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   2449篇
  免费   422篇
  国内免费   1171篇
安全科学   180篇
废物处理   126篇
环保管理   334篇
综合类   2461篇
基础理论   260篇
污染及防治   178篇
评价与监测   262篇
社会与环境   214篇
灾害及防治   27篇
  2024年   26篇
  2023年   97篇
  2022年   161篇
  2021年   213篇
  2020年   191篇
  2019年   169篇
  2018年   166篇
  2017年   181篇
  2016年   200篇
  2015年   207篇
  2014年   213篇
  2013年   254篇
  2012年   273篇
  2011年   286篇
  2010年   178篇
  2009年   152篇
  2008年   98篇
  2007年   121篇
  2006年   125篇
  2005年   95篇
  2004年   79篇
  2003年   91篇
  2002年   66篇
  2001年   86篇
  2000年   66篇
  1999年   53篇
  1998年   35篇
  1997年   36篇
  1996年   29篇
  1995年   25篇
  1994年   16篇
  1993年   14篇
  1992年   16篇
  1991年   11篇
  1990年   5篇
  1989年   1篇
  1987年   2篇
  1986年   4篇
  1982年   1篇
排序方式: 共有4042条查询结果,搜索用时 913 毫秒
831.
The impact of air traffic on the global atmosphere is characterised by a high degree of uncertainty, concerning both the physico-chemical phenomena involved and the extent of the forcing due to anthropogenic emissions. The different effects of these emissions (e.g. on climate change, stratospheric ozone depletion, acidification, tropospheric ozone formation) are dealt with by different international bodies and conventions (e.g. IPCC, EMEP. . .) which are trying to define a standard methodology allowing countries to evaluate their contributions to global aircraft emissions and to report these figures in a standardised way. The paper compares different methodologies proposed by the joint EMEP/CORINAIR 'Atmospheric Emission Inventory Guidebook' for estimating aircraft emissions. Adjustments to these methodologies have been proposed, in order to integrate some additional data such as the total amount of flight hours per aircraft type or fuel consumption per trip. In case detailed information is not available, we recommend the use of a VERY SIMPLE methodology which may yield acceptable results, provided that every country makes adequate assumptions on the average aircraft type.  相似文献   
832.
介绍了大气中可吸入颗粒物的来源分析,并对工业燃烧源和小型燃烧源的排放因子、排放测量方面的研究进行了总结。最后进一步探讨了燃烧源中可吸入颗粒物的未来研究重点和研究方向。  相似文献   
833.
PM_(2.5)and PM_(10)samples were collected at four major cities in the Pearl River Delta(PRD),South China,during winter and summer in 2002.Six water-soluble ions,Na~ ,NH_4~ ,K~ ,Cl~-,NO_3~- and SO_4~(2-)were measured using ion chromatography.On average,ionic species accounted for 53.3% and 40.5% for PM_(2.5)and PM_(10),respectively in winter and 39.4% and 35.2%,respectively in summer. Secondary ions such as sulfate,nitrate and ammonium accounted for the major part of the total ionic species.Sulfate was the most abundant species followed by nitrate.Overall,a regional pollution tendency was shown that there were higher concentrations of sulfate, nitrate and ammonium in Guangzhou City than those in the other PRD cities.Significant seasonal variations were also observed with higher levels of species in winter but lower in summer.The Asian monsoon system was favorable for removal and diffusion of air pollutants in PRD in summer while highly loading of local industrial emissions tended to deteriorate the air quality as well.NO_3~-/SO_4~(2-) ratio indicated that mobile sources have considerably contribution to the urban aerosol,and stationary sources should not be neglected. Besides the primary emissions,complex atmospheric reactions under favorable weather conditions should be paid more attention for the control of primary emission in the PRD region.  相似文献   
834.
