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   4218篇
  免费   345篇
  国内免费   399篇
安全科学   1026篇
废物处理   50篇
环保管理   605篇
综合类   1871篇
基础理论   386篇
环境理论   1篇
污染及防治   196篇
评价与监测   293篇
社会与环境   306篇
灾害及防治   228篇
  2024年   20篇
  2023年   76篇
  2022年   112篇
  2021年   158篇
  2020年   159篇
  2019年   113篇
  2018年   90篇
  2017年   174篇
  2016年   204篇
  2015年   193篇
  2014年   221篇
  2013年   259篇
  2012年   366篇
  2011年   417篇
  2010年   302篇
  2009年   246篇
  2008年   177篇
  2007年   249篇
  2006年   257篇
  2005年   198篇
  2004年   149篇
  2003年   136篇
  2002年   97篇
  2001年   85篇
  2000年   76篇
  1999年   59篇
  1998年   53篇
  1997年   41篇
  1996年   50篇
  1995年   39篇
  1994年   25篇
  1993年   33篇
  1992年   27篇
  1991年   17篇
  1990年   6篇
  1989年   10篇
  1988年   7篇
  1987年   5篇
  1986年   4篇
  1985年   4篇
  1983年   3篇
  1981年   5篇
  1980年   5篇
  1979年   4篇
  1978年   3篇
  1977年   3篇
  1976年   3篇
  1974年   3篇
  1973年   5篇
  1972年   5篇
排序方式: 共有4962条查询结果,搜索用时 15 毫秒
71.
One of the primary challenges in resource and environmental planning is successful implementation of plans. Plan implementation is a complex process influenced by many factors. This study identifies 19 criteria affecting implementation success and tests the impact of these criteria through a case study of collaborative plan implementation in British Columbia, Canada. The significance of criteria and degree to which they are met is assessed by a survey of senior officials responsible for plan implementation. An implementation evaluation index (IEI) is constructed to assess the quality of plan implementation systems and best practices for effective implementation are identified.  相似文献   
72.
王秀芳  刘国荣  朱珈 《环境技术》2008,26(1):22-24,45
本文简述电气领域如何评定测量不确定度过程,并结合CNAS T0346低温试验能力验证计划,识别和具体分析低温试验中各测量不确定度的来源,对各种影响因素进行评价,论述人、机、料、法、环、测各环节对测量结果的影响,给出了低温试验测量结果不确定度的评估过程。  相似文献   
73.
通过对近年来的城市燃气管道事故抢险统计数据的分析与研究,管道事故抢险方案的选择存在着很大的主观性和片面性.为了克服应急抢修方案的种种局限,笔者应用模糊综合评判方法建立了城市燃气管道事故应急抢修方案评价选择模型;考虑可靠性、抢修时间、事故损失、抢险费用、社会影响及政治影响等6类影响因素来评判抢修方案的优劣,可以科学合理地选择最佳的管道事故应急抢修方案,达到经济合理、快速可靠的目的;实例验证,评判模型对城市燃气管道事故抢险具有重要的现实意义和参考价值.  相似文献   
74.
The strong fluctuating component in the measured concentration time series of a dispersing gaseous pollutant in the atmospheric boundary layer, and the hazard level associated to short-term concentration levels, demonstrate the necessity of calculating the magnitude of turbulent fluctuations of concentration using computational simulation models. Moreover the computation of concentration fluctuations in cases of dispersion in realistic situations, such as built-up areas or street canyons, is of special practical interest for hazard assessment purposes. In this paper, the formulation and evaluation of a model for concentration fluctuations, based on a transport equation, are presented. The model is applicable in cases of complex geometry. It is included in the framework of a computational code, developed for simulating the dispersion of buoyant pollutants over complex geometries. The experimental data used for the model evaluation concerned the dispersion of a passive gas in a street canyon between 4 identical rectangular buildings performed in a wind tunnel. The experimental concentration fluctuations data have been derived from measured high frequency concentrations. The concentration fluctuations model is evaluated by comparing the model's predictions with the observations in the form of scatter plots, quantile-quantile plots, contour plots and statistical indices as the fractional bias, the geometrical mean variance and the factor-of-two percentage. From the above comparisons it is concluded that the overall model performance in the present complex geometry case is satisfactory. The discrepancies between model predictions and observations are attributed to inaccuracies in prescribing the actual wind tunnel boundary conditions to the computational code.  相似文献   
75.
