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在各项均为正数的等比数列{an}中，若log2a2+log2a8＝1，则a3•a7＝ ．
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高二下学期数学《》真题及答案
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设{an}是由正数组成的等比数列且a5·a6＝81则log3a1＋log3a2＋＋log3a10的值
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已知等比数列{an}的各项均为正数2a2﹣5a1=3a3a7=9a421求数列{an}的通项公式2设
等比数列{an}的各项均为正数且2a1+3a2=1a32=9a2a6Ⅰ求数列{an}的通项公式Ⅱ设b
若等比数列{an}的各项均为正数且a10a11+a9a12=486则log3a1+log3a2++l
在各项均为正数的等比数列{an}中已知a2＝2a1＋3且3a2a45a3成等差数列.1求数列{an}
在各项均为正数的等比数列{an}中a1=2且2a1a33a2成等差数列.Ⅰ求等比数列{an}的通项公
在等差数列中我们有结论若abc成等差数列则2a2b2c成等比数列成立类比上述结论则有下列结论成立的
若正数a，b，c成等比数列，则log
m
a，log
m
b，log
m
c成等差数列
若正数a，b，c成等比数列，则2
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，2
b
，2
c
成等差数列
若正数a，b，c成等比数列，则log
m
a，log
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b，log
m
c成等比数列
若正数a，b，c成等比数列，则2
a
，2
b
，2
c
成等比数列
在正项等比数列{an}中若a3a11=16则log2a2+log2a12=.
等比数列{an}的各项均为正数且2a1＋3a2＝1a＝9a2a6.Ⅰ求数列{an}的通项公式Ⅱ设bn
已知各项均为正数的等比数列{an}的前n项和为Sn若S4=3S2a3=2则a7.
在各项均为正数的等比数列{an}中若a1≥1a2≤2a3≥3则a4的取值范围是.
在正项等比数列{an}中若a3a11=16则log2a2+log2a12=.
下列命题中正确的是
若a，b，c是等差数列，则log2a，log2b，log2c是等比数列
若a，b，c是等比数列，则log2a，log2b，log2c是等差数列
若a，b，c是等差数列，则2a，2b，2c是等比数列
若a，b，c是等比数列，则2a，2b，2c是等差数列
等比数列{an}的各项均为正数且2a1+3a2=1a32=9a2a6Ⅰ求数列{an}的通项公式Ⅱ设b
互不相等的三个正数x1x2x3成等比数列且点P1logax1logby1P2logax2logby2
等差数列，但不成等比数列
等比数列而非等差数列
等比数列，也可能成等差数列
既不是等比数列，又不是等差数列
在各项均为正数的等比数列{an}中若a2=1a5=a3+2a1则a3=
等比数列{an}的各项均为正数且a5a6+a4a7=18则log3a1+log3a2+log3a10
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2+log
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等比数列{an}的各项均为正数且a4•a7=3则log3a1+log3a2++log3a10=.
