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   85523篇
  免费   1137篇
  国内免费   531篇
测绘学   1757篇
大气科学   5611篇
地球物理   16268篇
地质学   30795篇
海洋学   7868篇
天文学   19932篇
综合类   226篇
自然地理   4734篇
  2022年   619篇
  2021年   1048篇
  2020年   1116篇
  2019年   1248篇
  2018年   2552篇
  2017年   2362篇
  2016年   2721篇
  2015年   1353篇
  2014年   2619篇
  2013年   4490篇
  2012年   2862篇
  2011年   3694篇
  2010年   3373篇
  2009年   4265篇
  2008年   3721篇
  2007年   3831篇
  2006年   3551篇
  2005年   2524篇
  2004年   2446篇
  2003年   2283篇
  2002年   2273篇
  2001年   1970篇
  2000年   1955篇
  1999年   1536篇
  1998年   1595篇
  1997年   1469篇
  1996年   1243篇
  1995年   1242篇
  1994年   1042篇
  1993年   1007篇
  1992年   934篇
  1991年   968篇
  1990年   936篇
  1989年   819篇
  1988年   751篇
  1987年   886篇
  1986年   773篇
  1985年   947篇
  1984年   1070篇
  1983年   1032篇
  1982年   952篇
  1981年   893篇
  1980年   792篇
  1979年   751篇
  1978年   727篇
  1977年   622篇
  1976年   626篇
  1975年   613篇
  1974年   589篇
  1973年   657篇
排序方式: 共有10000条查询结果,搜索用时 6 毫秒
981.
Based on the spore-pollen data, the mineral composition of clay rocks, analyzed structures and facies, and a general paleogeographic analysis, the sedimentation conditions and landscapes of islands located during the Late Bajocian in the region of the present-day the Crimean Mountains have been reconstructed. It is shown that the sublatitudinally elongated insular land zone had a width of 30 km, the heights of the islands were no more than 1 km, with steep mudflow-affected northern slopes and with an extensive river system on the southern slopes.  相似文献   
982.
The statistical study of intense mesoscale cyclones formed in the Black Sea region in 1979-2013 is carried out using the surface wind data of the RegCM climate model. Such cyclone parameters as intensity, lifetime, area, height, and trajectories over the sea as well as the place and time of origin are considered. The distribution of mesocyclones by months and times of day is considered. The obtained results are compared with the results of a statistical study on the Black Sea mesocyclones based on the PRECIS climate model. Possible causes for differences in data on the intensity and number of mesocyclones simulated by RegCM and PRECIS models are considered.  相似文献   
983.
The first data on the chemical composition of dispersed matter from sedimentary traps are reported. The suspended components of sedimentary matter (amorphous silica, organic matter, carbonates, and lithogenic material, as well as Fe, Mn, and minor elements) are considered. As a result, it is shown that the intraannual variability in vertical fluxes of sedimentary matter is characterized by a seasonal increase in spring and autumn. The high fluxes of the components of sedimentary matter on the northern and southern slopes of the Derbent Basin in winter are explained by precipitation of material from the nepheloid layer that forms over the contour current.  相似文献   
984.
Issues of the formation and recording of the spatial and angular distributions of thermal radio radiation of rainfall in the microwave range are discussed. The thermal radio-frequency radiative transfer in a threedimensional rain cell is simulated numerically with a different rainfall rate, taking into account the nonspherical shape of falling raindrops and their size distribution. The role of the three-dimensional inhomogeneity of rainfall fields in the formation of a field of their inherent thermal radio radiation in the microwave range is revealed.  相似文献   
985.
A numerical experiment has been carried out using a hydrodynamical model with nonlinear equations of motion and heat and salt advection to reconstruct the fields of hydrophysical parameters taking into account the real atmospheric forcing for the autumn season along the southern coast of the Crimean Peninsula. The studied part of the coast is situated at 44.25°N 33.95°E/44.72°N 34.55°E. High spatial resolution is used for modeling: 350 m in the horizontal plane with 38 layers in the vertical; the bottom topography is described in detail with ~500 m resolution. Detected and studied meso- and sub-mesoscale structures in the current field agree well with the observational data, which is impossible or hard to identify in numerical experiments with coarser resolution. Their kinematic characteristics and the lifetime are defined and some mechanisms of their origin are suggested.  相似文献   
986.
The first find of srilankite (very rare Zr and Ti oxide, Ti2ZrO6) in the Urals and the third find in Russia is reported. Srilankite forms very small (0.5–20 μm) inclusions in some rutile grains. These minerals are observed in the rare rock variety, corundum-bearing spinel–saphirine hornblendite forming a block in serpentinized amphibolizied peridotite of the Ilmeny–Vishnevogorsk Complex, near the village of Taiginka, Chelyabinsk oblast. Srilankite has not been observed in such an association yet. The composition of the host rock provides evidence for its deep (the lowermost crust of the Earth) origin. Srilankites of the Urals are distinguished from all others by the high concentrations of UO2, ThO2, HfO2, and Nb2O5, which provides additional evidence for their crustal origin. Srilankite may indicate high-temperature and high-pressure conditions of rock formation.  相似文献   
987.
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   
988.
989.
990.
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