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   741篇
  免费   16篇
  国内免费   7篇
安全科学   27篇
废物处理   30篇
环保管理   173篇
综合类   86篇
基础理论   172篇
污染及防治   168篇
评价与监测   51篇
社会与环境   51篇
灾害及防治   6篇
  2022年   7篇
  2021年   14篇
  2020年   11篇
  2019年   11篇
  2018年   19篇
  2017年   20篇
  2016年   18篇
  2015年   20篇
  2014年   16篇
  2013年   82篇
  2012年   30篇
  2011年   42篇
  2010年   24篇
  2009年   24篇
  2008年   41篇
  2007年   48篇
  2006年   35篇
  2005年   18篇
  2004年   19篇
  2003年   38篇
  2002年   24篇
  2001年   10篇
  2000年   13篇
  1999年   5篇
  1998年   11篇
  1997年   9篇
  1996年   9篇
  1995年   8篇
  1994年   18篇
  1993年   11篇
  1992年   4篇
  1991年   6篇
  1990年   10篇
  1989年   4篇
  1988年   5篇
  1986年   6篇
  1985年   9篇
  1984年   6篇
  1983年   12篇
  1982年   10篇
  1981年   7篇
  1980年   7篇
  1979年   6篇
  1978年   5篇
  1977年   4篇
  1974年   2篇
  1973年   1篇
  1972年   1篇
  1971年   2篇
  1917年   1篇
排序方式: 共有764条查询结果,搜索用时 703 毫秒
261.
262.
263.
Social Network Analysis has become an important methodological tool for advancing our understanding of human and animal group behaviour. However, researchers tend to rely on arbitrary distance and time measures when defining ‘contacts’ or ‘associations’ between individuals based on preliminary observation. Otherwise, criteria are chosen on the basis of the communication range of sensor devices (e.g. bluetooth communication ranges) or the sampling frequencies of collection devices (e.g. Global Positioning System devices). Thus, researchers lack an established protocol for determining both relevant association distances and minimum sampling rates required to accurately represent the network structure under investigation. In this paper, we demonstrate how researchers can use experimental and statistical methods to establish spatial and temporal association patterns and thus correctly characterise social networks in both time and space. To do this, we first perform a mixing experiment with Merino sheep (Ovis aries) and use a community detection algorithm that allows us to identify the spatial and temporal distance at which we can best identify clusters of previously familiar sheep. This turns out to be within 2–3 m of each other for at least 3 min. We then calculate the network graph entropy rate—a measure of ease of spreading of information (e.g. a disease) in a network—to determine the minimum sampling rate required to capture the variability observed in our sheep networks during distinct activity phases. Our results indicate the need for sampling intervals of less than a minute apart. The tools that we employ are versatile and could be applied to a wide range of species and social network datasets, thus allowing an increase in both the accuracy and efficiency of data collection when exploring spatial association patterns in gregarious species.  相似文献   
264.
The integration of the Geographic Information System (GIS) with groundwater modeling and satellite remote sensing capabilities has provided an efficient way of analyzing and monitoring groundwater behavior and its associated land conditions. A 3-dimensional finite element model (Feflow) has been used for regional groundwater flow modeling of Upper Chaj Doab in Indus Basin, Pakistan. The approach of using GIS techniques that partially fulfill the data requirements and define the parameters of existing hydrologic models was adopted. The numerical groundwater flow model is developed to configure the groundwater equipotential surface, hydraulic head gradient, and estimation of the groundwater budget of the aquifer. GIS is used for spatial database development, integration with a remote sensing, and numerical groundwater flow modeling capabilities. The thematic layers of soils, land use, hydrology, infrastructure, and climate were developed using GIS. The Arcview GIS software is used as additive tool to develop supportive data for numerical groundwater flow modeling and integration and presentation of image processing and modeling results. The groundwater flow model was calibrated to simulate future changes in piezometric heads from the period 2006 to 2020. Different scenarios were developed to study the impact of extreme climatic conditions (drought/flood) and variable groundwater abstraction on the regional groundwater system. The model results indicated a significant response in watertable due to external influential factors. The developed model provides an effective tool for evaluating better management options for monitoring future groundwater development in the study area.  相似文献   
265.
