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   447篇
  免费   3篇
  国内免费   6篇
安全科学   20篇
废物处理   16篇
环保管理   39篇
综合类   63篇
基础理论   71篇
污染及防治   187篇
评价与监测   18篇
社会与环境   40篇
灾害及防治   2篇
  2023年   2篇
  2022年   5篇
  2021年   9篇
  2020年   8篇
  2019年   8篇
  2018年   12篇
  2017年   16篇
  2016年   14篇
  2015年   22篇
  2014年   12篇
  2013年   28篇
  2012年   26篇
  2011年   27篇
  2010年   19篇
  2009年   22篇
  2008年   25篇
  2007年   30篇
  2006年   23篇
  2005年   26篇
  2004年   15篇
  2003年   11篇
  2002年   5篇
  2001年   10篇
  2000年   4篇
  1999年   9篇
  1998年   4篇
  1997年   9篇
  1996年   3篇
  1995年   3篇
  1994年   4篇
  1993年   2篇
  1992年   3篇
  1990年   2篇
  1989年   3篇
  1988年   2篇
  1985年   2篇
  1984年   2篇
  1983年   3篇
  1982年   3篇
  1981年   6篇
  1980年   2篇
  1979年   2篇
  1977年   5篇
  1976年   4篇
  1970年   1篇
  1960年   1篇
  1956年   1篇
  1938年   1篇
排序方式: 共有456条查询结果,搜索用时 15 毫秒
121.
The personal assessments of the current and expected future state of the environment by 3232 community respondents in 18 nations were investigated at the local, national, and global spatial levels. These assessments were compared to a ranking of each country's environmental quality by an expert panel. Temporal pessimism (“things will get worse”) was found in the assessments at all three spatial levels. Spatial optimism bias (“things are better here than there”) was found in the assessments of current environmental conditions in 15 of 18 countries, but not in the assessments of the future. All countries except one exhibited temporal pessimism, but significant differences between them were common. Evaluations of current environmental conditions also differed by country. Citizens' assessments of current conditions, and the degree of comparative optimism, were strongly correlated with the expert panel's assessments of national environmental quality. Aside from the value of understanding global trends in environmental assessments, the results have important implications for environmental policy and risk management strategies.  相似文献   
122.
The ARGOS decision support system is currently being extended to enable estimation of the consequences of terror attacks involving chemical, biological, nuclear and radiological substances. This paper presents elements of the framework that will be applied in ARGOS to calculate the dose contributions from contaminants dispersed in the atmosphere after a ‘dirty bomb’ explosion. Conceptual methodologies are presented which describe the various dose components on the basis of knowledge of time-integrated contaminant air concentrations. Also the aerosolisation and atmospheric dispersion in a city of different types of conceivable contaminants from a ‘dirty bomb’ are discussed.  相似文献   
123.
Among the emerging literature addressing the biological effects of nanoparticles, very little information exists, particularly on aquatic organisms, that evaluates nanoparticles in comparison to non-nanocounterparts. Therefore, the potential effects of nano-scale and non-nano-scale TiO2 and ZnO on the water flea, Daphnia magna, were examined in 48-h acute toxicity tests using three different test media, several pigment formulations – including coated nanoparticles – and a variety of preparation steps. In addition, a 21-d chronic Daphnia reproduction study was performed using coated TiO2 nanoparticles. Analytical ultracentrifugation analyses provided evidence that the nanoparticles were present in a wide range of differently sized aggregates in the tested dispersions. While no pronounced effects on D. magna were observed for nano-scale and non-nano-scale TiO2 pigments in 19 of 25 acute (48-h) toxicity tests (EC50 > 100 mg L−1), six acute tests with both nano- and non-nano-scale TiO2 pigments showed slight effects (EC10, 0.5–91.2 mg L−1). For the nano-scale and non-nano-scale ZnO pigments, the acute 48-h EC50 values were close to the 1 mg L−1 level, which is within the reported range of zinc toxicity to Daphnia. In general, the toxicity in the acute tests was independent of particle size (non-nano-scale or nano-scale), coating of particles, aggregation of particles, the type of medium or the applied pre-treatment of the test dispersions. The chronic Daphnia test with coated TiO2 nanoparticles demonstrated that reproduction was a more sensitive endpoint than adult mortality. After 21 d, the NOEC for adult mortality was 30 mg L−1 and the NOEC for offspring production was 3 mg L−1. The 21-d EC10 and EC50 values for reproductive effects were 5 and 26.6 mg L−1, respectively. This study demonstrates the utility of evaluating nanoparticle effects relative to non-nano-scale counterparts and presents the first report of chronic exposure to TiO2 nanoparticles in D. magna.  相似文献   
124.
