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   374篇
  免费   48篇
  国内免费   149篇
安全科学   57篇
废物处理   15篇
环保管理   50篇
综合类   270篇
基础理论   93篇
污染及防治   56篇
评价与监测   11篇
社会与环境   10篇
灾害及防治   9篇
  2024年   1篇
  2023年   6篇
  2022年   13篇
  2021年   13篇
  2020年   17篇
  2019年   14篇
  2018年   7篇
  2017年   22篇
  2016年   18篇
  2015年   23篇
  2014年   29篇
  2013年   34篇
  2012年   42篇
  2011年   47篇
  2010年   31篇
  2009年   20篇
  2008年   24篇
  2007年   31篇
  2006年   40篇
  2005年   30篇
  2004年   16篇
  2003年   14篇
  2002年   7篇
  2001年   9篇
  2000年   7篇
  1999年   12篇
  1998年   4篇
  1997年   5篇
  1996年   10篇
  1995年   1篇
  1994年   3篇
  1993年   1篇
  1992年   6篇
  1991年   2篇
  1989年   1篇
  1988年   2篇
  1987年   2篇
  1986年   1篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1978年   2篇
  1977年   1篇
排序方式: 共有571条查询结果,搜索用时 15 毫秒
531.
在固体酸催化下 ,粗苯酐与杂醇油直接酯化再经减压蒸馏制备邻苯二甲酸C4 ~C5混合酯增塑剂 ,经中试生产表明 ,该工艺技术是可行的 ,苯酐及C4 ~C5醇回收利用率均可达 90 %以上 ,且废水排放量很少。其最佳工艺条件为 :(1)酯化反应  (C4 ~C5醇 )∶(苯酐 ) =2 6∶1 0 ,催化剂用量为反应物总质量的 1 5 % ,温度 110~ 16 0℃ ,时间 5h ,反应在搅拌下进行 ;(2 )减压蒸馏 蒸馏压力 <2 0kPa。  相似文献   
532.
温度和污泥浓度对短程内源反硝化脱氮的影响   总被引:5,自引:0,他引:5  
采用SBR反应器,以亚硝酸盐(NO2-)作电子受体,对温度和污泥浓度对短程内源反硝化脱氮的影响进行了研究。结果表明,在15~30℃范围内,随着温度的升高,短程内源反硝化速率逐渐增高,温度每升高10℃,反硝化速率增加3倍。温度一定时,污泥浓度增加,短程内源反硝化速率也相应增加,当MLSS从4000mg/L变化到12000mg/L时,反硝化速率从开始的0.0259gN/(gVSS·d)增加到了0.0378gN/(gVSS·d),即增大了近1.5倍,即采用较高污泥浓度可以大大节省反应时间。  相似文献   
533.
行业特性和技术约束致使一些制造企业产生大量的副产品和边角废料,对环境造成巨大压力.而可持续发展要求则促使制造企业寻求一种与自然生态环境和谐共处、资源良性循环的物流模式,构建再循环物流系统.因此,为了有效解决经济发展与环境的矛盾,促进产业间或产业内工业企业进行循环经济实践,设计具有生态柔性的B2B网络下再循环物流系统的结构模型.运用环境影响分析模型,分析再循环物流系统各个业务单元的环境影响因子.基于结构模型,运用混合整数规划方法,构建再循环物流系统多目标优化模型.该模型同时考虑了再循环系统的物流成本和外部环境影响;适合于多物料、单周期、有产能限制的再循环网络设施选址-分配问题.通过算例验证了模型的有效性.   相似文献   
534.
ABSTRACT: Escherichia coli. Streptococcus faecalis, Salmonella typhimurium, and Staphylococcus aureus were tested in pure culture and in various combined mixed cultures to determine effects of the presence of carbaryl in water. Oxygen uptake of E. coli and S. typhimirium was stimulated by five mg/L carbaryl when mixed together, but no stimulation was observed when either organism was tested alone or with other bacteria. In mixed culture the survival time of S. faecalis was reduced in the presence of five mg/L carbaryl; however, the survival time of both S. aureus and S. typhimurium was increased in the presence of five mg/L carbaryl. Implications of these results are discussed.  相似文献   
535.
市政污泥与生活垃圾掺烧工艺探讨   总被引:1,自引:0,他引:1  
本文概括介绍了国内市政污泥处理处置的现状和目前不同类型的市政污泥处理处置技术,根据国外经验和国内情况做了市政污泥与生活垃圾掺烧的探讨,并总结了通过掺烧试验进行的工程应用实践。  相似文献   
536.
In the pulp and paper industry, lignin and other color compounds are removed by chemical agents in bleaching process. Use of chlorine-based agents results in production of degradation products which include various chloro-organic derivatives. Since these new compounds are highly chlorinated, they cause a problem in the treatment of pulp and paper industry wastewaters. Chemical precipitation, lagooning, activated sludge, and anaerobic treatment are the processes used for treating pulp and paper effluents. Furthermore, a combination of these processes is also applicable. In this study, the effluent of Dalaman SEKA Pulp and Paper Industry was examined for its toxic effects on anaerobic microorganisms by anaerobic toxicity assay. Additionally, this wastewater was applied to a sequential biotreatment process consisting of an upflow anaerobic sludge blanket as the anaerobic stage and a once-through completely mixed stirred tank as the aerobic stage. Results indicated that: (1) Dalaman SEKA Pulp and Paper Industry wastewater exerted no inhibitory effects on the anaerobic cultures under the studied conditions, and (2) application of a sequential biological (anaerobic/aerobic) system to treat the Dalaman SEKA Pulp and Paper Industry wastewater resulted in approximately 91% COD and 58% AOX removals at a HRT of 5 and 6.54 h for anaerobic and aerobic, respectively.  相似文献   
537.
