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   3204篇
  免费   25篇
  国内免费   38篇
安全科学   90篇
废物处理   174篇
环保管理   305篇
综合类   527篇
基础理论   654篇
环境理论   2篇
污染及防治   990篇
评价与监测   295篇
社会与环境   202篇
灾害及防治   28篇
  2023年   29篇
  2022年   103篇
  2021年   135篇
  2020年   62篇
  2019年   57篇
  2018年   121篇
  2017年   127篇
  2016年   154篇
  2015年   90篇
  2014年   147篇
  2013年   222篇
  2012年   154篇
  2011年   195篇
  2010年   135篇
  2009年   127篇
  2008年   144篇
  2007年   139篇
  2006年   91篇
  2005年   129篇
  2004年   165篇
  2003年   158篇
  2002年   115篇
  2001年   78篇
  2000年   38篇
  1999年   35篇
  1998年   16篇
  1997年   26篇
  1996年   18篇
  1995年   24篇
  1994年   21篇
  1993年   10篇
  1992年   12篇
  1991年   16篇
  1990年   11篇
  1989年   12篇
  1988年   7篇
  1987年   10篇
  1986年   9篇
  1985年   10篇
  1984年   11篇
  1983年   11篇
  1982年   6篇
  1981年   8篇
  1979年   8篇
  1970年   3篇
  1966年   3篇
  1965年   3篇
  1964年   4篇
  1963年   3篇
  1961年   4篇
排序方式: 共有3267条查询结果,搜索用时 46 毫秒
991.
In early 2009, few would have expected that the Intergovernmental Panel on Climate Change (IPCC) would come under such massive attack. The IPCC had enjoyed a pristine reputation and had even advanced to become a role model for biodiversity and food security assessments (Loreau et al. 2006; Watson 2005). However, public trust and, with it, the organization’s credibility eroded dramatically after November 2009 with the events that became known as ‘climategate’. This article seeks to contribute to current debates about how to reform the IPCC. It argues that there are major flaws in the design of the IPCC which are rooted in the linear model of expertise and which are helping to stoke the backlash against the IPCC. The article analyzes the ways in which the IPCC’s activities conform to the linear model of expertise and considers the consequences of this for integrating adaptation into the IPCC assessments. It explains why adaptation played only a marginal role up until the IPCC Third Assessment Report. It then demonstrates why the use of the linear model of expertise constrains the scientific and political debate about adaptation and leads to proxy debates about scientific evidence, which result in depoliticizing the politics of adaptation and politicizing science. Finally, the article calls for the debate to be opened up to accommodate alternatives that are both politically more feasible and at the same time more appropriate to the specific needs of adaptation policies at different levels of decision-making.  相似文献   
992.
The aim of this paper is to disclose livelihood strategy-poverty links and gain a better understanding by developing typologies of rural households. Based on qualitative and quantitative data, we group households into different typologies and explore interactions. We identified six main agronomic strategies, four dominant livelihood diversification strategies, and income quartiles (proxies for poverty) using cluster and principal component factor analysis. We found that nearly 82% of the surveyed farmers in the study area belong to the bottom income quartiles while about 18% are on the upper quartiles. Households in the bottom income quartiles engaged in casual off-farm work and cereal-dominated livelihood strategies that tend to pursue subsistence farming by growing cereals and oil crops. Contrarily, farmers in the upper income quartiles adapted intensive agronomic strategies by integrating root crops, legumes, and vegetables with livestock. This was largely attributed to access to key livelihood assets such as land, livestock, education, and institutional support in which the upper quartiles were more endowed. Improving availability of the key assets for the bottom income quartiles might be a way out of poverty and ensuring sustainable development. It is crucial to recognize local-level heterogeneities of rural households when targeting development interventions.  相似文献   
993.
Differentiation of nitrous oxide emission factors for agricultural soils   总被引:3,自引:0,他引:3  
Nitrous oxide (N2O) direct soil emissions from agriculture are often estimated using the default IPCC emission factor (EF) of 1%. However, a large variation in EFs exists due to differences in environment, crops and management. We developed an approach to determine N2O EFs that depend on N-input sources and environmental factors. The starting point of the method was a monitoring study in which an EF of 1% was found. The conditions of this experiment were set as the reference from which the effects of 16 sources of N input, three soil types, two land-use types and annual precipitation on the N2O EF were estimated. The derived EF inference scheme performed on average better than the default IPCC EF. The use of differentiated EFs, including different regional conditions, allows accounting for the effects of more mitigation measures and offers European countries a possibility to use a Tier 2 approach.  相似文献   
994.
995.
To assess transport and ecotoxicological risks of metals, such as cadmium (Cd) in soils, models are needed for partitioning and speciation. We derived regression-based “partition-relations” based on adsorption and desorption experiments for main Australian soil types. First, batch adsorption experiments were carried out over a realistic range of dissolved Cd concentrations in agricultural soils in Australia. Results showed linear sorption relationships, implying the adequacy of using Kd values to describe partitioning. Desorption measurements were then carried out to assess in-situ Kd values and relate these to soil properties The best transfer functions for solid-solution partitioning were found for Kd values relating total dissolved Cd concentration to total soil Cd concentrations, accounting for the variation in pH, SOM contents and DOC concentrations. Model predictions compared well with measurements of an independent data set, but there was a tendency to underestimate dissolved Cd concentrations of highly polluted soils.  相似文献   
996.
997.

