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   282篇
  免费   8篇
  国内免费   7篇
安全科学   23篇
废物处理   13篇
环保管理   69篇
综合类   24篇
基础理论   57篇
污染及防治   55篇
评价与监测   40篇
社会与环境   14篇
灾害及防治   2篇
  2023年   1篇
  2022年   1篇
  2021年   4篇
  2020年   2篇
  2019年   3篇
  2018年   8篇
  2017年   5篇
  2016年   20篇
  2015年   7篇
  2014年   9篇
  2013年   24篇
  2012年   9篇
  2011年   16篇
  2010年   14篇
  2009年   20篇
  2008年   15篇
  2007年   19篇
  2006年   11篇
  2005年   13篇
  2004年   24篇
  2003年   21篇
  2002年   8篇
  2001年   9篇
  2000年   3篇
  1999年   1篇
  1998年   2篇
  1997年   2篇
  1996年   2篇
  1995年   5篇
  1994年   2篇
  1993年   1篇
  1992年   1篇
  1991年   3篇
  1990年   1篇
  1989年   3篇
  1988年   2篇
  1986年   2篇
  1982年   1篇
  1981年   1篇
  1977年   2篇
排序方式: 共有297条查询结果,搜索用时 15 毫秒
111.
Household waste prevention in England has been recognised in national strategy as a key component for future sustainable practice. To support the policy agenda, the Department of Environment, Food and Rural Affairs (Defra) in England has funded an extensive programme of fundamental research in the area. The specific research aim reported on here, in this Defra funded project, was to trial and assess methods for monitoring and evaluating approaches detailed in the National Resource and Waste Forum (NRWF)’s Household Waste Prevention Toolkit. The methods that formed the basis for the four research Objectives for the project were: using pilot and control areas (core Objective), tracking waste arisings, measuring specific activities and declared awareness and behaviour surveys. A primary objective of this research was to quantify the direct waste tonnage impacts of implementing a targeted household waste campaign in Dorset County, UK. A key performance indicator chosen for this assessment was the weight of waste collected at the kerbside from households. In an area where a waste prevention campaign is well planned and implemented then reductions in household waste arisings in pilot areas can be in the region of 2% per annum. This method for monitoring can be used, in the hands of an expert project team, to communicate to the public the direct benefits of waste prevention. It was found that there are a wide range of factors that need to be taken into account in the UK, and that these had hitherto been given little prominence, such as careful matching of pilot and control areas – this proved problematical in this research. However, a range of techniques used to support the methods, e.g. doorstepping surveys and focus groups could not show clear attributable waste prevention impacts but their findings could be used to direct new future messages to the public. The most successful and measurable campaign activities that were revealed by evaluation were: mail preference registrations, Home composting and doorstepping. An expert evaluation of all major methods found that no clear preference was revealed as to which were the most useful. None of the methods were judged very poor neither very good, all had major issues about their use. Tracking waste arisings and focus groups were assessed to be the best techniques in terms of input effort to output value. It is likely that waste prevention teams for household waste will need very careful training in the cost-effective use of the NRWF Toolkit before they are competent to apply it to a given place; the issues are more complex than were first thought.  相似文献   
112.
The use of leaded gasoline in automobiles equipped with catalytic converters causes deactivation of the converters and leads to significant increases in emissions of reactive hydrocarbons, a precursor of ozone. Such fuel switching may be a contributing factor to the increase in photochemical smog levels recently observed in the South Coast Air Basin (SOCAB).  相似文献   
113.
Human alteration of the landscape has an extensive influence on the biogeochemical processes that drive oxygen cycling in streams. We estimated trends from the mid-1990s to 2003, using the seasonal Mann-Kendall's test, for percent saturation dissolved oxygen (DO), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), and ammonia-nitrogen (NH(3)-N) for 12 sites in the Rock Creek watershed, northwest Oregon, USA. In order to understand the influence of landscape change, scale, and stormwater runoff management on dissolved oxygen trends, we calculated land cover change through aerial photo interpretation at full-basin, local (near sample point) basin, and 100m stream buffer scales, for the years 1994 and 2000. Significant (p < or = 0.05) trends occurred in DO (increasing at five sites), COD (decreasing at seven sites), TKN (decreasing at five sites, increasing at one site), and NH(3)-N (decreasing at one site, increasing at one site). Significant land cover change occurred in agricultural land cover (-8% for the entire basin area) and residential land cover (+10% for the entire basin area) (p < or = 0.05). Correlation results indicated that: (1) forest cover negatively influenced COD at the full basin scale and positively influences NH(3)-N at local scales, (2) residential land cover influenced oxygen demand variables at local scales, (3) agricultural land cover did not influence oxygen demand, (4) local topography negatively influenced TKN and NH(3)-N, and (5) stormwater runoff management infrastructure correlated positively with COD at the local scale. This study indicates that landscape factors influencing DO conditions for the study streams act at multiple scales, suggesting that better knowledge of scale-process interactions can guide watershed managers' decision making in order to maintain improving water quality conditions.  相似文献   
114.
The paper presents a framework for the analysis of external costs of environmental burdens, namely an impact pathway analysis, often coupled with the inventory stage of life cycle assessment (LCA). The ground rule is: quantify as much as possible in terms of burdens (pollutant emissions, etc.), impacts, and their monetary equivalent, then use multi-criteria analysis (MCA) for any remaining impacts that are considered to be too uncertain or defy quantification through to monetization. Although MCA could be used directly on estimates of burdens or impacts, monetary valuation provides a mechanism for consistent weighting of impacts categories based on assessment of public preference. Further advantages of extending LCA through detailed impact assessment combined with monetary valuation are that it greatly simplifies MCA by combining a large number of different environmental impact categories, thereby avoiding an unmanageably large number of criteria, and also facilitates cost benefit analysis (CBA). The risks are noted of inappropriate use of the tools or interpretation/use of the results, and recommendations are made for improved practice. These points are illustrated with examples. The key messages are: (1) that policies should be targeted correctly to give a clear signal which source of a burden should be reduced by how much; (2) that analysts should take into account the needs of policy makers and the link between the analysis and possible policy applications; and (3) that current LCA practice gives limited guidance in both areas, largely through a lack of consideration of the relative and absolute importance of different types of impact. However, this is precisely the strength of external costs analysis, particularly when used with MCA.  相似文献   
115.
