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   5044篇
  免费   199篇
  2020年   69篇
  2019年   73篇
  2018年   104篇
  2017年   126篇
  2016年   126篇
  2015年   97篇
  2014年   67篇
  2013年   1420篇
  2012年   94篇
  2011年   109篇
  2010年   126篇
  2009年   128篇
  2008年   130篇
  2007年   106篇
  2006年   95篇
  2005年   74篇
  2004年   63篇
  2003年   69篇
  2002年   68篇
  2001年   61篇
  2000年   72篇
  1999年   82篇
  1998年   66篇
  1997年   50篇
  1996年   58篇
  1995年   56篇
  1994年   53篇
  1993年   59篇
  1992年   55篇
  1991年   36篇
  1990年   35篇
  1989年   57篇
  1988年   46篇
  1987年   56篇
  1986年   52篇
  1985年   75篇
  1984年   96篇
  1983年   83篇
  1982年   65篇
  1981年   72篇
  1980年   77篇
  1979年   70篇
  1978年   71篇
  1977年   56篇
  1976年   75篇
  1975年   77篇
  1974年   49篇
  1973年   39篇
  1972年   36篇
  1970年   31篇
排序方式: 共有5243条查询结果,搜索用时 15 毫秒
941.
942.
943.
Summary. A number of settlements and other traces of occupation have been identified in the mountainous areas near to tin and copper deposits in the Erzgebirge, and some of them excavated. The newly collected evidence seems to suggest that many small sources of metals, both tin and copper, were exploited, the former metal by washing from the river and creek beds. Though these sources were more modest than the British and Spanish tin supply, they seem to have served the Bohemian and Saxon Bronze Age cultures well.  相似文献   
944.
945.
946.
947.
948.
Precordilleran Late Palaeozoic brachiopod genera considered for this palaeobiogeographical analysis belong to four faunal associations: the low diversity Early Carboniferous (Tournaisian) Protocanites scalabrinii-Azurduya chavelensis Zone; the Late Carboniferous (Bashkirian-Moscovian) Levipustula fauna, which appears in sequences associated with glacial intervals; the latest Carboniferous-earliest Permian (Gzhelian-Asselian) Rhipidomella-Micraphelia and Tuberculatella-Aseptella associations, and the Early Permian (mid to late Asselian) Tivertonia jachalensis-Streptorhynchus inaequiornatus Biozone. The brachiopod affinities of the Precordillera are compared with the biogeographical Late Palaeozoic regions previously suggested by other authors using cluster analysis. During the Bashkirian-Moscovian, the Precordilleran faunas show a high affinity with the Austral Realm because of the presence of the Levipustula faunal elements in Eastern Australia. At the same time the affinity with the central and North American Regions is very low. The Early Permian Precordilleran faunas demonstrate highest affinity with the Gondwanan Realm with several genera also linked to the Tethyan and Boreal Realms. After the Late Carboniferous glacial episodes that affected the southwestern Gondwanan margin, the Precordilleran region underwent climatic amelioration. Subsequently, the Early Permian Precordilleran brachiopod assemblages are characterized by typical cool to cold water genera widely developed in the core Gondwanan Realm, with fewer genera (such as Kochiproductus, Rhynchopora and Neochonetes) suggesting a warmer water influence. The Precordilleran faunas demonstrate an increase in brachiopod diversity from the Carboniferous to the Permian, related to water temperature changes and to the palaeogeographical evolution of the southwestern Gondwanan margin and the movement of Gondwana across the South Pole.  相似文献   
949.
American constitutional history in the early national period seems at times to be a conversation—or an argument—among Virginians. There's James Madison, George Washington, George Mason, John Taylor of Caroline County, Judge Spencer Roane, John Randolph of Roanoke, to mention only some. At the center of this constellation were John Marshall and Thomas Jefferson.  相似文献   
950.
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