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   12102篇
  免费   852篇
  国内免费   1400篇
安全科学   1838篇
废物处理   705篇
环保管理   3768篇
综合类   4688篇
基础理论   1107篇
环境理论   12篇
污染及防治   1003篇
评价与监测   525篇
社会与环境   422篇
灾害及防治   286篇
  2024年   17篇
  2023年   172篇
  2022年   240篇
  2021年   325篇
  2020年   390篇
  2019年   292篇
  2018年   278篇
  2017年   383篇
  2016年   524篇
  2015年   442篇
  2014年   658篇
  2013年   777篇
  2012年   784篇
  2011年   891篇
  2010年   605篇
  2009年   742篇
  2008年   566篇
  2007年   729篇
  2006年   764篇
  2005年   583篇
  2004年   568篇
  2003年   507篇
  2002年   445篇
  2001年   399篇
  2000年   406篇
  1999年   311篇
  1998年   218篇
  1997年   198篇
  1996年   166篇
  1995年   159篇
  1994年   95篇
  1993年   96篇
  1992年   81篇
  1991年   60篇
  1990年   43篇
  1989年   31篇
  1988年   36篇
  1987年   38篇
  1986年   30篇
  1985年   24篇
  1984年   30篇
  1983年   20篇
  1982年   24篇
  1981年   22篇
  1980年   30篇
  1979年   37篇
  1978年   21篇
  1973年   16篇
  1972年   16篇
  1971年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
洪涝灾害条件下疏散交通生成预测方法   总被引:1,自引:0,他引:1  
为有助于有关部门更准确预测洪涝灾害受灾民众的疏散量,结合非集计数据和集计数据的优点,提出分区集计数据的概念,设计了受灾区域分区方法,并通过意向偏好(SP)调查法对我国居民在洪涝条件下疏散交通需求数据进行调查。在此基础上,引入BP神经网络建立基于分区集计数据的疏散交通生成预测模型。利用调查数据进行实证分析发现,所设计方法取得了较好的预测效果,鲁棒性较好,平均相对预测误差仅为1.8%,其预测效果明显优于现有的非集计和整集计模型。  相似文献   
2.
Although stewardship has been widely defined and used in environmental management and planning, there is a dearth of studies that describe how the lay public perceives this concept. A national sample of residents in 14 states who live near DOE nuclear facilities were interviewed to delineate public understanding and awareness of the stewardship program of the U.S. Department of Energy (DOE). This study discusses the findings of the survey and discusses how institutional trust influences public participation and resident’s choices of potential stewards. Almost 40% of the respondents could not define stewardship; those who did, believed that ‘responsibility,’ ‘management,’ and ‘accountability’ are key elements of stewardship. In addition, about a third of the respondents identified Federal groups and the DOE as potential stewards. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue  相似文献   
3.
On the Kola Peninsula, the mining and concentration industry exerts anthropogenic impact on the environment. Tailing dumps cause airborne pollution through dusting, and waterborne pollution due to direct dumping and accidental releases. The objectives were: (1) to analyse multidate satellite imagesfor 1964–1996 to assess the environmental pollution from themining and concentration activity in the Kola in temporal perspective; (2) to evaluate remote sensing methods for integrated environmental impact assessment. The area of mining and industrial sites steadily expands and amounted to 94 km2 in 1996. The polluted water surface amounted to at least 150 km2 through dumping in 1978 and to 106 km2 in1986 due to dusting. Thus, the impact from the mining and concentration activity should be reconsidered as more significant than it was officially anticipated. In the past the main mechanism of pollution wasdirect dumping into the lakes. Currently and in future, airborne pollution after dusting storms will dominate. The effective recultivation of the tailing dumps will be a long-term process. For effective assessment of impacts from the mining and concentration industry, remote sensing methods should be complemented by in-situ measurements, fieldwork, and mathematical modelling.  相似文献   
4.
