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   516篇
  免费   9篇
  国内免费   57篇
安全科学   7篇
废物处理   22篇
环保管理   51篇
综合类   123篇
基础理论   117篇
污染及防治   172篇
评价与监测   69篇
社会与环境   18篇
灾害及防治   3篇
  2023年   4篇
  2022年   10篇
  2021年   13篇
  2020年   14篇
  2019年   9篇
  2018年   9篇
  2017年   19篇
  2016年   23篇
  2015年   14篇
  2014年   23篇
  2013年   62篇
  2012年   11篇
  2011年   20篇
  2010年   25篇
  2009年   23篇
  2008年   23篇
  2007年   25篇
  2006年   23篇
  2005年   23篇
  2004年   18篇
  2003年   13篇
  2002年   19篇
  2001年   21篇
  2000年   11篇
  1999年   9篇
  1998年   4篇
  1997年   3篇
  1996年   7篇
  1995年   9篇
  1994年   7篇
  1993年   7篇
  1992年   3篇
  1991年   4篇
  1989年   4篇
  1988年   4篇
  1987年   3篇
  1986年   2篇
  1982年   5篇
  1979年   2篇
  1975年   3篇
  1974年   2篇
  1971年   4篇
  1966年   4篇
  1965年   5篇
  1964年   4篇
  1963年   5篇
  1961年   6篇
  1960年   2篇
  1958年   2篇
  1955年   2篇
排序方式: 共有582条查询结果,搜索用时 360 毫秒
551.
This paper discusses the need for critically evaluating regional-scale (~200–2,000 km) three-dimensional numerical photochemical air quality modeling systems to establish a model’s credibility in simulating the spatio-temporal features embedded in the observations. Because of limitations of currently used approaches for evaluating regional air quality models, a framework for model evaluation is introduced here for determining the suitability of a modeling system for a given application, distinguishing the performance between different models through confidence-testing of model results, guiding model development and analyzing the impacts of regulatory policy options. The framework identifies operational, diagnostic, dynamic, and probabilistic types of model evaluation. Operational evaluation techniques include statistical and graphical analyses aimed at determining whether model estimates are in agreement with the observations in an overall sense. Diagnostic evaluation focuses on process-oriented analyses to determine whether the individual processes and components of the model system are working correctly, both independently and in combination. Dynamic evaluation assesses the ability of the air quality model to simulate changes in air quality stemming from changes in source emissions and/or meteorology, the principal forces that drive the air quality model. Probabilistic evaluation attempts to assess the confidence that can be placed in model predictions using techniques such as ensemble modeling and Bayesian model averaging. The advantages of these types of model evaluation approaches are discussed in this paper.  相似文献   
552.
A sustainable forestry scenario aimed at meeting the projected biomassdemands, halting deforestation and regenerating degraded forests wasdeveloped and analyzed for additionality of mitigation and cost-effectivenessfor India. Similarly, mitigation potential of a commercial forestry scenarioaimed at meeting the biomass demands from forestry activities on privateland was assessed. India has a significant scale baseline scenario afforestationand effective forest conservation activities. India is afforesting at an averagegross rate of 1.55 × 106 ha yr-1 over the past 10 years, while the gross deforestation rate was 0.272 × 106 ha yr-1 during the same period. The sustainable forestry scenario could lead to an additional carbon (C) stock of 237 × 106 Mg C during 2000 to 2012, while the commercial forestry scenario apart from meeting all the incremental biomass demands (estimated for 2000 to 2015) could potentially lead to an additional carbon stock of 78 × 106Mg C during 2000 to 2012. Short- and Long-rotation forestry activities arecommercially viable. With appropriate policies and financial incentives allthe industrial wood, sawnwood and commercial fuelwood requirementcould be met through commercial forestry, so that government funds couldbe dedicated for conserving state owned forests and meeting subsistencebiomass demands. The commercial forestry activities could receive financialsupport under greenhouse gas (GHG) abatement programmes. The government, however, needs to develop institutions and guidelines to process, evaluate, approve and monitor forestry sector mitigation projects.  相似文献   
553.
A small study was undertaken to examine the microbiological characteristics of spent mushroom compost (SMC), which is the major waste by-product of the mushroom industry and which is regularly disposed off by application to agricultural land. The primary aim of this study was to examine SMC for the presence of faecal bacterial pathogens, including Campylobacter spp., Salmonella spp. and Listeria monocytogenes. Secondly it was desirable to quantify bacterial and fungal populations within SMC, and also qualitatively identify the diversity of bacterial populations within SMC, through employment of rDNA PCR and direct sequencing techniques on the culturable microflora. Conventional microbiological analyses of SMC material (n=30) from six commercial operations in both Northern Ireland and the Republic of Ireland, failed to detect Salmonella spp, Listeria spp. or Campylobacter spp. in any of the SMC material examined. Total aerobic plate counts gave a mean count of log10 7.01 colony forming units (cfu) per gram SMC material (range: log10 6.53-7.52 cfu/g). Fungal counts gave a mean count of log(10) 4.57 cfu per gram SMC material (range: log10 3.93-4.98 cfu/g). From a total of greater than 50 colony picks, a total of 12 bacterial morphotypes were identified and were further examined by employment of partial 16S rRNA gene amplification and sequencing techniques, yielding several genera and species, including Bacillus licheniformis, Bacillus subtilis, Klebsiella/Enterobacter sp. Microbacterium sp. Paenibacillus lentimorbus, Pseudomonas mevalonii, Sphingobacterium multivorum and Stenotrophomonas sp. This is the first preliminary report on the microbial diversity of SMC waste and demonstrates the presence of several species that have not been previously described in SMC, in addition to two potentially novel species within the genera Microbacterium and Stenotrophomonas. It is thereby important to examine the ecological microbe-microbe and plant-microbe interactions that are occurring between the native bacterial soil flora and those added annually (theoretically estimated at approximately 10(18) cells) through the application of SMC. Such studies would be beneficial in helping to ascertain the ecological consequences involved in the disposal of SMC waste on agricultural land.  相似文献   
554.
