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   4496篇
  免费   822篇
  国内免费   656篇
测绘学   851篇
大气科学   385篇
地球物理   353篇
地质学   1305篇
海洋学   182篇
天文学   110篇
综合类   1130篇
自然地理   1658篇
  2024年   7篇
  2023年   54篇
  2022年   147篇
  2021年   185篇
  2020年   173篇
  2019年   182篇
  2018年   156篇
  2017年   236篇
  2016年   227篇
  2015年   248篇
  2014年   331篇
  2013年   310篇
  2012年   367篇
  2011年   407篇
  2010年   354篇
  2009年   231篇
  2008年   254篇
  2007年   278篇
  2006年   288篇
  2005年   261篇
  2004年   227篇
  2003年   183篇
  2002年   139篇
  2001年   119篇
  2000年   95篇
  1999年   96篇
  1998年   58篇
  1997年   68篇
  1996年   37篇
  1995年   44篇
  1994年   39篇
  1993年   33篇
  1992年   28篇
  1991年   22篇
  1990年   15篇
  1989年   9篇
  1988年   9篇
  1987年   7篇
  1986年   10篇
  1985年   4篇
  1984年   5篇
  1983年   3篇
  1982年   3篇
  1979年   2篇
  1978年   3篇
  1976年   7篇
  1975年   2篇
  1973年   3篇
  1972年   2篇
  1971年   3篇
排序方式: 共有5974条查询结果,搜索用时 15 毫秒
1.
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   
2.
邵正义  赵君亮 《天文学报》1996,37(4):377-386
本文提出了一个普适的衡量成团天体系统成员概率计算结果的有效性指数:E=1-NΣ{P(i)[1-P(i)]}/ΣP(i)Σ[1-P(i)]},并以此对以Sanders方法为基础的各种成员确定模型的有效性进行了分析.从总体上说,运动学资料(自行、视向速度等)是一类有效的观测判据.  相似文献   
3.
We present a library of 47 open-cluster integrated spectra, mostly obtained at CASLEO (San Juan, Argentina) in the range  3600 < λ < 7400 Å  , which are made available at CDS. The data are combined with previous spectra to obtain 10 high signal-to-noise ratio basic templates in the young and intermediate-age domains, which are also provided in the library. These Galactic disc templates represent the increased time resolution spectral evolution of a stellar population unit around the Solar metallicity level. The improved signal-to-noise ratio of the present templates with respect to previous template lists, together with their increased time resolution, allowed us to improve the fundamental parameters of some open clusters. The present spectral library will be useful for several astrophysical applications, particularly for population syntheses of star-forming giant galaxies.  相似文献   
4.
数字地球、数字城市是近几年刚提出来的一个全新的概念 ,但数字城市的建设却以空前的速度向前发展着 ,国务院总理朱熔基在视察宜昌时提出要把宜昌建设成世界级的城市 ,未来的城市数字化程度将是衡量一个城市发达程度的重要指标 ,启动数字宜昌建设是跻身世界级城市 ,提高宜昌市综合竞争力的重要举措  相似文献   
5.
1INTRODUCTIONClusters,definedasgeographicallyproximategroupsofinterconnectedcompaniesandassociatedinstitutionsinparticularfields,linkedbycommonalitiesandcomple-mentarities(PORTER,2000),havearousedanintenseinterestofurbanandregionalplanningresearchersandpolicymakersoverthepastdecades.Itiswidelyrecog-nizedthatclusterscanpromoteproductivityandinno-vation,developlocalcompetitiveadvantages.Popular-izedbyMichaelPORTERinhisbook“TheCompetitiveAdvantageofNationsin1990,theclusterisnotanewcon…  相似文献   
6.
本文根据大量的调查资料,采用多指标评判打分法对铜川市区滑坡逐一进行了危险性综合评价,旨在为该区滑坡的预测与防治提供可靠的依据。  相似文献   
7.
利用上海天文台的照相底片资料,确定了疏散星团NGC6530天区364颗恒星的自行和成员概率,并对有关自行测定的方法、结果和精度等问题作了较为详细的介绍和讨论。使用的底片历元差为87年,全部恒星自行中误差的均方根值为1.09mas/a。  相似文献   
8.
9.
Gary Bridge 《Geoforum》2008,39(4):1570-1584
This paper explores the radical possibilities of pragmatism for geography using the illustration of arguments concerning a renewed (urban) public realm through the exchange of validity claims in communication. Pressing further the pragmatist possibilities of Habermas’s idea of communicative action it draws on John Dewey’s work, and a range of contemporary pragmatist philosophers, to consider human communicability in its widest sense. This is then explored using an example of the spatiality and performativity of body-minds in a range of communicative spaces of the city. Then the paper moves on to consider the radical implications of pragmatism for geography in general in terms of body-mind/environment relations; a transactional view of space; experience, rationality and radical democracy.  相似文献   
10.
Identifying China’s leading world city: a network approach   总被引:3,自引:0,他引:3  
This paper reports our research on China’s world cities. Formal network analysis of air passenger linkages for recent years among China’s most populous cities and among many of the world’s largest cities allows us to identify the country’s leading world city from among the leading Mainland candidates, Beijing, Shanghai and Guangzhou. We theorize our findings about China’s world cities in relation to both global forces (and China’s increasing entanglement with them) and the policies and actions of the national state. We examine the national and global urban network through a longitudinal, two-level analysis of airline passenger travel for four time points between about 1990 and 2005. We show that Beijing was China’s leading world city at the beginning of the time period, a status it lost nationally in as early as 1995, and then globally 10 years later. On the other hand Shanghai became China’s leading world city, and it acquired this status first nationally in 2000, and then globally in 2005. The changing status of the Chinese capital corresponds to the country’s increasing involvement with the capitalist world economy. Shanghai’s ascendance as the leading world city in China may indicate that global forces have come to play an increasingly important role relative to that of the developmental state.
Michael F. TimberlakeEmail:
  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