全文获取类型
收费全文 | 3806篇 |
免费 | 596篇 |
国内免费 | 2篇 |
出版年
2021年 | 50篇 |
2019年 | 39篇 |
2018年 | 47篇 |
2016年 | 59篇 |
2015年 | 108篇 |
2014年 | 116篇 |
2013年 | 138篇 |
2012年 | 179篇 |
2011年 | 182篇 |
2010年 | 142篇 |
2009年 | 107篇 |
2008年 | 155篇 |
2007年 | 149篇 |
2006年 | 131篇 |
2005年 | 128篇 |
2004年 | 132篇 |
2003年 | 115篇 |
2002年 | 138篇 |
2001年 | 121篇 |
2000年 | 113篇 |
1999年 | 99篇 |
1998年 | 54篇 |
1997年 | 43篇 |
1996年 | 49篇 |
1995年 | 43篇 |
1994年 | 50篇 |
1993年 | 42篇 |
1992年 | 87篇 |
1991年 | 92篇 |
1990年 | 76篇 |
1989年 | 81篇 |
1988年 | 97篇 |
1987年 | 75篇 |
1986年 | 71篇 |
1985年 | 57篇 |
1984年 | 52篇 |
1983年 | 54篇 |
1982年 | 38篇 |
1981年 | 54篇 |
1980年 | 43篇 |
1979年 | 62篇 |
1978年 | 47篇 |
1977年 | 44篇 |
1976年 | 40篇 |
1975年 | 38篇 |
1974年 | 61篇 |
1973年 | 60篇 |
1972年 | 39篇 |
1970年 | 36篇 |
1967年 | 39篇 |
排序方式: 共有4404条查询结果,搜索用时 31 毫秒
151.
152.
Roles for Protein Kinase C and Mitogen-Activated Protein Kinase in Nicotine-Induced Secretion from Bovine Adrenal Chromaffin Cells 总被引:3,自引:2,他引:1
Abstract: Both the Ca2+/phospholipid-dependent protein kinases (protein kinases C, PKCs) and mitogen-activated protein kinases (MAPKs) have been implicated as participants in the secretory response of bovine adrenomedullary chromaffin cells. To investigate a possible role for these kinases in exocytosis and the relationship of these kinases to one another, intact chromaffin cells were treated with agents that inhibited each of the kinases and analyzed for catecholamine release and MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK)/MAPK activation after stimulation with secretagogues of differential efficacy. Of the three secretagogues tested, inactivation of PKCs by long-term phorbol 12-myristate 13-acetate (PMA) treatment or incubation with GF109203X had the greatest inhibitory effect on nicotine-induced catecholamine release and MEK/MAPK activation, a moderate effect on KCl-induced events, and little, if any, effect on Ca2+ ionophore-elicited exocytosis and MEK/MAPK activation. These results indicate that PKC plays a significant role in events induced by the optimal secretagogue nicotine and a lesser role in exocytosis elicited by the suboptimal secretagogues KCl and Ca2+ ionophore. Treatment of cells with the MEK-activation inhibitor PD098059 completely inhibited MEK/MAPK activation (IC50 1–5 µM) and partially inhibited catecholamine release induced by all secretagogues. However, PD098059 was more effective at inhibiting exocytosis induced by suboptimal secretagogues (IC50~10 µM) than that induced by nicotine (IC50~30 µM). These results suggest a more prominent role for MEK/MAPK in basic secretory events activated by suboptimal secretagogues than in those activated by the optimal secretagogue nicotine. However, PD098059 also partially blocked secretion potentiated by short-term PMA treatment, suggesting that PKC can function in part by signaling through MEK/MAPK to enhance secretion. Taken together, these results provide evidence for the preferential involvement of MEK/MAPK in basic secretory events activated by the suboptimal secretagogues KCl and Ca2+ ionophore and the participation of both PKC and MEK/MAPK in optimal secretion induced by nicotine. 相似文献
153.
