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若->-2,则x 6
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若函数y=fx的导函数f'x=6x2+5则fx可以是
3x
2
+5x
2x
2
+5x+6
2xa+5x
6x
2
+5x+6
下列变形正确的是
若x
2
=y
2
,则x=y
若
,则x=y
若x(x﹣2)=5(2﹣x),则x=﹣5
若(m+n)x=(m+n)y,则x=y
下列等式变形错误的是
若
a+3=b-1,则a+9=3b-3
若2x-6=4y-2,则x-3=2y-1
若x
2
-5=y
2
+1,则x
2
-y
2
=6
若
,则2x=3y
若x2+4x﹣4=0则3x﹣22﹣6x+1x﹣1的值为
﹣6
6
18
30
若x1x2是x2-6x-7=0的根则x1·x2=
-7
7
6
-6
在下列命题①若a2=b2则a=b②若x>y则2﹣3x>2﹣3y③若x2=2则x=±④若x3=8则x=
已知fx=ax4+bcosx+7x-2.若f′2017=6则f′-2017为
-6
-8
6
8
下列变形中正确的是
若x
2
=6x,则x=6
若﹣3x=1,则x=﹣3
若x=y,则
若
,则x=y
若A.=x2-3x-6B.=2x2-4x+6则3A-2B=_______
下列变形正确的是
若x
2
=y
2
,则x=y
若
,则x=y
若x(x﹣2)=5(2﹣x),则x=﹣5
若(m+n)x=(m+n)y,则x=y
下列说法错误的是
命题“若x
2
-5x+6=0,则x=2”的逆否命题是“若x≠2,则x
2
-5x+6≠0”
若命题p:存在x
0
∈R.,x
+x
0
+1<0,则綈p:对任意x∈R.,x
2
+x+1≥0
若x,y∈R.,则“x=y”是“xy≥
2
”的充要条件
已知命题p和q,若“p或q”为假命题,则命题p与q中必一真一假
1若a+b=8则-a+b=_______2若a+b=8则-a-b=_______3若x2+y2=1则
若函数y=fx的导函数f′x=6x2+5则fx可以是______.
3x
3
+5x
2x
2
+5x+6
2x
3
+5x
6x
3
+5x+6
下列命题中错误的是________.①命题若x2-5x+6=0则x=2的逆否命题是若x≠2则x2-5
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Areyouahappypersonoranunhappyperson? Ifyou'reanunhappypersonpleaserememberthathappinessisachoice.1Whatyouneedtodoistomakesomechanges. Unhappypeoplearemorelikelytobelievethatlifeishard.Theyseethemselvesasvictimsoflifewhensomethingbadhappenstothem.Yesasisknowntoalllifecanbehard.2 Unhappypeoplearemorelikelytobelievethatmostpeoplecan'tbetrusted.Theydon'tthinkstrangerscanbetrusted.Unfortunatelythisthoughtslowlystartstopreventthemfrommeetingnewpeople.3Inthiswayyoucanmakemorefriendswhocanincreaseyourhappiness. Unhappypeoplelikecomparingthemselveswithothersandfeeljealous.4Thisiswrong.Insteadyoushouldgetinspiredandtrytoachievemore.Learntobelieveinunlimitedpossibilities.Don'tgetupsetandthinkthatsomebody'slucklimitsyourpossibleoutcomeinlife. Unhappypeopleconsidertheirfuturewithworryandfear.5Unhappypeoplefilltheheadspacewithworryandfear.Howcanyoubehappyifyouarealwaysinworryorfear?Whenfearorworrycrossesyourmindaskyourselfifthereisanactionyoucantaketopreventyourfearorworryfromhappening.Ifthereisn'tjustlayitdownbecauseworryorfeardoesyounogoodatall. Everyonewillprobablyswiminnegativewatersonceinawhilebutwhatmattersishowlongyoustaythere.Followthewaysmentionedaboveandthenyouwillbemuchhappier. A.Butyoushouldhaveapositiveattitudetowardslifeinsteadofcomplainingallthetime. B.Thereisonlysomuchspacebetweenyourears. C.Unhappinessisalsoachoice. D.Youcanchoosetobehappy. E.Youshouldtrytobekindtoothersinordertomakemorefriends. F.Insteadyoushouldbelieveinthegoodinpeopleandstayopenandfriendlytowardspeopleyoumeet. G.Theybelievethatsomeoneelse'sluckisstolenfromtheirown.
