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   1388篇
  免费   56篇
  2023年   7篇
  2022年   5篇
  2021年   7篇
  2020年   24篇
  2019年   45篇
  2018年   45篇
  2017年   60篇
  2016年   51篇
  2015年   23篇
  2014年   42篇
  2013年   431篇
  2012年   37篇
  2011年   42篇
  2010年   37篇
  2009年   33篇
  2008年   27篇
  2007年   28篇
  2006年   24篇
  2005年   23篇
  2004年   29篇
  2003年   33篇
  2002年   25篇
  2001年   25篇
  2000年   22篇
  1999年   21篇
  1998年   12篇
  1997年   24篇
  1996年   11篇
  1995年   20篇
  1994年   15篇
  1993年   15篇
  1991年   6篇
  1990年   11篇
  1989年   6篇
  1988年   9篇
  1987年   5篇
  1986年   11篇
  1985年   8篇
  1984年   17篇
  1983年   13篇
  1982年   16篇
  1981年   10篇
  1980年   5篇
  1979年   9篇
  1978年   9篇
  1977年   9篇
  1976年   8篇
  1975年   8篇
  1974年   5篇
  1969年   4篇
排序方式: 共有1444条查询结果,搜索用时 31 毫秒
111.
112.
We present the combination of an analysis of resource demand by the early post-contact (1721) Cherokee population with spatially explicit estimates of production for five key resources: architectural land, agricultural land, firewood, hard mast, and white-tailed deer (Odocoileus virginianus). We combine a recent synthesis of village location and population, a map of recognized Cherokee territory, digital terrain data, estimates of per capita demand, and productive capacity for each resource. Average, high, and low demands were estimated for each resource and assigned based on a weighted function of terrain and distance from each village. We conclude that Cherokee demands for architectural and agricultural land, hard mast, and fuelwood were easily met within a short proximity to each town under all combinations of production and demand. These resources were likely not limiting, and were satisfied for the entire Cherokee population by less than 1% of the entire recognized Cherokee territory in 1721. These resources likely exceeded demand even when sources were restricted to the convex hull of the Cherokee territory, or to near stream, flat regions. Deer resources were likely harvested over a much larger area and to a much greater extent. Our best estimate of deer resource demand was 32% of annual sustainable production in the Cherokee territory, with from 16 to 48% of estimated sustainable production harvested for low and high demand estimates, respectively. Our estimates vary in response to uncertainties in deer production, harvest proportion, deer density, and sustainable harvest rates. Deer demand was substantially higher under all combinations of conditions than that available within the convex hull of Cherokee villages, indicating significant travel was needed to furnish deer requirements. Spatially explicit models that consider terrain- and distance-related tradeoffs suggest that Cherokee demand for deer drove harvest over areas consisting of over half the recognized Cherokee territory.  相似文献   
113.
114.
115.
116.
This article reviews the state of the two security and defence institutions available to west Europeans: NATO and the EU's common European Security and Defence Policy (ESDP). In each case, the authors assess the political maturity and stability of the institution, and then ask what it can contribute in terms of coordinated military capability to west European's strategic readiness. NATO's Prague summit in November 2002 will address the thorny issue of the next tranche of post–Cold War enlargement. But beyond the predictable debate about which candidates to admit, and what should be offered to those unsuccessful in their bid, there will be a far more urgent and important agenda to be discussed at Prague—the military capabilities of the European allies. Given that ESDP is still far from achieving its capability goals, the authors argue that the time is right for European allies to begin thinking in terms of generating a composite, joint strike force which could be configured to be interoperable with US forces and which could salvage something useful from the disheartening lack of progress in developing a European military capability.  相似文献   
117.
This article examines how the British government has responded to Zimbabwe’s ongoing crisis. This case raises several wider issues for British foreign policy, most notably the question of how much leverage London can exercise on the international scene in general, and over relatively small and weak states like Zimbabwe in particular. Zimbabwe’s crisis also raises profound questions about the appropriate balance between bilateral and multilateral policies, and between engaging in public criticism and conducting so–called ‘quiet diplomacy’. While bilateralism clearly has not worked, multilateralism has revealed its own frustrations, especially given the reluctance of many African elites within a number of organizations to criticize President Mugabe’s policies. This reluctance threatens to unravel the British Labour government’s stated objectives in Africa while at the same time raising important doubts over the credibility of the New Partnership for Africa’s Development (NEPAD), and whether an ‘Africa moment’ can be discerned in the manner articulated by prime minister Tony Blair.  相似文献   
118.
119.
120.
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