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   4638篇
  免费   343篇
  国内免费   368篇
安全科学   429篇
废物处理   99篇
环保管理   1659篇
综合类   1611篇
基础理论   598篇
环境理论   21篇
污染及防治   215篇
评价与监测   85篇
社会与环境   490篇
灾害及防治   142篇
  2023年   77篇
  2022年   114篇
  2021年   110篇
  2020年   154篇
  2019年   145篇
  2018年   151篇
  2017年   249篇
  2016年   276篇
  2015年   226篇
  2014年   179篇
  2013年   380篇
  2012年   274篇
  2011年   381篇
  2010年   257篇
  2009年   234篇
  2008年   189篇
  2007年   239篇
  2006年   202篇
  2005年   153篇
  2004年   130篇
  2003年   134篇
  2002年   92篇
  2001年   103篇
  2000年   94篇
  1999年   107篇
  1998年   59篇
  1997年   54篇
  1996年   57篇
  1995年   50篇
  1994年   47篇
  1993年   24篇
  1992年   30篇
  1991年   25篇
  1990年   19篇
  1989年   14篇
  1988年   14篇
  1987年   22篇
  1986年   22篇
  1985年   26篇
  1984年   26篇
  1983年   14篇
  1982年   15篇
  1981年   12篇
  1980年   18篇
  1979年   25篇
  1978年   23篇
  1977年   17篇
  1973年   17篇
  1972年   14篇
  1971年   17篇
排序方式: 共有5349条查询结果,搜索用时 15 毫秒
71.
An improved energy demand forecasting model is built based on the autoregressive distributed lag (ARDL) bounds testing approach and an adaptive genetic algorithm (AGA) to obtain credible energy demand forecasting results. The ARDL bounds analysis is first employed to select the appropriate input variables of the energy demand model. After the existence of a cointegration relationship in the model is confirmed, the AGA is then employed to optimize the coefficients of both linear and quadratic forms with gross domestic product, economic structure, urbanization, and technological progress as the input variables. On the basis of historical annual data from 1985 to 2015, the simulation results indicate that the proposed model has greater accuracy and reliability than conventional optimization methods. The predicted results of the proposed model also demonstrate that China will demand approximately 4.9, 5.6, and 6.1 billion standard tons of coal equivalent in 2020, 2025, and 2030, respectively.  相似文献   
72.
采动影响下含瓦斯煤岩的损伤变形是一个极其复杂的非线性过程,单纯依靠传统经典弹塑性力学无法准确分析其破坏机理。针对此情况,通过试验研究了不同初始围压条件下含瓦斯煤岩的损伤变形特征,并分析了损伤变形与能量演化规律之间的内在联系。研究表明:初始围压越高,煤样破坏时强度越大,脆性破坏特征越明显,瓦斯流量急剧增加幅度越大,煤样破坏时积累的总能量和弹性应变能越多,且初始围压与弹性能之间满足对数函数关系。采用累积耗散能定义了煤岩损伤变量,并分析了不同阶段损伤与渗透率之间的演化关系。  相似文献   
73.
In the process of implementing EU policy, Member States sometimes introduce new policy instruments in cases where this is not obligatory. To better understand this phenomenon, this paper reviews three cases in which new instruments emerged and develops a methodology to trace back the influence of EU Directives on instrument choice. The method is illustrated by a narrative of the emergence of new management planning instruments during the implementation of the EU Habitats Directive in three EU Member States: Finland, Hungary and the Netherlands. Three key features of a policy instrument are defined, namely, its authoritative force, action content and governance design. These are used to measure the contribution of the Habitats Directive compared to other potential explanatory causes for the emergence of the new policy instrument. In all three reviewed countries a nested causal relationship between the Habitats Directive and the introduction of the new policy instrument is identified. Based on the relative contribution of the Habitats Directive to the emergence of the new instrument a distinction is made whether the Directive acted as a cause, catalyst or if conjunction occurred.  相似文献   
74.
There is a growing concern about integrating biodiversity into urban planning, yet, discussions are concentrated on science-informed planning in general. Few have explored the integration of biodiversity in specific planning instruments, especially in African cities. This paper examines how and what components of biodiversity are integrated into master plans, medium-term plans, building codes, zoning codes and permits in Kumasi City, Ghana. There is limited integration of biodiversity in most planning instruments as they were mostly designed on the basis of health, safety and economy. Allied to lack of funding and public participation, biodiversity in Kumasi is under significant threat from rapid urban development. Creating an opportunity for popular participation and decentralizing the planning system could set the preconditions for local integration and revision of instruments. Simplifying the definition of biodiversity could increase local planners’ appreciation, understanding and their ability to make use of biodiversity data.  相似文献   
75.
