全文获取类型
| 收费全文 | 82045篇 |
| 免费 | 14001篇 |
| 国内免费 | 17675篇 |
专业分类
| 测绘学 | 6664篇 |
| 大气科学 | 8751篇 |
| 地球物理 | 14807篇 |
| 地质学 | 48556篇 |
| 海洋学 | 8791篇 |
| 天文学 | 8062篇 |
| 综合类 | 5380篇 |
| 自然地理 | 12710篇 |
出版年
| 2024年 | 218篇 |
| 2023年 | 870篇 |
| 2022年 | 2419篇 |
| 2021年 | 2750篇 |
| 2020年 | 2724篇 |
| 2019年 | 3087篇 |
| 2018年 | 2549篇 |
| 2017年 | 2983篇 |
| 2016年 | 3075篇 |
| 2015年 | 3444篇 |
| 2014年 | 4313篇 |
| 2013年 | 4475篇 |
| 2012年 | 4747篇 |
| 2011年 | 5040篇 |
| 2010年 | 4301篇 |
| 2009年 | 5591篇 |
| 2008年 | 5358篇 |
| 2007年 | 5861篇 |
| 2006年 | 5755篇 |
| 2005年 | 5226篇 |
| 2004年 | 4798篇 |
| 2003年 | 4591篇 |
| 2002年 | 3957篇 |
| 2001年 | 3501篇 |
| 2000年 | 3382篇 |
| 1999年 | 3042篇 |
| 1998年 | 2749篇 |
| 1997年 | 2205篇 |
| 1996年 | 1864篇 |
| 1995年 | 1648篇 |
| 1994年 | 1609篇 |
| 1993年 | 1340篇 |
| 1992年 | 1049篇 |
| 1991年 | 744篇 |
| 1990年 | 638篇 |
| 1989年 | 503篇 |
| 1988年 | 375篇 |
| 1987年 | 255篇 |
| 1986年 | 170篇 |
| 1985年 | 117篇 |
| 1984年 | 57篇 |
| 1983年 | 48篇 |
| 1982年 | 44篇 |
| 1981年 | 36篇 |
| 1980年 | 31篇 |
| 1979年 | 34篇 |
| 1978年 | 49篇 |
| 1977年 | 30篇 |
| 1975年 | 6篇 |
| 1954年 | 25篇 |
排序方式： 共有10000条查询结果，搜索用时 203 毫秒
131.
132.
We present a new general scheme for calculating the structure and dynamics of radiation-pressure-driven photoionized flows. The new method goes one step beyond the Sobolev approximation. It involves a numerical solution of the radiative transfer in absorption lines, including the effects of differential expansion and line interactions such as line locking and blanketing. We also present a new scheme for calculating the radiation pressure due to trapped line photons in finite, differentially expanding flows. We compare our results for the radiation pressure force with those obtained using the Sobolev approximation and show the limitations of the latter. In particular, we demonstrate that the Sobolev method gives a poor approximation near discontinuity surfaces and its neglect of line blanketing can lead to erroneous results in high-velocity flows. We combine the newly calculated radiation pressure force with self-consistent photoionization and thermal calculations to study the dynamics and spectral features of broad absorption-line flows and highly ionized gas flows in active galactic nuclei (AGN). A comparison with Sobolev-type calculations shows that the latter overestimates the terminal velocity of the flow and, conversely, underestimates its opacity. We also show that line locking on broad emission lines can have a significant effect on the dynamics and spectral features of AGN flows. 相似文献
133.
134.
J. Dommanget 《Journal of Astrophysics and Astronomy》2003,24(3-4):99-109
A research that we conducted in 1963 on the evolution of the binaries based on the available orbital data to obtain a philosophical
degree, led to the establishment of an interesting and new diagram between the logarithm of the total mass and a particular
parameterX, bound to the areal constant. This appeared to have a real physical significance but the basic observational material was
insufficiently extended to assure its undeniable existence. In 1981, a new research based on a more extended orbital material,
has confirmed this diagram. Presently, another important increase in the orbital material and the availability of highly accurate
trigonometric parallaxes produced by the Hipparcos satellite, gave us the opportunity to confirm once more the stability of
this diagram. This last research is here described. 相似文献
135.
MENGLi-li 《中国地理科学(英文版)》2003,13(2):190-192
The exploitation and utilization of the tour resources of tournament athletics, including skiling, boat sail-ing, archery, ice engraving, snow engraving, has become a new trend of the development of Chinese tourism. Due tothe unique cold climate and superior geographic location, Harbin is a promising city for developing tour resources of tourna-ment athletics. Based on the analysis of the superiority and peculiarity of Harbin, the speculation on development of tour resources of tournament athletics in Harbin is proposed as follows : 1 ) Harbin should develop its special tour resources of tournament athletics associated with needs of market; 2) Harbin should take the advantages of rich resources and devel-op ice and snow entertainment in winter and travel for sight-seeing and spending summer;, 3) the adjustment of the layoutof ice and snow resources should be based on the idea of taking Harbin as the center and all-side opening at the largescale in the way of radiation; 4) tourism should be developed by the combined efforts of various departments to make feasi-ble plan, and the organizers should pay much attention to ensuring the safetv of tourists. 相似文献
136.
137.
138.
139.
140.