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   2999篇
  免费   253篇
  国内免费   583篇
安全科学   362篇
废物处理   88篇
环保管理   712篇
综合类   1626篇
基础理论   303篇
环境理论   19篇
污染及防治   152篇
评价与监测   133篇
社会与环境   384篇
灾害及防治   56篇
  2024年   13篇
  2023年   57篇
  2022年   80篇
  2021年   106篇
  2020年   141篇
  2019年   128篇
  2018年   128篇
  2017年   194篇
  2016年   223篇
  2015年   203篇
  2014年   149篇
  2013年   335篇
  2012年   258篇
  2011年   313篇
  2010年   214篇
  2009年   168篇
  2008年   126篇
  2007年   162篇
  2006年   136篇
  2005年   98篇
  2004年   71篇
  2003年   82篇
  2002年   53篇
  2001年   64篇
  2000年   57篇
  1999年   54篇
  1998年   26篇
  1997年   25篇
  1996年   25篇
  1995年   14篇
  1994年   26篇
  1993年   11篇
  1992年   12篇
  1991年   13篇
  1990年   9篇
  1989年   4篇
  1988年   2篇
  1987年   3篇
  1985年   3篇
  1984年   5篇
  1983年   2篇
  1982年   5篇
  1981年   4篇
  1980年   6篇
  1979年   10篇
  1978年   5篇
  1977年   3篇
  1976年   2篇
  1971年   2篇
  1969年   1篇
排序方式: 共有3835条查询结果,搜索用时 640 毫秒
991.
There is a growing ‘energy democracy’ (ED) movement which regards the transition to renewable energy as an opportunity for socio-economic transformation, as well as technological innovation. The literature on ED tends to associate greater democratic control of energy systems with increased community control over the means of energy generation and distribution. Nonetheless, this literature often assumes rather than demonstrates that the forms of governance it promotes are more democratic than the status quo. This analysis contributes to the emerging field of ED by assessing the complex and varied ways in which communities in Scotland practise energy governance. By focusing on three key governance processes (decision-making, accountability and dispute resolution), the importance of local contexts for the establishment and negotiation of democratic practices is demonstrated. This local specificity, however, also raises further questions regarding the universal applicability of the ED concept.  相似文献   
992.
Global climate change and the implementation of energy technologies are among the most pressing issues facing society and the environment today. Related educational content spans the science disciplines. Through an analysis of introductory-level university textbooks from four major US publishers in Biology, Chemistry, and Physics, this study presents trends in terminology and content. As the defining terms, “global warming” and “climate change” are used nearly equally. However, the first location of a working definition for climate change appears earlier. Energy technologies, climate change, and related environmental issues are found, on average, on ≤4% of textbook pages, and variation is large among individual textbooks. Discipline-based trends exist, especially for the energy technologies presented. Addressed separately as a non-renewable, non-fossil fuel, nuclear energy is found on ≤1% of textbook pages and unfavorably represented. The discussion within these science disciplines has implications on introductory-level education, public perception of science, and informed citizenship.  相似文献   
993.
近年来,电动汽车因其在行驶过程中无任何尾气排放,被各国政府视为推动交通部门清洁、低碳发展的重要途径,主要发达国家纷纷推出了各自的电动汽车发展战略。但是,由于电力属于二次能源,其上游电力生产阶段的能源消费是否清洁将对电动汽车的减排效果产生重要影响。考虑到目前中国绝大部分电力源于煤炭,电动汽车是否真正有益于减排还有待进一步验证。目前一些专家和学者基于传统的过程生命周期评价方法对电动汽车的能源消费、温室气体排放做了一些研究,但研究结果差异较大。为了对电动汽车的减排效果进行更精确的研究,本文采用混合生命周期方法对电动汽车的能源消费、温室气体排放进行了计算。同时,在考虑电动汽车的燃料生命周期、车辆制造生命周期的基础上,将相关配套充电设施建设生命周期纳入到电动汽车的全生命周期系统边界内,以使对电动汽车全生命周期的研究结果更加完整、精确。研究结果显示,纯电动汽车并非是"零排放"的,在燃料周期,虽然纯电动汽车的单位里程能源消费强度较小,约为传统汽油车的94.6%,但以煤为主的高碳电力结构导致目前纯电动汽车燃料周期的单位里程温室气体排放强度约为传统汽油车的1.12倍;车辆周期内,纯电动汽车的能源消费和温室气体排放量也略高于传统汽油车;此外,配套充电设施的建设也将增加纯电动汽车全生命周期的能源消费和温室气体排放量。综合燃料、车辆及充电设备的全生命周期,在当前的电源结构及技术条件下,电动汽车虽然具有较高的能源效率和较好的石油替代效果,但其全生命周期内的煤炭消费较高,导致其温室气体排放量高于传统汽油车,在当前的情况下大规模发展电动汽车并不利于温室气体减排。  相似文献   
994.
