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   4201篇
  免费   67篇
  国内免费   45篇
安全科学   252篇
废物处理   153篇
环保管理   873篇
综合类   514篇
基础理论   1034篇
环境理论   3篇
污染及防治   963篇
评价与监测   312篇
社会与环境   166篇
灾害及防治   43篇
  2024年   21篇
  2023年   36篇
  2022年   45篇
  2021年   55篇
  2020年   69篇
  2019年   81篇
  2018年   86篇
  2017年   125篇
  2016年   142篇
  2015年   109篇
  2014年   139篇
  2013年   354篇
  2012年   192篇
  2011年   241篇
  2010年   183篇
  2009年   203篇
  2008年   213篇
  2007年   223篇
  2006年   208篇
  2005年   178篇
  2004年   157篇
  2003年   141篇
  2002年   138篇
  2001年   102篇
  2000年   70篇
  1999年   63篇
  1998年   51篇
  1997年   66篇
  1996年   51篇
  1995年   59篇
  1994年   59篇
  1993年   48篇
  1992年   40篇
  1991年   32篇
  1990年   30篇
  1989年   27篇
  1988年   23篇
  1987年   17篇
  1986年   17篇
  1985年   23篇
  1984年   18篇
  1983年   28篇
  1982年   22篇
  1981年   32篇
  1980年   19篇
  1979年   18篇
  1978年   13篇
  1977年   5篇
  1976年   6篇
  1975年   5篇
排序方式: 共有4313条查询结果,搜索用时 15 毫秒
971.
ABSTRACT: Grain transportation is a major economic activity on the multiple use Snake-Columbia River System. Congress is currently considering increased transportation user fees aimed at recapturing federal expenditures for waterway operations and maintenance. Three types of fee structure and four levels of cost recovery are evaluated using a network program model. In each case traffic is diverted away from the river to other Puget Sound ports via truck and rail transport modes. Grain shippers in the region will be adversely affected by a higher transport bill. The Lower Columbia River port economic activities will be negatively affected; however, competitive uses of the river, recreation, and hydroelectric generation will likely benefit modestly.  相似文献   
972.
    
ABSTRACT: The successful design of constructed wetlands requires a continuous supply of water or vegetation that can withstand drought conditions. Having a constant water source is the best alternative to insure species diversity throughout the season. Consequently, detention structure designs should be based on times between events as well as on hydrologic return periods, since between events is when most evaporation and infiltration losses are likely to occur. In arid or semi-arid environments, this is a difficult process because of long interevent times and seasonal changes in precipitation patterns. This discussion is predicated on the assumption that phytoplankton, epiphytic algae, and emergent vegetation require moist conditions to be effective at removing nutrients, metals and other pollutants. There are drought tolerant species of vegetation that can be used in constructed wetlands but it may take several days to re-establish the attached bacteria communities necessary for optimum pollutant removal. This paper examines a stochastic framework to examine the probability of extended dry periods based on historic rainfall data. The number of consecutive dry days is selected for a specified level of assurance. By multiplying this value by the sum of daily system losses, an overall pond volume can be determined that ensures a minimum depth of water. To illustrate the utility of the approach, the method is applied to a site in Spokane, Washington.  相似文献   
973.
974.
Bovine tuberculosis (bovine TB) is the most important animal health and welfare policy issue in Britain. Badgers are a wildlife reservoir of disease, although the eight-year Independent Scientific Group (ISG) Randomised Badger Culling Trial concluded with a recommendation against culling. The report advised government that bovine TB could be controlled, and ultimately eradicated, by cattle-based measures alone. Despite the ISG recommendation against culling, the farming and veterinary industries continued to lobby government for a badger cull. The 2005–2010 Labour government followed the ISG advice and decided against a cull. The 2010–2015 Coalition and the 2015-present Conservative governments have followed a badger culling policy. This paper investigates whether a virtuous government would cull badgers. It provides an overview of virtue theory in the context of government animal health and welfare policy. Bovine TB and badger control policy options are then analysed in the context of the virtues of justice, wisdom, integrity, loyalty, curiosity, trust, empathy, compassion and aesthetics. Justice is the first virtue of government, and badger culling is seriously problematic from a virtue perspective given that five badgers are culled per cow that avoids slaughter as a result. Analysis based on other virtues strongly suggests that government should not cull badgers. The paper concludes that a virtuous government would not cull badgers as part of policy to control bovine TB in cattle.  相似文献   
975.
976.
This paper briefly assesses the economic efficiency case for voluntary initiatives (VIs), discusses some limitations of this type of policy instrument and goes on to consider the role that local‐scale voluntary initiatives might play in assisting small and medium sized enterprises (SMEs) to embrace the issue of environmental performance improvement. The paper examines SME organizational management in relation to the likely effectiveness of their participation in voluntary environment programmes. An environmental attitudes survey carried out with 62 SMEs in East Anglia found that willingness to become involved in such initiatives does exist, but that a better presentation of opportunities for prospective small firms, together with a more tailored approach, will be necessary if VIs for SMEs are to become a more extensive feature of environmental policy making in the UK.  相似文献   
977.
Investigating public decisions about protecting wetlands   总被引:7,自引:0,他引:7  
Quantitative analyses of species protection decisions taken by public authorities regularly show that ecological factors, such as the probability of extinction, often play a minor role in the decision-making process. The taxonomy of the species or its potential conflict with economic development is a more powerful factor. This paper presents quantitative empirical research on the protection of wetlands in Austria. Econometrically estimated models show that geographical and ecological factors (such as the size of the area, elevation and importance for biodiversity) play a significant role in the protection of wetlands. Additional influences include conflict variables encoding the negative effects of the primary economic sector (agriculture) or tourism.  相似文献   
978.
979.
980.
    
The study aims to find out the effect of environmental management initiatives (EMI) on corporate social responsibility (CSR) authenticity and CSR legitimacy. The current study also examines the influence of CSR authenticity on CSR legitimacy and mediating effect of CSR authenticity in the connection between EMI and CSR legitimacy. Data were collected from 309 managers of hotels and tourism industries. Statistical techniques such as correlation and regression were used through AMOS 7.0 software for data analysis. Results reveal that EMI positively predicts CSR authenticity. Moreover, CSR authenticity significantly predicts the CSR legitimacy. The direct link between EMI and CSR legitimacy is also positive and significant. The findings also reveal that CSR authenticity mediates the relationship between both EMI and CSR legitimacy links. These findings suggested that managers in hotel and tourism industry should participate in CSR activities and well-being of the societies using the organizational resources for attaining CSR legitimacy.  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