全文获取类型
收费全文 | 729篇 |
免费 | 84篇 |
出版年
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 10篇 |
2015年 | 25篇 |
2014年 | 36篇 |
2013年 | 35篇 |
2012年 | 38篇 |
2011年 | 23篇 |
2010年 | 27篇 |
2009年 | 19篇 |
2008年 | 26篇 |
2007年 | 24篇 |
2006年 | 30篇 |
2005年 | 32篇 |
2004年 | 23篇 |
2003年 | 13篇 |
2002年 | 24篇 |
2001年 | 17篇 |
2000年 | 15篇 |
1999年 | 16篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1981年 | 6篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1969年 | 5篇 |
1909年 | 5篇 |
1905年 | 4篇 |
1904年 | 7篇 |
排序方式: 共有813条查询结果,搜索用时 15 毫秒
131.
Antonio C. L. da Costa Lucy Rowland Rafael S. Oliveira Alex A. R. Oliveira Oliver J. Binks Yann Salmon Steel S. Vasconcelos João A. S. Junior Leandro V. Ferreira Rafael Poyatos Maurizio Mencuccini Patrick Meir 《Global Change Biology》2018,24(1):249-258
Transpiration from the Amazon rainforest generates an essential water source at a global and local scale. However, changes in rainforest function with climate change can disrupt this process, causing significant reductions in precipitation across Amazonia, and potentially at a global scale. We report the only study of forest transpiration following a long‐term (>10 year) experimental drought treatment in Amazonian forest. After 15 years of receiving half the normal rainfall, drought‐related tree mortality caused total forest transpiration to decrease by 30%. However, the surviving droughted trees maintained or increased transpiration because of reduced competition for water and increased light availability, which is consistent with increased growth rates. Consequently, the amount of water supplied as rainfall reaching the soil and directly recycled as transpiration increased to 100%. This value was 25% greater than for adjacent nondroughted forest. If these drought conditions were accompanied by a modest increase in temperature (e.g., 1.5°C), water demand would exceed supply, making the forest more prone to increased tree mortality. 相似文献
132.
Heterogeneity in host susceptibility and transmissibility to parasite attack allows a lower transmission rate to sustain an epidemic than is required in homogeneous host populations. However, this heterogeneity can leave some hosts with little susceptibility to disease, and at high transmission rates, epidemic size can be smaller than for diseases where the host population is homogeneous. In a heterogeneous host population, we model natural selection in a parasite population where host heterogeneity is exploited by different strains to varying degrees. This partitioning of the host population allows coexistence of competing parasite strains, with the heterogeneity-exploiting strains infecting the more susceptible hosts, in the absence of physiological tradeoffs and spatial heterogeneity, and even for markedly different transmission rates. In our model, intermediate-strategy parasites were selected against: should coexistence occur, an equilibrium is reached where strains occupied only the extreme ends of trait space, under appropriate conditions selecting for lower R0 . 相似文献
133.
Comparison of Cultures from Rectoanal-Junction Mucosal Swabs and Feces for Detection of Escherichia coli O157 in Dairy Heifers 下载免费PDF全文
Margaret A. Davis Daniel H. Rice Haiqing Sheng Dale D. Hancock Thomas E. Besser Rowland Cobbold Carolyn J. Hovde 《Applied microbiology》2006,72(5):3766-3770
Fecal culture for Escherichia coli O157:H7 was compared to rectoanal mucosal swab (RAMS) culture in dairy heifers over a 1-year period. RAMS enrichment culture was as sensitive as fecal culture using immunomagnetic separation (IMS) (P = 0.98, as determined by a chi-square test). RAMS culture is less costly than fecal IMS culture and can yield quantitative data. 相似文献
134.
135.
136.
137.
138.
139.
140.