全文获取类型
| 收费全文 | 45987篇 |
| 免费 | 704篇 |
| 国内免费 | 314篇 |
专业分类
| 测绘学 | 1106篇 |
| 大气科学 | 3063篇 |
| 地球物理 | 9211篇 |
| 地质学 | 15790篇 |
| 海洋学 | 3993篇 |
| 天文学 | 11362篇 |
| 综合类 | 99篇 |
| 自然地理 | 2381篇 |
出版年
| 2021年 | 413篇 |
| 2020年 | 470篇 |
| 2019年 | 484篇 |
| 2018年 | 1081篇 |
| 2017年 | 972篇 |
| 2016年 | 1205篇 |
| 2015年 | 685篇 |
| 2014年 | 1181篇 |
| 2013年 | 2299篇 |
| 2012年 | 1345篇 |
| 2011年 | 1818篇 |
| 2010年 | 1597篇 |
| 2009年 | 2281篇 |
| 2008年 | 1867篇 |
| 2007年 | 1898篇 |
| 2006年 | 1767篇 |
| 2005年 | 1333篇 |
| 2004年 | 1323篇 |
| 2003年 | 1245篇 |
| 2002年 | 1196篇 |
| 2001年 | 1059篇 |
| 2000年 | 1023篇 |
| 1999年 | 887篇 |
| 1998年 | 907篇 |
| 1997年 | 851篇 |
| 1996年 | 726篇 |
| 1995年 | 737篇 |
| 1994年 | 660篇 |
| 1993年 | 565篇 |
| 1992年 | 529篇 |
| 1991年 | 536篇 |
| 1990年 | 607篇 |
| 1989年 | 523篇 |
| 1988年 | 482篇 |
| 1987年 | 622篇 |
| 1986年 | 511篇 |
| 1985年 | 648篇 |
| 1984年 | 728篇 |
| 1983年 | 701篇 |
| 1982年 | 625篇 |
| 1981年 | 652篇 |
| 1980年 | 546篇 |
| 1979年 | 499篇 |
| 1978年 | 493篇 |
| 1977年 | 456篇 |
| 1976年 | 437篇 |
| 1975年 | 437篇 |
| 1974年 | 402篇 |
| 1973年 | 443篇 |
| 1971年 | 269篇 |
排序方式： 共有10000条查询结果，搜索用时 859 毫秒
161.
Valentin D. Ivanov G. Chauvin C. Foellmi M. Hartung N. Huélamo C. Melo D. Nürnberger M. Sterzik 《Astrophysics and Space Science》2006,304(1-4):247-249
The multiplicity of early-type stars is still not well established. The derived binary fraction is different for individual star forming regions, suggesting a connection with the age and the environment conditions. The few studies that have investigated this connection do not provide conclusive results. To fill in this gap, we started the first detailed adaptive-optic-assisted imaging survey of early-type field stars to derive their multiplicity in a homogeneous way. The sample has been extracted from the Hipparcos Catalog and consists of 341 BA-type stars within ∼300 pc from the Sun. We report the current status of the survey and describe a Monte-Carlo simulation that estimates the completeness of our companion detection. 相似文献
162.
163.
164.
We show how the Yarkovsky effect can be understood as a heat engine. The output of the engine, manifested in the rate of change in semimajor axis of the body, has a maximum at an intermediate heat capacity, depending on the rotation rate of the body. This maximum arises because the work output depends on the product of the solar heat absorbed by the body and transported from its morning to evening side (this am-pm heat flux increases with heat capacity) and the Carnot efficiency (which declines with heat capacity). 相似文献
165.
G. Djurašević P. Rovithis H. Rovithis-Livaniou E. Fragoulopoulou 《Astrophysics and Space Science》2005,296(1-4):311-314
BV light curves of the eclipsing binary UV Leo obtained at the Kryonerion Astronomical Station of the National Observatory of
Athens, Greece, are analyzed. The analysis is based on a Roche configuration with two spots on the secondary surface. The
elements of the two components of the system are calculated and the spot characteristics are given. 相似文献
166.
The paper models the suprathermal plasma as the concatenation of two different gravitating fluids each having its own separate density and pressure. One of the fluids has isotropic pressure while the other has an anisotropic pressure. The system is subjected to a uniform magnetic field which is frozen with the fluids. The gravitational instability of the model for low frequency plane waves has been investigated in a linear framework for plasma parameters relevant to the spiral arms of the galaxy and the cosmic gas clouds. The analysis shows that the wavelength of the instability is strongly dependent upon the anisotropy of the non-thermal plasma. 相似文献
167.
168.
169.