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   53187篇
  免费   4578篇
  国内免费   9篇
  2023年   261篇
  2021年   502篇
  2020年   401篇
  2019年   408篇
  2018年   1020篇
  2017年   1052篇
  2016年   1236篇
  2015年   1197篇
  2014年   1422篇
  2013年   2308篇
  2012年   3552篇
  2011年   3880篇
  2010年   2072篇
  2009年   1422篇
  2008年   3144篇
  2007年   3186篇
  2006年   2951篇
  2005年   2712篇
  2004年   2577篇
  2003年   2396篇
  2002年   2388篇
  2001年   1643篇
  2000年   1820篇
  1999年   1075篇
  1998年   539篇
  1997年   428篇
  1996年   498篇
  1995年   421篇
  1994年   453篇
  1993年   412篇
  1992年   555篇
  1991年   470篇
  1990年   449篇
  1989年   426篇
  1988年   396篇
  1987年   404篇
  1986年   362篇
  1985年   436篇
  1984年   489篇
  1983年   435篇
  1982年   398篇
  1981年   365篇
  1980年   326篇
  1979年   339篇
  1978年   335篇
  1977年   312篇
  1976年   305篇
  1975年   354篇
  1974年   302篇
  1973年   280篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The bacterial flagellum is composed of more than 20 different proteins. The filament, which constitutes the major extracellular part of the flagellum, is built up of approximately 20,000 FliC molecules that assemble at the growing distal end of the filament. A capping structure composed of five FliD molecules located at the tip of the filament promotes polymerization of FliC. Lack of FliD leads to release of the subunits into the growth medium. We show here that FliD can be successfully used in bacterial surface display. We tested various insertion sites in the capping protein, and the optimal region for display was at the variable region in FliD. Deletion and/or insertion at other sites resulted in decreased formation of flagella. We further developed the technique into a multihybrid display system in which three foreign peptides are simultaneously expressed within the same flagellum, i.e., D repeats of FnBPA from Staphylococcus aureus at the tip and fragments of YadA from Yersinia enterocolitica as well as SlpA from Lactobacillus crispatus along the filament. This technology can have biotechnological applications, e.g., in simultaneous delivery of several effector molecules.  相似文献   
32.
33.
Comparative chromosome painting with individual human chromosome-specific libraries (CSLs) on cattle metaphase chromosomes delineated 46 homologous chromosomal segments between the two species. Continuous arrangement of these segments on individual cattle chromosomes demonstrates a nearly complete coverage of the bovine karyotype and shows physical boundaries of bovine chromosomal segments homologous to individual human chromosomes. Alignment of the available comparative gene mapping data with the homologous segments strongly supports the detected gross homologies between the karyotypes of the two species. In addition to cattle, four human CSLs were hybridized to sheep metaphase chromosomes also, to further verify the known karyotype homology within the Bovidae. Besides its application to karyotype evolution research, the comparative knowledge provides for rapid expansion of the much needed Type I locus-based bovine gene map. Received: 9 September 1995 / Accepted: 4 December 1995  相似文献   
34.
35.
Abstract

The antioxidant effects of ellagic acid (EA) and hesperidin (HES) against skeletal muscle ischemia/reperfusion injury (I/R) were performed. Hindlimb ischemia has been induced by tourniquet occlusion for 2?h on left hindlimb. At the end of ischemia, the tourniquate has been removed and initiated reperfusion for 2?h. EA (100?mg/kg) has been applied orally before ischemia/reperfusion in the EA?+?I/R group. HES (100?mg/kg) has been given orally in the HES?+?I/R group. The left gastrocnemius muscle has been harvested and stored immediately at??80?°C until assessed for the levels of MDA and antioxidant enzymes activities. MDA level has statistically increased in I/R group (p?<?0.05) compared to other groups. The muscle tissue antioxidant enzymes activities were lower than the other groups in the I/R group (p?<?0.05). EA and HES treatments significantly reversed the damage level in I/R, also activity of tissue SOD increased in the EA?+?I/R and HES?+?I/R groups.  相似文献   
36.
37.
38.
39.
40.
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