已知等比数列{an}的各项均为正数a2＝8a3＋a4＝48.1求数列{an}的通项公式2设bn＝lo
各项为正数的等比数列{an}a4•a7=8则log2a1+log2a2++log2a10=
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如图甲所示ABCD分别是竖直面内半径为R4R的圆弧轨道光滑AB圆弧与粗糙平面BC在B点平滑连接圆弧CD的圆心与C在同一高度．一个质量为m的物块从A点上方高度为R的P点由静止释放刚好从A进入圆弧轨道物块与BC平面间的动摩擦因数随物块从B点向右滑行的距离d之间的关系如图乙所示物块从C点抛出后落在CD弧上的某点E且E点与CD弧对应圆心O的连线跟水平方向的夹角为53°重力加速度为gsin53°＝0.8cs53°＝0.6求 1物块运动到圆弧B点时对轨道的压力大小 2水平面BC部分的长度
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Havingtroubledistinguishingonefurrypandafromanother?Afacialrecognitionappwillmakeiteasyforyou.TheappisdevelopedbytheChinaConservationandResearchCenterforGiantPandasalongwithresearchersinSingaporeNanyangTechnologicalUniversityandSichuanNormalUniversity. Theimageanalysisresearchbeganin2017.Adatabasenowcontainsabout120000imagesand10000videoclipsofgiantpandas.Closeto10000pandapictureshavebeenanalyzedandmarked.Usingthedatabaseresearchersareabletocarryoutautomaticfacialrecognitiononpandafacestotelloneanimalfromanotherthecentersaid. It'snotjustagimmick噱头fortouriststhough.PandaresearchershopealgorithmsandAItechnologywillhelpthemanalyzedataonpandasbothincaptivity圈养andthewild.Theappanddatabasewillhelpusgathermorepreciseandwell﹣roundeddataonthepopulationdistributionagesgenderratiobirthanddeathsofwildpandaswholiveindeepmountainsandarehardtotracksaidChenPengaresearcherwiththebasewhoco﹣authoredapaperonGiantPandaFaceRecognitionUsingSmallDatabase.ItwilldefinitelyhelpusimproveefficiencyandeffectivenessinconservationandmanagementoftheanimalsChensaid. Chinahascarriedoutfourscientificfieldresearchprojectofgiantpandasinthewild.Thegiantpandawasscientificallydiscovered150yearsagoandnamedinthecityofYa'anSichuan.Itremainsoneoftheworld'smostendangeredspecies.Thenumberofcaptivepandaswas548globallyasofNovemberlastyear.Fewerthan2000pandasliveinthewildmostlyintheprovincesofSichuanandShaanxi. 1Howmanypandashavebeencarefullyrecordedaccordingtothepassage? A.120000. B.10000. C.2000. D.548. 2Withthehelpoftheappanddatabasewecangetinformationaboutpandasexpect. A.thepopulation B.theirages C.thebirthanddeathsofwildpandas D.theweight 3Whatcanwelearnfromthepassage? A.TheAItechnologymakesnodifferencetotheprotectionofpandas. B.Atpresenttheappisnotpracticalfortourists. C.Morepandasliveinthewildratherthanincaptivity. D.Pandasarethemostendangeredspeciesaroundtheworld.
Notre﹣DamedeParisacathedralchurchinParisisthemostfamousoftheGothiccathedralsoftheMiddleAges.FortheFrenchitrepresentssomethingimmortalever﹣presentandunchanginglikeamountain.BuiltoveralmosttwocenturiestheNotre﹣DameisasPresidentEmmanuelMacronsaidwheretheFrenchlivedalltheirgreatmoments.SoldiersprayedherebeforeleavingfortheCrusadesNapoleonBonapartewascrownedhereitsurvivedtheFrenchRevolutiontwoWorldWarsandtheNazioccupation.Itiswheremenbendtheirkneestoprofessloveandthousandsoftouriststakephotoseveryday. Afirewhosecausewasnotidentifiedyetengulfed吞没onApril15ththecathedral'supperstructure.Morethan400firefighterstookpartinthe15﹣hourbattletocontroltheblaze火苗thattriggeredsorrowovertheglobe.Theextentofthedamageisstillunknownbutthefiredestroyedmuchofthegothiccathedral'swood﹣timberedroofandspire塔尖.ThecathedralwillcertainlyberestoredtheFrenchgovernmentpromisesbutthesightofflamesbringingdownthespiremovedtheworldinamannerfarexceedingitsreligioussignificance. FrenchCultureMinisterFranckRiesteronThursdaysaidthegovernmentwoulddrawalltheconsequencesfromthehugeflamesthatdestroyedthecenturies﹣oldNotreDameCathedraladdingmeasurestoprotectthenationalheritagewereonthetable.StafffromthefiredepartmentthecultureministryandthecitytownhallrushedtotheCathedralwhenthefirestartedtoprotectthemainartworksthatwereinside.TheartworkswhichincluderelicssuchastheChrist'scrownofthornsandFrenchkingSaint﹣Louis's13thcenturytunicwerefirstmovedtothecitytownhallandwillnowbetransferredtothenearbyLouvreMuseum.theministertoldLeParisiannewspaperinaninterviewwithoutgivingdetailsonthepossiblemeasures. 1WhatcanwelearnabouttheNotre﹣DamedeParis? A.Itisthemostwell﹣knowncathedral. B.MostoftheFrenchthinklittleofit. C.ItwasbuiltbyNapoleonBonaparte. D.It'sstillinexistenceaftertwoWorldWars. 2TheunderlinedwordtriggeredinParagraph2canbereplacedby. A.destroyed. B.avoided. C.caused. D.prevented 3WhatistrueabouttheCathedralintheaccident? A.Onlythespirewasbroughtdownbytheflames. B.Itwascompletelyburntinthefire. C.Thegildedcrownofthornsinitwasgoneforever. D.ThecauseoftheaccidenttotheCathedralwasstillunknown. 4AccordingtoFranckRiesterwhathasalreadydonebythegovernment? A.Rebuildthecathedral. B.Rescuetheartworksinsidethecathedral. C.TransfertherelicstothenearbyLouvreMuseum. D.Releasethecauseofthefiretothepublic.
