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   2057篇
  免费   77篇
  国内免费   11篇
测绘学   38篇
大气科学   193篇
地球物理   515篇
地质学   605篇
海洋学   177篇
天文学   393篇
综合类   3篇
自然地理   221篇
  2021年   14篇
  2020年   19篇
  2019年   24篇
  2018年   34篇
  2017年   44篇
  2016年   45篇
  2015年   35篇
  2014年   41篇
  2013年   98篇
  2012年   39篇
  2011年   68篇
  2010年   59篇
  2009年   104篇
  2008年   80篇
  2007年   72篇
  2006年   89篇
  2005年   76篇
  2004年   88篇
  2003年   76篇
  2002年   69篇
  2001年   66篇
  2000年   52篇
  1999年   34篇
  1998年   50篇
  1997年   34篇
  1996年   30篇
  1995年   33篇
  1994年   35篇
  1993年   29篇
  1992年   34篇
  1991年   21篇
  1990年   31篇
  1989年   22篇
  1988年   23篇
  1987年   31篇
  1986年   34篇
  1985年   36篇
  1984年   24篇
  1983年   44篇
  1982年   39篇
  1981年   37篇
  1980年   36篇
  1979年   25篇
  1978年   18篇
  1977年   21篇
  1976年   20篇
  1975年   18篇
  1974年   14篇
  1973年   17篇
  1971年   12篇
排序方式: 共有2145条查询结果,搜索用时 78 毫秒
61.
Beyond world cities: Central America in a global space of flows   总被引:1,自引:0,他引:1  
Central America is a region without a world city. Traditionally, the region's national projects have been based upon openness to the world economy: how do the region's contemporary transnational projects connect to the world economy under the new conditions of openness that is contemporary globalization? Focusing upon advanced producer services, three connections into the world city network are identified: global service firms operating directly in Central American cities, local service firms operating indirectly through extra-regional world cities and global service firms operating through Latin American regional offices. Miami is confirmed as the primary world city through which Central America connects into the world economy  相似文献   
62.
A coupled model,which is employed to study the dominating factor and key area of El Nino cycle formation,consists of a dynamical ocean model and a statistical atmospheric model.The coupled model with seasonal forcing successfully reproduces the El Nino event cycle which exhibits quasi-regular oscillations with a preferred period of about 4 years.The results show that the heat content(HC) is transported between the eastern and the western tropical Pacific areas.The spatial distribution of HC anomalies for four phases of the whole cycle clearly shows a possible formation mechanism of El Nino.Experiments further suggest that sea surface temperature in the tropical Pacific and HC in the central tropical Pacific are the most important factors and the central tropical Pacific is the most important area for determining formation of El Nino cycle.  相似文献   
63.
James Taylor 《Area》1997,29(2):160-171
Summary This paper discusses the relationship between advertising and 'race', using as its foundation the replication of a study conducted in the US which used content analysis to examine the representation of Black characters in television advertisements. The replication facilitates a comparison of the British and American cases, revealing significant differences in the frequency and perceived importance of such representations. It can also help draw out the specificities of the UK situation. The paper attempts to convey the complexity of the interplay between advertising and racialisation, and emphasises that while such quantitative, textual studies offer a useful basis for further research, they are limited by their failure to address the motivations of producers and how advertisements are read by different groups in different places.  相似文献   
64.
65.
66.
67.
Coastal steepening potentially presents an array of management issues in the form of financial implications of sea defence degradation, increased risk posed to the hinterland as wave attenuation is reduced, 'coastal squeeze' and statutory requirements in the light of the Habitats Directive. The extent to which coastal steepening has occurred throughout England and Wales has been investigated through use of a GIS and dataset based on historical Ordnance Survey map information. Data were collected along 1084 selected profile lines, positioned so as to be geomorphologically representative of the coast. Features recorded from each map year included the positions of mean high water (MHW) and mean low water (MLW), the relative movements of which infer changing intertidal gradients. The results presented in this paper are on a subject and scale not previously published. It is revealed that 61% of the coastline studied has experienced a tendency towards steepening. Of the remainder, 33% has flattened, and 6% has experienced no rotational movement. This tendency towards steepening has been the dominant movement on each of the west, south, and east coasts.  相似文献   
68.
69.
70.
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