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   267篇
  免费   7篇
安全科学   27篇
废物处理   28篇
环保管理   35篇
综合类   50篇
基础理论   55篇
污染及防治   51篇
评价与监测   16篇
社会与环境   10篇
灾害及防治   2篇
  2023年   5篇
  2022年   5篇
  2021年   3篇
  2020年   6篇
  2019年   5篇
  2018年   12篇
  2017年   10篇
  2016年   5篇
  2015年   14篇
  2014年   13篇
  2013年   19篇
  2012年   14篇
  2011年   15篇
  2010年   13篇
  2009年   14篇
  2008年   19篇
  2007年   10篇
  2006年   17篇
  2005年   4篇
  2004年   7篇
  2003年   7篇
  2002年   4篇
  2001年   8篇
  2000年   4篇
  1999年   6篇
  1998年   5篇
  1996年   2篇
  1995年   3篇
  1994年   6篇
  1993年   7篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1989年   2篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1981年   2篇
排序方式: 共有274条查询结果,搜索用时 15 毫秒
81.
82.
ABSTRACT: Our nation periodically reviews national water policy and considers its directions for the future. The most recent examination was directed at the western United States and the role of the federal agencies in meeting its needs. The West is no longer the frontier, but rather contains vibrant cities and booming centers of international trade, as well as tourism, mineral, and oil and gas development, agricultural, and other development. In this changing environment, federal water policies need to consider the long term sustainability of the West, provide justice to Indian tribes, protect the rivers and ecosystems on which natural systems depend, balance the needs of newcomers with those of agricultural users and communities, and meet a myriad of other demands. The Western Water Policy Review Advisory Commission has just concluded its review of these issues and issued its report. Key among the recommendations is the need to coordinate federal agencies at the basin and watershed level and make government more responsive to local needs, but within a framework that includes national mandates. The Commission's recommendations are presented here, along with some of the issues that surrounded the operations of the Commission.  相似文献   
83.
Sexual selection models suggest that female choice is based on male traits that indicate their genetic or environmental condition, consequently enhancing her reproductive success by direct or indirect benefits. We investigated the relationship between male foot colour and offspring condition in the blue-footed booby, a socially monogamous seabird, with conspicuous and variably condition-dependent coloured feet that are selected by females. In a cross-fostering experiment, we found that chick condition was related to the foot colour of the foster father and, to some extent, to the foot colour of the genetic father; thus overall, the fathers sexual ornamentation (genetic and foster) explained 32% of variance of chick condition. These data suggest that foot colour, a dynamic sexually selected trait, is mostly a signal of parental contribution. In species in which males provide parental care, females may choose mates with higher parental ability. Overall, our data suggest that colourful integuments are honest signals of parental ability.Communicated by J. Graves  相似文献   
84.
Our objectives are to evaluate inter-continental source-receptor relationships for fine aerosols and to identify the regions whose emissions have dominant influence on receptor continents. We simulate sulfate, black carbon (BC), organic carbon (OC), and mineral dust aerosols using a global coupled chemistry-aerosol model (MOZART-2) driven with NCEP/NCAR reanalysis meteorology for 1997–2003 and emissions approximately representing year 2000. The concentrations of simulated aerosol species in general agree within a factor of 2 with observations, except that the model tends to overestimate sulfate over Europe in summer, underestimate BC and OC over the western and southeastern (SE) U.S. and Europe, and underestimate dust over the SE U.S. By tagging emissions from ten continental regions, we quantify the contribution of each region's emissions on surface aerosol concentrations (relevant for air quality) and aerosol optical depth (AOD, relevant for visibility and climate) globally. We find that domestic emissions contribute substantially to surface aerosol concentrations (57–95%) over all regions, but are responsible for a smaller fraction of AOD (26–76%). We define “background” aerosols as those aerosols over a region that result from inter-continental transport, DMS oxidation, and emissions from ships or volcanoes. Transport from other continental source regions accounts for a substantial portion of background aerosol concentrations: 36–97% for surface concentrations and 38–89% for AOD. We identify the Region of Primary Influence (RPI) as the source region with the largest contribution to the receptor's background aerosol concentrations (or AOD). We find that for dust Africa is the RPI for both aerosol concentrations and AOD over all other receptor regions. For non-dust aerosols (particularly for sulfate and BC), the RPIs for aerosol concentrations and AOD are identical for most receptor regions. These findings indicate that the reduction of the emission of non-dust aerosols and their precursors from an RPI will simultaneously improve both air quality and visibility over a receptor region.  相似文献   
85.