Numerical clustering has frequently been used to define hierarchically organized ecological regionalizations, but there has been little robust evaluation of their performance (i.e., the degree to which regions discriminate areas with similar ecological character). In this study we investigated the effect of the weighting and treatment of input variables on the performance of regionalizations defined by agglomerative clustering across a range of hierarchical levels. For this purpose, we developed three ecological regionalizations of Switzerland of increasing complexity using agglomerative clustering. Environmental data for our analysis were drawn from a 400 m grid and consisted of estimates of 11 environmental variables for each grid cell describing climate, topography and lithology. Regionalization 1 was defined from the environmental variables which were given equal weights. We used the same variables in Regionalization 2 but weighted and transformed them on the basis of a dissimilarity model that was fitted to land cover composition data derived for a random sample of cells from interpretation of aerial photographs. Regionalization 3 was a further two-stage development of Regionalization 2 where specific classifications, also weighted and transformed using dissimilarity models, were applied to 25 small scale “sub-domains” defined by Regionalization 2. Performance was assessed in terms of the discrimination of land cover composition for an independent set of sites using classification strength (CS), which measured the similarity of land cover composition within classes and the dissimilarity between classes. Regionalization 2 performed significantly better than Regionalization 1, but the largest gains in performance, compared to Regionalization 1, occurred at coarse hierarchical levels (i.e., CS did not increase significantly beyond the 25-region level). Regionalization 3 performed better than Regionalization 2 beyond the 25-region level and CS values continued to increase to the 95-region level. The results show that the performance of regionalizations defined by agglomerative clustering are sensitive to variable weighting and transformation. We conclude that large gains in performance can be achieved by training classifications using dissimilarity models. However, these gains are restricted to a narrow range of hierarchical levels because agglomerative clustering is unable to represent the variation in importance of variables at different spatial scales. We suggest that further advances in the numerical definition of hierarchically organized ecological regionalizations will be possible with techniques developed in the field of statistical modeling of the distribution of community composition.  相似文献   
125.
The Swedish System for Quality Assessment of Agricultural Soils   总被引:2,自引:0,他引:2  
Soil quality assessment is based on the concept of soilfunctions. The performances of three soil functions, cropproduction, biological decomposition and matter exchange withthe atmosphere and groundwater, are used as quality criteria.Soil properties that can be used as indicators for the degreeof functional performance were identified. Each soil propertyselected was graded into five classes – from best (class 1) toworst (class 5). Grading was based biological on boundaryconditions as well as on statistical distribution. The systemoutlined can be used to interpret the quality state ofagricultural soils, provides for a relative comparison betweensoils, and may be helpful in an environmental monitoringprogram to assess trends in data.  相似文献   
126.
Persistent organic pollutants (POPs) are chemicals that accumulate in the food chain and are toxic to humans and wildlife. The fourth World Health Organization (WHO) survey on POP levels in human milk (2006-2009) aims to provide baseline and trend information on human exposure to POPs. So far Belgium participated in all three previous rounds (1988, 1992, 2001). Whereas the first three rounds focused on determination of dioxins and PCBs in pooled (mixed) samples, the fourth survey comprised the analyses of individual milk samples for nine "basic POPs" (chlorinated pesticides and indicator PCBs) and of pooled milk samples for "basic POPs", "advanced POPs" (dioxins and dioxin-like PCBs) and "optional POPs" (polybrominated diphenylethers [PBDEs], polybrominated dioxins and dibenzofurans [PBrDD/F], mixed halogenated dioxins and dibenzofurans [PXDD/F] and hexabromocyclododecane [HBCD]). For the Belgian participation human milk samples were collected during the summer of 2006 from 197 women between 18 and 30 years old distributed over all Belgian provinces. The individual samples were analyzed in a Belgian Laboratory for "basic" POPs. A pooled sample was made from 178 individual samples and analyzed by the WHO Reference Laboratory for the "basic, advanced and optional" POPs. The results indicate that most organochlorinated pesticides banned 25-30 years ago were below or around detection limits in Belgian human milk samples although DDE was still found at low levels in all samples. Over the last five years the levels of marker PCBs and PCDD/Fs in Belgian human milk decreased, respectively, by 58% and 39%. For some of the other emerging or older compounds recent international data are needed to allow comparison. This shows the importance of international studies as run by WHO.  相似文献   
127.
