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   1248篇
  免费   37篇
  国内免费   27篇
测绘学   29篇
大气科学   341篇
地球物理   46篇
地质学   178篇
海洋学   130篇
天文学   3篇
综合类   68篇
自然地理   517篇
  2024年   3篇
  2023年   6篇
  2022年   30篇
  2021年   29篇
  2020年   33篇
  2019年   57篇
  2018年   60篇
  2017年   61篇
  2016年   66篇
  2015年   53篇
  2014年   45篇
  2013年   233篇
  2012年   39篇
  2011年   50篇
  2010年   45篇
  2009年   46篇
  2008年   53篇
  2007年   63篇
  2006年   42篇
  2005年   39篇
  2004年   32篇
  2003年   32篇
  2002年   27篇
  2001年   22篇
  2000年   27篇
  1999年   24篇
  1998年   21篇
  1997年   12篇
  1996年   5篇
  1995年   8篇
  1994年   4篇
  1993年   5篇
  1992年   2篇
  1991年   7篇
  1989年   1篇
  1988年   7篇
  1987年   4篇
  1986年   3篇
  1985年   5篇
  1984年   4篇
  1983年   4篇
  1982年   1篇
  1980年   1篇
  1978年   1篇
排序方式: 共有1312条查询结果,搜索用时 0 毫秒
211.
In recent years, physical geography in Mexico has contributed to the enterprise of geographical science by integrating with fields of study closely related to topics of sustainable development. This paper outlines the contribution of the discipline to environmental public policy development, particularly ecological land use planning and integrated watershed management. In terms of applications, physical geography appears to have reached a stage of maturity in Mexico. However, it must offer a stronger leadership in areas such as ecoregional analysis (in an integrated fashion, and not only from the biological‐ecological perspective) and regional vulnerability to global change processes. An excellent opportunity exists for scientists and decision makers to develop a common agenda.  相似文献   
212.
The Australian government Caring for our Country (CfoC) program, first announced in 2008, has sought to build on and enhance previous experience with Australian natural resource management policy. This paper critically examines the initial design, planned delivery, and first round of competitive funding outcomes of the new program. This analysis shows that the initial design and delivery of the CfoC model was ad hoc, politicised, and lacking in transparency. The paper concludes that a more systematic and transparent approach for achieving sustainable environmental outcomes is required in order for this new program to achieve its intended objectives. These implications are of interest to Australian and international geographers, natural resource planners, scientists and policy makers concerned with the design, delivery and outcomes of large natural resource and environmental management programs.  相似文献   
213.
林雄斌  杨家文 《地理研究》2016,35(9):1727-1739
交通运输投资是区域规划和政策制定的重要内容,但交通运输投资对促进经济增长的时空效应仍存在较大争议。在总结交通成本、交通投资与经济增长关系的基础上,建立1997-2013年省级尺度的交通运输投资、劳动力和经济总量的面板模型,综合评估交通投资对经济增长的多尺度时空间效应。研究发现:① 全国层面上看,交通投资对经济增长具有显著的引导效应,其弹性系数为11.4%,但在不同地区这一弹性系数存在显著差异。总体上,在城市化水平和社会基础较好的东部和东北地区,交通运输投资对社会经济增长的作用更加明显。② 在时间尺度上,随着中国城市化水平的不断扩大,交通投资对经济增长的作用也逐渐增强。③ 在考虑交通投资和经济总量时间滞后性之后,在全国层面上,当期交通投资和前期交通运输投资对经济的增长作用程度大致相同,但相对中西部地区而言,东部地区当期交通投资对经济增长作用更加显著。考虑到交通运输投资的这种时空差异,应根据不同地区不同发展阶段的特点,采取谨慎地投资策略以强化对经济增长的引导作用。  相似文献   
214.
This article examines the potential geographic inequities between major hazard events and U.S. presidential disaster declarations at the county level from 1965 through 2004. The previous literature suggests that the disaster declaration process is highly politicized and not necessarily based on need. We hypothesize that there is a spatial inequity between the receipt of disaster declarations and the distribution of major hazard events. The results indicate that the geographic distribution of disaster declarations is not totally explained by the spatial pattern of major hazard events. In some locales, state experience in submitting disaster requests and achieving success translates into more disaster declarations (holding everything else constant), providing further evidence of the political nature of the process.  相似文献   
215.
Abstract