AnAmericanphotographerismakingcopiesofgreatartworkavailableforblindpeopleandthosewithverypooreyesight.Atleast285millionpeopleworldwideareeitherblindorconsideredvisuallyimpaired有缺陷的.Theyareunabletoseeorenjoyvisualfineart. RomeoEdmeadlosthiseyesightwhenhewasonlytwoyearsold.Butthathasnotstoppedhimfromlivinglifetothefullest.Hewenttocollageandstudiedjournalism.HenowlivesinNewYork.Hedependsheavilyonhisothersenses.ButhecannotexperiencethegreatworksofartintheCity.Heremembersavisittoanartcollectionwithhisgrandmother.WewenttothismuseumandIjustwanderedoffsomewhereandIstartedtouchingsomethingandallofasuddenalarmwentoff.Andaguardcamerunningoverandmygrandmotherwasallashamed.Romeoisnowabletousehisfingerstofeelartpaintings.Hecangetanideaoftheappearancebyfollowingthemarkings. JohnOlsononceworkedasaphotographerforLIFEmagazine.HedevelopedaprintingprocesstomaketheartofDaVinciandVanGoghtouchableforvisually﹣impairedpeople.Ibegantorealizehowimportantimages影像havebeentomeandwhattheyhaveallowedmetodo.Anditcausedmetowonderwhatitwasfortheblindnothavingaccesstoimages.Olson'scompanyiscalled3DPhotoworks.Itproducescopiesofartworkinthreedimensions﹣heightwidthanddepth.Thewholeprocesscantakeuptofourweeks. Thankstonewtechnology3Dartmaysoonhanginartmuseumsallovertheworld.Itgivesthevisually﹣impairedthechancetoexperiencethebeautyofvisualart. 1WhatmotivatedJohnOlsontomake3Dartforblindpeople? A.Thebenefitofhiscompany. B.RomeoEdmead'ssufferings. C.Hisappreciationtoblindpeople. D.Theimportanceofimagestopeople. 2Whatdoestheunderlinedworddimensionmean? A.aperiodoftime B.thesizeofasituation C.ameasurementinspace D.thewayofdoingthings 3HowwillJohnOlson'sworkinfluencethelifeofblindpeople? A.Theyareabletolivetheirlifetothefullest. B.Theycanhavethechancetofeelthebeautyofvisualart. C.Theydon'tneedtodependheavilyontheirothersenses. D.Theyhavefreeaccesstomuseumswithoutanydifficulty. 4Whatcanwelearnfromthepassage? A.Ittakesamonthorsotoproducea3Dartwork. B.3Dartisproducedbasedonheightanddepth. C.3Dartisdisplayedinartmuseumsallovertheworld. D.JohnOlsonisrichforwhathehasdonefortheblind.
DearMary IreceiveyourE﹣mailjustnow.Don'tworryaboutme.I'mgettingonwellmyresearchworkinthelab.ButtomygreatsurpriseyousayyouwillgiveuplearningEnglish.Thereasonisthatbecauseyouhavenotdonewellinitrecentlyandyouhavelostinterests.I'mafraidIcan'tagreeonyou.IknowitisdifficulttolearnEnglishbutEnglishiswideusedintheworldtoday.Itwillbeimportanttoolinourfuturework.Besideitisbecomingmoreandmoreimportantinyourdailylife.Ifyoustudyhardyouwillsucceed.Dorememberwherethereisawillthereisaway.I'mlookingforwardtoheargoodnewsfromyou.
Ithoughtthepartywaswell组织andeverythingwentwell.
