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   1921篇
  免费   80篇
  国内免费   649篇
安全科学   141篇
废物处理   103篇
环保管理   140篇
综合类   1076篇
基础理论   311篇
污染及防治   568篇
评价与监测   78篇
社会与环境   107篇
灾害及防治   126篇
  2023年   22篇
  2022年   82篇
  2021年   71篇
  2020年   68篇
  2019年   67篇
  2018年   81篇
  2017年   89篇
  2016年   90篇
  2015年   112篇
  2014年   144篇
  2013年   180篇
  2012年   115篇
  2011年   140篇
  2010年   109篇
  2009年   101篇
  2008年   124篇
  2007年   130篇
  2006年   85篇
  2005年   86篇
  2004年   66篇
  2003年   103篇
  2002年   103篇
  2001年   80篇
  2000年   83篇
  1999年   58篇
  1998年   46篇
  1997年   59篇
  1996年   31篇
  1995年   29篇
  1994年   28篇
  1993年   21篇
  1992年   16篇
  1991年   9篇
  1990年   8篇
  1989年   4篇
  1988年   5篇
  1987年   3篇
  1983年   1篇
  1981年   1篇
排序方式: 共有2650条查询结果,搜索用时 312 毫秒
171.
随着电子信息产业的高速发展和人民生活水平的不断提高,电子废弃物的数量也不断增长,成为21世纪增长最快的固体废弃物。从我国电子废弃物的回收利用现状入手进行分析,提出建设一套专业回收利用体系,形成以城市社区回收点为基础,中转交投中心为纽带,资源循环利用为目的,点面结合、三位一体的电子废弃物回收利用体系,逐步提高回收、集散、循环利用能力,促进行业健康、有序发展。  相似文献   
172.
A set of toxic metals, i.e. As, Hg, Pb, Cd, Cu, Zn, Ni and Cr, in urban and suburban SDSs were investigated comparatively in the biggest metropolitan area of China, Shanghai. Results showed that all of the metals except As were accumulated greatly, much higher than background values. Geo-accumulation index indicated that metal contamination in urban SDSs was generally heavier than that in suburban SDSs. Potential ecological risk index demonstrated that overall risks caused by metals were considerable. Cd contributed 52% to the overall risk. Multivariate statistical analysis revealed that in urban SDSs, Zn, Ni, Cd, Pb, Cu and Cr were related to traffic and industry; coal combustion led to elevated levels of Hg; soil parent materials controlled As contents. In suburban SDSs, Pb, Cu, As and Cd largely originated from traffic pollution; Zn, Ni and Cr were associated with industrial contaminants; Hg was mainly from domestic solid waste.  相似文献   
173.
Based on environmental monitoring data in 93 major cities and meteorological records at 398 weather stations in China from 1981 to 2007, total suspended particle (TSP) concentration, the intensity of dustfall, and sand and dust storm frequency (Fd) were analysed. During the past 27 years, the annual average TSP concentration (CTSP) in 93 cities was 402 μg m?3. Annual average CTSP decreased from the north to the south and from inland to the coast areas with a peak value of 628.8 μg m?3 in Lanzhou. In the 1980s, 1990s and 2000s, annual average CTSP was 628.7, 319.2, and 250.1 μg m?3, respectively. Annual average intensity of dustfall (Id) was 240.5 t km?2 a?1, decreased from northern to southern China and from inland to the coast areas with the maximum value of 717.2 t km?2 a?1 in Baotou. In the 1980s, 1990s and 2000s, annual average Id was 334.8, 220.9, 146 t km?2 a?1 respectively. Annual average Id in the Loess Plateau region was commonly higher than 200 t km?2 a?1. The annual average Fd decreased from arid regions in northwestern China to humid areas in southeastern China with two sand and sand storm centers existing in Xinjiang Taklamakan Desert and western Inner Mongolia. The annual average Fd in the 1980s, 1990s, 2000s was 16, 8, 6 days respectively, decreased steadily from 18 days in 1981–5 days in 2007. Annual average Id had a positive linear relation to annual average CTSP (R2 = 0.96). Annual average Fd had a positive relation with annual average CTSP (R2 = 0.97) as well as annual average Id (R2 = 0.94). TSP was the chief pollutant influencing Air Pollution Index (API) in northern China in spring and winter seasons. Sand and dust storm might be a major factor affecting the temporal variability and spatial distribution of TSP and dustfall in China.  相似文献   
174.
