全文获取类型
| 收费全文 | 10612篇 |
| 免费 | 1589篇 |
| 国内免费 | 1304篇 |
专业分类
| 测绘学 | 973篇 |
| 大气科学 | 1183篇 |
| 地球物理 | 2980篇 |
| 地质学 | 2972篇 |
| 海洋学 | 1645篇 |
| 天文学 | 456篇 |
| 综合类 | 774篇 |
| 自然地理 | 2522篇 |
出版年
| 2024年 | 30篇 |
| 2023年 | 127篇 |
| 2022年 | 340篇 |
| 2021年 | 381篇 |
| 2020年 | 390篇 |
| 2019年 | 455篇 |
| 2018年 | 327篇 |
| 2017年 | 429篇 |
| 2016年 | 431篇 |
| 2015年 | 435篇 |
| 2014年 | 597篇 |
| 2013年 | 567篇 |
| 2012年 | 543篇 |
| 2011年 | 660篇 |
| 2010年 | 497篇 |
| 2009年 | 666篇 |
| 2008年 | 667篇 |
| 2007年 | 759篇 |
| 2006年 | 721篇 |
| 2005年 | 601篇 |
| 2004年 | 529篇 |
| 2003年 | 467篇 |
| 2002年 | 381篇 |
| 2001年 | 351篇 |
| 2000年 | 340篇 |
| 1999年 | 274篇 |
| 1998年 | 303篇 |
| 1997年 | 183篇 |
| 1996年 | 181篇 |
| 1995年 | 154篇 |
| 1994年 | 152篇 |
| 1993年 | 128篇 |
| 1992年 | 96篇 |
| 1991年 | 75篇 |
| 1990年 | 50篇 |
| 1989年 | 72篇 |
| 1988年 | 36篇 |
| 1987年 | 28篇 |
| 1986年 | 14篇 |
| 1985年 | 16篇 |
| 1984年 | 12篇 |
| 1983年 | 3篇 |
| 1982年 | 9篇 |
| 1981年 | 4篇 |
| 1980年 | 6篇 |
| 1979年 | 3篇 |
| 1978年 | 7篇 |
| 1977年 | 2篇 |
| 1976年 | 1篇 |
| 1954年 | 5篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
21.
Zoran Knežević 《Celestial Mechanics and Dynamical Astronomy》1993,55(4):387-404
Leverrier's development of the indirect part of the disturbing function has been extended to include terms up to degree 4 in eccentricity and inclination; the resulting series has been expressed with respect to a fixed plane, and in a computer readable form (a list of integers). Tests have been performed for the relative significance of the terms of degrees 2, 3 and 4, and estimates have been obtained for the accuracy of the short periodic perturbations of a minor planet, and of the corresponding mean orbital elements. It was found that: (i) even in extreme cases, the indirect part of the disturbing function gives rise to very small short periodic perturbations; (ii) bodies of very high eccentricity/inclination and those close to mean motion resonances are most significantly affected; (iii) indirect perturbations for minor planets can be computed up to the degree 2 terms only, without any significant loss of accuracy; and (iv) higher degree indirect perturbations appear to be important only for their contribution to the long periodic effects of higher order (with respect to the perturbing mass). 相似文献
22.
23.
24.
Wang Yanhui 《水文研究》1992,6(2):241-251
Black locust (Robina pseudoacacia) has become one of the most important shelter species in the loess area of northwest China. This paper summarizes recent research concerning its hydrological influence, including canopy interception, litter absorption capacity, its effect on rainfall kinetic energy, infiltration rates, surface runoff, soil moisture, and evapotranspiration, and its role in soil conservation. Several predictive models are listed. on the basis of existing results, optimum characteristics for an effective plantation are defined, and problems requiring further research are identified. 相似文献
25.
26.
27.
We present predictions for the numbers of ultracool dwarfs in the Galactic disc population that could be detected by the WFCAM/UKIDSS Large Area Survey and Ultra Deep Survey. Simulated samples of objects are created with masses and ages drawn from different mass functions and birthrates. Each object is then given absolute magnitudes in different passbands based on empirically derived bolometric correction versus effective temperature relationships (or model predictions for Y dwarfs). These are then combined with simulated space positions, velocities and photometric errors to yield observables such as apparent magnitudes and proper motions. Such observables are then passed through the survey selection mechanism to yield histograms in colour. This technique also produces predictions for the proper motion histograms for ultracool dwarfs and estimated numbers for the as yet undetected Y dwarfs. Finally, it is shown that these techniques could be used to constrain the ultra-low-mass mass function and birthrate of the Galactic disc population. 相似文献
28.
Theoretical predictions of an accretion model of star formation in galactic clusters, published quite long ago, which is found
to have some relevance with the current picture of star formation have been tested with observation of seven clusters of young
and intermediate ages. It is found that the agreement between the theory and observation is very good. 相似文献
29.
30.