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   89573篇
  免费   1241篇
  国内免费   917篇
测绘学   2553篇
大气科学   6413篇
地球物理   16592篇
地质学   34116篇
海洋学   7660篇
天文学   19913篇
综合类   352篇
自然地理   4132篇
  2022年   441篇
  2021年   782篇
  2020年   843篇
  2019年   920篇
  2018年   4154篇
  2017年   3855篇
  2016年   3526篇
  2015年   1393篇
  2014年   2294篇
  2013年   3873篇
  2012年   3206篇
  2011年   5171篇
  2010年   4610篇
  2009年   5538篇
  2008年   4583篇
  2007年   5167篇
  2006年   3024篇
  2005年   2573篇
  2004年   2528篇
  2003年   2446篇
  2002年   2216篇
  2001年   1799篇
  2000年   1741篇
  1999年   1439篇
  1998年   1466篇
  1997年   1352篇
  1996年   1136篇
  1995年   1101篇
  1994年   1023篇
  1993年   858篇
  1992年   843篇
  1991年   797篇
  1990年   897篇
  1989年   723篇
  1988年   718篇
  1987年   764篇
  1986年   687篇
  1985年   883篇
  1984年   973篇
  1983年   866篇
  1982年   844篇
  1981年   729篇
  1980年   721篇
  1979年   667篇
  1978年   649篇
  1977年   555篇
  1976年   507篇
  1975年   530篇
  1974年   465篇
  1973年   505篇
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
121.
122.
The D-CIXS Compact X-ray Spectrometer will provide high quality spectroscopic mapping of the Moon, the primary science target of the ESA SMART-1 mission. D-CIXS consists of a high throughput spectrometer, which will perform spatially localised X-ray fluorescence spectroscopy. It will also carry a solar monitor, to provide the direct calibration needed to produce a global map of absolute lunar elemental abundances, the first time this has been done. Thus it will achieve ground breaking science within a resource envelope far smaller than previously thought possible for this type of instrument, by exploiting two new technologies, swept charge devices and micro-structure collimators. The new technology does not require cold running, with its associated overheads to the spacecraft. At the same time it will demonstrate a radically novel approach to building a type of instrument essential for the BepiColombo mission and potential future planetary science targets.  相似文献   
123.
This paper proposes a multi‐level parallelized substructuring–frontal combined algorithm for the analysis of the problem of thermo/hydraulic/mechanical behaviour of unsaturated soil. Temperature, displacement, pore water pressure and pore air pressure are treated as the primary variables in a non‐linear analysis. Details are given firstly of the substructuring–frontal combined approach. The incorporation of the algorithm in a multi‐level parallel strategy is then discussed. The parallel processing can thus be carried out at different substructural levels. The method thus developed impacts, in a positive way, on both computer storage requirement and execution time. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
124.
The discovery of binaries among the population of transneptunian objects isa landmark advance in the study of this remote region of the solar system.Determination of binary orbits will enable direct determination of systemmasses, fundamental for determination of density, internal structure, and bulkcomposition. The mere existence of binaries with the observed separations andapparent masses constrains models of planetary formation.  相似文献   
125.
126.
Radiative Transfer (RT) codes with image capability are a fundamental tool for preparing interferometric observations and for interpreting visibility data. In view of the upcoming VLTI facilities, we present the first comparison of images/visibilities coming from two 3D codes that use completely different techniques to solve the problem of self-consistent continuum RT. In addition, we focus on the astrophysical case of a disk distorted by tidal interaction with by-passing stars or internal planets and investigate for which parameters the distortion can be best detected in the mid-infrared using the mid-infrared interferometric device MIDI. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
127.
128.
129.
130.
The Munich Near-IR Cluster Survey (MUNICS) is a wide-area, medium-deep, photometric survey selected in the K' band. The project's main scientific aims are the identification of galaxy clusters up to redshifts of unity and the selection of a large sample of field early-type galaxies up to z < 1.5 for evolutionary studies. We created a Large Scale Structure catalog, using a new structure finding technique specialized for photometric datasets, that we developed on the basis of a friends-of-friends algorithm. We tested the plausibility of the resulting galaxy group and cluster catalog with the help of Color-Magnitude Diagrams (CMD), as well as a likelihood- and Voronoi-approach. This revised version was published online in August 2006 with corrections to the Cover Date.  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