AsInternetusersbecomemoredependentontheInternettostoreinformationarepeoplerememberingless?Ifyouknowyourcomputerwillsaveinformationwhystoreitinyourownpersonalmemoryyourbrain?ExpertsarewonderingiftheInternetischangingwhatwerememberandhow. InarecentstudyProfessorBetsySparrowconductedsomeexperiments.SheandherresearchteamwantedtoknowhowtheInternetischangingmemory.Inthefirstexperimenttheygavepeople40unimportantfactstotypeintoacomputer.Thefirstgroupofpeopleunderstoodthatthecomputerwouldsavetheinformation.Thesecondgroupunderstoodthatthecomputerwouldnotsaveit.Laterthesecondgrouprememberedtheinformationbetter.Peopleinthefirstgroupknewtheycouldfindtheinformationagainsotheydidnottrytorememberit. Inanotherexperimenttheresearchersgavepeoplefactstorememberandtoldthemwheretofindtheinformationonthecomputer.Theinformationwasinaspecificcomputerfolder文件夹.Surprisinglypeoplelaterrememberedthefolderlocation位置betterthanthefacts.WhenpeopleusetheInternettheydonotremembertheinformation.Rathertheyrememberhowtofindit.Thisiscalledtransactivememory交互记忆. AccordingtoSparrowwearenotbecomingpeoplewithpoormemoriesasaresultoftheInternet.Insteadcomputerusersaredevelopingstrongertransactivememoriesthatispeoplearelearninghowtoorganizehugequantitiesofinformationsothattheyareabletoaccessitatalaterdate.Thisdoesn'tmeanwearebecomingeithermoreorlessintelligentbutthereisnodoubtthatthewayweusememoryischanging. 1Thepassagebeginswithtwoquestionsto. A.introducethemaintopic B.showtheauthor'sattitude C.describehowtousetheInternet D.explainhowtostoreinformation 2Whatcanwelearnaboutthefirstexperiment? A.TheSparrow'steamtypedtheinformationintoacomputer. B.Thetwogroupsrememberedtheinformationequallywell. C.Thefirstgroupdidnottrytoremembertheinformation. D.Thesecondgroupdidnotunderstandtheinformation. 3Intransactivememorypeople. A.keeptheinformationinmind B.changethequantityofinformation C.organizeinformationlikeacomputer D.rememberhowtofindtheinformation 4WhatistheeffectoftheInternetaccordingtoSparrow'sresearch? A.Weareusingmemorydifferently. B.Wearebecomingmoreintelligent. C.Wehavepoorermemoriesthanbefore. D.Weneedabetterwaytoaccessinformation.
