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   77772篇
  免费   6669篇
  国内免费   40篇
  84481篇
  2022年   493篇
  2021年   955篇
  2020年   570篇
  2019年   729篇
  2018年   938篇
  2017年   877篇
  2016年   1461篇
  2015年   2414篇
  2014年   2756篇
  2013年   3793篇
  2012年   4649篇
  2011年   4795篇
  2010年   3157篇
  2009年   2857篇
  2008年   4223篇
  2007年   4341篇
  2006年   4151篇
  2005年   4113篇
  2004年   4214篇
  2003年   3800篇
  2002年   3806篇
  2001年   898篇
  2000年   641篇
  1999年   918篇
  1998年   1201篇
  1997年   868篇
  1996年   803篇
  1995年   768篇
  1994年   755篇
  1993年   702篇
  1992年   653篇
  1991年   629篇
  1990年   610篇
  1989年   642篇
  1988年   557篇
  1987年   537篇
  1986年   486篇
  1985年   614篇
  1984年   759篇
  1983年   648篇
  1982年   771篇
  1981年   801篇
  1980年   727篇
  1979年   513篇
  1978年   566篇
  1977年   532篇
  1976年   537篇
  1975年   407篇
  1974年   505篇
  1973年   468篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
51.
52.
53.
A simple modification of nuclear staining after acid hydrolysis has been made which provides easy identification of quail nuclear markings in a chick-quail chimera. This method also improves the histologic detail normally seen with hematoxylin and eosin when compared to the more commonly used Feulgen reaction. Embryonic tissues can be fixed in Zenker's or Helly's solution and the sections obtained are hydrolyzed in acid (3.5 N HCl at 37 C for 40-50 min). After acid hydrolysis the sections are stained with hematoxylin and eosin rather than Schiff reagent and fast green. The interphase nuclei of chick cells show homogeneous or mottled purplish blue staining, while quail nuclei contain a dark blue spot. This staining corresponds to the reddish purple staining of the quail's heterochromatin seen adjacent to the nucleolus in the standard Feulgen stain. This new technique facilitates identification of quail cell types in the chick host and provides superior histology of the chick tissues by demonstrating cytoplasmic detail.  相似文献   
54.
55.
The accumulation of several hundred proteins during the nuclear division cycle of Physarum polycephalum was measured by digital image processing of silver-stained two-dimensional (2D) polyacrylamide gels. In contrast to previous studies, we have used an organism with a naturally synchronous cell cycle, so there are no uncertainties concerning synchronization artifacts or cell-sorting artifacts, and we have measured the specific amounts of each protein rather than the rate of synthesis. Since one-dimensional SDS-PAGE shows no significant fluctuations in the most abundant plasmodial proteins, we have loaded 2D gels so that proteins of low-to-moderate abundance appear in the linear range of the silver stain standard curve. Only five proteins showed reproducible, measureable fluctuations during the cell cycle. One of these proteins was tubulin. Full quantitative information was obtained by analysing the digital images of silver-stained gels by a general image processing system.  相似文献   
56.
57.
Synthetic 125I-labelled N-(2-hydroxypropyl)methacrylamide copolymers containing four different, potentially degradable peptidyl side chains were incubated with rat visceral yolk sacs cultured in vitro. All copolymers were captured by fluid-phase pinocytosis and three of the side chains were susceptible to lysosomal hydrolysis, resulting in release of [125I]iodotyrosine back into the culture medium. Uptake and degradation was completely inhibited by 2,4-dinitrophenol. The thiol-proteinase inhibitor leupeptin did not affect the rate of pinocytosis, but caused different degrees of inhibition of hydrolysis depending on side chain composition.  相似文献   
58.
Enveloped virus glycoproteins exhibit membrane fusion activity. We have analysed whether the G protein of vesicular stomatitis virus, reconstituted into liposomes, is able to fuse nucleated cells in a pH-dependent fashion. Proteoliposomes produced by octylglucoside dialysis did not exhibit cell fusion activity of the G protein. However, by making use of n-dodecyl octaethylene monoether (C12E8) as the solubilizing agent and by removal of the detergent in two steps, we were able to produce fusogenic G protein liposomes. These G protein liposomes fuse to the BHK-21 cell surface at pH 5.7-6.0 with an efficiency of fusion comparable with that of the parent virus. Physical and chemical analysis revealed that the fusogenic liposomes exhibited a protein to lipid weight ratio of 0.67 and showed an average diameter of 130 nm.  相似文献   
59.
60.
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