CT机将 X线锥形束限定为扇形束的部件是

A、滤过器
B、准直器
C、窗口
D、探测器
E、定位系统
查看答案
正确答案:

B

答案解析:

暂无解析

上一题
你可能感兴趣的试题

Whatdoesthefutureholdfortheproblemofhousing?Agooddealdepends,ofcourse,onthemeaningof“future”.Ifoneisthinkingintermsofsciencefictionandthespaceage,itisatleastpossibletoassumethatmanwillhavesolvedsuchtrivialandearthlyproblemsashousing.Writersofsciencefiction,fromH.G.Wellsonwards,havehadlittletosayonthesubject.Theyhaveconveyedthesuggestionthatmenwillliveingreatcomfort,witheveryconceivableapparatustomakelifesmooth,healthyandeasy,ifnothappy.Buttheyhavenotsaidwhathishousewillbemadeof.Perhapssomenewbuildingmaterial,asyetunimagined,willhavebeendiscoveredorinventedatleast.Onemaybecertainthatbricksandmortar(泥灰,灰浆)willlonghavegoneoutoffashion.

Buttheproblemsofthenextgenerationortwocanmorereadilybeimagined.Scientistshavealreadypointedoutthatunlesssomethingisdoneeithertorestricttheworld’srapidgrowthinpopulationortodiscoveranddevelopnewsourcesoffood(orboth),millionsofpeoplewillbedyingofstarvationoratthebestsufferingfromunderfeedingbeforethiscenturyisout.Butnobodyhasyetworkedoutanyplanforhousingthesegrowingpopulations.Admittedlytheworstsituationswilloccurinthehottestpartsoftheworld,wherehousingcanbelightstructureorinbackwardareaswherestandardsaretraditionallylow.Buteventheminimumshelterrequiresmaterialsofsomekindandintheteeming,bulgingtownsthelow-standard“housing”offlattenedpetrolcansanddirtycanvasisfarmorewastefulofgroundspacethancanbetolerated.

Sincethewar,HongKonghassufferedthekindofcrisiswhichislikelytoariseinmanyotherplacesduringthenextgeneration.Literallymillionsofrefugeesarrivedtoswellthealreadygrowingpopulationandemergencystepshadtobetakenrapidlytopreventsqualor(肮脏)anddiseaseandthespreadcrime.Thecityistacklingthesituationenergeticallyandenormousblocksoftenements(贫民住宅)arerisingatanastonishingaped.ButHongKongisonlyonesmallpartofwhatwillcertainlybecomeavastproblemandnotmerelyahousingproblem,becausewhenpopulationgrowsatthisratethereareaccompanyingproblemsofeducation,transport,hospitalservices,drainage,watersupplyandsoon.NoteveryareamaygivethesameresourcesasHongKongtodrawuponandthesearchforquickerandcheapermethodsofconstructionmustnevercease.

1.Whatistheauthor’sopinionofhousingproblemsinthefirstparagraph?

A.Theymaybecompletelysolvedatsometimeinthefuture.

B.Theyareunimportantandeasilydealtwith.

C.Theywillnotbesolveduntilanewbuildingmaterialhasbeendiscovered.

D.Theyhavebeendealtwithinspecificdetailinbooksdescribingthefuture.

2.Thewriterissurethatinthedistantfuture___.

A.bricksandmortarwillbereplacedbysomeotherbuildingmaterial.

B.anewbuildingmaterialwillhavebeeninvented.

C.bricksandmortarwillnotbeusedbypeoplewhowanttheirhousetobefashionable.

D.anewwayofusingbricksandmortarwillhavebeendiscovered.

3.Thewriterbelievesthatthebiggestproblemlikelytoconfronttheworldbeforetheendofthecentury___.

A.isdifficulttoforesee.

B.willbehowtofeedtheevergrowingpopulation.

C.willbehowtoprovideenoughhousesinthehottestpartsoftheworld.

