全文获取类型
收费全文 | 6861篇 |
免费 | 620篇 |
国内免费 | 69篇 |
出版年
2024年 | 9篇 |
2023年 | 58篇 |
2022年 | 99篇 |
2021年 | 195篇 |
2020年 | 129篇 |
2019年 | 180篇 |
2018年 | 190篇 |
2017年 | 201篇 |
2016年 | 241篇 |
2015年 | 414篇 |
2014年 | 402篇 |
2013年 | 521篇 |
2012年 | 609篇 |
2011年 | 554篇 |
2010年 | 399篇 |
2009年 | 350篇 |
2008年 | 419篇 |
2007年 | 360篇 |
2006年 | 325篇 |
2005年 | 279篇 |
2004年 | 299篇 |
2003年 | 217篇 |
2002年 | 225篇 |
2001年 | 69篇 |
2000年 | 44篇 |
1999年 | 51篇 |
1998年 | 48篇 |
1997年 | 45篇 |
1996年 | 37篇 |
1995年 | 37篇 |
1994年 | 34篇 |
1993年 | 40篇 |
1992年 | 30篇 |
1991年 | 30篇 |
1990年 | 36篇 |
1989年 | 32篇 |
1988年 | 19篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 18篇 |
1982年 | 25篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 12篇 |
排序方式: 共有7550条查询结果,搜索用时 0 毫秒
31.
R. B. Singh Ben W. Smith 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1971,41(8):360-364
Summary Cytogenetic studies were made with particular emphasis on the sex-determining mechanism in Rumex acetosella (6 x = 42) and its hybrids (F
1, F
2, BC
1 and BC
2) with R. hastatulus (synthetic 4 x = 16 = 4 A +4 X = and 4 x = 18 = 4 A + 2 (X Y
1
Y
2) = ). Rumex acetosella was almost strictly dioecious with 5050 male and female. Breeding tests revealed that the males were heterogametic. The longest chromosomes (S), usually two, are the sex chromosomes of this hexaploid species. The S chromosomes are homomorphic in both male and female. The sex chromosome: autosome ratios, and the strong epistatic male effect of the S
M chromosome in the polyploid dioecious species and in the hybrids, are evidence of an X/Y Melandrium type sex-determining mechanism controlled by a single pair of homomorphic sex chromosomes. Thus, the sex chromosome formula of the males was S
F
S
M and that of females was S
F
S
F. The present approach is a new method for resolving the sex-determining mechanism in a dioecious species. 相似文献
32.
33.
34.
Effect of Temperature on the Potential and Current Thresholds of Axon Membrane 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《The Journal of general physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Rita Guttman with the technical assistance of Ben Sandler 《The Journal of general physiology》1962,46(2):257-266
The effect of temperature on the potential and current thresholds of the squid giant axon membrane was measured with gross external electrodes. A central segment of the axon, 0.8 mm long and in sea water, was isolated by flowing low conductance, isoosmotic sucrose solution on each side; both ends were depolarized in isoosmotic KCl. Measured biphasic square wave currents at five cycles per second were applied between one end of the nerve and the membrane of the central segment. The membrane potential was recorded between the central sea water and the other depolarized end. The recorded potentials are developed only across the membrane impedance. Threshold current values ranged from 3.2 µa at 267deg;C to 1 µa at 7.5°C. Threshold potential values ranged from 50 mv at 26°C to 6 mv at 7.5°C. The mean Q10 of threshold current was 2.3 (SD = 0.2), while the Q10 for threshold potentials was 2.0 (SD = 0.1). 相似文献
35.
36.
37.
38.
39.
40.