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   161篇
  免费   0篇
  国内免费   3篇
安全科学   8篇
废物处理   7篇
环保管理   32篇
综合类   34篇
基础理论   34篇
污染及防治   32篇
评价与监测   8篇
社会与环境   7篇
灾害及防治   2篇
  2022年   2篇
  2020年   4篇
  2019年   3篇
  2018年   2篇
  2017年   5篇
  2016年   4篇
  2015年   5篇
  2014年   5篇
  2013年   18篇
  2012年   5篇
  2011年   7篇
  2010年   6篇
  2009年   8篇
  2008年   6篇
  2007年   14篇
  2006年   8篇
  2005年   4篇
  2004年   2篇
  2002年   8篇
  2001年   3篇
  2000年   1篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1995年   3篇
  1994年   2篇
  1992年   1篇
  1991年   1篇
  1990年   3篇
  1989年   1篇
  1988年   1篇
  1987年   3篇
  1986年   1篇
  1985年   1篇
  1984年   3篇
  1983年   1篇
  1981年   2篇
  1977年   1篇
  1968年   1篇
  1967年   1篇
  1962年   1篇
  1958年   1篇
  1957年   2篇
  1955年   2篇
  1952年   1篇
  1947年   1篇
  1941年   1篇
  1940年   1篇
  1924年   1篇
  1913年   1篇
排序方式: 共有164条查询结果,搜索用时 234 毫秒
101.
OBJECTIVES: Most states now have lengthy learner periods for young, beginning drivers as part of their graduated driver licensing (GDL) systems. Although parents play a vital role during the learner stage of GDL by supervising driving practice, virtually nothing is known about the nature and quality of parental supervision. The objectives of this study were to investigate parents' supervisory behavior and parent-teen relationships during the learner stage of graduated licensing and to evaluate two approaches for assisting parents in supervising their teenager's early driving experience. METHODS: Families of teenagers applying for a learner permit received either a booklet describing highly structured practice sessions for beginning drivers, a series of "tip sheets" offering more generalized guidance, or no special materials. Questionnaires were sent separately to parents and teenagers three to six months after teenagers obtained their permit. RESULTS: Of 1,190 participating families, 653 parents (55%) and 609 teenagers (51%) responded. Both parents and teenagers perceived parents as supportive and helpful during driving sessions. Parents often demonstrated positive behaviors, such as complimenting their teenager and pointing out possible hazards; they also exhibited less desirable behaviors, such as raising their voice, but these were less frequent. A majority of parents (71%) and teenagers (52%) reported that they enjoyed spending this time together. About four months after obtaining a permit, most parents believed their teenager did not yet have enough experience and was not ready to drive unsupervised. Although the reported behaviors are encouraging, within-family agreement was low on most items. Finally, efforts to assist parents proved unsuccessful. Although parents thought the booklet and tip sheets were helpful, most used these materials only in a general way. CONCLUSIONS: The extended learning experience required by GDL programs is a positive experience for many families. However, finding a method for helping parents achieve maximum benefits during this process will be challenging. The results also suggest that current requirements in the learner phase of most state GDL systems (six months; 30-50 hours) may be inadequate to ensure that teenagers obtain a sufficient amount of experience to begin driving safely on their own.  相似文献   
102.
103.
Sierra Leone suffered from 11 years of civil war (1991-2002) resulting in tens of thousands of deaths and mutilations together with massive population displacement. In 2001, ARC International, Sierra Leone conducted a baseline survey of 201 commercial sex workers (CSWs) and 202 military respondents on the knowledge, attitudes and practices surrounding HIV/AIDS and STIs in Port Loko, Sierra Leone. In 2003, a comparable post-intervention survey of 202 CSWs and 205 military respondents was performed. Comparison of baseline and post-intervention results showed that HIV/AIDS knowledge increased among both groups, with those able to name three effective means of avoiding AIDS increasing from 5 per cent to 70 per cent among CSWs, and 11 to 75 per cent among the military. Reported condom use during last sex increased among CSWs from 38 to 68 per cent and among military from 39 to 68 per cent. These results demonstrate that, despite the challenges inherent in a post-conflict country, good-quality AIDS-prevention programmes can be effective.  相似文献   
104.