一根轻质弹簧受到拉力作用时其长度会变长且拉力大小与弹簧长度的增加量之比为定值.该比值反映了弹簧的力学性质由此定义该比值叫做弹簧的劲度系数用符号k来表示.如果将两根自然长度相同劲度系数不同粗细也不同的弹簧套在一起看做一根新弹簧设原弹簧A劲度系数为k1原弹簧B劲度系数为k2.现将弹簧AB的一端连接在一起将AB的另一端也连接在一起作为新弹簧记为C的两端C劲度系数为k3.关于k1k2k3的大小关系同学们做出了如下猜想 甲同学和电阻并联相似可能是=+ 乙同学和电阻串联相似可能是k3=k1+k2 丙同学可能是k3= 1为了验证猜想同学们设计了相应的实验.装置见图甲 2简要实验步骤如下请完成相应填空. ①将弹簧A悬挂在铁架台上用刻度尺测量弹簧A的自然长度L0 ②在弹簧A的下端挂上相同的钩码记下钩码的个数n每个钩码的质量m已知实验室所在位置的重力加速度大小g并用刻度尺测量弹簧的长度L1 ③由F=计算弹簧的弹力由x=L1﹣L0计算弹簧的伸长量由计算弹簧的劲度系数 ④改变重复实验步骤②③并求出弹簧A的劲度系数的平均值k1 ⑤仅将弹簧分别换为BC重复上述操作步骤求出弹簧BC的劲度系数的平均值k2k3.比较k1k2k3并得出结论. 3图乙是实验得到的图线由此可以判断同学的猜想正确. 4相类似地定义一个系统在受到拉力作用时拉力大小与系统长度增加量的比值叫做系统的等效劲度系数如图丙中的装置就是我们要研究的一个系统外力竖直向下作用于与动滑轮相连的挂钩上滑轮光滑且质量不计挂钩质量不计细线为不可伸长的轻绳弹簧的劲度系数为k且质量不计.若定义该系统的长度为系统静止时天花板到挂钩最低点间的距离则该系统的等效劲度系数为. A.4kB.2kC.0.50kD.0.25k
如图所示表面光滑的斜面固定在水平地面顶端安装有定滑轮小物块AB通过绕过定滑轮的绝缘轻绳连接轻绳平行于斜面空间有平行于斜面向下的匀强电场.开始时带正电的小物块A在斜面底端在外力作用下静止B离地面一定高度撤去外力B竖直向下运动.B不带电不计滑轮摩擦.则从A和B开始运动到B着地的过程中
2018年5月和12月我国分别成功地将探月工程的鹊桥号中继星和嫦娥四号登月探测器发射升空.鹊桥号中继星是世界首颗运行于地月拉格朗日L2点的通信卫星为在月球背面工作的嫦娥四号登月探测器提供地月间的中继通信.该L2点位于地球和月亮连线的延长线上如图所示鹊桥号在该点消耗很少燃料就可较长期地与月球同步绕地球做圆周运动.嫦娥四号登月探测器软着陆月球背面更深层次地探测月球地质资源等方面的信息.请根据上述信息和你所掌握的物理知识确定下列叙述中正确的是
用如图所示的装置探究物体的加速度与力质量的关系图中小车的质量用M表示钩码的质量用m表示.要顺利完成该实验在操作中 1平衡摩擦力的目的是 2使M远大于m目的是 3某次打出的某一条纸带ABCDE为相邻的5个计数点如图相邻计数点间还有四个点未标出所用交流电频率为50赫兹.利用图中给出的数据可求出小车的加速度a=m/s2.结果保留二位有效数字
Thisplacedoesn'tlook熟悉的atallwemustbelost.
如图质量为1.5kg的物体A静止在竖直的轻弹簧上质量为0.5kg的物体B由细线悬在天花板上B与A刚好接触但不挤压.现突然将细线剪断则剪断后瞬间AB间的作用力大小为g取10m/s2
Theywantedto设计amachinethatwasbothattractiveandpractical.
如图所示在竖直平面內有一粗糙斜面轨道AB与光滑圆弧轨道BC在B点平滑连接滑块经过B点时速度大小不变斜面轨道长L=2.5m斜面倾角θ=37°O点是圆弧轨道圆心OB竖直圆弧轨道半径R=1m圆心角θ=37°C点距水平地面的高度h=0.512m整个轨道是固定的.一质量m=1kg的滑块在A点由静止释放最终落到水平地面上.滑块可视为质点滑块与斜而轨道之间的动摩擦因数μ=0.25取g=10m/s2sin37°=0.6cos37°=0.8不计空气阻力求 1滑块经过圆弧轨道最低点B时对圆弧轨道的压力 2渭块离开C点后在空中运动的时间t.
