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   537篇
  免费   39篇
  国内免费   25篇
安全科学   30篇
废物处理   9篇
环保管理   186篇
综合类   209篇
基础理论   33篇
污染及防治   21篇
评价与监测   17篇
社会与环境   69篇
灾害及防治   27篇
  2024年   3篇
  2023年   11篇
  2022年   14篇
  2021年   17篇
  2020年   34篇
  2019年   16篇
  2018年   7篇
  2017年   27篇
  2016年   31篇
  2015年   23篇
  2014年   15篇
  2013年   25篇
  2012年   23篇
  2011年   49篇
  2010年   13篇
  2009年   19篇
  2008年   27篇
  2007年   23篇
  2006年   16篇
  2005年   18篇
  2004年   12篇
  2003年   8篇
  2002年   13篇
  2001年   13篇
  2000年   12篇
  1999年   18篇
  1998年   20篇
  1997年   9篇
  1996年   7篇
  1995年   12篇
  1994年   9篇
  1993年   8篇
  1992年   6篇
  1991年   1篇
  1990年   5篇
  1989年   4篇
  1988年   4篇
  1987年   3篇
  1986年   9篇
  1985年   6篇
  1984年   2篇
  1983年   3篇
  1982年   4篇
  1980年   1篇
  1968年   1篇
排序方式: 共有601条查询结果,搜索用时 31 毫秒
71.
The empirical evidence of decline in ecosystem services (ES) over the last century has reinforced the call for ES quantification, monitoring and valuation. Usually, only provisioning ES are marketable and accounted for, whereas regulating, supporting and cultural ES are typically non-marketable and overlooked in connection with land-use or management decisions. The objective of this study was to quantify and value total ES (marketable and non-marketable) of diverse production systems and management intensities in Denmark to provide a basis for decisions based on economic values. The production systems were conventional wheat (Cwheat), a combined food and energy (CFE) production system and beech forest. Marketable (provisioning ES) and non-marketable ES (supporting, regulating and cultural) ES were quantified by dedicated on-site field measurements supplemented by literature data. The value of total ES was highest in CFE (US$ 3142 ha−1 yr−1) followed by Cwheat (US$ 2767 ha−1 yr−1) and beech forest (US$ 2328 ha−1 yr−1). As the production system shifted from Cwheat - CFE–beech, the marketable ES share decreased from 88% to 75% in CFE and 55% in beech whereas the non-marketable ES share increased to 12%, 25% and 45% of total ES in Cwheat, CFE and beech respectively, demonstrating production system and management effects on ES values. Total ES valuation, disintegrated into marketable and non-marketable share is a potential way forward to value ES and ‘tune’ our production systems for enhanced ES provision. Such monetary valuation can be used by policy makers and land managers as a tool to assess ES value and monitor the sustained flow of ES. The application of ES-based valuation for land management can enhance ES provision for maintaining the productive capacity of the land without depending on the external fossil-based fertilizer and chemical input.  相似文献   
72.
Climate change effects are becoming evident worldwide, with serious regional and local impacts. The European Union (EU) has launched and developed initiatives and policies that scratch the surface of water resources impacts. This article presents an introduction of the existing environmental policy and more concisely in the areas of climate change and the interactions with water resources. It also addresses main management tools, and plans linked to policies, recent updates on the Science–Policy Interface, highlighting major results from research and development projects. Establishing appropriate policies to tackle climate change impacts on water is essential given the cross-sectorial and flowing nature and the importance of water in all environmental, social and economic sectors. There are still some pending reviews and updates in the current EU policy and its implementation, as well as at the national level in Spain. This article identifies existing gaps, and provides recommendations on how and where reforms could take place and be applied by decision makers in the water policy sector.  相似文献   
73.
The present study assesses the feasibility of exploiting single- and double-basin solar stills in our daily lives. An investigation is carried out to determine the thermal performance and economic viability of making use of solar stills in water desalination. The climatic conditions of Tehran (35°44?N, 51°30?E) are considered to assess the feasibility of the basins. Transient energy and mass balance equations are utilized for modeling the thermal performance. The equations are solved by using fourth-order Runge–Kutta method in FORTRAN. The daily productivities of single- and double-basin solar stills are found to be 5.22 kg/m2 and 7.73 kg/m2, respectively, while the effect of different water masses (20–100 kg) on the productivity of each system was found to be optimum at 20 kg/m2. The results are compared with experimental work performed under different climatic conditions to examine the validity of the feasibility of basins in general. A life cycle cost analysis performed for Tehran, yields that single- and double-basin solar stills have savings-to-investment ratios of 4.2 and 4.8, respectively, indicating that they are economically feasible.  相似文献   
74.
长江经济带开发构想与发展态势   总被引:4,自引:0,他引:4  
长江经济带是我国国土开发和经济建设中极其重要的开发轴线,近年来已经上升为新一轮的国家战略,肩负着参与国际竞争、协调东中西3大区域、推进双向开放、建设生态文明的使命。在国际国内经济社会发展新形势下,长江经济带发展机遇与挑战并存。以流域经济发展为视角,从长江经济带提出的背景出发,回顾了长江经济带战略构想及20世纪80年代以来开发历程,从经济地位、产业集聚、航运建设、岸线开发、沿江交通等5个方面分析了长江经济带发展态势,并重点分析了长江经济带重化工业发展与布局、生态环境影响、港口建设与发展、城市群培育等方面面临的主要问题,最后从改革考核机制、破除行政壁垒、强化流域协调机构与建立流域管理法律法规等方面提出了对策思路,以期为新时期长江经济带开发建设提供参考借鉴。  相似文献   
75.