为减少旅游业能源消耗,实现旅游低碳绿色发展,探讨如何提高旅游业能源效率,基于包含非期望产出的方向性距离函数,首先构建了适应旅游业的Biennial Malmquist-Luenberger(BML)效率指数,以中国30个省市2005~2013年旅游业为实证对象,测度了其能源效率,9 a来旅游业能源效率变化源泉可被分解为全要素生产率、资本对能源替代效应、劳动对能源替代效应、能源结构效应和产出结构效应5项影响因素。研究发现:(1)中国旅游业能源效率整体上处于较低水平,旅游业能源效率可以扩张提升的比例较大。(2)整体上全要素生产率、资本对能源替代效应、劳动对能源替代效应和能源结构效应的提升能促进旅游业能源效率提高。(3)近3 a来劳动和资本投入的能源替代效应对旅游业能源效率变化的作用超过了全要素生产率。(4)区域层面上,东部地区旅游业能源效率高于中西部地区,主要由地区间旅游业对资本投入使用和能源消耗结构的差异造成。(5)整个样本期间,中国17个省市旅游业能源效率呈现下降趋势,背后的因素各有不同,旅游业资本替代效应是湖北省、福建省和浙江省等多数省市旅游业能源效率下降的主要因素,全要素生产率是安徽省、海南省、贵州省和甘肃省旅游业能源效率下降的主要原因。因此,合理利用投入的资源要素对旅游业低能耗发展至关重要,尤其是要发挥好资本对能源的替代效应,高效的资本配置能极大提高旅游能源效率。  相似文献   
995.
Abstract

Machine tool, which is the basis energy consumed device in manufacturing system, its energy consumption model and energy efficiency evaluation are the prerequisites for energy saving in manufacturing. Considering the multi-energy-sources features,analysed the mathematical model of a CNC continuous generating grinding machine tool from the view of energy constitute. The energy sources of a CNC continuous generating grinding machine tool are classified into gear grinding system, grinding wheel dressing system and auxiliary system. Based on the power balance equations of energy flow, the energy flow system of a CNC continuous generating grinding machine tool is established. And then the energy consumption mathematical model of a CNC continuous generating grinding machine tool is set up by combining the power balance equations with the operating features of three kinds of energy sources. The case study shows that the proposed energy consumption model can provide fundamental support for energy consumption forecasting, energy efficiency analysis and energy-saving optimisation during the machine tool operation process.  相似文献   
996.
Abstract

Energy management in small to medium enterprises (SMEs) remains undeveloped due to competing priorities and a lack of specialist knowledge. However considerable savings can be demonstrated where companies take the time to investigate their energy use. Savings of over 20% can be achieved through changes to operational and behavioural practice. Additional benefits, such as improved production tracking and improved maintenance, can been seen which add to the value in undertaking an energy monitoring and targeting (M&T) plan. The method described involves the application of a series of ‘virtuous’ cycles of engagement and energy savings that can be applied from the highest factory level right down to a specific machine. The analysis of overall energy use from utility bills and the visualisation of typical machine power profiles aid in understanding the drivers of energy consumption and in engaging management in energy efficiency. The monitoring of specific machines in production highlights the significant consumption of electricity during non-productive times. The development of energy performance indicators is described for product variations which can be useful in tendering for business and selecting optimum production pathways. The approach is illustrated with data from a case study of a precision engineering SME based in Limerick, Ireland.  相似文献   
997.
