全文获取类型
收费全文 | 610100篇 |
免费 | 67229篇 |
国内免费 | 462篇 |
专业分类
677791篇 |
出版年
2016年 | 6887篇 |
2015年 | 9347篇 |
2014年 | 10857篇 |
2013年 | 15945篇 |
2012年 | 17474篇 |
2011年 | 17820篇 |
2010年 | 12224篇 |
2009年 | 11169篇 |
2008年 | 16130篇 |
2007年 | 16361篇 |
2006年 | 15614篇 |
2005年 | 15169篇 |
2004年 | 14895篇 |
2003年 | 14697篇 |
2002年 | 14139篇 |
2001年 | 24585篇 |
2000年 | 24481篇 |
1999年 | 19745篇 |
1998年 | 7405篇 |
1997年 | 7688篇 |
1996年 | 7492篇 |
1995年 | 6825篇 |
1994年 | 6774篇 |
1993年 | 6792篇 |
1992年 | 16796篇 |
1991年 | 16597篇 |
1990年 | 16153篇 |
1989年 | 15871篇 |
1988年 | 14740篇 |
1987年 | 14366篇 |
1986年 | 13249篇 |
1985年 | 13571篇 |
1984年 | 11296篇 |
1983年 | 9867篇 |
1982年 | 7745篇 |
1981年 | 7344篇 |
1980年 | 6740篇 |
1979年 | 11320篇 |
1978年 | 8821篇 |
1977年 | 8466篇 |
1976年 | 7963篇 |
1975年 | 8807篇 |
1974年 | 9612篇 |
1973年 | 9525篇 |
1972年 | 8740篇 |
1971年 | 7985篇 |
1970年 | 7078篇 |
1969年 | 7035篇 |
1968年 | 6398篇 |
1967年 | 5557篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
31.
32.
A A Sukhopiatkina O S Bat A V Levitskaia V G Potapova 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1985,(4):80-81
The study of the specific epidemiological and clinical features of Q fever revealed the existence of an active focus of infection among humans due to their contacts with agricultural animals in one of the districts of the region. The focus was manifested by group morbidity among the cattle-tending personnel of a dairy farm. The source of this infection was cattle. The infection was transferred mainly through the air. The disease took a moderately severe course. The study of the rickettsial contamination of humans, animals and ticks suggested the presence of the active epidemic process and made it possible to work out concrete antiepidemic measures. 相似文献
33.
F F Dias M K Shaikh Y B Bhatt D C Modi V R Subramanyam 《The Journal of applied bacteriology》1986,60(4):271-275
Mutants of Bacillus amyloliquefaciens resistant to at least 10 micrograms/ml of tunicamycin were isolated and shown to be pleiotropic. The mutants were more resistant to streptomycin, chloramphenicol, kanamycin and neomycin than was the parent strain but less resistant to penicillin G and tetracycline. They were more autolytic, presumably due to an altered cell wall. The mutants produced reduced levels of amylase, penicillinase and both metal and serine protease besides having an enhanced sporulation frequency and being more motile. 相似文献
34.
Proteins in the molecular weight range of 10 000–170 000 were separated by high performance gel permeation chromatography. Silica particles with 30 nm or 50 nm pores were derivatized with glycidoxy-propyltrimethoxysilane and used as support. The proteins were eluted with 50% formic acid. A protein fraction which induces endodermal and mesodermal tissues in amphibian gastrula ectoderm was purified by this method. 相似文献
35.
Transcriptive expression during sea urchin embryogenesis 总被引:2,自引:0,他引:2
36.
Subsequent to observations that pulmonary responses to antigen challenge are of different magnitudes in sensitized rats that are anesthetized with different drugs, we conducted studies to test whether the alterations in responses were due to changes in airway responsiveness to cholinergic or serotonergic challenge, opioid-receptor mediated events, or changes in mast cell mediator release. Immunoglobulin E-sensitized rats anesthetized with ketamine/urethan had larger changes in lung resistance and plasma histamine after pulmonary antigen challenge compared with rats anesthetized with fentanyl-droperidol. Blockade of opioid receptors with naloxone did not affect the responses. In unsensitized rats, airway responses to aerosolized methacholine were similar for the two anesthetics, indicating unchanged smooth muscle responsiveness; however, airway responses to intravenous serotonin were enhanced by ketamine and ablated by droperidol. We conclude that ketamine- and droperidol-induced alterations of pulmonary allergic responses are due to changes in sensitivity to serotonin and in mast cell mediator release. We speculate that mast cell mediator release may be modulated by a serotonin receptor-linked mechanism. 相似文献
37.
38.
39.
40.