To understand the effects of long-term amendment of organic manure and N fertilizer on N2O emission in the North China Plain, a laboratory incubation at different temperatures and soil moistures were carried out using soils treated with organic manure (OM), half organic manure plus half fertilizer N (HOM), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer PK (NK) and control (CK) since 1989. Cumulative N2O emission in OM soil during the 17 d incubation period was slightly higher than in NPK soil under optimum nitrification conditions (25℃ and 60% water-filled pore space, WFPS), but more than twice under the optimum denitrification conditions (35℃ and 90% WFPS). N2O produced by denitrification was 2.1-2.3 times greater than that by nitrification in OM and HOM soils, but only 1.5 times greater in NPK and NP soils. These results implied that the long-term amendment of organic manure could significantly increase the N2O emission via denitrification in OM soil as compared to NPK soil. This is quite different from field measurement between OM soil and NPK soil. Substantial inhibition of the formation of anaerobic environment for denitrification in field might result in no marked difference in N2O emission between OM and NPK soils. This is due in part to more rapid oxygen diffusion in coarse textured soils than consumption by aerobic microbes until WFPS was 75% and to low easily decomposed organic C of organic manure. This finding suggested that addition of organic manure in the tested sandy loam might be a good management option since it seldom caused a burst of N2O emission but sequestered atmospheric C and maintained efficiently applied N in soil.  相似文献   
835.
负外部成本内部化约束下的煤炭开采税费水平研究   总被引:1,自引:0,他引:1  
煤炭开采中面临严重的代际负外部性和生态环境负外部性问题,分别运用使用者成本法和直接市场法测算了煤炭资源开采中的代际负外部成本和生态环境负外部成本。根据两个负外部成本充分内部化的要求,提出煤炭开采中税费水平的调整目标。以2008年为例,煤炭开采中资源税的征收标准应由目前的从量0.3-5元/t(约从价1%)提至从价10%;开采吨煤应交的生态环境费用标准应由目前的24元/t提至64.23-68.47元/t,即每吨提高40.23-44.47元。综合资源税和生态环境费用的提高幅度,煤炭开采活动中的税费水平应提高约21-22个百分点;通过比较现行税费制度下煤炭开采企业实交的资源税费、生态环境税费总额与企业应交的资源、生态环境费用总额之间的差距,指出目前我国政府对开采企业隐性税费补贴的规模水平,根据价差法计算得出取消此部分税费补贴将可以削减3 653.69万tCO2排放。  相似文献   
836.
Foreign trade drives China’s growth,but as the trade scale continues to expand,the carbon emissions also increase quickly.Based on the industry panel data from 1996 to 2010,this paper calculates carbon emissions of 27manufacturing industries.According to the intensity of carbon emissions,this paper divides the manufacturing sectors into low carbon and high carbon manufacturing industry and then analyzes the carbon emission trends.Next,the paper uses the feasible generalized least square regression to verify the existence of environmental Kuznets curve(EKC)of the manufacturing industry’s carbon.In order to investigate the carbon leakage problem,the regression also includes the interaction term between trade and industrial value added.Our findings are as follows:the carbon emissions of the whole manufacturing industry and low carbon manufacturing industry accord with the EKC curve,but have a linear relationship with the high carbon manufacturing industry;trade reduces the carbon emissions of the whole manufacturing industry and low carbon manufacturing industry,but it increases those of the high carbon manufacturing industry;for the whole manufacturing industry and low carbon manufacturing industry,there is no carbon leakage,but it exists in the high carbon manufacturing industry.On the whole,pollution haven hypothesis does not hold up in China,and China does not need to limit industry foreign trade to reduce the emission of CO2.But the manufacturing industry will still be the main engine of the economic growth,and therefore our country should make an effective low-carbon policy,introduce advanced technology,increase R&D investment into lowcarbon technologies,and upgrade and transform the original equipment to change the backward mode of production.  相似文献   
837.
