全文获取类型
收费全文 | 8666篇 |
免费 | 727篇 |
国内免费 | 1篇 |
出版年
2023年 | 51篇 |
2022年 | 109篇 |
2021年 | 234篇 |
2020年 | 151篇 |
2019年 | 167篇 |
2018年 | 193篇 |
2017年 | 181篇 |
2016年 | 293篇 |
2015年 | 464篇 |
2014年 | 503篇 |
2013年 | 602篇 |
2012年 | 756篇 |
2011年 | 712篇 |
2010年 | 435篇 |
2009年 | 407篇 |
2008年 | 560篇 |
2007年 | 496篇 |
2006年 | 462篇 |
2005年 | 406篇 |
2004年 | 355篇 |
2003年 | 305篇 |
2002年 | 319篇 |
2001年 | 89篇 |
2000年 | 84篇 |
1999年 | 101篇 |
1998年 | 52篇 |
1997年 | 49篇 |
1996年 | 47篇 |
1995年 | 42篇 |
1994年 | 39篇 |
1993年 | 31篇 |
1992年 | 54篇 |
1991年 | 50篇 |
1990年 | 50篇 |
1989年 | 51篇 |
1988年 | 30篇 |
1987年 | 41篇 |
1986年 | 41篇 |
1985年 | 38篇 |
1984年 | 30篇 |
1983年 | 25篇 |
1982年 | 23篇 |
1981年 | 23篇 |
1980年 | 20篇 |
1979年 | 17篇 |
1978年 | 20篇 |
1977年 | 24篇 |
1976年 | 20篇 |
1975年 | 21篇 |
1973年 | 28篇 |
排序方式: 共有9394条查询结果,搜索用时 31 毫秒
1.
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.
Eliane S. Meier Thomas C. Edwards Jr Felix Kienast Matthias Dobbertin Niklaus E. Zimmermann 《Journal of Biogeography》2011,38(2):371-382
Aim During recent and future climate change, shifts in large‐scale species ranges are expected due to the hypothesized major role of climatic factors in regulating species distributions. The stress‐gradient hypothesis suggests that biotic interactions may act as major constraints on species distributions under more favourable growing conditions, while climatic constraints may dominate under unfavourable conditions. We tested this hypothesis for one focal tree species having three major competitors using broad‐scale environmental data. We evaluated the variation of species co‐occurrence patterns in climate space and estimated the influence of these patterns on the distribution of the focal species for current and projected future climates. Location Europe. Methods We used ICP Forest Level 1 data as well as climatic, topographic and edaphic variables. First, correlations between the relative abundance of European beech (Fagus sylvatica) and three major competitor species (Picea abies, Pinus sylvestris and Quercus robur) were analysed in environmental space, and then projected to geographic space. Second, a sensitivity analysis was performed using generalized additive models (GAM) to evaluate where and how much the predicted F. sylvatica distribution varied under current and future climates if potential competitor species were included or excluded. We evaluated if these areas coincide with current species co‐occurrence patterns. Results Correlation analyses supported the stress‐gradient hypothesis: towards favourable growing conditions of F. sylvatica, its abundance was strongly linked to the abundance of its competitors, while this link weakened towards unfavourable growing conditions, with stronger correlations in the south and at low elevations than in the north and at high elevations. The sensitivity analysis showed a potential spatial segregation of species with changing climate and a pronounced shift of zones where co‐occurrence patterns may play a major role. Main conclusions Our results demonstrate the importance of species co‐occurrence patterns for calibrating improved species distribution models for use in projections of climate effects. The correlation approach is able to localize European areas where inclusion of biotic predictors is effective. The climate‐induced spatial segregation of the major tree species could have ecological and economic consequences. 相似文献
7.
8.
9.
10.