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   536篇
  免费   10篇
  国内免费   4篇
安全科学   28篇
废物处理   26篇
环保管理   66篇
综合类   47篇
基础理论   131篇
污染及防治   167篇
评价与监测   44篇
社会与环境   31篇
灾害及防治   10篇
  2023年   6篇
  2022年   12篇
  2021年   13篇
  2020年   8篇
  2019年   10篇
  2018年   12篇
  2017年   16篇
  2016年   17篇
  2015年   15篇
  2014年   16篇
  2013年   48篇
  2012年   25篇
  2011年   43篇
  2010年   29篇
  2009年   30篇
  2008年   30篇
  2007年   35篇
  2006年   34篇
  2005年   34篇
  2004年   19篇
  2003年   14篇
  2002年   19篇
  2001年   4篇
  2000年   5篇
  1999年   6篇
  1998年   4篇
  1997年   6篇
  1996年   4篇
  1995年   6篇
  1994年   7篇
  1993年   3篇
  1992年   4篇
  1991年   2篇
  1990年   3篇
  1989年   1篇
  1985年   2篇
  1983年   1篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1974年   1篇
  1964年   1篇
排序方式: 共有550条查询结果,搜索用时 31 毫秒
511.
Over the past few decades, four distinct and largely independent research and policy communities--disaster risk reduction, climate change adaptation, environmental management and poverty reduction--have been actively engaged in reducing socio-economic vulnerability to natural hazards. However, despite the significant efforts of these communities, the vulnerability of many individuals and communities to natural hazards continues to increase considerably. In particular, it is hydro-meteorological hazards that affect an increasing number of people and cause increasingly large economic losses. Arising from the realisation that these four communities have been largely working in isolation and enjoyed only limited success in reducing vulnerability, there is an emerging perceived need to strengthen significantly collaboration and to facilitate learning and information exchange between them. This article examines key communalities and differences between the climate change adaptation and disaster risk reduction communities, and proposes three exercises that would help to structure a multi-community dialogue and learning process.  相似文献   
512.
At the new Marais des Cygnes National Wildlife Refuge in Linn County, Kansas, and Bates County, Missouri, USA, we evaluated long-lived contaminants before acquisition of the land for the refuge. We sampled sediments at 16 locations and fish at seven locations. The samples were analyzed for metals and for chlorinated hydrocarbon compounds. Selected sediment samples also were analyzed for aliphatic hydrocarbons. Arsenic concentrations in sediment samples from six locations were elevated compared to US norms, but arsenic was not detected in any fish composite. Mercury concentrations in largemouth bass from two locations were comparable to the 85th percentile concentrations in nationwide fish collections. Most sediment concentrations of other metals were unlikely to have detrimental effects on biota. No chlorinated hydrocarbons were detected in any sediment sample. Chlordane compound concentrations in fish composites from two sites at the eastern end of the sampling area were 0.127 and 0.228 μg/g wet weight, respectively, which are high enough to cause concern. Most aliphatic hydrocarbons detected were found at low concentrations and probably were natural in origin. We concluded that there are no serious contaminants concerns within the project area, but past use of arsenical pesticides may mean a legacy of elevated soil arsenic levels in parts of the area and some use of banned pesticides such as chlordane and DDT likely is still occurring near the refuge.  相似文献   
513.
514.
Among commonly employed methods of fast estimation of the soil biological activity a method of the oxygen consumption determination is used. The main goal of this research was an estimation of a soil respiratory metabolism using the constant pressure volumetric respirometer and also using the flow-through respirometer UNI-RES10.Soil respiration measurements were done using both types of respirometers in temperatures 10, 15, 20, 25, 30 and 35 °C, keeping up the constant humidity. The investigated soil was a soil humus belonged to organic soils from the Dziekanów Leny field. The soil respiration was also measured for 8 plant communities in Sudeten Mountains with various respiration intensity.After the experiments it was stated that both measuring instruments could be used for the soil metabolism evaluation. Readouts obtained from the UNI-RES10 respirometer are smaller then readouts when using the constant pressure volumetric respirometer. The flow-through respirometers have to be calibrated to obtain results comparable with these from volumetric ones. The volumetric and flow-through respirometry methods are useful for the comparative analysis of metabolism levels.  相似文献   
515.
516.
