全文获取类型
收费全文 | 39080篇 |
免费 | 3521篇 |
国内免费 | 21篇 |
专业分类
42622篇 |
出版年
2023年 | 237篇 |
2022年 | 498篇 |
2021年 | 1069篇 |
2020年 | 616篇 |
2019年 | 778篇 |
2018年 | 923篇 |
2017年 | 777篇 |
2016年 | 1202篇 |
2015年 | 2002篇 |
2014年 | 2229篇 |
2013年 | 2366篇 |
2012年 | 3343篇 |
2011年 | 3048篇 |
2010年 | 1956篇 |
2009年 | 1676篇 |
2008年 | 2414篇 |
2007年 | 2364篇 |
2006年 | 2136篇 |
2005年 | 2015篇 |
2004年 | 1853篇 |
2003年 | 1744篇 |
2002年 | 1617篇 |
2001年 | 341篇 |
2000年 | 240篇 |
1999年 | 343篇 |
1998年 | 414篇 |
1997年 | 274篇 |
1996年 | 245篇 |
1995年 | 211篇 |
1994年 | 215篇 |
1993年 | 219篇 |
1992年 | 218篇 |
1991年 | 206篇 |
1990年 | 192篇 |
1989年 | 166篇 |
1988年 | 176篇 |
1987年 | 163篇 |
1986年 | 129篇 |
1985年 | 129篇 |
1984年 | 165篇 |
1983年 | 125篇 |
1982年 | 154篇 |
1981年 | 146篇 |
1980年 | 133篇 |
1979年 | 103篇 |
1978年 | 107篇 |
1977年 | 99篇 |
1976年 | 82篇 |
1974年 | 71篇 |
1973年 | 83篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
142.
143.
144.
145.
146.
All Enterococcus spp., isolated from environmental water samples (n=81), emitted a high chemiluminescence signal in the presence of luminol (10(-2) M). Kinetic studies of chemiluminescence show a close correlation between chemiluminescence and growth curves during the exponential phase, with a maximum chemiluminescence reached just before bacterial growth entered in the stationary phase. On the other hand, genera closely related to Enterococcus such as Streptococcus or Lactococcus produced a very weak chemiluminescent signal. Chemiluminescence of enterococci could therefore offer a rapid test, in aiding the identification of the genus Enterococcus and in the survey of the microbiological quality of water supplies. 相似文献
147.
Among the three main categories of small silencing RNAs in insects and mammals-siRNAs, miRNAs, and piRNAs-siRNAs were thought to arise primarily from exogenous sources, whereas miRNAs and piRNAs arise from endogenous loci. Recent work in flies and mice reveals several classes of endogenous siRNAs (endo-siRNAs) that contribute to functions previously reserved for miRNAs and piRNAs, including gene regulation and transposon suppression. 相似文献
148.
149.
Ulf Büntgen Andrew Liebhold Hannes Jenny Atle Mysterud Simon Egli Daniel Nievergelt Nils C. Stenseth Kurt Bollmann 《Ecology letters》2014,17(3):303-313
Direct effects of climate change on animal physiology, and indirect impacts from disruption of seasonal synchrony and breakdown of trophic interactions are particularly severe in Arctic and Alpine ecosystems. Unravelling biotic from abiotic drivers, however, remains challenging because high‐resolution animal population data are often limited in space and time. Here, we show that variation in annual horn growth (an indirect proxy for individual performance) of 8043 male Alpine ibex (Capra ibex) over the past four decades is well synchronised among eight disjunct colonies in the eastern Swiss Alps. Elevated March to May temperatures, causing premature melting of Alpine snowcover, earlier plant phenology and subsequent improvement of ibex food resources, fuelled annual horn growth. These results reveal dependency of local trophic interactions on large‐scale climate dynamics, and provide evidence that declining herbivore performance is not a universal response to global warming even for high‐altitude populations that are also harvested. 相似文献
150.