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   1514篇
  免费   50篇
  国内免费   75篇
安全科学   142篇
废物处理   6篇
环保管理   318篇
综合类   510篇
基础理论   143篇
环境理论   1篇
污染及防治   40篇
评价与监测   137篇
社会与环境   137篇
灾害及防治   205篇
  2024年   2篇
  2023年   4篇
  2022年   7篇
  2021年   12篇
  2020年   17篇
  2019年   9篇
  2018年   19篇
  2017年   39篇
  2016年   38篇
  2015年   38篇
  2014年   38篇
  2013年   68篇
  2012年   69篇
  2011年   105篇
  2010年   99篇
  2009年   118篇
  2008年   95篇
  2007年   144篇
  2006年   111篇
  2005年   112篇
  2004年   87篇
  2003年   89篇
  2002年   71篇
  2001年   51篇
  2000年   47篇
  1999年   36篇
  1998年   35篇
  1997年   25篇
  1996年   13篇
  1995年   14篇
  1994年   13篇
  1993年   8篇
  1992年   2篇
  1991年   3篇
  1989年   1篇
排序方式: 共有1639条查询结果,搜索用时 31 毫秒
141.
We use spatial data representing transportation networks, elevation, stand height, and recreation use to construct and compare models of recreation use patterns and visibility in a forest. The recreation use pattern model depicts use frequencies along travel corridors. The visibility model quantifies visibility for all forest areas. We find that the models provide different but complementary types of information. Forest managers who are involved in scheduling harvest operations and want to address the visual concerns of forest visitors may benefit most from the visibility model. Managers who wish to know more about travel patterns or to reroute forest visitors affected by operations may benefit from the use pattern model. A combination of the two models has the highest potential for providing planning assistance in multiple-use forests. Both models may be able to enhance visual resource management (VRM) systems already in use by providing spatially explicit recreation use and visibility data.  相似文献   
142.
This research demonstrates the predictive modeling capabilities of a geographic information system (GIS)-based soil erosion potential model to assess the effects of implementing land use change within a tropical watershed. The Revised Universal Soil Loss Equation (RUSLE) was integrated with a GIS to produce an Erosion Prediction Information System (EPIS) and modified to reflect conditions found in the mountainous tropics. Research was conducted in the Zenzontia subcatchment of the Río Ayuquíla, located within the Sierra de Manantlán Biosphere Reserve (SMBR), México. Expanding agricultural activities within this area will accentuate the already high rate of soil erosion and resultant sediment loading occurring in the Río Ayuquíla. Two land-use change scenarios are modeled with the EPIS: (1) implementation of soil conservation practices in erosion prone locations; and (2) selection of sites for agricultural expansion which minimize potential soil loss. Confronted with limited financial resources and the necessity for expedient action, managers of the SMBR can draw upon the predictive capacity of the EPIS to facilitate rapid and informed land-use planning decisions.  相似文献   
143.
For the last 20 years, human–wildlife conflicts have been rapidly increasing in towns. Although people want “greener” cities, the expansion of disliked species causes problems that are difficult to manage and to reduce. The complexity of the numerous factors involved in these human–wildlife relations needs the development of a comprehensive tool for urban planners. Today, with the development of computers and geographical information systems, it is easier to analyze and combine different spatial data as methods used for the management of risks in studies of natural hazards. Here we present a method for assessing and mapping the risk in cases of human–wildlife conflict. An application to starling management in a town in western France will show the efficiency of our methods to combine information given by a network of experts and to highlight higher risk sites. The map of risk provides a spatial result useful for comprehension, communication between people and agencies, and public education.  相似文献   
144.
/ Data from historical aerial photographs analyzed with a GIS show that river channel change on the Salt River in the Phoenix metropolitan area of central Arizona has been driven by large-scale regional flood events and local human activities. Mapping of functional surfaces such as low-flow channels, high-flow channels, islands, bars attached to channel banks, and engineered surfaces shows that during the period from 1935 to 1997, the relative areal coverage of these surfaces has changed. Flood events have caused general changes in sinuosity of the low-flow channel, but islands have remained remarkably consistent in location and size, while channel-side bars have waxed and waned. The most important determinant of local channel form and process is sand and gravel mining, which in some reaches occupies more than 70% of the active channel area. The general location of mining is closely related to the location of the moving urban fringe, which serves as a market for sand and gravel during construction. Quantitative spatial analysis of imagery supplemented by field mapping shows that for each location within the general channel area, it is possible to specify a probability of encountering a low-flow channel or other fluvial features. Maps showing the distribution of these probabilities of occurrence reveal the most probable location and configuration of the channel as it occurred in the past. Some reaches have the low-flow channel located persistently within a limited area as a result of bedrock or sinuosity controls, but other reaches dominated by flow separation or shallow gradient have almost no persistence in channel location from one flood to another.  相似文献   
145.
以青海省德令哈市为例,论述在土地利用更新调查中应用新技术的情况,以及利用新技术取得的效果,并阐述了土地利用更新调查和建库的工作流程,同时对新技术和新方法在全省的推广应用提出建议。  相似文献   
146.
