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   463篇
  免费   15篇
  国内免费   4篇
测绘学   17篇
大气科学   41篇
地球物理   83篇
地质学   172篇
海洋学   39篇
天文学   76篇
综合类   1篇
自然地理   53篇
  2021年   6篇
  2020年   4篇
  2019年   8篇
  2018年   8篇
  2017年   15篇
  2016年   24篇
  2015年   10篇
  2014年   19篇
  2013年   25篇
  2012年   20篇
  2011年   34篇
  2010年   22篇
  2009年   26篇
  2008年   20篇
  2007年   12篇
  2006年   20篇
  2005年   7篇
  2004年   24篇
  2003年   21篇
  2002年   14篇
  2001年   11篇
  2000年   10篇
  1999年   11篇
  1998年   8篇
  1997年   5篇
  1996年   3篇
  1995年   5篇
  1994年   5篇
  1993年   6篇
  1992年   4篇
  1991年   3篇
  1990年   5篇
  1989年   5篇
  1988年   3篇
  1987年   3篇
  1986年   2篇
  1985年   7篇
  1984年   9篇
  1983年   6篇
  1982年   2篇
  1980年   5篇
  1979年   3篇
  1978年   2篇
  1977年   2篇
  1976年   3篇
  1975年   4篇
  1974年   2篇
  1973年   3篇
  1968年   1篇
  1967年   1篇
排序方式: 共有482条查询结果,搜索用时 0 毫秒
481.
482.
Geoarchaeological investigations in an area surrounding the confluence of the upper Colorado and Concho Rivers, Edwards Plateau of West Texas, have produced a detailed landscape evolution model which provides a framework for discussion of the influences of geomorphic processes on the development, preservation, and visibility of the archaeological record. Field mapping within the study area has differentiated six allostrati-graphic units of fluvial origin in both valleys, as well as extensive eolian sand sheets along the Colorado River. Early to middle Pleistocene terrace remnants cap many upland areas, whereas two distinct late Pleistocene terrace surfaces are widespread within the study area at somewhat lower elevations. Fluvial activity during the time period of human occupation is represented by an extensive Holocene terrace and underlying valley fill, which is up to 11 m in thickness. Valley fill sediments can be subdivided into allostratigraphic units of early to middle Holocene (ca. 10,000–5000 yr B.P.) and late Holocene age (ca. 4600–1000 yr B.P.), which are separated by a buried soil profile. The modern incised channels and very narrow floodplains represent the last millennium. Eolian sand sheets of early to middle Holocene age overlie limestone- and shale-dominated uplands, Pleistocene terraces, and in some cases the Holocene valley fill along the Colorado River. Pleistocene terraces have been stable features in the landscape and available for settlement through the time period of human occupation. Archaeological materials of all ages occur at the surface, and the record preserved in individual sites range from that associated with discrete periods of activity to longer-term palimpsests that represent repeated use over millennia. Sites within early to middle Holocene and late Holocene fills represent short-term utilization of constructional floodplains during the Paleoindian through early Archaic and middle to late Archaic time periods respectively. By contrast, those that occur along the buried soil profile developed in the early to middle Holocene fill record middle to late Archaic cultural activity on stable terrace surfaces, and represent relatively discrete periods of activity to longer-term palimpsests that represent repeated use over the 3000–4000 years of subaerial exposure. Late Prehistoric sites occur as palimpsests on soils developed in late Holocene alluvium or stratified within modern floodplain facies. Paleoindian through Late Prehistoric sites occur stratified within eolian sand sheets or along the unconformity with subjacent fluvial deposits. The landscape evolution model from the upper Colorado and Concho Rivers is similar to that developed for other major valley axes of the Edwards Plateau. This model may be regionally applicable, and can be used to interpret the geomorphic setting and natural formation processes for already known sites, as well as provide an organizational framework for systematic surface and subsurface survey for new archaeological records. 0 1992 John Wiley & Sons, Inc.  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