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   8969篇
  免费   31篇
  国内免费   398篇
安全科学   374篇
废物处理   415篇
环保管理   920篇
综合类   1144篇
基础理论   578篇
环境理论   1篇
污染及防治   4033篇
评价与监测   1206篇
社会与环境   631篇
灾害及防治   96篇
  2024年   7篇
  2023年   23篇
  2022年   23篇
  2021年   20篇
  2020年   22篇
  2019年   26篇
  2018年   25篇
  2017年   23篇
  2016年   14篇
  2015年   39篇
  2014年   45篇
  2013年   41篇
  2012年   836篇
  2011年   1122篇
  2010年   149篇
  2009年   279篇
  2008年   1055篇
  2007年   978篇
  2006年   809篇
  2005年   674篇
  2004年   621篇
  2003年   572篇
  2002年   486篇
  2001年   378篇
  2000年   245篇
  1999年   116篇
  1998年   39篇
  1997年   50篇
  1996年   55篇
  1995年   50篇
  1994年   44篇
  1993年   38篇
  1992年   51篇
  1991年   39篇
  1990年   52篇
  1989年   37篇
  1988年   37篇
  1987年   58篇
  1986年   17篇
  1985年   34篇
  1984年   27篇
  1983年   28篇
  1982年   20篇
  1981年   35篇
  1980年   27篇
  1979年   9篇
  1978年   8篇
  1976年   4篇
  1975年   6篇
  1974年   4篇
排序方式: 共有9398条查询结果,搜索用时 15 毫秒
971.
Laser-ablation inductively coupled-plasma mass-spectrometry analysis of red oak (Quercus rubra) from a well documented heavy metal contaminated United States Environmental Protection Agency superfund site in Woburn, Massachusetts reveals decade-long trends in Pb contaminant sources. Lead isotope ratios (207Pb/206Pb and 208Pb/206Pb) in tree rings plot along a linear trend bracketed by several local and regional contamination sources. Statistically significant interannual variations in 207Pb/206Pb suggest that atmospheric Pb is rapidly incorporated into wood, with minimal mobility subsequent to deposition in annual growth rings. We interpret the decadal trends in our record as a changing mixture of local pollution sources and gasoline-derived Pb. Between 1940 and 1970, Pb was predominantly derived from remobilization of local industrial Pb sources. An abrupt shift in 207Pb/206Pb may indicate that local Pb sources were overwhelmed by gasoline-derived Pb during the peak of leaded gasoline emissions in the late 1960s and early 1970s.  相似文献   
972.
In this study treatment of palm oil mill effluent (POME) was investigated using aerobic oxidation based on an activated sludge process. The effects of sludge volume index, scum index and mixed liquor suspended solids during the acclimatizing phase and biomass build-up phase were investigated in order to ascertain the reactor stability. The efficiency of the activated sludge process was evaluated by treating anaerobically digested and diluted raw POME obtained from Golden Hope Plantations, Malaysia. The treatment of POME was carried out at a fixed biomass concentration of 3900+/-200mg/L, whereas the corresponding sludge volume index was found to be around 105+/-5mL/g. The initial studies on the efficiency of the activated sludge reactor were carried out using diluted raw POME for varying the hydraulic retention time, viz: 18, 24, 30 and 36h and influent COD concentration, viz: 1000, 2000, 3000, 4000 and 5000mg/L, respectively. The results showed that at the end of 36h of hydraulic retention time for the above said influent COD, the COD removal efficiencies were found to be 83%, 72%, 64%, 54% and 42% whereas at 24h hydraulic retention time they were 57%, 45%, 38%, 30% and 27%, respectively. The effectiveness of aerobic oxidation was also compared between anaerobically digested and diluted raw POME having corresponding CODs of 3908 and 3925mg/L, for varying hydraulic retention time, viz: 18, 24, 30, 36, 42, 48, 54 and 60h. The dissolved oxygen concentration and pH in the activated sludge reactor were found to be 1.8-2.2mg/L and 7-8.5, respectively. The scum index was found to rise from 0.5% to 1.9% during the acclimatizing phase and biomass build-up phase.  相似文献   
973.