Background, aims, and scope

Formaldehyde (FA) is a harmful chemical, which is classified as carcinogenic to humans (Group 1) by the International Agency for Research on Cancer. Solutions of FA that are used to preserve cadavers in research and education morphological institutes represent a risk to occupational health of professionals and students. During the dissection of cadavers in the anatomy laboratories, FA vapors are emitted, resulting in the exposure of students and their instructors to elevated levels of FA. The World Health Organization recommends an air quality guideline value of 0.1 mg m?3 for exposure to FA. The limit of occupational exposure adopted by the Brazilian legislation (2.3 mg m?3) is markedly higher than those adopted by institutions of other countries around the world. The purpose of this study was to determine the levels of personal exposure and the area concentration of FA in the morphology department of the Federal Fluminense University, Brazil, and investigate and compare the relationship between them.

Methods

Four rooms distributed in the three floors of the Morphology Department were evaluated: the embalming laboratory, the anatomy laboratories, the corridor of the teachers?? rooms, and the entrance hall. Thirty-six samples in total were collected in the second semester of 2010 and first semester of 2011. The air sampling and FA analysis were performed according to the EPA TO-11A Protocol, using a diffusive sampling device for carbonyl compounds. Personal samples were collected from monitors using a sampling device pinned on each person??s lapel. The samples were analyzed using rapid resolution liquid chromatography with UV-DAD detection at 360 nm.

Results and discussion

The concentrations of FA ranged from 0.20 and 0.18 mg m?3 in the corridor between the teachers?? rooms, 0.03 to 0.37 mg m?3 in the entrance hall, 0.22 to 2.07 mg m?3 in the anatomy laboratory, 2.21 to 2.52 mg m?3, in the embalming room. The levels found in the corridor between the teachers?? rooms and in the entrance hall were lower than in other compartments because of their large distances to the sources of FA and better ventilation. The other rooms presented higher levels of FA because of the activities carried there (embalming and dissection procedures). Even in the rooms that showed the lowest levels of FA, the values found were higher than those established by all international guideline limits, except the Brazilian legislation limit, although, the concentration level in the embalming room was even greater than the Brazilian guideline. These concentrations are 100?C1,000-fold higher than those reported in an FA outdoor study. The exposure levels of monitors and students ranged from 1.89 to 4.82 mg m?3, indicating that current practices at the Morphology Department at the university would represent a health risk. The simultaneous monitoring of area concentrations and personal exposure showed that the characteristics of classes and of cadavers?? parts, the number of students in the room and even the activities of the monitors influence the FA concentrations.

Conclusion

This study revealed that the concentration of FA was low in the ventilated areas of the Morphology Department, and that the personal exposure when the person was close to the cadavers during the dissection procedure was higher than the mean FA concentration. This should be considered in the risk assessment of FA during these activities without effective protection equipment. It is suggested that the Brazilian legislation of exposure to formaldehyde requires an urgent update considering international legislation.  相似文献   
998.

