首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 234 毫秒
1.
AnoldChinesemythsaysthereusedtobeahorribleperiodwhentenwickedsunscameouttogetherandburntoutallcrops.Thencamethegreathero,HouYi,whokillednineofthesunswithhispowerfulbowandarrows.Ofcoursethesuninthismythisahostileimage.Itissincethetimethestorycameintob…  相似文献   

2.
IntroductionInordertomitigatetheproblemsofenergyshortage,environmentalpollutionandtheoverburdenedtransportationsystemsinChina,underthesupportofthestate,thenuclearheatingreactor(NHR)wasdevelopedbytheInstituteofNuclearEnergyTechnology(INET),TsinghuaUni…  相似文献   

3.
IntroductionInmodernengineeringapplications,filtrationhasbecomeawidelyusedwater treatmentprocessintheproductionofpotablewaterandinwastewatertreatment.Theapplicationoffiltersindrinkingwatertreatmenthasalongtradition ,thedesignandtheoperationarebasedonlo…  相似文献   

4.
IntroductionWiththedevelopmentofindustrialproductionandcitylife ,largeamountofindustrialwastewateranddomesticsewageareex haustedtotherivercourse,whichleadstothedegradationoftheriverwater.Nowadays,mostoftheriversinourcountryarepol lutedintheirrespectivel…  相似文献   

5.
IntroductionSelectionofaproperdryingmethodisveryimportantfordry ingofhighlyviscousandheat sensitivefoods.Vacuumdryingisconsideredasasuitablemethodfordryingofsuchmaterials .Ac cordingtoseveralresearchreportsbyNotter,BrekkeandTaylor,itresultsinproductswhic…  相似文献   

6.
IntroductionWhenthehomogeneoussolutionbecomesthermodynamicallyunstable (e g ,bytheintroductionofanonsolvent) ,thesolutionseparatesintotwoliquidphasesofdifferentcompositiontolowerthefreeenergyofthemixture Thisprocessisresponsibleforthegenerationoftheporou…  相似文献   

7.
Identification of the Material Parameters of Laminated Plates   总被引:7,自引:0,他引:7  
IntroductionForstructuralmembersconstructedofisotropicmaterials,thematerialpropertiescanbedeterminedbyroutinemeasurementsoftypicalspecimens.However,forcompositematerials,theheterogeneityandanisotropymakeidentificationofthematerialpropertiesmorecomplica…  相似文献   

8.
EarlyPleistoceneisarelativelylongperiodingeologichistory,inwhichthestudyofenvironmentalevolutionisnotenoughtocomparewiththatofLatePleistoceneandHolocene.Dingetal.(1994)havestudiedthewintersummermonsoonalternationsandtherelatedenvironmentalfeaturesin…  相似文献   

9.
City’sstandardplotsaresomelandblockssetupinaregion,whichlandquality,individualfactors,landusebenefitandpricearerepresentat...  相似文献   

10.
DiscusionOntheSemanticsandCultureWangJianwu(Dept.ofB.C.ofShaanxiInstituteofTechnology)Abstract:Thispaperfocusesonhowsemantics...  相似文献   

11.
The mitochondrial DNA cytochrome b gene was sequenced from 8 bagrid catfishes in China. Aligned with cytochrome b sequences from 9 bagrid catfishes in Japan, Korea and Russia retrieved from GenBank, and selected Silurus meridionalis, Liobagrus anguillicauda, Liobagrus reini and Phenacogrammus interruptus as outgroups, we constructed a matrix of 21 DNA sequences. The Kimura's two-parameter distances were calculated and molecular phylogenetic trees were constructed by using the maximum parsimony (MP) and neighbor-joining (NJ) methods. The results show that (i) there exist 3-bp deletions of mitochondrial cytochrome b gene compared with cypriniforms and characiforms; (ii) the molecular phylogenetic tree suggests that bagrid catfishes form a monophyletic group, and the genus Mystus is the earliest divergent in the East Asian bagrid catfishes, as well as the genus Pseudobagrus is a monophyletic group but the genus Pelteobagrus and Leiocassis are complicated; and (iii) the evolution rate of the East Asian bagrids mitochondrial cytochrome b gene is about 0.18%~0.30% sequence divergence per million years.  相似文献   

12.
描述了瓦氏黄颡、粗唇(鱼危)、乌苏拟鲿和大鳍鳠共4种鲶形目鲿科鱼类肾的外形,发现这4种鱼类的两肾有不同程度的愈合,愈合后的尾端形态:瓦氏黄颡和粗唇(鱼危)逐渐变细;乌苏拟鲿较尖长;大鳍鳠的肾在愈合后的尾端延伸最细长.4种鱼的头肾和肾都是分离的,但前3种鱼的头肾为一叶;而大鳍鳠的头肾个体变异较多,有的为一叶,有的为二叶,有的则为部分愈合的二叶.4种鲶形目鱼类的肾前面有索状肾组织存在,但存在的情况也不一致,因此认为,4种鱼类肾的外形确有种间差异,并首次在本文中描述了粗唇(鱼危)和大鳍鳠的肾脏形态有较大的个体变异.这与Ogawa提出的将硬骨鱼肾的外形分为5种类型,并将鲶类归为Ⅱ型肾的结论不同,而与Singhs,Sahais根据10种印度淡水硬骨鱼所提出的“肾的外形有很大的差异甚至在种内也有变异”的意见一致.作者还注意到鲿科中的长吻(鱼危)的幼体,体重100—150g的肾脏前端确有一条细长索状的肾组织与头肾相连,与Ogawa描述的两种鲶类相同,但 Ogawa所取两种鲶鱼材料的体长分别为120mm和80mm.我们认为均应属幼体范围,这是因为长吻(鱼危)的成体长索的前段退化,头肾与肾完全分离与其他4种鲿科鲶类一样.说明鲶类在随体长体重的增长,肾的形态亦会发生变化.因此,也不能如Ogawa所说单从肾的外形去探讨其系统演  相似文献   