OneSaturdayafternoonmymotherwasdrivinghome.Onthehalfwayafter1hercreditcardtobuysomethingatthestorenearthegasstationsheputherwalletonthetopofhercarjustforamomentto2myphonecall.Andthenobviouslyshe3anddroveoff.Whenarrivinghomesherealizedthatandthoughtthatthe4ofgettingitagainwassmall. Shewasso5surprisedwhenshefounda6onherdoorfromapersonwhosaidheandhisfriendfoundherwalletafewhoursearlier.PatrickandCatherinesawthewalletinthemiddleoftheroadafew7fromthegasstation.Theystoppedtheircarto8.Itwasfilledwithallthethingsonenaturallykeptinawalletincludingsome9andothercashhowevernophonenumber.10thistheymanagedtogetan11frommymother'sdrivinglicenceandwithouthesitationtheydecidedtodrivetoourhometo12it. Wheymymotherwenttogetherwallet.shewasso13andgrateful.She14togivethemsomemoneyasan15ofgratitudebuttheyrefusedsayingthattheywerejustgladto16mymotherhelp. Theywerenaturally17andtheyhadfirm18intheGoldenRuleaswell.Theydrovetoourhomebecausetheyrealizedtheunpleasantandupsetexperiencetheexperiencethelossofawalletandallitscontentscould19.Ithinktheywerereally20andhelpful. 1A.pullingout B.standingfor C.payingfor D.sortingout 2A.make B.answer C.hear D.send 3A.sank B.explored C.forgot D.inspected 4A.amount B.expectation C.thought D.chance 5A.curiously B.joyfully C.willingly D.strangely 6A.sign B.signal C.note D.postcard 7A.seconds B.hours C.squares D.blocks 8A.pickitup B.lookitup C.takeitout D.putitout 9A.pictures B.envelopes C.bills D.medals 10A.Insteadof B.Becauseof C.Despite D.Without 11A.number B.photograph C.address D.distance 12A.get B.check C.exchange D.return 13A.hopeless B.relieved C.fortunate D.warm﹣hearted 14A.planned B.advised C.demanded D.instructed 15A.feeling B.mood C.present D.expression 16A.offer B.share C.trust D.seek 17A.honest B.selfish C.logical D.creative 18A.courage B.faith C.support D.devotion 19A.remove B.deserve C.value D.cause 20A.humorous B.independent C.polite D.considerate
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小麦的穿梭育种是将一个地区的品种与其他地区的品种进行杂交然后通过在两个地区间不断地反复交替穿梭种植选择鉴定最终选育出多种优良性状的小麦新品种．下列关于小麦穿梭育种的叙述错误的是
松果体可通过褪黑素的周期性分泌向中枢神经系统发放“时间信号”从而影响机体时间生物效应如睡眠与觉醒．如图表示光暗信号通过视网膜→神经中枢→松果体途径调控人体睡眠过程的示意图．请回答 1当神经末梢有神经冲动传来时突触前膜内的受到刺激释放去甲肾上腺素引起松果体细胞分泌褪黑素．褪黑素分泌的调节方式是与褪黑素调节睡眠相比该调节方式的反应速度． 2下丘脑除与生物节律的控制有关外还有等神经中枢． 3研究发现褪黑素还能促进BT淋巴细胞的增殖．B细胞在填场所中成熟并可增殖分化成．由此判断等病症患者不适合使用外源褪黑索．
如图所示在竖直的墙壁正前方有一个点D点D到墙壁的水平距离是d从D点以不同的初速度水平抛出一个小球视为质点每次都可以击中墙壁如果要想使小球以最小的动能击中墙壁则平抛小球的初速度是
假定英语课上老师要求同桌之间交换修改作文请你修改你同桌写的以下作文.文中共有10处语言错误每句中最多有两处错误.每处错误仅涉及一个单词的增加删除或修改. 增加在缺词处加一个漏字符号^并在其下面写出该加的词. 删除把多余的词用斜线\划掉. 修改在错的词下面画一横线并在该词下面写出修改后的词. 注意1.每处错误及其修改均仅限一词 2.只允许修改10处多者从第11处起不计分. DuringtheNationalDayholidayIpaidavisitmygrandmainthecountryside.IthasbeenalmosttwoyearssinceIlastsawher.Inmymemorymygrandmawasahardworkingbutstrongwomanfullofenergy.Whenevershesawmeshealwayshuggedmedeep.ButwhenIgaveherahugthistimeIfoundthatshewasmuchshortandthinnerthanbefore.Herbackwasbecomebentandherhairsturnedwhite.Butluckilyshewasstillhealth.Shecouldlaughlikeachild.Tomyhappyshecouldcooksomedeliciousfoodforme.Ilovemygrandma.Iknowhewillalwaysbetherehelpingmeandlovingme.
