全文获取类型
收费全文 | 2358篇 |
免费 | 184篇 |
国内免费 | 196篇 |
专业分类
2738篇 |
出版年
2023年 | 49篇 |
2022年 | 55篇 |
2021年 | 44篇 |
2020年 | 50篇 |
2019年 | 67篇 |
2018年 | 60篇 |
2017年 | 59篇 |
2016年 | 70篇 |
2015年 | 55篇 |
2014年 | 92篇 |
2013年 | 140篇 |
2012年 | 66篇 |
2011年 | 106篇 |
2010年 | 84篇 |
2009年 | 104篇 |
2008年 | 127篇 |
2007年 | 120篇 |
2006年 | 119篇 |
2005年 | 102篇 |
2004年 | 80篇 |
2003年 | 77篇 |
2002年 | 82篇 |
2001年 | 60篇 |
2000年 | 68篇 |
1999年 | 54篇 |
1998年 | 43篇 |
1997年 | 37篇 |
1996年 | 36篇 |
1995年 | 29篇 |
1994年 | 25篇 |
1993年 | 39篇 |
1992年 | 35篇 |
1991年 | 41篇 |
1990年 | 47篇 |
1989年 | 35篇 |
1988年 | 36篇 |
1987年 | 35篇 |
1986年 | 38篇 |
1985年 | 37篇 |
1984年 | 47篇 |
1983年 | 19篇 |
1982年 | 29篇 |
1981年 | 26篇 |
1980年 | 27篇 |
1979年 | 25篇 |
1978年 | 11篇 |
1976年 | 8篇 |
1974年 | 8篇 |
1973年 | 8篇 |
1972年 | 9篇 |
排序方式: 共有2738条查询结果,搜索用时 0 毫秒
41.
42.
Bayesian analyses for a multiple capture-recapture model 总被引:3,自引:0,他引:3
43.
44.
45.
46.
On variance estimation in nonparametric regression 总被引:8,自引:0,他引:8
47.
48.
Mg2+ restores membrane potential in rat liver mitochondria deenergized by Ca2+ and phosphate movements 总被引:1,自引:0,他引:1
Cellular ornithine biosynthesis could be expected to play a significant role in putrescine formation and hence in growth. Two enzymes are involved in ornithine biosynthesis: arginase and transamidinase. These enzyme activities were studied in two human melanoma cell lines differing in their Km of diamine oxidase for putrescine and in their tumorigenicity in nude mice. Arginase activity accounts for the majority of ornithine formed in the highly tumorigenic cell line, while the majority of ornithine is derived from transamidinase action in the poorly tumorigenic cell line, with concomitant formation of methyl guanidine, a potent inhibitor of diamine oxidase. 相似文献
49.
Hajime Tokuda Tsutomu Unemoto 《Biochemical and biophysical research communications》1981,102(1):265-271
The membrane potential generated at pH 8.5 by K+-depleted and Na+-loaded is not collapsed by proton conductors which, instead, induce the accumulation of protons in equilibrium with the membrane potential. The generation of such a membrane potential and the accumulation of protons are specific to Na+-loaded cells at alkaline pH and are dependent on respiration. Extrusion of Na+ at pH 8.5 occurs in the presence of proton conductors unless respiration is inhibited while it is abolished by proton conductors at acidic pH. The uptake of α-aminoisobutyric acid, which is driven by the Na+-electrochemical gradient, is observed even in the presence of proton conductors at pH 8.5 but not at acidic pH. We conclude that a respiration-dependent primary electrogenic Na+ extrusion system is functioning at alkaline pH to generate the proton conductor-insensitive membrane potential and Na+ chemical gradient. 相似文献
50.
Sumiko Narise 《Biochemical genetics》1979,17(5-6):433-444
Two allozymes (MDHf and MDHs) of cytoplasmic malate dehydrogenase of Drosophila virilis were partially purified and their biochemical properties were compared. MDHf has a pH optimum of 9.75 and MDHs one of 9.25 for malate oxidation. Optimal pH for oxaloacetate reduction is 6.75 and 8.0 for MDHf and MDHs, respectively. The Km value for oxaloacetate of MDHs is approximately twice as that of MDHf. No differences were found with respect to thermostability and Km's for malate, NAD+, or NADH. These results are discussed in terms of the physiological role of cytoplasmic malate dehydrogenase of D. virilis.This work was supported in part by grants from the Ministry of Education, Japan, Nos. 134050 and 154205. 相似文献