全文获取类型
| 收费全文 | 4746篇 |
| 免费 | 319篇 |
| 国内免费 | 263篇 |
专业分类
| 测绘学 | 152篇 |
| 大气科学 | 128篇 |
| 地球物理 | 452篇 |
| 地质学 | 851篇 |
| 海洋学 | 218篇 |
| 天文学 | 2893篇 |
| 综合类 | 63篇 |
| 自然地理 | 571篇 |
出版年
| 2024年 | 26篇 |
| 2023年 | 37篇 |
| 2022年 | 72篇 |
| 2021年 | 79篇 |
| 2020年 | 72篇 |
| 2019年 | 127篇 |
| 2018年 | 59篇 |
| 2017年 | 66篇 |
| 2016年 | 74篇 |
| 2015年 | 86篇 |
| 2014年 | 129篇 |
| 2013年 | 149篇 |
| 2012年 | 145篇 |
| 2011年 | 181篇 |
| 2010年 | 122篇 |
| 2009年 | 416篇 |
| 2008年 | 362篇 |
| 2007年 | 447篇 |
| 2006年 | 411篇 |
| 2005年 | 359篇 |
| 2004年 | 314篇 |
| 2003年 | 314篇 |
| 2002年 | 226篇 |
| 2001年 | 202篇 |
| 2000年 | 157篇 |
| 1999年 | 159篇 |
| 1998年 | 182篇 |
| 1997年 | 61篇 |
| 1996年 | 52篇 |
| 1995年 | 46篇 |
| 1994年 | 33篇 |
| 1993年 | 36篇 |
| 1992年 | 29篇 |
| 1991年 | 14篇 |
| 1990年 | 19篇 |
| 1989年 | 13篇 |
| 1988年 | 8篇 |
| 1987年 | 12篇 |
| 1986年 | 11篇 |
| 1985年 | 6篇 |
| 1984年 | 4篇 |
| 1982年 | 5篇 |
| 1981年 | 1篇 |
| 1980年 | 1篇 |
| 1979年 | 1篇 |
| 1977年 | 1篇 |
| 1971年 | 2篇 |
排序方式： 共有5328条查询结果，搜索用时 15 毫秒
71.
72.
73.
Dong-Mei Qin Ping Guo Zhan-Yi Hu Yong-Heng ZhaoNational Laboratory of Pattern Recognition Laboratory Institute of Automation Chinese Academy of Sciences Beijing dmqin@nlpr.ia.ac.cnDepartment of Computer Sciences Beijing Normal University Beijing National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2003,3(3)
For LAMOST, the largest sky survey program in China, the solution of the problem of automatic discrimination of stars from galaxies by spectra has shown that the results of the PSF test can be significantly refined. However, the problem is made worse when the redshifts of galaxies are not available. We present a new automatic method of star/(normal) galaxy separation, which is based on Statistical Mixture Modeling with Radial Basis Function Neural Networks (SMM-RBFNN). This work is a continuation of our previous one, where active and non-active celestial objects were successfully segregated. By combining the method in this paper and the previous one, stars can now be effectively separated from galaxies and AGNs by their spectra-a major goal of LAMOST, and an indispensable step in any automatic spectrum classification system. In our work, the training set includes standard stellar spectra from Jacoby's spectrum library and simulated galaxy spectra of EO, SO, Sa, Sb types with redshift ranging from 0 to 1 相似文献
74.
75.
76.
77.
78.
79.
80.
J. P. Bernstein † Suketu P. Bhavsar ‡ 《Monthly notices of the Royal Astronomical Society》2001,322(3):625-630
The brightest, or first-ranked, galaxies (BCGs) in rich clusters show a very small dispersion in luminosity, making them excellent standard candles. This small dispersion raises questions about the nature of BCGs. Are they simply the extremes of normal galaxies formed via a stochastic process, or do they belong to a special class of atypical objects? If they do, are all BCGs special, or do normal galaxies compete for the first rank? To answer these questions, we undertake a statistical study of BCG magnitudes using results from extreme value theory. Two-population models do better than one-population models. A simple scenario where a random boost in the magnitude of a fraction of bright normal galaxies forms a class of atypical galaxies best describes the observed distribution of BCG magnitudes. 相似文献