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   1322篇
  免费   124篇
  国内免费   489篇
安全科学   121篇
废物处理   78篇
环保管理   92篇
综合类   919篇
基础理论   161篇
环境理论   1篇
污染及防治   367篇
评价与监测   64篇
社会与环境   69篇
灾害及防治   63篇
  2024年   6篇
  2023年   40篇
  2022年   101篇
  2021年   73篇
  2020年   85篇
  2019年   44篇
  2018年   70篇
  2017年   79篇
  2016年   70篇
  2015年   83篇
  2014年   107篇
  2013年   143篇
  2012年   98篇
  2011年   93篇
  2010年   105篇
  2009年   72篇
  2008年   94篇
  2007年   65篇
  2006年   73篇
  2005年   45篇
  2004年   28篇
  2003年   30篇
  2002年   25篇
  2001年   28篇
  2000年   37篇
  1999年   47篇
  1998年   27篇
  1997年   25篇
  1996年   29篇
  1995年   24篇
  1994年   23篇
  1993年   17篇
  1992年   11篇
  1991年   15篇
  1990年   5篇
  1989年   5篇
  1988年   4篇
  1987年   3篇
  1986年   2篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
排序方式: 共有1935条查询结果,搜索用时 203 毫秒
991.
微生物燃料电池利用甘薯燃料乙醇废水产电的研究   总被引:3,自引:2,他引:1  
蔡小波  杨毅  孙彦平  张良  肖瑶  赵海 《环境科学》2010,31(10):2512-2517
利用空气阴极微生物燃料电池(MFC)处理甘薯燃料乙醇废水,以COD为5000mg/L的废水做底物,获得的最大电功率密度为334.1mW/m2,库仑效率(CE)为10.1%,COD去除率为92.2%.实验进一步考察了磷酸缓冲液(PBS)浓度和废水浓度对MFC产电性能的影响.PBS含量从50mmol/L增加到200mmol/L,MFC输出的最大电功率密度提高了33.4%,CE增加26.0%,但PBS对废水的COD去除率影响不大.含50mmol/LPBS的废水COD从625mg/L增加到10000mg/L,COD去除率和MFC输出的最大电功率密度在废水浓度为5000mg/L处均获得最大值,但CE值有降低的趋势,从28.9%变化至10.3%.这些结果表明,MFC可以在处理甘薯燃料乙醇废水的同时获得电能;增大PBS浓度能提高MFC的产电性能;MFC输出的最大电功率密度随废水COD增加而增大,但废水浓度过高会引起酸化使MFC产电性能下降.  相似文献   
992.
选取了湖泊底泥、矿化垃圾、覆盖土和好氧污泥4种填埋场周边易得基质为分离源,采用驯化、传代培养、甲烷氧化能力及适应性等方法进行了适合于填埋场覆盖层应用的甲烷氧化菌的筛选研究.结果表明,从好氧污泥中分离得到的甲烷氧化菌较其它分离源得到的甲烷氧化菌具有更高的甲烷氧化活性(2461.29μg·h-1·g-1,以每g干污泥每小时氧化的CH4量(μg)计,下同)和甲烷氧化速率增幅(1045.56μg·h-1·g-1,以每g干污泥每小时氧化的CH4量(μg)计,下同),接种后能显著提高覆盖材料的甲烷氧化能力(p0.05),且不受CH4浓度的抑制.源自好氧污泥的甲烷氧化菌具有生长迟滞期短、生长速率高等特点,对填埋场的甲烷削减更具适应性,有利于工程扩大应用.  相似文献   
993.
广西罗城国家地质公园地质遗迹资源十分丰富,以典型壮美的喀斯特地貌景观和水体景观为主,辅以地质剖面遗迹景观和地质构造遗迹景观等.介绍了罗城地质公园内的地质遗迹类型及其分布,并从科学价值、科普价值、美学价值、旅游开发价值四个方面对其进行了综合评价.  相似文献   
994.
阐述了110千伏变电站噪声环境影响的现状,全面列举了变电站的主要噪声源并分析其分布规律及噪声影响特点.针对各类声源的特点,结合变电站设计、施工、运行维护三个主要阶段,全过程分析了常用的变电站噪声控制方案及其效果,重点关注了有源消声技术的应用和排风扇噪声影响的问题.对常用噪声控制方案的分析与研究,旨在寻求最经济、最有效的110千伏变电站噪声控制方案.  相似文献   
995.
低碳城镇化是新型城镇化建设的重要内容。本文从分析山西省城镇化特征入手,梳理了城镇化中的高碳问题,针对山西省的发展阶段和特征,提出发展低碳经济、实施低碳规划、推行绿色交通和建筑、倡导低碳生活等低碳城镇化的路径选择。  相似文献   
996.