Compensatory mitigation of impacted streams and wetlands has increased over the past two decades, with the associated industry spending over US$2.9 billion in aquatic restoration annually. Despite these expenditures, evaluations by the National Research Council and U.S. Government Accountability Office have provided evidence that compensatory mitigation practices are failing to protect aquatic resource functions and services, and vague federal policy and inadequate evaluation of compensatory mitigation projects are to blame. To address these weaknesses, an update to federal regulations on compensatory mitigation was released in 2008. Additionally, the 2012 Reissuance of Nationwide Permits, some of which affects compensatory stream mitigation, was recently published. Current policy, as reflected in these documents, still uses nonspecific language to direct compensatory stream mitigation leaving most implementation decisions to the local U.S. Army Corps of Engineers district. The majority of federal mitigation policy has focused on wetland compensation, with other aquatic resources receiving less attention (e.g., streams). In this article, weaknesses of current policy are discussed, as are suggested policy changes to minimize the loss of stream ecosystem functions and services. Compensatory mitigation policy should clearly define key terms, incorporate adaptive management procedures, and provide guidelines for determining mitigation costs and compensation ratio requirements.  相似文献   
266.
There is a need for a global shift towards a low-carbon society and this requires action at the local level. The aim of the study into sustainable community development is to clarify the role of a community as a whole rather than the role of individuals within that community. Mixed methods of literature review and empirical study have been used to translate the knowledge and experience with urban sustainable development into empirical knowledge of a rural, market town setting. The exemplary case study is the Scottish market town Huntly. The main findings of the study show the need for three ingredients for a Community Sustainability Plan for a town such as Huntly. Community involvement is crucial in developing such plans in a rural setting. Further research in more remote settings, e.g. coastal and island communities, is needed to allow broader conclusions on rural sustainable development.  相似文献   
267.
ABSTRACT

Despite growing evidence pointing to the multiple benefits of home gardening, few studies have considered the health and well-being benefits perceived by gardeners who are principally motivated by biodiversity conservation (i.e. home gardening for biodiversity conservation). This study explores the environmental, social and economic co-benefits (and costs) of home gardening for biodiversity conservation in the City of Winnipeg, Canada. A total of 42 semi-structured interviews (30–60?min each) were conducted with 50 home gardeners who were formally certified or locally recognised for undertaking multiple gardening activities that promote biodiversity conservation. Thematic analysis revealed that study participants self-reported a range of environmental, psychological, physiological and social outcomes associated with their home gardening experiences. Despite home gardening often being a solitary activity, most gardeners valued the multiple forms of social interaction that occurred during important social events in their garden, or when connecting with passers-by. Home gardeners also cited benefits related to connection to nature and place attachment; attention restoration; reduced stress and anxiety; improved mood; satisfaction and pride; increased self-esteem and courage to do things differently in life; and, important education or learning opportunities. However, conflicts relating to the nexus between biodiversity and perceived tidiness of gardens emerged, which raise important ethical and social justice issues for sustainability planning. We compare key insights to the benefits (and costs) of community gardening and make some recommendations for future research, including how to engage more disadvantaged groups in gardening for conservation.  相似文献   
268.
269.
Biological systems are frequently used for wastewater treatment and hazardous materials remediation. The primary problem cited with these systems is the lack of a structured methodology that can be used to predict the performance for design and operational applications. The purpose of this article is to present the background and examples of a novel methodology for analyzing biological treatment processes. This technique is much more cost-effective and accurate than conventional approaches. The article will address applications for both biological wastewater treatment systems and bioremediation processes.  相似文献   
270.
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