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   830522篇
  免费   90904篇
  国内免费   668篇
  2018年   8140篇
  2017年   7562篇
  2016年   10977篇
  2015年   15236篇
  2014年   17720篇
  2013年   25123篇
  2012年   28045篇
  2011年   28288篇
  2010年   19262篇
  2009年   17425篇
  2008年   24953篇
  2007年   25427篇
  2006年   24009篇
  2005年   23103篇
  2004年   23012篇
  2003年   22033篇
  2002年   21329篇
  2001年   38924篇
  2000年   39033篇
  1999年   31070篇
  1998年   11018篇
  1997年   11470篇
  1996年   10759篇
  1995年   10028篇
  1994年   9723篇
  1993年   9528篇
  1992年   25085篇
  1991年   24307篇
  1990年   23673篇
  1989年   23040篇
  1988年   21336篇
  1987年   19950篇
  1986年   18497篇
  1985年   18341篇
  1984年   15254篇
  1983年   12726篇
  1982年   9654篇
  1981年   8637篇
  1980年   8087篇
  1979年   13646篇
  1978年   10618篇
  1977年   9597篇
  1976年   8704篇
  1975年   9652篇
  1974年   10298篇
  1973年   10177篇
  1972年   9088篇
  1971年   8299篇
  1970年   7086篇
  1969年   6854篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A cDNA probe corresponding to the mRNA sequence for apolipoprotein E (apo E) was used to screen two independently-constructed human genomic libraries. Two recombinants (lambda E-2, and lambda E2-1), isolated using the apo E cDNA probe, also contain part or all of the apo CI gene. Hybridisation studies using both apo E and apo CI cDNA probes show that these two genes are in the same orientation and separated by 4 kb.  相似文献   
992.
H Arai  M Berne  G Terres  H Terres  K Puopolo  M Forgac 《Biochemistry》1987,26(21):6632-6638
The partially purified proton-translocating adenosinetriphosphatase [(H+)-ATPase] from clathrin-coated vesicles has been reported to contain eight polypeptides of molecular weights 15,000-116,000 [Xie, X.S., & Stone, D.K. (1986) J. Biol. Chem. 261, 2492-2495]. To determine whether these polypeptides form a single macromolecular complex, we have isolated three monoclonal antibodies which recognize the reconstitutively active (H+)-ATPase in the native, detergent-solubilized state. All three monoclonal antibodies precipitate the same set of polypeptides from either the partially purified enzyme or the detergent-solubilized coated vesicle membrane proteins. The immunoprecipitated polypeptides have molecular weights of 100,000, 73,000, 58,000, 40,000, 38,000, 34,000, 33,000, 19,000, and 17,000. These results thus indicate that this set of polypeptides forms a single macromolecular complex and suggest that they correspond to subunits of the coated vesicle (H+)-ATPase. To identify the ATP-hydrolytic subunit of the coated vesicle (H+)-ATPase, the purified enzyme was reacted with N-ethylmaleimide (NEM) and 7-chloro-4-nitro-2,1,3-benzoxadiazole (NBD-Cl), both of which inhibit activity in an ATP-protectable manner. Labeling was carried out by using [3H]NEM or [14C]NBD-Cl, and the specificity of the reaction was increased by prelabeling of the protein with the nonradioactive reagents in the presence of ATP and by taking advantage of the nucleotide specificity of protection. The principal polypeptide labeled by both [3H]NEM and [14C]NBD-Cl had a molecular weight of 73,000. In addition, this protein was the only polypeptide whose labeling was significantly reduced in the presence of ATP.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
993.
The complete amino acid sequence of histone H3 (135 residues) from the nematode Caenorhabditis elegans has been established. Microheterogeneity occurs at positions 96 and 100 of the chain. The sequences of the nematode H3 isoforms are very similar to the major chain of calf thymus H3 with which they show 4 substitutions in total. The major variant has cysteine in position 96. This is the first report of cysteine in this position in H3 from non-mammalian tissue. An exceptional methylation site has been detected at position 79. Various other sites of secondary modification are of a conservative nature.  相似文献   
994.
The effect of selection for methidathion resistance on fitness components of aP. persimilis strain was analysed by different means. The resistant strain was compared with the susceptible one from which it was selected. The life history and some parameters essential to the successful use of this species in biological control (voracity, resistance to starvation and drought) were analysed. Methidathion resistance was followed for 6 months under rearing conditions free of insecticide in the resistant and in a mixed strain. The investigations showed that the fitness of resistant mites did not seem altered by methidathion selection. It thus appears possible to increase pesticide resistance in beneficial arthropods without adversely affecting their main fitness components.  相似文献   
995.
996.
997.
998.
999.
1000.
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