全文获取类型
收费全文 | 574168篇 |
免费 | 62954篇 |
国内免费 | 3807篇 |
专业分类
640929篇 |
出版年
2021年 | 6005篇 |
2019年 | 5085篇 |
2018年 | 7020篇 |
2017年 | 6504篇 |
2016年 | 8837篇 |
2015年 | 11111篇 |
2014年 | 13406篇 |
2013年 | 18360篇 |
2012年 | 20538篇 |
2011年 | 20654篇 |
2010年 | 13925篇 |
2009年 | 12757篇 |
2008年 | 17439篇 |
2007年 | 17728篇 |
2006年 | 16459篇 |
2005年 | 15501篇 |
2004年 | 15250篇 |
2003年 | 14519篇 |
2002年 | 13788篇 |
2001年 | 29031篇 |
2000年 | 28785篇 |
1999年 | 22444篇 |
1998年 | 7062篇 |
1997年 | 7581篇 |
1996年 | 6995篇 |
1995年 | 6485篇 |
1994年 | 6243篇 |
1993年 | 6155篇 |
1992年 | 17265篇 |
1991年 | 16488篇 |
1990年 | 15869篇 |
1989年 | 15360篇 |
1988年 | 14021篇 |
1987年 | 13077篇 |
1986年 | 12163篇 |
1985年 | 11916篇 |
1984年 | 9745篇 |
1983年 | 8164篇 |
1982年 | 6058篇 |
1981年 | 5429篇 |
1980年 | 5138篇 |
1979年 | 8982篇 |
1978年 | 6859篇 |
1977年 | 6310篇 |
1976年 | 5679篇 |
1975年 | 6266篇 |
1974年 | 6789篇 |
1973年 | 6585篇 |
1972年 | 6018篇 |
1971年 | 5456篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
G S Aulakh E B Stephens D L Rose J G Tully M F Barile 《Journal of bacteriology》1983,153(3):1338-1341
3H-labeled Acholeplasma DNA probes were generated in vitro by the nick-translation method and used to determine the nucleotide sequence homology among the type strains of the eight currently recognized species of Acholeplasma. Very little nucleotide sequence homology (less than or equal to 18%) was found among the eight species, with heteroduplexes showing at least 12% or more mismatching as determined by thermal elution midpoints. The small amount of nucleotide sequence homology among the eight species indicates that these species are quite distinct and are not closely related to each other genomically. 相似文献
72.
A. V. Nikolayev Yu. V. Kirichek O. I. Ostrovskaya I. I. Maletina K. I. Petko L. M. Yagupol’skii 《Neurophysiology》1999,31(3):191-193
With the use of a patch-clamp technique in the whole-cell configuration, we studied the effects of pinacidil and its fluorine
derivatives on A-type potassium current (I
A) through the membrane of pyramidal neurons of the rat hippocampus. Hydrogen peroxide (10 mM) exerted no influence on the
rate of inactivation ofI
A; therefore, this current is probably mediated by Shal Kv4.2 potassium channels. Pinacidil demonstrated the properties of
a weakI
A blocker: in the 500 μM concentration it blocked about 45% of the current, while 50 μM of pinacidil fluorine derivatives were
capable of blocking up to 30% ofI
A. The effects of pinacidil and its derivatives showed no dependence on the stimulating potential. A similar pattern of the
effects of pinacidil fluorine derivatives, which are an order of magnitude stronger than those of pinacidil itself, allows
us to suppose that the imine nitrogen of the tested compounds is significantly more involved in the molecular interaction
with the site of an A-type potassium channel than the pyridine nitrogen. 相似文献
73.
74.
75.
76.
77.
78.
Biotin and protein synthesis in rat liver 总被引:5,自引:0,他引:5
79.
Robert S. Steneck 《Current biology : CB》2009,19(3):R117-R119
80.
Isolation of viral coat protein mutants with altered assembly and aggregation properties 总被引:1,自引:0,他引:1 下载免费PDF全文
A method was developed to screen bacteria for synthesis of mutant proteins with altered assembly and solubility properties using bacteriophage MS2 coat protein as a model self-associating protein. Colonies expressing coat protein from a plasmid were covered with an agarose overlay under conditions that caused the lysis of some of the cells in each colony. The proteins thus liberated diffused through the overlay at rates depending on their molecular sizes. After transfer of the proteins to a nitrocellulose membrane, probing with coat protein-specific antiserum revealed spots whose sizes and intensities were related to the aggregation state of coat protein. The method was employed in the isolation of assembly defective mutants and to find soluble variants of an aggregation-prone coat protein mutant. 相似文献