全文获取类型
收费全文 | 191篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 1篇 |
丛书文集 | 53篇 |
现状及发展 | 37篇 |
研究方法 | 9篇 |
综合类 | 90篇 |
自然研究 | 3篇 |
出版年
2020年 | 1篇 |
2018年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 9篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1970年 | 4篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1963年 | 1篇 |
1959年 | 16篇 |
1958年 | 30篇 |
1957年 | 22篇 |
1956年 | 10篇 |
1955年 | 15篇 |
1954年 | 23篇 |
1948年 | 7篇 |
1947年 | 3篇 |
排序方式: 共有193条查询结果,搜索用时 31 毫秒
51.
Losos JB Leal M Glor RE De Queiroz K Hertz PE Rodríguez Schettino L Lara AC Jackman TR Larson A 《Nature》2003,424(6948):542-545
Niche conservatism--the tendency for closely related species to be ecologically similar--is widespread. However, most studies compare closely related taxa that occur in allopatry; in sympatry, the stabilizing forces that promote niche conservatism, and thus inhibit niche shifts, may be countered by natural selection favouring ecological divergence to minimize the intensity of interspecific interactions. Consequently, the relative importance of niche conservatism versus niche divergence in determining community structure has received little attention. Here, we examine a tropical lizard community in which species have a long evolutionary history of ecological interaction. We find that evolutionary divergence overcomes niche conservatism: closely related species are no more ecologically similar than expected by random divergence and some distantly related species are ecologically similar, leading to a community in which the relationship between ecological similarity and phylogenetic relatedness is very weak. Despite this lack of niche conservatism, the ecological structuring of the community has a phylogenetic component: niche complementarity only occurs among distantly related species, which suggests that the strength of ecological interactions among species may be related to phylogeny, but it is not necessarily the most closely related species that interact most strongly. 相似文献
52.
Zusammenfassung Mit Hilfe von radioaktiv markiertem Prolin wird autoradiographisch das Vorkommen von Collagen im Matrixeiweiss pflanzlicher Zellkerne festgestellt.
This investigation was partially supported by a Ford Foundation Grant to the Department of Agricultural Engineering of this Institute. Thanks are due to Prof.V. N. Prasad, Director, and Prof.A. C. Pandya, Head of the Department of Agricultural Engineering of this Institute. 相似文献
This investigation was partially supported by a Ford Foundation Grant to the Department of Agricultural Engineering of this Institute. Thanks are due to Prof.V. N. Prasad, Director, and Prof.A. C. Pandya, Head of the Department of Agricultural Engineering of this Institute. 相似文献
53.
54.
55.
56.
57.
58.
59.
60.