D.isthequestionoffindingenoughgroundspace.

4.Whenthewritersaysthattheworstsituationswilloccurinthehottestpartsoftheworldorinbackwardareas,heisreferringtothefactthatintheseparts___.

A.standardsofbuildingarelow.

B.onlyminimumshelterwillbepossible.

C.thereisnotenoughgroundspace.

D.thepopulationgrowthwillbethegreatest.

5.WhichofthefollowingsentencesbestsummarizesParagraph3?

A.HongKonghasfacedaseriouscrisiscausedbymillionsofrefugees.

B.HongKonghassuccessfullydealtwiththeemergencycausedbymillionsofrefugees.

C.HongKong’scrisiswasnotonlyamatterofhousingbutincludedanumberofotherproblemsofpopulationgrowth.

D.ManypartsoftheworldmayhavetofacethekindofproblemsencounteredbyHongKongandmayfinditmuchhardertodealwiththem.

Questions1to5arebasedonthefollowingpassage:

Someyearsagothecaptainofashipwasveryinterestedinmedicine.Healwaystookmedicinebookstoseaandlikedtotalkaboutdifferentdiseases.

Onedayalazysailoronhisshippretendedtobeill.Helayonhisbunk(铺)andgroanedasifhewereverysick.Thecaptaincametoseehimandwasverypleasedtohaveapatienttolookafter.Hetoldthemantorestforafewdaysandmadetheothersailorsdohiswork.Threedayslateranothersailorpretendedthathehadsomethingwrongwithhischest.Oncemorethecaptainlookedinhismedicalbooksandtold“sick”mantohavearest.

Theothersailorswereveryangrybecausetheyhadmoreworktodo.Thepatientshadthebestfoodandlaughedattheirfriendswhenthecaptainwasnotlooking.Atlastthemate(船长副手)decidedtocurethe“sick”men.Hemixedupsomesoap,soot(烟灰),glue(胶水)andotherunpleasantthings.Thenheobtainedpermissionfromthecaptaintogivehismedicinetothe“sick”men.Whentheytastedthemedicine,theyreallydidfeelill.Itwassohorriblethatoneofthepatientsjumpedoutofhibunk,ranupondeskandclimbedthehighestmastontheship.Hedidnotwantanymoremedicine.

Thematetoldbothofthementhattheymusttakethemedicineeveryhalfanhour,nightandday.Thissooncuredthem.Theybothsaidtheyfeltbetterandwantedtostartwordagain.Thecaptainrealizedthatthementriedtodeceivehimsohemadethemworkveryhardfortherestofthevoyage.

1.Thefirstsailorpretendedtobeillbecausehewantedto.

A.testthecaptain’sknowledgeofmedicine

B.befreefromwork

C.havethebestfoodontheship

D.playajokeonhisfriends

2.Whenthecaptainknewasailorwasill,he.

A.didn’tcaremuch

B.sentforadoctor

C.lookedafterhimandtoldhimtohavearest

D.gavehimsomemedicine

3.Thepatientsfeltbetterquicklybecause.

A.theyhadbeengivenpropermedicine

B.theylearnedthatthecaptainhadfoundoutthetruth

C.theywerelaughedatbytheirfriends

D.themedicinethemategavewashorrible

4.Whenthecaptainknewhehadbeendeceived,he.

A.toldthemnottodosoagain

B.losthistemper

C.madethemworkharder

D.firedthem

5.Whichofthefollowingbestsummarizesthepassage?

A.AsuddenCure.

B.TwoPatients.

C.CaptainandSailors.

D.ADifficultVoyage.

PartIVTranslation

Bymakingvehicleslighterinweightaluminumhasgreatlyreducedtheamountoffuelneededtomovethem,(PassageTwo)

I_____thepartymuchmoreiftherehadn’tbeenquitesuchacrowdofpeoplethere.