Supplementing the nutrient requirement of crops through organic manures plays a key role in sustaining soil fertility, and crop productivity and reducing use of fossil fuels. Field experiments were conducted for 2 years at two different locations (i.e. Lucknow and Pantnagar) in Uttar Pradesh, India. The objectives of the study were to assess the herb and essential oil yields of Japanese mint (Mentha arvensis cv. Hy 77), and its nutrient accumulation under single and combined applications of organic manures and inorganic fertilizers (NPK). Changes in physical and chemical characteristics of the soils (Fluvisols, Mollisols) were also determined. Eight treatments comprising different combinations of NPK through inorganic fertilizers and farm yard manure (FYM) were compared. The distilled waste of mint after extraction of essential oil was recycled to soils in the plots to supplement the nutritional requirement of the succeeding mustard crop (Brassica juncea cv. Pusa Bold). Herb and essential oil yield of mint were significantly higher with combined application of organic and inorganic sources of nutrients as compared to single applications. Accumulation of N and P was at par under full inorganic and combined supply whereas, K accumulation was higher with the former. Soil organic C and pH after harvest of mint did not significantly differ among the treatments, but the level of mineralizable N, Olsen-P and NH4OAc extractable K were higher in soil with integrated supply of nutrients. Significant increase in soil water stable aggregates, organic C, available NPK and microbial biomass, and decrease in soil bulk density were observed with waste recycling over fertilizer application. These benefits were reflected in the seed and stubble yield of mustard which succeeded mint. This study indicates that combined application of inorganic fertilizers with organics helps in increasing the availability of nutrients and crop yield and provides a significant effect to the succeeding crop. Similarly, recycling crop residues reduces the need for fossil fuel based fertilizer, and helps in sustaining and restoring soil fertility in terms of available nutrients and major physical and chemical characteristics of the soil.  相似文献   
5.
运用灰色关联度分析法,定量分析了影响厦门市生活垃圾产生量的影响因子,发现其主要因子是城市国内生产总值(GDP);利用灰色系统理论建立了该市生活垃圾产生量的GM(1,1)预测模型,并进行预测分析。  相似文献   
6.
我国水产养殖业对环境的影响及对策   总被引:7,自引:0,他引:7  
综述了我国水产养殖业的自身污染、对水环境和生态系统的影响及其对景观环境质量的影响等,提出应在健全的法律法规指导下,建立完善的水产养殖环境管理系统,加强营养与饲料学研究,提高水产养殖饲料质量和投饵水平,同时强化环境工程技术在集约化水产养殖中的应用,以减少污染排放,使水产养殖走可持续发展的道路。  相似文献   
7.
危险废物安全填埋场应探讨企业化经营模式。在单一处理模式、一体化经营模式和依托于大型企业模式中选择适宜的模式。填埋场建设资金筹集渠道中,由废物产生单位集资建设是可行办法。探讨了填埋场收费标准的计算方法,并给出计算公式。  相似文献   
8.
It is the key to control bio-derived dissolved organic matters (DOM) in order to reduce the effluent concentration of wastewater treatment, especially for waste leachate with high organic contaminants. In the present study, the anaerobic degradation of aerobically stabilized DOM was investigated with DOM substrate isolated through electrodialysis. The degradation of bio-derived DOM was confirmed by reduction of 15% of total organic carbon in 100 days. We characterized the molecular behavior of bio-derived DOM by coupling molecular and biological information analysis. Venn based Sankey diagram of mass features showed the transformation of bio-derived DOM mass features. Occurrence frequency analysis divided mass features into six categories so as to distinguish the fates of intermediate metabolites and persistent compounds. Reactivity continuum model and machine learning technologies realized the semi-quantitative determination on the kinetics of DOM mass features in the form of pseudo-first order, and confirmed the reduction of inert mass features. Furthermore, network analysis statistically establish relationship between DOM mass features and microbes to identify the active microbes that are able to utilize bio-derived DOM. This work confirmed the biological technology is still effective in controlling recalcitrant bio-derived DOM during wastewater treatment.  相似文献   
9.
根据对医疗废物焚烧残余物中有毒有害物质的化验分析结果,确定焚烧残余物中有毒有害成分含量仍较高,部分指标超出标准值,必须对其进行稳定化/固化处理,避免对土壤及地下水环境造成污染.本文阐述了稳定化/固化处理原理及处理工艺,使医疗废物无害化、减量化和资源化的处理原则得以全面实现.  相似文献   
10.
胶粉的生产利用现状及前景分析   总被引:5,自引:0,他引:5  
废橡胶作为工业垃圾 ,已为世界所公认 ,介绍了废橡胶回收利用的意义和方法 ,着重阐述了胶粉的生产利用现状 ,并简要分析了胶粉的生产利用前景  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