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   730870篇
  免费   70522篇
  国内免费   439篇
  2018年   11322篇
  2017年   10981篇
  2016年   12103篇
  2015年   11292篇
  2014年   13671篇
  2013年   19756篇
  2012年   23752篇
  2011年   27841篇
  2010年   19509篇
  2009年   17986篇
  2008年   24209篇
  2007年   26083篇
  2006年   19775篇
  2005年   19377篇
  2004年   19195篇
  2003年   18680篇
  2002年   18103篇
  2001年   34411篇
  2000年   34292篇
  1999年   26540篇
  1998年   8280篇
  1997年   8736篇
  1996年   8072篇
  1995年   7427篇
  1994年   7156篇
  1993年   7107篇
  1992年   20864篇
  1991年   20274篇
  1990年   19623篇
  1989年   19288篇
  1988年   17633篇
  1987年   16484篇
  1986年   15277篇
  1985年   15204篇
  1984年   12384篇
  1983年   10372篇
  1982年   7553篇
  1981年   6690篇
  1980年   6424篇
  1979年   11464篇
  1978年   8775篇
  1977年   8067篇
  1976年   7478篇
  1975年   8469篇
  1974年   9182篇
  1973年   8965篇
  1972年   8608篇
  1971年   7885篇
  1970年   6460篇
  1969年   6190篇
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
991.
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   
992.
A method is proposed for assessing the biocidal efficacy of water-dispersed nanoparticles of silver. It is based on negative chemotaxis of the plasmodia of the slime mold Physarum polycephalum. Biocidal and repellent effects were compared for silver nanoparticles, Ag+ ions, and AOT in solution and in the agar gel. In such characteristics as increasing the period of auto-oscillations of contractile activity, decreasing the area of spreading on substrate, and substrate preference in spatial tests, silver nanoparticles proved to be substantially more effective than Ag+ and AOT. The lethal concentrations of the nanoparticles were close to those found earlier for bacteria and viruses. The chemotactic tests allow quantitative assessment of the biological reaction and monitoring its dynamics; in resolution, they are superior to the tests based on the lethal action of biocidal agents.  相似文献   
993.
994.
995.
996.
997.
V A Shuklinov 《Tsitologiia》1985,27(3):268-275
The paper reports reasons for a possibility of tumour regression due to selection of low-malignant and differentiating clones. Experimental evidence is provided supporting this view.  相似文献   
998.
Mitochondrial DNA variation was examined in one of the southem most populations of domestic reindeer, inhabiting Tyva Republic (Tuva). In Tuvinian population sequence polymorphism of the mitochondrial DNA D-loop region was demonstrated. In a sample of 29 individuals 7 mitotypes were distinguished, pointing to the preservation of rather high level of genetic diversity in this population.  相似文献   
999.
The effects of biological treatments with PlantShield®, Prestop®, Quadra 136, RootShield®, and S33 (Rhodosporidium diobovatum) and chemical treatment with Decree® applied as a preventive or curative sprays on stem canker caused by Botrytis cinerea on tomato plants grown in sawdust were studied under near-commercial greenhouse conditions. Prestop® and Decree®, applied as preventive or curative sprays, PlantShield® applied as curative spray, and S33 and Q-136 applied as preventive or preventive plus one spray to wounded surface provided season-long protection from B. cinerea stem canker. These treatments also increased fruit yield and decreased the number of dead plants compared with the inoculated control.  相似文献   
1000.
Fossil plants of the Chingandzha flora were studied from volcanogenic sediments of the Chingandzha and Rond formations on the northern coast of the Sea of Okhotsk. It was concluded that all platanaceous leaves earlier described in this flora as different taxa belong to one highly variable species, Pseudoprotophyllum cordatum Samyl. emend. Shczepetov et Golovneva.  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