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   331篇
  免费   7篇
  国内免费   4篇
测绘学   12篇
大气科学   48篇
地球物理   63篇
地质学   115篇
海洋学   33篇
天文学   39篇
综合类   2篇
自然地理   30篇
  2021年   3篇
  2020年   5篇
  2019年   4篇
  2018年   6篇
  2017年   8篇
  2016年   9篇
  2015年   5篇
  2014年   17篇
  2013年   26篇
  2012年   14篇
  2011年   12篇
  2010年   7篇
  2009年   28篇
  2008年   14篇
  2007年   20篇
  2006年   9篇
  2005年   8篇
  2004年   9篇
  2003年   13篇
  2002年   8篇
  2001年   7篇
  2000年   7篇
  1998年   6篇
  1997年   5篇
  1996年   5篇
  1995年   4篇
  1994年   2篇
  1993年   2篇
  1992年   3篇
  1991年   5篇
  1989年   5篇
  1988年   2篇
  1987年   3篇
  1985年   3篇
  1984年   3篇
  1983年   5篇
  1982年   8篇
  1981年   3篇
  1980年   4篇
  1979年   8篇
  1978年   3篇
  1977年   6篇
  1976年   2篇
  1975年   2篇
  1974年   2篇
  1973年   2篇
  1972年   2篇
  1970年   1篇
  1966年   1篇
  1965年   1篇
排序方式: 共有342条查询结果,搜索用时 15 毫秒
341.
Evidence for heterogenes primary MORB and mantle sources,NW Indian Ocean   总被引:1,自引:0,他引:1  
Basalts from 5 Deep Sea Drilling Project (DSDP) sites in the northwest Indian Ocean (Somali Basin and Arabian Sea) have general geochemical features consistent with a spreading origin at the ancient Carlsberg Ridge. However, compared to most MORBS from other oceans they have low normative olivine, TiO2, and Zr contents. There is no evidence that the mantle source of these northwest Indian Ocean basalts was enriched in incompatible elements relative to the Atlantic and Pacific ocean mantles. In detail, incompatible element abundances in these DSDP basalts establish that they evolved from several compositionally distinct parental magmas. In particular, basalts from site 236 in the Somali Basin have relatively high SiO2 and low Na, P, Ti, and Zr contents. These compositional features along with low normative olivine contents are similar to those proposed for melts derived by two-stage (or dynamic) melting. Published data also indicate there is no enrichment in incompatible elements at the southwest Indian Ocean triple junction, although southwest Indian Ocean basalts have slightly higher 87Sr/86Sr than normal Atlantic MORB. The data suggest that there are significant subtle geochemical variations in the Indian Ocean mantle sources, but are insufficient to show whether these variations have a systematic temporal or geographic distribution.  相似文献   
342.
The Bali Action Plan and Cancun agreements on Reducing Emissions from Deforestation and forest Degradation, plus forest conservation, sustainable management of forests and enhancement of forest carbon stocks (REDD+) have encouraged demonstration activities as part of Readiness and a step towards national approaches. This has enabled important growth in pilot and demonstration projects. Yet an understanding about how these projects are connected and contribute to national-level technical, policy, and institutional preparedness (Readiness) for REDD+ is lacking. This article examines the linkages between national processes and the private-sector-driven Kasigau Corridor REDD+ project in Kenya. The study reveals interesting cross-scale interactions that have increased over time and have high potential for harnessing national-level processes through lessons from the project level. Key innovations from the Kasigau Corridor Project include the implementation of REDD+ in dry forests, operationalization of conservation easements in the context of REDD+, and demonstration of potential ways of obtaining upfront finance for REDD+. The study also provides a number of key recommendations for Kenya and REDD+ in general, including official endorsement of stand-alone REDD+ projects under national Readiness schemes and exploring jurisdictional and nested REDD+ approaches. Additionally, more accommodating national-level frameworks for attracting private-sector engagement and investments, and for integrating, scaling-out, or scaling-up lessons from such projects, would be needed to enhance national REDD+ Readiness.  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