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   4262篇
  免费   299篇
  国内免费   252篇
安全科学   148篇
废物处理   99篇
环保管理   1572篇
综合类   1497篇
基础理论   585篇
环境理论   45篇
污染及防治   110篇
评价与监测   76篇
社会与环境   572篇
灾害及防治   109篇
  2024年   9篇
  2023年   50篇
  2022年   63篇
  2021年   100篇
  2020年   110篇
  2019年   142篇
  2018年   122篇
  2017年   212篇
  2016年   195篇
  2015年   157篇
  2014年   145篇
  2013年   222篇
  2012年   215篇
  2011年   271篇
  2010年   183篇
  2009年   238篇
  2008年   171篇
  2007年   245篇
  2006年   202篇
  2005年   202篇
  2004年   166篇
  2003年   154篇
  2002年   152篇
  2001年   127篇
  2000年   146篇
  1999年   122篇
  1998年   74篇
  1997年   84篇
  1996年   77篇
  1995年   75篇
  1994年   58篇
  1993年   64篇
  1992年   33篇
  1991年   36篇
  1990年   29篇
  1989年   15篇
  1988年   11篇
  1987年   7篇
  1986年   12篇
  1985年   18篇
  1984年   10篇
  1983年   9篇
  1982年   8篇
  1980年   7篇
  1979年   15篇
  1978年   8篇
  1977年   7篇
  1973年   9篇
  1972年   5篇
  1971年   10篇
排序方式: 共有4813条查询结果,搜索用时 140 毫秒
481.
Congestion charging is widely considered an effective policy measure to regulate and reduce car traffic demand and associated environmental and health problems in cities. However, introducing restrictive measures to constrain individual choice and behaviour for the common good has often proven difficult. Using a specific case, the Gothenburg congestion tax introduced in 2013, we study the policy process behind the introduction of the tax and assess to what extent green values were compromised along the way. The tax was made possible by co-financing infrastructure investments, including roads, which seemingly contradicts stated goals of reducing car traffic and emissions. We show how the tax was ‘muddled through’ in a top-down political compromise by a grand coalition where different interests could legitimate their support in relation to the achievement of partially conflicting objectives and projects. However, to declare the regulatory goals fully neutralised would be to underestimate the scheme's direct environmental effects and restrictive potential. Finding a compromise with powerful political and economic interests was necessary to get it off the ground. Once launched, however, it can over time regain its restrictive properties and lead to more profound long-term effects.  相似文献   
482.
We investigate natural resource governance in three indigenous communities in the Colombian Amazon. We base our analysis on an evolutionary governance model in which governance dimensions emerge as relevant through time. The less accessible of the communities represents earlier steps in governance evolution, while the more physically accessible is more integrated into the western scene. We observe how increased physical accessibility in a community brings in western governance models which hybridize with more traditional ones, influencing the couplings between the social and ecological systems. We zoom in on changing management of three commonly used palm species and illustrate how detailed studies of natural resource management contribute to understanding governance evolution. By comparing governance evolutions we were able to gain insights and improve our understanding on how natural resource management changes in communities transiting into western ways of living. In doing so we recognized points of rigidity and flexibility which might influence the social ecological systems capacity to adapt to changing conditions.  相似文献   
483.
Theories in risk, psychology, and communication suggest aiming to inform the public about basic ecological facts may not be enough to influence knowledge of risks or behaviors to mitigate water quality risks. The risk information‐seeking and processing model and the theory of planned behavior suggest several additional variables that are likely to influence risk‐mitigating behaviors. We used data from a survey of watershed residents in Ohio to explore a model of behavioral intentions to positively impact stream health. Residents' informational norms, or the perceived pressure to know about local stream health, strongly predicted their information‐seeking behaviors. Active‐seeking behaviors predicted positive attitudes toward behaviors impacting stream health, which predicted intentions to positively impact stream health. Implications for outreach include couching communication in terms of risk found important to the local community, here wildlife were seen as negatively influenced by water quality, as opposed to plain reports typically provided by utility companies. Increasing social pressure to feel informed by emphasizing the existing knowledge of stream ecology among residents could change the norm for the less informed. A low response rate limits the generalizability of findings here, but leveraging these findings in outreach efforts could prove more successful in engaging the public to improve stream health and support policies to improve stream health.  相似文献   
484.
Research of problem definitions typically centres on agenda setting and formulation with less attention given to implementation. In recognition of this gap, this analysis examines the relationship between issue definition, issue redefinition and policy implementation by reviewing two municipal stormwater plans. The results suggest that in larger issue contexts replete with ambiguity and uncertainty, problem definitions are often “tweaked” and adapted during the implementation process. In short, street-level bureaucrats craft “genetically related” but idiosyncratic problem definitions – that fit their own policy-making context. In the case of stormwater, “solutions”; are best described as dynamic policies built upon the values associated with technical expertise, public participation and environmental sustainability.  相似文献   
485.
National authorities in many countries aim at having climate change adaptation mainstreamed into existing policy domains in order to achieve coherence and synergies, and to avoid mal-adaptation. Because of local variations in climate change impacts, the lion's share of climate adaptation work will have to take place at the local level. This means also that the mainstreaming process needs to occur locally. This article examines the mainstreaming of climate change adaptation into existing sectors in five Norwegian municipalities. Applying theories of mainstreaming and policy integration we find that policy development is slower, but perhaps more robust in the municipalities that have chosen a horizontal, cross-sectoral approach to mainstreaming than in the municipalities that have chosen a vertical sector approach to mainstreaming.  相似文献   
486.
