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   533861篇
  免费   59687篇
  国内免费   359篇
  593907篇
  2018年   5251篇
  2017年   5110篇
  2016年   6980篇
  2015年   8831篇
  2014年   10560篇
  2013年   15326篇
  2012年   17046篇
  2011年   17434篇
  2010年   11742篇
  2009年   10781篇
  2008年   15216篇
  2007年   15774篇
  2006年   14722篇
  2005年   14104篇
  2004年   13980篇
  2003年   13324篇
  2002年   12838篇
  2001年   28368篇
  2000年   28224篇
  1999年   21992篇
  1998年   6737篇
  1997年   7313篇
  1996年   6741篇
  1995年   6217篇
  1994年   5985篇
  1993年   5959篇
  1992年   17047篇
  1991年   16293篇
  1990年   15710篇
  1989年   15215篇
  1988年   13930篇
  1987年   12943篇
  1986年   12045篇
  1985年   11819篇
  1984年   9665篇
  1983年   8085篇
  1982年   5996篇
  1981年   5374篇
  1980年   5097篇
  1979年   8942篇
  1978年   6812篇
  1977年   6273篇
  1976年   5646篇
  1975年   6241篇
  1974年   6762篇
  1973年   6545篇
  1972年   5982篇
  1971年   5429篇
  1970年   4684篇
  1969年   4400篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
The effect of one massive dose of cytoxan (150 mg/kg), as an alkylating agent, on the morphology of sarcoma 180 cells was followed after 1, 3, 6, 12, 24, 48, 96, 120, and 168 h. After 1 h the cells of treated tumour showed clumping and a decrease in their size. In addition, statistical analysis manifested significant decrease in all phases of mitotic figures. All mitotic figures were completely stopped after 3 h from cytoxan treatment. After 6 and 12 h from cytoxan treatment the hyaline degenerations became more marked in the treated tumour tissue. Chromosomal bridge formation, nuclei aberrations and polynuclear cells were more prominent in 24, 48, and 96 h from cytoxan treatment. Increase in the nuclear size and hyaline degeneration were observed in treated section of 120 and 168 h.  相似文献   
952.
The differentiation of spermatids in the marmoset (Callithrix jacchus, n = 9) testis is described here at the light-microscopic level employing serial semithin sections. The definition of 8 different phases of spermiogenesis, i.e. the formation of spermatids, is based upon the changes in the development of nucleus, acrosome and flagellum.  相似文献   
953.
A rapid, direct method for screening single cell-derived colonies or foci is described. The method allows the screening of a large number of colonies or foci by nitrocellulose filter hybridization using DNA probes. This technique simplifies current screening procedures and is a reliable, rapid, and sensitive method for the selection of cell clones containing a desired transfected gene.  相似文献   
954.
955.
956.
957.
Cimetidine is widely prescribed for the treatment of peptic ulcer disease and has recently been shown to inhibit the metabolism of warfarin, antipyrine and diazepam. To further examine this phenomenon we investigated the effect of various doses of cimetidine and other related drugs on 14C-aminopyrine, 14C-phenacetin and 14C-caffeine breath tests. Cimetidine caused a dose-related inhibition of the metabolism of aminopyrine and caffeine but had no effect on the phenacetin breath test. Metiamide, H1-antihistamines, phenothiazines and local anesthetics also inhibited the aminopyrine breath test. Cyproheptadine had no effect on either phenacetin or caffeine elimination. This study demonstrates a complex drug-drug interaction which may have widespread clinical implications.  相似文献   
958.
959.
ELISA is used for detecting the soluble staphylococcal antigen in patients with purulent septic infections. The optimum conditions for the assay have been established: the dose of staphylococcal gamma globulin for plate sensitization should be 5.0-10.0 micrograms/ml, the pH of the buffer solution 9.6-10.0, the time and temperature of incubation 18-20 hours at 4 degrees C or 5 hours at 37 degrees C. The possibility of using plates manufactured in the USSR has been shown. The sensitivity of the above diagnostic test system is 0.005 microgram/ml.  相似文献   
960.
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