全文获取类型
收费全文 | 104174篇 |
免费 | 1731篇 |
国内免费 | 710篇 |
专业分类
测绘学 | 2326篇 |
大气科学 | 7062篇 |
地球物理 | 20222篇 |
地质学 | 37646篇 |
海洋学 | 9444篇 |
天文学 | 23658篇 |
综合类 | 258篇 |
自然地理 | 5999篇 |
出版年
2022年 | 686篇 |
2021年 | 1185篇 |
2020年 | 1267篇 |
2019年 | 1389篇 |
2018年 | 2917篇 |
2017年 | 2738篇 |
2016年 | 3202篇 |
2015年 | 1643篇 |
2014年 | 3109篇 |
2013年 | 5487篇 |
2012年 | 3384篇 |
2011年 | 4409篇 |
2010年 | 3982篇 |
2009年 | 5036篇 |
2008年 | 4391篇 |
2007年 | 4490篇 |
2006年 | 4206篇 |
2005年 | 3041篇 |
2004年 | 2967篇 |
2003年 | 2765篇 |
2002年 | 2743篇 |
2001年 | 2444篇 |
2000年 | 2373篇 |
1999年 | 1912篇 |
1998年 | 1942篇 |
1997年 | 1862篇 |
1996年 | 1578篇 |
1995年 | 1570篇 |
1994年 | 1367篇 |
1993年 | 1262篇 |
1992年 | 1210篇 |
1991年 | 1218篇 |
1990年 | 1219篇 |
1989年 | 1068篇 |
1988年 | 1019篇 |
1987年 | 1161篇 |
1986年 | 1013篇 |
1985年 | 1264篇 |
1984年 | 1376篇 |
1983年 | 1367篇 |
1982年 | 1268篇 |
1981年 | 1168篇 |
1980年 | 1098篇 |
1979年 | 1014篇 |
1978年 | 964篇 |
1977年 | 844篇 |
1976年 | 841篇 |
1975年 | 816篇 |
1974年 | 804篇 |
1973年 | 853篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
22.
Zsolt Sándor Bálint Érdi Carl D. Murray 《Celestial Mechanics and Dynamical Astronomy》2002,84(4):355-368
The dynamics of co-orbital motion in the restricted three-body problem are investigated by symplectic mappings. Analytical and semi-numerical mappings have been developed and studied in detail. The mappings have been tested by numerical integration of the equations of motion. These mappings have been proved to be useful for a quick determination of the phase space structure reflecting the main characteristics of the dynamics of the co-orbital problem. 相似文献
23.
24.
25.
Measurement of variations in the radial velocities of stars due to the reflex orbital motion of the star around the planetary-system barycenter constitutes a powerful method of searching for substellar or planetary mass companions. After several years of patient data acquisition, radial-velocity searches for planetary systems around other stars are now beginning to bear fruit. In late 1995 and early 1996, three candidate systems were announced with Jovian-mass planets around solar-type stars. The current paradigm for low-mass star formation suggests that planetary systems should be able to form in the circumstellar disks surrounding young stellar objects. These newly discovered systems, and other discoveries which will soon follow them, will test critically our understanding of the processes of star- and planet-formation. We review the techniques used in these radial-velocity searches and their results to date. We then discuss planned improvements in the surveys, and the prospects for the next 20 years. 相似文献
26.
H. A. Harutyunian 《Astrophysics》1996,39(4):370-374
The Voigt function and its derivatives are represented by means of series in Hermite polynomials. The equations obtained can be used both for numerical calculations of these functions and for analytical research.Translated from Astrofizika, Vol. 39, No. 4, pp. 619–625, October–December, 1996. 相似文献
27.
28.
M. J. Freyberg H. Bräuninger W. Burkert G. D. Hartner O. Citterio F. Mazzoleni G. Pareschi D. Spiga S. Romaine P. Gorenstein B. D. Ramsey 《Experimental Astronomy》2005,20(1-3):405-412
The Max-Planck-Institut für extraterrestrische Physik (MPE) in Garching, Germany, uses its large X-ray beam line facility PANTER for testing X-ray astronomical instrumentation. A number of telescopes, gratings, filters, and detectors, e.g. for astronomical satellite missions like Exosat, ROSAT, Chandra (LETG), BeppoSAX, SOHO (CDS), XMM-Newton, ABRIXAS, Swift (XRT), have been successfully calibrated in the soft X-ray energy range (< 15keV). Moreover, measurements with mirror test samples for new missions like ROSITA and XEUS have been carried out at PANTER. Here we report on an extension of the energy range, enabling calibrations of hard X-ray optics over the energy range 15–50 keV. Several future X-ray astronomy missions (e.g., Simbol-X, Constellation-X, XEUS) have been proposed, which make use of hard X-ray optics based on multilayer coatings. Such optics are currently being developed by the Osservatorio Astronomico di Brera (OAB), Milano, Italy, and the Harvard-Smithsonian Center for Astrophysics (CfA), Cambridge, MA, USA. These optics have been tested at the PANTER facility with a broad energy band beam (up to 50 keV) using the XMM-Newton EPIC-pn flight spare CCD camera with its good intrinsic energy resolution, and also with monochromatic X-rays between C-K (0.277 keV) and Cu-Kα (8.04 keV).
PACS: 95.55.Ka, 95.55.Aq, 41 50.+h, 07.85.Fv 相似文献
29.