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   836824篇
  免费   99373篇
  国内免费   336篇
  936533篇
  2016年   9197篇
  2015年   12709篇
  2014年   15044篇
  2013年   21880篇
  2012年   24355篇
  2011年   24557篇
  2010年   16350篇
  2009年   15311篇
  2008年   22009篇
  2007年   22823篇
  2006年   21607篇
  2005年   20788篇
  2004年   20612篇
  2003年   19854篇
  2002年   19299篇
  2001年   36043篇
  2000年   36666篇
  1999年   29401篇
  1998年   10750篇
  1997年   11327篇
  1996年   10900篇
  1995年   10240篇
  1994年   10286篇
  1993年   10172篇
  1992年   25448篇
  1991年   25022篇
  1990年   24671篇
  1989年   24231篇
  1988年   22326篇
  1987年   21482篇
  1986年   20048篇
  1985年   20293篇
  1984年   16891篇
  1983年   14848篇
  1982年   11436篇
  1981年   10521篇
  1980年   10014篇
  1979年   16665篇
  1978年   12986篇
  1977年   11845篇
  1976年   11339篇
  1975年   12455篇
  1974年   13053篇
  1973年   12854篇
  1972年   11999篇
  1971年   10549篇
  1970年   9265篇
  1969年   8700篇
  1968年   7956篇
  1967年   7017篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The study of the effect of gamma globulin introduced in different doses (0.5 and 0.25 ml/mg) in combination with Fermi rabies vaccine (observations on humans were made) and with cerebral rabies vaccine inactivated by UV irradiation (in animal experiments) demonstrated that the injection of the higher doses of gamma globulin resulted in lower geometrical mean of antibody titers. Therefore, in combined administration of rabies vaccine and gamma globulin for postexposure rabies prevention it is advisable to reduce the dose of gamma globulin by one-half.  相似文献   
992.
993.
994.
The pH, the osmolality and the urea and ammonia concentrations in blood, as well as the net urea and ammonia excretions, were studied in the amphibian Xenopus laevis exposed for several weeks to increased osmotic pressure (OP) of the ambient water, as a result of the addition of either NaCl or mannitol to the water. The pH and the ammonia concentration of the blood were independent of the variations of the ambient osmolarity. On the contrary, the blood osmolality and its urea concentration increased markedly when the ambient OP was augmented. The increase of ambient OP by NaCl addition to the medium augmented the urea net excretion and slightly decreased the ammonia excretion. When the increase of ambient OP resulted from the addition of mannitol in the water, excretions of urea and ammonia became negligible.  相似文献   
995.
996.
Phenotypic data on 203 Gram-negative non-fermentative bacteria of the Flavobacterium-Cytophaga group isolated from milk and butter were analyzed by numerical taxonomic techniques. Twenty reference strains including species of Flavobacterium, Cytophaga and strains of Pseudomonas paucimobilis were included in the study. Using the matching coefficient of Sokal & Michener with antibiotic susceptibility data included, 139 isolates were recovered in nine clusters. Six of these clusters were linked at or above the 85% S level while three were linked at or above the 79% S level. The largest cluster, representing 46.3% of the isolates, could be equated with Flavobacterium sp. Group IIb. Other clusters could be equated with Flavobacterium sp. L 16/1 (22.7% of isolates), F. balustinum (10.8% of isolates), F. breve (4.4%), F. multivorum (3.5%) and Cytophaga johnsonae (1.5%). The cluster resembling Flavobacterium sp. L 16/1 and a smaller unclassified cluster, were exceptional in being susceptible to the antibiotics cephalothin and penicillin G.  相似文献   
997.
Fractionation of human erythrocyte membrane proteins was performed using a modification of two-dimensional gel electrophoresis described by P. O'Farrel with isoelectric point plotted against molecular mass. All major erythrocyte proteins, including high molecular weight proteins, such as spectrin and band 3 protein, identified by one-dimensional sodium dodecyl sulfate gel electrophoresis, were visualized by silver staining of two-dimensional gels. All in all about 50 polypeptides were distinguished on two-dimensional electrophoretic patterns. Preliminary protein map was developed.  相似文献   
998.
999.
1000.
Abstract— The Nucleic acids were measured in developing retinae of normal (DBA) mice and those afflicted with an inherited degenerative disease (C3H). The content of RNA in normal and C3H retinae increased to a maximum at 5 days of postnatal age. Thereafter, that of C3H retinae declined to a value lower than the normal. The content of DNA in normal and C3H retinae was maximal at 10 and 5 days of postnatal age, respectively. By 20 days, it declined in both retinae to nearly adult values. The DNA/RNA ratio of normal adult retinae was about 3, while that of C3H adult retinae was nearly 1–5. It is proposed that the photoreceptor cells possess a smaller cytoplasmic volume and a larger DNA/RNA ratio than the cells of the inner retina. The loss of DNA in developing normal and C3H retinae appears to result from cellular death. It was calculated that approximately 1 million cells in normal and 6 million cells in C3H retinae disappear during development. Cellular death in C3H retinae may not be restricted to the photoreceptor population.  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