Wetland rapid assessment methods (RAMs) can provide a cost effective, scientifically defensible estimate of wetland and riparian condition for use in ambient and project monitoring in resource management and regulatory programs. Those who have chosen to develop a RAM to assess wetland and riparian condition are faced with a range of issues and important choices that they must make throughout the development process. This paper is intended as a practical guide to RAM development. Six basic stages in the RAM development process are discussed: (1) organize RAM development by identifying the intended applications, assessment endpoints, and geographic scope of the RAM and forming appropriate teams to advise and review the development process and its products; (2) build a scientific foundation for method development by conducting a literature review, choosing a wetland classification system, building conceptual models, and identifying the major assumptions underlying the model; (3) assemble the method as a system of attributes and metrics that describe a full range of conditions; (4) verify the ability of the method to distinguish between wetlands along a continuum of conditions; (5) calibrate and validate the method against sets of quantitative data representing more intensive measures of wetland condition; and (6) implement the method through outreach and training of the intended users. Important considerations within each of these stages lead to choices in accuracy, precision, robustness, ease of use, and cost. These are identified and the tradeoffs of the various options discussed. Experience with the ongoing development and implementation of the California Rapid Assessment Method (CRAM) is used to illustrate these stages and associated choices in RAM development.  相似文献   
105.
106.
A primary purpose in measuring safety is to develop intervention strategies to avoid future accidents. Recognizing signals before an accident occurs offers the potential for improving safety, and many organizations have sought to develop programs to identify and benefit from alerts, signals and prior indicators. In this paper, we address the challenge of identifying and evaluating leading indicators of safety in virtual organizations–organizations comprised of multiple, distributed members, temporarily linked together for competitive advantage, that share common value chains and business processes supported by distributed information technology. We begin by discussing risk propensity in virtual organizations and leading indicators of safety. We then describe a pilot study to identify leading indicators for one safety-critical system, and use the results of that study and the literature just described to propose an approach to developing leading indicators in virtual organizations.  相似文献   
107.
A systems analysis of the Lake Tahoe Basin indicates significant and accelerating environmental deterioration within the basin, suggests that Tahoe is poised for yet another round of urban expansion, delineates the portion of Tahoe's resources that are consumed by gaming recreation vis-à-vis outdoor recreation, and identifies the Federal government as a contributor to Tahoe's problems. In response to the need for a holistic approach to basin-wide planning and management, ecological carrying capacity concepts are explored as they may be applicable to the Basin's growth patterns, and ideas on establishing a carrying capacity for Tahoe are developed.  相似文献   
108.
109.
ABSTRACT Nebraska is well endowed with water, particularly groundwater, but has few fossil fuel reserves. However, it is located adjacent to states which have almost no water but have enormous quantities of coal and oil shale. Recent court cases facilitate the movement of water from water-rich states such as Nebraska to water-short states, such as Colorado and Wyoming. The possibility of an energy-water partnership exists and raise numerous policy questions. Within Nebraska, energy consumption patterns are similar to those of the nation's, with consumption of electricity in the agricultural sector growing fastest. Water consumption in the state is dominated by agriculture, and future development of groundwater for irrigation is expected to be intense. Although water and energy are both factors of economic production, an equivalent amount of water consumption provides more jobs in the energy industries than in agriculture. Water and energy are also interdependent. Each is required to produce the other and conservation of one will cause conservation of the other. If both agriculture and electricity are involved, such as in irrigation, the conservation effects are synergistic. Current water policy in Nebraska is biased toward agriculture relative to the energy industries and provides little incentive for water conservation. Given recent court cases and economic conditions, the advantages and disadvantages of the sale of water for export or the use of water with Wyoming coal for energy development need to be compared systematically with those of using water only for agriculture.  相似文献   
110.
Adverse environmental effects of intensive agriculture, together with scarcity in phosphates and water, urge farmers to find more sustainable practices. An example of such a sustainable practice is on-farm processing of organic waste. This paper explores three mechanisms that can lead to a widespread uptake of this technique: (1) economies of scale, (2) information sharing, and (3) adjustment of social norms. Although each of these mechanisms has been studied before, this paper provides new insights by considering the interactions that might exist between the different mechanisms when they are applied to real-life situations. Based on a pilot study, we developed a multi-criteria mathematical programming model at individual farm level. We used this model to simulate the uptake of on-farm processing of organic waste, as a result of the three mechanisms and their interactions. Our results show that each mechanism results in an increased uptake, but is not likely to cause a widespread uptake. Interaction between the mechanisms, will lead to a much higher uptake. This result suggests that simultaneous consideration of multiple mechanisms is essential to understand the behaviour of social–ecological systems.  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