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   3711篇
  免费   501篇
  国内免费   2篇
  2021年   61篇
  2020年   32篇
  2019年   46篇
  2018年   57篇
  2017年   63篇
  2016年   81篇
  2015年   102篇
  2014年   128篇
  2013年   205篇
  2012年   199篇
  2011年   175篇
  2010年   108篇
  2009年   109篇
  2008年   141篇
  2007年   141篇
  2006年   114篇
  2005年   125篇
  2004年   141篇
  2003年   120篇
  2002年   110篇
  2001年   101篇
  2000年   96篇
  1999年   95篇
  1998年   66篇
  1997年   54篇
  1996年   40篇
  1995年   44篇
  1994年   41篇
  1993年   49篇
  1992年   66篇
  1991年   75篇
  1990年   77篇
  1989年   60篇
  1988年   53篇
  1987年   71篇
  1986年   47篇
  1985年   50篇
  1984年   44篇
  1983年   48篇
  1982年   32篇
  1981年   40篇
  1979年   46篇
  1978年   40篇
  1977年   46篇
  1976年   35篇
  1975年   31篇
  1974年   38篇
  1973年   46篇
  1971年   33篇
  1968年   35篇
排序方式: 共有4214条查询结果,搜索用时 15 毫秒
1.
Few prospective studies support the use of anticoagulation during the acute phase of ischemic stroke, though observational data suggest a role in certain populations. Depending on the mechanism of stroke, systemic anticoagulation may prevent recurrent cerebral infarction, but concomitantly carries a risk of hemorrhagic transformation. In this article, we describe a case where anticoagulation shows promise for ischemic stroke and review the evidence that has discredited its use in some circumstances while showing its potential in others.  相似文献   
2.
PCR-generated conspecific sodium channel gene probe for the house fly.   总被引:3,自引:0,他引:3  
A segment of the house fly (Musca domestica) homologue of the para (paralytic) sodium channel gene of Drosophila melanogaster was isolated by using mixed sequence oligonucleotide primers in the polymerase chain reaction (PCR). The specificity of the procedure was demonstrated by genomic Southern analysis using the housefly PCR amplification product as a probe and by DNA sequence analysis. The latter showed structural homology to the para gene, but not to the corresponding region of DSC1, another D. melanogaster gene with structural similarity to vertebrate sodium channel genes.  相似文献   
3.
4.
5.
Abstract Four isolates of the non-motile species Aeromonas media , icluding the type strain, were demonstrated by transmission electronk microcopy to possess polar flagella. Motility appeared to be restricted to old, regularly subcultured strains, and coincided with an increase in colony size and a concomitant reduction in the amount of brown diffusible pigment produced by colonies on tryptone soya agar.  相似文献   
6.
Summary The rodent Harderian gland is an important site of porphyrin biosynthesis and storage. Porphyrins are visible at the light and electron microscope level as large intraluminal accretions, as large interstitial accretions surrounded by foreign body giant cells, or as small interstitial deposits within free macrophages. Since porphyrins are soluble in a wide range of solvents, it is important to employ histological routines which minimize porphyrin loss during processing in addition to giving good tissue preservation. In this quantitative investigation, these requirements were optimally achieved with fixation in 3% buffered glutaraldehyde and the use of amyl acetate as a clearing agent.  相似文献   
7.
Abstract— Colchichine blocks axoplasmic flow of proteins in chicken sciatic nerve. The slow component is more effectively blocked than the fast. The colchicine effect on slow flow is independent of the time delay between colchicine injection and that of the [14C]-leucine used to measure flow, over a period extending from 2 h after to 9 days before the leucine. It is still effective, but to a lesser degree, after a period of 27 days. There is little effect on the fast component when the colchicine is administered after leucine. When given before leucine the effect is not pronounced up to a time interval of 1 day. Maximum blockage was obtained with longer intervals of up to 27 days. These results are discussed in relation to the involvement of the microtubules in both slow flow and rapid flow.
The effect of both cytochalasins A and B on slow and rapid protein flow has also been studied. Neither drug had any significant effect on slow flow. Cytochalasin A reduced the amount of protein flowing at the rapid rate to a small extent when administered 2 h before [14C]leucine. Cytochalasin B also caused a similar reduction and this effect was independent of dose over the ranges of doses used. The cytochalasin B diminished the incorporation of amino acid into protein in the spinal cord and it has been concluded that these results are due to a membrane effect which reduces uptake of amino acid rather than a direct effect on neurofilaments in the axons.  相似文献   
8.
9.
10.
A new method for selecting RNA polymerase mutants   总被引:12,自引:0,他引:12  
  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