城市是人类生产和生活的中心,超过75%的温室气体从城市产生,其中又以城市产业部门能源消费和工业过程非能源产生的CO2为主。本文基于投入产出模型,评价城市产业部门3个不同层次的CO2排放。以重庆为案例,核算其2002-2008年产业部门三个层次的CO2排放,包括能源消费直接排放、购买电力间接排放和全生命周期排放,并进行多层次对比。结果显示传统能源消耗和购买电力为对象的核算方法低估了产业部门CO2排放水平。2002-2008年,重庆各产业部门排放量逐年增加,碳排放强度整体呈现下降趋势。煤炭开采和洗选业、非金属矿采选业、非金属矿物制品业、电力、热力的生产和供应业,化学工业、金属冶炼及压延加工业、交通运输、仓储及邮电通讯业部门共7大行业是重庆碳排放的重点行业。部门交通设备制造业是重庆的优势产业,排放总量大,但是排放强度却相对较小,因此应大力发展该产业以促进重庆市低碳经济的发展。  相似文献   
838.
节能减排目标任务的制定需要依据科学合理的CO2排放量测算。现有的IPCC提供的CO2排放量计算方法仅考虑一次能源燃料所产生的CO2,未考虑到二次能源省际调配的情况,不能真实反映各省CO2排放情况。本研究提出了考虑二次能源省际调配情况下CO2排放量的计算方法,并以2009年的数据为例,对各省能源消费CO2排放量进行了计算。考虑二次能源省际调配后,传统的能源大省如内蒙古、山西的CO2排放总量下降,东部沿海省份的CO2排放总量上升。中西部地区的CO2排放强度仍显著高于东部地区。中西部地区存在能源利用效率低、能源加工技术设备落后的情况,导致了西部地区的CO2排放强度偏高。建议中央在实施西部大开发"十二五"规划时,应当加强对中西部地区能源加工行业的投资,改善能源加工技术,改良加工设备,提高能源加工效率,降低CO2排放强度。建议由能源调入省向能源调出省份实施补偿。该部分补偿资金用于调出省的能源产业升级改造,以顺利实现节能减排的目标。  相似文献   
839.
本文采用考虑反馈性出口隐含碳的MRIO模型,测算了2000—2011年中国14个制造业行业出口隐含碳排放强度;在此基础上,基于全球价值链(GVC)分工地位的视角,理论分析并实证检验了不同技术进步路径对中国制造业出口隐含碳排放强度的影响。研究发现:中间品进口、自主研发、模仿创新显著降低了中国制造业出口隐含碳排放强度,而国外技术引进和外商直接投资(FDI)对中国制造业出口隐含碳排放强度的影响不显著;提升中国制造业在GVC中的国际分工地位能够显著降低其出口隐含碳排放强度。进一步研究发现,不同技术进步路径对中国制造业出口隐含碳排放强度的作用效果受到制造业在GVC中的国际分工地位的影响,并表现出明显的门槛特征,即只有中国制造业在GVC中的分工地位越过门槛值后,技术进步路径才能显著降低中国制造业出口隐含碳排放强度。此外,将制造业分为知识密集型、资本密集型和劳动密集型三类,发现不同技术进步路径对中国制造业出口隐含碳排放强度还存在着显著的行业差异。因此,中国制造业应充分发挥中间品进口、自主研发、模仿创新在降低中国制造业出口隐含碳排放强度中的作用,在引进FDI和国外技术的过程中,优先考虑引进发达国家的先进低碳制造技术和清洁生产技术。同时,中国制造业还应积极培育自身竞争优势,构建自我主导的国内价值链和区域价值链体系,主动嵌入全球创新链,提升中国制造业在GVC中的国际分工地位。此外,政府应根据技术创新和引进政策在不同制造业行业中的执行效果,有所侧重地制定和实施相关政策。  相似文献   
840.
以化学抑制法研究污水生物处理过程中N2O的释放源   总被引:1,自引:1,他引:1       下载免费PDF全文
采用化学抑制法,研究了不同曝气量下污水生物处理过程中N2O的释放源.结果表明,缺氧段中, N2O的主要释放源为硝酸盐异化成氨反应,而反硝化反应消耗N2O.好氧段中N2O释放源受曝气量的影响很大,当曝气量适中时(65L/h), N2O释放源主要为硝化细菌反硝化作用;而当曝气量偏高(105L/h)或偏低(25L/h)时,同步硝化-反硝化反应是主要的N2O释放源.同时硝化细菌反硝化反应也能够产生少量N2O.  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