The Environmental Management System (EMS) is commonly implemented in private firms. However, on the basis of a strengths, weaknesses, opportunities and threats (SWOT) analysis, our work analyzes the consequences of implementing an EMS within the context of local public administrations, particularly regarding the City Council of Ohanes in Almería (Spain). This is the first European corporation to implement an EMS according to the ISO 14001 Standard, certified by the Spanish Association of Normalization and Certification. Its analysis would be equivalent to the Shumpeterian "market innovator study", so that public administration "followers" can take advantage of the derived benefits and of minimizing the negative effects of such an experience. On the other hand, we show that the economic and environmental advantages derived from the EMS go beyond the activities that the City Council is in charge of. They have spillover effects that extend them to all economic activities in the municipality and these effects are expected to be increased in the medium and long-term perspective. In this paper, we compare the costs and benefits that the municipality obtains in two cases: the City Council implements the EMS or it does not implement it. The main objective of this article is to show the economic and environmental advantages obtained by a municipality when it is only the City Council who is implementing an EMS. It is logical to suppose that this case study can stimulate other municipalities to use this instrument, even if the economic and environmental characteristics of the municipality are different.  相似文献   
974.
Sediments of five Ligurian beaches in compliance with European Union bathing water regulations were studied based on the characteristics of the fungal assemblage during the tourism season. Among the 179 taxa of filamentous fungi isolated, 120 were opportunistic pathogens, such as Acremonium sp., and the genus Penicillium was also present as the pathogenic species P. citrinum. Furthermore, 5% of the total filamentous fungi belonged to the dermatophyte genus Microsporum, whose species can cause mycoses. Beach sediments showed elevated densities of opportunistic pathogens, of pathogenic filamentous fungi, and of yeasts during the tourism season. Although monitoring of beach sediments for microbiological contamination is not mandatory, and disease transmission from sediments has not yet been demonstrated, our study suggests that beach sediments may act as a reservoir of potential pathogens, including fungi. In addition, the mycoflora displayed high sensitivity to critical environmental situations in the beaches studied. Therefore, the fungal community can be a useful tool for assessing the quality of sandy beaches in terms of sanitary and environmental quality.  相似文献   
975.
Although the use of kerbside recycling facilities by householders is often key to the reduction of materials disposed of to landfill, the quantitative assessment of householders' recycling behaviour is problematic. This study introduces a method to diagnose recycling behaviour by assessing kerbside scheme use in terms of the set-out of recyclate containers compared to the proportion of households participating in recycling (participation ratio). Application of numerical behaviour models demonstrated that kerbside recycling in sampled regions of the UK tends to be consistent with householders using kerbside schemes more frequently than would be observed with random patterns of use that are uniform amongst all householders. When aggregated to collection rounds, householders' modal recycling behaviour tended towards either non-participation or frequent participation. We propose that initiatives to enhance kerbside recycling should employ such quantitative assessments of recycling behavioural modes to inform and guide promotional and educational strategies. A conceptual model for prioritizing campaigns to promote recycling at the kerbside on the basis of identifiable and quantifiable patterns of householder recycling behaviour is presented.  相似文献   
976.
Landscapes fulfil a multitude of ecological and social functions. Due to the fact that both traditional and everyday landscapes today face many different threats, regulatory measures have been undertaken in many countries to protect and further sustainable landscape development. They include legislation as well as economic incentives. In recent years, however, it has become clear that just to have a few laws and to spend money on subsidies is not enough. Factors other than legislation are also essential to further the sustainable development of landscapes. One of the basic factors affecting the success or failure of landscape conservation measures is public acceptance of these measures. Our project took this as its starting point. The objective was to determine which conditions and factors influence acceptance positively or negatively. To this end 22 Swiss who are directly affected by nature conservation measures, in particular by mire landscape and dry meadow conservation measures, were interviewed using qualitative interview techniques. It is shown that perception, communication, and possibilities to participate are the most decisive driving factors influencing the formation of a long-lasting acceptance. Furthermore, acceptance may be based mainly on economic criteria, on usefulness, on ecological or even aesthetic aspects. It can be shown that not all of these motivations lead to a long-lasting acceptance. Ecologically based acceptance seems the most promising because it is founded on general convictions. Economic incentives--though important--seem to generate only superficial acceptance and do not seem to be as important as is usually assumed.  相似文献   
977.
