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   23397篇
  免费   247篇
  国内免费   137篇
测绘学   371篇
大气科学   1232篇
地球物理   4445篇
地质学   9238篇
海洋学   2282篇
天文学   5301篇
综合类   41篇
自然地理   871篇
  2022年   267篇
  2021年   435篇
  2020年   401篇
  2019年   468篇
  2018年   959篇
  2017年   871篇
  2016年   901篇
  2015年   376篇
  2014年   788篇
  2013年   1317篇
  2012年   926篇
  2011年   1108篇
  2010年   1075篇
  2009年   1229篇
  2008年   1058篇
  2007年   1227篇
  2006年   1081篇
  2005年   584篇
  2004年   545篇
  2003年   557篇
  2002年   569篇
  2001年   520篇
  2000年   416篇
  1999年   340篇
  1998年   329篇
  1997年   333篇
  1996年   260篇
  1995年   269篇
  1994年   239篇
  1993年   185篇
  1992年   215篇
  1991年   189篇
  1990年   202篇
  1989年   190篇
  1988年   161篇
  1987年   188篇
  1986年   174篇
  1985年   215篇
  1984年   204篇
  1983年   205篇
  1982年   195篇
  1981年   175篇
  1980年   167篇
  1979年   188篇
  1978年   165篇
  1977年   145篇
  1976年   137篇
  1975年   142篇
  1974年   127篇
  1973年   174篇
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
851.
This paper presents a summary of the quantitative substantiation for four main patterns relating to the changes in the chemical composition of mine waters in Eastern Donbas. The patterns and their origin and impact on the environment are characterized. This makes it possible to solve current practical and theoretical issues: to predict the main components of the environmental contamination, develop standards for treatment facilities, and forecast the transformation in the composition of surface waters, ground waters, and mine waters, and to solve successfully other ecological issues in Eastern Donbas.  相似文献   
852.
Obtained data shows that high-potassic dyke rocks of the Ryabinoviy massif (Central Aldan) belong to low-titanium lamproite series (Mediterranean type) and are distinct with “classic” high-titanium lamproites. Based on Al-in-olivine thermometer, temperature of olivine–chrome-spinel pair crystallization varies in range between 1100 and 1250°C. This suggests lithospheric mantle source for the parental melt and makes role of mantle plume insignificant. High-precision data on olivine composition and bulk rock traceelement composition imply mixed source for the parental melt, consisted of depleted peridotite and enriched domains, originated during ancient subduction.  相似文献   
853.
854.
The main trends of water dissolution in Fe-bearing olivine have been investigated in the olivine–H2O–hydrocarbon fluid system in experiments at a pressure of 6.3 GPa, a temperature of 1200°C, and hydrogen fugacity ( fH2) buffered by the Mo–MoO2 equilibrium. The content and contribution of ОH defects of different types in Fe-bearing olivines depend on the composition of reduced fluids in the system. As the fraction of hydrocarbons in the fluid increases, the H2O content in olivine crystals decreases from 900 to 160–180 ppm, while the ОН absorption peaks become lower at high frequencies and occupy a larger part of the infrared spectrum in the low-frequency region. According to the experimental results, even the deepest seated mantle olivines with OH defects were not equilibrated with a fluid rich in light alkanes or oxygenated hydrocarbons.  相似文献   
855.
Fishchenko  V. K.  Dolgikh  G. I.  Zimin  P. S.  Subote  A. E. 《Doklady Earth Sciences》2018,482(1):1244-1247

The design features of an oceanological video-monitoring system created for operational research of coastal infrasonic wave processes are described. The results obtained confirm great opportunities for its use in fundamental and applied works in various seasons. The processing of the obtained experimental data has revealed the dynamics of the wave processes starting from wind waves to diurnal tides.

  相似文献   
856.
Doklady Earth Sciences - Complex research to determine the stress–strain state of the Earth’s crust and the types of seismotectonic destruction for the northeastern sector of the...  相似文献   
857.
Doklady Earth Sciences - The rocks and minerals of the Kolvitsa massif are studied by complex isotopic–geochronological and geochemical (U–Pb, Sm–Nd, REE contents of zircons)...  相似文献   
858.
The results of observations with the MASTER-SHOK robotic wide-field optical cameras onboard the Lomonosov Space Observatory carried out in 2016 are presented. In all, the automated transient detection system transmitted 22 181 images of moving objects with signal-to-noise ratios greater than 5 to the Earth. Approximately 84% of these images are identified with well-known artificial Earth satellites (including repeated images of the same satellite) and fragments of such satellites (space debris), according to databases of known satellites. The remaining 16% of the images are relate to uncatalogued objects. This first experience in optical space-based monitoring of near-Earth space demonstrates the high efficiency and great potential of using large-aperture cameras in space, based on the software and technology of the MASTER robotic optical complexes (the Mobile Astronomical System of TElescope- Robots (MASTER) global network of robotic telescopes of Lomonosov Moscow State University).  相似文献   
859.
The role of pressure as a source of gravity in general relativity is considered. In homogeneous, anisotropic cosmological models, the anisotropic pressure components along different coordinate axes are included as terms in the equations determining the accelerations along these axes; in this sense, this situation is similar to how the mass density is included in these equations. A change in the pressure component along one of the coordinates leads to an anisotropic change in the accelerations along all three coordinates. However, the pressure components are not present in the equation determining the initial conditions. On the other hand, with an inhomogeneous matter density distribution, the mass density and pressure play fundamentally different roles as sources of gravity. The consequences of this are considered.  相似文献   
860.
An analysis of the dynamics of the electron temperature of the solar atmosphere in regions where solar flares appear is presented. The temperatures are estimated from the emission in spectral lines of ions with various degrees of ionization. The emission of ionized helium and highly ionized iron was used. Images of preflare states and of flares from the archive of the American SDO spacecraft are analyzed. A solar flare is usually preceded by the registration of a bright glowing structure above the action region, with a temperature exceeding that of the corona. This preflare structure (~1010 cm) is identified with the development of a system of currents, which, according to numerical simulations, is responsible for the accumulation of energy above the active region before the flare. After several tens of hours of a slow increase in the brightness of the preflare glow in the 94 Å iron (FeXVIII) line, the emission in the 193 Å line of FeXXIV increases sharply, indicating a flare-like growth of the temperature up to at least 20 MK. This growth of the emission coincides with the onset of the solar flare. The observed dynamics of the emission in spectral lines of highly ionized ions is consistent with an electrodynamic model of a solar flare based on the accumulation of magnetic energy in a current sheet above the active region and the explosive release of the stored energy. Studies of mechanisms for solar flares are of special importance in connection with the discovery of solar cosmic rays. Information from the worldwide network of neutron monitors and from the GOES spacecraft has made it possible to firmly state that the source of solar rays is solar flares, not shocks generated by such flares. It cannot be ruled out that a similar mechanism, not shocks, is also responsible for the acceleration of cosmic rays in the Galaxy.  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