污泥通过好氧堆肥反应腐熟,除去其中有害物质及降低重金属含量后达到农用标准,然后在温室大棚内进行种植实验,将堆肥按不同混配方式施入土壤中。研究污泥混配土中氮磷的变化表明:混配土中的总氮在种植过程中被作物吸收和自身流失,有一定程度降低;氨态氮经过转化和作物吸收,降低很快。混配土中总磷的含量在种植过程中基本不变,作物生长只需少部分磷,在温室中种植避免了磷的流失;速效磷的变化较为复杂,种植一段时间后,速效磷呈现上升趋势。  相似文献   
538.
混合污泥接种的厌氧氨氧化处理污泥脱水液的启动   总被引:9,自引:1,他引:8       下载免费PDF全文
采用UASB反应器,接种由好氧颗粒污泥、厌氧颗粒污泥、氧化沟活性污泥及短程硝化活性污泥组成的混合污泥,以污泥脱水液经短程硝化处理后水质为进水,在温度(30±0.2)℃, pH值7.3~7.9,初期进水氨氮、亚硝氮容积负荷分别为0.07, 0.10kg/(m3×d)条件下,经过24d运行,氨氮和亚硝氮得到稳定同步去除,186d时TN去除负荷达0.99 kg/(m3×d).启动初期,氨氮、亚硝氮进水浓度分别为20,30mg/L,二者浓度随去除量增加而逐级增加,最高分别达到157,216mg/L;启动过程中,系统受到O2抑制以及O2和亚硝氮基质的连续抑制,分别经过了约10d和30d才得以恢复. 厌氧氨氧化(ANAMMOX)反应与反硝化反应可以共存于系统中,产气量与总氮去除呈正比关系,可及时地指示系统运行状态,对气体成分检测,氮气含量在99.8%.在稳定期ANAMMOX反应呈pH值升高而碱度略有降低.接种混合污泥、低基质负荷启动ANAMMOX,可30d内实现稳定的氨氮和亚硝氮同步去除,180d左右启动成功.  相似文献   
539.
Monitoring of non-point source pollutants load from a mixed forest land use   总被引:3,自引:0,他引:3  
The aim of this study was to determine the unit load of NPS (non-point source) pollutants including organic variables such as BOD (biochemical oxygen demand),COD (chemical oxygen demand) and DOC (dissolved organic carbon),nitrogen and phosphorus constituents,and suspended solids (SS) and their event mean concentration (EMC) of runoff flows from a water-shed of mixed forest land use by intensive field experiments.Field monitoring for continuous measurements of rainfall,flow,and water quality was conducted over 12 storm events during 2008–2009 using automated and manual sampling methods.The EMCs of individual runoff event were estimated for each water quality constituent based on the flow rate and concentration data of runoff discharge.The average EMCs of BOD,COD,DOC,SS,TN (total nitrogen),NH 4+ -N,NO 3- -N,TP (total phosphorus),PO 43- -P from the mixed forest land were 1.794,3.498,1.462,10.269,0.862,0.044,0.634,0.034,and 0.005 mg/L,respectively.The annual unit loads of BOD,COD,DOC,SS,TN,NH 4+ -N,NO 3- -N,TP and PO 43--P were estimated as 66.9,133.2,55.5,429.8,36.5,1.6,26.9,1.3 and 0.1 kg/(ha·yr),respectively.In addition,affecting parameters on the EMCs were investigated by statistic analysis of the field data.As a result,significant correlations with precipitation,rainfall intensity,and total runoff flows were found in most constituents.  相似文献   
540.
Total mercury in wild fish in Guizhou reservoirs, China   总被引:2,自引:0,他引:2  
The health hazard of mercury (Hg) compounds is internationally recognized, and the main pathways for methylmercury (MeHg) intake in humans are through consumption of food, especially fish. Given the large releases of Hg to the environment in China, combined with the fast development of hydropower, this issue deserves attention. Provided similar mobilization pathways of Hg in China as seen in reservoirs in North America and Europe one should expect increased Hg contamination in relation to future hydropower reservoir construction in this country. This study presents total Hg (THg) concentrations in wild fish from six Guizhou reservoirs, China. The THg concentrations in fish were generally low despite high background levels in the bedrock and depositions from local point sources. The over all mean ± SD concentration of THg was (0.066 ± 0.078) μg/g (n = 235). After adjusting for among-reservoir variation in THg, there were significant differences in THg among functional groups of the fish, assumed to re?ect trophic levels. Predicted THg- concentration ratios, retrieved from a mixed linear model, between the functional groups were 9:4:4:1 for carnivorous, omnivorous, planktivorous and herbivorous fish. This result indicated that MeHg accumulation may prevail even under circumstances with short food chains as in this Chinese water system. No fish exceeded recommended maximum THg limit for human consumption set by World Health Organization and the Standardization Administration of China (0.5 μg/g fish wet weight (ww)). Only six fish (2.5%) exceeded the maximum THg limit set by US Environmental Protection Agency (0.3 μg/g fish ww).  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