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   284篇
  免费   3篇
  国内免费   6篇
安全科学   50篇
废物处理   13篇
环保管理   52篇
综合类   29篇
基础理论   59篇
污染及防治   52篇
评价与监测   20篇
社会与环境   12篇
灾害及防治   6篇
  2023年   2篇
  2022年   6篇
  2020年   1篇
  2019年   3篇
  2018年   6篇
  2017年   8篇
  2016年   4篇
  2015年   2篇
  2014年   7篇
  2013年   18篇
  2012年   14篇
  2011年   20篇
  2010年   13篇
  2009年   21篇
  2008年   16篇
  2007年   17篇
  2006年   16篇
  2005年   10篇
  2004年   7篇
  2003年   13篇
  2002年   8篇
  2001年   7篇
  2000年   7篇
  1999年   5篇
  1998年   8篇
  1997年   3篇
  1996年   4篇
  1995年   5篇
  1994年   5篇
  1993年   11篇
  1992年   6篇
  1991年   8篇
  1989年   2篇
  1988年   5篇
  1987年   1篇
  1986年   1篇
  1983年   1篇
  1979年   2篇
排序方式: 共有293条查询结果,搜索用时 453 毫秒
81.
This review summarises current knowledge about production volumes, physico-chemical properties, analysis, environmental occurrence, fate and behaviour and human exposure to the "novel" brominated flame retardants (NBFRs). We define the term NBFRs as relating to BFRs which are new to the market or newly/recently observed in the environment. Restrictions and bans on the use of some polybrominated diphenyl ether (PBDE) formulations, in many jurisdictions, have created a market for the use of NBFRs. To date, most data on NBFRs have arisen as additional information generated by research designed principally to study more "traditional" BFRs, such as PBDEs. This has led to a wide variety of analytical approaches for sample extraction, extract purification and instrumental analysis of NBFRs. An overview of environmental occurrence in abiotic matrices, aquatic biota, terrestrial biota and birds is presented. Evidence concerning the metabolism and absorption of different NBFRs is reviewed. Human exposure to NBFRs via different exposure pathways is discussed, and research gaps related to analysis, environmental sources, fate, and behaviour and human exposure are identified.  相似文献   
82.
This article discusses the ecological and cultural criteria underlying the management practices for protected areas in France. It examines the evolution of French conservation from its roots in the 19th century, when it focused on the protection of scenic landscapes, to current times when the focus is on the protection of biodiversity. However, biodiversity is often socially defined and may not represent an ecologically sound objective for conservation. In particular, we question the current approach to protecting a specific type of biodiversity that is at the basis of traditional landscape but does not value systems that are left to develop naturally (i.e., without significant human intervention). We present several examples of current attempts in France and Europe to managing traditional ecosystems and then discuss the values that exist in systems that develop naturally. We feel the latter systems often have much to offer in terms of biodiversity as well as providing important sites for the study of dynamic ecological communities in an ever-changing world.  相似文献   
83.
84.
To examine variation in diet and daily ration of the bonnethead shark, Sphyrna tiburo (Linnaeus 1758), animals were collected from three areas in the eastern Gulf of Mexico: northwest Florida (∼29°40′N, 85°13′W), Tampa Bay near Anclote Key (∼28°10′N, 82°42.5′W), and Florida Bay (∼24°50′N, 80°48′W) from March through September, 1998–2000. In each area, diet was assessed by life stage (young-of-the year, juveniles, and adults) and quantified using five indices: percent by number (%N), percent by weight (%W), frequency of occurrence (%O), index of relative importance expressed on a percent basis (%IRI), and %IRI based on diet category (%IRIDC). Diet could not be assessed for young-of-the-year in Tampa Bay or Florida Bay owing to low sample size. Diet analysis showed an ontogenetic shift in northwest Florida. Young-of-the-year stomachs from northwest Florida (n = 68, 1 empty) contained a mix of seagrass and crustaceans while juvenile stomachs (n = 82, 0 empty) contained a mix of crabs and seagrass and adult stomachs (n = 39, 1 empty) contained almost exclusively crabs. Crabs made up the majority of both juvenile and adult diet in Tampa Bay (n = 79, 2 empty, and n = 88, 1 empty, respectively). Juvenile stomachs from Florida Bay (n = 72, 0 empty) contained seagrass and a mix of crustaceans while adult stomachs contained more shrimp and cephalopods (n = 82, 3 empty). Diets in northwest Florida and Tampa Bay were similar. The diet in Florida Bay was different from those in the other two areas, consisting of fewer crabs and more cephalopods and lobsters. Plant material was found in large quantities in all stomachs examined from all locations (>15 %IRIDC in 6 of the 7 life stage-area combinations, >30 %IRIDC in 4 of the 7 combinations, and 62 %IRIDC in young-of-the-year diet in northwest Florida). Using species- and area-specific inputs, a bioenergetic model was constructed to estimate daily ration. Models were constructed under two scenarios: assuming plant material was and was not part of the diet. Overall, daily ration was significantly different by sex, life stage, and region. The bioenergetic model predicted increasing daily ration with decreasing latitude and decreasing daily ration with ontogeny regardless of the inclusion or exclusion of plant material. These results provide evidence that bonnetheads continuously exposed to warmer temperatures have elevated metabolism and require additional energy consumption to maintain growth and reproduction. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
85.