JohnMichaelThomas14Florida WhenJohnMichaelThomasdecidedtohonorhisfriendandclassmateElizabethBuckleywhodiedfromcancerherememberedhowmuchshelovedpeacocks孔雀. Hewantedtobuildalifesizedpeacockfountain喷泉inElizabeth'sfavoriteparkinthecity.Hethoughtitcouldbeaplaceforpeopletorelaxandbeinspired. JohnMichaelraised﹩52000tobuildthefountain. BarrettEngland13Utah ThewheelsbegantoturnforBarrettEnglandwhenheheardaboutKarmaBikeShopaplacewhereyoungpeoplecanearnafreebikebyreadingandperformingcommunity社区service. BarrettvisitedKarma'sownerwithhisideaHewouldcollectandrepairusedbikesanddonate捐赠themtotheshop. Heexpectedtogetabout10donatedbikes.IntheendBarrettreceived39. ZacharyBlohm15Wisconsin The25yearoldplaygroundatanelementaryschoolnearMilwaukeeWis.wassosmallthatonly70ofits575studentscouldplayonitatatime. That'swhenZacharyBlohmsavedthedayHeandsomevolunteersbuiltahugeplayground.ToraisemoneyZacplannedTshirtandbakesalessoldticketsandmore.Heheldmonthlymoneyraisingeventsformorethanayear.Overallhecollected﹩130000﹣enoughtofinishhisproject. JackZimmerman16NewJersey Forsomepeoplefindingamealisassimpleasopeningtherefrigerator.Formorethan366000hungrykidsinNewJerseyit'snotthateasy. Thatfactdidn'tsitwellwithJackZimmermanwhoorganizedadrivetolessenchildhoodhungerinhisstate.Hisgoalcreate40000packagedmealsthatcouldbedonatedtothoseinneed.OngamedayJackandhisvolunteersstartedtheirwork.Afterthefinalcounttheteamhadpackaged47124meals﹣wellaboveJack'sgoal. 1Thepeacockfountainwasbuiltinapark. A.toinspirepeople B.fortheloveofanimals C.inmemoryofateenager D.toencourageacancersufferer 2WhatdidBarrettdoforKarmaBikeShop? A.Hedonatedbikestoit. B.Herepairedbikesthere. C.Hehelpeditwincustomers. D.Heofferedareadingservicethere. 3Whatdothefourpeoplehaveincommon? A.They'retopstudents. B.Theycareaboutothers. C.Theylikevariouspublicactivities. D.They'remoneyraisersforthepoor.
某科学家提出年轻热星体中核聚变的一种理论其中的两个核反应方程为H+C→N+Q1H+N→C+X+Q2方程式中Q1Q2表示释放的能量相关的原子核质量见下表
如图所示理想变压器输入端接在电动势随时间变化内阻为r的交流电源上输出端接理想电流表及阻值为R的负载变压器原副线圈匝数的比值为.如果要求负载消耗达到最大功率则下列说法正确的是
Itdidn'ttakealongtimeforhimto恢复fromhisillness.
Musicisoneofthemostimportantandpowerfulthingsinmylife.1listentomusiccanhelpmotivatemeinhardtimes. WhenIwasyoungerIdidn'thavethegreatlove2musicasIdonow.I3mainlistenedtowhatmyparentswerelisteningto.Ididn'thavemuchofcareformusicalcompositions.WhetherIwasinthecarthehouse4anywhereelsetherewassuretobesomeBeatlesBuddyHollyortheDubliners.NowasI'm5oldIenjoyitasitallowsme6remembermychildhood. Ibelievemusic7havetheabilitytoconveyallsortsoffeelings.Theeffectthatmusiccanhaveonour8emotionisunbelievableasitcanbringpeopletofloodsoftearsorburstsoflaughter. Ibelievemusicaffectspeopleinmanydifferentways.Tomemusicismorethanjust9welistentoorplayit'ssomethingtofeel.Inmylifeitismusicwhichisextremelyimportant10bringsmeclosertomyfriendsandfamily.Ialsofeelthatithelpsmetogetthroughthings.
