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   1097篇
  免费   111篇
  国内免费   76篇
测绘学   135篇
大气科学   133篇
地球物理   119篇
地质学   217篇
海洋学   128篇
天文学   2篇
综合类   131篇
自然地理   419篇
  2024年   16篇
  2023年   24篇
  2022年   52篇
  2021年   44篇
  2020年   49篇
  2019年   46篇
  2018年   41篇
  2017年   78篇
  2016年   65篇
  2015年   53篇
  2014年   87篇
  2013年   75篇
  2012年   50篇
  2011年   80篇
  2010年   78篇
  2009年   57篇
  2008年   73篇
  2007年   43篇
  2006年   84篇
  2005年   50篇
  2004年   27篇
  2003年   20篇
  2002年   34篇
  2001年   10篇
  2000年   15篇
  1999年   7篇
  1998年   5篇
  1997年   4篇
  1996年   1篇
  1995年   3篇
  1994年   2篇
  1993年   2篇
  1992年   2篇
  1991年   1篇
  1989年   2篇
  1987年   2篇
  1983年   2篇
排序方式: 共有1284条查询结果,搜索用时 15 毫秒
121.
本文首先列举了近几年发生的几起典型的境外组织、机构和人员对我国进行的非法测绘案件,分析了空间数据的重要性以及公众对空间数据安全的认识误区,提出了制定我国空间数据安全政策的建议。  相似文献   
122.
粮食主产区河南省经济欠发达,粮食总产位居前列,以耕地压力指数对粮食安全进行定量分析和计算,采用重心量算模型和空间变差函数对河南省粮食安全的空间格局和变化特征进行了分析.研究结果表明:研究时段内,耕地压力指数小于1的县区主要位于河南省东部,呈现先增加后减少的趋势;最高值位于西北地区,最高值与最低值的差距逐步扩大,重心从东南平原区向西北山地区转移,迁移轨迹符合耕地变化情况.耕地压力指数的空间特征结构性上表现出一定的随机性,粮食安全总体格局表现出一定的稳定性,而各向异性表现明显,其中以南北的差距最为显著.  相似文献   
123.
网格在地理空间数据传输中的应用研究   总被引:1,自引:0,他引:1  
地理空间数据传输是构建网格GIS的基础。本文从网格GIS服务的构建、地理空间数据传输协议、地理空间数据传输格式、地理空间数据传输安全机制以及地理空间数据传输速度等方面网格在地理空间数据传输中的应用进行了研究,提出了基于GridGML语言的地理数据网络传输策略。最后通过网络评估和网络负载平衡,提出了GridFTP与HTTP协议相结合的地理空间数据快速传输方案。  相似文献   
124.
Despite rapid economic growth, India has not seen the improvements in food and nutritional security that other developing countries have had. This “Asian enigma” has generated a wealth of economistic analyses seeking to explain the persistence of poor nutrition, yet few studies have looked at everyday experiences of changing food systems, and how this impacts nutritional practices as well as the processes of subject formation. In this paper, I draw on qualitative research conducted in Uttarakhand, North India and examine how state-led shifts in agricultural production have resulted in changing food consumption practices and diminished perceptions of health. Villagers link this decreased health to increased chemicals in home-produced food, greater dependence on the market for food purchases, and generational changes in dietary preferences. Despite villagers’ cognizance of the negative health effects of these practices, they largely view these byproducts of capitalistic development with an air of inevitability. Following Mansfield (2011) this paper contributes to the political ecology of health literature by employing the concept of food as a “vector of intercorporeality” (Stassart and Whatmore, 2003:449) and bringing this into conversation with a poststructuralist understanding of subjectivity. I argue that within shifting landscapes of agriculture production and food consumption, notions of diminished health are indicative of the complex and always incomplete processes of subject formation. I view shifting health perceptions as intimate bodily resistances to agricultural development, and conclude that within agricultural development programs a focus on bodily health and well-being is a fecund platform for further experimental research that seeks to imagine development differently.  相似文献   
125.
This paper offers a systematic analysis of the concepts and contexts that frame the climate-smart agriculture (CSA) discourse in the academic and policy literature. Documents (n?=?113) related to CSA and published in peer-reviewed journals, books, working papers, and scientific reports from 2004 to 2016 were reviewed. Three key trends emerged from the analysis: studies are biased towards global policy agendas; research focuses on scientific and technical issues; and the integration of mitigation, adaptation, and food security (the three pillars of CSA) is becoming a popular scholarly solution. Findings suggest that CSA is a fairly new concept used to describe a range of adaptation and mitigation practices without a specific set of criteria. Although CSA is often framed around the three pillars, the underlying issues constructing the discourse differ at global, developing, and developed country scales. Although there is increasing research on developing countries, particularly in relation to how CSA can transform smallholder agriculture, there is a paucity of research documenting the experiences from developed countries. The findings suggest that research on CSA needs to move beyond solely focussing on scientific approaches and only in certain geographical contexts. If CSA is to be applicable for farmers across the globe, then cross-disciplinary research that is underpinned by broad socio-economic and political contexts is essential to understand how differences in narratives might affect implementation on-the-ground in both developing and developed countries.

