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   2328篇
  免费   174篇
  国内免费   63篇
安全科学   145篇
废物处理   25篇
环保管理   1069篇
综合类   606篇
基础理论   374篇
环境理论   2篇
污染及防治   57篇
评价与监测   62篇
社会与环境   131篇
灾害及防治   94篇
  2023年   20篇
  2022年   39篇
  2021年   52篇
  2020年   54篇
  2019年   50篇
  2018年   59篇
  2017年   85篇
  2016年   93篇
  2015年   93篇
  2014年   82篇
  2013年   126篇
  2012年   83篇
  2011年   140篇
  2010年   90篇
  2009年   116篇
  2008年   112篇
  2007年   117篇
  2006年   109篇
  2005年   87篇
  2004年   73篇
  2003年   76篇
  2002年   55篇
  2001年   66篇
  2000年   57篇
  1999年   69篇
  1998年   44篇
  1997年   40篇
  1996年   46篇
  1995年   40篇
  1994年   28篇
  1993年   17篇
  1992年   23篇
  1991年   19篇
  1990年   14篇
  1989年   13篇
  1988年   13篇
  1987年   21篇
  1986年   22篇
  1985年   25篇
  1984年   22篇
  1983年   13篇
  1982年   12篇
  1980年   15篇
  1979年   17篇
  1978年   20篇
  1977年   14篇
  1975年   10篇
  1973年   16篇
  1972年   14篇
  1971年   16篇
排序方式: 共有2565条查询结果,搜索用时 453 毫秒
511.
The following is a summary of work carried out in urban planning design at the University of Newcastle upon Tyne. The main objectives of the study were to identify those factors which condition the use of a street and to understand the physical and emotional impacts of the street and its different characteristics upon its users; eventually this led to establishing facts involving the criteria which contribute to making streets which would enrich peoples’ experience and would contribute to the urban life and excitement of all.  相似文献   
512.
计划生育是“天下第一难的事”,这是有一定道理的。但是,计划生育之“难”的原因?却很少有人专门研究或探及。本文试图通过计划生育工作实践,从宏观上对此做一点探讨,以便在改革开放的大潮中,进一步抓住控制人口的主要矛盾。把握规律,针对问题,采取对策,做好工作,为促进改革开放、发展经济创造良好的人口环境。  相似文献   
513.
人口与资源和环境之间的相互关系是一个历史过程。从发生学观点研究特写区域这种关系及其变化规律是区域历史地理研究的核心内容,探索历史上人口与资源和环境之间相互关系的规律及其演化机制,可为区域国土规划与整治中人口、资源与环境发展提供必要的历史借鉴和客观依据。同时,国土规划与整治的现实任务亦为区域历史地理研究提供了发展机遇。  相似文献   
514.
Land degradation continues to be a major threat to local and national food security. With limited potential to develop new land, any increase in agricultural production must be sought largely through the better use of land already under cultivation. Concerns for the global environment associated with agriculture worldwide have also increased in recent years and require more coordinated efforts at global and national levels with decentralisation of activities at the local level.
This article presents an overview of land resources potential for food production, the processes and extent of land degradation and its economic and environmental costs and impacts, and highlights some macro-economic policies and institutional measures for the prevention of land degradation and rehabilitation of degraded lands. A people-centred programme is presented as a basis for decentralising activities for sustainable land use and land management. Finally, the need for better coordinated efforts of concerned UN, multinational agencies and NGOs for the implementation of Agenda 21 and related conventions is stressed.  相似文献   
515.
Several approaches can be used to define and construct visual buffer strips around proposed new facility sites in a forested environment. A visual buffer strip of a given value, defines a region around an object within which the probability of an unblocked view of all or portions of it by an observer are less than the buffer strip probability value. Two primary approaches are used to define visual buffer strips that take into account the size of the vegetative elements and their individual effects on visibility. Several variations and combinations of the approaches are possible. One approach defines a visual buffer strip based on the average probability of a clear view of points along the object by an observer; the other approach is based on the visibility of the feature as a whole. The computation and construction of visual buffer strips based on these two concepts are presented. Comparisons of the two approaches for specific feature shapes are also described.  相似文献   
516.
ABSTRACT: A research project was undertaken for the U.S. Army Corps of Engineers to determine the relative utility and effectiveness of four well-known multicriteria decision making (MCDM) models for applications in realistic water resources planning settings. A series of experiments was devised to examine the impact of rating and ranking procedures on the decision making behavior of users (e.g., planners, managers, analysts, etc.) when faced with situations involving multiple evaluation criteria and numerous alternative planning projects. The four MCDM models tested were MATS-PC, EXPERT CHOICE, ARIADNE, and ELECTRE. Two groups of analysts and decision makers were tested. One group consisted of experienced U.S. Army Corps planners, while the other was comprised of graduate students. Based on a series of nonparametric statistical tests, the results identified EXPERT CHOICE as the preferred MCDM model by both groups based largely on ease of use and understandability. ARIADNE fostered the largest degree of agreement within and among the two groups of individuals tested. The tests also lend support to the claim that rankings are not affected significantly by the choice of decision maker (i.e., who uses any of these MCDM models) or which of these four models is used.  相似文献   
517.
Citizens from two communities were questioned regarding the sources from which they have previously obtained information about environmental hazards and their preferences for different communication channels. Three ethnic groups—whites, blacks, and Mexican-Americans—were represented among those questioned. While all three ethnic groups described similar patterns of past information receipt, it was found that Mexican-Americans obtained more information through social network contacts than whites or blacks. Ethnic differentials emerged when citizens were asked about preferred sources for information receipt. While radio was identified as desirable by all three groups, only minority citizens expressed a preference for local television as a dissemination mode and only Mexican-Americans favored neighborhood meetings. Mailed dissemination and newspapers were preferred primarily by whites and blacks. The implications of the results for the conduct of hazard information dissemination are examined.  相似文献   
518.
Extensive losses of semi‐natural rural biotopes have led to pressures for conservation and habitat creation. Of particular concern is the loss of large‐scale structure and regional distinctiveness. If this is to be regained, planners will require both an effective body of theory relating to large‐scale visual and ecological cohesion, and effective methods of implementation. This study reviews the value of landscape ecology as a theoretical framework and discusses some applications, with particular reference to the re‐forestation of lowland Britain.  相似文献   
519.
The growing political and public profile of tourism has led to the need for local estimates of its economic impact and importance, especially the number of jobs involved. In particular there is a need to produce spatially and temporally disaggregated estimates of visitor numbers, visitor spending and tourism‐related employment. This paper outlines and uses an indirect non‐survey method for estimating the tourism‐related workforce in local areas proposed by Roger Vaughan. The method is applied to recently published 1987 Census of Employment data for Yorkshire and Humberside.  相似文献   
520.
One of the most pressing problems facing wilderness managers in the ecologically fragile Drakensberg Mountains, South Africa, is that of path erosion, since it detracts from the wilderness experience and is very costly to remediate. As increasing demand for wilderness and outdoor recreation places greater pressure on paths and trails, it will be necessary to increase path network size and capacity, and it is important that new paths are routed such that maintenance requirements are minimal. This study describes the development of a technique based on the site and environmental variables of rainfall, topographic slope, and lithology, which enables assessment of path erosion risk before paths are planned and constructed. The technique was tested on a path at the Drakensberg resort of Loteni, and showed good correlation with actual path degradation. When used as a tool in path network planning, it can aid in the selection of low-maintenance routes and also help in planning maintenance budgets.  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