A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis. Macrophyte biomass showed coincident growth trends with time, but different variation rates with nitrogen treatment. All plant growth indexes with nitrogen addition (N, NH4Cl 100, 200, 400 mg/kg, respectively) were lower than those of the control group. Four humiclike components, two autochthonous tryptophan-like components, and one autochthonous tyrosine-like component were identified using the parallel factor analysis model. The results suggested that the relative component changes of fluorescence in the colonized sediments were in direct relation to the change of root biomass with time. In the experiment, the root formation parameters of the plants studied were significantly affected by adding N in sediments, whichmay be related to the reason that the root growthwas affected byNaddition. Adding a low concentration of N to sediments can play a part in supplying nutrients to the plants. However, the intensive uptake of NH4+ may result in an increase in the intracellular concentration of ammonia, which is highly toxic to the plant cells. Hence, our experiment results manifested that organic matter cycling in the macrophyte-dominated sediment was influenced by nitrogen enrichment through influencing vegetation and relevant microbial activity.  相似文献   
997.
Marine aerosols over the East China Seas are heavily polluted by continental sources. During the Chinese Comprehensive Ocean Experiment in November 2012, size and mass spectra of individual atmospheric particles in the size range from 0.2 to 2.0 μm weremeasured onboardby a single particle aerosol mass spectrometer (SPAMS). The average hourly particle number (PN) was around 4560 ± 3240 in the South Yellow Sea (SYS), 2900 ± 3970 in the North Yellow Sea (NYS), and 1700 ± 2220 in the Bohai Sea (BS). PN in NYS and BS varied greatly over 3 orders of magnitude, while that in SYS varied slightly. The size distributions were fitted with two log-normal modes. Accumulation mode dominated in NYS and BS, especially during episodic periods. Coarse mode particles played an important role in SYS. Particles were classified using an adaptive resonance theory based neural network algorithm (ART-2a). Six particle types were identified with secondary-containing, aged sea-salt, soot-like, biomass burning, fresh sea-salt, and lead-containing particles accounting for 32%, 21%, 18%, 16%, 4%, and 3% of total PN, respectively. Aerosols in BS were relatively enriched in particles from anthropogenic sources compared to SYS, probably due to emissions from more developed upwind regions and indicating stronger influence of continental outflowonmarine environment. Variation of source types dependedmainly on origins of transported air masses. This study examined rapid changes in PN, size distribution and source types of fine particles in marine atmospheres. It also demonstrated the effectiveness of high-time-resolution source apportionment by ART-2a.  相似文献   
998.
A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis.Macrophyte biomass showed coincident growth trends with time, but different variation rates with nitrogen treatment. All plant growth indexes with nitrogen addition(N, NH4Cl100, 200, 400 mg/kg, respectively) were lower than those of the control group. Four humiclike components, two autochthonous tryptophan-like components, and one autochthonous tyrosine-like component were identified using the parallel factor analysis model. The results suggested that the relative component changes of fluorescence in the colonized sediments were in direct relation to the change of root biomass with time. In the experiment, the root formation parameters of the plants studied were significantly affected by adding N in sediments, which may be related to the reason that the root growth was affected by N addition.Adding a low concentration of N to sediments can play a part in supplying nutrients to the plants. However, the intensive uptake of NH4+may result in an increase in the intracellular concentration of ammonia, which is highly toxic to the plant cells. Hence, our experiment results manifested that organic matter cycling in the macrophyte-dominated sediment was influenced by nitrogen enrichment through influencing vegetation and relevant microbial activity.  相似文献   
999.
针对毒死蜱中间体生产的化工废水有机物浓度高、生物抑制性强的特点,以实际生产废水为研究对象,基于响应曲面法,进行了超声/Fenton法降解有机物效能研究与运行参数的优化.结果表明:1通过单因素试验确定响应曲面设计的自变量中心点为H2O2投加量0.5 mol/L、Fe2+投加量0.93 g/L、反应时间90 min.2采用Box-Behnken试验设计,建立了以H2O2及Fe2+投加量、反应时间为自变量的回归模型,经方差分析,模型显著(P0.000 1);对有机物去除率影响最大的因素为Fe2+投加量,其与反应时间的交互作用显著.3最优工况为H2O2投加量0.7 mol/L、Fe2+投加量1.36 g/L、反应时间96 min,该条件下模型预测CODCr去除率为96.63%,试验值与模型预测值的相对误差为1.36%,出水水质指标远低于GB 8978—1996《污水综合排放标准》三级标准,ρ(BOD5)/ρ(CODCr)从0.09升至0.22,CODCr单位去除负荷的H2O2及Fe2+用量相对较低,分别为0.14 mmol/mg和0.28 mg/mg.研究显示,采用超声/Fenton法处理高浓度难降解有机废水可有效提高CODCr去除率及其可生化性.  相似文献   
1000.
针对孤立电力系统的特点及其在线监测方面存在的问题,基于TCP/IP协议的光纤局域网接口技术,运用C++和汇编语言,依托100/1 000 Mbps以太网通讯技术,采用分层分布式结构,设计了孤立电网综合故障诊断系统。实现孤立电网设备的在线状态监测、电气量动态记录、故障预报、故障分析等功能。结果表明:该系统通过监测系统负荷变化、谐波含量、频率变化,有效解决了孤立电网的监测和电能质量问题,在孤立电网发生故障时,可迅速采取有效措施,减小孤立电网故障对主网的冲击,避免设备损坏,确保了电力系统运行的稳定性。  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