2002 has been a landmark year for children's environmental health, with several major international conferences dedicated to the issue and the publication of numerous reports and studies. In this article we review how and why children's health has emerged as a key environmental policy issue and what the analytical sciences can contribute.  相似文献   
116.
117.
The requirements of the Texas State Implementation Plan of the U.S. Clean Air Act for the Houston-Galveston Ozone Nonattainment Area stipulate large reductions in oxides of nitrogen (NO(x)) emissions. A large number of sources at Dow Chemical Co. sites within the nonattainment area may require the addition of continuous emission monitoring systems (CEMS) for online analysis of NO(x), CO, and O2. At the outset of this work, it was not known whether the analyzers could accurately measure NO(x) as low as 2 ppm. Therefore, NO(x) CEMS analyzers from five different companies were evaluated for their ability to reliably measure NO(x) in the 2-20 ppm range. Testing was performed with a laboratory apparatus that accurately simulated different mixtures of flue gas and, on a limited basis, simulated a dual-train sampling system on a gas turbine. The results indicate that this method is a reasonable approach for analyzer testing and reveal important technical performance aspects for accurate NO(x) measurements. Several commercial analyzers, if installed in a CEMS application with sampling conditioning components similar to those used in this study, can meet the U.S. Environmental Protection Agency's measurement data quality requirements for accuracy.  相似文献   
118.
A reconnaissance soil geochemical and concomitant plant survey based on 318 soil (0-15 cm) and 122 plant samples was used for the assessment of heavy metal pollution of agricultural soils and crops of Thailand. Arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) were determined in soils using aqua regia digestion, and in plants using nitric acid digestion. Organic carbon (C), pH, electrical conductivity (EC) and available phosphorus (P) were determined on the soil samples using appropriate procedures. Results indicated that concentrations of heavy metals varied widely among the different regions of Thailand. Regression analysis between the concentrations of metals in soil (aqua regia extractable) and edible plant parts indicated a small but positive relationship for Cd in all the plants sampled in the survey (R2 = 0.081, p < 0.001). There was also a positive relationship between soil and plant Cd concentrations in rice (R2 = 0.242, p < 0.010), and negative relationships for Zn in rice (R2 = 0.385, p < 0.001), and Cu (R2 = 0.355, p < 0.001) and Zn (R2 = 0.122, p < 0.026) in glutinous rice. Principal component analysis of the soil data suggested that concentrations of As, Co, Cr, Cu, Hg, Ni and Pb were strongly correlated with concentrations of Al and Fe, which is suggestive of evidence of background variations due to changes in soil mineralogy. Thus, the evidence for widespread contamination of soils by these elements through agricultural activities is not strong. On the other hand, Cd and Zn were strongly correlated with organic matter and concentrations of available and aqua regia extractable P. This is attributed to input of contaminants in agricultural fertilisers and soil amendments (e.g. manures, composts).  相似文献   
119.
ABSTRACT: The planning and developing of water resources to meet the country's needs for water supply, flood control, hydroelectric power, irrigation, and navigation now needs to take more account of environmental needs and regulations. Water resource development is often beneficial to the environment, but may also be harmful, as in cases involving salmon and various other endangered species. As a national objective, the environment must be preserved and in some cases restored; but how can this be done consistent with other national objectives, relating to life and welfare of human beings? This problem has aroused the concern of many engineers and water scientists. As a result, a national conference on this subject was held in Chicago in June 1998, as an integral part of ASCE's Annual Conference on Water Resources Planning and Management and the Annual Conference on Environmental Engineering. At the conclusion of that conference, a post-conference meeting was held by a group of prominent water resource practitioners. It was concluded at this meeting that action should be taken by our government to establish a new form of interagency approach, involving the states, as a means of coordination in cases of national importance.  相似文献   
120.
ABSTRACT: We surveyed first‐to third‐order streams (channel widths from 1.4 to 10 m) in the southeastern slopes of the Cascade Range of Washington and found two distinct endpoints of riparian vegetation. Where the forest overstory is dominated by park‐like Ponderosa pine (Pinus ponderosa), channels are commonly bordered with a dense scrub‐shrub vegetation community. Where fire suppression and/or lack of active riparian zone management have resulted in dense encroachment of fir forests that create closed forest canopies over the channel, scrub‐shrub vegetation communities are virtually absent near the channel. Other factors being equal, distinct differences in channel morphology exist in streams flowing thru each riparian community. The scrub‐shrub channels have more box‐like cross‐sections, lower width‐to‐depth ratios, more pools, more undercut banks, more common sand‐dominated substrates, and similar amounts of woody debris (despite lower tree density). Temperature comparisons of forest and scrub‐shrub sections of two streams indicate that summer water temperatures are slightly lower in the scrub‐shrub streams. We surmise that these morphology and temperature effects are driven by differences in root density and canopy conditions that alter dynamic channel processes between each riparian community. We suspect that the scrub‐shrub community was more common in the landscape prior to the 20th century and may have been the dominant native riparian community for these stream types. We therefore suggest that managing these streams for dense riparian conifer does not mimic natural conditions, nor does it provide superior in‐stream habitat.  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