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   1323篇
  免费   158篇
  国内免费   148篇
安全科学   227篇
废物处理   26篇
环保管理   434篇
综合类   483篇
基础理论   204篇
污染及防治   43篇
评价与监测   64篇
社会与环境   63篇
灾害及防治   85篇
  2024年   5篇
  2023年   23篇
  2022年   39篇
  2021年   52篇
  2020年   40篇
  2019年   61篇
  2018年   41篇
  2017年   50篇
  2016年   52篇
  2015年   54篇
  2014年   51篇
  2013年   87篇
  2012年   73篇
  2011年   90篇
  2010年   66篇
  2009年   73篇
  2008年   57篇
  2007年   81篇
  2006年   76篇
  2005年   65篇
  2004年   42篇
  2003年   45篇
  2002年   63篇
  2001年   33篇
  2000年   42篇
  1999年   40篇
  1998年   21篇
  1997年   23篇
  1996年   22篇
  1995年   24篇
  1994年   19篇
  1993年   15篇
  1992年   21篇
  1991年   5篇
  1990年   4篇
  1989年   5篇
  1988年   8篇
  1986年   2篇
  1985年   2篇
  1984年   5篇
  1982年   3篇
  1981年   2篇
  1980年   3篇
  1979年   3篇
  1978年   6篇
  1977年   6篇
  1976年   4篇
  1975年   6篇
  1972年   4篇
  1971年   9篇
排序方式: 共有1629条查询结果,搜索用时 31 毫秒
211.
Pressures on water resources due to changing climate, increasing demands, and enhanced recognition of environmental flow needs result in the need for hydrology information to support informed water allocation decisions. However, the absence of hydrometric measurements and limited access to hydrology information in many areas impairs water allocation decision‐making. This paper describes a water balance‐based modeling approach and an innovative web‐based decision‐support hydrology tool developed to address this need. Using high‐resolution climate, vegetation, and watershed data, a simple gridded water balance model, adjusted to account for locational variability, was developed and calibrated against gauged watersheds, to model mean annual runoff. Mean monthly runoff was modeled empirically, using multivariate regression. The modeled annual runoff results are within 20% of the observed mean annual discharge for 78% of the calibration watersheds, with a mean absolute error of 16%. Modeled monthly runoff corresponds well to observed monthly runoff, with a median Nash–Sutcliffe statistic of 0.92 and a median Spearman rank correlation statistic of 0.98. Monthly and annual flow estimates produced from the model are incorporated into a map‐ and watershed‐based decision‐support system referred to as the Northeast Water Tool, to provide critical information to decision makers and others on natural water supply, existing allocations, and the needs of the environment.  相似文献   
212.
水资源多目标协同配置:全价值基础上的框架研究   总被引:2,自引:1,他引:1       下载免费PDF全文
从资源的视角而言,水资源具有的社会、经济、生态属性中,社会属性和生态属性所提供的生态功能和服务多是外部性和非市场的,其价值在纯粹的市场驱动下难以充分实现。从资源管理视角而言,水资源多目标协同配置的实质是水资源多重属性功能和服务的均衡。因此,将具有外部性的社会、生态功能和服务与具有经济价值的功能和服务同时纳入配置框架,是实现多目标协同配置实践的关键问题。本文在回顾水资源配置和水资源非市场价值评估的相关研究的基础上,围绕我国现行水资源配置存在的主要问题,通过水资源的全价值(市场价值和非市场价值)将其多属性功能和公众意愿纳入水资源多目标协同配置中,从水资源管理信息系统、全价值评估和配置管理的绩效评价三个方面构建了水资源配置的多目标协同框架,最后提出相关的保障政策建议。  相似文献   
213.
韩相奎  周春生  董春兰 《环境科学》1991,12(6):37-39,47
本文探讨了稀释倍数影响BOD测定结果的生化机理.研究结果表明,稀释倍数不同所引起的BOD测定值不同的原因在于培养体系内食料微生物比F/M值的不同.在相同接种条件下,稀释倍数愈大,BOD测定值和耗氧速率常数K值也愈大,而其BOD_u值基本不变.对标准葡萄糖-谷氨酸溶液来说,不同F/M值的两个培养体系的活菌总数峰值均在两日内出现,且F/M值大的其峰值相对滞后出现;细菌种群在内源呼吸期之前的耗氧速率较大,内源呼吸期的耗氧速率较小.  相似文献   
214.
