全文获取类型
收费全文 | 15630篇 |
免费 | 1616篇 |
国内免费 | 1840篇 |
专业分类
测绘学 | 5172篇 |
大气科学 | 2035篇 |
地球物理 | 2194篇 |
地质学 | 3053篇 |
海洋学 | 1220篇 |
天文学 | 2637篇 |
综合类 | 1410篇 |
自然地理 | 1365篇 |
出版年
2024年 | 91篇 |
2023年 | 208篇 |
2022年 | 473篇 |
2021年 | 613篇 |
2020年 | 624篇 |
2019年 | 679篇 |
2018年 | 480篇 |
2017年 | 765篇 |
2016年 | 695篇 |
2015年 | 716篇 |
2014年 | 832篇 |
2013年 | 1002篇 |
2012年 | 895篇 |
2011年 | 822篇 |
2010年 | 662篇 |
2009年 | 905篇 |
2008年 | 909篇 |
2007年 | 1094篇 |
2006年 | 991篇 |
2005年 | 836篇 |
2004年 | 837篇 |
2003年 | 619篇 |
2002年 | 547篇 |
2001年 | 475篇 |
2000年 | 392篇 |
1999年 | 357篇 |
1998年 | 328篇 |
1997年 | 187篇 |
1996年 | 173篇 |
1995年 | 169篇 |
1994年 | 146篇 |
1993年 | 116篇 |
1992年 | 91篇 |
1991年 | 70篇 |
1990年 | 49篇 |
1989年 | 47篇 |
1988年 | 36篇 |
1987年 | 22篇 |
1986年 | 26篇 |
1985年 | 14篇 |
1984年 | 17篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1977年 | 11篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1971年 | 5篇 |
1954年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
We present the excitation energies and lifetimes for the 3 s 3 p 3 d 4 F 7/2,9/2 levels for five aluminium-like ions of the iron group. Apart from the wavelengths, this also includes the transition probabilities and branching ratios for the electric-dipole allowed (E1) and forbidden (M1, E2, M2) lines into the energetically lower lying levels of the 3 s 2 3 d , 3 s 3 p 2 and 3 s 3 p 3 d configurations. Applying systematically enlarged multiconfiguration Dirac–Fock (MCDF) wavefunctions, here the effects of relativity and the electron–electron correlation are treated within the same (computational) model. 相似文献
74.
75.
76.
77.
Hari Om Vats M. R. Deshpande K. N. Iyer Tetsuro Kondo Takeshi Isobe 《Astrophysics and Space Science》1996,243(1):251-254
This article describes the observations of a type III radio burst observed at 103 MHz simultaneously by the two radio telescopes situated at Rajkot (22.3°N, 70.7°E) and Thaltej (23°N, 72.4°E). This event occurred on September 30, 1993 at about 0430 UT and lasted for only half a minute. The event consisted of several sharp spikes in a group. The rise and fall time of these are comparable, however the peaks of individual spikes varied by a factor of four. The comparison of these observations with the data of solar radio spectrograph HiRAS indicates that this was a metric radio burst giving highest emission at about 103 MHz. 相似文献
78.
E. Biémont P. Palmeri P. Quinet G. Paquin Z. G. Zhang G. Somesfalean S. Svanberg 《Monthly notices of the Royal Astronomical Society》2001,328(4):1085-1090
Lifetimes of six levels belonging to the 4f10 6p configuration of Ho iii have been measured for the first time using the time-resolved laser-induced fluorescence method. They are compared with multiconfigurational pseudo-relativistic Hartree–Fock calculations. A very good agreement is found. Using the experimental lifetimes and theoretical branching fractions, a first set of transition probabilities of astrophysical interest has been obtained for this ion. 相似文献
79.
80.
Using a set of compilations of measurements for extragalactic radio sources, we construct all-sky maps of the Faraday rotation produced by the Galactic magnetic field. In order to generate the maps, we treat the radio source positions as a kind of 'mask' and construct combinations of spherical harmonic modes that are orthogonal on the masked sky. As long as relatively small multipoles are used, the resulting maps are quite stable to changes in the selection criteria for the sources, and show clearly the structure of the local Galactic magnetic field. We also suggest the use of these maps as templates for cosmic microwave background (CMB) foreground analysis, illustrating the idea with a cross-correlation analysis between the Wilkinson Microwave Anisotropy Probe ( WMAP ) data and our maps. We find a significant cross-correlation, indicating the presence of a significant residual contamination. 相似文献