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   13306篇
  免费   3741篇
  国内免费   359篇
安全科学   897篇
废物处理   253篇
环保管理   2146篇
综合类   8803篇
基础理论   1753篇
环境理论   7篇
污染及防治   1284篇
评价与监测   1641篇
社会与环境   500篇
灾害及防治   122篇
  2025年   106篇
  2024年   347篇
  2023年   470篇
  2022年   569篇
  2021年   610篇
  2020年   584篇
  2019年   551篇
  2018年   464篇
  2017年   623篇
  2016年   629篇
  2015年   699篇
  2014年   671篇
  2013年   851篇
  2012年   823篇
  2011年   905篇
  2010年   706篇
  2009年   685篇
  2008年   610篇
  2007年   789篇
  2006年   824篇
  2005年   611篇
  2004年   560篇
  2003年   606篇
  2002年   498篇
  2001年   462篇
  2000年   440篇
  1999年   313篇
  1998年   234篇
  1997年   209篇
  1996年   195篇
  1995年   136篇
  1994年   124篇
  1993年   83篇
  1992年   82篇
  1991年   64篇
  1990年   50篇
  1989年   20篇
  1988年   16篇
  1987年   30篇
  1986年   16篇
  1985年   11篇
  1984年   6篇
  1982年   16篇
  1981年   18篇
  1980年   13篇
  1979年   10篇
  1978年   16篇
  1973年   8篇
  1972年   10篇
  1971年   13篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
201.
Paul Harvey 《Disasters》1998,22(3):200-217
The paper examines the challenge of rehabilitation from complex political emergencies (CPEs) and identifies a strategy that is characterised as a civil society rebuilding approach. It focuses on Somalia and a case study of a CARE project that aims to build the capacity of local NGOs. The paper argues that civil society in CPEs is simultaneously being undermined and contested by warring parties and emerging after state collapse. The scope of the paper is limited to one case study and that case study examines only a single aspect of civil society: national and international NGOs. The paper therefore presents tentative and preliminary results based on limited research. However, in reviewing the literature and presenting a way of approaching the subject, it aims to suggest a starting-point for developing a theoretical framework for such research. The paper finds that international agencies have tended to focus on civil society institutions simply as conduits for aid money and that this has tended to create organisations which lack downward accountability, are dependent on donors and are not addressing the wider roles for civil society envisaged in the approach. Rebuilding civil society does hold out the promise of giving non-military interests a stronger voice and starting a process of changing the aid delivery culture. Achieving these objectives, however, will be a slow and largely indigenous process and there is a need for lowered expectations about what outside assistance can achieve  相似文献   
202.
基于FAHP的黄河中下游灾害系统脆性评价   总被引:10,自引:0,他引:10  
首次将复杂系统的脆性引用到黄河灾害的研究中,并根据复杂系统的层次结构,采用模糊层次分析法(FAHP)对黄河中下游灾害系统进行了分析.由模糊层次分析法求得了灾害子系统的相对重要度排序向量,找出了极易使黄河中下游系统崩溃的脆性因素.结合黄河中下游的现状,通过对系统必要的脆性分析,为决策者提供重要的参考依据.  相似文献   
203.
电力污闪事故的气象条件分析   总被引:1,自引:0,他引:1  
对1980-2003年长治市发生的26次严重电力污闪事故进行了调研分析.找出了其中主要电力污闪事故发生的成因及其时空分布特征.对诱发污闪的主要气象条件(浓雾、小雪、雨夹雪、毛毛雨、小雨、冰融等恶劣天气)和气象要素(相对湿度、气温、风向、风速、结冰、积雪等)进行了综合分析,给出了污闪事故发生的各类气象条件综合性判别指标以及事故发生可能性的分级预测标准,并提出了预防电力污闪的一些安全措施.  相似文献   
204.
    
Several authoritative studies indicate that air transport makes a strong, positive contribution to economic development – a contribution that far outweighs the environmental and social costs of aviation. This article investigates this benign view, analysing the assumptions upon which it is based and arguing that the relationship between air transport and economic benefits may be more complex than is commonly held. In particular, the benefits of air transport services may be highly unevenly distributed, with particular groups benefiting from air transport provision to a far greater extent than others. Hence this article poses the question of whether air transport is an effective tool for sustainable development, or whether it simply reinforces existing patterns of economic interest and political hegemony. Based on analysis of a range of key documents, some criteria are presented that could potentially be used to indicate how air transport may most effectively be used to promote sustainable development. Copyright © 2008 John Wiley & Sons, Ltd and ERP Environment.  相似文献   
205.
    