Despite the increased importance of and attention to renewable energy, its share in the overall energy mix has varied significantly across countries and over time. There are many determinants of clean energy transitions; this study focuses on political constraints. Here it is argued that political systems that have fewer political constraints have fewer access points through which powerful status quo veto players can slow the progress of clean energy reforms. To test the theory, a hierarchical model is applied on a dataset of 125 countries over four decades. The results provide significant support for the theory. Furthermore, the effects for political constraints hold even when we distinguish between hydro and non-hydro renewable sources and control for regime type. This study builds on research that recognizes the importance of politics in understanding the challenges and opportunities of clean energy reform.  相似文献   
76.
77.
基于SCP模型的节能环保市场分析研究   总被引:1,自引:0,他引:1  
从需求角度出发,区分了节能环保产业中三种不同类型的市场,然后以SCP模型为分析框架,对三种不同类型的市场结构、企业行为和绩效进行了分析和比较,归纳了节能环保产业中不同类型的市场所存在的问题和解决思路。  相似文献   
78.
Patterson, Lauren A., Jeffrey Hughes, Glenn Barnes, and Stacey I. Berahzer, 2012. A Question of Boundaries: The Importance of “Revenuesheds” for Watershed Protection. Journal of the American Water Resources Association (JAWRA) 48(4): 838‐848. DOI: 10.1111/j.1752‐1688.2012.00655.x Abstract: Watersheds transcend jurisdictional boundaries; raising important questions of who should pay for watershed protection, and how can watershed governance be funded? The responsibility and cost for watershed protection has progressively devolved to local governments, resulting in additional negative externalities and financing challenges. Watershed governance structures have formed at the scale of the watershed, but they often lack the financing mechanisms needed to achieve policy goals. Financing mechanisms via local governments provide a reliable source of revenue and the flexibility to address watershed specific issues. We develop a “revenueshed” approach to access the initial challenges local governments face when seeking to finance trans‐jurisdictional watershed governance. The revenueshed approach engages local governments into discussion and implementation of financial strategies for collaborative watershed governance. Legislation places water quality regulations primarily on local governments inside the watershed. The revenueshed approach extends the financial and stewardship discussion to include local governments outside the watershed that benefit from the watershed. We applied the revenueshed approach to the Mills River and Upper Neuse watersheds in North Carolina. Mills River had a partnership governance seeking revenue for specific projects, whereas the Upper Neuse sought long‐term financial stability to meet new water quality legislation.  相似文献   
79.
中国城市化与能源强度关系的交互动态响应分析   总被引:2,自引:0,他引:2  
基于1990-2009年的统计数据,建立城市化率和能源强度间的向量自回归模型,运用协整分析、脉冲响应函数和动态方差分解法,从不同视角对两组变量的交互动态响应关系进行分析和预测,旨在揭示我国城市化水平与能源利用效率的内在联系、互动机制与发展趋势。分析结果表明:尽管在短期内呈现波动态势,我国城市化水平与能源强度之间存在长期均衡关系;两组变量的动态脉冲响应为负,体现出城市化率和能源强度之间的反向变动走势;与城市化相比,能源强度的脉冲曲线波动剧烈,说明单纯依靠能源系统内部来改善能源效率缺乏可持续性;方差分解时序值显示,能源强度对城市化变动因素的累计贡献较低,而城市化水平对能源强度变动的影响显著且增长迅速,说明能源强度的降低并不是城市化率提高的主要动力,反之城市化水平的提高对能源强度的下降具有较强的促进作用。由此可见,通过城市的优化开发与系统建设,能够有效促进能源的可持续利用,实现能源消费与经济增长间的均衡发展。  相似文献   
80.
阐述了火电机组状态及性能全息诊断系统的技术原理、系统结构及应用情况。该系统以解决机组应用性能问题为目标,采用状态空间分析模型,具备多层次分析的运行操作指导,基于性能渐变特性的设备状态检修,包括分散度在内的运行指标考核以及定期的节能潜力诊断等功能,在10余家电厂44台近1500万kW机组上取得了供电煤耗平均降低1.5~3.5g(标煤)/kW.h的节能效果。  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