基于MapX的县级土地利用信息系统设计与实现   总被引:3,自引:0,他引:3  
选用组件式GIS技术,使用地理信息系统组件Mapx5.0和高级语言VB6.0来开发土地利用管理地理信息系统。介绍了MapX的基本功能和系统的设计开发过程,阐述了该系统的功能、总体结构及系统实现。  相似文献   
147.
GIS在琅琊山摩崖石刻及碑刻文物资源保护和管理中,能够支持数字化地图并对文物进行精确定位、文物点的多媒体信息管理、文物时空分布规律研究、文物点周边环境的综合分析以及文物保护和管理的日常办公等。  相似文献   
148.
The EU Flood Directive 2007/60 requires the assessment and delineation of flood risk maps. The latter should provide the required knowledge for the development of flood risk management plans (FRMPs), that should deal with all features of risk management: e.g. preparation, protection and prevention, comprising also the phase of the flood forecasting and warning systems, in addition to the emergency management. The risk maps, delineated through the expert-drive qualitative (EDQ) approach currently adopted in several European countries, such as Italy, fail to represent the information base that needed by stakeholders for selecting the suitable objectives and designing the appropriate mitigation actions for flood risk management. In the EDQ approach, the flood hazard and the potential damage degree maps are combined by means of a matrix to obtain a qualitative flood risk map. However, the performance of the risk matrix is not usually rigorous validated and, therefore, presents limits, such as subjective and not careful explained interpretation of rating and poor resolution, (due to range compression), that can produce errors in comparative ranking of risk areas. In this context, this paper proposes the FloodRisk approach that aims to improve the efficacy of flood risk map overcoming the limits of EDQ approach in supplying the knowledge base that allow to analyze costs and benefits of potential mitigation measures. However, the proposed approach is also able to involve the citizens in the flood management process, enhancing their awareness. An application of FloodRisk procedure is showed on a pilot case in “Serio” Valley, (North Italy), and its strengths and limits, in terms of additional efforts required in its application compared with EDQ procedure, have been discussed focusing on the efficacy of the outcomes provided for the fulfillment of FRMPs. The results have demonstrated the ability of FloodRisk, respect to EDQ approach, to distinguish successfully different levels of vulnerability of exposure elements, thanks to the use of asset value and depth-damage curves, that allows a suitably evaluation of the effectiveness of risk mitigation strategies. In this light, a successfully application of a cost-benefit analysis of FloodRisk approach on a portfolio of alternative mitigation actions, (i.e. structural and non-structural measurements), has been demonstrated on the proposed study case. However, FloodRisk requires additional information, e.g. water depths assessment and assets values, and it needs a proper analysis and communication of the uncertainty in its results. Although they still exist limitations that impede, at present, the FloodRisk application without an adequate understanding and a critical consideration of the hazard, exposure and vulnerability characteristics of the study area, considerations are supplied on how the utilization of this approach can be maximized in the light of the next flood risk maps revision due by December 2019.  相似文献   
149.
Coastal flooding affects physical and social place attachments. Values-based approaches to climate change adaptation examine how risks to place attachments are distributed within and among communities, with a view to informing equitable adaptation policies. In this nascent body of research, divergent theoretical frameworks and empirical approaches to measuring social values are evolving. While some studies explore the things people value about their everyday lives generally—the lived values approach, others locate specific social and cultural values in geographic space—the landscape values mapping approach. This study aims to compare the explanatory value of these two approaches for understanding the social risks of sea-level rise, and appraise whether either or both approaches are likely to meet local adaptation planning needs. It does this by examining the potential social impacts of sea-level rise in Kingston Beach, Australia, informed by a mail-out survey of the community. The lived values approach identified that the natural environment, scenery, relaxed lifestyle and safety are highly important to local residents, while the landscape values mapping approach revealed that Kingston Main Beach is the most highly valued of eight coastal landscape units. Incorporating the landscape values mapping into the lived values cluster analysis revealed that while Kingston Main Beach is highly important for its recreational value to some members of the community, for others manmade features such as community halls or sports ovals may be of higher importance because they facilitate social interactions. There is potential to further integrate these two approaches to better inform adaptation policy about how lived and landscape values are distributed among communities, where they are located in space and whether they change over time. A deeper understanding of such assigned values can lead to improved engagement with coastal residents to inform adaptation policy now and into the future.  相似文献   
150.
如何处理区域内多灾种之间的相互作用关系是当前多灾种综合风险评估研究的热点和难点之一。在梳理沿海城市多灾种之间相互作用关系的基础上,提出一种基于触发关系的多灾种耦合危险性评估方法。首先选取多指标建立单灾种分级方案,计算单灾种初始危险性指数;然后构建基于触发关系的多灾种耦合规则,结合GIS技术进行空间耦合,计算耦合后的危险性指数;最后对耦合后的多灾种危险性的综合进行了探讨。以福建省泉州市为例进行了案例研究,结果表明:该方法在多灾种耦合危险性评估中具有可行性,为后续多脆弱性和多灾种综合风险的研究提供支持,为决策者进行科学风险管理提供依据。  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