全文获取类型
收费全文 | 5591篇 |
免费 | 683篇 |
国内免费 | 202篇 |
出版年
2021年 | 70篇 |
2020年 | 56篇 |
2019年 | 61篇 |
2018年 | 68篇 |
2017年 | 63篇 |
2016年 | 90篇 |
2015年 | 143篇 |
2014年 | 159篇 |
2013年 | 219篇 |
2012年 | 292篇 |
2011年 | 249篇 |
2010年 | 180篇 |
2009年 | 173篇 |
2008年 | 212篇 |
2007年 | 243篇 |
2006年 | 187篇 |
2005年 | 174篇 |
2004年 | 199篇 |
2003年 | 168篇 |
2002年 | 205篇 |
2001年 | 169篇 |
2000年 | 188篇 |
1999年 | 146篇 |
1998年 | 98篇 |
1997年 | 62篇 |
1996年 | 63篇 |
1995年 | 55篇 |
1993年 | 52篇 |
1992年 | 132篇 |
1991年 | 114篇 |
1990年 | 156篇 |
1989年 | 102篇 |
1988年 | 105篇 |
1987年 | 107篇 |
1986年 | 91篇 |
1985年 | 94篇 |
1984年 | 85篇 |
1983年 | 58篇 |
1982年 | 92篇 |
1981年 | 75篇 |
1980年 | 64篇 |
1979年 | 87篇 |
1978年 | 76篇 |
1977年 | 70篇 |
1976年 | 54篇 |
1975年 | 68篇 |
1974年 | 53篇 |
1973年 | 56篇 |
1972年 | 53篇 |
1971年 | 46篇 |
排序方式: 共有6476条查询结果,搜索用时 609 毫秒
951.
952.
953.
Ten micrograms of 2-nitro-1-butyl pyridinium sulfate (NBPS) per milliliter inhibited the growth of Bacillus subtilis by blocking thymidylate synthetase. The inhibition could be reversed by the addition of thymine or cytosine. 相似文献
954.
Summary Biochemical and ultrastructural findings from intact and fractionated pig and human blood platelets indicate the presence of different types of alpha granules. An electron dense type can be distinguished from a lighter one with a fibrillar matrix. The major part of the lysosomal hydrolases beta-glucuronidase and cathepsin is associated with the lighter granules. Most of the acid phosphatase appears in the vesicle fraction. The ultracytochemical investigation shows the acid phosphatase bound to both types of granules or vesicles. This enzyme is visible in the narrow spaces between the outer membranes of aggregated thrombocytes. Furthermore, there can be seen the transformation of alpha granules into vesicles and vesicles, which contain acid phosphatase releasing their contents into the extracellular medium. Thus the significance of the vesicle system for the release of substances out of the platelet seems to be proved. From this point of view the different types could be considered as alpha granules in different functional stages.Supported by Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg. 相似文献
955.
Polar and Antipolar Mutants in the Tryptophan Operon of Salmonella typhimurium 总被引:9,自引:3,他引:6
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Elias Balbinder Arthur J. Blume Anne Weber Hideo Tamaki 《Journal of bacteriology》1968,95(6):2217-2229
Polar mutations in trpA, the first structural gene of the tryptophan operon of Salmonella typhimurium, have an uncoordinate effect on the expression of the distal genes, with trpB, the second gene, being more drastically affected than the last three. A number of these polar mutant strains grow very poorly on anthranilic acid-supplemented minimal medium. By selecting for more rapid growth in the presence of anthranilic acid, secondary mutant clones showing a correction of the polar effect were isolated. A few of these were analyzed and shown to contain deletions of various segments of the trpA gene. Ten randomly isolated deletion mutants missing various segments of the trp operon were analyzed for possible pleiotropic effects. Five of them showed a pleiotropic effect of some sort and five did not. Of those showing pleiotropic effects, one had lost the promotor-like elements necessary to initiate expression of the operon, three showed possible antipolar effects, and one showed both polar and antipolar effects simultaneously. 相似文献
956.
957.
On a new carboxypeptidase (EC 3.4.2.?) from spleen 总被引:1,自引:0,他引:1
U Stein U Weber E Buddecke 《Hoppe-Seyler's Zeitschrift für physiologische Chemie》1968,349(4):472-484
958.
Sieve-tube proteins from Cucurbita maxima 总被引:2,自引:1,他引:1
959.
960.