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   42504篇
  免费   1823篇
  2020年   540篇
  2019年   890篇
  2018年   970篇
  2017年   1166篇
  2016年   1277篇
  2015年   993篇
  2014年   965篇
  2013年   14262篇
  2012年   1120篇
  2011年   1147篇
  2010年   1140篇
  2009年   1121篇
  2008年   1070篇
  2007年   976篇
  2006年   870篇
  2005年   604篇
  2004年   592篇
  2003年   563篇
  2002年   524篇
  2001年   517篇
  2000年   457篇
  1999年   504篇
  1998年   474篇
  1997年   432篇
  1996年   416篇
  1995年   419篇
  1994年   367篇
  1993年   408篇
  1992年   390篇
  1991年   291篇
  1990年   298篇
  1989年   302篇
  1988年   306篇
  1987年   325篇
  1986年   299篇
  1985年   416篇
  1984年   441篇
  1983年   447篇
  1982年   399篇
  1981年   379篇
  1980年   427篇
  1979年   413篇
  1978年   404篇
  1977年   427篇
  1976年   377篇
  1975年   380篇
  1974年   293篇
  1973年   260篇
  1972年   241篇
  1970年   226篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
The concentrations of two major elements and thirteen trace elements in 73 selected sherds of fine grey ware from the Iron Age and Roman period, excavated at Conimbriga, Santa Olaia and Tavarede, Portugal, were determined by instrumental neutron activation analysis. These concentrations were used to calculate distance matrices which were then subjected to cluster analysis employing SAHN and k-means methods, as well as to principal components analysis, to group the sherds according to the overall similarity of their compositional characteristics. The results showed that equivalent groupings appeared regardless of the taxonomic method used. Two major clusters were recognized corresponding to two different sites, namely Conimbriga and Santa Olaia, suggesting that the ceramics from these sites were made locally. No significant differences in compositional patterns were observed between iron age and roman sherds from Conimbriga.  相似文献   
63.
This study explores the spatial structure of retailing in Milwaukee, Wisconsin, in the era before the introduction of the electric streetcar in 1890. It uses city directory listings to chart changes in the numbers and types of retail outlets, their degree of nucleation and the functional complexity of such nucleations. The evidence suggests the early appearance of non-central retailing, the rapid dispersal of high as well as low order goods to non-central sites and the early emergence initially of a three-level and then, by 1870, a four-level hierarchy of shopping clusters. The pattern of retail clustering varied with the class and ethnic character of neighbourhoods, and clusters gravitated toward major arterial routes even in the pre-mass transit ear. Urban retailing in the second half of the nineteenth century was neither randomly dispersed nor over-whelmingly concentrated in a single central retail district, but developed a spatial hierarchy that clearly anticipated modern patterns.  相似文献   
64.
65.
66.
67.
A problem which has arisen in discussions of an elm-disease explanation for the Neolithic elm decline has been the lack of fossil records of Scolytus scolytus (F.) (elm bark beetle), which is the main carrier of the fungus which causes the present epidemic of Dutch Elm Disease. Now, the discovery of wing cases of two individuals from elm decline deposits at Hampstead Heath, London, proves that the beetle was present in Britain during this episode. The deposits in which it occurs are described, and the various implications for elm disease causing, aiding or at least occurring during this stage of the early Neolithic are discussed.  相似文献   
68.
China has officially become a predominantly urban country, with over 50% of the population now registered as urban residents. Its urbanization process has been described as the most managed in human history. The Chinese government manages the building of new cities, regulates the housing of displaced people and controls squatters. As an historically poorer area, the west of China has been the target of ongoing efforts at infrastructural development. Describing urbanization as managed however masks the conflicts and contradictions involved in a process which is far from smooth. Although villagers are usually seen to be largely the powerless victims of these initiatives, it is clear that many try to take advantage of the situation, while others are unable to do so. Based on recent fieldwork and eight years of visits to one village undergoing urbanization, this article looks at the complex dynamics involved and at the moral battleground which they lay bare.  相似文献   
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