Utility-scale solar energy (USSE) development is an emerging cause of land use change across the American Southwest. Many proposed projects in the region have encountered resistance from environmental groups because of concern about endangered, threatened, and special status species. Projects have also faced resistance from impacted local communities and Native American tribes. This research documents land use conflicts that surfaced during the initial wave of USSE development from 2009 to 2015. The goal is to identify potential roots of land use conflict over renewable energy development, to help explain why there is consistent support for renewables in general, but widespread opposition to projects during the proposal and development stages. The primary data presented include public comments to formal rule-making processes, semi-structured interviews conducted from 2009 to 2013, and various media sources. The paper concludes describing emerging planning frameworks that identify sites for USSE with fewer land use conflicts.  相似文献   
998.
We assess the role of fossil fuel prices, energy efficiency, and carbon taxation in achieving climate policy goals using a dynamic general-equilibrium model of the Portuguese economy. Given the forecasts for international fossil fuel prices, improving energy efficiency and implementing a new carbon tax have significantly different economic and budgetary effects. Greater energy efficiency reduces emissions and has a positive economic effect, but increases public and foreign debt. A carbon tax reduces emissions at a cost for the economy, but leads to positive effects on public and foreign debt. Thus, it is important to pursue both strategies. We estimate that under the reference-price scenario, a steady energy efficiency gain of 2%–2.5% per year and a carbon tax of at least 35 € per tCO2 are needed to achieve the stated goal of reducing carbon dioxide emissions by 2030 by an amount equivalent to 40% of the emissions in 1990. These views were fully integrated in a proposal presented by the Commission for Environmental Tax Reform to the Portuguese Government in September 2014, and then discussed in Parliament in November 2014, before enacting a new carbon tax on 1 January 2015.  相似文献   
999.
Water use for oil and gas development (i.e., hydraulic fracturing) is a concern in semiarid basins where water supply is often stressed to meet demands, and oil and gas production can exacerbate the situation. Understanding the impacts of water use for hydraulic fracturing (HF) on water availability in semiarid regions is critical for management and regulatory decisions. In the current work, we quantify water use for HF at several scales — from municipal to state‐wide — using the IHS Enerdeq database for the South Platte Basin. In addition, we estimate produced water (a by‐product of oil and gas production), using data from the Colorado Oil and Gas Conservation Commission to explore reuse scenarios. The South Platte River Basin, located in northeastern Colorado, encompasses the Denver‐Metro area. The basin has one of the most productive oil and gas shale formations in Colorado, with much of the production occurring in Weld County. The basin has experienced higher horizontal drilling rates coupled with an increasing population. Results show water use for horizontal and vertical wells averages 11,000 and 1,000 m3, respectively. Water use for HF in the South Platte Basin totaled 0.63% of the basin's 2014 total water demand. For Weld County, water use for HF was 2.4% of total demand, and for the city of Greeley, water use was 7% of total demand. Produced water totaled 9.4 Mm3 in the basin for 2014, which represents 42% of the total water used for HF.  相似文献   
1000.
Transitioning to renewable energy has become a global phenomenon. Attempts to explain development patterns are often fragmented, focusing on specific rationale for (un)successful deployment or the perspective of specific stakeholders. We recognize the importance for holistic insights for successful and effective environmental policy-making and planning in the context of renewable energy development. Using wind energy as an example, this paper provides methodological toolkits for utilizing content analysis (CA) to gain more holistic insights on renewable energy deployment and policy outcomes. Building on existing literature, past and ongoing research, three variations of CA are presented for understanding stakeholder conflicts surrounding wind energy development as well as public perceptions and responses to the technology across space and over time. Although newspapers are used as an example, these methodological protocols could be applied to diverse forms of data such as interviews, policy documents, reports, public meetings and letters of appeal.  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