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   895936篇
  免费   85962篇
  国内免费   315篇
  2018年   13513篇
  2017年   12881篇
  2016年   15346篇
  2015年   16386篇
  2014年   18900篇
  2013年   26979篇
  2012年   31849篇
  2011年   35246篇
  2010年   24556篇
  2009年   22559篇
  2008年   30795篇
  2007年   32594篇
  2006年   26212篇
  2005年   25295篇
  2004年   24931篇
  2003年   24043篇
  2002年   23438篇
  2001年   35966篇
  2000年   35473篇
  1999年   28460篇
  1998年   10632篇
  1997年   10625篇
  1996年   10219篇
  1995年   9404篇
  1994年   9050篇
  1993年   9057篇
  1992年   22943篇
  1991年   22527篇
  1990年   21934篇
  1989年   21436篇
  1988年   19569篇
  1987年   18840篇
  1986年   17594篇
  1985年   17504篇
  1984年   14423篇
  1983年   12631篇
  1982年   9607篇
  1981年   8686篇
  1980年   8084篇
  1979年   13470篇
  1978年   10587篇
  1977年   9585篇
  1976年   9155篇
  1975年   10296篇
  1974年   10977篇
  1973年   10820篇
  1972年   10365篇
  1971年   9255篇
  1970年   7829篇
  1969年   7759篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
192.
Binomial parameters of transmitter secretion were calculated on the basis of analysis of synaptic potentials in the frog sartorius muscle. Negative values of the parameter p were found in some synapses. This happened most often in low Ca2+ concentrations and with low amplitude of miniature end-plate potentials. The results were interpreted in terms of a model assuming spatial heterogeneity of probability of transmitter quantum release at different release points. Simulation of transmitter secretion by computer showed that the appearance of negative values of the parameter p and incorrect estimates of n experimentally are connected with the form of distribution of probability of transmitter quantum release in the synapse and with the amplitude of miniature potentials.S. V. Kurashov Kazan' Medical Institute, Ministry of Health of the RSFSR. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 182–189, March–April, 1984.  相似文献   
193.
194.
The neutrophil-stimulating properties of 38 S. aureus strains and 32 S. epidermidis strains were studied in the reaction of luminol-mediated chemiluminescence. All S. aureus strains and 29 S. epidermidis strains were found to possess neutrophil-stimulating activity, the mean activity index for S. aureus being significantly higher. The stimulating activity of the strains varied within a wide range (the variation coefficient was 120.0 +/- 21.9%) and did not correlate with the content of protein A in bacterial cells and the degree of their hydrophoby. The opsonization of staphylococci with normal human serum enhanced the neutrophil reaction 1.5- to 100-fold and simultaneously leveled out the chemiluminescence indices in experiments with different strains (the variation coefficient was 8.0 +/- 1.5%). The nature of the neutrophil-stimulating effect of staphylococci and its relationship to the exploratory reactions of phagocytes are discussed.  相似文献   
195.
Cryptococcosis is an often fatal opportunistic fungal infection. Despite efforts to elucidate the role of immunity in host defense against the disease, much remains to be learned. The purpose of this brief review is to provide the reader with an overview of the history of research concerned with host immunity in cryptococcosis. Both humoral and cell-mediated studies are included. An effort has been made to present the reader with a comprehensive list of references in the hope of encouraging additional reading and research in this important area.  相似文献   
196.
Heterozygote advantage in Tay-Sachs carriers?   总被引:4,自引:1,他引:3       下载免费PDF全文
Chi-square analyses of new data as well as data previously reported by Myrianthopoulos have shown that grandparents of Tay-Sachs carriers die from proportionally the same causes as grandparents of noncarriers. It is unlikely that there is any advantage to being a Tay-Sachs carrier insofar as resistance to tuberculosis is concerned. Our results are further evidence to support Fraikor's claim that the high carrier frequency of the allele in Ashkenazi Jews is probably caused by a combination of founder effect, genetic drift, and differential immigration patterns.  相似文献   
197.
198.
199.
200.
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