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排序方式: 共有101条查询结果,搜索用时 15 毫秒
1.
资源与资源利用者共存系统的数学模型初探   总被引:1,自引:0,他引:1  
本文在种群营养动力学的基础上分析了资源及其利用者的共存系统。结论表明,如果人类过度利用资源,则此共存系统将要崩溃。  相似文献   
2.
光照、水温和营养盐对浮游植物生长重要影响大小的顺序   总被引:11,自引:3,他引:11  
根据光照、水温、营养盐对浮游植物生长影响的研究结果,综合分析光照、水温、营养盐影响浮游植物生长的变化和其集群结构的改变,探讨了上述因子影响浮游植物生长的生理特征和其集群结构的改变特点.本文阐明光照、水温和营养盐对浮游植物生长影响的机理和过程,确定了它们对浮游植物生长重要影响大小的顺序,由小到大的重要影响程度依次为:光照、水温和营养盐Si.这样,在人类的活动中,首先要考虑输入大海的营养盐Si,其次要关注海洋的水温变化,为海洋生态的持续发展做出积极的贡献.  相似文献   
3.
Eight stormwater user fees (SUFs) were applied to the City of Roanoke and the Town of Blacksburg, Virginia, to determine the effect each has on how land use type impacts the sources of revenue. Roanoke is larger and includes more industrial areas, but less multifamily impervious areas than Blacksburg, which translates differently in the SUFs. Residential parcels comprise the highest percentage of the revenue in all eight SUFs in Blacksburg and four in Roanoke. For both municipalities, two specific SUFs consistently comprised the highest percentage burden for residential homeowners while three other SUFs demonstrated the highest burden for commercial parcels. Open space parcels contain little impervious area, yet account for up to 27% of the revenue in the Blacksburg Area fee structure. Industrial parcels comprise more revenue in Roanoke, averaging 10.1‐4.5% in Blacksburg. Fee types that are easier to administer (e.g., Flat fees) may not fully represent the stormwater contribution from the parcels. SUF types that more accurately represent the stormwater burden on the municipality are also more administratively intensive and are more variable with fee factors.  相似文献   
4.
煤炭行业清费建税,资源税从价计征引起了社会各界对资源税费制度改革的热议,而资源耗减价值是资源税费制度改革的重要依据之一。将资源回采率纳入使用者成本模型,科学计量了我国2000-2011年间煤炭资源的耗减价值。分析表明:2000-2011年间,4%折现率下煤炭资源耗减价值增加了22倍之多,而资源税费却仅仅增长了7倍,煤炭资源耗减价值与资源税费实际征收额之间存在有巨大缺口得不到补偿;国家资源所有者权益的实现度与煤炭经济形势呈逆向分布,煤炭工业利润率的上升并没有带来国家资源所有者权益的增加,导致这种错位的原因与我国不合理的资源税收机制有很大关系;资源税税率的理论区间为1.11%-8.85%,与国家规定的2%-10%高度重合,从而说明国家决策的合理性。为使资源所有者权益的实现度与煤炭工业经济形势相"挂钩",以资源税收入等于资源耗减价值为切入点,对资源所有者权益的实现度进行数理分析,求得了资源税税率与当期资源价格的关系,发现固定税率的资源税难以适应市场波动,于是提出"资源税+利润税"的组合税收工具,确定了利润税的起征点,计算得出了资源税和利润税的税率组合。该组合税制在一定程度上能够平抑经济周期对煤炭工业造成的影响,同时又维护国家资源所有者权益,从而实现国家与煤炭工业"利益共享、风险共担"。  相似文献   
5.
建设项目环境影响报告编制过程中常因未注意到某些关键问题的论述,而使环境影响报告缺乏科学性和可靠性,导致环境影响评价结论依据不足.为使建设项目从环境保护角度分析更具有可行性,以某橡胶制品项目为例,总结了橡胶制品工业项目环境影响评价文件中需注意的几个要点问题,为环境保护主管部门审批环境影响评价文件提供必要的依据,为此类项目更好地开展环境保护工作提供指导.  相似文献   
6.