The oxidative degradation of polyolefins in the presence of transition metal catalysts is well known in the patent and technical literature. It has been suggested that a properly designed oxidatively degradable polymer could be used in limited lifetime articles and also on those whose primary method of disposal is composting, wherein the thermal activity is used to accelerate the oxidation process. The results of a detailed study of transition metal reactivity in the presence of numerous oxidation promoting species in polyolefins are presented. The oxidative degradation of these polyolefins was demonstrated at moderate temperatures under air and in a simulated compost environment. Approaches to determining the ultimate fate of these materials are discussed.  相似文献   
86.
Energy transition is the process whereby the volume and proportion of commercial energy increases so as to replace traditional fuels as the main energy source. In South and South-East Asia the extent to which this transition has taken place varies within and between countries. In general, in the urban areas, the process is more advanced than in rural areas. It is also more advanced in the larger towns than the smaller ones and more advanced within higher income groups. In rural areas industry is a large consumer of traditional energy and many rural peoples earn their livelihoods as suppliers of traditional energy to industry. For both economic and social reasons the transition process has been slower in rural households than in urban households. This must change as for much of the rural areas of South and South-East Asia, increasing population and increasing energy demand are creating pressures on the biomass which cannot be sustained.  相似文献   
87.
Environmental Science and Pollution Research - Sugarcane bagasse, a largely available waste worldwide, was submitted to solid-state fermentation (SSF) using the fungus Metarhizium anisopliae,...  相似文献   
88.
For high volume air sampling, New York State uses a random once every six days schedule. To avoid double travel, this usually requires leaving filters mounted for five days before the actual sampling period of 24 hr. The starting and stopping of the sampling is controlled by a 7 day timer. (At the maximum, it is possible that a filter could be in place for 10 days with the motor idle.) The purpose of this investigation was to determine whether the filter collects a significant weight of particulate matter during the period the motor is idle, and what effect the collected windborne particulate matter has on computed TSP concentrations.  相似文献   
89.
Recent advances in the development of receptor-oriented source apportionment techniques (models) have provided a new approach to evaluating the performance of particulate dispersion models. Rather than limiting performance evaluations to comparisons of particulate mass, receptor model estimates of source impacts can be used to open new opportunities for in-depth analysis of dispersion model performance. Recent experiences in the joint application of receptor and dispersion models have proven valuable in developing increased confidence in source impact projections used for control strategy development. Airshed studies that have followed this approach have identified major errors in emission inventory data bases and provided technical support for modeling assumptions.

This paper focuses on the joint application of dispersion and receptor models to particulate source impact analysis and dispersion model performance and evaluation. The limitations and advantages of each form of modeling are reviewed and case studies are examined. The paper is offered to provide several new perspectives into the model evaluation process in the hope that they may prove useful to those that manage our nation’s air resources.  相似文献   
90.
The water-soluble fraction (WSF) of petroleum contains a mixture of polycyclic aromatic hydrocarbons, volatile hydrocarbons, phenols, and heterocyclic compounds, considered deleterious to aquatic biota. Marine “pejerrey” Odontesthes argentinensis (Teleostei: Atherinopsidae) has a great commercial importance in local fisheries and a high potential for aquaculture. The aim of this study was to evaluate the histopathological effects in “pejerrey” larvae exposed to different concentrations of petroleum WSF. The chronic toxicity test was conducted with newly hatched larvae exposed for 21 days to sublethal concentrations of WSF (2.5, 5, 10, and 20 % of WSF), plus one control. Survival and growth were significantly lower in the highest concentration. Several histopathological changes were found in the gills (e.g., hyperplasia, aneurisms, edema, and necrosis), kidney (e.g., nuclear alterations, decrease in the hematopoietic cells), and liver (e.g., hypertrophy, karyorrhexis, and karyopyknosis). An index of branchial lesion was proposed to standardize gill lesions to different pollutants.  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