86.
87.
This research examines the relations of the cognitive factors of beliefs and fears proposed by Price (1982) with the revised Jenkins Activity Survey (JAS) factors of achievement striving and impatience-irritability as well as the outcome measures of job and class performance. Results provide support for Spence, Helmreich, and Pred (1987), and Spence, Pred, and Helmreich's (1989) findings of the positive association between achievement striving and class performance but provide limited support for Price's (1982) model.  相似文献   
88.
INTRODUCTION: This longitudinal field study was designed to encourage Appalachian coal miners in West Virginia and Pennsylvania to engage in hearing-protection behaviors. METHOD: Participants were mailed postcards that featured either a positive, negative, or neutral message on the outside of the postcard and a message encouraging hearing protection behaviors on the inside. The first posttest measurement of the effectiveness of the persuasive messages was conducted about a week after the postcards were mailed. The delayed posttest measurement was conducted six weeks later. RESULTS: Responses from 307 coal miners revealed that the positive or neutral messages generated significantly more self-reported hearing protection behaviors than the negative message. Identical results were obtained in a delayed posttest assessment of miners' self-reported hearing protection behaviors. The positive message was also more effective than either the neutral or negative message in preventing defensive mechanisms from emerging over time. IMPACT ON INDUSTRY: Positive and neutral messages were convincingly more successful than negative messages in facilitating self-reported hearing protection behaviors among coal miners. Similarly, the positive messages kept defensive processes at bay.  相似文献   
89.
In this study, we examined the role of organizational level as a moderator of the relationships of procedural and distributive justice with seven employee attitudes and behaviors. Based on social identity and resource allocation theories, we suggested an allocational model of authority in organizations. We posited that lower rank encourages a more process‐oriented perspective that emphasizes procedural concerns while higher rank imbues a more result‐oriented perspective that emphasizes distributive outcomes. We considered the cultural context that characterized work relationships in our sample of respondents from a Chinese state‐owned enterprise. Significant sets of interactions supported the predicted relationships of procedural justice with three outcomes at lower levels and distributive justice with four outcomes at higher levels. Implications and extensions of these findings are considered. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
90.
ABSTRACT: :The model described herein was used to assess effects of the Suwannee River sill (a low earthen dam constructed to impound the Suwannee River within the Okefenokee National Wildlife Refuge to eliminate wildfires) on the hydrologic environment of Okefenokee Swamp, Georgia. Developed with Arc/Info Macro Language routines in the GRID environment, the model distributes water in the swamp landscape using precipitation, inflow, evapotranspiration, outflow, and standing water. Water movement direction and rate are determined by the neighborhood topographic gradient, determined using survey grade Global Positioning Systems technology. Model data include flow rates from USGS monitored gauges, precipitation volumes and water levels measured within the swamp, and estimated evapotranspiration volumes spatially modified by vegetation type. Model output in semi‐monthly time steps includes water depth, water surface elevation above mean sea level, and movement direction and volume. Model simulations indicate the sill impoundment affects 18 percent of the swamp during high water conditions when wildfires are scarce and has minimal spatial effect (increasing hydroperiods in less than 5 percent of the swamp) during low water and drought conditions when fire occurrence is high but precipitation and inflow volumes are limited.  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