Kolleru lake is the largest fresh water lake in the districts of East and West Godavari of Andhra Pradesh, India. Many anthropogenic sources contribute to the heavy metal pollution in the lake and the bioaccumulation of heavy metals in fish helps in assessing the aquatic pollution. Total contents and fractionation of selected heavy metals, viz., Zn, Cu, Cd, Pb, Cr, Ni and Co were measured in sediment sample and three edible fish. The investigation aimed at revealing differences in the accumulation pattern of heavy metals in fish inhabiting sediments characterized by varying metal bioavailability. The metal concentrations were found to be greater than the background concentrations of sediments indicating the anthropogenic origin of metals. Good recovery values were obtained for metal contents in sediments and fish. Large fractions of Zn, Cd and Cu were associated with mobile fraction of sediment and showed greater bioaccumulation in fish whereas Ni and Co were least mobilisable. The results clearly indicate that the fish of Kolleru lake are contaminated with metals and not advisable for human consumption.  相似文献   
555.
The present study deals with the biochemical composition of Channa orientalis from a habitat polluted by slaughter house wastes in comparison to an unpolluted habitat of Mudasarlova stream of Visakhapatnam. The total proteins, carbohydrates and lipids were found to be less in the organisms collected from the polluted habitat. The probable reasons for these variations are discussed in detail.  相似文献   
556.
557.
Mussels are good bioaccumulators of metals and have been used as indicators for environmental monitoring. in this study on P. viridis from Pondicherry coast, metal content (aluminium, lead, cadmium, copper and zinc) were analysed in selected tissues and shell nacre for a period of one year. the metal content shows that digestive gland accumulates higher concentrations of metal ions followed by gill, mantle and shell. of the different components (digestive gland, gill, mantle and shell nacre) of the organism, only shell nacre exhibited a significant relationship with ambient levels and therefore can be applied to temporal monitoring of metal contamination.  相似文献   
558.
根据IPCC的国家温室气体排放清单编制指南,初步计算了中国动物废弃物源的甲烷排放量。20年间,中国动物废弃物源的甲烷排放量增加了75%,1990年的甲烷排放量为1.198Tg,占全球的10%左右。并提出发展沼气池、贮留池不仅能减少甲烷排放,而且能产生其它的环境效益和经济效益。  相似文献   
559.
Removal of Cr6 + and Ni2+ from aqueous solution using bagasse and fly ash   总被引:9,自引:0,他引:9  
Raw bagasse and fly ash, the waste generated in sugar mills and boilers respectively have been used as low-cost potential adsorbents. Raw bagasse was pretreated with 0.1N NaOH followed by 0.1N CH3COOH before its application. These low-cost adsorbents were used for the removal of chromium and nickel from an aqueous solution. The kinetics of adsorption and extent of adsorption at equilibrium are dependent on the physical and chemical characteristics of the adsorbent, adsorbate and experimental system. The effect of hydrogen ion concentration, contact time, sorbent dose, initial concentrations of adsorbate and adsorbent and particle size on the uptake of chromium and nickel were studied in batch experiments. The Sorption data has been correlated with Langmuir, Freundlich and Bhattacharya and Venkobachar adsorption models. The efficiencies of adsorbent materials for the removal of Cr(VI) and Ni(II) were found to be between 56.2 and 96.2% and 83.6 and 100%, respectively. These results were obtained at the optimized conditions of pH, contact time, sorbent dose, sorbate concentration of 100 mg/l and with the variation of adsorbent particles size between 0.075 and 4.75 mm. The order of selectivity is powdered activated carbon > bagasse > fly ash for Cr(VI) removal and powdered activated carbon > fly ash > bagasse for Ni(II) removal.  相似文献   
560.
文章分析了成都区域管制中心内的雷达、微波通信站、遥控台和卫星地面站等典型电磁设施的电磁辐射污染源状况,用电磁辐射分析仪对拟建成都区域管制中心及机场等典型环境中的电磁辐射水平开展了监测与评价,有针对性地提出了电磁辐射防护措施,为合理建设成都区域管制中心提供了辐射环境方面的科学依据。  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