长江经济带产业分工合作现状、问题及发展对策   总被引:2,自引:0,他引:2  
在梳理长江经济带产业分工与合作现状及问题的基础上,认为长江经济带区际产业发展的互补特征鲜明,下游地区服务业发展较为完善,中上游地区特色产业突出;但也存在市场化程度发育偏低、要素流动不畅、行政区经济严重制约、中心城市产业高度偏低、区域创新能力不足等问题。还根据未来长江经济带产业分工合作的基本思路,提出应发挥下游优势产业的引领带动作用、打造行业龙头骨干企业的辐射结盟作用、加强产业园区的创新示范作用等若干对策建议。  相似文献   
76.
长江经济带研究文献分析   总被引:2,自引:0,他引:2  
长江经济带是我国国土空间开发最重要的东西轴线,近年来推动长江经济带发展逐步上升为新一轮的国家战略。而自长江经济带初步构想于20世纪80年代提出以来,我国学者对长江经济带进行了诸多方面的研究。通过相关研究的文献分析,了解分析文献来源规律,梳理总结文献研究内容,有利于相关学术研究的推进。在查阅了大量相关文献的基础上,首先对文献来源进行分析,接着对长江经济带的概念与范围进行了辨析,再从发展战略、产业发展、交通建设、区域经济差异、区域空间结构、区域协调与合作、地区与长江经济带关系与生态环境等8个方面的对文献内容进行归纳总结与探讨,最后从加强交流合作、宏观微观结合、经典理论应用、关注交通研究、流域联动机制及视野动态开阔等方面对新时期长江经济带研究进行展望。  相似文献   
77.
Though dynamic operation of chemical processes has been extensively explored theoretically in contexts such as economic model predictive control or even considering the potential for cyberattacks on control systems creating non-standard operating policies, important practical questions remain regarding dynamic operation. In this work, we look at two of these with particular relevance to process safety: (1) evaluating dynamic operating policies with respect to process equipment fidelity and (2) evaluating procedures for determining the parameters of an advanced control law that can promote both dynamic operation as well as safety if appropriately designed. Regarding the first topic, we utilize computational fluid dynamics and finite element analysis simulations to analyze how cyberattacks on control systems could impact a metric for stress in equipment (maximum Von Mises stress) over time. Subsequently, we develop reduced-order models showing how both a process variable and maximum Von Mises stress vary over time in response to temperature variations at the boundary of the equipment, to use in evaluating how advanced control frameworks might impact and consider the stress. We close by investigating options for obtaining parameters of an economic model predictive control design that would need to meet a variety of theoretical requirements for safety guarantees to hold. This provides insights on practical safety aspects of control theory, and also indicates relationships between control and design from a safety perspective that highlight further relationships between design and control under dynamic operation to deepen perspectives from the computational fluid dynamics and finite element analysis discussions.  相似文献   
78.
Yellow starthistle (Centaurea solsitialis L.) is an invasive weed that creates problems for the management of Idaho's rangelands. A bioeconomic approach combined with an input-output economic model is used to estimate direct and secondary economic costs of the weed in relation to its interference with agricultural and non-agricultural benefits that rangelands provide. Direct economic costs of the infestations were estimated to be of 8.2 million '05 dollars per year, and secondary costs of 4.5 million '05 dollars per year, for a total of 12.7 million '05 dollars; agricultural related economic impacts accounted for 79% of this total cost, and non-agricultural for 21%.  相似文献   
79.
It has traditionally been argued that recycling municipal solid waste (MSW) is usually not economically viable and that only when externalities, long-term dynamic considerations, and/or the entire product life cycle are taken into account, recycling becomes worthwhile from a social point of view. This article explores the results of a wide study conducted in Israel in the years 2000–2004. Our results reveal that recycling is optimal more often than usually claimed, even when externality considerations are ignored. The study is unique in the tools it uses to explore the efficiency of recycling: a computer-based simulation applied to an extensive database. We developed a simulation for assessing the costs of handling and treating MSW under different waste-management systems and used this simulation to explore possible cost reductions obtained by designating some of the waste (otherwise sent to landfill) to recycling. We ran the simulation on data from 79 municipalities in Israel that produce over 60% of MSW in Israel. For each municipality, we were able to arrive at an optimal method of waste management and compare the costs associated with 100% landfilling to the costs born by the municipality when some of the waste is recycled. Our results indicate that for 51% of the municipalities, it would be efficient to adopt recycling, even without accounting for externality costs. We found that by adopting recycling, municipalities would be able to reduce direct costs by an average of 11%. Through interviews conducted with representatives of municipalities, we were also able to identify obstacles to the utilization of recycling, answering in part the question of why actual recycling levels in Israel are lower than our model predicts they should be.  相似文献   
80.
余博  潘爱民 《自然资源学报》2022,37(6):1481-1493
数字经济技术在产业转型和经济高质量发展中扮演着越来越重要的角色。基于2011—2018年长三角“三省一市”共41个城市数据,测度了长三角地区数字经济和高质量发展的综合水平,分析数字经济对长三角地区高质量发展的影响,创新性地构造了人才流动不平衡指标,并探讨区域内人才流动不平衡对二者关系的调节效应。研究发现:长三角地区高质量发展水平和数字经济规模逐年上升。数字经济发展通过提升生产效率、流通效率和社会便利促进长三角地区高质量发展,非核心区域的正影响强度大于核心区域。人才流动不平衡会逆向调节数字经济对长三角地区高质量发展的正影响程度,但这一调节效应存在区域异质性。此外数字经济对长三角地区高质量发展存在经济距离为权重矩阵的空间负向溢出效应。  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