G R Thomas O Jensson G Gudmundsson L Thorsteinsson D W Cox 《American journal of human genetics》1995,56(5):1140-1146
154.
Baker R. L. Cox E. H. Carter A. H. 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1984,67(2-3):113-122
Summary Four lines of mice were formed from a common base population and selected for 37 generations for either increased 3-week weight (weaning weight), 6-week weight, 3–6 week gain, or maintained as a randomly bred control line. Realised heritability estimates for short-term (long-term) responses were 0.33±0.20 (0.07±0.10), 0.46±0.14 (0.26±0.09), 0.36±0.14 (0.24±0.11) for 3-week weight, 6-week weight and 3–6 week gain, respectively. Realised genetic correlations estimated from short-term (long-term) responses were 0.23±0.08 (0.35±0.10) between 3-week weight and 3–6 week gain; 0.82±0.04 (0.58±0.08) between 3-week weight and 6-week weight; and 0.81±0.04 (0.97±0.04) between 3–6 week gain and 6-week weight. The genetic correlation between 3-week weight and 6-week weight was asymmetric with a greater correlated response for 3-week weight when selecting for 6-week weight (1.06) than vice versa (0.63). 相似文献
155.
Thymidine-kinase activity of cultured cells from individuals with inherited galactokinase deficiency 总被引:1,自引:1,他引:0
Cells of a person homozygous for galactokinase deficiency and of her heterozygous parents were found to be deficient in the enzyme thymidine kinase. The decrease in thymidine-kinase activity may be the result of a qualitative alteration in the enzyme molecule. This is reflected in the apparent alteration in the sensitivity of the enzyme to trifluorothymidine. It is suggested that this relationship between the galactokinase and thymidine kinase is not fortuitous but a reflection of their interdependence as found previously in the Chinese hamster. 相似文献
156.
R N Cox R R Kaldany P W Brandt B Ferren R A Hudson A Karlin 《Analytical biochemistry》1984,136(2):476-486
A continuous-flow technique is described in which a photoaffinity label, membrane rich in acetylcholine receptor, and various effectors are rapidly mixed, passed through a delay tube, through a tube in which they are irradiated, and are collected in a tube containing quencher. Delay times as short as 20 ms between mixing and photolysis are achievable. Because the flow is continuous, milliliter volumes of membrane can be labeled in a single run, which is convenient for the analysis of both the functional effects and sites of photolabeling. Using this technique, we have found that receptor in its transitory, active state, in which the channel is open, is more susceptible to photolabeling by the noncompetitive inhibitor analog [3H] quinacrine azide than is receptor in either its resting or desensitized states, in which the channel is closed. This technique should prove generally useful for the photolabeling of transient conformational states of macromolecules. 相似文献
157.
T. S. Cox 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1984,68(1-2):183-186
Summary The genetic variance among random-mated lines derived from backcrossing (BCgS1 lines) depends upon the backcross generation (g) and the number (n) of BCgF1 plants crossed in generations 1 through g. There is little effect of n on genetic variance for n > 6. The genetic variance among BCgF2-derived lines is greater than that among BCgS1 lines for all g. If either BCgF2-derived or BCgS1 lines are used as a base population for recurrent selection, 8, 16, 32, and 64 BC1F1, BC2F1, BC3F1, and BC4F1 plants, respectively, should be used to avoid loss of donor alleles to drift.Joint contribution of USDA-ARS and Journal Paper No. J-11224 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2471Formerly Research Geneticist, USDA-ARS, Ames, Iowa, USA 相似文献
158.
159.
160.
Comparison of aldolase isozymes in placenta, HeLa cells, and human fibroblast cultures 总被引:1,自引:0,他引:1
The aldolase specific activity of the human carcinoma cell line, HeLa, against fructose 1,6-diphosphate as substrate is 4- to 5-fold greater than the specific activity of diploid human fibroblast cultures derived from skin and lung. HeLa aldolase is isozyme is predominantly the A type and its substrate preferences resemble human placenta. These findings provide further support for the oncofetal enzyme consitution of HeLa cells. 相似文献