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   767篇
  免费   10篇
  国内免费   4篇
安全科学   59篇
废物处理   42篇
环保管理   138篇
综合类   68篇
基础理论   230篇
环境理论   1篇
污染及防治   155篇
评价与监测   61篇
社会与环境   23篇
灾害及防治   4篇
  2023年   4篇
  2022年   7篇
  2019年   5篇
  2018年   8篇
  2017年   9篇
  2016年   17篇
  2015年   13篇
  2014年   19篇
  2013年   76篇
  2012年   23篇
  2011年   46篇
  2010年   31篇
  2009年   26篇
  2008年   28篇
  2007年   31篇
  2006年   50篇
  2005年   21篇
  2004年   18篇
  2003年   26篇
  2002年   33篇
  2001年   23篇
  2000年   27篇
  1999年   12篇
  1998年   15篇
  1997年   11篇
  1996年   12篇
  1995年   13篇
  1994年   10篇
  1993年   9篇
  1992年   9篇
  1991年   9篇
  1990年   11篇
  1989年   7篇
  1988年   8篇
  1987年   8篇
  1986年   9篇
  1985年   6篇
  1984年   11篇
  1983年   5篇
  1982年   9篇
  1981年   7篇
  1980年   9篇
  1979年   5篇
  1978年   8篇
  1977年   4篇
  1976年   5篇
  1975年   3篇
  1974年   5篇
  1973年   5篇
  1969年   3篇
排序方式: 共有781条查询结果,搜索用时 31 毫秒
431.
The purpose of the project was to improve the traffic safety impact and net benefits of the negligent operator probation violator hearing conducted by the California Department of Motor Vehicles. The three hearing formats evaluated varied in several aspects including use of license restrictions (rather than suspension or revocation), hearing duration, use of negotiation and contingency contracting, and use of caseload assignment. The two experimental programs differed primarily in the timing of restriction removal, one employing a single fixed-interval restriction and the other a sequential multiphase restriction strategy. The licensing actions used at the project entry hearing were more liberal than anticipated in all hearing formats. The standard hearing format was superior to the others both in overall traffic safety impact and net benefits. The differences between hearing formats in fatal and injury accidents and in countable convictions tended to favor the standard format. Implementation of either alternative format would probably (p≈.80) result in a decline in program net benefits. The application of a behavior modification paradigm was not successful in the project reported here.  相似文献   
432.
The Environmental Council of the European Communities is giving consideration to a procedure to provide a common basis for the assessment and control of potentially polluting development. This discusses the rationale and theory underlying the use of land use planning procedures to control potentially polluting development, and the need for harmonisation of procedures within the European Communities in order to avoid the emergence of pollution havens. It goes on to discuss the proposed Directive on environmental assessment, and the implications of its adoption and incorporation into the planning procedures of the U.K. and other member states.  相似文献   
433.
It is widely agreed that public support is vital to the success of most recycling schemes; the actions of householders are paramount to the success of sustainable waste policies. However, the success of recycling schemes is not just dependent on public participation; it is also dependent on careful planning, effective design and tailoring to local needs.This study has evaluated a kerbside recycling scheme in the north-west of England by comparing the recycling performance of those on alternate collections of residual waste and recyclates with those on weekly residual collections and fortnightly recyclate collections. Three data collection methodologies were adopted: postal questionnaires, set-out rate monitoring, and personal interviews with policy writers.The results demonstrated that alternate collections produce higher recycling set-out rates, suggesting that alternate collections will also generate higher recycling rates. The research showed that if designed and complemented by other services, then an alternate collection system is a realistic waste management approach. However, the local authority and the public appear to use different indicators of success for the scheme. The local authority uses governmental performance indicators (such as best value performance indicators—BVPIs) to measure success, whereas the public's indicators of success tend to focus more on issues such as required changes to established behaviours, convenience and personal preferences.A key recommendation from this study is that all local authorities should carry out local opinion surveys on an annual basis to supplement the BVPIs required by statute. This should help them to fill the information gaps in order to provide a comprehensive, up-to-date and user-responsive waste management service to the public.  相似文献   
434.