某冋学利用如图甲所示装置研究匀变速直线运动规律.某次实验通过电磁打点计时器打出纸带的一部分如图乙所示图中ABCDE为相邻的计数点每两个相邻计数点间有4个计时点没有画出打点计时器所接交流电源频率为50Hz.分别测出A点到BCDE点之间的距离x1x2x3x4以打A点作为计时起点算出小车位移与对应运动时间的比值并作出﹣t图象如图丙所示. 1实验中下列措施必要的是填正确答案标号 A.打点计时器接220V交流电源B.平衡小车与长木板间的摩擦力 C.细线必须与长木板平行D.小车的质量远大于钩码的质量 2由图内中图象求出小车加速度a=m/s2打A点时小车的速度vA=m/s.结果均伓留两位有效数字
如图所示竖直平面内的直角坐标系中X轴上方有一个圆形有界匀强磁场图中未画出x轴下方分布有斜向左上与Y轴方向夹角θ=45°的匀强电场在x轴上放置有一挡板长0.16m板的中心与O点重合.今有一带正电粒子从y轴上某点P以初速度v0=40m/s与y轴负向成45°角射入第一象限经过圆形有界磁场时恰好偏转90°并从A点进入下方电场如图所示.已知A点坐标0.4m0匀强磁场垂直纸面向外磁感应强度大小B=粒子的荷质比=×103C/kg不计粒子的重力.问 1带电粒子在圆形磁场中运动时轨迹半径多大 2圆形磁场区域的最小面积为多少 3为使粒子出电场时不打在挡板上电场强度应满足什么要求
IntheUnitedStateswhenonebecomesrichhewantspeopletoknowit.Andevenifhedoesnotbecomeveryrichhewantspeopletothinkthatheis.ThatiswhatkeepingupwiththeJonesesisabout.Itisthestoryofsomeonewhotriedtolookasrichashisneighbors. Theexpressionwasfirstusedin1913byayoungAmericancalledArthurMomand.Hetoldthisstoryabouthimself.Hebeganearning$125aweekattheageof23.Thatwasalotofmoneyinthosedays.HegotmarriedandmovedwithhiswifetoaverywealthyneighborhoodoutsideNewYorkCity.WhenhesawthatrichpeoplerodehorsesMomandwenthorsebackridingeveryday.WhenhesawthatrichpeoplehadservantsMomandandhiswifealsohiredaservantandgavebigpartiesfortheirnewneighbors. Itwaslikearacebutonecouldneverfinishhisracebecauseonewasalwaystryingtokeepup.TheraceendedforMomandandhiswifewhentheycouldnolongerpayfortheirnewwayoflife.TheymovedbacktoanapartmentinNewYorkCity. Momandlookedaroundhimandnoticedthatmanypeopledothingsjusttokeepupwithrichlifestyleoftheirneighbors.Hesawthefunnysideofitandstartedtowriteaseriesofshortstories.HecalleditKeepingupwiththeJonesesbecauseJonesisaverycommonnameintheUnitedStates.KeepingupwiththeJonesescametomeankeepingupwithrichlifestyleofthepeoplearoundyou.Momand'sseriesappearedindifferentnewspapersacrossthecountryforover28years. PeopleneverseemtogettiredofkeepingupwiththeJoneses.AndthereareJonsesineverycityoftheworld.ButonemustgettiredoftryingtokeepupwiththeJonesesbecausenomatterwhatonedoesMr.Jonesalwaysseemstobeahead. 1SomepeoplewanttokeepupwiththeJonesesbecausethey. A.wanttobeasrichastheirneighbors B.wantotherstoknowortothinkthattheyarerich C.don'twantotherstoknowtheyarerich D.wanttobehappy 2Itcanbeinferred推断fromthestorythatrichpeopleliketo. A.liveoutsideNewYorkCity B.liveinNewYorkcity C.liveinapartments D.havemanyneighbors 3ArthurMomandusedthenameJonesinhisseriesofshortstoriesbecauseJonesis. A.animportantname B.apopularnameintheUnitedStates C.hisneighbor'sname D.notagoodname 4AccordingtothewriteritistokeepupwiththeJoneses. A.correct B.interesting C.impossible D.good 5What'stheauthor'sattitudetokeepingupwiththeJoneses? A.Negative B.Positive C.Objective D.Supportive
Childrenwhohavechancesto探索naturalareastendtolovescience.
