全文获取类型
收费全文 | 664731篇 |
免费 | 76433篇 |
国内免费 | 356篇 |
专业分类
741520篇 |
出版年
2016年 | 7606篇 |
2015年 | 10352篇 |
2014年 | 12176篇 |
2013年 | 17120篇 |
2012年 | 19286篇 |
2011年 | 19705篇 |
2010年 | 13529篇 |
2009年 | 12646篇 |
2008年 | 17988篇 |
2007年 | 18648篇 |
2006年 | 17551篇 |
2005年 | 17046篇 |
2004年 | 16874篇 |
2003年 | 16276篇 |
2002年 | 15865篇 |
2001年 | 26007篇 |
2000年 | 26118篇 |
1999年 | 21108篇 |
1998年 | 7967篇 |
1997年 | 8334篇 |
1996年 | 7928篇 |
1995年 | 7438篇 |
1994年 | 7343篇 |
1993年 | 7334篇 |
1992年 | 18126篇 |
1991年 | 17874篇 |
1990年 | 17483篇 |
1989年 | 17101篇 |
1988年 | 16267篇 |
1987年 | 15751篇 |
1986年 | 14718篇 |
1985年 | 14708篇 |
1984年 | 12384篇 |
1983年 | 10930篇 |
1982年 | 8548篇 |
1981年 | 7942篇 |
1980年 | 7465篇 |
1979年 | 12273篇 |
1978年 | 9720篇 |
1977年 | 9089篇 |
1976年 | 8718篇 |
1975年 | 9474篇 |
1974年 | 10501篇 |
1973年 | 10275篇 |
1972年 | 9611篇 |
1971年 | 8699篇 |
1970年 | 7666篇 |
1969年 | 7661篇 |
1968年 | 7146篇 |
1967年 | 6127篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Activity of phosphoenolpyruvate carboxylase of an anthracycline-producing streptomycete 总被引:1,自引:0,他引:1
During fermantation studies on the production of anthracycline antibiotics by Streptomyces C5, it was observed that among the intermediate metabolism enzymes tested, only phosphoenolpyruvate carboxylase (PEPCase; EC 4.1.1.31) increased significantly in specific activity during stationary phase. The specific activity of the Streptomyces C5 PEPCase increased ca. 3-fold during antibiotic production phase from the logarithmic phase levels. To characterize the regulation of the enzyme further, the Streptomyces C5 PEPCase was purified 150-fold from crude extracts. Acetyl-CoA and Mg2+ were shown to be required for PEPCase activity. The activity of the partially purified PEPCase was stimulated slightly by fructose 1,6-bisphosphate and AMP, and was inhibited severely by oxaloacetate, aspartate, malate, succinate, ATP, citrate, and CoASH. 相似文献
72.
Protein metal-binding sites. 总被引:2,自引:0,他引:2
Metal ions have a role in a variety of important functions in proteins including protein folding, assembly, stability, conformational change, and catalysis. The presence or absence of a given metal ion is crucial to the conformation or activity of over one third of all proteins. Recent developments have been made in the understanding and design of metal-binding sites in proteins, an important and rapidly advancing area of protein engineering. 相似文献
73.
V K Khugaeva E D Klimenko P N Aleksandrov G F Leskova M I Reutov 《Biulleten' eksperimental'no? biologii i meditsiny》1985,100(7):15-19
Experiments were made on rabbit fed an atherogenic diet (0.5 g/kg cholesterol) singly for 15 and 24 h and repeatedly for 3, 9 and 30 days. At early stages of lipid metabolism distress the interrelationship was established between blood rheological disorders and microcirculatory abnormalities. The dependence of the initial reaction of some rheological characteristics on their initial level was marked. 相似文献
74.
75.
E A Bardakhch'ian Iu G Kirichenko 《Biulleten' eksperimental'no? biologii i meditsiny》1986,102(7):97-100
Electron microscopy of the adrenal medulla and cortex during the intermediate period of endotoxin shock has revealed severe destructive changes in parenchymal cells. These changes are the reason for synthetic, secretory and trophic disturbances of glandular functions. Ultrastructural lesions indicate that stress exposure exceeds the adaptive capacity of cells, the majority of which are exhausted and killed. 相似文献
76.
77.
Synthesis of prenylquinones in chloroplasts 总被引:3,自引:0,他引:3
78.
M A Pass M W Goosem S Pollitt 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1985,82(2):457-461
The metabolism of the cholestatic triterpene acid reduced lantadene A has been studied in susceptible and resistant rats and in sheep which are susceptible to intoxication. Sheep and susceptible female rats produced a similar major metabolite and rats produced a second metabolite which was a glucuronide. These metabolites were also observed in extracts of bile canalicular membranes prepared from intoxicated rats. Resistant male and female rats produced a similar major metabolite which was different to those synthesized by susceptible animals. It is concluded that in rats and sheep there is a correlation between the type of metabolites produced in the liver and the susceptibility to intoxication by reduced lantadene A. 相似文献
79.
G. E. Tanyi 《Bulletin of mathematical biology》1982,44(4):501-535
The Thom gradient model of morphogenesis poses the followinga posteriori problem: “From the observed morphology of a given natural process (effect) determine the dynamics of the process (cause)”. In this paper we consider the classicala priori problem: “Given the cause (dynamics) determine the effect (resultant morphology)”.
We find that in biochemical processes the mechanisms for energy activation, energy-matter interaction and energy dissipation
determine the dynamics. Furthermore there exists basic energy mechanisms which drive the equilibrium states through the elementary
catastrophes of Thom. A comparison with current theories shows that our models describe open ecological food chains and their
dynamical systems generalize the equations of organisation posed by M. Eigen.
Work supported by a Research Associateship of the International Centre for Theoretical Physics, P.O.B. 586, Miramare, 34100
Trieste, Italy. 相似文献
80.