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   81785篇
  免费   4694篇
  国内免费   9篇
  86488篇
  2021年   1006篇
  2020年   905篇
  2019年   919篇
  2018年   2200篇
  2017年   1928篇
  2016年   2617篇
  2015年   3455篇
  2014年   3562篇
  2013年   4694篇
  2012年   5496篇
  2011年   4827篇
  2010年   3153篇
  2009年   2375篇
  2008年   3860篇
  2007年   3648篇
  2006年   3620篇
  2005年   3023篇
  2004年   3037篇
  2003年   2709篇
  2002年   2475篇
  2001年   2055篇
  2000年   1918篇
  1999年   1478篇
  1998年   669篇
  1997年   472篇
  1996年   531篇
  1995年   468篇
  1992年   929篇
  1991年   845篇
  1990年   826篇
  1989年   903篇
  1988年   740篇
  1987年   753篇
  1986年   688篇
  1985年   755篇
  1984年   621篇
  1983年   548篇
  1979年   670篇
  1978年   489篇
  1977年   490篇
  1975年   584篇
  1974年   624篇
  1973年   595篇
  1972年   548篇
  1971年   491篇
  1970年   536篇
  1969年   610篇
  1968年   574篇
  1967年   479篇
  1966年   466篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
The effect of single intraperitoneal 1 g.kg-1 doses of a solution of 20 amino acids (AA) on food intake was investigated in 20 piglets examined repeatedly between 2 and 26 days of age. The animals were reared individually from day 1 after birth in cages and bottle-fed a liquid diet nine times per day at two-hour intervals from 6 to 22 h. Although amino acid administration did not significantly affect plasma concentrations of total free AA throughout the experiment (as measured just before and 2 and 5 h after AA administration in blood withdrawn from the external jugular vein) it did produce a downward trend in food intake of piglets at 9-10 d of age. In older animals, the depressive effect on food intake was significantly greater and lasted longer. It is suggested that the aminostatic component of food intake regulation in piglets does not begin to operate until the weaning period.  相似文献   
152.
153.
After a short irradiation at 366 nm with 200 lx, the intensity of conidiation ofTrichoderma viride colonies grown in the dark increased for the first 10 s proportionally with time. The increase slowed down after 10 s—6 min of exposure and after 10–60 min of irradiation the conidiation intensity began to decrease. When photo-induced by daylight, the conidiation started at a high rate after 25 h and persisted even after 48 h. The conidiation had no circadian character and its periodicity depended on the periodicity of photo-induction. Its intensity was also influenced by the carbon sources used, a maximum being reached with glucose (1–2 %). Higher glucose concentrations inhibited conidiation but had no influence on growth of colonies.  相似文献   
154.
R Adány  L Muszbek 《Histochemistry》1989,91(2):169-174
As spontaneous abortion is a frequent finding in females with Factor XIII (FXIII) deficiency it has been presumed that this clotting factor is essential to normal pregnancy. FXIII subunit a (FXIII A) has been demonstrated in the homogenate of human uterus, but no information on its cellular distribution has been published, so far. In the present study first FXIII A was detected in paraformaldehyde-fixed, paraffin-embedded sections of human uterus by immunoperoxidase technique. Cells containing FXIII A were localized between collagen fibrils stained by Picrosirius Red F3B in the connective tissue. To characterize them the immunofluorescent detection of FXIII A was combined by the visualization of different marker antigens of monocytes and macrophages recognized by Leu-M3, RFD7, anti-HLA-DR and DAKO-anti-macrophage monoclonal antibodies on frozen sections. The coexpression of FXIII A with monocyte and macrophage differentiation marker antigens clearly proves that cells containing FXIII A in the uterus are monocyte-derived tissue macrophages. The results well agree with our previous findings demonstrating FXIII A in human monocytes and different types of macrophages. On the basis of these results, the presence of FXIII A does not seem to be a specificity of the uterus but a characteristic of monocyte/macrophage cell line including tissue macrophages, in general.  相似文献   
155.
156.
The formation of two extracellular enzymes (α-amylase and a proteinase) ofB. subtilis was investigated in batch and continuous cultures. Differences were observed in the production of both enzymes in batch culture when studied in flasks and in a fermentor. The values of proteinase activity from continuous cultivation never reached those obtained during batch cultivation. The optimal dilution rate for proteinase synthesis was 0.1 – 0.2/h. The optimal dilution rate for the production of α-amylase was 0.2 –0.3/h.  相似文献   
157.
158.
159.
160.
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