13.
拟鲿属鱼类分类学研究概况   总被引:1,自引:0,他引:1  
拟鲿属(Pseudobagrus)是鲿科鱼类中物种数目较多的一个属,为东亚所特有,中国为其主要分布区域。目前,拟鲿属的分类仍然存在较大的问题,表现在:大量已描述物种的有效性需要重新验证;未描述的物种急待发现;属的界定和属下分类需要重新评估。因此,有必要对中国拟鲿属分类展开深入地探讨。本文对拟鲿属的分类学研究进展及分类中存在的问题进行系统回顾及阐述,旨在为拟鲿属物种的分类和系统学研究提供全面的参考。  相似文献   

14.
对从嘉陵江合川至北碚段收集的4属11种科鱼类脊头骨作了系统的比较研究。结果表明,属、黄颡鱼属、拟属和属在下颞骨的有无,嗅神经孔和舌颌骨与颅骨关节面的构成,泪骨的形态,上枕骨嵴的长短及其与背鳍第一辐鳍骨的关系,颅骨的比例性状等方面具有一分明显的属间差异,头骨形态亦可作为种间分类的重要依据之一。  相似文献   

15.
Afast startisahigh energyswimmingburststartingeitherfromrestorfromsteadyswimming[1] .Thefast startsareclassifiedintotwomaintypes ,C startandS start ,inwhichthefishbodyisbentintoa‘C’or‘S’shapeattheendofthefirstcontractionofthelateralmusculature .Fast startsareimportantformostfishinescapingpredatorsandachieving preycapture .Afast startprocesshastwoamazingcharac teristics.Oneistheturningmaneuver .Theturningmaneuveriscarriedoutveryrapidly ,withtheturningdiameterbeingequalto ,orevenlessthanth…  相似文献   

16.
The kinematics and hydrodynamics of the escape response of yellow catfish ( Pelteobagrus fulvidraco ) is investigated.It is observed from digital high-speed camera that all the escape response of yellow catfish is a C-type fast-start, which is characterized by the C-shape of the fish body at the end of the first contraction of the lateral musculature. Based on the analysis of the mass center movement and the performance of the caudal fin, the fast-start process can be divided into two stages: in stage one the fish body rotates rapidly around its mass center and in stage two the fish begins moving straightly. Theoretically, the Weihs' model is employed to obtain the forces, moments and turning angular accelerations acting on the fish during the escape response. The results are in good agreement with the experimental observation. Furthermore, muscle strain at different locations along the body is calculated. At last, the dynamical performance of the escape response is explained.  相似文献   

17.
对分别属于食用型、兼用型和油用型的不同品种向日葵在萌动时期的酯酶同工酶研究后发现:供研究的3个类型的所有品种,有4条共同酶带,可分为两类酶谱型;乌苏小葵花有一条较原始酶带;所分析的杂交品种分别为母本型和互补型;值得注意的是兼用型和油用型的品种都有一条“油型酶带”,而食用型则没有.  相似文献   

18.
11种鲇形目鱼的血液检测与比较分析   总被引:4,自引:0,他引:4  
测定了大口鲇、鲇、杂交鲇、革胡子鲇、黄颡鱼、长吻鱼危、条纹拟鱼尝、青石爬鱼兆、斑点叉尾鱼回、白缘鱼央、黑尾鱼央、拟缘鱼央等11种鲇形目鱼12个样品的血细胞数量、血红蛋白浓度以及血清铁浓度,比较了它们的血清转铁蛋白分区和带谱以及红细胞形态差异,初步确定了鱼类的血液可作为渔业生产上鱼类疾病或生产性状的检测指标,并对鲇形目鱼类耐低氧和底栖的生活特性进行了分析.  相似文献   

19.
对Hsu,Wu和Wu提出的门限代理签名方案的安全性进行了分析,表明该方案易受内部攻击,即原始签名人及代理签名人都可通过改变公钥,成功地伪造有效的代理签名.基于Hsu等人的方案,提出了一个改进方案,新方案消除了Hsu等人方案的某些安全缺陷.  相似文献   

20.
日语的声调为高低型,一个假名代表一个音节。其中,名词按音节数排列起来,可分成平板式和起伏式,当名词后接助词、助动词时,原声调若是平板式时,则句节平接;若为起伏式,后接的助词、助动词均要低读。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号