太湖地区“禁磷”措施的效果及在富营养化控制中的作用   总被引:2,自引:0,他引:2  
通过太湖地区采取“禁磷”措施前后城市生活污水、主要入湖河水和湖体水域中磷浓度与富营养化指数变化的分析 ,证实“禁磷”措施对降低居民生活污水中磷浓度的作用较为明显 ,降幅为 2 4 %左右 ,但对入湖河道和湖体水域中磷浓度与水体富营养化的影响则不明显。表明太湖富营养化的改善 ,除了实施“禁磷”措施外 ,尚需结合流域内其它污染治理措施 ,进行综合治理 ,才能取得较好的效果。  相似文献   
76.
生态补水对玄武湖水质的影响   总被引:1,自引:0,他引:1  
分析南京玄武湖1997年-2010年的水质变化,以及生态补水与玄武湖水质变化的关系。结果表明,玄武湖于1998年实施生态补水,随着生态补水的持续运行和生态补水量的不断增加,玄武湖水质得以显著改善,其水质类别由生态补水前的劣V类水体转为V类水体,并接近于Ⅳ类水体,富营养化程度由重度富营养化水平转为轻度富营养化水平。目前玄武湖主要营养物质来源于生态补水,相关性分析显示各湖区TN浓度与生态补水中TN浓度呈显著相关关系。  相似文献   
77.
This paper presents result from an economic and technical point of view evaluation study, which has sought to establish the potential for replacing well-water that is currently used at the Piaggio industrial plant in Pontedera with recycled wastewater. The study is based upon a pilot wastewater treatment plant, which has been used to test wastewater treatment processes and to compare with achieved quality of recycled waters with that of water drawn on-site from physical/chemical pre-treatment and end with a reverse osmosis and air stripping stage. However, after the physical/chemical pre-treatment, the first option uses oxidation with ozone followed by activated carbon filtration, whereas the second method uses ultrafiltration. The first method is more effective at reducing chemical oxygen demand (COD) whereas the second method is more effective in removing bacteria. Nonetheless, both methods deliver water for re-use of a quality comparable with or better than that of well-water. In principle, the reverse osmosis permeate from either process could be re-used in all production phases at the industrial plant. However, the method base upon oxidation with ozone followed by activated carbon filtration is preferred, because, the process is simpler and continuous. The economic analysis of this process gives an estimated cost of Euro 0.55 per m3 for treated water. This compares favorably with other treatment processes and with the cost of other forms of water supply, which are projected to increase in any case.  相似文献   
78.
ABSTRACT: We evaluated the effectiveness of watershed‐scale implementations of best‐management practices (BMPs) for improving habitat and fish attributes in two coldwater stream systems in Wisconsin. We sampled physical habitat, water temperature, and fish communities in multiple paired treatment and reference streams before and after upland (barnyard runoff controls, manure storage, contour plowing, reduced tillage) and riparian (stream bank fencing, sloping, limited rip‐rapping) BMP installation in the treatment subwatersheds. In Spring Creek, BMPs significantly improved overall stream habitat quality, bank stability, instream cover for fish, abundance of cool‐ and coldwater fishes, and abundance of all fishes. Improvements were most pronounced at sites with riparian BMPs. Water temperatures were consistently cold enough to support coldwater fishes such as trout (Salmonidae) and sculpins (Cottidae) even before BMP installation. We observed the first‐time occurrence of naturally reproduced brown trout (Salmo trutta) in Spring Creek, indicating that the stream condition had been improved to be able to partially sustain a trout population. In Eagle Creek and its tributary Joos Creek, limited riparian BMPs led to localized gains in overall habitat quality, bank stability, and water depth. However, because few upland BMPs were installed in the subwatershed there were no improvements in water temperature or the quality of the fish community. Temperatures remained marginal for coldwater fish throughout the study. Our results demonstrate that riparian BMPs can improve habitat conditions in Wisconsin streams, but cannot restore coldwater fish communities if there is insufficient upland BMP implementation. Our approach of studying multiple paired treatment and reference streams before and after BMP implementation proved effective in detecting the response of stream ecosystems to watershed management activities.  相似文献   
79.
构建了针对秦皇岛市的生态城市评价指标体系,采用多指标综合评价法,对2011年秦皇岛市城市生态化程度进行了评价。结果表明:秦皇岛市城市生态化综合指数为0.687,生态化程度为2级水平,经济持续发展子系统和资源能源节约子系统较为薄弱。根据评价结果,提出了大力发展循环经济、加强水污染治理、提高资源能源利用效率、加大生态建设力度等建议。  相似文献   
80.
汽车整车腐蚀试验主观评价方法的探讨   总被引:1,自引:0,他引:1  
本本文介绍汽车整车道路腐蚀试验、整车腐蚀试验中评价方法的选择,主要探讨整车腐蚀评价体系中主观评价的几大要素。  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