The present work attempts to address the main aspects of chronic and extreme risks in contemporary Athens. It focuses on two cases of acute chronic risk bedevilling the capital region, namely road accidents and noise pollution, and one case of extreme risk, namely seismic disasters. In all cases social vulnerability, seen as the attribute of social and economic entities that can serve to increase damage from given danger, is a basic determinant of risk level. This social vulnerability might be defined in terms of three constituent elements: exposure to, resistance against and resilience to danger impacts. The whole analysis seeks the generating causes of the relevant high risk levels; their distribution across the geographical and social space of the capital region; their impacts on citizens' lifestyle and awareness of unsustainability; the public policy actions to abate or mitigate them and the individuals' adaptive reactions or efforts to escape risks and finally the repercussions of individualized and governmental responses on future risk and vulnerability levels. Copyright © 2005 John Wiley & Sons, Ltd and ERP Environment.  相似文献   
206.
本文介绍了一种新型正压空气呼吸器面罩的结构设计。分别从数据采集、曲面重构及实体建模等方面对面罩的数字化设计步骤进行了详细阐述,并对面罩视野进行了初步校核。  相似文献   
207.
/ A number of strategies for the control of vehicular emissions are being considered by the Philippine government to address Metropolitan Manila's air quality problem. An analytical tool is needed for optimizing criteria pollutant reductions given the budgetary constraints. The simplest approach is to take costs and pollutant removals to be linear with each strategy's scale of activity, and this is readily solved as a linear programming problem. Another approach is to use a dynamic system of weights which shift with progressive improvements in pollutant emissions. The two approaches yield somewhat different results, suggesting the sensitivity of the solution to the assumed weights. The study also illustrates the importance of a sound methodology for evaluating priorities given to different air quality goals. One such methodology may involve a polling of expert panels and the public to gain insight into the relative importance given to competing emissions reduction goals. An informal polling of resource agency staff was conducted and discussed in this paper. The authors take the position that proper planning involves tracing intermediate steps to the final outcome and not just focusing on the latter.KEY WORDS: Vehicular emissions; Urban air quality; Emissions control; Optimization; Manila; Environmental systems analysis  相似文献   
208.
The quality of the waters collected from R. Arno was examined in the period September 1988 to December 1989. A first campaign in September/October 1988, during a period of low water, gives a general picture of pollution conditions along the river from the source to the mouth. the river appears to be heavily polluted immediately downstream of Florence and in the area of the textile industry.

In the second campaign, through the whole year 1989, particular attention has been given to the Florence area; the most significant results, compared with those from a previous investigation carried out in 1971, show only a small reduction of the pollution load, due to the shortage and inadequacy of wastewater depuration. Some considerations are reported on pollution drop with full spate.  相似文献   
209.
    
Electrocatalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) are crucial for water splitting and fuel cells/metal–air batteries, of which the benchmark catalysts for HER/ORR and OER are expensive and scarce Pt‐based and Ir/Ru‐based compounds, respectively. In spite of this, no trifunctional electrocatalyst for HER, OER, and ORR with an acceptable performance have been reported. In response, herein, as a proof‐of‐concept experiment, this study first in situ couples element abundant FeM (M = Ni, Co) particles with the nitrogen‐doped porous carbon (NPC) by a facile and scalable strategy. Unexpectedly, the resulted FeM/NPC exhibits superior trifunctional catalytic activities for HER, OER, and ORR even in the same electrolyte, which can be attributed to the synergistic advantages of FeM/NPC in terms of its good conductivity, highly porous structure, high Brunauer−Emmett−Teller (BET) surface area, nitrogen doping, and the intimate contact of FeM and NPC. Furthermore, such trifunctional catalyst makes the overall water splitting work at moderate overpotential, and endows the assembled Zn−air battery with a good performance and impressive capacity to self‐power the overall water splitting, demonstrating its feasibility for practical application.  相似文献   
210.
    
Due to the COVID-19 pandemic, governments imposed several mobility restrictions which can be used to evaluate their impact on air quality and generate better-targeted policies to improve it. Therefore, this study aimed to define sustainable mitigation measures to reduce air pollution based on quantifying the impacts of the restrictions imposed during the COVID-19 pandemic on air quality in Portugal. Thus, hourly concentrations of PM10, PM2.5, NO2, O3, CO and SO2 were obtained from the Portuguese Air Quality Monitoring Network. Data was then divided into six periods (2020–2021) and compared with the corresponding historical periods (2015–2019). Furthermore, the satellite data of NO2, CO, and absorbing aerosol index (AAI) from the sentinel-5P TROPOMI was collected to complement the analysis conducted for the monitoring data. Overall, air quality improved in all study periods and areas, except in industrial sites. The satellite data corroborated the results herein achieved and thus validated the real effect of the measures adopted in the country during the pandemic on air quality. Sustainable policies to improve air quality could include remote (or hybrid) work whenever possible as a long-term measure and prohibition of travelling between municipalities when an extraordinary event of high air pollution is predicted or occurs. Other policies should be adopted for industrial areas. Given this, and as the restrictive mobility measures had a strong effect on reducing air pollution, the post-COVID era represents an opportunity for society to rethink future mobility and other emerging policies, that should favour softer and cleaner means of transportation.  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