Background and scope  

Effect-directed analysis is increasingly used for the identification of key toxicants in environmental samples and there is a growing need for in vivo biotests as diagnostic tools. Within this study, we performed an in vivo sediment contact test, applicable on both native field samples and their extracts or fractions, in order to be able to compare the results from both field and laboratory studies.  相似文献   
999.

Purpose

To assess groundwater exposure to pesticides, in agricultural areas of ??Ribatejo?? region (Portugal), and the influence of some key factors in that exposure, field, laboratory and modelling studies were carried out.

Methods

The study was performed in maize, potato, sugar beet, tomato and vegetables agricultural areas, located in a shallow aquifer, with pesticides use and, in most cases, with irrigation practices. Pesticides used in the studied agricultural areas and having leaching potential were selected, being considered also other pesticides included in priority lists, defined in Europe. Evaluation of groundwater exposure to pesticides was carried out by successively: (1) groundwater sampling in seven campaigns over the period 2004?C2006; (2) pesticide analysis [including isolation and concentration from the groundwater samples and further determination by gas chromatography?Cmass spectrometry (GC?CMS) of 14 herbicides, four insecticides and two metabolites]; and (3) analysis and discussion of the results by applying joint correspondence analysis (JCA).

Results

From the 20 pesticides and metabolites selected for the study, 11 were found in groundwater. Pesticides and metabolites most frequently detected were atrazine, alachlor, metolachlor, desethylatrazine, ethofumesate, ??-endosulfan, metribuzine, lindane and ??-endosulfan. The results showed that groundwater exposure to pesticides is influenced by local factors??either environmental or agricultural, as precipitation, soil, geology, crops and irrigation practices. Spring and autumn were more associated with the detection of pesticides being more likely to observe mixtures of these compounds in a groundwater sample in these transition seasons.

Conclusions

This work evidences the importance of models, which evaluate pesticides environmental behaviour, namely their water contamination potential (as Mackay multicompartimental fugacity model) and, specially, groundwater contamination potential (as GUS and Bacci and Gaggi leaching indices), in pesticide selection. Moreover, it reveals the importance to adapt proper statistical methods according to level of left-censored data. Using JCA was still possible to establish relations between pesticides and their temporal trend in a case study where there were more than 80% of data censored. This study will contribute to the Tagus river basin management plan with information on the patterns of pesticide occurrence in the alluvial aquifer system.  相似文献   
1000.
The bioaccumulation of perfluorooctanesulfonamide (PFOSA) and two fluorotelomer alcohols (8:2 FTOH, 10:2 FTOH) by rainbow trout (Oncorhynchus mykiss) through dietary exposure, including depuration rates and metabolism was investigated. Concentrations in the spiked feed ranged from 10.9 μg g−1 wet weight (wet wt) for PFOSA and 6.7 μg g−1 wet wt for 8:2 FTOH to 5.0 μg g−1 wet wt for 10:2 FTOH. Trout was fed at 1.5% body weight per day for 30 d and depuration was followed for up to 30 d following previously published dietary exposure protocols. Perfluorooctanesulfonate (PFOS) was the major perfluoroalkylsulfonate (PFSA) detected in fish following dietary exposure to PFOSA. Half-lives of PFOS and PFOSA were 16.9 ± 2.5 and 6.0 ± 0.4 d, respectively. A biomagnification factor (BMF) of 0.023 was calculated for PFOSA which indicates that dietary exposure to PFOSA does not result in biomagnification in the rainbow trout. PFOS had a BMF of 0.08. The fluorotelomer saturated acids (8:2 FTCA, 10:2 FTCA) and fluorotelomer unsaturated acids (8:2 FTUCA, 10:2 FTUCA) were the major products detected in rainbow trout following dietary exposure to 8:2 FTOH and 10:2 FTOH, respectively. Half-lives were 3.7 ± 0.4, 2.1 ± 0.5, 3.3, and 1.3 d for 10:2 FTCA, 10:2 FTUCA, 8:2 FTCA, and 8:2 FTUCA, respectively. Small amounts of perfluorooctanoate (PFOA) and perfluorodecanoate (PFDA) were also detected in the FTOH exposed fish.  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