全文获取类型
收费全文 | 87235篇 |
免费 | 7725篇 |
国内免费 | 42篇 |
出版年
2023年 | 286篇 |
2022年 | 708篇 |
2021年 | 1575篇 |
2020年 | 887篇 |
2019年 | 1121篇 |
2018年 | 1449篇 |
2017年 | 1248篇 |
2016年 | 2143篇 |
2015年 | 3665篇 |
2014年 | 4089篇 |
2013年 | 4855篇 |
2012年 | 6593篇 |
2011年 | 6532篇 |
2010年 | 4209篇 |
2009年 | 3826篇 |
2008年 | 5476篇 |
2007年 | 5480篇 |
2006年 | 5285篇 |
2005年 | 5077篇 |
2004年 | 4932篇 |
2003年 | 4700篇 |
2002年 | 4435篇 |
2001年 | 900篇 |
2000年 | 661篇 |
1999年 | 1014篇 |
1998年 | 1252篇 |
1997年 | 831篇 |
1996年 | 758篇 |
1995年 | 660篇 |
1994年 | 625篇 |
1993年 | 677篇 |
1992年 | 585篇 |
1991年 | 534篇 |
1990年 | 490篇 |
1989年 | 423篇 |
1988年 | 442篇 |
1987年 | 358篇 |
1986年 | 345篇 |
1985年 | 425篇 |
1984年 | 538篇 |
1983年 | 420篇 |
1982年 | 519篇 |
1981年 | 506篇 |
1980年 | 431篇 |
1979年 | 325篇 |
1978年 | 334篇 |
1977年 | 299篇 |
1976年 | 275篇 |
1975年 | 230篇 |
1974年 | 266篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Michael Jamieson 《BMJ (Clinical research ed.)》1980,281(6253):1466
102.
103.
Steven I. Higgins Robert B. O’Hara Olga Bykova Michael D. Cramer Isabelle Chuine Eva‐Maria Gerstner Thomas Hickler Xavier Morin Michael R. Kearney Guy F. Midgley Simon Scheiter 《Journal of Biogeography》2012,39(12):2132-2145
Aim To develop a physiologically based model of the plant niche for use in species distribution modelling. Location Europe. Methods We link the Thornley transport resistance (TTR) model with functions which describe how the TTR’s model parameters are influenced by abiotic environmental factors. The TTR model considers how carbon and nutrient uptake, and the allocation of these assimilates, influence growth. We use indirect statistical methods to estimate the model parameters from a high resolution data set on tree distribution for 22 European tree species. Results We infer, from distribution data and abiotic forcing data, the physiological niche dimensions of 22 European tree species. We found that the model fits were reasonable (AUC: 0.79–0.964). The projected distributions were characterized by a false positive rate of 0.19 and a false negative rate 0.12. The fitted models are used to generate projections of the environmental factors that limit the range boundaries of the study species. Main conclusions We show that physiological models can be used to derive physiological niche dimensions from species distribution data. Future work should focus on including prior information on physiological rates into the parameter estimation process. Application of the TTR model to species distribution modelling suggests new avenues for establishing explicit links between distribution and physiology, and for generating hypotheses about how ecophysiological processes influence the distribution of plants. 相似文献
104.
105.
106.
107.
Michael J. Gentle 《Behavioural processes》1981,6(2):109-120
The oral behaviour of adult Brown Leghorn hens was recorded in response to oral stimulation with water, 2 M sodium chloride, 2 M acetic acid and 0.1 M quinine hydrochloride before and after surgical ablation of either the anterior telencephalon or the entire telencephalon and/or the diencephalon. It was found that beak wiping behaviour could be abolished by the removal of the anterior telencephalon. Head shaking behaviour was abolished only by the complete removal of the forebrain (telencephalon and diencephalon) whereas beak and tongue movements persisted after forebrain removal. Although these three behaviour patterns occur together in response to the stimulus, they appear to be controlled in different areas of the brain. The results are discussed in relation to the current work on the control of oral behaviour in mammals. 相似文献
108.
109.
110.
Rabbit alveolar macrophages exhibit a chemiluminescent response which is associated with phagocytosis of zymosan and polystyrene-butadiene particles. The chemiluminescence reaches a peak in 15 to 25 minutes and then gradually diminishes over the next 1 to 3 hours. During the time of maximal light emission there appears to be no actual uptake of particles, but the response is dependent upon the particle concentration. The metabolic inhibitor, DNP (2,4-dinitrophenol), causes a rapid inhibition of the chemiluminescent response. The addition of ATP to the medium prior to exposure of the cells to particles causes the chemiluminescent response to be greatly diminished, i.e., 0.3mM ATP virtually abolishes the response. These experiments suggest that some metabolic response of the cell to phagocytosis is responsible for the chemiluminescence. 相似文献