全文获取类型
收费全文 | 3289篇 |
免费 | 376篇 |
出版年
2021年 | 45篇 |
2019年 | 26篇 |
2018年 | 31篇 |
2016年 | 66篇 |
2015年 | 92篇 |
2014年 | 115篇 |
2013年 | 120篇 |
2012年 | 156篇 |
2011年 | 146篇 |
2010年 | 85篇 |
2009年 | 89篇 |
2008年 | 121篇 |
2007年 | 129篇 |
2006年 | 108篇 |
2005年 | 107篇 |
2004年 | 108篇 |
2003年 | 112篇 |
2002年 | 110篇 |
2001年 | 96篇 |
2000年 | 99篇 |
1999年 | 77篇 |
1998年 | 49篇 |
1997年 | 28篇 |
1996年 | 26篇 |
1995年 | 33篇 |
1994年 | 34篇 |
1993年 | 44篇 |
1992年 | 80篇 |
1991年 | 69篇 |
1990年 | 67篇 |
1989年 | 67篇 |
1988年 | 67篇 |
1987年 | 61篇 |
1986年 | 40篇 |
1985年 | 48篇 |
1984年 | 63篇 |
1983年 | 48篇 |
1982年 | 34篇 |
1981年 | 30篇 |
1980年 | 44篇 |
1979年 | 43篇 |
1978年 | 45篇 |
1977年 | 40篇 |
1976年 | 49篇 |
1975年 | 43篇 |
1974年 | 38篇 |
1973年 | 45篇 |
1972年 | 30篇 |
1970年 | 23篇 |
1969年 | 26篇 |
排序方式: 共有3665条查询结果,搜索用时 31 毫秒
61.
Molecular basis of the action of interferon 总被引:15,自引:0,他引:15
62.
Natural Antibody in Mammalian Serum Reacting with an Antigen in Some Leptospires 总被引:3,自引:0,他引:3 下载免费PDF全文
Serum from normal mammals agglutinated and immobilized nonpathogenic Leptospira biflexa and agglutinated avirulent lines of pathogenic serotypes L. icterohaemorrhagiae and L. zanoni. Virulent lines of L. icterohaemorrhagiae and L. zanoni were not affected, nor were any of three strains of L. pomona, one of which was avirulent. The active principle in serum was a beta-macroglobulin which was heat-labile and reduced by 2-mercaptoethanol, and acted in conjunction with complement and lysozyme; it was absorbable from serum by Formalin-treated susceptible leptospires. The Formalin-stable receptor antigen, named "Z antigen," is associated with virulence rather than pathogenicity, but may not be a determinant of virulence. 相似文献
63.
Branched-chain sphingosines from Tetrahymena pyriformis 总被引:1,自引:0,他引:1
64.
65.
The uptake of orthophosphate (32P) by excised corn roots, Zea mays L. was studied using roots grown on 0.2 mm CaSO4. Nine concentrations of KH2PO4 from 1 to 256 μm were used at temperatures of 20°, 30°, and 40°. Enzyme kinetic analysis was applied to the data obtained. Two apparent mechanisms (sites) of phosphate uptake were observed, 1 dominating at high P concentrations and 1 at low P concentrations. A Km of 1.36 × 10−4 and a Vmax of 177 × 10−9 moles per gram of roots per hour at 30° was calculated for the mechanism dominating at high P concentrations. Similar calculations gave a Km of 6.09 × 10−6 and a Vmax of 162 × 10−9 moles per gram of roots per hour at 30° for the mechanism dominating at low P concentrations. The Q10 for both mechanisms was approximately 2. Calculation of thermodynamic values from the data gave ΔF of − 5200 cal, ΔH of − 950 to − 1400 cal, and a enthalpy of activation (A) of 10,300 to 13,800 cal per mole for the mechanism dominating at high P concentrations. Similar calculations from the data for the mechanism dominating at low P concentrations gave a ΔF of − 7300 cal, ΔH of − 10,700 to − 8200 cal, and a A of 9300 to 18,900 cal per mole. If the dual mechanism interpretation of this kind of data adequately describes this system, then both mechanisms of P absorption by corn roots involve chemical reactions. 相似文献
66.
67.
68.
69.
70.