The mechanistic bioaccumulation model OMEGA (Optimal Modeling for Ecotoxicological Applications) is used to estimate accumulation of zinc (Zn), copper (Cu), cadmium (Cd) and lead (Pb) in the earthworm Lumbricus rubellus. Our validation to field accumulation data shows that the model accurately predicts internal cadmium concentrations. In addition, our results show that internal metal concentrations in the earthworm are less than linearly (slope<1) related to the total concentration in soil, while risk assessment procedures often assume the biota-soil accumulation factor (BSAF) to be constant. Although predicted internal concentrations of all metals are generally within a factor 5 compared to field data, incorporation of regulation in the model is necessary to improve predictability of the essential metals such as zinc and copper.  相似文献   
128.
The purpose of the current study was to investigate spatial and seasonal variation of dioxin and dioxin-like PCB (dl-PCB) content in herring sampled along the northern Baltic Sea coast and map out risk zones for dioxins and dl-PCBs. We further aimed to investigate relationships between congener distribution (pattern) and sampling location and season. The results showed that there were distinct geographical differences in concentrations of dioxins, dibenzofurans and dl-PCBs along the Swedish coast, from the Bothnian Bay to north Baltic Proper, with the highest levels detected in the southern Bothnian Sea. The majority of the locations showed concentrations above the prescribed maximum for dioxin residues (4 TEQ pg g(-1) wet weight [w.w.]). If all the edible parts of the fish (muscle, subcutaneous fat and skin) are considered, the estimated concentrations exceeded the prescribed maximum level in the whole study area for herring collected during spring-summer. Concentrations in herring caught during spring-summer compared to concentrations in herring sampled in the autumn indicated seasonal variation. The pattern analysis showed a variation in relative congener concentration at the different sampling locations (spring-summer). Pattern differences were also noticed between seasons.  相似文献   
129.
Karlson K  Bonsdorff E  Rosenberg R 《Ambio》2007,36(2-3):161-167
This article focuses on the ecological role of benthic macrofauna on nutrient dynamics and benthic-pelagic coupling in the Baltic Sea with relation to eutrophication. Generally, benthic macrofaunal activities have large effects on sediment biogeochemistry and often with stimulatory effects on processes that counteract eutrophication, i.e., denitrification and increased phosphorus retention of the sediment. The degree of faunal impact on such processes varies depending on faunal density and functional group composition. The effect of macrofaunal activities on sediment nutrient dynamics can also result in a higher nitrogen: phosporus ratio of the sediments efflux compared with sediments without macrofauna. Increased internal nutrient loading during eutrophication-induced anoxia is suggested to be caused both by altered sediment biogeochemical processes and through reduced or lost bioturbating macrofauna and thereby a reduced stimulatory effect from their activities on natural purification processes of the Baltic Sea ecosystem.  相似文献   
130.
Controlling fugitive emissions from leaks in petrochemical industry process equipment now requires periodic monitoring of valves, flanges, pumps etc., typically on a quarterly basis. Previous studies have shown that over 90% of the reducible emissions come from approximately 0.1% of the components, i.e. the large leakers. A new, and more cost-effective approach for controlling these large leakers would entail more frequent monitoring of process equipment, allowing for the detection and repair of the highly leaking components that contribute the most to emissions. This approach has been called "Smart LDAR." New optical imaging instruments, which significantly reduce monitoring costs, are now available to implement such an alternative work practice. This work describes the determination of the leak detection sensitivity (equivalency threshold) that an optical imaging instrument must achieve to ensure that it will provide at least the equivalent emission control of the current leak detection and repair practice. Equivalency thresholds were developed for various monitoring intervals. The U.S. Environment Protection Agency's Monte Carlo simulation approach was used to perform the analysis and to demonstrate that optical imaging, which is capable of identifying all of the largest leakers, can provide better control of fugitive emissions.  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