全文获取类型
收费全文 | 5600篇 |
免费 | 986篇 |
国内免费 | 1篇 |
出版年
2022年 | 55篇 |
2021年 | 80篇 |
2019年 | 64篇 |
2018年 | 66篇 |
2017年 | 66篇 |
2016年 | 94篇 |
2015年 | 164篇 |
2014年 | 184篇 |
2013年 | 239篇 |
2012年 | 253篇 |
2011年 | 279篇 |
2010年 | 174篇 |
2009年 | 133篇 |
2008年 | 205篇 |
2007年 | 242篇 |
2006年 | 290篇 |
2005年 | 269篇 |
2004年 | 288篇 |
2003年 | 251篇 |
2002年 | 239篇 |
2001年 | 204篇 |
2000年 | 149篇 |
1999年 | 136篇 |
1998年 | 50篇 |
1997年 | 62篇 |
1996年 | 69篇 |
1995年 | 57篇 |
1994年 | 57篇 |
1993年 | 50篇 |
1992年 | 98篇 |
1991年 | 92篇 |
1990年 | 92篇 |
1989年 | 75篇 |
1988年 | 81篇 |
1987年 | 85篇 |
1986年 | 99篇 |
1985年 | 99篇 |
1984年 | 58篇 |
1983年 | 60篇 |
1981年 | 62篇 |
1980年 | 54篇 |
1979年 | 81篇 |
1977年 | 52篇 |
1976年 | 51篇 |
1974年 | 70篇 |
1973年 | 66篇 |
1972年 | 56篇 |
1971年 | 65篇 |
1970年 | 55篇 |
1969年 | 48篇 |
排序方式: 共有6587条查询结果,搜索用时 656 毫秒
31.
32.
We review the New Caledonian representatives of the Australasian endemic hydroptiline genus Acritoptila, based on examination of a considerable collection of material in the Swedish Museum of Natural History and of types of previously established species. A key for identification of males is given and includes 3 species newly described here: A. parallela
sp. n., A. forficata
sp. n. and A. macrospina
sp. n. For all New Caledonian species, male genitalia are illustrated, and for 5 associated females, distinctive features are illustrated and described. 相似文献
33.
34.
35.
36.
37.
38.
Parameters of brown-headed cowbird Molothrus ater egg discrimination in warbling vireos Vireo gilvus
We examined which egg parameters warbling vireos Vireo gilvus use to discriminate brown-headed cowbird Molothrus ater eggs and, by comparing our results to other studies, tested the prediction that ejecter species with eggs more similar in appearance to cowbird eggs will be less tolerant of foreign eggs. In addition, we tested the hypothesis that egg characteristics influence the cost of ejection and probability of committing ejection errors. Warbling vireos ejected 100% of eggs with a cowbird spot pattern and only spot pattern significantly influenced the probability of ejecting a foreign egg, whereas size and nest stage did not. Foreign eggs that differed in two parameters were not ejected significantly more than those that differed in one parameter. Thus, warbling vireos appear to be less tolerant of foreign eggs than species with eggs more divergent from cowbird eggs. There was no significant difference in the number of vireo eggs that were damaged when foreign eggs of different sizes and spot patterns were ejected, which is counter to the assumptions of the evolutionary equilibrium hypothesis. Similarly, foreign egg characteristics did not significantly influence the probability of ejection errors. Finally, egg discrimination in warbling vireos appears to have evolved directly to counter cowbird parasitism because all conspecific eggs switched into their nests were accepted. 相似文献
39.
40.