全文获取类型
收费全文 | 3102篇 |
免费 | 93篇 |
国内免费 | 76篇 |
专业分类
安全科学 | 114篇 |
废物处理 | 26篇 |
环保管理 | 1140篇 |
综合类 | 1120篇 |
基础理论 | 203篇 |
环境理论 | 7篇 |
污染及防治 | 34篇 |
评价与监测 | 37篇 |
社会与环境 | 549篇 |
灾害及防治 | 41篇 |
出版年
2023年 | 19篇 |
2022年 | 40篇 |
2021年 | 51篇 |
2020年 | 62篇 |
2019年 | 58篇 |
2018年 | 53篇 |
2017年 | 97篇 |
2016年 | 93篇 |
2015年 | 70篇 |
2014年 | 79篇 |
2013年 | 136篇 |
2012年 | 124篇 |
2011年 | 160篇 |
2010年 | 112篇 |
2009年 | 96篇 |
2008年 | 105篇 |
2007年 | 158篇 |
2006年 | 130篇 |
2005年 | 154篇 |
2004年 | 158篇 |
2003年 | 153篇 |
2002年 | 123篇 |
2001年 | 89篇 |
2000年 | 133篇 |
1999年 | 139篇 |
1998年 | 81篇 |
1997年 | 72篇 |
1996年 | 55篇 |
1995年 | 69篇 |
1994年 | 51篇 |
1993年 | 54篇 |
1992年 | 50篇 |
1991年 | 36篇 |
1990年 | 25篇 |
1989年 | 9篇 |
1988年 | 14篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1973年 | 11篇 |
1972年 | 9篇 |
1971年 | 15篇 |
排序方式: 共有3271条查询结果,搜索用时 958 毫秒
801.
可再生能源资源评价体系与方法 总被引:8,自引:0,他引:8
本文根据可再生能源资源的特性以及与技术、市场之间的内在联系,构建了可再生能源的资源评价体系,分析了资源量、生产率、生产经济性及不确定性分析等各环节中的具体评价方法和指标框架,并提出了最小和最大经济获利开发量以度量资源生产的经济性潜力 相似文献
802.
Damodar S. Airan 《Journal of the American Water Resources Association》1973,9(3):421-432
ABSTRACT Environmental resources can be managed properly only by adopting a comprehensive approach. The whole environment must be considered as a single system, and prior to any action, all types of environmental impacts caused by it should be studied in detail. This paper underlines the close relationship between different environmental problems, analyzes existing management patterns, and proposes new alternatives whenever applicable. The different constraints, which have to be considered in the decision-making process while developing a plan, are also discussed. It is concluded that efforts neglecting the interaction among different aspects of the environment do not upgrade the quality of water, air, and land to any appreciable degree. 相似文献
803.
James W. McFarland M. Leon Hyatt 《Journal of the American Water Resources Association》1973,9(4):755-767
Alternative futures are defined to be mutually consistent alternative combinations of assumed sets of future conditions. Alternative futures are employed in conjunction with the Wollman-Bonem model to project future water use. The model solutions under different alternative futures provide an indication of the direction and relative magnitude of changes in water use, both in quantity and quality, that may result from changes in policy-influenced variables, technology, and other data. The Wollman-Bonem model is employed in this paper as a tool to illustrate the alternative futures concept. The model can best be cast as an economic model. The model solutions are not given as a set of formal projections, but as various possible water-use-over-time curves. This should aid in disspelling the erroneous idea that it is possible to make distant projections of water use as a single curve. Multiple curves suggest that water use is really a function of many variables. 相似文献
804.
The recent versions of nonlinear programming techniques such as the conjugate gradient and the gradient projection algorithms are used to obtain the optimal operating conditions of a multiple reservoirs system with multiple purposes. These algorithms are compared with other techniques in the literature. The conjugate gradient method incorporates the advantages of both the generalized Newton-Raphson, also known as the quasilinearization technique, and the gradient approach while avoiding their major drawbacks. To illustrate the technique, a water resources system with three reservoirs and a tabular objective function is solved by the two algorithms. 相似文献
805.
