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   786篇
  免费   34篇
  国内免费   25篇
安全科学   46篇
废物处理   25篇
环保管理   187篇
综合类   99篇
基础理论   262篇
环境理论   1篇
污染及防治   147篇
评价与监测   37篇
社会与环境   27篇
灾害及防治   14篇
  2024年   1篇
  2023年   11篇
  2022年   12篇
  2021年   10篇
  2020年   19篇
  2019年   21篇
  2018年   30篇
  2017年   36篇
  2016年   36篇
  2015年   25篇
  2014年   39篇
  2013年   63篇
  2012年   46篇
  2011年   65篇
  2010年   34篇
  2009年   37篇
  2008年   50篇
  2007年   47篇
  2006年   37篇
  2005年   32篇
  2004年   24篇
  2003年   18篇
  2002年   38篇
  2001年   17篇
  2000年   10篇
  1999年   9篇
  1998年   10篇
  1997年   7篇
  1996年   5篇
  1995年   6篇
  1994年   3篇
  1993年   7篇
  1992年   4篇
  1991年   4篇
  1990年   3篇
  1989年   3篇
  1988年   1篇
  1987年   5篇
  1986年   2篇
  1985年   4篇
  1984年   1篇
  1983年   3篇
  1982年   3篇
  1981年   2篇
  1979年   1篇
  1978年   2篇
  1977年   1篇
  1975年   1篇
排序方式: 共有845条查询结果,搜索用时 31 毫秒
11.
Emitted thermal infrared radiation (TIR, λ= 8 to 14 μm) can be used to measure surface water temperatures (top approximately 100 μm). This study evaluates the accuracy of stream (50 to 500 m wide) and lake (300 to 5,000 m wide) radiant temperatures (15 to 22°C) derived from airborne (MASTER, 5 to 15 m) and satellite (ASTER 90 m, Landsat ETM+ 60 m) TIR images. Applied atmospheric compensations changed water temperatures by ?0.2 to +2.0°C. Atmospheric compensation depended primarily on atmospheric water vapor and temperature, sensor viewing geometry, and water temperature. Agreement between multiple TIR bands (MASTER ‐ 10 bands, ASTER ‐ 5 bands) provided an independent check on recovered temperatures. Compensations improved agreement between image and in situ surface temperatures (from 2.0 to 1.1°C average deviation); however, compensations did not improve agreement between river image temperatures and loggers installed at the stream bed (from 0.6 to 1.6°C average deviation). Analysis of field temperatures suggests that vertical thermal stratification may have caused a systematic difference between instream gage temperatures and corrected image temperatures. As a result, agreement between image temperatures and instream temperatures did not imply that accurate TIR temperatures were recovered. Based on these analyses, practical accuracies for corrected TIR lake and stream surface temperatures are around 1°C.  相似文献   
12.
The Jordan River is among the world’s most famous and culturally and historically significant waterways. The lower stretch of the river, however, has been a victim of development in a water scarce region, with current flows less than 5 % of historical levels. Furthermore, as it functions as an international border in a region of conflict, access to the river and its potential as a tourist attraction has been limited. Recently, there have been numerous calls for rehabilitation of the river. This study presents a first estimate of the economic benefits of such rehabilitation and compares them to the estimated costs. Identical contingent valuation method surveys were administered in Israel, Jordan, and the Palestinian Authority. Evidence from this study shows that, despite the large opportunity costs of increasing environmental flows, rehabilitation of the lower Jordan would produce positive net economic benefits. This is true even though the study estimated only the benefits to local populations, and not to international tourists or those outside the region. Net benefits are maximized when taking a regional, as opposed to strictly national, approach.  相似文献   
13.
‘Fracking’ was on New York's agenda since 2008, yet no decision was made about it until late 2014. The gridlock is an intriguing puzzle given that the Marcellus shale is considered a ‘world class’ energy supply, and development has been aggressive in other US states. While policy scholars typically conceptualize gridlock as policy stability, this paper examines it as a dynamic process by which competing discourse coalitions engage in interactive framing processes that (re)structure the discussion. This suggests that the interaction between contending coalitions influences gridlock. Yet, we lack knowledge about interactive framing between competing coalitions during policy controversies. Our main finding is that a central mechanism of gridlock is the production of conflict through interactive framing dynamics that deny a shared discursive space capable of ushering in a consensus, or reasoned agreement. In New York, this contest evolved from a policy consensus about the economic benefits of fracking to policy negotiation that incorporated environmental threats, and to prolonged policy controversy in which competing discourse coalitions contested notions of fracking in relation to energy production, environmental protection, public health, economic development, and governance. While a ban has been instituted, the failure to bridge discourse coalitions suggests that controversy will persist unless meaning disputes are resolved.  相似文献   
14.
Although significant resources are being spent researching and fostering the relationship between forests and livelihoods to promote mutually beneficial outcomes, critical gaps in understanding persist. A core reason for such gaps is that researchers, practitioners, and policy makers lack the structured space to interact and collaborate, which is essential for effective, interdisciplinary research, practice, and evaluation. Thus, scientific findings, policy recommendations, and measured outcomes have not always been synthesized into deep, systemic understanding; learning from practice and implementation does not easily find its way into scientific analyses, and science often fails to influence policy. Communities of practice (CofPs) are dynamic sociocultural systems that bring people together to share and create knowledge around a common topic of interest. They offer participants a space and structure within which to develop new, systemic approaches to multidimensional problems on a common theme. Uniquely informed by a systems‐thinking perspective and drawing from the scientific and gray literatures and in‐depth interviews with representatives of established CofPs in the natural resource management and development domain, we argue that a well‐designed and adequately funded CofP can facilitate interdisciplinary and cross‐sectoral relationships and knowledge exchange. Well‐designed CofPs integrate a set of core features and processes to enhance individual, collective, and domain outcomes; they set out an initial but evolving purpose, encourage diverse leadership, and promote collective‐identity development. Funding facilitates effective communication strategies (e.g., in person meetings). We urge our colleagues across sectors and disciplines to take advantage of CofPs to advance the domain of forests and livelihoods.  相似文献   
15.
Abstract

