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   137970篇
  免费   11744篇
  国内免费   44篇
  149758篇
  2021年   1493篇
  2019年   1257篇
  2018年   1985篇
  2017年   1831篇
  2016年   2656篇
  2015年   3399篇
  2014年   3929篇
  2013年   5274篇
  2012年   6240篇
  2011年   6806篇
  2010年   4608篇
  2009年   4066篇
  2008年   5270篇
  2007年   5205篇
  2006年   4910篇
  2005年   4517篇
  2004年   4519篇
  2003年   4188篇
  2002年   3989篇
  2001年   5028篇
  2000年   4747篇
  1999年   3826篇
  1998年   1468篇
  1997年   1381篇
  1996年   1242篇
  1995年   1173篇
  1994年   1131篇
  1993年   1130篇
  1992年   2847篇
  1991年   2799篇
  1990年   2788篇
  1989年   2555篇
  1988年   2418篇
  1987年   2309篇
  1986年   2082篇
  1985年   2111篇
  1984年   1792篇
  1983年   1553篇
  1982年   1182篇
  1981年   1101篇
  1979年   1647篇
  1978年   1306篇
  1977年   1196篇
  1976年   1153篇
  1975年   1350篇
  1974年   1415篇
  1973年   1494篇
  1972年   1321篇
  1971年   1159篇
  1969年   1070篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Strains of paramyxovirus type 1 (PMV-1) have been isolated from diseased racing pigeons in Sweden. One of these isolates was selected for studies of the pathogenicity and contagiousness in chickens. The same isolate was previously found to have a high intravenous pathogenicity index (IVPI) in 6 weeks old chickens. In three experiments it was found that the PMV-1 isolate was very pathogenic for 1 week old chickens but not pathogenic for 120 day old pullets inoculated intranasally and ocularly. Symptoms in the young chickens were similar to those seen in the neurotropic form of Newcastle disease. The mortality was high and the incubation period 5–11 days. The disease easily spread to young chickens kept in contact with diseased birds. The microscopic examination revealed an interstitial nonpurulent pneumonia and a nonpurulent encephalitis in the young chickens. In the pullets the only finding was a mild encephalitis. PMV-1 was recovered from all young chickens but not from the pullets. Both the chickens and the inoculated pullets developed antibodies to PMV-1.  相似文献   
102.
103.
104.
105.
The perfusion procedure described in this paper produces high quality impregnation of pig visual and somatosensory cortical neurons with a Golgi-Cox solution. Starting within 30 min after death, pig heads were perfused with a fixative solution composed of a mixture (v/v) of liquid phenol, 5%; formalin, 14%; ethylene glycol, 25%; methanol, 28%; and water, 28% for two periods of 4 hr each. After perfusion, the heads were chilled for at least 18 hr. The entire brain was removed from the skull and then placed in 10% buffered formalin, where it remained for at least 10 days before taking the blocks that were to be immersed in the Golgi-Cox solution. Three weeks spent in the Golgi-Cox solution typically produced uniform neuron impregnation. The tissue blocks were then embedded in celloidin and sectioned at 120 micron. This procedure avoids the following difficulties: Golgi-Cox methods that produced excellent results with rodent or primate tissue were unsuccessful with pig tissue, placing fresh tissue in Golgi-Cox solution resulted in incomplete neuron impregnation, and immersion fixation in 10% buffered formalin without perfusion resulted in excessive staining of glia.  相似文献   
106.
107.
The paper is concerned with analysis of the results of intraoperative phlebotesticulography, performed in 50 patients with varicocele of degree I-II during Ivanissevich's operation. The effect of surgical intervention was shown to depend upon the quality of ligation of the testicular vein, some parts of which are anastomosed between themselves. The localization of this anastomosis is revealed by means of intraoperative phlebotesticulography, which permits increasing the results of surgical treatment and predicting a course of a postoperative period.  相似文献   
108.
109.
110.
Neurotoxic Esterase in Human Nervous Tissue   总被引:1,自引:1,他引:0  
  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