全文获取类型
收费全文 | 29270篇 |
免费 | 2766篇 |
国内免费 | 2060篇 |
专业分类
测绘学 | 1186篇 |
大气科学 | 1224篇 |
地球物理 | 4038篇 |
地质学 | 6869篇 |
海洋学 | 1175篇 |
天文学 | 17397篇 |
综合类 | 869篇 |
自然地理 | 1338篇 |
出版年
2024年 | 81篇 |
2023年 | 172篇 |
2022年 | 366篇 |
2021年 | 382篇 |
2020年 | 405篇 |
2019年 | 565篇 |
2018年 | 369篇 |
2017年 | 388篇 |
2016年 | 448篇 |
2015年 | 616篇 |
2014年 | 701篇 |
2013年 | 761篇 |
2012年 | 829篇 |
2011年 | 853篇 |
2010年 | 755篇 |
2009年 | 2231篇 |
2008年 | 2071篇 |
2007年 | 2488篇 |
2006年 | 2413篇 |
2005年 | 2139篇 |
2004年 | 2221篇 |
2003年 | 1955篇 |
2002年 | 1705篇 |
2001年 | 1516篇 |
2000年 | 1332篇 |
1999年 | 1271篇 |
1998年 | 1398篇 |
1997年 | 527篇 |
1996年 | 430篇 |
1995年 | 493篇 |
1994年 | 503篇 |
1993年 | 311篇 |
1992年 | 227篇 |
1991年 | 179篇 |
1990年 | 188篇 |
1989年 | 222篇 |
1988年 | 154篇 |
1987年 | 128篇 |
1986年 | 99篇 |
1985年 | 51篇 |
1984年 | 35篇 |
1983年 | 25篇 |
1982年 | 10篇 |
1981年 | 4篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1954年 | 10篇 |
1897年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Zhan-Le Du Hua-Ning Wang Xiang-Tao He National Astronomical Observatories Chinese Academy of Sciences Beijing Department of Astronomy Beijing Normal University Beijing 《中国天文和天体物理学报》2006,6(4):489-494
The maximum amplitudes of solar activity cycles are found to be well anti-correlated (r = -0.72) with the newly defined solar cycle lengths three cycles before (at lag -3) in 13-month running mean sunspot numbers during the past 190 years. This result could be used for predicting the maximum sunspot numbers. The amplitudes of Cycles 24 and 25 are estimated to be 149.5±27.6 and 144.3±27.6, respectively. 相似文献
62.
Xie Rui-xiang Wang Min Shi Shuo-biao Xu Chun Li Wei-hua Yan Yi-hua 《Chinese Astronomy and Astrophysics》2003,27(4):426-434
Using the decimetric (700–1500 MHz) radio spectrometer and the synchronous observational system with high temporal resolution at four frequencies (1420, 2130, 2840 and 4260 MHz) of Yunnan Observatory, two rare events were observed on 2001 June 24 and 1990 July 30. The former was a small radio burst exhibiting pulsations with short periods (about 29, 40 and 100 ms) in the impulsive phase. The latter was a large radio burst, which at 2840 MHz produced radio pulsations with period of about 30 ms. This paper focuses on pulsations with very short periods in the range of 29–40 ms. The mechanism of generation of such pulsations may be modulation of radio radiation by the periodic trains of whistler packets originating in unstable regions of the corona. Alternatively, these pulsations can be attributed to wave-wave non-linear interactions of electrostatic upper hybrid waves driven by beams of precipitating electrons in flaring loops. 相似文献
63.
Nikos Prantzos 《Astrophysics and Space Science》2003,284(2):675-684
We develop a detailed model of the Milky Way (a `prototypical' disk galaxy) and extend it to other disks with the help of
some simple scaling relations, obtained in the framework of Cold Dark Matter models. This phenomenological (`hybrid') approach
to the study of disk galaxy evolution allows us to reproduce successfully a large number of observed properties of disk galaxies
in the local Universe and up to redshift z ∼ 1. The important conclusion is that, on average, massive disks have formed the bulk of their stars earlier than their lower
mass counterparts: the `star formation hierarchy' has been apparently opposite to the `dark matter assembly' hierarchy. It
is not yet clear whether `feedback' (as used in semi-analytical models of galaxy evolution) can explain that discrepancy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
64.
65.
66.
67.
68.
69.
70.