全文获取类型
收费全文 | 706340篇 |
免费 | 79375篇 |
国内免费 | 484篇 |
出版年
2016年 | 8682篇 |
2015年 | 11958篇 |
2014年 | 13897篇 |
2013年 | 19328篇 |
2012年 | 21978篇 |
2011年 | 22240篇 |
2010年 | 15112篇 |
2009年 | 13837篇 |
2008年 | 20114篇 |
2007年 | 20790篇 |
2006年 | 19629篇 |
2005年 | 19019篇 |
2004年 | 18772篇 |
2003年 | 18051篇 |
2002年 | 17619篇 |
2001年 | 27039篇 |
2000年 | 27198篇 |
1999年 | 21960篇 |
1998年 | 8342篇 |
1997年 | 8639篇 |
1996年 | 8230篇 |
1995年 | 7717篇 |
1994年 | 7625篇 |
1993年 | 7604篇 |
1992年 | 18656篇 |
1991年 | 18376篇 |
1990年 | 17938篇 |
1989年 | 17548篇 |
1988年 | 16655篇 |
1987年 | 16103篇 |
1986年 | 15082篇 |
1985年 | 15044篇 |
1984年 | 12683篇 |
1983年 | 11201篇 |
1982年 | 8817篇 |
1981年 | 8202篇 |
1980年 | 7659篇 |
1979年 | 12566篇 |
1978年 | 9967篇 |
1977年 | 9287篇 |
1976年 | 8880篇 |
1975年 | 9718篇 |
1974年 | 10724篇 |
1973年 | 10485篇 |
1972年 | 9812篇 |
1971年 | 8918篇 |
1970年 | 7830篇 |
1969年 | 7844篇 |
1968年 | 7362篇 |
1967年 | 6298篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
51.
52.
53.
54.
55.
56.
A. R. E. SINCLAIR 《African Journal of Ecology》1973,11(1):93-107
Censuses of buffalo and wildebeest in the Serengeti-Mara region have been carried out by various workers at intervals since 1958. The methods of these censuses, which normally employ a total count, are described and the errors inherent in such techniques are analysed in detail. After the appropriate corrections had been made the results showed that both populations have increased considerably over the years 1961–1971. 相似文献
57.
AAA ATPases form a functionally diverse superfamily of proteins. Most members form homo-hexameric ring complexes, are catalytically active only in the fully assembled state, and show co-operativity among the six subunits. The mutual dependence among the subunits is clearly evidenced by the fact that incorporation of mutated, inactive subunits can decrease the activity of the remaining wild type subunits. For the first time, we develop here models to describe this form of allostery, evaluate them in a simulation study, and test them on experimental data. We show that it is important to consider the assembly reactions in the kinetic model, and to define a formal inhibition scheme. We simulate three inhibition scenarios explicitly, and demonstrate that they result in differing outcomes. Finally, we deduce fitting formulas, and test them on real and simulated data. A non-competitive inhibition formula fitted experimental and simulated data best. To our knowledge, our study is the first one that derives and tests formal allosteric schemes to explain the inhibitory effects of mutant subunits on oligomeric enzymes. 相似文献
58.
59.
60.
Vinogradov Michael E.; Shushkina Elvira A.; Nezlin Nikolay P.; Arnautov Genrikh N. 《Journal of plankton research》1998,20(1):85-103
Zooplankton data collected during September 1995 in the NorthWest Atlantic at 4139'N, 4958'W (the location of the siteof the Titanic wreck) were analysed. The regioninvestigated was characterized by a very sharp frontal zonebetween the Gulf Stream and the main stream of the LabradorCurrent. The total plankton biomass in the water column wasvery high. The macroplankton biomass values below the 600 mlayer were significantly higher as compared with the similarvalues measured before in other productive boreal regions ofthe Atlantic and Pacific oceans. A lot of dead mesoplanktonanimals occurred in the deep layers. The reason was that thecold-water mesoplankton advected by the Labrador Current diedoff intensively within the deep layers of the frontal zone andwere used as a food resource by the macroplankton carnivoresand scavengers that were very abundant there. 相似文献