To the average layman, the distinction between opinion and attitude is artificial at best, and is neither consistent nor logically defensible. For many purposes one need not distinguish between the two. However, when assessing opinion and attitude the disparity becomes quite evident. Opinion surveys are characteristically concerned with replies to specific questions which need not be related. The responses are kept separately as opposed to being combined into a total score. Attitude scales, on the other hand, typically yield a total score indicating both a direction and intensity of an individual's feelings, thoughts, and predispositions to act toward a given concept. Further, in the construction of an attitude scale, the different statements are designed to measure a single attitude or unidimensional variable. The Likert method of constructing attitude measuring instruments requires a large number of judges to indicate their own attitudes by responding to statements thought to pertain to an attitude in question. Five possible responses are provided for each item. The procedure for construction of a Thurstone type scale utilizes the Law of Categorical Judgment as a basis. Statements are obtained and analyzed for the various categories and in final form, the attitude scale is presented to the respondent who indicates statements with which he agrees or disagrees. 相似文献
806.
Water quality must be considered in the development and planning aspects of water resource management. To accomplish this, the decision-maker needs to have at his disposal a systematized procedure for simulating water quality changes in both time and space. The simulation model should be capable of representing changes in several parameters of water quality as they are influenced by natural and human factors impinging on the hydrologic system. The objective of this work is two-fold. The first goal is to demonstrate the feasibility of developing and utilizing a water quality simulation model in conjunction with a hydrologic simulation model. The model represents water quality changes in both time and space in response to changing atmospheric and hydrologic conditions and time-varying waste discharges at various points in the system. This model has been developed from and verified with actual field data from a prototype system selected for this purpose. The second aim is to set forth procedural guidelines to assist in the development of water quality simulation models as tools for use in the quality-quantity management of a hydrologic unit. 相似文献
807.
Icko Iben 《Journal of the American Water Resources Association》1969,5(2):51-58
The ages-old and ever-growing need for communication and information retrieval among scientists has found expression in the development of indexes, abstracts, reviews and combinations or variations of such. A short review of such efforts is followed by a discussion of efforts along these lines in the new field of water resources science and technology. Such undertakings as the Information Retrieval System of the American Society of Civil Engineers and of the U.S. Water Resources Research Office are compared with that of the American Water Resources Association. 相似文献
808.
As complex social phenomena, public involvement processes are influenced by contextual factors. This study examined agency
goals for public involvement and assessed the importance of local context in remedial action planning, a community-based water
resources program aimed at the cleanup of the 42 most polluted locations in the Great Lakes Basin. Agency goals for public
involvement in remedial action plans (RAPs) were agency-oriented and focused on public acceptance of the plan, support for
implementation, and positive agency-public relations. Corresponding to these goals, citizen advisory committees were created
in 75% of the RAP sites as a primary means for public input into the planning process. Factors that influenced the implementation
of public involvement programs in remedial action planning included public orientation toward the remediation issue, local
economic conditions, the interaction of diverse interests in the process, agency and process credibility, experience of local
leadership, and jurisdictional complexity. A formative assessment of “community readiness” appeared critical to appropriate
public involvement program design. Careful program design may also include citizen education and training components, thoughtful
management of ongoing agency-public relations and conflict among disparate interests in the process, overcoming logistical
difficulties that threaten program continuity, using local expertise and communication channels, and circumventing interjurisdictional
complexities. 相似文献
809.
Safei El-Deen Hamed 《Journal of Agricultural and Environmental Ethics》1993,6(2):145-164
A comprehensive paradigm of environmental ethics should encompass two things: (1) a particular way of life, and (2) a path to achieve that ideal. An effective paradigm must also be internally consistent, yet externally workable in the real world. On the whole, the modern environmental movement has failed to provide these essential components and qualities in its associated philosophies, most of which suffer from being too abstract or too utopian.This paper suggests that Islam, as a religion and as a body of knowledge, is capable of providing its followers with a comprehensive and practical system of environmental ethics. The basic principles and guidelines of the faith represent the conceptual ideal, while Islamic institutions and laws provide the operational components of an ethical system. 相似文献
810.
贵州南部河谷热带性植物共计464种、2变种。主要构成3种植被类型:大型羽状复叶林、稀树草坡灌丛与肉质多刺灌丛。可分为11类经济用途:药用(139种)、纤维(38种)、野果(21种)、观赏(21种)、鞣料(18种)、饲料(13种)、油脂(13种)、淀粉(12种)、紫胶虫寄主(11种)、芳香(6种)、染料(5种)。资源流失与环境变化,使现存资源的保护与深层次利用成为当前的主要问题。 相似文献