全文获取类型
收费全文 | 72201篇 |
免费 | 820篇 |
国内免费 | 503篇 |
专业分类
测绘学 | 1595篇 |
大气科学 | 4333篇 |
地球物理 | 14048篇 |
地质学 | 26186篇 |
海洋学 | 6712篇 |
天文学 | 16996篇 |
综合类 | 160篇 |
自然地理 | 3494篇 |
出版年
2022年 | 574篇 |
2021年 | 934篇 |
2020年 | 977篇 |
2019年 | 1111篇 |
2018年 | 2275篇 |
2017年 | 2081篇 |
2016年 | 2419篇 |
2015年 | 1126篇 |
2014年 | 2142篇 |
2013年 | 3754篇 |
2012年 | 2468篇 |
2011年 | 3168篇 |
2010年 | 2952篇 |
2009年 | 3605篇 |
2008年 | 3131篇 |
2007年 | 3335篇 |
2006年 | 3017篇 |
2005年 | 2049篇 |
2004年 | 1936篇 |
2003年 | 1897篇 |
2002年 | 1810篇 |
2001年 | 1698篇 |
2000年 | 1511篇 |
1999年 | 1150篇 |
1998年 | 1181篇 |
1997年 | 1222篇 |
1996年 | 956篇 |
1995年 | 961篇 |
1994年 | 906篇 |
1993年 | 811篇 |
1992年 | 776篇 |
1991年 | 761篇 |
1990年 | 799篇 |
1989年 | 740篇 |
1988年 | 705篇 |
1987年 | 780篇 |
1986年 | 658篇 |
1985年 | 871篇 |
1984年 | 927篇 |
1983年 | 848篇 |
1982年 | 768篇 |
1981年 | 791篇 |
1980年 | 702篇 |
1979年 | 624篇 |
1978年 | 656篇 |
1977年 | 620篇 |
1976年 | 551篇 |
1975年 | 542篇 |
1974年 | 535篇 |
1973年 | 571篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
In this paper the peculiarities of compiled oceanographic data sets, which consist primarily in the presence of some characteristic information as well as in the planned incomplete filling of the files with observations, are discussed. A number of special ways are suggested which essentially improve the packing density of computerized data without applying special archiving algorithms. The effectiveness of these methods has been tested by treating thein situ hydrological/chemical data file compiled in the Black Sea in 1988.Translated by Vladimir A. Puchkin. 相似文献
83.
M. V. Ramana 《Geo-Marine Letters》1986,6(1):1-5
Satellite imagery and offshore magnetic data were analysed to correlate regional tectonic elements on the inner continental
shelf off Konkan and the adjacent Deccan plateau. Three statistically important lineament trends—N-S, WNW-ESE and ENE-WSW—that
prevail on land are correlatable well with the offshore trends. This positive correlation suggests simultaneous deformation.
The major magnetic lineament observed off Jaigad Bay, west coast of India, may be the extension of onshore lineaments. The
correlation of both the offshore and onshore trends indicates that the fracture pattern of the crystalline basement has also
controlled the offshore structural pattern. 相似文献
84.
85.
86.
J. J. Quenby T. J Sumner S. D. Sidher S. Immler 《Astrophysics and Space Science》1994,216(1-2):213-217
The shadowing effects of the molecular clouds in the nearby interstellar medium on the soft x-ray background has been investigated, using ROSAT WFC data in conjunction with previous rocket B and C band surveys. Shadowing over a 5° extent occurs only for a few percent of the sky, but the mixed model of the ISM is supported.Detailed modelling of the Draco shadowing region shows little evidence for a multi-temperature, hot ISM component. 相似文献
87.
This study considers the influence of the effects of scattering due to Langmuir turbulent pulsations in the transfer of radiation in the spectral lines. The transfer equation of radiation in spectral lines, by taking into account scattering due to Langmuir turbulent pulsations, is written in a form convenient for application by numerical methods.The profile's intensity for a plane-parallel finite isothermal slab of a turbulent plasma in the case of complete redistribution of scattering by an atom are obtained. Numerical studies show that in this case with the broadening of spectral lines and the decreasing of self-reversal, the Langmuir frequency
pe is of the same order as the electronic Doppler width
De. Creation of the line satellites when
pe is larger than the line width is shown with the aid of numerical methods. 相似文献
88.
The laboratory simulation experiments on volatilization from the melts formed due to micrometeoroid impacts on the lunar surface were carried out. The simulation was performed using modulated laser pulses incident on rocks and minerals in vacuum; in so doing microcraters on the targets, glass particles, condensates were formed and gases solved in the bulk of the rock and mineral grains were released. It is shown that volatilization from only the crater glass layers is negligible, which fully confirms the theoretical predictions of Nussinov and Chernyak.The volatilizations from the drops formed by the micrometeoric impacts can be noticeable. For micron-sized drops, predominant among the others after the impact, the volatilization of Na, K and other volatiles can be up to 10 to 20%. For larger-sized (d102 m) drops the volatilization should lead to the appearance of the significant gradients of the element concentrations over the particle cross-section and as a result of their normalization it leads to the surface enrichment by some elements (Si and others).The mechanism of dust formation due to the surface rocks attack by volatilizing alkaline metals (Naughtonet al.) on the Moon probably is not effective. It is the consequence of such a fact that the condensate of the target materials evaporated due to other simultaneous micrometeoric impacts and had the same (as the target has) elemental composition is the very strong background for volatilizing and condensating alkaline elements.Preliminary conclusions about a possible correlation between the composition and the sizes of dust particles in the Solar system and in the Universe (at similar initial composition) have been drawn. 相似文献
89.
90.
D. D. Barbosa 《Solar physics》1978,56(1):55-66
We have computed the surface Green's function for linear force-free magnetic fields, where × B = B and is a constant, for application to low coronal levels of the solar atmosphere. Boundary conditions are imposed on the normal component of B on two parallel planes which delineate the force-free volume. This procedure ensures that the magnetic field energy remains bounded, and that the field lines have a smooth behavior. A simple bipolar source distribution is treated and representative field line tracings are shown. 相似文献