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   23615篇
  免费   2065篇
  国内免费   10篇
  2023年   88篇
  2022年   240篇
  2021年   490篇
  2020年   308篇
  2019年   387篇
  2018年   525篇
  2017年   451篇
  2016年   707篇
  2015年   1126篇
  2014年   1288篇
  2013年   1460篇
  2012年   2009篇
  2011年   1776篇
  2010年   1208篇
  2009年   1115篇
  2008年   1490篇
  2007年   1503篇
  2006年   1348篇
  2005年   1305篇
  2004年   1206篇
  2003年   1112篇
  2002年   999篇
  2001年   254篇
  2000年   216篇
  1999年   250篇
  1998年   283篇
  1997年   199篇
  1996年   166篇
  1995年   133篇
  1994年   144篇
  1993年   127篇
  1992年   133篇
  1991年   106篇
  1990年   144篇
  1989年   118篇
  1988年   109篇
  1987年   102篇
  1986年   66篇
  1985年   95篇
  1984年   104篇
  1983年   71篇
  1982年   90篇
  1981年   82篇
  1980年   57篇
  1979年   52篇
  1978年   44篇
  1977年   38篇
  1976年   35篇
  1974年   32篇
  1973年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
123.
124.
125.
126.
127.
Ejaculated sperm from the domestic ferret (Mustela putorius furo) and the black-footed ferret (Mustela nigripes) were compared for differences in morphological abnormalities and argentophilic protein distribution. Thawed domestic ferret sperm was also compared to fresh sperm to determine whether there were any effects on cell morphology due to cryopreservation. There were statistically significant differences between the two species of ferret in two of the categories scored. The domestic ferret had a higher frequency of cells that were bent in the midpiece and in the principal piece, and a higher frequency of headless and tailless cells when compared to the black-footed ferret. There were no statistically significant differences in cell morphology between the fresh and cryopreserved ejaculates of the domestic ferret employing a standard egg yolk cryoextender. Silver nitrate staining distribution was different between the two species in both the head and tail region.  相似文献   
128.
A fast and sensitive multiple sequence alignment algorithm   总被引:4,自引:0,他引:4  
A two-step multiple alignment strategy is presented that allowsrapid alignment of a set of homologous sequences and comparisonof pre-aligned groups of sequences. Examples are given demonstratingthe improvement in the quality of alignments when comparingentire groups instead of single sequences. The modular designof computer programs based on this algorithm allows for storageof aligned sequences and successive alignment of any numberof sequences. Received on August 23, 1988; accepted on December 6, 1988  相似文献   
129.
During the maturation of the oocytes of the frog Xenopus laevis, the rate of protein synthesis shows a twofold increase. Studies of the mechanisms involved in this stimulation have been seriously limited by the lack of an active cell-free translation system. We have now prepared such systems from oocytes, progesterone-matured oocytes and eggs of Xenopus laevis by induction of lysis by centrifugation of whole cells. The extracts are highly active in incorporation of labelled amino acids and, in the progesterone-matured and egg extracts, a substantial proportion of this is due to reinitiation on endogenous mRNA, as shown by the use of inhibitors. The increased rate of protein synthesis previously observed in intact oocytes following progesterone-induced maturation is reflected in the relative activities of the extracts. The difference in activity is not due to the presence of a dominant inhibitor of translation in the extracts from unstimulated oocytes. Labelling studies with initiator tRNA ([35S]Met-tRNAf) indicate a higher concentration of 43S preinitiation complexes in the extracts from unstimulated oocytes, suggesting an impairment of initiation of translation at or after the mRNA-binding step. Extracts from both oocytes and progesterone-matured oocytes translated endogenous mRNAs to give products ranging over a wide spectrum of molecular weight. However, significant translation of exogenous (globin) mRNA required the presence of reticulocyte postribosomal supernatant, suggesting that one or more factors required for mRNA recruitment is limiting in these extracts.  相似文献   
130.
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