Objectives: What are we teaching drivers about safely interacting with cyclists? This is the main objective of the Cycle Aware project. As part of the study, a teaching and learning package is being developed to fill this gap in Australia.

Methods: Cycle Aware is a major national project that takes a mixed methods approach to investigate how cyclists are taught to share the road with cyclists when learning to drive. The project has five stages: (1) a national review of the driver licensing documentation; (2) interviews with key stakeholders (n?=?35) involved with novice driver education; (3) analysis of cyclist-novice driver crash data to identify the most frequent crash types; (4) develop a teaching and learning package (Cycle Aware Package), and; trial and evaluate Cycle Aware Package.

Results: Overall, drivers are taught little about sharing the road with cyclists. Representation of cyclists in government documentation is mixed and mostly negative and interviews identified driver-cyclist tensions related to attitudes and awareness of sharing the road. Crash types were similar among novice and experienced drivers. The Cycle Aware Package is being finalised and will be trialled in South Australia and Northern Territory in early 2019.

Conclusions: Cycle Aware will provide new insights into the way drivers are taught to share the road with cyclists. The Cycle Aware Package with interactive online content and driver competencies will facilitate a new approach to addressing this gap among Australia drivers.  相似文献   
16.
Elemental concentrations and bioaccessibility were determined in background soils collected in Canada as part of the North American Geochemical Landscapes Project. The concentrations of As, Cr, Cu, Co, Ni and Zn were higher in the C-horizon (parent material) compared to 0–5 cm (surface soil), and this observation along with the regional distribution suggested that most of the variability in concentrations of these elements were governed by the bedrock characteristics. Unlike the above-stated elements, Pb and Cd concentrations were higher in the surface layer reflecting the potential effects of anthropogenic deposition. Elemental bioaccessibility was variable decreasing in the order Cd > Pb > Cu > Zn > Ni > Co > As > Cr for the surface soils. With the exception of As, bioaccessibility was generally higher in the C-horizon soils compared to the 0–5 cm soils. The differences in metal bioaccessibility between the 0–5 cm and the C-horizon and among the provinces may reflect geological processes and speciation. The mean, median or 95th percentile bioaccessibility for As, Cr, Cu, Co, Ni and Pb were all below 100 %, suggesting that the use of site-specific bioaccessibility results for these elements will yield more accurate estimation of the risk associated with oral bioavailability for sites where soil ingestion is the major contributor of human health risk.  相似文献   
17.
Behavioral Ecology and Sociobiology - Adult animals of many species often behave in a cannibalistic manner when encountering conspecific offspring. Kin discrimination is critical for avoiding the...  相似文献   
18.
The health of freshwater biota is dependent on streamflow, yet identification of the flow regimes required to maintain ecological integrity remains challenging to states in the United States seeking to establish ecological flows. We tested the relationship between decreases in streamflow and Shannon‐Weaver diversity index of fish species for four flow‐based habitat guilds: riffle, riffle‐run, pool‐run, and pool in North Carolina. We found species that prefer shallow habitats, such as riffles and riffle‐runs were the most sensitive to decreases in streamflow; whereas no significant relationships were found for pool or pool‐run species. The sensitivity to decreases in streamflow was greatest during summer and fall, when streams are naturally lower. When all fish habitat guilds were included in the assessment of flow‐biology relationships, there were no significant relationships to decreases in streamflow. As the sensitivity of fish to reductions in streamflow is not constant across habitat guilds, combining all fish species together for flow‐biology analyses may greatly underestimate the response of fish species to decreases in flow and should be acknowledged when establishing ecological flows.  相似文献   
19.
Regional Environmental Change - Mountainous areas with extreme elevation gradients and corresponding ranges of biophysical and socioeconomic conditions are highly vulnerable to global change. We...  相似文献   
20.
Environmental Economics and Policy Studies - Growing societal pressures, technological trends and government and industry actions are moving the world toward decarbonization and away from the...  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