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   41796篇
  免费   3698篇
  国内免费   205篇
  45699篇
  2018年   494篇
  2017年   480篇
  2016年   622篇
  2015年   700篇
  2014年   902篇
  2013年   1073篇
  2012年   1220篇
  2011年   1257篇
  2010年   851篇
  2009年   862篇
  2008年   1173篇
  2007年   1164篇
  2006年   1176篇
  2005年   1002篇
  2004年   962篇
  2003年   910篇
  2002年   886篇
  2001年   2774篇
  2000年   2454篇
  1999年   1799篇
  1998年   612篇
  1997年   525篇
  1996年   470篇
  1995年   400篇
  1994年   386篇
  1992年   1279篇
  1991年   1158篇
  1990年   1095篇
  1989年   1043篇
  1988年   928篇
  1987年   922篇
  1986年   802篇
  1985年   793篇
  1984年   563篇
  1983年   513篇
  1982年   366篇
  1979年   630篇
  1978年   451篇
  1977年   414篇
  1976年   368篇
  1975年   494篇
  1974年   575篇
  1973年   553篇
  1972年   571篇
  1971年   548篇
  1970年   520篇
  1969年   526篇
  1968年   426篇
  1967年   373篇
  1966年   409篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
M Krugliak  Z Waldman  H Ginsburg 《Life sciences》1987,40(13):1253-1257
Human erythrocytes were loaded with either gentamicin or amikacin and subsequently infected with the human malarial parasite Plasmodium falciparum and grown in culture. Parasite invasion of erythrocytes was unaffected by the drugs, but subsequent development was retarded. The digestion of host cell cytosol in ring-stage parasites was inhibited by the drugs. A substantial acid, Ca2+-independent phospholipase activity could be monitored in parasite cytosol and was found to be inhibited by the drugs. These results imply that phospholipases are involved in the feeding mechanism of the parasite and that gentamicin and amikacin exert their inhibitory activity by affecting these enzymes.  相似文献   
2.
We propose a mathematical model for pendelluft flow in a single airway bifurcation. The model is motivated by an apparatus used in an experimental study of the pendelluft by Ultman et al. (1988). We derive differential equations governing the fluid flow, which directly connect physiological parameters to the variables determining the pendelluft; this approach allows us to include nonlinearity in the model. If nonlinearity is neglected, our model is identical to the R-I-C circuits used by previous investigators. If nonlinearity is retained, we show that pendelluft can occur even in perfectly symmetric airway bifurcations. For the specific apparatus used in the experiments of High et al. (1991), we demonstrate that two qualitatively different pendelluft flows can occur in the system.  相似文献   
3.
4.
An agar-degrading marine bacterium identified as a Microscilla species was isolated from coastal California marine sediment. This organism harbored a single 101-kb circular DNA plasmid designated pSD15. The complete nucleotide sequence of pSD15 was obtained, and sequence analysis indicated a number of genes putatively encoding a variety of enzymes involved in polysaccharide utilization. The most striking feature was the occurrence of five putative agarase genes. Loss of the plasmid, which occurred at a surprisingly high frequency, was associated with loss of agarase activity, supporting the sequence analysis results.  相似文献   
5.
6.
7.
Intensive synthesis of collagen-like substance was revealed in the rabbit myocardium during experimental diphtheria intoxication. It was more marked in the right ventricle 24 hours after the injection of diphtheria toxin. Since similar changes (the substance was mainly formed around blood vessels) have been observed in other cases of toxic myocardial alterations (i.e. ethanol intoxication, injection of pharmacological agents, etc.), it can be assumed that it is a standard protective reaction of the altered heart to the penetration of toxic agents from the blood into the myocardial tissue.  相似文献   
8.
9.
10.
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