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   85930篇
  免费   1145篇
  国内免费   528篇
测绘学   1775篇
大气科学   5665篇
地球物理   16364篇
地质学   30921篇
海洋学   7911篇
天文学   19950篇
综合类   222篇
自然地理   4795篇
  2022年   620篇
  2021年   1048篇
  2020年   1120篇
  2019年   1251篇
  2018年   2555篇
  2017年   2367篇
  2016年   2726篇
  2015年   1362篇
  2014年   2622篇
  2013年   4516篇
  2012年   2875篇
  2011年   3710篇
  2010年   3384篇
  2009年   4283篇
  2008年   3736篇
  2007年   3846篇
  2006年   3574篇
  2005年   2537篇
  2004年   2461篇
  2003年   2296篇
  2002年   2283篇
  2001年   1976篇
  2000年   1964篇
  1999年   1542篇
  1998年   1606篇
  1997年   1470篇
  1996年   1249篇
  1995年   1248篇
  1994年   1051篇
  1993年   1016篇
  1992年   938篇
  1991年   971篇
  1990年   941篇
  1989年   824篇
  1988年   758篇
  1987年   892篇
  1986年   776篇
  1985年   949篇
  1984年   1078篇
  1983年   1042篇
  1982年   962篇
  1981年   909篇
  1980年   799篇
  1979年   755篇
  1978年   737篇
  1977年   622篇
  1976年   629篇
  1975年   619篇
  1974年   591篇
  1973年   658篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Syn-ore centroid type deformations that produced unusual structural assemblages are identified in the Uryakh ore field. The regularities of the deformation process comparable to a mechanism of the centroid-type seismic focus are established. The results of studying fluid inclusions suggest that the pressure—temperature parameters of the system correspond to conditions typical of the seismic regime. A model of formation of structural assemblages in a centroid-type dynamic regime with the participation of fluids is proposed for the first time.  相似文献   
992.
The first data on abnormally high δ13С values in hydrocarbonates (НСО 3-) dissolved in underground waters of coal deposits of Kuzbass (up to +30.9‰) are reported. It is shown that such an unusual isotope composition of waters results from the long, strictly directed interaction in the water–rock–gas–organic material system occurring under the conditions of hindered water exchange. Extensive fractionation of C isotopes is the result of the evolution of the water–rock–gas–coal system after penetration of infiltration waters into the coal deposits and their long interaction with all these components, rather than metamorphism of organic material upon its transformation into coal. With respect to such an approach, the isotope composition of dissolved C may indicate the duration of the evolution in the water–rock–gas–organic material system.  相似文献   
993.
The results of 3D modeling of the formation of the accretion disks of intermediate polars are presented. A model with misaligned rotation axes of accretor and the orbit is onsidered, in which it is assumed that the white dwarf has a dipolar magnetic field with its symmetry axis inclined to the whitedwarf rotation and orbital axes. The computations show that, in the early stages of formation of the disk, the action of magnetic field is able to create the initial (seed) inclination of the disk. This inclination is then supported mainly by the dynamical pressure of the flow from the inner Lagrangian point L1. As themass of the disk increases, the inclination disappears. Under certain conditions, the disk inclination does not arise in systems with misaligned white-dwarf rotation and orbital axes. The influence of the magnetic field and asynchronous rotation of the accretor may result in the formation of spiral waves in the disk with amplitudes sufficient to be detected observationally.  相似文献   
994.
The atmospheric disturbances caused by the first rocket launch from the Vostochnyi Cosmodrome on April 28, 2016, were registered 10–24 min after the launch using the signals of the GPS/GLONASS global navigation satellite systems. The analysis of the spatial distribution of the disturbances allowed the conclusion that the launch vehicle moved northwest from the cosmodrome, which corresponds to a trajectory of the satellite movement to the orbit with an inclination of 98º.  相似文献   
995.
996.
To determine the long-term landscape evolution of the Albertine Rift in East Africa, low-temperature thermochronology was applied and the cooling history constrained using thermal history modelling. Acquired results reveal (1) “old” cooling ages, with predominantly Devonian to Carboniferous apatite fission-track ages, Ordovician to Silurian zircon (U–Th)/He ages and Jurassic to Cretaceous apatite (U–Th–Sm)/He ages; (2) protracted cooling histories of the western rift shoulder with major phases of exhumation in mid-Palaeozoic and Palaeogene to Neogene times; (3) low Palaeozoic and Neogene erosion rates. This indicates a long residence time of the analysed samples in the uppermost crust, with the current landscape surface at a near-surface position for hundreds of million years. Apatite He cooling ages and thermal history models indicate moderate reheating in Jurassic to Cretaceous times. Together with the cooling age distribution, a possible Albertine high with a distinct relief can be inferred that might have been a source area for the Congo Basin.  相似文献   
997.
998.
999.
1000.
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