全文获取类型
收费全文 | 52669篇 |
免费 | 9127篇 |
国内免费 | 12666篇 |
专业分类
测绘学 | 5939篇 |
大气科学 | 6466篇 |
地球物理 | 9070篇 |
地质学 | 30175篇 |
海洋学 | 7893篇 |
天文学 | 3417篇 |
综合类 | 3786篇 |
自然地理 | 7716篇 |
出版年
2024年 | 364篇 |
2023年 | 1051篇 |
2022年 | 1994篇 |
2021年 | 2430篇 |
2020年 | 2316篇 |
2019年 | 2759篇 |
2018年 | 2054篇 |
2017年 | 2363篇 |
2016年 | 2491篇 |
2015年 | 2707篇 |
2014年 | 3245篇 |
2013年 | 3167篇 |
2012年 | 3378篇 |
2011年 | 3477篇 |
2010年 | 2983篇 |
2009年 | 3485篇 |
2008年 | 3426篇 |
2007年 | 3524篇 |
2006年 | 3430篇 |
2005年 | 3178篇 |
2004年 | 2752篇 |
2003年 | 2559篇 |
2002年 | 2237篇 |
2001年 | 2012篇 |
2000年 | 1906篇 |
1999年 | 1660篇 |
1998年 | 1479篇 |
1997年 | 1095篇 |
1996年 | 926篇 |
1995年 | 780篇 |
1994年 | 757篇 |
1993年 | 624篇 |
1992年 | 476篇 |
1991年 | 384篇 |
1990年 | 257篇 |
1989年 | 194篇 |
1988年 | 166篇 |
1987年 | 100篇 |
1986年 | 50篇 |
1985年 | 53篇 |
1984年 | 26篇 |
1983年 | 26篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 14篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1954年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
P. A. Patsis 《Monthly notices of the Royal Astronomical Society》2005,358(2):305-315
We investigate the morphological relation between the orbits of the central family of periodic orbits ( x 1 family) and the bar itself using models of test particles moving in a barred potential. We show that different bar morphologies may have as a backbone the same set of x 1 periodic orbits. We point out that by populating initially axisymmetric stellar discs exponentially with test particles in circular, or almost circular motion, we may end up with a response bar which reveals a shape different in crucial details from that of the individual stable x 1 orbits. For example, a bar model in which the x 1 orbits are pure ellipses may have a much more complicated response morphology. This depends on the particular invariant curves around x 1 , which are populated in each model. 相似文献
93.
国家重大科学工程项目LAMOST总控系统的程序设计是一个庞大的软件工程.其总控系统下共包括8个既相互独立又互有关联的子系统.如何通过良好的软件设计方法来处理好这8个子系统之间的关系使其协调运转,以及如何确保软件开发的可维护性、可持续性是研究重点. 相似文献
94.
95.
96.
对广西岩溶区三个铅锌硫化物矿床风化带观测结果表明,中低山岩溶区硫化物矿床具有更强烈的风化淋滤作用,但次生晕面积较小;岩溶平原区硫化物矿床风化与元素表生迁移特征较相似于非岩溶区的情况,表现在可产生较宽的pH偏低带和较大面积的次生晕 相似文献
97.
Andrew J. L. Harris Anna L. Butterworth Richard W. Carlton Ian Downey Peter Miller Pedro Navarro David A. Rothery 《Bulletin of Volcanology》1997,59(1):49-64
Satellite data offer a means of supplementing ground-based monitoring during volcanic eruptions, especially at times or locations
where ground-based monitoring is difficult. Being directly and freely available several times a day, data from the advanced
very high resolution radiometer (AVHRR) offers great potential for near real-time monitoring of all volcanoes across large
(3000×3000 km) areas. Herein we describe techniques to detect and locate activity; estimate lava area, thermal flux, effusion
rates and cumulative volume; and distinguish types of activity. Application is demonstrated using data for active lavas at
Krafla, Etna, Fogo, Cerro Negro and Erebus; a pyroclastic flow at Lascar; and open vent systems at Etna and Stromboli. Automated
near real-time analysis of AVHRR data could be achieved at existing, or cheap to install, receiving stations, offering a supplement
to conventional monitoring methods.
Received: 21 January 1997 / Accepted: 3 April 1997 相似文献
98.
V. Castellani S. Degl'Innocenti P. G. Prada Moroni 《Monthly notices of the Royal Astronomical Society》2001,320(1):66-72
We compare theoretical stellar models for main sequence (MS) stars with the Hipparcos data base for the Hyades cluster to give a warning against the uncritical use of available theoretical scenarios and to show how formal MS fittings can be fortuitous if not fictitious. Moreover, we find that none of the current theoretical scenarios appears able to account for an observed mismatch between theoretical predictions and observations of the coolest Hyades MS stars. Finally, we show that current theoretical models probably give too faint He burning luminosities unlike the case of less massive He burning models, with degenerate progenitors, which have been suggested to suffer the opposite discrepancy. 相似文献
99.
100.