对大气污染总量控制规划智能决策支持系统的开发步骤和总体结构做了介绍。并描述了该系统中的知识库系统、模型库系统、数据库系统和图形库系统的设计思想,特别是对知识库的构造进行了较详细的叙述。还介绍了神经网络技术在该系统中的应用。指出大气污染总量控制规划智能决策支持系统将为大气污染总量控制提供更科学、更合理、更有效的规划方案。  相似文献   
215.
中国省级环境决策支持系统的系统分析   总被引:13,自引:1,他引:12  
中国省级环境决策支持系统(DSS)是基于GIS和各种模型的空间决策支持系统?该文介绍了DSS系统的系统分析方法和内容,包括软件需求说明?数据需求说明和总体设计   相似文献   
216.
浅谈城市环境综合整治宏观规划   总被引:2,自引:0,他引:2       下载免费PDF全文
结合秦皇岛的实际,初步论述了城市环境综合整治宏观规划的重要作用和内容,并着重对研究制定城市宏观环境规划的几个重要问题进行了初步探讨。主要阐述了3个问题:①环境承载力与“经济-环境”协调度的分析;②宏观环境规划协调因子的分析、包括战略协调、政策协调及技术协调;③战略目标和战略重点的确定。   相似文献   
217.
本文介绍了SEA的发展背景,现有项目EIA在PPPs决策层次上的缺陷和可持续发展理论如何导致SEA的发展,新发展的SEA比较传统的项目EIA所具有的优点,以及当前对SEA的认识和理解,在实践中所采用的形式,和成功的SEA必具备的特征,同时对在当前形势下SEA的实践方式进行了一定的评价,发现SEA的增值效应是SEA实施的先决条件。  相似文献   
218.
In this study, an option pricing model and a dynamic programming model are developed. These models contribute to the improvement of the decision making process in two respects. First, these models allow for the own growth rate of mining costs to be incorporated into the analysis. Second, these models are developed to estimate the satisfactory gross revenue for investing, so that these models are helpful in analyzing multi-metal mines.The two models are applied to estimate the satisfactory revenue for investing in the Carlin east gold mine, Nevada, USA. The satisfactory revenue estimated by the option pricing model is found to be $42.2M, while that estimated by the dynamic programming model is found to be $44.4M. Since the revenue calculated on the basis of the current conditions is $36M, then the decision by option pricing and dynamic programming is to wait and not to invest now. Despite the difference between the two models in estimating and applying the discount rate, the two models generate the same decision.  相似文献   
219.
ABSTRACT: The 1990s have featured a rapid proliferation of “watershed initiatives” in the western United States and elsewhere. Watershed initiatives are ad hoc, voluntary associations typically featuring both governmental and non-governmental actors organized together to collaboratively seek new strategies for addressing water and related natural resource problems at physically relevant regional scales. These efforts are a response to historical and sociopolitical trends that have resulted in increasingly ineffective forums and processes of resource management decision-making, and that have subordinated the role of local stakeholders in problem-solving efforts. In most cases, watershed initiatives appear to provide a pragmatic vehicle for resource managers and stakeholders to address common concerns in a more efficient manner than is otherwise possible, and as such, deserve further application and continued support.  相似文献   
220.
ABSTRACT: Most spatial decision support systems for natural resource planning and management are limited by their scenario-based (non-behavioral), deterministic (non-stochastic) structure. A spatial decision support system is developed that uses a multiple attribute decision-making model to explain how a property manager selects a land and water resource management system (LWRMS) based on its multiple, stochastic economic and environmental attributes. The decision support system assesses sustainable resource management at the property and watershed scales and identifies the most cost-effective policy for enhancing sustainable resource management. Economic attributes are determined with an economic model and environmental attributes are simulated with an environmental model. Input parameters for both models are generated with a geographic information system. The decision support system is used to rank five LWRMS for a sample of 20 farmers in Missouri's Goodwater Creek watershed and for two hypothetical watershed alliance groups. Results indicate that the average farmer and the two alliance groups would rank the five LWRMS in the same manner. From the viewpoint of the watershed alliance, the most preferred LWRMS for the average farmer in the watershed is sustainable.  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