材料相同质量不同的两滑块以相同的初动能在水平面上运动直到停止.若两滑块运动过程中只受到水平面的摩擦力则质量大的滑块
如图所示的xOy坐标系中x轴上固定一个点电荷Qy轴上固定一根光滑绝缘细杆细杆的下端刚好在坐标原点O处将一个套在杆上重力不计的带电圆环视为质点从杆上P处由静止释放圆环从O处离开细杆后恰好绕点电荷Q做圆周运动.下列说法正确的是
如图所示ab是x轴上关于O点对称的两点cd是y轴上关于O点对称的两点cd两点分别固定一等量异种点电荷带负电的检验电荷仅在电场力作用下从a点沿曲线运动到b点E为第一象限内轨迹上的一点以下说法正确的是
如图所示长木板AB倾斜放置板面与水平方向的夹角为θ在板的A端上方P点处以大小为v0的水平初速度向右抛出一个小球结果小球恰好能垂直打在板面上现让板绕A端顺时针转过一个角度到图上虚线的位置要让球从P点水平抛出后仍能垂直打在板面上则抛出的水平速度v不计空气阻力
IneversawmyfatherhomefromworklateorillnordidIeverseemyfathertakeanightoutwiththeboys.Hehadnobobbiesbutjusttookcareofhisfamily. For22yearssinceIlefthomeforcollegemyfathercalledmeeverySundayat900am.Hewasalwaysinterestedinmylife﹣howmyfamilywasdoing.ThecallsevencamewhenheandmymotherwereinAustraliaEnglandorFlorida. NineyearsagowhenIboughtmefirsthousemyfather67yearsoldspenteighthoursadayforthreedayspaintingmyhouse.Hewouldnotallowmetopaysomeonetohaveitdone.AllheaskedwasaglassoficedteaandthatIholdapaintbrushforhimandtalktohim.ButIwastoobusyforIhadalawpracticetorunandIcouldnottakethetimetoholdthepaintbrushortalktomyfather. Fiveyearsagomy71﹣year﹣oldfatherspentfivehoursputtingtogetheraswingset秋千formydaughter.AgainallheaskedwasthatIgethimaglassoficedteaandtalktohimButagainIhadlaundrytodoandthehousetoclean. ThemorningonSundayJanuary161995myfathertelephonedmeasusualthistimehehadseemedtohaveforgottensomethingswehaddiscussedtheweekbefore.IhadtogettochurchandIcuttheconversationshort. Thecallcameat440am.ThatdaymyfatherwassenttohospitalinFlorida.IgotonaplaneimmediatelyandIvowed发誓thatwhenIarrivedIwouldmakeupforthelosttimeandhaveanicelongtalkwithhimandreallygettoknowhim. IarrivedinFloridaat100ambutmyfatherhadpassedawayat912pm.Thistimeitwashewhodidnothavetimetotalkortimetowaitforme. IntheyearssincehisdeathIhavelearntmuchaboutmyfatherandevenmoreabouteverysingleday. 1Weknowfromthereadingthatthefather. A.likedtopainthouses B.hadnofriendsaroundhim C.wasnothealthyinhisyouth D.thoughtofhisfamilyashisall 2Whenherfatherpaintedherfirsthousethedaughter. A.couldonlyaffordaglassoficedtea B.wastoobusytotalktoherfather C.coulddonothingbutholdapaintbrush D.spenteighthoursadayworkingwithherfather 3OnJanuary161995thedaughterfeltthatherfather. A.seemedtobealittledifferent B.hadnotimetophoneherasusual C.becameinterestedinchurch D.hadforgottentodiscusssomethingswithher 4Inthereadingtheunderlinedphrase‘gettoknowhim'mostprobablymeans. A.gethimtoknowher B.knowmoreabouthim C.gethimtoknowhimself D.makehimwell﹣known 5Whichisthebesttitleofthereading? A.PaintingHouses B.Daughter'sFamily C.FatherandI D.Father'sphonecalls
已知月球半径为R飞船在距月球表面高度为R的圆轨道上飞行周期为T万有引力常量为G下列说法正确的是
假定你是李华你的加拿大笔友Susan正在学汉语她给你发来邮件询问你的近况并请你为她推荐﹣本汉语读物.请给她回复邮件要点如下 1.表示感谢 2.介绍你的近况学习生活等 3.推荐中国民间故事ChineseFolkTales. 注意 1.词数100左右 2.可适当增加细节以使行文连贯. DearSusan I'mmorethandelightedtohearfromyou.﹣﹣﹣﹣ Yours LiHua
2018年11月21日消息中科院合肥物质科学研究院核能安全所吴宜灿研究员获得美国核学会聚变核能杰出成就奖.关于核反应方程半衰期下列说法正确的是
某载人宇宙飞船绕地球做圆周运动的周期为T由于地球遮挡宇航员发现有T时间会经历“日全食”过程如图所示.已知地球的半径为R引力常量为G地球自转周期为T0太阳光可看做平行光则下列说法正确的是
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