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   3595篇
  免费   412篇
  2023年   18篇
  2022年   31篇
  2021年   74篇
  2020年   39篇
  2019年   49篇
  2018年   59篇
  2017年   50篇
  2016年   95篇
  2015年   187篇
  2014年   199篇
  2013年   180篇
  2012年   287篇
  2011年   242篇
  2010年   164篇
  2009年   123篇
  2008年   186篇
  2007年   211篇
  2006年   177篇
  2005年   181篇
  2004年   155篇
  2003年   145篇
  2002年   163篇
  2001年   61篇
  2000年   60篇
  1999年   51篇
  1998年   36篇
  1997年   36篇
  1996年   40篇
  1995年   29篇
  1994年   35篇
  1993年   21篇
  1992年   30篇
  1991年   27篇
  1990年   31篇
  1989年   34篇
  1988年   30篇
  1987年   48篇
  1986年   30篇
  1985年   29篇
  1984年   38篇
  1983年   28篇
  1982年   21篇
  1979年   26篇
  1978年   16篇
  1977年   17篇
  1976年   17篇
  1975年   19篇
  1974年   18篇
  1973年   20篇
  1969年   19篇
排序方式: 共有4007条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
Synthetic lysophospholipids represent a variety of analogs of the naturally occurring 2-lysophosphatidylcholine. Some of these compounds showed significant therapeutic effects on the survival of mice following radiation injury when administered after various doses of whole-body X irradiation. Such therapeutic effects were discernible even when the treatment was given 6 hr after irradiation, and both intravenous and oral application were effective. Intravenous application of 2 X 25 mg/kg lysophospholipid after whole-body X irradiation around the LD50 resulted in significantly higher numbers of surviving animals. The mode of action remains speculative.  相似文献   
7.
Cell lines derived from the small intestine that reflect authentic properties of the originating intestinal epithelium are of high value for studies on mucosal immunology and host microbial homeostasis. A novel immortalization procedure was applied to generate continuously proliferating cell lines from murine E19 embryonic small intestinal tissue. The obtained cell lines form a tight and polarized epithelial cell layer, display characteristic tight junction, microvilli and surface protein expression and generate increasing transepithelial electrical resistance during in vitro culture. Significant up-regulation of Cxcl2 and Cxcl5 chemokine expression upon exposure to defined microbial innate immune stimuli and endogenous cytokines is observed. Cell lines were also generated from a transgenic interferon reporter (Mx2-Luciferase) mouse, allowing reporter technology-based quantification of the cellular response to type I and III interferon. Thus, the newly created cell lines mimic properties of the natural epithelium and can be used for diverse studies including testing of the absorption of drug candidates. The reproducibility of the method to create such cell lines from wild type and transgenic mice provides a new tool to study molecular and cellular processes of the epithelial barrier.  相似文献   
8.
9.
Summary Different mushrooms, mosses and corresponding soil samples have been collected mainly from two sites in the alpine region of southwestern Bavaria. At the end of the growthseason, September 1986, gamma spectroscopic analysis showed that the moss-, mould, and needle-layer contained considerably more 134Cs and 137Cs activity per unit fresh weight than eight different species of mushroom. These two isotopes were carried into the biotop mainly as a consequence of the Chernobyl accident. 131J could not be found any more in the samples ca. 5–6 months after the catastrophe. The activity of the cesium isotopes decreased with increasing soil depth. In the mushrooms the activity was relatively high in Xerocomus badius and surprisingly low in Boletus edulis; samples of the latter and of Cantharellus cibarius collected in September 1985 (before the accident) and kept deep frozen contained almost identical amounts of 137Cs as those collected from August to October 1986. Mushrooms contained considerably more of the natural isotope 40K than the needlelayers and the soil samples in the neighbourhood. In all mushrooms except Xerocomus badius the activity of 40K was generally higher than the 137Cs activity. The results indicate that except Xerocomus badius the analyzed mushrooms do not actively take up Cs from the soil, in contrast to K.  相似文献   
10.
Summary Calli were initiated from immature embryos of nine lines of hexaploid wheat (Triticum aestivum L. em. Thell). These were the euploid lines Chinese Spring and Cappelle-Desprez, a line of Chinese Spring ditelocentric for the long arm of 4B, four substitution lines of Chinese Spring in which chromosome 4B has been replaced by its homologues from different wheat varieties and substituted into Chinese Spring and a substitution line of Besostaya I 4B into Cappelle-Desprez. The calli from these lines were found to differ in their growth rates and morphogenic and regenerative activities. The substitution of different 4B chromosomes into Chinese Spring significantly increased morphogenesis and shoot regeneration from callus. The potential for developing wheat lines with improved culture characteristics is 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