全文获取类型
收费全文 | 2955篇 |
免费 | 182篇 |
专业分类
3137篇 |
出版年
2023年 | 14篇 |
2022年 | 39篇 |
2021年 | 56篇 |
2020年 | 35篇 |
2019年 | 76篇 |
2018年 | 69篇 |
2017年 | 53篇 |
2016年 | 89篇 |
2015年 | 164篇 |
2014年 | 140篇 |
2013年 | 208篇 |
2012年 | 243篇 |
2011年 | 209篇 |
2010年 | 136篇 |
2009年 | 101篇 |
2008年 | 173篇 |
2007年 | 179篇 |
2006年 | 169篇 |
2005年 | 162篇 |
2004年 | 158篇 |
2003年 | 132篇 |
2002年 | 151篇 |
2001年 | 22篇 |
2000年 | 16篇 |
1999年 | 28篇 |
1998年 | 21篇 |
1997年 | 19篇 |
1996年 | 23篇 |
1995年 | 19篇 |
1994年 | 16篇 |
1993年 | 14篇 |
1992年 | 11篇 |
1991年 | 19篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 21篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有3137条查询结果,搜索用时 0 毫秒
1.
2.
Roberta L. Millstein 《Journal of the history of biology》2008,41(2):339-367
Biologists and philosophers have been extremely pessimistic about the possibility of demonstrating random drift in nature,
particularly when it comes to distinguishing random drift from natural selection. However, examination of a historical case
– Maxime Lamotte’s study of natural populations of the land snail, Cepaea nemoralis in the 1950s – shows that while some pessimism is warranted, it has been overstated. Indeed, by describing a unique signature
for drift and showing that this signature obtained in the populations under study, Lamotte was able to make a good case for
a significant role for␣drift. It may be difficult to disentangle the causes of drift and selection acting in a population,
but it is not (always) impossible. 相似文献
3.
4.
5.
6.
7.
8.
Roberta Colombo Raffaella Cerana Piera Lado Antonio Peres 《The Journal of membrane biology》1988,103(3):227-236
Summary The patch-clamp technique in whole-cell configuration was used to study the electrical properties of the tonoplast in isolated vacuoles fromAcer pseudoplatanus cultured cells. In symmetrical KCl or K2 malate solutions, voltage- and time-dependent inward currents were elicited by hyperpolarizing the tonoplast (inside negative), while in the positive range of potential the conductance was very small. The specific conductance of the tonoplast at –100 mV, in 100mm symmetrical KCl was about 160 S/cm2. The reversal potentials (E
rev) of the current, measured in symmetrical or asymmetrical ion concentrations (cation, anion or both) were very close to the values of the K+ equilibrium potential. Experiments performed in symmetrical or asymmetrical NaCl indicate that Na+ too can flow through the channels. NeitherE
rev nor amplitude and kinetics of the current changed by replacing NaCl with KCl in the external solution. These results indicate the presence of hyperpolarization-activated channels in tonoplasts, which are permeable to K+ as well as to Na+. Anions such as Cl– or malate seem to contribute little to the channel current. 相似文献
9.
10.