颗粒物对无电压作用下离子交换膜分离去除铜离子的影响   总被引:1,自引:1,他引:0  
在无外加电压条件下研究了颗粒物对阳离子交换膜分离去除铜离子效果的影响。选用硅酸、二氧化硅、氧化铝和水杨酸等4种物质作为颗粒物分别进行实验,其添加量均为50 mg/L。Cu2+及其补偿离子K+的浓度分别为0.0787mmol/L(5 mg/L)和0.787 mmol/L,水温为25±1℃,搅拌强度为600 r/min,水力停留时间为12 h。在所述实验条件下运行96 h后,水中无颗粒物干扰时,铜离子去除率为84%;水中存在带负电荷颗粒物(硅酸)和不带电荷颗粒物(二氧化硅和氧化铝)时,铜离子去除率略为下降至81%;而当水中存在带正电荷颗粒物(水杨酸)时,铜离子的去除率进一步下降为79%。研究结果表明带正电荷颗粒物对铜离子的交换去除影响较带负电荷或不带电荷颗粒物大,因为带正电荷颗粒物更易迁移至阳离子交换膜表面甚至进入膜内,并与膜表或膜内离子交换基团结合,从而导致铜离子交换去除明显下降。  相似文献   
175.
脱硫灰与钾矿石复合生产钾钙硅镁硫肥料研究   总被引:1,自引:0,他引:1  
石林 《环境工程学报》2010,4(10):2339-2342
对脱硫灰与钾矿石复合生产钾钙硅镁硫肥的研究意义、反应原理、生产流程、环境安全性能以及施肥方法等进行了介绍和评估,并对其应用前景进行了展望。研究结果表明:利用脱硫灰与钾矿石复合生产钾钙硅镁硫肥在理论上可行;生产出的产品中硫酸钾的含量达10.34%~12.0%,枸溶氧化钙19.06%~32.28%,枸溶二氧化硅10.98%~14.46%,枸溶氧化镁1.46%~1.82%。产品的pH值从原脱硫灰的10.65下降到9.60。重金属含量低于农用粉煤灰国家标准,生产过程中不会产生SO2等有害气体污染。肥料的生产成本低于350元/t,该肥料不但可以增加土壤中钾、钙、硅、镁和硫等中微量元素的含量,而且可以提高或改善农作物的产量和品质。达到变废为宝,促进循环经济发展之目的。  相似文献   
176.
Clays such as kaolin, bentonite and zeolite were evaluated as support material for nanoscale zero-valent iron (nZVI) to simultaneously remove Cu2+ and Zn2+ from aqueous solution. Of the three supported nZVIs, bentonite-supported nZVI (B-nZVI) was most effective in the simultaneous removal of Cu2+ and Zn2+ from a aqueous solution containing a 100 mg/l of Cu2+ and Zn2+, where 92.9 % Cu2+ and 58.3 % Zn2+ were removed. Scanning electronic microscope (SEM) revealed that the aggregation of nZVI decreased as the proportion of bentonite increased due to the good dispersion of nZVI, while energy dispersive spectroscopy (EDS) demonstrated the deposition of copper and zinc on B-nZVI after B-nZVI reacted with Cu2+ and Zn2+. A kinetics study indicated that removing Cu2+ and Zn2+ with B-nZVI accorded with the pseudo first-order model. These suggest that simultaneous adsorption of Cu2+and Zn2+ on bentonite and the degradation of Cu2+and Zn2+ by nZVI on the bentonite. However, Cu2+ removal by B-nZVI was reduced rather than adsorption, while Zn2+ removal was main adsorption. Finally, Cu2+, Zn2+, Ni2+, Pb2+ and total Cr from various wastewaters were removed by B-nZVI, and reusability of B-nZVI with different treatment was tested, which demonstrates that B-nZVI is a potential material for the removal of heavy metals from wastewaters.  相似文献   
177.
