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   297篇
  免费   48篇
  国内免费   143篇
安全科学   11篇
废物处理   18篇
环保管理   27篇
综合类   202篇
基础理论   96篇
污染及防治   95篇
评价与监测   10篇
社会与环境   14篇
灾害及防治   15篇
  2023年   5篇
  2022年   19篇
  2021年   27篇
  2020年   28篇
  2019年   13篇
  2018年   18篇
  2017年   25篇
  2016年   28篇
  2015年   23篇
  2014年   27篇
  2013年   24篇
  2012年   30篇
  2011年   30篇
  2010年   17篇
  2009年   34篇
  2008年   23篇
  2007年   23篇
  2006年   17篇
  2005年   13篇
  2004年   5篇
  2003年   10篇
  2002年   13篇
  2001年   10篇
  2000年   1篇
  1999年   4篇
  1998年   4篇
  1997年   3篇
  1996年   3篇
  1995年   4篇
  1994年   4篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
排序方式: 共有488条查询结果,搜索用时 15 毫秒
101.
实验探讨了添加碳源及投加反硝化细菌对低碳氮比景观水体生物脱氮的影响。结果表明,有机碳源及B.subtilis FS05均能显著促进实验水体的生物脱氮作用,实验水体在28℃静置72 h后,乙醇添加组的TN、氨氮、硝酸盐及亚硝酸盐的去除率分别达到了62.7%、67.0%、69.8%和29.4%,而同样条件下,B.subtilis FS05投加组的去除率分别达到了66.9%、73.4%、66.0%和82.2%。从水质变化趋势可以看出,投加B.subtilis FS05能在更短时间内完成生物脱氮过程,其中,硝酸盐和亚硝酸盐去除速率最快,分别仅需要18 h和12 h。  相似文献   
102.
微波-过氧乙酸联合作用处理剩余污泥的研究   总被引:1,自引:0,他引:1  
采用微波-过氧乙酸(PAA)联合作用处理剩余污泥,考察了微波辐照时间、微波功率、PAA投加量对剩余污泥分解效果的影响.同时以单独微波作用为对比,考察了微波-PAA联合作用下剩余污泥性质的变化.结果表明,当微波功率为600 W,PAA投加量为0.24 g/g(以干质量SS计)时,微波辐照60 s后剩余污泥分解率可达35%...  相似文献   
103.
The five central cities-Beijing,Tianjin,Shanghai,Guangzhou and Shenzhen-of the three most important strategic regions in China,namely Beijing-Tianjin-Hebei metropolitan region,the Yangtze River Delta and the Pearl River Delta,are taken as a comparative analysis on urban producer services’ competitiveness,especially focusing on the comparative advantages and disadvantages of producer services in Beijing.Firstly,based on an integrated indicator system including one objective hierarchy,four standard hierarchies and 35 indicator hierarchies,the study applies factor analysis model and analytic hierarchy process model reformed by entropy technology to measure the comprehensive competitiveness of producer services in the above five cities.Secondly,Beijing has comparative advantages of capital resource,industrial base,scientific research resource and market scale,since it takes the first place of the five cities in the comprehensive competitiveness of producer services,the competitiveness of industrial development,business environment and living environment,only inferior to Shanghai in the competitiveness of talent capital.Thirdly,Beijing has comparative disadvantages in the level of producer services development,urban innovation capability and living environment.Finally,five proposals are put forth to enhance the competitiveness of producer services in Beijing,namely perfecting the system of laws and statutes,supporting the development of industry association,implementing scientific development planning,introducing preferential fiscal and taxation policies and strengthening human capital reserve.  相似文献   
104.
扬州市城区地表水底泥重金属污染现状与风险评价   总被引:6,自引:0,他引:6  
对扬州市城区地表水底泥进行等距离布点采样.分析cd、Cu、Pb、Zn 4种重金属的含量,并应用潜在生态危害指数法对重金属潜在生态风险进行了评价.结果表明:4种重金属的潜在生态风险由高到低的顺序为Cd>Pb>Cu>Zn,其中Cd的潜在生态风险程度已达很强;扬州市城区地表水底泥重金属潜在生态风险程度为强.各条河流底泥重金属潜在生态风险程度由强到弱顺序为古运河>二道河>宝带河>小秦淮河>新城河>水院池塘(对照);从空间上看,扬州市城区东部的地表水底泥重金属潜在生态风险程度高于西部,北部高于南部.  相似文献   
105.
环糊精聚合物对苯胺的吸附和脱附性能研究   总被引:2,自引:1,他引:1  
以环氧氯丙烷为交联剂,合成和表征了β-环糊精聚合物(β-CDP),从动力学和热力学角度研究了β-CDP对苯胺的吸附性能。研究结果表明,β-CDP对水溶液中的苯胺具有一定的吸附量。用Langmuir, Freundlich和DubininRadushkevich(D-R)吸附等温式拟合了平衡等温数据,并计算出每个模型的参数。苯胺在β-CDP上的吸附符合D-R方程,吸附过程是热力学自发行为。在乙醇中,β-CDP的脱附能力很强,且可循环使用多次。  相似文献   
106.