Most traditional segregation measures, such as the index of dissimilarity D, fail to distinguish spatial patterns effectively. Previously proposed spatial measures modifying D suffer from several shortcomings. This article describes a general spatial segregation index based upon the concept of composite population counts, which are derived from grouping people in neighboring areas together to account implicitly for spatial interaction of groups across unit boundaries. The suggested spatial index can overcome the disadvantages of previous indices and can assess the spatial extent of the segregated clusters. The results offer a more comprehensive depiction of spatial segregation of a region.

  相似文献   
216.
While linguistic diversity is an integral component of cultural landscapes, the spatial depiction of languages fails to represent all community members. Language is difficult to map and established guidelines are lacking. The perception of power conveyed is arguably the most meaningful design issue in language mapping, as most language maps inaccurately show one language per place. This research examines the cartographic visualization of linguistic diversity, contributing to our understanding of the perception of power through cartographic decisions, with the application of a linguistic diversity index. The resulting maps serve as new figures for linguistic diversity lessons in educational contexts.  相似文献   
217.
The Organization for Economic Co-operation and Development (OECD) has identified population aging as one of the most important challenges facing OECD countries and has highlighted the need for people to work longer and for job prospects for older workers to be enhanced. This article provides a summary review of a recent OECD report, Ageing and Employment Policies—Live Longer, Work Longer, as a platform to highlight differences between countries in demographic profiles and projections and in patterns of formal labor market participation among older workers. Drawing on selected information from a broader evidence base, it unveils important differences between countries in the scale of demographic and associated labor market challenges. It also explores factors affecting labor market transitions among older workers and age-related and other barriers to paid work among older people, emphasizing the diversity of experience between individuals. Finally, it highlights some strategic challenges for policy.  相似文献   
218.
This article addresses the need to better understand the complex interactions between climate, human activities, vegetation responses, and surface ozone so that more informed air-quality policy recommendations can be made. The impacts of intraseasonal climate variations on ozone levels in Tucson, Arizona from April through September of 1995 to 1998 are determined by relating variations in ozone levels to variations in atmospheric conditions and emissions of ozone's precursor chemicals, volatile organic compounds (VOCs) and nitrogen oxides (NOx), and by determining month-specific atmospheric conditions that are conducive to elevated ozone levels. Results show that the transport of ozone and its precursor chemicals within the Tucson area causes the highest ozone levels to be measured at a downwind monitor. The highest ozone levels occur in August, due in part to the presence of the North American monsoon. Atmospheric conditions conducive to elevated ozone concentrations differ substantially between the arid foresummer (May and June) and the core monsoon months ( July and August). Transport of pollution from Phoenix may have a substantial impact on elevated ozone concentrations during April, May, and June, while El Paso/Ciudad Juarez –derived pollution may contribute significantly to elevated ozone concentrations in August and September. Two broad policy implications derive from this work. Regional pollutant transport, both within the U.S. and between the U.S. and Mexico, is a potential issue that needs to be examined more intensively in future studies. In addition, spatiotemporal variations in sensitivities of ozone production require the adoption of both NOx and VOC control measures to reduce ozone levels in the Tucson area.  相似文献   
219.
220.
Titles Of Theses     

This essay questions the effectiveness of nuclear winter modeling as a means of impacting nuclear policy and changing public attitudes about nuclear issues. In nuclear winter modeling, humanistic concern over the possibility of global environmental destruction is cloaked in the ostensibly neutral language of science. Nuclear winter modeling attempts to apply rational argument to an issue that is rooted instead in human affect and morality. The implications of this misappropriation are discussed in terms of the dehumanizing nature of the images conjured up by nuclear winter, its attention to the effects of nuclear weapons rather than deeper structural problems, and its political ambiguity as a function of unresolvable uncertainty in model results.  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