In densely populated countries like China, clean water is one of the most challenging issues of prospective politics and environmental planning. Water pollution and eutrophication by excessive input of nitrogen and phosphorous from nonpoint sources is mostly linked to soil erosion from agricultural land. In order to prevent such water pollution by diffuse matter fluxes, knowledge about the extent of soil loss and the spatial distribution of hot spots of soil erosion is essential. In remote areas such as the mountainous regions of the upper and middle reaches of the Yangtze River, rainfall data are scarce. Since rainfall erosivity is one of the key factors in soil erosion modeling, e.g., expressed as R factor in the Revised Universal Soil Loss Equation model, a methodology is needed to spatially determine rainfall erosivity. Our study aims at the approximation and spatial regionalization of rainfall erosivity from sparse data in the large (3,200 km2) and strongly mountainous catchment of the Xiangxi River, a first order tributary to the Yangtze River close to the Three Gorges Dam. As data on rainfall were only obtainable in daily records for one climate station in the central part of the catchment and five stations in its surrounding area, we approximated rainfall erosivity as R factors using regression analysis combined with elevation bands derived from a digital elevation model. The mean annual R factor (R a) amounts for approximately 5,222 MJ?mm?ha?1?h?1?a?1. With increasing altitudes, R a rises up to maximum 7,547 MJ?mm ha?1?h?1 a?1 at an altitude of 3,078 m a.s.l. At the outlet of the Xiangxi catchment erosivity is at minimum with approximate R a?=?1,986 MJ?mm?ha?1?h?1?a?1. The comparison of our results with R factors from high-resolution measurements at comparable study sites close to the Xiangxi catchment shows good consistance and allows us to calculate grid-based R a as input for a spatially high-resolution and area-specific assessment of soil erosion risk.  相似文献   
178.
179.
Liang P  Shao DD  Wu SC  Shi JB  Sun XL  Wu FY  Lo SC  Wang WX  Wong MH 《Chemosphere》2011,82(7):1038-1043
To study the influence of mariculture on mercury (Hg) speciation and distribution in sediments and cultured fish around Hong Kong and adjacent mainland China waters, sediment samples were collected from six mariculture sites and the corresponding reference sites, 200-300 m away from the mariculture sites. Mariculture activities increased total mercury, organic matter, carbon, nitrogen and sulfur concentrations in the surface sediments underneath mariculture sites, possibly due to the accumulation of unconsumed fish feed and fish excretion. However, methylmercury (MeHg) concentrations and the ratio of MeHg to THg (% MeHg) in sediments underneath mariculture sites were lower than the corresponding reference sites. The % MeHg in sediments was negatively correlated (r = −0.579, p < 0.05) with organic matter (OM) content among all sites, indicating that OM may have inhibited Hg methylation in surface sediments. Three mariculture fish species were collected from each mariculture site, including red snapper (Lutjanus campechanus), orange-spotted grouper (Epinephelus coioides) and snubnose pompano (Trachinotus blochii). The average MeHg concentration in fish muscle was 75 μg kg−1 (wet weight), and the dietary intake of MeHg through fish consumption for Hong Kong residents was 0.37 μg kg−1 week−1, which was lower than the corresponding WHO limits (500 μg kg−1 and 1.6 μg kg−1 week−1).  相似文献   
180.
A2O工艺好氧末段溶解氧变化对脱氮除磷影响   总被引:3,自引:0,他引:3  
采用连续流A2O工艺处理实际的生活污水,研究好氧末段在不同溶解氧(DO)浓度条件下对污泥沉降性能、系统脱氮除磷的影响,同时考察了DO对污泥硝化活性、厌氧释磷速率和反硝化脱氮速率的影响.结果表明,随着末段溶解氧的提高,污泥容积指数SVI从140降至100左右,后又升高到120~170;系统的硝化效果提高,氨氮的去除率从6...  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