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   9459篇
  免费   913篇
  国内免费   2404篇
安全科学   516篇
废物处理   185篇
环保管理   1837篇
综合类   6830篇
基础理论   1089篇
环境理论   6篇
污染及防治   746篇
评价与监测   1071篇
社会与环境   403篇
灾害及防治   93篇
  2024年   38篇
  2023年   210篇
  2022年   303篇
  2021年   401篇
  2020年   404篇
  2019年   343篇
  2018年   282篇
  2017年   381篇
  2016年   397篇
  2015年   492篇
  2014年   498篇
  2013年   683篇
  2012年   640篇
  2011年   723篇
  2010年   589篇
  2009年   577篇
  2008年   473篇
  2007年   660篇
  2006年   653篇
  2005年   479篇
  2004年   437篇
  2003年   478篇
  2002年   407篇
  2001年   375篇
  2000年   351篇
  1999年   268篇
  1998年   196篇
  1997年   181篇
  1996年   161篇
  1995年   117篇
  1994年   114篇
  1993年   77篇
  1992年   75篇
  1991年   59篇
  1990年   40篇
  1989年   18篇
  1988年   13篇
  1987年   28篇
  1986年   15篇
  1985年   11篇
  1984年   6篇
  1982年   15篇
  1981年   18篇
  1980年   14篇
  1979年   10篇
  1978年   16篇
  1977年   5篇
  1973年   8篇
  1972年   9篇
  1971年   12篇
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
991.
排污收费政策失灵分析   总被引:1,自引:0,他引:1  
在市场经济体制下,经常会出现政策失灵。本文首先介绍了政策失灵的基本理论,然后对我国的排污收费政策失灵进行了深入分析,最后提出了完善我国排污收费政策的对策。  相似文献   
992.
Trace and minor element concentrations differ in animal tissues as the result of the surrounding environment (feeding plants, soil contaminated with food and drinking water) and animal absorption of these elements. Concentrations of Ag, Au, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, and Zn were determined from different tissues of camel (inter-costal, scapula, sirloin, flank, front knuckle and front limb) from the semi-arid areas of the Aswan desert (Wadi El-Allaqi) and from Aswan city, Egypt. The study included an assessment of these same elements in the desert and city plants used as food by the camels and in soils from the study areas. The results reveal that camel tissues from the desert areas exhibited higher concentrations of Na, Mg, K, Au, Ag, Cu, Co and Zn than in those of the city camels. These higher levels of element are because of the high concentrations of the same elements in the desert plants and soil of the desert area. This, in turn, depends upon the geological formation differences between the desert area and the city area. Camel tissues appear to concentrate high levels of Mn, Ni, Co and Mg in the scapula while flank portions concentrate high levels of Mg and K. The levels of elements in the camel tissues under study were within the recommended safety baseline levels for camel health and human use, as well as within the appropriate limits in the desert and city plants for camel use.  相似文献   
993.
本文论述了城市汽车空气污染研究的目标、基本方法及城市汽车污染控制区的划分原则和方法.汽车类型流动源采用整个控制区平均浓度作为分析对比的基础不合适,应该专门研究确定基准控制点.为了合理选择确定控制计算点,提出3种方法:峰值法、核心区和重点控制区法、9点平均法.9点平均法可以有效增加各类污染源的敏感点,同时又可避免增加该点位影响过大的缺陷.这种方法在其他类型大气污染源控制中也能发挥作用.  相似文献   
994.
垃圾填埋二次污染的危害与防治   总被引:18,自引:0,他引:18  
介绍了垃圾卫生填埋中二次污染的危害,指出垃圾卫生填埋场建设和填埋操作中为防止填埋释放物对周围环境的二次污染所应采取的防渗、收集、处理和利用等措施,探讨了在垃圾卫生填埋场建设和填埋操作中应注意的问题及应着重考虑的方面.  相似文献   
995.
ABSTRACT: To measure crop evapotranspiration, a large double tank, electronic weighting lysimeter system was designed and installed at the Shahid Bahonar University farm, Kerman, Iran. The system was installed in a 50 m2 underground building. It includes two tanks of 3.00 m in diameter and 1.75 m deep. The weighing mechanism for each tank is a set of three compression strain gage load cells, which are fixed on 1.20 m height column above the floor. According to the specification of the load cells, the maximum possible weighing error may be about 0.01 percent of total mass, which is equivalent to 0.28 mm of water, but the measured error was equal to 1 kg mass, which is equivalent to 0.14 mm of water. The load cell data from each tank and the on‐site environmental data (temperature, humidity, and wind velocity and direction) are automatically recorded and saved in a personal computer hard disk for further use and analysis.  相似文献   
996.
开发研制绿色化学产品   总被引:1,自引:0,他引:1  
叙述绿色化学是一门从源头上彻底阻止污染的化学,简介了几种绿色化学产品及研究开发的进展。  相似文献   
997.
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   
998.
论地膜污染与防治对策   总被引:17,自引:0,他引:17  
随着地膜覆盖栽培年限的延长,由于残膜回收率低,土壤中残膜量逐步增加,造成地膜污染。通过分析地膜污染对环境和农作物产生的危害,对回收残膜存在的问题,总结出了防治地膜污染的对策与措施。  相似文献   
999.
本文指出成都市农业环境受工农业生产发展所造成的污染和对生态环境的破坏都较严重。为此,提出保护农业环境的关键在于:建立健全农业环境管理机构,健全法制,加强农业环境意识及促进农业生态系统的良性循环,加速生态农业建设,尽量减小农业自身污染。  相似文献   
1000.
ABSTRACT: The detrimental impacts of acid rain have become widely publicized, but effective and equitable methods to mitigate the acid rain problem remain to be found. This paper focuses on conflicts involved in allocation of the total emission loads to be reduced to respective pollution sources of acid rain, and proposes a game-theory approach to the resolution of the conflict. With an example abstracted from a hypothetical case study in the United States of America and Canada, a systematic analysis is performed and policy implications of the results examined to assess the applicability of the proposed model.  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