POLICY RELEVANCE

Although policy makers are increasingly supportive of the climate-smart agriculture (CSA) approach, the rhetoric has largely been developed on the basis of scientific and technical arguments. The political implications of varying perspectives have resulted in a growing divide between how developing and developed countries frame solutions to the impacts of climate change on agriculture under the 2015 Paris Agreement. Different framings are part of the explanation for why the scope of CSA is being rethought, with the scientific community redirecting attention to seeking a separate work programme under the United Nations Framework Convention on Climate Change (UNFCCC). The current policy framing of CSA will give no new policy direction unless it grounds itself in the smallholder farmer and civil society contexts.  相似文献   
126.
农用地多功能利用是黑龙江省沿边开放带土地利用效率提升及生态经济协调发展的客观要求,农用地利用多功能性评价是其基础工作。该文系统地研究了农用地利用多功能性评价方法,测度了1996年、2004年、2013年黑龙江省农用地利用多功能状态及期间变化。研究表明,1996~2013年黑龙江省农用地利用总功能缓慢提高,多功能协调性逐步提升;农用地利用由单一功能逐渐向多功能转变。为扩大农用地利用多功能整体效应并提高农用地利用多功能协调性,稳定生产功能、加快提高经济功能、重点遏制生态功能退化、逐步提高社会功能是沿边开放带今后的农用地利用方向。  相似文献   
127.
News Notes     
《The Journal of geography》2012,111(6):295-296
Abstract

Santa Claus and His Elves: by Mauri Kunnas, New York: Harmony House, 1981. 48 pp., and illus. $7.95 cloth.

Anno's Journey: by Mitsumasa Anno, New York: Philomee Books, 1983.50 pp., and illus. $10.95 cloth.

The Sea People: by Jörg Müller and Jörg Steiner, New York: Schocken Books, 1982.36 pp., and illus. $14.95 cloth.

The Lorax: by Dr. Seuss, New York: Random House, 1971. 62 pp., and illus. $5.95 cloth.

Continents in Collision: by Russell Miller, Alexandria, VA: Time-Life Books, 1983. Planet Earth series, edited by Russell Miller and the editors of Time-Life Books. 169 pp., illus., photos, maps, biblio., and index. $14.95 cloth.

South America 2d ed.: by Arthur Morris, Totowa, NJ: Barnes &; Noble, 1982. xii and 276 pp., figs., graphs, tables, photos, maps, biblio., glossary, and index. $17.50 paper.

The Navajo Atlas: Environments, Resources, People, and History of the Diné Bikeyah: by James M. Goodman, Norman, OK: University of Oklahoma Press, 1982. x and 109 pp., illus., maps, photos, refs., and index. $22.50 cloth.

The Geography of Multinationals: by Michael Taylor and Nigel Thrift, eds., New York: St. Martin's Press, 1982.338 pp., figs., graphs, tables, refs., and indexes. $35.00 cloth.  相似文献   
128.
Although the logistics industry provides critical services to all sectors of the economy, few studies exist in economic geography that examine and explain the organizational dynamics of this industry. This article highlights the significance of the logistics industry in contemporary industrialization and argues that an enriched understanding of the interaction between technology and space can be achieved by examining the evolution of an industry that plays a central role in the contemporary economy. We focus on dimensions that are identified as particularly important: organizational, geographic, and risk and security.  相似文献   
129.
江底盾构隧道施工期外水压分布规律的现场试验研究   总被引:1,自引:0,他引:1  
谢红强  何川  李围 《岩土力学》2006,27(10):1851-1855
重庆主城排水过江盾构隧道工程是国家重点环保工程之一,也是目前长江上最大的岩质盾构隧道。隧道采用泥水盾构机施工,其主体结构在施工期及运营期将承受0.6 MPa的高水压。研究高外水压力对隧道的影响具有重要意义,结合隧址区的地形地质及水文条件对施工期作用在盾构主体结构上的水压力进行了现场跟踪测试,探求施工期外水压力的分布规律,为盾构隧道的掘进控制提供参数,并为类似工程提供有益参考。  相似文献   
130.
徐忠  娄昭 《世界地理研究》2004,13(3):25-29,49
当前,世界政治形势处于动荡催生调整,调整蕴含机遇,在单极与多极矛盾的碰撞与互动中,正在形成某种更有效的机制,培育更为成熟、理性竞争的意识,促使各主要大国为世界的持久和平与繁荣共同担负起应有的责任。因此,国家经济安全是世界各国都普遍关注的战略问题。本文首先总结了就当今世界政治发展的四个特点,并在分析国际形势新变化对中国经济安全影响的基础上,提出了维护我国经济安全的六点思考。  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