全文获取类型
| 收费全文 | 15136篇 |
| 免费 | 1665篇 |
| 国内免费 | 1849篇 |
专业分类
| 测绘学 | 5259篇 |
| 大气科学 | 2162篇 |
| 地球物理 | 2389篇 |
| 地质学 | 3156篇 |
| 海洋学 | 1264篇 |
| 天文学 | 1236篇 |
| 综合类 | 1458篇 |
| 自然地理 | 1726篇 |
出版年
| 2024年 | 69篇 |
| 2023年 | 151篇 |
| 2022年 | 455篇 |
| 2021年 | 586篇 |
| 2020年 | 610篇 |
| 2019年 | 699篇 |
| 2018年 | 478篇 |
| 2017年 | 826篇 |
| 2016年 | 718篇 |
| 2015年 | 732篇 |
| 2014年 | 848篇 |
| 2013年 | 1086篇 |
| 2012年 | 928篇 |
| 2011年 | 875篇 |
| 2010年 | 662篇 |
| 2009年 | 870篇 |
| 2008年 | 929篇 |
| 2007年 | 1086篇 |
| 2006年 | 972篇 |
| 2005年 | 792篇 |
| 2004年 | 742篇 |
| 2003年 | 564篇 |
| 2002年 | 489篇 |
| 2001年 | 425篇 |
| 2000年 | 350篇 |
| 1999年 | 307篇 |
| 1998年 | 238篇 |
| 1997年 | 173篇 |
| 1996年 | 169篇 |
| 1995年 | 153篇 |
| 1994年 | 135篇 |
| 1993年 | 128篇 |
| 1992年 | 81篇 |
| 1991年 | 71篇 |
| 1990年 | 43篇 |
| 1989年 | 46篇 |
| 1988年 | 34篇 |
| 1987年 | 20篇 |
| 1986年 | 19篇 |
| 1985年 | 12篇 |
| 1984年 | 12篇 |
| 1982年 | 8篇 |
| 1981年 | 6篇 |
| 1980年 | 6篇 |
| 1979年 | 4篇 |
| 1977年 | 11篇 |
| 1973年 | 4篇 |
| 1972年 | 4篇 |
| 1971年 | 5篇 |
| 1954年 | 6篇 |
排序方式： 共有10000条查询结果，搜索用时 281 毫秒
11.
12.
13.
空间数据仓库的认知过程 总被引：3，自引：3，他引：0
从理论上探讨了空间数据仓库的认知过程．主要是十一个层次的世界模型通过十个算子转换的过程，对十一个层次世界及十个算子概念进行了较详细地讨论，并用代数系统对其进行了定义。 相似文献
14.
利用钻孔测井资料并运用地层倾角测量信息分析法，给出了江汉盆地地应力最大水平主压应力方向为ＮＥ６０～６５° 相似文献
15.
O. Tamuz T. Mazeh S. Zucker † 《Monthly notices of the Royal Astronomical Society》2005,356(4):1466-1470
We suggest a new algorithm to remove systematic effects in a large set of light curves obtained by a photometric survey. The algorithm can remove systematic effects, such as those associated with atmospheric extinction, detector efficiency, or point spread function changes over the detector. The algorithm works without any prior knowledge of the effects, as long as they linearly appear in many stars of the sample. The approach, which was originally developed to remove atmospheric extinction effects, is based on a lower rank approximation of matrices, an approach which has already been suggested and used in chemometrics, for example. The proposed algorithm is especially useful in cases where the uncertainties of the measurements are unequal. For equal uncertainties, the algorithm reduces to the Principal Component Analysis (PCA) algorithm. We present a simulation to demonstrate the effectiveness of the proposed algorithm and we point out its potential, in the search for transit candidates in particular. 相似文献
16.
17.
H. L. Xu S. Svanberg R. D. Cowan P.-H. Lefèbvre P. Quinet E. Biémont 《Monthly notices of the Royal Astronomical Society》2003,346(2):433-440
Radiative lifetime measurements were performed with time-resolved laser-induced fluorescence techniques for 24 levels of Nd ii in the energy range 20 500–32 500 cm−1 . For 17 levels, no previous experimental data exist. These results have allowed the testing of new theoretical calculations with the relativistic Hartree–Fock method taking configuration interactions and core-polarization effects into account, and a satisfying agreement has been found for this complex ion. A new set of calculated oscillator strengths, accurate within a few per cent for the strongest transitions, is presented for 107 lines of astrophysical interest appearing in the wavelength range 358.0–1100.0 nm. These results will be useful to evaluate abundance values of neodymium in chemically peculiar stars in relation with cosmochronology. 相似文献
18.
19.
The results of a photometric monitoring of the quasar 4C 38.41, performed at the optical R and B bands in 2002 February–March, are presented. With a 60/90 cm Schmidt telescope at the Xinglong station of the National Astronomical Observatories of China, we observed the source exhibiting amplitude variations of up to 0.78 mag in both bands during the whole campaign. Intraday and even intranight variations are detected as well. A typical variability time-scale of about 36 d is derived from our 2-month observations at the optical bands, which is identical to that found at a radio wavelength of 92 cm, suggesting a common origin for the variations in 4C 38.41 from optical to radio bands. 相似文献
20.