全文获取类型
| 收费全文 | 24227篇 |
| 免费 | 1322篇 |
| 国内免费 | 796篇 |
专业分类
| 测绘学 | 1118篇 |
| 大气科学 | 765篇 |
| 地球物理 | 2023篇 |
| 地质学 | 2859篇 |
| 海洋学 | 787篇 |
| 天文学 | 17084篇 |
| 综合类 | 500篇 |
| 自然地理 | 1209篇 |
出版年
| 2024年 | 45篇 |
| 2023年 | 105篇 |
| 2022年 | 238篇 |
| 2021年 | 208篇 |
| 2020年 | 232篇 |
| 2019年 | 361篇 |
| 2018年 | 197篇 |
| 2017年 | 226篇 |
| 2016年 | 242篇 |
| 2015年 | 354篇 |
| 2014年 | 371篇 |
| 2013年 | 385篇 |
| 2012年 | 488篇 |
| 2011年 | 507篇 |
| 2010年 | 494篇 |
| 2009年 | 1856篇 |
| 2008年 | 1755篇 |
| 2007年 | 2107篇 |
| 2006年 | 2083篇 |
| 2005年 | 1846篇 |
| 2004年 | 1955篇 |
| 2003年 | 1727篇 |
| 2002年 | 1483篇 |
| 2001年 | 1306篇 |
| 2000年 | 1062篇 |
| 1999年 | 1015篇 |
| 1998年 | 1203篇 |
| 1997年 | 316篇 |
| 1996年 | 208篇 |
| 1995年 | 366篇 |
| 1994年 | 381篇 |
| 1993年 | 209篇 |
| 1992年 | 125篇 |
| 1991年 | 122篇 |
| 1990年 | 105篇 |
| 1989年 | 184篇 |
| 1988年 | 107篇 |
| 1987年 | 105篇 |
| 1986年 | 90篇 |
| 1985年 | 49篇 |
| 1984年 | 36篇 |
| 1983年 | 25篇 |
| 1982年 | 11篇 |
| 1980年 | 7篇 |
| 1979年 | 5篇 |
| 1977年 | 6篇 |
| 1954年 | 3篇 |
| 1905年 | 3篇 |
| 1900年 | 3篇 |
| 1897年 | 7篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
61.
62.
63.
64.
65.
66.
67.
68.
69.
Lu Sun 《国际地质力学数值与分析法杂志》2003,27(1):69-84
A closed‐form deflection response of a beam rest is presented in this paper using the integral transform method. The theory of linear partial differential equations is used to represent the deflection of beam subjected to a moving harmonic line load in integration form. The solution is finally carried out using the inverse Fourier transform. To evaluate the integration analytically, poles of the integrand are identified with the help of algebraic equation theory. Residue theorem is then utilized to represent the integration as a contour integral in the complex plane. Closed‐form deflections and numerical results are provided for different combinations of load frequency and velocity. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
70.
In the first paper of this series, we presented EBAS – Eclipsing Binary Automated Solver, a new fully automated algorithm to analyse the light curves of eclipsing binaries, based on the ebop code. Here, we apply the new algorithm to the whole sample of 2580 binaries found in the Optical Gravitational Lensing Experiment (OGLE) Large Magellanic Cloud (LMC) photometric survey and derive the orbital elements for 1931 systems. To obtain the statistical properties of the short-period binaries of the LMC, we construct a well-defined subsample of 938 eclipsing binaries with main-sequence B-type primaries. Correcting for observational selection effects, we derive the distributions of the fractional radii of the two components and their sum, the brightness ratios and the periods of the short-period binaries. Somewhat surprisingly, the results are consistent with a flat distribution in log P between 2 and 10 d. We also estimate the total number of binaries in the LMC with the same characteristics, and not only the eclipsing binaries, to be about 5000. This figure leads us to suggest that (0.7 ± 0.4) per cent of the main-sequence B-type stars in the LMC are found in binaries with periods shorter than 10 d. This frequency is substantially smaller than the fraction of binaries found by small Galactic radial-velocity surveys of B stars. On the other hand, the binary frequency found by Hubble Space Telescope ( HST ) photometric searches within the late main-sequence stars of 47 Tuc is only slightly higher and still consistent with the frequency we deduced for the B stars in the LMC. 相似文献