全文获取类型
| 收费全文 | 29070篇 |
| 免费 | 4860篇 |
| 国内免费 | 7427篇 |
专业分类
| 测绘学 | 4376篇 |
| 大气科学 | 6587篇 |
| 地球物理 | 5837篇 |
| 地质学 | 10724篇 |
| 海洋学 | 3901篇 |
| 天文学 | 4138篇 |
| 综合类 | 2072篇 |
| 自然地理 | 3722篇 |
出版年
| 2024年 | 129篇 |
| 2023年 | 319篇 |
| 2022年 | 874篇 |
| 2021年 | 1053篇 |
| 2020年 | 1220篇 |
| 2019年 | 1444篇 |
| 2018年 | 1186篇 |
| 2017年 | 1365篇 |
| 2016年 | 1430篇 |
| 2015年 | 1606篇 |
| 2014年 | 1703篇 |
| 2013年 | 1964篇 |
| 2012年 | 1815篇 |
| 2011年 | 1864篇 |
| 2010年 | 1482篇 |
| 2009年 | 1975篇 |
| 2008年 | 1947篇 |
| 2007年 | 2097篇 |
| 2006年 | 1998篇 |
| 2005年 | 1849篇 |
| 2004年 | 1711篇 |
| 2003年 | 1481篇 |
| 2002年 | 1298篇 |
| 2001年 | 1154篇 |
| 2000年 | 1056篇 |
| 1999年 | 946篇 |
| 1998年 | 979篇 |
| 1997年 | 611篇 |
| 1996年 | 526篇 |
| 1995年 | 487篇 |
| 1994年 | 446篇 |
| 1993年 | 360篇 |
| 1992年 | 225篇 |
| 1991年 | 197篇 |
| 1990年 | 127篇 |
| 1989年 | 96篇 |
| 1988年 | 90篇 |
| 1987年 | 56篇 |
| 1986年 | 34篇 |
| 1985年 | 35篇 |
| 1984年 | 24篇 |
| 1983年 | 7篇 |
| 1982年 | 14篇 |
| 1981年 | 16篇 |
| 1980年 | 11篇 |
| 1979年 | 9篇 |
| 1978年 | 9篇 |
| 1977年 | 7篇 |
| 1973年 | 6篇 |
| 1954年 | 10篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
11.
12.
Roberto F. Viotti Lucio Angelo Antonelli Sonja Rebecchi Corinne Rossi 《Journal of Astrophysics and Astronomy》2002,23(1-2):19-22
We have investigated with BeppoSAX the long term behaviour of the harder X-ray component of the supposed supermassive binary
system η Car along its 5.52 year cycle. We have found that in March 1998 during egress from the last December 1997 eclipse,
this component was the same as outside eclipse, but for a large (×3.5) increase of NH
h
, that can be attributed to the presence or formation of opaque matter in front of the source near periastron. Unexpectedly,
at that time the iron 6.7 keV emission line was 40% stronger. BeppoSAX has for the first time found ahard X-ray tail extending to at least 50 keV, that cannot be adequately fitted with an additional hotter thermal component. The 2–100 keV
spectrum of η Car is instead well fitted with an absorbed powerlaw spectrum with photon index 2.53, suggesting non-thermal
emission as an alternative model for the core source. 相似文献
13.
14.
15.
16.
A wide-field time-series CCD photometric survey of variable stars in the field of the open cluster NGC 2168 was carried out using the BATC Schmidt telescope. In total 13 new variable stars are discovered with three W UMa systems, one EA type and two EB type eclipsing binaries (one of them could be a W UMa system), and seven pulsating stars including three candidates of δScuti stars. 相似文献
17.
18.
19.
本文对Ｏｓｈｅｒｏｖｉｃｈ的黑子返回磁通量模型作了适当的修改，使用黑子中心作为边界条件，用五种观测结果，导出了理论模型所需的五个主要参量，用半经验方法求得了黑子静力学模型的磁场、压力和温度等物理量．将此模型应用于一个中等大小的圆形对称黑子，可得到一个特解，结果发现我们的模型既能满足黑子的磁性质，同时又能满足合理的热力学量分布． 相似文献
20.
Sergei A. Klioner 《Celestial Mechanics and Dynamical Astronomy》1996,66(4):345-363
Intermediate orbit for general planetary theory is constructed in the form of multivariate Fourier series with numerical coefficients. The structure and efficiency of the derived series are illustrated by giving various statistical properties of the coefficients.The ability of the recently proposed elliptic function approach to compress the Fourier series representing the intermediate orbit is investigated. Our results confirm that when mutual perturbations of a pair of planets are considered the elliptic function approach is quite efficient and allows one to compress the series substantially. However, when perturbations of three or more planets are under study the elliptic function approach does not give any advantages. 相似文献