全文获取类型
收费全文 | 10741篇 |
免费 | 872篇 |
国内免费 | 3篇 |
专业分类
11616篇 |
出版年
2023年 | 73篇 |
2022年 | 133篇 |
2021年 | 282篇 |
2020年 | 171篇 |
2019年 | 200篇 |
2018年 | 261篇 |
2017年 | 229篇 |
2016年 | 354篇 |
2015年 | 583篇 |
2014年 | 644篇 |
2013年 | 787篇 |
2012年 | 973篇 |
2011年 | 883篇 |
2010年 | 559篇 |
2009年 | 516篇 |
2008年 | 720篇 |
2007年 | 626篇 |
2006年 | 621篇 |
2005年 | 544篇 |
2004年 | 513篇 |
2003年 | 429篇 |
2002年 | 426篇 |
2001年 | 86篇 |
2000年 | 66篇 |
1999年 | 86篇 |
1998年 | 82篇 |
1997年 | 62篇 |
1996年 | 61篇 |
1995年 | 64篇 |
1994年 | 48篇 |
1993年 | 37篇 |
1992年 | 51篇 |
1991年 | 43篇 |
1990年 | 34篇 |
1989年 | 48篇 |
1988年 | 26篇 |
1987年 | 23篇 |
1986年 | 27篇 |
1985年 | 24篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 21篇 |
1981年 | 18篇 |
1980年 | 23篇 |
1979年 | 11篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Temporal variability of top-down forces and their role in host choice evolution of phytophagous arthropods 总被引:1,自引:0,他引:1
The role of top-down forces in host choice evolution of phytophagous arthropods is the subject of a vividly animated debate. Empirical evidence for the evolutionary role of top-down forces comes from studies showing that phytophagous arthropods prefer hosts that entail enemy-free space. The aim of this paper is to draw the attention of plant–arthropod researchers to the potentially, temporally variable nature of third trophic level effects. We show that this aspect is largely neglected in studies on enemy-free space, despite the fact that relative enemy impact varies seasonally among plants in at least some studies. We conclude that rigorous testing of the enemy-free space hypothesis can only be performed when within and between season variation in higher trophic level effects is taken into account. 相似文献
2.
3.
4.
5.
Nicolas Delaleu Heike Immervoll Janet Cornelius Roland Jonsson 《Arthritis research & therapy》2008,10(1):R22
Introduction
Sj?gren's syndrome (SS) is a systemic autoimmune disease that mainly targets the exocrine glands. The aim of this study was to investigate the involvement of 87 proteins measured in serum and 75 proteins analyzed in saliva in spontaneous experimental SS. In addition, we intended to compute a model of the immunological situation representing the overt disease stage of SS. 相似文献6.
7.
8.
Loïc Pellissier Charlotte Ndiribe Anne Dubuis Jean‐Nicolas Pradervand Nicolas Salamin Antoine Guisan Sergio Rasmann 《Ecology letters》2013,16(5):600-608
Understanding drivers of biodiversity patterns is of prime importance in this era of severe environmental crisis. More diverse plant communities have been postulated to represent a larger functional trait‐space, more likely to sustain a diverse assembly of herbivore species. Here, we expand this hypothesis to integrate environmental, functional and phylogenetic variation of plant communities as factors explaining the diversity of lepidopteran assemblages along elevation gradients in the Swiss Western Alps. According to expectations, we found that the association between butterflies and their host plants is highly phylogenetically structured. Multiple regression analyses showed the combined effect of climate, functional traits and phylogenetic diversity in structuring butterfly communities. Furthermore, we provide the first evidence that plant phylogenetic beta diversity is the major driver explaining butterfly phylogenetic beta diversity. Along ecological gradients, the bottom up control of herbivore diversity is thus driven by phylogenetically structured turnover of plant traits as well as environmental variables. 相似文献
9.