TheHarbinInternationalIceandSnowSculpture雕塑品FestivalisHarbin'smaintouristhighlighteveryyear.It1becometheworld'sbiggestwinterfestivalsofar.2makestheHarbinfestivalspecialrethescaleandsizeofthesculpturesandthebeautifullighting.ItisbiggerthantheonesinJapanNorwayandCanada. AtfirstmainlytheChinesetookpartbutnowitisaninternationalfestivaland3compete.Asthefestivalgrowsthesizeofthesnowsculpturesandicearchitectureexhibitskeeps4increase.Theworkofmakingtheseexhibitsis5astonishandtheirsizeandbeautyareamazing. Thefestivalis6officialheldfromtheendofDecemberthroughFebruary.Openingdateskeepchangingandclosingdatespartlydepend7theweather.Morethan1000icesculpturesareonshowsuchasicelanternsmagicalfiguresandanimalsthat8lovebychildren.Itismostlyaniceworld9aimatkids.Thereareinterestingactivitieskidsmayenjoylikeiceskating.IfyouareplanningaHarbintourpleaseattend10wonderfulfestival.
假如你是李华美国交换生John刚来你校就读他朋友少感觉非常孤独希望得到同学们的帮助.你听说后决定用英语给他写一封信. 内容要点如下1.表示关心 2.就如何交朋友给出自己的建议 3.邀请John来家里做客. 注意1.词数100左右.首尾已给出但不计入总词数 2.可以适当增加细节以使行文连贯. DearJohn I'mLiHuaoneofyourschoolmates.I'msorrytohearthatyouarelonelyinthisnewschool. Yours LiHua
小鼠的弯曲尾B对正常尾b显性．让正常尾雌鼠与弯曲尾雄鼠杂交子一代弯曲尾♀正常尾♂＝11．遗传学家将一个本身不控制具体性状的DNA片段“M”导入到子一代弯曲尾雌鼠的体细胞中通过DNA重组和克隆技术获得一只转基因正常尾小鼠已知“M”和B基因同时存在时表现为正常尾b基因的表达不受“M”的影响小鼠的受精卵中Bb基因都不存在时将导致胚胎致死．请回答 1写出正常尾雌鼠与弯曲尾雄鼠杂交实验的遗传图解．． 2遗传学家认为“M”插入到小鼠染色体上的位置有4种可能如图．为确定“M”具体的插入位置进行了相应的杂交实验．不考虑交叉互换 实验方案让该转基因正常尾小鼠与非转基因正常尾雄鼠杂交统计子代的表现型种类及比例．结果与结论 ①若子代则“M”的插入位置属于第1种可能性 ②若子代则“M”的插入位置属于第2种可能性 ③若子代则“M”的插入位置属于第3种可能性 ④若子代则“M”的插入位置属于第4种可能性．
“碰撞中的动量守恒”实验装置如图所示让质量为m1的小球A从斜面上某处自由滚下与静止在支柱上质量为m2的小球B发生对心碰撞两球的半径均为r对心碰撞瞬间两球心的连线保持在水平方向上． 1本实验设计思想的巧妙之处是用的测量替代的测量 2实验中两球的质量关系一定满足 3碰撞中如果动量守恒则满足
Cloningisanapproachto1makeanexactcopyofanotheranimalorplantwhichinourdailylifehappensquiteoften.Ithastwomajoruses.2isthatgardenerstakecuttingsfromgrowingplantstomakenewones.Theotheristhatitis3valueformedicalresearchonanimals.Theprocessofcloningisadifficulttask4undertake. ThefirstsuccessfulcloneDollythesheep5arouseworldwide6curiousandconcernbecauseofitsscientificandethicalimplications影响.ShewasthefirstmammaltobeclonedfromadultDNA7takefromanadultcell.Dolly'sappearanceraisedastormof8objectandhadagreateffect9themediaandpublicimagination.Differentpeoplehavedifferentopinionsonit.Howeverscientistsstillwonder10cloningwillhelporharmusandwhereitisleadingus.
