首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   62933篇
  免费   758篇
  国内免费   410篇
测绘学   1869篇
大气科学   4598篇
地球物理   11933篇
地质学   24167篇
海洋学   4972篇
天文学   13557篇
综合类   257篇
自然地理   2748篇
  2021年   330篇
  2020年   373篇
  2019年   464篇
  2018年   3789篇
  2017年   3497篇
  2016年   2687篇
  2015年   792篇
  2014年   1157篇
  2013年   2050篇
  2012年   2240篇
  2011年   4138篇
  2010年   3802篇
  2009年   4434篇
  2008年   3660篇
  2007年   4229篇
  2006年   1742篇
  2005年   1755篇
  2004年   1637篇
  2003年   1609篇
  2002年   1474篇
  2001年   1118篇
  2000年   1055篇
  1999年   903篇
  1998年   891篇
  1997年   890篇
  1996年   713篇
  1995年   672篇
  1994年   626篇
  1993年   547篇
  1992年   478篇
  1991年   493篇
  1990年   468篇
  1989年   494篇
  1988年   428篇
  1987年   494篇
  1986年   444篇
  1985年   527篇
  1984年   646篇
  1983年   561篇
  1982年   554篇
  1981年   509篇
  1980年   455篇
  1979年   426篇
  1978年   440篇
  1977年   374篇
  1976年   340篇
  1975年   344篇
  1974年   323篇
  1973年   364篇
  1972年   252篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
963.
964.
965.
The history of the discovery of hot gas in galaxies is briefly reviewed, and the main properties of this gas described, emphasizing the need to refine these properties, in particular, the mass of the gas. It is proposed to do this via observations of the Sunyaev-Zel’dovich (SZ) effect due to hot gas in the coronas of elliptical galaxies. The absolute and relative perturbations of the spectrum of the cosmic microwave background (CMB) radiation due to scattering of the CMB photons by electrons with a Maxwellian energy distribution are calculated. The possibility of observing the SZ effect is demonstrated using three elliptical galaxies as examples. The kinematic SZ effect arising due to the peculiar motions and rotations of the galaxies is also accessible to observations. Together with X-ray data, such observations would enable refinement of the properties of gas in galaxies, and also yield additional information about the rotation of galaxies, possible accretion flows in the galactic gas, and hot galactic winds.  相似文献   
966.
We present the results of two-dimensional calculations of a magneto-rotational (MR) supernova explosion with a collapsing core for various core masses, rotational angular momenta, and magnetic-field configurations. It is shown that the MR mechanism produces an explosion energy that corresponds to observed values. The form of the explosion depends substantially on the initial configuration of the magnetic field. MR instability develops during the evolution of the magnetic field in an MR supernova explosion, resulting in an exponential increase of all components of the magnetic field, thereby substantially decreasing the time scale of the MR explosion. The energy of the supernova increases with the core’s mass and initial rotational energy.  相似文献   
967.
The Karalar galena-barite deposits are typical examples of the carbonate-hosted barite-galena deposits widely occurring in the Central Tauride Belt. These deposits are located in Permian limestones as ore veins along fault zones that are discordant to the bedding planes and as thin veinlets within hardly brecciated bottom zones of Permian limestones. The ore deposits contain mainly barite and galena and small amounts of sphalerite, pyrite, fahlore, limonite, quartz, and calcite. Barites occur during the earlier episode of mineralization and were mylonitized before the formation of galena. Galena and other minerals occur epigenetically with barite along porous zones between brecciated barite crystals and are especially abundant in the hardly mylonitized zones. Fluid inclusion studies indicate that the ore deposits of the area were developed by hydrothermal fluids with following characteristics: they contained NaCl, CaCl2, and MgCl2; the salinity of the fluids was relatively high and their temperature was low during the crystallization of barites in the earlier episode of mineralization; and the salinity of the fluids decreased and their temperature increased during the crystallization of sulfide minerals through the later episode of mineralization. δ18O and the δD results indicate that the water in the mineralizing fluid was of meteoric origin. The deposits were formed by deep meteoric water circulating through marine sediments. Shallow circulating and slightly warmed fluids dissolved Ba and sulfate from marine sediments of the basement and transported them to the mineralization environment during the early episode, while deep circulating and more heated fluids dissolved Pb, Zn, and other elements from the basement and reached the environment during the later episode of mineralization. The text was submitted by the authors in English.  相似文献   
968.
The REE distribution in minerals from tin-bearing ore-magmatic systems of the Russian Far East, including the Komsomolsk, Khingan, and Badzhal districts in the Amur region and the Kavalerovo, Lesozavodsk, Voznesenka, Furmanovo, and other districts in Primorsky krai, has been studied. The main attention was focused on tourmaline and chlorite; in addition, associated biotite, feldspar, apatite, fluorite, and carbonates were examined. The major factors affecting the REE distribution in the studied minerals are the temperature, Eh, and pH of the mineral-forming medium; crystal chemistry; partition coefficients of REE between fluid and minerals; and complexation that disturbs the coherent behavior of REE. Fluid evolution at different stages is characterized.  相似文献   
969.
Relations between indoor and soil gas radon were experimentally studied in villages of the Baikal region. On the basis of the obtained data, the soil-to-indoor radon ratio was calculated, which can be used for prediction of radon pollution in buildings of the same kind.  相似文献   
970.
The methods of celestial mechanics can be used to construct a mathematical model for the perturbed rotational motions of the deformable Earth that can adequately describe the astrometric measurements of the International Earth Rotation Service (IERS). This model describes the gravitational and tidal influences of the Sun and Moon. Fine resonant interactions of long-period zonal tides (annual, semiannual, monthly, and biweekly) with the diurnal and semidiurnal tides are revealed. These interactions can be reliably confirmed via a spectral analysis of the IERS data. Numerical modeling of tidal irregularities of the Earth’s axial rotation was carried out, focusing on the analysis and forecasting of variations of the day length occurring within short time intervals of a year or shorter (intrayear variations).  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号