Plant invasions are a serious threat to natural and semi-natural ecosystems worldwide. Most management-orientated research on invasions focuses on invaders that are already widespread and often have major impacts. This paper deals with "emerging" invaders-those alien species with the potential to become important problems without timely intervention. A climate matching procedure was developed to define areas of South Africa, Lesotho and Swaziland that could be invaded by 28 plant species that had previously been classified as emerging invaders. Information on the location of populations of these species in the study area was combined with information on their distributions (as native or alien) in parts of Australia and the United States of America. These two countries had the best available distribution data for this study. They also share many invasive alien plant species with South Africa. Climatic data obtained for weather stations near points of known occurrence in these countries were used to define the climatically suitable areas for each species in the study area. Almost 80% of the remaining natural environment in southern Africa was found to be vulnerable to invasion by at least one of these species, 50% by six or more and 24% by 16 or more species. The most vulnerable areas are the highveld grasslands and the eastern escarpment. The emerging invaders with the greatest potential range included Acacia podalyriifolia and Cortaderia selloana. The globally important invaders Ulex europaeus and Lythrum salicaria had a more limited invasion potential but could still become major invaders. There was no relationship between the extent of the climatically suitable areas for the different species and an expert ranking of their invasion potential, emphasising the uncertainties inherent in making expert assessments based on very little information. The methods used in this analysis establish a protocol for future modelling exercises to assess the invasion potential of other emerging invaders.  相似文献   
978.
Multicriteria decision analysis (MCDA) provides a well-established family of decision tools to aid stakeholder groups in arriving at collective decisions. MCDA can also function as a framework for the social learning process, serving as an educational aid in decision problems characterized by a high level of public participation. In this paper, the framework and results of a structured decision process using the outranking MCDA methodology preference ranking organization method of enrichment evaluation (PROMETHEE) are presented. PROMETHEE is used to frame multi-stakeholder discussions of river management alternatives for the Upper White River of Central Vermont, in the northeastern United States. Stakeholders met over 10 months to create a shared vision of an ideal river and its services to communities, develop a list of criteria by which to evaluate river management alternatives, and elicit preferences to rank and compare individual and group preferences. The MCDA procedure helped to frame a group process that made stakeholder preferences explicit and substantive discussions about long-term river management possible.  相似文献   
979.
Spatial scaling between leaf area index maps of different resolutions   总被引:1,自引:0,他引:1  
We developed algorithms for spatial scaling of leaf area index (LAI) using sub-pixel information. The study area is located near Liping County, Guizhou Province, in China. Methods for LAI spatial scaling were investigated on LAI images with 960 m resolution derived in two ways. LAI from distributed calculation (LAID) was derived using Landsat ETM+ data (30 m), and LAI from lumped calculation (LAIL) was obtained from the coarse (960 m) resolution data derived through resampling the ETM+ data. We found that lumped calculations can be considerably biased compared to the distributed (ETM+) case, suggesting that global and regional LAI maps can be biased if surface heterogeneity within the mapping resolution is ignored. Based on these results, we developed algorithms for removing the biases in lumped LAI maps using sub-pixel land cover-type information, and applied these to correct one coarse resolution LAI product which greatly improved its accuracy.  相似文献   
980.
This paper develops a technique which can be used as a preliminary tool for assessing air quality related to urban traffic. It combines a Geographic Information System (GIS) with an interaction matrix-type methodology based on a system analysis approach. The matrix identifies and quantifies interactions between all selected variables involved in a system as well as their interaction with the system as a whole. This matrix is used to determine the weightings to apply to spatial datasets within a GIS to develop a pollution vulnerability map. The focus of the paper is to introduce and assess a more versatile coding of the interaction matrix with respect to previously used coding. A case study is presented in which the modified interaction methodology is applied to data for a busy urban location. The resulting vulnerability map, in terms of pollution vulnerable hot spots, was compared to a pollution map derived from an advanced dispersion model. The interaction matrix technique with GIS can be used as a tool complementary to sophisticated numerical modelling and has potential as an analytical tool to evaluate multidisciplinary systems.  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