全文获取类型
收费全文 | 1986篇 |
免费 | 213篇 |
专业分类
2199篇 |
出版年
2023年 | 15篇 |
2022年 | 20篇 |
2021年 | 47篇 |
2020年 | 29篇 |
2019年 | 32篇 |
2018年 | 41篇 |
2017年 | 28篇 |
2016年 | 61篇 |
2015年 | 80篇 |
2014年 | 89篇 |
2013年 | 82篇 |
2012年 | 132篇 |
2011年 | 123篇 |
2010年 | 64篇 |
2009年 | 70篇 |
2008年 | 85篇 |
2007年 | 106篇 |
2006年 | 103篇 |
2005年 | 79篇 |
2004年 | 70篇 |
2003年 | 69篇 |
2002年 | 69篇 |
2001年 | 50篇 |
2000年 | 37篇 |
1999年 | 46篇 |
1998年 | 25篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 19篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 19篇 |
1989年 | 19篇 |
1988年 | 14篇 |
1987年 | 18篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 19篇 |
1980年 | 22篇 |
1979年 | 19篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 20篇 |
1975年 | 18篇 |
1974年 | 28篇 |
1973年 | 29篇 |
1972年 | 16篇 |
1971年 | 18篇 |
排序方式: 共有2199条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
7.
Angus Davison †§ Johnny D. S. Birks † Rachael C. Brookes † John E. Messenger† Huw I. Griffiths‡ 《Molecular ecology》2001,10(10):2479-2488
The flora and fauna of Europe are linked by a common biogeographic history, most recently the Pleistocene glaciations that restricted the range of most species to southern refugial populations. Changes in population size and migration, as well as selection, have all left a signature on the genetic differentiation. Thus, three paradigms of postglacial recolonization have been described, inferred from the patterns of DNA differentiation. Yet some species, especially wide-ranging carnivores, exhibit little population structuring between the proposed refugia, although relatively few have been studied due to the difficulty of obtaining samples. Therefore, we investigated mitochondrial variation in pine martens, Martes martes, in order to understand the extent to which they were affected by glacial cycles, and compared the results with an analysis of sequences from polecats, Mustela putorius. A general lack of ancient lineages, and a mismatch distribution that is consistent with an expanding population, is evidence that the present-day M. martes and Mu. putorius in central and northern Europe colonized from a single European refugium following a recent glaciation. There has also been interspecific mitochondrial introgression between M. martes and the sable M. zibellina in Fennoscandia. 相似文献
8.
Wheat was inoculated with Bipolaris sorokiniana and Fusarium acuminatum individually and in combination under controlled conditions. Only B. sorokininana produced significant disease when used alone; however, F. acuminarum significantly augmented the effects of B. sorokiniana when plants are inoculated with both fungi. 相似文献
9.
Richard Horton 《BMJ (Clinical research ed.)》1985,291(6503):1204-1205
10.