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   1587篇
  免费   199篇
  国内免费   211篇
安全科学   409篇
废物处理   40篇
环保管理   390篇
综合类   717篇
基础理论   138篇
污染及防治   76篇
评价与监测   86篇
社会与环境   80篇
灾害及防治   61篇
  2024年   4篇
  2023年   36篇
  2022年   34篇
  2021年   64篇
  2020年   70篇
  2019年   62篇
  2018年   33篇
  2017年   78篇
  2016年   99篇
  2015年   103篇
  2014年   80篇
  2013年   119篇
  2012年   143篇
  2011年   133篇
  2010年   111篇
  2009年   91篇
  2008年   61篇
  2007年   104篇
  2006年   96篇
  2005年   70篇
  2004年   47篇
  2003年   60篇
  2002年   37篇
  2001年   45篇
  2000年   27篇
  1999年   24篇
  1998年   14篇
  1997年   10篇
  1996年   17篇
  1995年   8篇
  1994年   9篇
  1993年   3篇
  1992年   13篇
  1989年   3篇
  1988年   8篇
  1987年   5篇
  1983年   2篇
  1982年   4篇
  1981年   5篇
  1980年   4篇
  1979年   3篇
  1978年   7篇
  1977年   5篇
  1976年   4篇
  1975年   4篇
  1974年   5篇
  1973年   4篇
  1972年   6篇
  1971年   11篇
  1970年   4篇
排序方式: 共有1997条查询结果,搜索用时 653 毫秒
981.
企业重大事故应急预案编制探讨   总被引:11,自引:4,他引:11  
针对企业编制预案时存在的共性问题,提出了企业预案的核心内容要求,明确了企业预案中应当包括的主要应急行动程序;采用基于应急功能分析的整体预案编制方法,提出了企业预案的基本框架,并对预案中有关报警、警报和备案等问题进行了讨论.  相似文献   
982.
中国城市综合减灾的未来学研究   总被引:3,自引:4,他引:3  
金磊 《灾害学》2005,20(1):116-120
本文从国内外大城市频发的事故灾害现状入手,扼要地探讨了有中国特色的2020年中国城市发展的综合减灾战略研究的框架思路,希望对国家"十一五"城市安全计划的研究制定有所借鉴和启发.  相似文献   
983.
近年来,突发公共事件的应急研究是研究热点,但对小城镇却缺少应有的关注和重视.本文剖析了当前小城镇突发公共事件应急管理存在的弊端,简要介绍了小城镇突发公共事件应急决策系统的设计与实现,包括应急预案、历史灾情库和法律法规库三大功能.着重论述了小城镇突发公共事件应急流程和预案的框架要素,并分析了应急决策系统与小城镇应急管理体制的融合机制问题.  相似文献   
984.
ABSTRACT: For numerical modeling of ground water movement in a real aquifer system, the aquifer is usually divided into hydrogeologically defined zones, each with its own parameter values. The responses of the system, such as head or drawdown, are often available only in some of the zones. The estimated parameters of all the zones are based on the measured response in these limited zones. However, the estimates for some of the zones may be very uncertain, and these zones are therefore not justified by the data. In this paper, an approach is presented to understand which zone may produce uncertain parameter values and should be lumped with its neighbor. This approach is demonstrated using a regional numerical model for pumping test analysis in the Nottinghamshire aquifer, UK. A step-by-step process is used in identifying the aquifer zones and estimating their parameters based on the principle of using the smallest possible numbers of zones and parameters for adequate representation of the drawdown response. After the parameters of each zone are estimated, the sensitivity features of these parameters are examined. The results show that the parameters in one zone can be estimated properly by the drawdown in another zone only when there is significant sensitivity. For transmissivity, sensitivity between zones occurs when there is significant flow between them. For storativity, sufficient sensitivity can occur without large flows between the zones, provided that one zone causes significant drawdown in the other. This idea can be extended to the flow model for a large aquifer system. If the aquifer is divided in such a way that aquifer responses are not sensitive to the parameters in some of the zones, the parameters in those zones cannot be estimated properly and should be lumped into their neighboring zones. In this way, a simple but more reasonable model can be built.  相似文献   
985.