Practitioners and academic researchers increasingly look to evaluation of health impact assessment (HIA) to improve its practice, its efficiency and its legitimacy. Evaluation is also used to account to policy-makers, who express doubts that the benefits of HIA justify its costs. Until recently evaluation of HIA focused on instrument design and procedures but now the focus needs to shift to analysis of the interaction of HIA and decision-making. Multiple case studies have been applied to identify the conditions in which HIA produces the desired benefits. These studies used analytical concepts derived from the literature on evaluation, knowledge utilization, science of sociology and knowledge management.This paper describes a case study in which the strategic motives of the decision-makers affected the impact of an HIA. This HIA comprised of a quantitative environmental model ‘City & Environment’ that was used to assess environmental health impacts of an urban reconstruction plan in a Dutch city. The evaluation of the HIA shows that the decision to follow the recommendations of the HIA was part of a damage control strategy. The more HIA goals deviate from the policy problem and the less HIA is embedded in institutional procedures, then the more HIA impact will be subject to strategic decision-making behaviour. Appropriate cognitive and social strategies are needed to avoid ‘negative learning’ in those the HIA seeks to influence.  相似文献   
517.
For most plant species growing in polluted areas genotoxicity assays are not available. We have studied the possibility of using the alkaline protocol of the Comet assay as a method for detecting induced DNA damage in a grass Calamagrostis epigejos, growing wild in highly polluted areas. To calibrate the Comet assay for C. epigejos, two model mutagens were applied: the monofunctional alkylating agent ethyl methanesulfonate (EMS) and gamma-rays. With increasing concentrations of EMS (0 to 10 mM, 18 h treatment at 26 degrees C) applied on excised leaves, the DNA damage, as expressed by the tail moment (TM) values, increased from 4.7 +/- 0.9 to 60.8 +/- 2.7 microns. After gamma irradiation (0 to 30 Gy) the TM value increased from 4.2 +/- 0.2 to 48.1 +/- 1.7 microns. A 24 to 72 h recovery of leaves after EMS treatment in an EMS-free medium did not result in a significant change in the induced EMS damage. By contrast, a 24 h recovery after gamma-irradiation led to a complete repair of DNA damage measurable by the Comet assay. We have measured the DNA damage in nuclei of leaves of C. epigejos plants growing in the area of a sediment reservoir with substrates from uranium mining, where the ore was exploited through leaching with sulfuric acid. The average specific activity of natural radionuclides measured in the substrate was for 226Ra = 11,818 Bq kg-1, for 232Th = 66 Bq kg-1 and for 40K = 75 Bq kg-1. No significant increase in the DNA damage in plants growing on the sediment substrate above the DNA damage in control plants was detected by the Comet assay.  相似文献   
518.
The pelagic crustacean Euphausia pacifica Hansen was sampled with a multiple-sample 1.0 m2 Tucker trawl and a multiple-sample 1.0 m2 vertical net in Dabob Bay, Washington on 17 dates between May 1985 and October 1987. Size (stage) structure and abundance of the population were determined for each date, while vertical distribution and diel migration were determined for 13 dates. Although internannual variability in both timing and magnitude of events occurred, consistent patterns were discernable. The population produced a large pulse of larvae (2 to 5 mm) in late spring of each year, apparently in response to the vernal phytoplankton bloom. Much lower abundances of larvae occurred during summer and autumn of each year, and larvae were completely absent during winter. Recruitment to the juvenile (6 to 9 mm) and adult (10 mm) stages was strongest during the summer, with abundances of these individuals peaking in summer and autumn. Individual growth rates, determined by modal progression analysis, were calculated for E. pacifica. Rates ranged from zero for some adult cohorts during the winter to 0.12 mm d-1 for larvae during spring. The latter are among the highest ever reported for this species in the field. The vertical distributions and diel vertical migrations (DVM) of E. pacifica varied seasonally and between size (stage) classes. At night, all size classes were distributed in the surface layer (upper 25 m) irrespective of season or year. During the day, the larger/older stages were always distributed at middepths (50 to 125 m). In contrast, the daytime distribution of the larvae was more variable, being concentrated at the surface during spring and early summer of 1985, and at increasing depths later in the summer and autumn of 1985 and again in spring of 1986. This resulted in invariant DVM in the juveniles and adults, but variable DVM in the larvae, the latter of which is hypothesized to be a response to variable abundances of zooplanktivorous fish.  相似文献   
519.
We show that (i) subsidies for renewable energy policies with the intention of encouraging substitution away from fossil fuels may accentuate climate change damages by hastening fossil fuel extraction, and that (ii) the opposite result holds under some specified conditions. We focus on the case of subsidies for renewable resources produced under increasing marginal costs, and assume that both the renewable resources and the fossil fuels are currently in use. Such subsidies have a direct effect and an indirect effect working in opposite directions. The direct effect is the reduction in demand for fossil fuels at any given price. The indirect effect is the reduction in the current equilibrium price for fossil fuels, which tends to increase the amount of fossil fuels demanded. Whether the sum of the two effects will actually result in an earlier or later date of exhaustion of the stock of fossil fuels depends on the curvature of the demand curve for energy and of the supply curve for the renewable substitute.  相似文献   
520.
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