Wang, Jinxia, Jikun Huang, Lijuan Zhang, Qiuqiong Huang, and Scott Rozelle, 2010. Water Governance and Water Use Efficiency: The Five Principles of WUA Management and Performance in China. Journal of the American Water Resources Association (JAWRA) 46(4): 665-685. DOI: 10.1111/j.1752-1688.2010.00439.x Abstract: In recent years China has attempted to reform water management by decentralizing water management responsibilities. The overall goal of our paper is to better understand the emergence of water user associations (WUAs) in China and assess if they are adhering to the practices spelled out by the Five Principles, a set of recommended practices that are supposed to lead to successful WUA operation. Using four sets of different types of villages to examine implementation and performance, we find that World Bank-supported WUA villages (“Bank villages”) can be thought of as operating mostly according to the Five Principles. For example, the Bank villages were endowed with a more reliable water supply; were set up and were operating with a relatively high degree of farmer participation; and leaders were more consultative and the process more formal. When WUAs are run according to the Five Principals, we show that WUAs increase water use efficiency. The study also provides evidence that there is a perception in the Bank villages that water management is improving in general and that there is less conflict both within the village and among villages. Perhaps more importantly, we find that the Bank’s effort to promote WUAs extended beyond their own project villages. The openness, consultative nature, and transparency found in the Bank WUAs are also found (albeit at a somewhat lower level) in the non-Bank WUA villages.  相似文献   
7.
Option value is estimated for the Washakie Wilderness, northwest Wyoming, USA, using the contingent valuation technique. Consumer surplus, the traditional measure of economic value, is estimated separately and compared with option value. Several populations are tested, including Washakie visitors, Yellowstone National Park visitors, and residents from four metropolitan test markets: Salt Lake City, Utah; Portland, Oregon; Nashville, Tennessee; and Orlando, Florida, USA. The average annual preservation option value (consumer surplus) expressed by on-site wilderness visitors is $46.17 ($80.13), by urban residents is $9.70 ($8.97), and by rural residents is $8.43 ($7.80). Four selected attributes are determined to be important in motivating option demand for the Washakie, including existence value, bequest value, the desire for an on-site visit, and interest in securing the visiting privileges of others. The results suggest that option value is important in wilderness valuation and that off-site users account for a large part of the economic value of wilderness.  相似文献   
8.
土地利用总体规划修编重点与难点问题探讨   总被引:1,自引:0,他引:1  
土地利用总体规划是国民经济和社会发展规划的重要组成部分,是统筹城乡建设、加强土地管理的基础,是实现世界上最严格的耕地保护制度的基本手段。在新一轮土地利用总体规划修编之际,对上轮规划存在的主要问题从宏观层面上进行了分析与探讨,有助于新一轮规划的科学编制和有效实施。简要介绍了规划修编的背景,并对本轮规划修编的网上调查结果进行了分析。通过回顾和分析上一轮土地利用总体规划实施过程中存在的主要问题,提出本轮规划修编应以统筹城乡发展、加强部门协调、促进节约集约、合理增加弹性、提高公众参与等为理念,并就本轮规划的重点与难点方面提出了建设性的意见和建议。  相似文献   
9.
ABSTRACT: The Environmental Protection Agency administers a construction grant program to encourage abatement of wastewater pollution by sharing with municipalities the costs of wastewater treatment facilities. The enabling legislation (P.L. 92–500) specifies that EPA's cost share will be 75% of construction costs. It further requires municipalities to collect user fees from industrial users of the facilities to repay that part of the federal grant allocable to the treatment of industrial wastewater. The municipality must return half of the user fees collected to the U.S. Treasury; the municipality is allowed to retain the remaining half. Retention by municipalities of these user fees lowers their effective cost shares and results in the following consequences: (1) a bias for municipalities to select certain kinds of abatement techniques regardless of whether or not they are the least-cost techniques from the national perspective; (2) a bias for municipalities to select larger-than-optimal scales of abatement facilities; (3) a hidden federal subsidy to industry; and (4) grants that favor industrial communities. This article examines the legislative and regulatory requirements for user charges, derives the algebraic expressions for calculating the real federal, municipal, and industrial cost shares with user fees; computes municipal cost shares for selected values of the determinant factors; evaluates efficiency and other consequences of current user fee arrangements; and concludes that the efficiency distortions brought about by the impacts of user fees on cost sharing could be eliminated by requiring that all user fees collected from industry against the federal cost share be returned to the U.S. Treasury.  相似文献   
10.
许涛  朱文昌 《四川环境》2008,27(1):42-45,60
本文简要介绍了环境监测技术规范中所规定的数值修约规则及相关规范要求的主要内容,并给出了相应的Excel修约公式和修约函数,可方便地用于对环境监测工作中实验测定和计算得出的各种数值进行修约。修约公式是一个利用Excel工作表函数构造的满足数值修约基本规则的工作表计算公式,在给定修约位数的前提下,可直接在工作表单元格中使用修约公式对数值进行修约,对于简单应用,具有方便、快捷、直观的特点。修约函数是一个利用Excel VBA编制的自定义函数,共有四个参数,其调用方法同工作表函数,具有针对性强、灵活、便捷的特点,可根据环境监测技术规范的特定要求,实现自动按有效位数或小数位数进行数值修约,并按相应的格式输出数据。  相似文献   
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