A、wouldenjoy
B、willhaveenjoyed
C、couldhaveenjoyed
D、willbeenjoying

PARTVREADINGCOMPREHENSION

Inthissectiontherearefourpassagesfollowedbyquestionsorunfinishedstatements,eachwithfoursuggestedanswersmarkedA,B,CandD.Choosetheonethatyouthinkisthebestanswer.

TEXTA

Racket,dinclamor,noise,whateveryouwanttocallit,unwantedsoundisAmerica'smostwidespread

nuisance.Butnoiseismorethanjustanuisance.Itconstitutesarealandpresentdangertopeople'shealth.Day

andnight,athome,atwork,andatplay,noisecanproduceseriousphysicalandpsychologicalstress.Nooneis

immunetothisstress.Thoughweseemtoadjusttonoisebyignoringit,theear,infact,neverclosesandthe

bodystillresponds—sometimeswithextremetension,astoastrangesoundinthenight.

Theannoyancewefeelwhenfacedwithnoiseisthemostcommonoutwardsymptomofthestressbuilding

upinsideus.Indeed,becauseirritabilityissoapparent,legislatorshavemadepublicannoyancethebasisof

manynoiseabatementprograms.Themoresubtleandmoreserioushealthhazardsassociatedwithstress

causedbynoisetraditionallyhavebeengivenmuchlessattention.Nevertheless,whenweareannoyedormade

irritablebynoise,weshouldconsiderthesesymptomsfairwarningthatotherthingmaybehappeningtous,

someofwhichmaybedamagingtoourhealth.

Ofmanyhealthhazardstonoise,hearinglossisthemostclearlyobservableandmeasurablebyhealth

professionals.Theotherhazardsarehardertopindown.Formanyofus,theremaybeariskthatexposuretothe

stressofnoiseincreasessusceptibilitytodiseaseandinfection.Themoresusceptibleamongusmayexperience

noiseasacomplicatingfactorinheartproblemsandotherdiseases.Noisethatcausesannoyanceandirritability

inhealthpersonsmayhaveseriousconsequencesforthesealreadyillinmindorbody.

Noiseaffectsusthroughoutourlives.Forexample,thereareindicationsofeffectsontheunbornchildwhen

mothersareexposedtoindustrialandenvironmentalnoise.Duringinfancyandchildhood,youngstersexposed

tohighnoiselevelsmayhavetroublefallingasleepandobtainingnecessaryamountsofrest.

Why,then,istherenotgreateralarmaboutthesedangers?Perhapsitisbecausethelinkbetweennoiseand

manydisabilitiesordiseaseshasnotyetbeenconclusivelydemonstrated.Perhapsitisbecausewetendto

dismissannoyanceasapricetopayforlivinginthemodernworld.Itmayalsobebecausewestillthinkof

hearinglossasonlyanoccupationalhazard.

1.InParagraph1,thephrase"immuneto"areusedtomean___.

A.unaffectedby

B.hurtby

C.unlikelytobeseenby

D.unknownby

2.Theauthor'sattitudetowardnoisewouldbestbedescribedas___.

A.unrealistic

B.traditional

C.concerned

D.hysterical

3.Whichofthefollowingbeststatesthemainideaofthepassage?

A.Noiseisamajorproblem;mostpeoplerecognizeitsimportance.

B.Althoughnoisecanbeannoying,itisnotamajorproblem.

C.Noiseisamajorproblemandhasnotyetbeenrecognizedassuch.

D.Noiseisamajorproblemaboutwhichnothingcanbedone.

4.Theauthorcondemnsnoiseessentiallybecauseit___.

A.isagainstthelaw

B.canmakesomepeopleirritable

C.isanuisance

D.inagangertopeople'shealth

5.Theauthorwouldprobablyconsiderresearchabouttheeffectsnoisehasonpeopletobe___.

A.unimportant

B.impossible.

C.awasteofmoney

D.essential

热门试题 更多>
相关题库更多>
基础知识
专业知识
相关专业知识
专业实践技能
试卷库
试题库