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   4949篇
  免费   140篇
  国内免费   61篇
安全科学   270篇
废物处理   170篇
环保管理   1251篇
综合类   536篇
基础理论   1368篇
环境理论   8篇
污染及防治   998篇
评价与监测   320篇
社会与环境   172篇
灾害及防治   57篇
  2023年   57篇
  2022年   55篇
  2021年   55篇
  2020年   65篇
  2019年   69篇
  2018年   122篇
  2017年   134篇
  2016年   179篇
  2015年   121篇
  2014年   162篇
  2013年   407篇
  2012年   233篇
  2011年   306篇
  2010年   204篇
  2009年   237篇
  2008年   262篇
  2007年   257篇
  2006年   229篇
  2005年   195篇
  2004年   180篇
  2003年   149篇
  2002年   141篇
  2001年   86篇
  2000年   94篇
  1999年   72篇
  1998年   75篇
  1997年   61篇
  1996年   65篇
  1995年   83篇
  1994年   74篇
  1993年   68篇
  1992年   57篇
  1991年   39篇
  1990年   35篇
  1989年   36篇
  1988年   30篇
  1987年   39篇
  1986年   41篇
  1985年   40篇
  1984年   45篇
  1983年   44篇
  1982年   52篇
  1981年   44篇
  1980年   32篇
  1979年   15篇
  1978年   29篇
  1977年   16篇
  1976年   13篇
  1972年   7篇
  1971年   9篇
排序方式: 共有5150条查询结果,搜索用时 151 毫秒
361.
This research demonstrates the contribution of phenomenological inquiry within the realm of geographic and environmental planning. The contention is that a focus on the wide range of individual meanings and values ascribed to landscapes, a marginalized element in many planning assessments, can bring out data to more substantively inform decision making, A case study of user meanings imparted to residual waterfront land in Hoboken, New Jersey, USA, suggests that such property provides an array of amenities to residents. Most importantly, it expands the range of recreational activities, creates visual relief from the monotonous urban milieu, and provides scenic vistas to promote an awareness of the quality of life still possible in cities. The study concludes that planners can use phenomenology to generate data for more judicious decision making.  相似文献   
362.
This paper addresses questions of affective responses of residents of rural Arizona to changes in proximate community and riparian landscapes and the congruence of their perceptions of change with physical measures of change in those landscapes. Based on findings and concepts from previous studies, perceptions of change were assessed using a mail survey. Physical measures of land use and vegetation change were obtained from aerial photography for two points in time spanning approximately 13 years and were analyzed using a geographic information system. Significant differences were found in perceptions of change in the community and riparian landscapes. In contrast with previous findings, a majority of respondents found the changes as either improving or having no effect on landscape quality. Those who were more frequent users of the riparian landscape tended to be more aware of changes in it. The findings also suggest challenges for planners and resource managers working in rural areas adjacent to riparian landscapes.  相似文献   
363.
364.
Numerical site-specific chemical and biological criteria were established to assess the impact of a pilot dredging project on water quality at the New Bedford Harbor, Massachusetts, USA, Superfund site. Because most existing chemical concentrations in the water column and indigenous biota exceeded federal and state water quality limits, the derivation of site-specific criteria was required. Prior to any operational phases of the project (i.e., dike construction, dredging), criteria values were developed from background concentrations of PCBs and metals in water and biota, as well as for the toxic effects of water quality on the biota. During each operational phase of the project, water samples were collected, analyzed within 16 h, and the data supplied to a management committee in order to assess the environmental impact of the previous days' operation. The ambient unfiltered water concentration of PCBs and metals were the only chemical or biological criteria exceeded. Modification of the next days' operations resulted in a return of these concentrations to background levels. The combined use of site-specific criteria and a real-time decision making management process allowed for successful completion of this project with a minimal effect on water quality.  相似文献   
365.
ABSTRACT: A risk-based model is presented for determining action levels in real-time operation of public water supplies under drought conditions. The model, applicable to surface water supplies, is built around the almost universally adopted structure for drought management, a sequence of increasingly stringent measures to reduce demand. Action levels are determined by finding minimum storage levels that will satisfy a prescribed set of probability constraints over the remainder of a drawdown-refill cycle. Results are presented for the City of Raleigh, NC.  相似文献   
366.
ABSTRACT: Certain physical and chemical properties of soil vary with soil water content. The relationship between these properties and water content is complex and involves both the pore structure and constituents of the soil solution. One of the most economical techniques to quantify soil water content involves the measurement of electrical resistance of a dielectric medium that is in equilibrium with the soil water content. The objective of this research was to test the reliability and accuracy of fiberglass soil-moisture electrical resistance sensors (ERS) as compared to gravimetric sampling and Time Domain Reflectometry (TDR). The response of the ERS was compared to gravimetric measurements at eight locations on the USDA-ABS Walnut Gulch Experimental Watershed. The comparisons with TDR sensors were made at three additional locations on the same watershed. The high soil rock content (≥45 percent) at seven locations resulted in consistent overestimation of soil water content by the ERS method. Where rock content was less than 10 percent, estimation of soil water was within 5 percent of the gravimetric soil water content. New methodology to calibrate the ERS sensors for rocky soils will need to be developed before soil water content values can be determined with these sensors.  相似文献   
367.
368.
During the winters of 1978–79 and 1979–80, a 500-kV electrical transmission right-of-way (r-o-w) was constructed across the Red Lake Peatland in northwestern Minnesota, the largest contiguous peatland in the lower 48 states of the USA. Immediately before, and for two years following construction, vascular vegetation was monitored within the r-o-w and in undisturbed control areas. Monitoring was carried out in five vegetation types: a thicket swamp, a low shrub bog, a graminoid fen, a treed bog, and a treed fen. Evaluation of construction impacts was based on vegetation structure, irrespective of species composition, and on community composition (species data for low shrubs and herbs). Construction eliminated trees from the r-o-w. Vegetation structure, excluding trees, was markedly altered in the two bog types and the treed fen type in the first postconstruction growing season. By the second season, measurable recovery to control levels had begun. The sample plots were placed into a previously developed vegetation classification system for the Red Lake Peatland, on the basis of herbs and low shrubs. There was a shift in composition in the low shrub bog and in the treed vegetation types following construction. Results of both methods of data analysis were consistent. Major vegetation changes following construction occurred in the low shrub bog and treed types. The open, low-stature fen types showed almost no changes related to construction. Even in the affected types, all vegetation strata except trees were returning to their preconstruction status by the second growing season following construction.  相似文献   
369.
A series of studies examined the effects of labelled meaning on affective response to housing scenes. Students at Ohio State University assessed their feelings towards imagined housing (public or private) and cities (Memphis, Houston and San Francisco). Expected differences in the affective quality were found. Responses to color photographs of specific housing scenes labelled as either private condominiums or public housing were obtained. Differences in scene-affect as a function of labelled meaning were found. Responses to housing scenes labelled as located in either Memphis, Houston or San Francisco revealed no differences in scene-affect as a function of label meaning. This latter finding was confirmed in a non-repeated measure examination. Differences in the fittingness, potency or relevance of the information provided may account for the pattern of findings.  相似文献   
370.
This paper examines the applicability of attribution theory research to safety management in industry. Behavioral research on the perception of causality is reviewed in relation to: (a) how individual workers appraise the risks associated with various workplace hazards, (b) responses of first-line supervisors to safety incidents, and (c) the impact of upper management on the safety climate of the organization. Particular attention is given to the sources of attributional bias most likely to exist in organizational settings. Conclusions and safety program recommendations are presented.  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