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   35篇
  免费   7篇
大气科学   1篇
地球物理   13篇
地质学   16篇
海洋学   3篇
天文学   8篇
自然地理   1篇
  2021年   1篇
  2020年   4篇
  2019年   2篇
  2018年   2篇
  2017年   2篇
  2016年   2篇
  2015年   3篇
  2014年   1篇
  2013年   1篇
  2011年   1篇
  2010年   2篇
  2008年   1篇
  2007年   1篇
  2005年   1篇
  2004年   1篇
  2001年   2篇
  2000年   1篇
  1992年   1篇
  1989年   1篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1980年   2篇
  1978年   1篇
  1975年   1篇
  1973年   1篇
  1943年   2篇
  1940年   1篇
排序方式: 共有42条查询结果,搜索用时 0 毫秒
41.
Research on soil fertility is presented in the context of runoff agriculture, a venerable farming system that has been used for millennia in arid to semiarid regions, where water is a major limiting resource for crop production. The agroecology of runoff farming was studied with the Zuni to evaluate nutrient and hydrologic processes, management, maize productivity, and soil quality in some of the oldest recognized fields in the United States. This ancient Southwest agriculture has functioned without conventional irrigation or fertilization by tapping into biogeochemical processes in natural watersheds connected to fields. Carefully placed fields are managed on alluvial fans and other valley margin landforms to intercept runoff and associated sediment and organic debris transported from adjoining forested uplands. We report on research to evaluate and link nitrogen and phosphorus, two key nutrients for crop production, in watershed, soil, and crop components of this agroecosystem. Nutrient data have been collected by observational and experimental methods for each component and the transport of nutrients from watershed to field to maize. The condition of Zuni agricultural soils suggests that their knowledge and management of soils contributed to effective conservation. This study and others indicate the need for further long‐term monitoring and experimental research on watersheds, runoff processes, field soils, and crops across a range of arid to semiarid ecosystems. © 2007 Wiley Periodicals, Inc.  相似文献   
42.
Zooarchaeology can contribute to issues that lie beyond the traditional boundaries of archaeology and paleobiology. The techniques and methods of zooarchaeology are essential to an historical ecology that has emerged as a powerful perspective for understanding indigenous peoples and landscapes of the neotropics, both in the present and the past. In order to realize fully its potential contributions to historical ecology, zooarchaeology must reject the arbitrary dichotomization of culture and nature and a viewpoint that considers indigenous peoples as passive reactors to environments rather than as active creators of human landscapes. Zooarchaeology must avoid the seduction of neo-Malthusian assumptions that underlie many cherished models, and should do more than simply list extinctions at the hands of prehistoric humans. Instead, zooarchaeologists should focus on the study of past human landscapes, explore dynamic disturbances and the human maintenance of habitat mosaics, record the infrastructure of intensive agriculture, and understand the indigenous logic of past biodiversity management. When archaeologists study the landscapes of previous human populations, they are engaged in the practice of historical ecology.  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