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   8147篇
  免费   364篇
  2020年   127篇
  2019年   168篇
  2018年   267篇
  2017年   264篇
  2016年   311篇
  2015年   205篇
  2014年   198篇
  2013年   2231篇
  2012年   240篇
  2011年   248篇
  2010年   249篇
  2009年   250篇
  2008年   176篇
  2007年   187篇
  2006年   185篇
  2005年   108篇
  2004年   96篇
  2003年   101篇
  2002年   100篇
  2001年   140篇
  2000年   106篇
  1999年   118篇
  1998年   118篇
  1997年   92篇
  1996年   94篇
  1995年   80篇
  1994年   73篇
  1993年   99篇
  1992年   78篇
  1991年   64篇
  1990年   58篇
  1989年   79篇
  1988年   68篇
  1987年   89篇
  1986年   71篇
  1985年   74篇
  1984年   74篇
  1983年   89篇
  1982年   68篇
  1981年   77篇
  1980年   79篇
  1979年   72篇
  1978年   61篇
  1977年   84篇
  1976年   65篇
  1975年   65篇
  1974年   49篇
  1973年   40篇
  1972年   53篇
  1971年   42篇
排序方式: 共有8511条查询结果,搜索用时 15 毫秒
1.
Evidence from several disciplines supports the proposition that following the Wisconsinan and an initial but brief moist phase of the Holocene, there was a gradual drying trend in the mid-continent Prairie Peninsula that peaked about 7000 years ago, a pattern that was not reversed until about 4000 years ago. Except for minor perturbations, conditions during the past four millennia have essentially been similar to those of the present. Studies in palynology and geomorphology have shown that the climatic regimes of the early/mid Post-glacial had a marked influence on both the biota and landscape erosional patterns, especially along the margins of the Prairie Peninsula. Measurable changes in the landscape and attendant biota show a time-transgressive pattern of drought related phenomena recorded palaeo-ecologically from west to east.Few studies of archaeological sites in the Prairie Peninsula have examined the evidence in and around the sites themselves for data reflecting local environmental dynamics. In fact, earlier models proposed for explaining the evolution of food-procuring systems in eastern North America virtually ignored potential changes in the natural environment. This paper examines data from two archaeological sites along the prairie-forest border in Missouri that contain long cultural sequences. Evidence is presented that pronounced changes in the natural environment occurred and that these biophysical variables are indeed critical for understanding the evolution of food-procuring societies in the American Midwest.  相似文献   
2.
3.
4.
5.
6.
7.
8.
This paper examines the regional structure and extraregional trends of Europe and the Asia-Pacific. The formation of the European Community and the latter's potential enlargement to Eastern Europe contrasts with the Asia-Pacific which has resisted economic and political integration and pursued economic linkages with countries outside of the region. The difference in regionalization tendencies have resulted in more geographically defined subregions in Europe, and greater territorial fragmentation in the Asia-Pacific. Even though European countries exhibit tighter interlinkages with one another, the evidence indicates that their extra-regional links compare favorably with the Asia-Pacific for much of the period from 1965 to 1994.  相似文献   
9.
10.
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   
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