首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   99849篇
  免费   899篇
  国内免费   965篇
  101713篇
  2023年   63篇
  2022年   117篇
  2021年   218篇
  2020年   139篇
  2019年   190篇
  2018年   11996篇
  2017年   10826篇
  2016年   7666篇
  2015年   1015篇
  2014年   696篇
  2013年   837篇
  2012年   4818篇
  2011年   13330篇
  2010年   12366篇
  2009年   8556篇
  2008年   10162篇
  2007年   11692篇
  2006年   582篇
  2005年   800篇
  2004年   1264篇
  2003年   1237篇
  2002年   996篇
  2001年   324篇
  2000年   204篇
  1999年   78篇
  1998年   56篇
  1997年   68篇
  1996年   47篇
  1995年   39篇
  1994年   43篇
  1993年   69篇
  1992年   50篇
  1991年   68篇
  1990年   46篇
  1989年   39篇
  1988年   39篇
  1987年   35篇
  1986年   19篇
  1985年   27篇
  1984年   38篇
  1983年   35篇
  1982年   27篇
  1981年   16篇
  1980年   17篇
  1979年   15篇
  1975年   18篇
  1972年   250篇
  1971年   282篇
  1965年   17篇
  1962年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
Systematics and taxonomy of hares of the genus Lepus (Lagomorpha) are under contentious debate, and phylogenetic relationships among many taxa are not well understood. Here we study genetic differentiation and evolutionary relationships among North African hares, currently considered subspecies of Lepus capensis , cape hares ( L. capensis ) from the Cape province in South Africa, and brown hares ( L. europeaus ) from Europe and Anatolia, using maternally (mtDNA) and biparentally (allozymes) inherited markers. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of a c. 1.8 kb long segment of the mitochondrial control region using eight hexanucleotide-recognizing restriction endonucleases yielded 28 haplotypes, and horizontal starch gel electrophoresis of proteins encoded by 25 structural gene loci revealed 52 alleles at 18 polymorphic loci. Diverse phylogenetic analyses (neighbor joining dendrogram, median joining network, multidimensional scaling of pairwise distances, AMOVA, F -statistics, hierarchical F -statistics) of genetic variants revealed marked substructuring of mtDNA into three phylogeographic groups, namely an African, a central European, and an Anatolian, but a somewhat less pronounced overall differentiation of the nuclear genome, despite a relatively high number of population-specific (private) alleles. However, all our results are not incongruent with Petter's (1959: Mammalia 23 , 41; 1961: Z. f. Säugetierkunde 26 , 30; 1972 : Société Des Sciences Naturelles et Physiques du Maroc 52 , 122) hypothesis that North African hares generally belong to L. capensis and that brown hares should be included in this species as well.  相似文献   
15.
16.
17.
Summary We have mapped and sequenced the globin gene and seven surrounding Alu repeat sequences in the orangutan globin gene cluster and have compared these and other orangutan sequences to orthologously related human sequences. Noncoding flanking and intron sequences, synonymous sites of , , and globin coding regions, and Alu sequences in human and orangutan diverge by 3.2%, 2.7%, and 3.7%, respectively. These values compare to 3.6% from DNA hybridizations and 3.4% from the globin gene region. If as suggested by fossil evidence and molecular clock calculations, human and orangutan lineages diverged about 10–15 MYA, the rate of noncoding DNA evolution in the two species is 1.0–1.5×10–9 substitutions per site per year. We found no evidence for either the addition or deletion of Alu sequences from the globin gene cluster nor is there any evidence for recent concerted evolution among the Alu sequences examined. Both phylogenetic and phenetic distance analyses suggest that Alu sequences within the and globin gene clusters arose close to the time of simian and prosimian primate divergence (about 50–60 MYA). We conclude that Alu sequences have been evolving at the rate typical of noncoding DNA for the majority of primate history.Presented at the FEBS Symposium on Genome Organization and Evolution, held in Crete, Greece, September 1–5, 1986  相似文献   
18.
The kinetics of haemolysis of rabbit erythrocytes byCroton tiglium lectin was studied as a function of concentration of the lectin and erythrocytes. The length of the prelytic period decreased with increasing lectin concentrations, indicating that the secondary events at the membrane which follow the binding of the lectin to cell surface carbohydrate receptors are accelerated at higher surface concentrations of the lectin. The rate or extent of haemolysis was not affected by the inclusion of ions like K+, Ca2+ and Mg2+ in the medium or by the substitution of ionic medium by a non-ionic medium. The inhibition of haemagglutination and haemolysis of rabbit red cells byCroton tiglium lectin by antilectin rabbit serum was observed. A possible mechanism of haemolysis by the lectin is discussed.  相似文献   
19.
N-Acetyl-D-galactosamine in β-linkage being ubiquitous in cell surface glycoproteins, their interaction with lectins specific for this sugar moiety may be a significant event in cell adhesion phenomena. This article discusses the common β-N-acetyl galactosamine-specific lectins, with particular stress on the lectin from winged beans (Psophocarpus tetragonolobus).  相似文献   
20.
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