全文获取类型
| 收费全文 | 26290篇 |
| 免费 | 4647篇 |
| 国内免费 | 6410篇 |
专业分类
| 测绘学 | 1660篇 |
| 大气科学 | 5440篇 |
| 地球物理 | 4588篇 |
| 地质学 | 12713篇 |
| 海洋学 | 2850篇 |
| 天文学 | 5832篇 |
| 综合类 | 1775篇 |
| 自然地理 | 2489篇 |
出版年
| 2024年 | 131篇 |
| 2023年 | 463篇 |
| 2022年 | 903篇 |
| 2021年 | 1123篇 |
| 2020年 | 1179篇 |
| 2019年 | 1383篇 |
| 2018年 | 1061篇 |
| 2017年 | 1135篇 |
| 2016年 | 1178篇 |
| 2015年 | 1297篇 |
| 2014年 | 1790篇 |
| 2013年 | 1771篇 |
| 2012年 | 1808篇 |
| 2011年 | 1848篇 |
| 2010年 | 1776篇 |
| 2009年 | 2131篇 |
| 2008年 | 2050篇 |
| 2007年 | 2086篇 |
| 2006年 | 1893篇 |
| 2005年 | 1567篇 |
| 2004年 | 1403篇 |
| 2003年 | 1156篇 |
| 2002年 | 991篇 |
| 2001年 | 854篇 |
| 2000年 | 759篇 |
| 1999年 | 698篇 |
| 1998年 | 567篇 |
| 1997年 | 391篇 |
| 1996年 | 351篇 |
| 1995年 | 284篇 |
| 1994年 | 263篇 |
| 1993年 | 244篇 |
| 1992年 | 167篇 |
| 1991年 | 128篇 |
| 1990年 | 109篇 |
| 1989年 | 85篇 |
| 1988年 | 55篇 |
| 1987年 | 45篇 |
| 1986年 | 35篇 |
| 1985年 | 38篇 |
| 1984年 | 28篇 |
| 1983年 | 21篇 |
| 1982年 | 24篇 |
| 1981年 | 10篇 |
| 1980年 | 16篇 |
| 1979年 | 7篇 |
| 1978年 | 6篇 |
| 1977年 | 21篇 |
| 1976年 | 5篇 |
| 1954年 | 6篇 |
排序方式： 共有10000条查询结果，搜索用时 93 毫秒
131.
132.
133.
Lightning discharge generated in the protoplanetary nebula is viewed as a temporally isolated surge in the flow of electrically charged particles, similar to that of terrestrial lightning. If the current is intense enough, a powerful circular impulse magnetic field is generated around the instantaneous virtual electric conductor. Such magnetic field is capable of magnetizing dust grains containing ferromagnetic components present in its vicinity to their saturation levels. As a result, dust grains attract one another, forming the aggregates. This magnetically driven attraction suggests an important process possibly operational at an early stage of the planetary accretion. Based on both a classical model for electric conductor, and the theory of Lienard–Wiechert electromagnetic potentials, our calculations show that the magnetic impulse due to a discharge channel of a few cm in diameter transferring a charge of about 104 electrons reaches as high as 10 T. At these magnetic fields, the ferromagnetic dust grains, and possibly the already-formed larger aggregates as well, are easily magnetized to the saturation levels, producing compact clusters exhibiting permanent magnetic moments. 相似文献
134.
135.
136.
137.
138.
139.
Douglas P. Looze Markus Kasper Stefan Hippler Orhan Beker Robert Weiss 《Experimental Astronomy》2003,15(2):67-88
This paper develops a compensation algorithm based on Linear–Quadratic–Gaussian (LQG) control system design whose parameters
are determined (in part) by a model of the atmosphere. The model for the atmosphere is based on the open-loop statistics of
the atmosphere as observed by the wavefront sensor, and is identified from these using an auto-regressive, moving average
(ARMA) model. The (LQG) control design is compared with an existing compensation algorithm for a simulation developed at ESO
that represents the operation of MACAO adaptive optics system on the 8.2 m telescopes at Paranal, Chile.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
140.