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   861篇
  免费   53篇
  国内免费   98篇
安全科学   213篇
废物处理   17篇
环保管理   108篇
综合类   417篇
基础理论   117篇
污染及防治   28篇
评价与监测   52篇
社会与环境   54篇
灾害及防治   6篇
  2024年   1篇
  2023年   10篇
  2022年   16篇
  2021年   45篇
  2020年   43篇
  2019年   23篇
  2018年   9篇
  2017年   25篇
  2016年   26篇
  2015年   61篇
  2014年   61篇
  2013年   52篇
  2012年   43篇
  2011年   72篇
  2010年   43篇
  2009年   59篇
  2008年   47篇
  2007年   45篇
  2006年   54篇
  2005年   60篇
  2004年   30篇
  2003年   24篇
  2002年   22篇
  2001年   26篇
  2000年   23篇
  1999年   16篇
  1998年   22篇
  1997年   10篇
  1996年   11篇
  1995年   9篇
  1994年   3篇
  1993年   4篇
  1992年   4篇
  1991年   5篇
  1990年   3篇
  1988年   1篇
  1987年   1篇
  1981年   2篇
  1973年   1篇
排序方式: 共有1012条查询结果,搜索用时 31 毫秒
901.
The relatively scarcity of flat or moderately sloping land in Central Appalachia make reclaimed surface mined lands attractive for agricultural uses. A reclaimed surface coal mine in southern West Virginia was placed under grazing management during the 1984 and 1985 growing seasons. Discharge was collected from summer-grazed watersheds of about 2.8 ha and 8.9 ha and analyzed, by the membrane-filtration method, for fecal coliforms (FC). Prior to grazing, in 1984, FC counts were < 20/100 ml. During the grazing season, FC ranged from <0/100 ml to> 1000/100 ml in 1984 and from 0/100 ml to > 2500/100 ml in 1985. FC counts remained high during warm periods for several months after grazing ceased. It was concluded that the bacteriological quality of receiving streams was impacted by grazing the reclaimed area and recommended standards for point sources were often exceeded; however, the FC counts did not appear to be any greater than what would have been expected from grazed, undisturbed areas. Reclaimed surface mine areas in Appalachia have the potential to be a valuable “flat land” resource and grazing appears to be an alternative post mine land use that affects bacteriological water quality in a similar manner as “natural” pastures. However, good management practices may be necessary to avoid bacterial contamination of adjacent bodies of water.  相似文献   
902.
Assessing the genetic structure of natural populations differentially impacted by anthropogenic contaminants can be a useful tool for evaluating the population genetic consequences of exposure to pollution. In this study, measures of genetic diversity at variable-number-tandem-repeat loci in six dandelion populations (3 urban and 3 rural) showed patterns that may have been influenced by exposure to environmental contaminants. Mean genetic similarity among individuals within a population was significantly and positively correlated with increasing levels of airborne particulate matter ( 10 m, PM10) and soil concentrations of four metals (Cd, Fe, Ni and Pb). In addition, mean genetic similarity was always significantly higher at the urban sites compared to rural sites. There was a significant negative correlation between the number of genotypes at a site and increasing amounts of PM10, concentrations of five soil metals (Cd, Cu, Fe, Ni and Pb), leaf tissue levels of Fe and a significant positive correlation between the extent of clonality at a site and levels of PM10 and soil concentrations of five metals (Cd, Cu, Fe, Ni and Pb). Although, this study does not directly establish a causal link between the specific contaminants detected at the study sites and differences in genetic diversity, our data are consistent with the hypothesis that pollution-induced selection has contributed in some fashion to the lower genetic diversity found at the urban sites.  相似文献   
903.
The Montreal Process was formed in 1994 to develop an internationally agreed upon set of criteria and indicators for the conservation and sustainable management of temperate and boreal forests. In response to this initiative, the Forest Inventory and Analysis (FIA) and Forest Health Monitoring (FHM) programs of the United States Department of Agriculture Forest Service have implemented soil measurements as part of a national monitoring program to address specific questions related to the conservation of soil and water resources. Integration of soil assessments into the national FIA program provides for systematic monitoring of soil properties across all forested regions of the U.S. using standardized collection, laboratory, and statistical procedures that are compatible with existing forest inventory data. The resulting information will provide quantitative benchmarks for regional, national, and international reporting on sustainable forest management and enhance our understanding of management effects on soil quality. This paper presents an overview of the FIA soil monitoring program, outlines the field and laboratory protocols as currently implemented, and provides examples of how these data may be used to assess indicators of sustainable management as defined by the Montreal Process.  相似文献   
904.