The distribution of some heavy metals, namely Cd, Pb, Zn, Fe, Cu, Cr and Mn in epipellic sediments of Igbede, Ojo and Ojora rivers of Lagos was studied weekly in the early summer (November) of 2003. The levels of selected trace metals were determined using Atomic Absorption Spectrophotometer (UNICAM 969 AAS SOLAR). Trends in heavy metal burdens in the sediments revealed weekly variations in all the rivers assessed. Statistical analyses also showed different mean levels of trace metals in the aquatic environments, the distribution of which followed the sequence Fe > Zn > Mn > Pb > Cu > Cr > Cd, Fe > Zn > Cu > Mn > Pb > Cr > Cd and Fe > Zn > Mn > Cu > Cr > Pb > Cd in Igbede, Ojo and Ojora rivers respectively. Fe recorded the highest concentration levels (1,582.95 ± 96.57 μ g/g–1,910.34 ± 723.19 μ g/g) in all the sediments investigated while the Cd levels (0.06 ± 0.10 μ g/g–0.47 ± 0.36 μ g/g) were the lowest. Expectedly, trace metal concentrations in fine grain muddy sediments of the Igbede and Ojo coastline were much higher than those of Ojora which consist of coarse and sandy deposits covering the near shore area. Generally, the results obtained fell within tolerable limits stipulated by World Health Organization (WHO).  相似文献   
435.
Low impact development (LID) and other land development methods have been presented as alternatives to conventional storm water management and site design. Low impact development encourages land preservation and use of distributed, infiltration‐based storm water management systems to minimize impacts on hydrology. Such systems can include shallow retention areas, akin to natural depression storage. Other approaches to land development may emphasize land preservation only. Herein, an analysis of four development alternatives is presented. The first was Traditional development with conventional pipe/pond storm water management and half‐acre lots. The second alternative was Cluster development, in which implementation of the local cluster development ordnance was assumed, resulting in quarter‐acre lots with a pipe/pond storm water management system and open space preservation. The “Partial” LID option used the same lot layout as the Traditional option, with a storm water management system emphasizing shallow depression storage. The “Full” LID used the Cluster site plan and the depression storage‐based storm water management system. The alternatives were compared to the hydrologic response of existing site conditions. The analysis used two design storms and a continuous rainfall record. The combination of land preservation and infiltration‐based storm water management yielded the hydrologic response closest to existing conditions, although ponds were required to control peak flows for the design storms.  相似文献   
436.
OBJECTIVES: To review the research evidence concerning the effects of passengers on teenage driving and crash involvement, and to explore ways to reduce negative effects. METHODS: Review of the international literature on these topics. RESULTS: Passenger presence increases crash risk for teenage drivers, especially when the passengers are other teenagers and especially when they are male. Female passengers do not have the same effects. Teenagers are more susceptible to peer influences than adults. The combination of passenger-induced distraction and driving inexperience can disrupt driving behavior, and there is evidence that teenage driver risk taking increases in vehicles with multiple teenagers. Possible ways to reduce the resulting crash problem include altering the in-vehicle behavior of teenagers or influencing their selection of travel partners. Legal restrictions on passengers with teenage drivers have been found effective in reducing the crash problem. Parental monitoring of teenage driving behavior, and programs aimed at teenagers themselves, could be other options but their efficacy is unproven. It currently is unknown why female passengers have a different effect than males or if that might offer clues about future interventions. CONCLUSIONS: Despite passenger restrictions in the majority of states, 42% of 16- and 17-year-old drivers in fatal crashes in 2005 were transporting teenagers with no adults in the vehicle; 61% of teenage passenger deaths (1,222 in 2005) occurred in vehicles driven by other teenagers. Wider application of passenger restrictions is indicated. IMPACT ON INDUSTRY: Ways to make passenger restrictions more effective are needed, and other techniques for reducing this major problem need development and testing.  相似文献   
437.