ElephantReserve CountryThailand Thisisaworkingvacationatawildlifecentre.Anyonecanbecomeavolunteerifhe/sheagreestohelptheelephantkeeperswithtasks. Dailytasks Gathertheelephantsat630am.Takethemtolookforfoodintheforest.Cleantheenclosure围场.Swimwiththeelephantsinthelakeintheafternoon.Ifvolunteerswanttorelaxafterworktheycanwatchsatellitetelevision. Howthisvacationhelps Iftheseelephantshadn'tbeenrescuedtheywouldstillbelivingonthestreetsofBangkok.Theruralenvironmentismuchbetterforthemthantheurbanenvironmentwherethereislotsofpollution. YourComment Iloveworkingwiththesehugegentleanimals. Gorillasafari观赏野兽的旅行 CountriesKenyaRwandaandUganda Departures出发2﹣3departurespermonthfromAug.toDec. Extraspermit￡220 Ifyou'reluckyyou'llseelionselephantsandrhinosduringthissafari.Thehighlight最好的部分ofthetripistheopportunitytoseegorillasinthemountainforests.Howeveryoumustbeingoodhealth﹣ifagorillacaughtacolditwouldbeextremelyharmfultoitswholefamily. Howthisvacationhelps Thereareonlyabout600gorillasleftintheworldashumanactivityhasreducedtheareawheretheycanlive.Whenyoubuyapermitthiswillpayfortheprotectionofthenationalpark. Yourcomment I'llsurelygobackassoonasIhaveenoughmoney! Polarbearwatching Area&CountryArcticCanada DeparturessixtytripsbetweenOct.1﹣Nov.19. EveryOctoberandNovembergroupsofpolarbearsgatherinHudsonBay.Astheyarenormallylonelycreaturesthisisunusual.Thebearswaitfortheoceantofreezesothattheycanhuntforsealssothisistheperfectopportunitytoseethem.Extraactivitiesincludedogsledding狗拉雪橇andanighttriptoseetheNorthernLights. Howthisvacationhelps IftheArcticicecapmeltsduetoglobalwarmingpolarbearswillbeindanger.Wegiveashareofourprofits利益tothecharitythatprotectspolarbears. Yourcomment Theseterriblebearsgetalltheliquidtheyneedfromtheirfood. 1Whatwillelephantvolunteersdo? A.Sweeptheenclosureofelephants. B.Takefoodforelephantsat630am. C.Watchsatellitetelevisiononelephants. D.Washelephantsinthelakeintheafternoon. 2WhatdoweknowabouttheGorillasafari? A.YoucanfindgorillasinKenyaandCanada. B.Youwillgetacoldinthemountainforests. C.Visitorsneedtopay﹩220toseegorillas. D.Thereareabout10tripstovisitgorillas. 3What'stheaimoftheseactivities? A.Tohelpbuildmorenationalparks. B.Tohelpprotectthewildanimals. C.Tohelpdealwiththepollutionincities. D.Tohelpsolvetheproblemofglobalwarming.