ABSTRACT: Recent developments in multiple objective decision making methods presented in the upcoming sequence of research papers are evaluated and compared with respect to their usefulness in addressing challenging problems in water resources management. Because many of the decision making techniques originated in the field of operational research, the historical evolution of this field is outlined and the current need for developing a wide range of techniques for employment in strategic decision making is pointed out. Informative attributes for classifying decision making techniques are given to allow a practitioner to select decision aids that can best model the key characteristics of the particular problems under study. By systematically applying a wide variety of multiple objective decision making techniques to many different kinds of water resources problems, the authors of the papers clearly demonstrate the effectiveness of utilizing these methods for assisting in making both tactical and strategic decisions in water resources management.  相似文献   
986.
Abstract: This paper describes an interactive data and model generator that is intended to bridge the gap between the water resource enginner and planner and the mathematical progrmming systems approach to regional water supply planning. The optimization objective is to minimize total annual cost with respect to capital investment and operation and maintenance costs. The matrix generator formulates the necessary hydrologic, demographic and programming problem for system optimization. The interactive program guides the user through the input and optimization segments, totally eliminates the chore of manually structuring the model matrix aides in eliminating errors, and allows use by planners without skill in mathematical programming.  相似文献   
987.
ABSTRACT: A new and practical concept in water resources modeling and optimization is introduced. Instead of unrealistically assuming a multipurpose reservoir to be composed of a single lumped pool of water, it is treated as two different pools namely conservation and flood pools. Based on this treatment, the optimization problem is stated using the concepts of Lagrange multipliers and parameter optimization. The optimization problem consists of the material balance equation, the constraints on control and state variables and the objective function.  相似文献   
988.
ABSTRACT: Arizona's water pollution control program is based on authorties of Arizona Revised Statutes and Public Law 92–500, the Federal Water Pollution Control Act Amendments of 1972. The primary areas of this program are monitoring, facility inspections, plan review, planning, discharge permits and grants for the construction of publicly-owned waste water treatment facilities. The discharge permit program deals with control of point-source discharges and is administered by the United States Environmental Protection Agency. The planning and construction grants programs are administered by the State Water Quality Control Council and are implemented by the Bureau of Water Quality Control, which serves as staff to the Council. There are several challenges that face the State in this program. First is the adaptation of the “eastern law” to deal with Arizona's water quality problems. Second is to address problems caused by a long history of “laissez-faire” environmental quality management. Third is a mutual cooperation and coordination among the many entities involved in water resources management. Areas of particular interest in the State's program is the process setting water quality standards and the involvement of people of diversified backgrounds in the field of areawide planning under Section 208 of the Federal Water Pollution Control Act, which is primarily concerned with non-point sources of water pollution.  相似文献   
989.
ABSTRACT: The current 201 study by the Bergen County Sewer Authority illustrates possibilities for improving the currently defined relationships between 201, 208 and 303 studies. The Bergen County Sewer Authority serves 115 square miles in northeast New Jersey, providing sewerage service to 507,000 people in 43 municipalities. Its STP discharges to the Hackensack River, a tidal estuary recently classified as Water Quality Limited, and which receives significant non-plant loading. The subject 201 study is concurrent with 208 and 303 planning by NJDEP. Preliminary evaluations show that detailed 201 work can affect the conclusions of 303 and 208 studies, and that a wider (environmental - social as well as economic) interpretation of cost-effectiveness can demand re-examination of prior assumptions and decisions, a task not typically part of 208–303 work. Increased flexibility is needed in applying 303 and 208 recommendations to defining 201 studies and NPDES permit criteria, particularly in analysis of water use objectives, water quality parameters and future flows, loadings and facility costs. Further, perception of alternatives can be clarified by broadening analysis of costs and control and plant strategies. Inclusion of 201 planning at all stages of regional planning can synergistically improve the total planning process.  相似文献   
990.
ABSTRACT: Irrigation in arid and semiarid regions has led to accumulation of salts, destruction of soil texture, decline in fertility and yield, and eventual abandoning of the land. The problems of irrigated agriculture may be attributed to the fact that managers seldom consider irrigated land as a system consisting of a number of components and that the individual health of each component is vital to the overall health of the entire system. A management model is described here which considers all the important components of an irrigated system and may help maintain a permanent irrigated agriculture. The model optimizes net farm income, maintains favorable hydrologic and salt balance in the irrigated system, meets the concentration requirements of the drainage water for the individual crops, and simulates the impact of the irrigation on the unsaturated and the saturated zone.  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