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   19296篇
  免费   1558篇
  国内免费   27篇
  20881篇
  2023年   157篇
  2022年   141篇
  2021年   322篇
  2020年   266篇
  2019年   259篇
  2018年   562篇
  2017年   521篇
  2016年   544篇
  2015年   540篇
  2014年   670篇
  2013年   1030篇
  2012年   1505篇
  2011年   1590篇
  2010年   806篇
  2009年   636篇
  2008年   1290篇
  2007年   1331篇
  2006年   1246篇
  2005年   1133篇
  2004年   1100篇
  2003年   1025篇
  2002年   900篇
  2001年   256篇
  2000年   331篇
  1999年   229篇
  1998年   147篇
  1997年   116篇
  1996年   95篇
  1995年   131篇
  1994年   116篇
  1993年   89篇
  1992年   138篇
  1991年   120篇
  1990年   107篇
  1989年   94篇
  1988年   92篇
  1987年   79篇
  1986年   56篇
  1985年   69篇
  1984年   80篇
  1983年   69篇
  1982年   78篇
  1981年   80篇
  1980年   67篇
  1979年   63篇
  1978年   67篇
  1977年   55篇
  1976年   55篇
  1975年   51篇
  1974年   53篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
63.
Study of the effect of phenformin on the blood glucose level in normal subjects before and during 70 hours of starvation showed a statistically significant hypoglycaemic effect after 40 hours of starvation. This effect was not due to increased glucose utilization.Another finding in this study was a statistically significant decrease in total urinary nitrogen excretion during starvation in subjects given phenformin. These findings show that the hypoglycaemic effect of phenformin in starved normal subjects is due to inhibition of gluconeogenesis.  相似文献   
64.
Exeised roots ofSolanum laciniatum Ait. grown in vitro in a liquid medium will form the typical rich white callus with a high water content. Its formation is made possible by the presence of 2,4-dichlorophenoxyacetic acid and niyo-inositol in the nutrient medium. Choline, ascorbic acid, riboflavin, calcium pantothenate and biotin are inactive. A mixture of thiamine, pyridoxine and nicotinic acid will induce only slight proliferation.  相似文献   
65.
Summary Eight newSalmonella types are described.S. houten, 43; Z4, Z23 :−, was isolated from a frog,S.tuindorp, 43: Z4, Z32: −,S. vleuten, 44: fg: −,S.zeist, 18: Z10: Z6, andS.soesterberg. 21: Z4, Z23: −, were isolated from lizards. S. kralingen (8), 20: y: Z6, was isolated from peanuts andS. assen, 21: a: −, was isolated from a swine. All these strains were isolated in the Netherlands. S.mim, 13, 22: a: 1,6, was isolated from a rat in Ghana.  相似文献   
66.
Various possibilities of usingSörensen's coefficient of floristic similarity in plant sociology are summarized. A new formula (11), derived from that bySörensen and based on constancy values, is suggested in order to calculate the mean floristic similarity within a set of relevés.  相似文献   
67.
Various possibilities of usingSörensen’s coefficient of floristic similarity in plant sociology are summarized. A new formula (11). derived from that bySörensen and based on constancy values, is suggested in order to calculate the mean floristic similarity within a set of relevés.  相似文献   
68.
69.
Out of 12,472 strains ofSalmonella isolated in the Netherlands in 1962, 1365, or 10.94%, were found to be resistant to tetracycline or chloramphenicol or to both. Compared with the findings of the preceding years (1958/59:2.08%, 1960:1.29%, 1961:3.96%) this is a considerable increase. Of these 1365 strains, 1285, or 94.1%, were resistant to tetracycline and 46, or 3.4%, were resistant to chloramphenicol. The remaining 34 strains, or 2.5%, were resistant to both drugs.Among allSalmonella strains isolated in 1962, 5517 belonged to the speciesS. typhi murium. Of these, 1203 or 21.8%, were resistant to tetracycline. The resistance rates of strains originating from human patients, calves, pigs, other animals and other materials were 24.4%, 37.1%, 15.0%, 8.0% and 5.7% respectively.Factors which may possibly have contributed to the greatly increased frequency of drug resistance inS. typhi murium are: (1) the rapid spread of the use of tetracycline for therapeutic, prophylactic and nutritive purposes, and (2) the possibility of an episome-mediated transfer of drug resistance from relatively harmless intestinal bacteria, such asE. coli, toS. typhi murium.  相似文献   
70.
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