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   866674篇
  免费   96370篇
  国内免费   487篇
  2018年   8138篇
  2016年   10940篇
  2015年   14273篇
  2014年   17017篇
  2013年   24266篇
  2012年   27028篇
  2011年   27759篇
  2010年   18885篇
  2009年   17468篇
  2008年   24802篇
  2007年   25783篇
  2006年   24066篇
  2005年   23253篇
  2004年   22947篇
  2003年   21764篇
  2002年   21254篇
  2001年   39799篇
  2000年   39765篇
  1999年   31389篇
  1998年   10740篇
  1997年   11294篇
  1996年   10515篇
  1995年   9772篇
  1994年   9428篇
  1993年   9489篇
  1992年   25548篇
  1991年   24774篇
  1990年   24127篇
  1989年   23455篇
  1988年   21796篇
  1987年   20613篇
  1986年   19294篇
  1985年   19040篇
  1984年   15768篇
  1983年   13509篇
  1982年   10269篇
  1981年   9249篇
  1980年   8836篇
  1979年   15031篇
  1978年   11687篇
  1977年   10718篇
  1976年   10009篇
  1975年   10953篇
  1974年   12092篇
  1973年   11739篇
  1972年   10856篇
  1971年   9914篇
  1970年   8616篇
  1969年   8326篇
  1968年   7942篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
We have identified mouse and human FKBP60, a new member of the FKBP gene family. FKBP60 shares strongest homology with FKBP65 and SMAP. FKBP60 contains a hydrophobic signal peptide at the N-terminus, 4 peptidyl-prolyl cis/trans isomerase (PPIase) domains and an endoplasmic reticulum retention motif (HDEL) at the C-terminus. Immunodetection of HA-tagged FKBP60 in NIH-3T3 cells suggests that FKBP60 is segregated to the endoplasmic reticulum. Northern blot analysis shows that FKBP60 is predominantly expressed in heart, skeletal muscle, lung, liver and kidney. With N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide as a substrate, recombinant GST-FKBP60 is shown to accelerate effectively the isomerization of the peptidyl-prolyl bond. This isomerization activity is inhibited by FK506. mFKBP60 binds Ca2+ in vitro, presumably by its C-terminal EF-hand Ca2+ binding motif, and is phosphorylated in vivo. hFKBP60 has been mapped to 7p12 and/or 7p14 by fluorescence in situ hybridization (FISH).  相似文献   
2.
3.
Squilla mantis hemocyanin is composed of two hexameric subunits but has electron microscopic profiles different from other bis-hexameric hemocyanins, e.g. Astacus and Homarus. We distinguished three different electron microscopic profiles of S. mantis hemocyanin: two sideviews and a topview. These profiles were studied using computer image alignment and correspondence analysis [Van Heel, M. and Frank, J. (1981) Ultramicroscopy 6, 187 - 194]. With the results of this analysis we were able to build a three-dimensional model for the quaternary structure of this hemocyanin. In this model the two hexamers are stacked in such a way that their hexagonal surfaces overlap to about 60% of their width. In the overlap area four subunits are arranged in two different interhexameric pairs, each forming a bridging area between the two hexamers.  相似文献   
4.
5.
A patient with chronic anemia is presented who radiologically showed prominent rugae of the stomach. Angiography demonstrated an arteriovenous malformation with a large feeding artery and prominent draining veins.  相似文献   
6.
7.
8.
9.
Essential genes were identified in the 1.5-map unit dpy-5 unc-13 region of chromosome I in the Caenorhabditis elegans genome by rescuing lethal mutations using the duplication sDp2. In this paper, we report the mapping and complementation testing of lethal mutations, 45 of which identify 18 new, essential genes. This analysis brings the number of essential genes defined by the sDp2 rescue of lethal mutants to 97; 64 of these map between dpy-5 and unc-13. 61% of these essential genes are identified by more than one allele. Positioning of the mutations was done using the breakpoints of six duplications. The mutant phenotypes of 14 loci essential for fertility were characterized by Nomarski microscopy and DAPI staining. None of the mutants were rescued by wild-type male sperm. The cytological data showed that four genes produced mutants with defects in gonadogenesis, let-395, let-603, let-605 and let-610. Mutations in seven genes, let-355, let-367, let-384, let-513, let-544, let-545 and let-606, affected germ cell proliferation or gametogenesis. Mutants for the remaining three genes, let-370, let-599 and let-604, produced eggs that failed to develop or hatch, thereby acting as maternal effect lethals. We observed a nonrandom distribution of arrest phenotypes with regard to map position. Received: 8 May 1996 / Accepted : 27 January 1997  相似文献   
10.
E Weir 《CMAJ》2000,162(13):1843-1848
Raves are all-night dance parties attended by large numbers of youth, sometimes in excess of 20,000. The rave scene, which is international in scope, is distinguished by clandestine venues, hypnotic electronic music and the liberal use of drugs such as ecstasy (3,4-methylenedioxymethamphetamine), GHB (gamma-hydroxybutyrate) and ketamine. Several rave-related deaths in Canada in 1999 alerted health authorities, parents and police to the health risks of rave attendance. Family physicians, emergency physicians and pediatricians should have some understanding of raves, the drugs and the health risks so they can effectively counsel and treat patients. The rave culture in Canada and the drugs commonly used at raves are reviewed, and strategies and initiatives for harm reduction are discussed.  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