聚硅酸锌铝的制备及其性能研究   总被引:1,自引:1,他引:0  
以硅酸钠、硫酸锌、硫酸铝为原料,通过共聚法制备了无机高分子絮凝剂聚硅酸锌铝(PSZAS),研究了Na2SiO3的摩尔浓度、活化时间、Al/Si、Zn/Si 配比及絮凝剂的投加量对絮凝效果的影响,用X-射线衍射(XRD)和电子扫描电镜(SEM)对该絮凝剂的结构及形貌进行了表征。结果表明:当硅酸钠的浓度为0.4 mol/L,硅酸活化时间为2 h,Si∶Al∶Zn=1∶1∶1.5,絮凝剂投加量为20 mL/L废水时,絮凝剂的电中和能力和吸附架桥能力最强,絮凝剂对含H-酸染料模拟废水的絮凝效果最好。  相似文献   
107.
Leachate was collected from an anaerobic lagoon at Shanghai Laogang refuse landfill, the largest landfill in China, and the sample was separated into six fractions using micro-filtration membranes, followed by ultra-filtration membranes. Several parameters of the samples were measured, including chemical oxygen demand (COD), total organic carbon (TOC), total solids (TS), pH, total phosphate (TP), total nitrogen (TN), fixed solids (FS), NH4+, orthophosphate, color, turbidity, and conductivity. These parameters were then quantitatively correlated with the molecular weight cutoff of the membrane used. Organic matter in the dissolved fraction (MW<1kDa) predominated in the leachate, accounting for 65% of TOC. Thermal infrared spectroscopy was used to characterize the filter residues. Asymmetric and symmetric stretching of methyl and methylene groups, and of functional groups containing nitrogen and oxygen atoms, were observed. In addition, the ability of two different samples to adsorb heavy metals was tested. Cu2+ was chosen as the representative heavy metal in this study, and the samples were soil; aged refuse, which had spent 8 years in a conventional sanitary landfill; and samples of soil and aged refuse treated for 48h with leachate in the ratio of 5g of sample per 50ml of leachate. Cu2+ uptake by the raw soil was approximately 4.60microg/g, while uptake by the leachate-contacted soil and leachate-contacted aged refuse were 5.66 and 5.11microg/g, respectively. These results show that the organic matter in the leachate enhanced the capacity of aqueous solutions to adsorb Cu2+.  相似文献   
108.
Wang X  Li Y  Dong D 《Chemosphere》2008,73(1):1-6
The sorption characteristics of pentachlorophenol (PCP) in the surficial sediments were investigated using a selective extraction procedure. The results show that the Gamma(max) of PCP sorption decreased from 1.60mumolg(-1) to 0.69mumolg(-1) by approximately 60% after selective removal of organic materials from the sediments. The sorption of PCP in the sediments after selective removal of Mn oxides increased nearly up to 600% (from 1.60mumolg(-1) to 11.11mumolg(-1)) and, to a less degree, the PCP sorption in the sediments after simultaneous removal of Fe/Mn oxides (Gamma(max)=3.53mumolg(-1)). The analysis of the data using an additional model indicates that the contribution of Mn oxides to PCP sorption was negative, and Fe oxides and organic materials both have greater potential for sorption of PCP with less contribution from residues including Mn and Fe oxides in the residual fractions determined by a sequential extraction procedure and clay and silicate minerals. The differences in the decreased degrees of PCP sorption with increasing of Cu suggest that competition between Cu and PCP for sorption sites mainly takes place on Fe oxides.  相似文献   
109.
通过把起相转移作用的聚乙二醇链固载在硅胶上(SiO2-PEG600),再将聚乙稀吡咯烷酮(PVP)络合双金属Pd-Cu(PVP-PdCl2-CuCl2)后负载其中,制成一种新型双负载双金属水相脱卤催化剂PVP-PdCl2-CuCl2/SiO2-PEG600。以甲酸钠为氢转移试制,在水相中催化有机卤化物脱卤,研究结果表明:反应温度为800℃,Pd∶Cu=2∶1(摩尔比),反应介质pH≈11.7左右时,该催化剂对芳香氯化物及α-氯代酮、酯具有良好的催化脱氯和重复使用性能。  相似文献   
110.
Annual normalized difference vegetation index (NDVI) and chlorophyll-a (Chl-a) concentration are the most important large-scale indicators of terrestrial and oceanic ecosystem net primary productivity. In this paper, the Sea-viewing Wide Field-of-view Sensor level 3 standard mapped image annual products from 1998 to 2009 are used to study the spatial–temporal characters of terrestrial NDVI and oceanic Chl-a concentration on two sides of the coastline of China by using the methods of mean value (M), coefficient of variation (CV), the slope of unary linear regression model (Slope), and the Hurst index (H). In detail, we researched and analyzed the spatial–temporal dynamics, the longitudinal zonality and latitudinal zonality, the direction, intensity, and persistency of historical changes. The results showed that: (1) spatial patterns of M and CV between NDVI and Chl-a concentration from 1998 to 2009 were very different. The dynamic variation of terrestrial NDVI was much mild, while the variation of oceanic Chl-a concentration was relatively much larger; (2) distinct longitudinal zonality was found for Chl-a concentration and NDVI due to their hypersensitivity to the distance to shoreline, and strong latitudinal zonality existed for Chl-a concentration while terrestrial NDVI had a very weak latitudinal zonality; (3) overall, the NDVI showed a slight decreasing trend while the Chl-a concentration showed a significant increasing trend in the past 12 years, and both of them exhibit strong self-similarity and long-range dependence which indicates opposite future trends between land and ocean.  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