某工业场地砷污染的加密布点优化与精度对比分析   总被引:1,自引:0,他引:1  
场地污染调查是开展场地风险评估和修复的基础,随着我国颁布建设用地土壤风险管控标准等文件,提出风险筛选值和管制值的分级管控体系,我国土壤污染调查工作对于精确掌握污染物浓度梯度及空间分布有了更高的要求,因而如何构建高效采样布点方法变得尤为重要.本研究以南京市某砷工业污染场地为例,开展了优化布点方法与调查精度的研究.首先,在初查数据的基础上,运用指示克里格的方法预测土壤污染概率,参考城市土壤背景值开展阈值设定,提取加密布点区域,之后结合场地历史生产资料与自然信息布设加密点位,最终将插值预测污染结果与非加密、均匀加密、真实情况结果进行对比,验证方法精度.结果表明:本方法符合国际中基于设计抽样以达到场地调查简单、经济、客观的理念,适用于数据存在明显空间相关性的场地;该方法获得的污染区域面积占比为8.32%,与8.57%的现实情况较为接近,但普通法得到的污染面积比相对未加密情况不升反降,可能的原因是在非污染区域增设点位会造成阈值边缘区域在模拟时往清洁区域偏移,污染区域被误判为清洁,反而造成结果偏差;在目前我国环境管理对超阈范围重点关注的背景下,该方法既能够节约布点成本,又精确化预测场地污染超标范围,为后续的场地修复和治理工作提供帮助.  相似文献   
905.
矿井通风系统是一个复杂的非线性系统,具有随机性、模糊性和不确定性特征。应用层次分析法(AHP)和模糊综合评价(FCE)的基本理论建立的AHPFCE模型,可以全面考虑矿井通风系统的各种因素,既能体现评价过程的模糊性,又能尽量减少个人主观臆断带来的弊端,使优选的方案更符合实际,评价结果更可靠。应用加速遗传算法检验和修正判断矩阵的一致性,具有搜索效率高、计算时间短、求解精度高、计算结果稳定、适用性强等特点,是一种全局优化方法。采用AHPFCE方法确定权重,具有较强的逻辑性、实用性和系统性,并能准确地得出各评价指标的权系数,使计算结果更客观和稳定。实例计算结果表明:AHPFCE方法简便和通用,不仅能指导生产实际,而且为类似的方案优化工作提供了一种新的思路和方法。  相似文献   
906.
以REE系统理论为指导,构建了操作性较强的评价指标体系,并建立了基于模糊理论的多层次模糊评价模型,对西部9省市REE系统协调性的空间规律进行了研究.在讨论西部各省区资源、环境、经济和社会发展优劣势的基础上,指出四川和新疆是西部地区的两个协调性高值极点;贵州、甘肃和青海协调性值较低;西藏、云南、陕西、宁夏处于中间水平.  相似文献   
907.
基于希尔伯特空间向量范数的铁路机务安全评价模型研究   总被引:1,自引:0,他引:1  
在分析了层次分析法(AHP)、模糊评判法等评价方法的基础上,笔者提出了基于希尔伯特空间向量范数的铁路机务安全评价模型。围绕建立安全指数模型为核心,充分利用希尔伯特空间上单位球的弱紧性,探讨了建立标准希尔伯特指标子空间M的方法,基于层次分析法的权重算子的生成方法;在考虑相对独立选取指标的基础上,建立了基于M的向量范数的安全指数评价模型及安全指标分析模型。该评价模型具有良好的数据处理功能,包括定性数据和非定性数据;能通过指数分析,对评价对象进行横向和纵向的比较;能通过指标分析,得到各指标对于总指数的贡献率,找出问题和差距,有的放矢地改善安全环境,具有很强的适用性。  相似文献   
908.
于冰  石磊 《环境科学与管理》2007,32(11):158-162
企业是循环经济的基本单元和"小循环"的载体,其循环经济相关指标体系的设计受到越来越多的重视.在辨析循环经济、清洁生产和环境友好企业等概念基础上,分别综述和探讨了企业清洁生产、环境友好企业和循环经济指标体系,并给出相应的对策建议:(1)配合国家试点工作,尽快有针对性地设立企业循环经济指标;(2)企业循环经济指标的设立可以采取分步走的策略;(3)应把生产者责任延伸和消费者付费思想体现在循环经济指标中;(4)尤其要关注组装和间歇制造业的循环经济指标.  相似文献   
909.
燃煤电厂烟气脱硫主要工艺   总被引:4,自引:0,他引:4  
简要介绍燃煤电厂烟气脱硫(FGD)的湿法,半干法,干法,可回收工艺和联合SO2/NOx工艺等五类主要工艺,并对我国烟气脱硫技术的进展进行了探讨,指出我国烟气脱硫技术的发展应走国产化的道路。  相似文献   
910.
The aim of this paper is to show how the environmental practices of a restaurant may be evaluated in a quantitative way. For this, a new methodology, sustainable development records (SDR), was used. This allows financial, environmental and social aspects of an operation to be handled in a systematic way. The results of the two sustainable development audits show that the restaurant washes more dishes per unit of chemicals used in 1994 than in 1991. However, there is a negative trend regarding the number of meals served per unit of water used and waste generated, which suggests that the restaurant in 1994 is more wasteful with these resources than in 1991. On the other hand, this might be explained by the fact that the restaurant has increased its use of primary products. The environmental ratios are increasing for both chemicals and energy, which means that more and more of the resources used are environmentally acceptable. The lowest environmental ratios are those for provisions (<2%) and transportation (<5%), which means that not more than 2% of the provisions and 5% of the transportation are environmentally acceptable in the long run. The restaurant's ratio of satisfied customers as well as its environmental image is improving, while the profitability has not changed. The results of this paper point to a general problem of environmental auditing in regard to the evaluation of perceived positive or negative developments of an individual enterprise, since there might be an opposite implication for the larger system. It is therefore crucial to look at several hierarchical levels in order to be able to assess the effects of environmental measures.  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