High employee turnover rates constitute a major challenge to effective aid provision. This study examines how features of humanitarian work and aid workers’ individual characteristics affect retention within one humanitarian organisation, Médecins Sans Frontières (MSF) Holland. The study extends existing research by providing new theoretical explanations of employment opportunities and constraints and by engaging in the first large‐scale quantitative analysis of aid worker retention. Using a database of field staff (N=1,955), a logistic regression is performed of the likelihood of reenlistment after a first mission. The findings demonstrate that only 40 per cent of employees reenlist for a second mission with MSF Holland, and that workplace location and security situation, age, and gender have no significant effect. Individuals are less likely to reenlist if they returned early from the first mission for a personal reason, are in a relationship, are medical doctors, or if they come from highly developed countries. The paper reflects on the findings in the light of policy.  相似文献   
487.
为评价典型有机污染物对长江三峡库区上游特有珍稀鱼类的环境风险,本实验以稀有鮈鲫为对象,研究了低剂量多环芳烃(PAHs)暴露而引起的内分泌干扰效应.将成年稀有鮈鲫暴露于不同浓度(0、0.1、0.3、1.0和3.0μg·L-1)的苯并芘(Ba P)中28 d,测定了体质系数、性激素含量、下丘脑-垂体-性腺(HPG)轴和肝脏中与繁殖相关基因的表达.结果显示:在雌鱼中,Ba P暴露后,睾酮(T)的含量显著升高,雌二醇(E2)的水平显著下降并改变了T/E2的比值;在雄鱼中,T和E2的含量都显著下降.雌雄鱼性激素的改变可能与类固醇合成相关基因(Cyp17、Cyp19a)表达量的改变有关.Ba P暴露显著抑制了雌雄鱼肝脏中卵黄蛋白原(VTG)基因的表达.以上检测到的激素或者基因表达的改变主要发生在高剂量(3.0μg·L-1)Ba P暴露下,而长江上游库区水体中多环芳烃含量较低(100 ng·L-1),因此推测,库区存在的多环芳烃不会对三峡库区上游水体中的鱼类产生内分泌干扰效应.  相似文献   
488.
Soybean wastewater was used to generate biomass resource by use of purple non-sulfur bacteria (PNSB). This study investigated the enhancement of PNSB cell accumulation in wastewater by Mg2+ under the light-anaerobic condition. Results showed that with the optimal Mg2+ dosage of 10 mg/L, biomass production was improved by 70% to 3630 mg/L, and biomass yield also was improved by 60%. Chemical Oxygen Demand (COD) removal reached above 86% and hydraulic retention time was shortened from 96 to 72 hr. The mechanism analysis indicated that Mg2+ could promote the content of bacteriochlorophyll in photosynthesis because Mg2+ is the bacteriochlorophyll active center, and thus improved adenosine triphosphate (ATP) production. An increase of ATP production enhanced the conversion of organic matter in wastewater into PNSB cell materials (biomass yield) and COD removal, leading to more biomass production. With 10 mg/L Mg2+, bacteriochlorophyll content and ATP production were improved by 60% and 33% respectively.  相似文献   
489.
利用历史数据,选取合适计算模型,定量预测了2014年-2020年江苏省城镇化边际资源环境影响,即以与城镇化发展密切相关的资源使用量或者城镇生活污染物排放量较上一年的增量,除以当年城镇化率增量,得到江苏省城镇化水平每提高一个百分点带来的资源环境影响,以期为江苏环境管理及政府综合决策提供切实有效的数据依据.结果表明:未来7年,江苏省城镇化率每上升1个百分点,增加城镇生活用水量约0.5亿立方米、城镇建设用地面积16万亩;增加城镇生活污水排放量1.15亿吨、生活氮氧化物排放量10 228吨、生活垃圾产生量36.4万吨;减少生活COD排放量7 549吨、生活氨氮排放量762吨、生活二氧化硫(SO2)排放量371吨.  相似文献   
490.
This paper examines the temporal change and spatial variation of population pressure on the ecological environment in China. We have collected sufficient data from the statistical yearbooks of 31 provincial administrative areas in 1990, 1995, 2000, 2005, and 2010. Using a geographic information system (GIS) and relevant models, we analyzed the trend of the population pressure on ecological environment and the change of the gravity center of ecological environment quality. We conclude that: (1) generally, population pressure on the ecological environment in China was becoming higher during 1990–2010, especially in some areas where the population and environment were in serious imbalance and the ecological environment experienced severe pollution; (2) during a certain period, population pressure on the ecological environment was becoming lower in some areas, but the ecological environment was getting worse; (3) the areas with super-high population pressure on the ecological environment were Beijing, Tianjin, and Shanghai; (4) the gravity center of population pressure on the ecological environment and the center of ecological environment quality move differently during the study time period, but the general trend was similar – both of them were moving from west to east. Based on the analysis, this paper also provides some policy suggestions on the control of ecological environment quality.  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