Self﹣esteem自尊playsaroleinalmosteverythingyoudo.1Theycanhavebetterrelationshipswithpeers同龄人andadultsfeelhappierfinditeasiertodealwithmistakesdisappointmentsandfailuresandaremorelikelytostickwithsomethinguntiltheysucceed. Ifyouwanttoimproveyourself﹣esteemherearesomeusefultips. ★Trytostophavingnegativethoughtsaboutyourself.Ifyou'reusedtofocusingonyourshortcomingsstartthinkingaboutpositiveaspectsofyourself.2 ★Viewmistakesaslearningopportunities.Acceptthatyouwillmakemistakesbecauseeveryonedoes. 3Remindyourselfthataperson'stalentsareconstantlydevelopingandeveryonedoeswellindifferentthings. ★4Ifyourealizethatyou'reunhappywithsomethingthatyoucanchangethenstarttoday.Ifit'ssomethingyoucan'tchangelikeyourheightthenstarttoworktowardlovingyourselfthewayyouare. ★Makeacontribution.Helpaclassmatewho'shavingtroubleoffertocleanupyourneighborhoodorvolunteeryourtimeinsomeotherway.5 ★Havefun.Enjoyspendingtimewiththepeopleyoucareaboutanddoingthethingsyoulove.Relaxandhaveagoodtime﹣andavoidputtingyourlifeonhold. Ittakessomeworktodevelopgoodself﹣esteembutonceyoudoit'saskillyou'llhaveforlife. A.Mistakesarepartoflearning. B.Recognizewhatyoucanchangeandwhatyoucan't. C.Lowself﹣esteemisanegativeevaluation评价ofoneself. D.Thatyourhelpisvaluedcandowonderstoimproveself﹣esteem. E.Eachdaywritedownthreethingsaboutyourselfthatmakeyouhappy. F.Peoplewithhighself﹣esteemdobetterinschoolandfinditeasiertomakefriends. G.Experienceisthegreatthingthatenablesyoutorecognizeamistakewhenyoumakeitagain.
如图所示是一列简谐横波在t0＝0时刻的波形此时刻质点P的速度为v经过t＝0.2s后它的速度大小方向第一次与v相同再经过△t＝1.0s后它的速度大小方向第二次与v相同则这列简谐横波的传播方向是向选填“左”或“右”传播波速是若某时刻N质点到达波谷处则Q质点一定到达选填“波峰”“波谷”或“平衡位置”处从图示位置开始计时在t＝3s时质点M偏离平衡位置的位移为运动方向是选填“向上”“向下”“向左”或“向右”．
如图所示质量为m带有半圆形轨道的小车静止在光滑的水平地面上其水平直径AB的长度为2R现将质量也为m的小球从距A点正上方为h的位置由静止释放然后由A点进入半圆形轨道后从B点冲出在空中上升的最大高度为h不计空气阻力则
为研究影响抗体分泌的因素用取自同一个体的细胞完成了以下实验“+”表示有“﹣”表示无．有关叙述错误的是
Itwasanotherfrustratingday.Icamehomefromschoolchangedmyclothesandgotreadyforwork.Iworkedatalocalrestaurantintown. Iwenttoworkfeelingdown.It'sthesamethingoverandoveragaindealingwithcustomerswhocomplainabouttheirfood﹣﹣﹣howthepieceofpiethattheyareservedistoobigortoosmall.Threeelderlyladieswalkedinandsatbythewindow.Iwasworkingsince500p.m.andwewerequitebusy.ButtheseelderlywomenwerewatchingmeasIwasworkingreallyhardtomakesureeverytablewascleanandreadyforthenextcustomers. WhentheywerefinishedwiththeirmealsItooktheirplatesbacktothekitchen.TheytalkedtomeforawhileaboutschoolhowIwasdoingwhichgradeIwasinandwhatIplannedtodointhefuture. AstheywereleavingtheywalkedpastmeandoneofthemsaidtomeinaconfidentandgentlevoiceYouaregoingplaces.TheylefttherestaurantandIwasprettymuchinawe.Ihadtearsinmyeyesbecausetheygavemeareasontobelieveinmyself.Theypickedmyspiritupfrombeingdownandgavemeareasontokeeponworkinghardandtogiveitmyall. 