70 beaches in Wales, UK, were investigated with regard to the quality of beach scenery using video panoramas. Beaches were given a score from zero to 20 by a panel of 24 coastal managers (National Park and Heritage Coast Wardens, etc.) and 42 final year Degree or Master of Science students specializing in environmental sciences. Mean scores of coastal managers ranged from 16.1 (Broadhaven, S. Pembrokeshire; 80%) to 3.8 (Prestatyn, North Wales; 19%), while scores of students ranged from 16.0 (Barafundle, S. Pembrokeshire; 80%) to 6.1 (Trecco Bay, Porthcawl; 31%). Wave height, number of people present on the beach and position on the final videotape did not have significant effects on mean scores generated by either group. With both groups a strong preference was observed for undeveloped beaches over those where anthropogenic structures were prominent (p=0.00), but beach commercialization level had an independent effect only on scores from the student group (p=0.02). Cloud cover at time of filming had a significant effect (p=0.00) on scoring, so a correction was applied for final score calculation and ranking. The findings contribute to management of coastal aesthetic resources by providing a quantitative evaluation scheme. It is proposed to use these scores for beach scenery/aesthetic quality in a novel, comprehensive beach rating system.  相似文献   
438.
Shore platform erosion is considered a driving mechanism for cliff recession on many rocky coasts and, in the vicinity of sea defence structures, a threat to their stability, yet the spatial pattern of platform erosion, as well as the rate of lowering, is poorly documented. Measurements based on techniques such as the micro-erosion metre or laser scanner, though highly accurate for short time scales and specific locations, are difficult to extrapolate in space and time. They also fail to record mesoscale changes such as block removal. This paper describes a technique to quantify spatial and temporal changes and presents first results.  相似文献   
439.
Potts DL  Scott RL  Cable JM  Huxman TE  Williams DG 《Ecology》2008,89(10):2900-2910
In semiarid ecosystems, physiography (landscape setting) may interact with woody-plant and soil microbe communities to constrain seasonal exchanges of material and energy at the ecosystem scale. In an upland and riparian shrubland, we examined the seasonally dynamic linkage between ecosystem CO2 exchange, woody-plant water status and photosynthesis, and soil respiration responses to summer rainfall. At each site, we compared tower-based measurements of net ecosystem CO2 exchange (NEE) with ecophysiological measurements among velvet mesquite (Prosopis velutina Woot.) in three size classes and soil respiration in sub-canopy and inter-canopy micro-sites. Monsoonal rainfall influenced a greater shift in the magnitude of ecosystem CO2 assimilation in the upland shrubland than in the riparian shrubland. Mesquite water status and photosynthetic gas exchange were closely linked to the onset of the North American monsoon in the upland shrubland. In contrast, the presence of shallow alluvial groundwater in the riparian shrubland caused larger size classes of mesquite to be physiologically insensitive to monsoonal rains. In both shrublands, soil respiration was greatest beneath mesquite canopies and was coupled to shallow soil moisture abundance. Physiography, through its constraint on the physiological sensitivity of deeply rooted woody plants, may interact with plant-mediated rates of soil respiration to affect the sensitivity of semiarid-ecosystem carbon exchange in response to episodic rainfall.  相似文献   
440.
Integrative research is increasingly a priority within the scientific community and is a central goal for the evolving field of sustainability science. While it is conceptually attractive, its successful implementation has been challenging and recent work suggests that the move towards interdisciplinarity and transdisciplinarity in sustainability science is being only partially realized. To address this from the perspective of social-ecological systems (SES) research, we examine the process of conducting a science of integration within the Southcentral Alaska Test Case (SCTC) of Alaska-EPSCoR as a test-bed for this approach. The SCTC is part of a large, 5 year, interdisciplinary study investigating changing environments and adaptations to those changes in Alaska. In this paper, we review progress toward a science of integration and present our efforts to confront the practical issues of applying proposed integration frameworks. We: (1) define our integration framework; (2) describe the collaborative processes, including the co-development of science through stakeholder engagement and partnerships; and (3) illustrate potential products of integrative, social-ecological systems research. The approaches we use can also be applied outside of this particular framework. We highlight challenges and propose improvements for integration in sustainability science by addressing the need for common frameworks and improved contextual understanding. These insights may be useful for capacity-building for interdisciplinary projects that address complex real-world social and environmental problems.  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