1Fromthepassagewelearnthattheauthor. A.hadaparttimejob B.workedintherestaurantallday C.lovedhisjobatfirst D.didverywellinhislessons 2TheunderlinedsentenceYouaregoingplaces.inthetextprobablymeans. A.You'regoingonatrip. B.Youshouldgotoabetterplace. C.You'llbesuccessful D.You'reintherightplace. 3Theauthorfeltsadbecause. A.hedidn'twanttoworkthere B.itwasdifficulttomakethecustomershappy C.hehadtodothesamethingagainandagain D.theworkwastoohardforateenager 4Thepassagetellsusthat. A.encouragementcanbeimportantforyoursuccess B.everyoneshouldtreatelderpeoplegently C.peopledoingallkindsofjobsshouldberespected D.studentsshouldmakemoneytosupportthemselves
Smilingisagreatwaytomakeyourselfstandoutwhilehelpingyourbodytofunctionbetter.Itisjustonefunwaytolivelongerreadabouttheothersandtryasmanyasyoucan.1 1.Smilingmakesusattractive 2Thereisanattractionfactor.Wewanttoknowasmilingpersonandfigureoutwhatissogood.Frownsandsorrowsallpushpeopleaway﹣﹣butasmiledrawsthemin.Whensomeoneissmilingtheylightenuptheroomchangethemoodsofothersandmakethingshappier.Smilealotandyouwilldrawpeopletoyou. 2.3 Stresscanreallyshowupinourfaceswhilesmilinghelpstopreventusfromlookingtiredworndownandoverwhelmed.Whenyouarestresseditisofgreatsignificancetotaketimetoputonasmilewhichcantrickthebodyintohelpingyouchangeyourmood.Thestressshouldbereducedandyou'llbebetterabletotakeaction. 3.SmilingLowersYourBloodPressure Whenyousmilethereisameasurablereductioninyourbloodpressure.4 Sitforafewminutestakeareading.Thensmileforaminuteandtakeanotherreadingwhilestillsmiling.Doyounoticeadifference? 4.SmilingMakesYouSeemSuccessful Smilingpeopleappearmoreconfidentaremorelikelytobepromotedandmorelikelytobeapproached.5 Nexttimeyouarefeelingdowntryputtingonasmile.There'sagoodchanceyourmoodwillchangeforthebetter. A.Themusclesweusetosmileliftthefacemakingapersonappearyounger. B.SmilingRelievesStress C.Herearesomereasonstokeepsmilinginyourdailylife. D.Giveitatryifyouhaveabloodpressuremonitorathome. E.Putonasmileatmeetingsandappointmentsandpeoplewillreacttoyoudifferently. F.WhenwesmileourbodyissendingtherestofusamessagethatLifeisGood! G.Wearedrawntopeoplewhosmile.
埃博拉病毒EBO呈纤维状EBO衣壳外有包膜包膜上有5种蛋白棘突VP系列蛋白和GP蛋白其中GP蛋白最为关键能被宿主细胞强烈识别．请回答下列问题 1要获得编码GP蛋白抗原的基因疫苗首先要提取出病原体的RNA并利用RNA经合成DNA构建cDNA文库．cDNA文库中的基因选填“可以”“不可以”“部分”进行物种间的基因交流． 2为了从牛分泌的乳汁中提取GP蛋白需将GP蛋白基因通过方法导入牛受精卵中．在基因导入牛受体细胞前基因的首段必须含有使其仅能在牛的乳腺细胞中特异性表达的驱动转录过程．转基因牛是否培育成功可以通过技术从分子水平上进行检测． 3以GP蛋白作为疫苗比利用毒性减弱的埃博拉病毒作疫苗更安全其原因是． 4科研人员利用经EBO免疫后小鼠的与小鼠的骨髓瘤细胞进行融合以形成杂交瘤细胞培养后可以获得纯净的单一品种抗体其特点是可以用此抗体与药物制成“生物导弹”抗击EBO．
下列说法正确的是
如图所示质量mA＝2kg的木板A被锁定在倾角为30°的光滑斜面的顶端质量为mB＝1kg的可视为质点的物块B恰能在木板A上匀速下滑．现让物块B以v0＝7.5m/s的初速度从木板的上端下滑同时解除对木板A的锁定．g取10m/s2斜面足够长．求 1要使物块B不从木板A上滑落下来则木板A的长度至少为多少 2在物块B不从木板A上滑落的前提下系统损失的机械能最多是多少
如图所示是半径为R的圆柱形玻璃砖的横截面一束单色光斜射到玻璃砖圆弧面上的C点入射角α＝60°折射光线照射到圆弧面的D点再次折射后出射光线沿DE方向．已知光线经玻璃砖两次折射后的偏向角θ＝60°光在真空中的传播速度为c则玻璃对单色光的折射率n＝光线在玻璃砖中从C传播到D所用的时间t＝．
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