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   248篇
  免费   8篇
  国内免费   2篇
安全科学   15篇
废物处理   5篇
环保管理   47篇
综合类   28篇
基础理论   71篇
环境理论   1篇
污染及防治   58篇
评价与监测   23篇
社会与环境   7篇
灾害及防治   3篇
  2023年   1篇
  2022年   2篇
  2021年   3篇
  2020年   4篇
  2019年   3篇
  2018年   6篇
  2017年   5篇
  2016年   11篇
  2015年   6篇
  2014年   3篇
  2013年   27篇
  2012年   12篇
  2011年   15篇
  2010年   11篇
  2009年   16篇
  2008年   12篇
  2007年   18篇
  2006年   15篇
  2005年   6篇
  2004年   5篇
  2003年   8篇
  2002年   4篇
  2001年   2篇
  2000年   7篇
  1999年   4篇
  1998年   4篇
  1997年   1篇
  1996年   5篇
  1995年   3篇
  1994年   3篇
  1993年   2篇
  1992年   2篇
  1991年   1篇
  1990年   3篇
  1989年   2篇
  1988年   3篇
  1987年   3篇
  1986年   1篇
  1985年   2篇
  1984年   3篇
  1983年   5篇
  1982年   2篇
  1981年   3篇
  1978年   2篇
  1968年   1篇
  1967年   1篇
排序方式: 共有258条查询结果,搜索用时 15 毫秒
251.
It has long been known that the re-use of syringes can cause the spread of infections such as HIV and hepatitis. The production of disposable syringes was undertaken as a solution to the infection problem. In developing countries, however, there has been an unwanted result: the re-use and recycling of disposable syringes. One response has been "auto-disable" syringes that lock the plug and piston in place after a single use. These types of approaches, however, have resulted in greatly increased volumes of used injection materials. This is a particular problem in developing countries where contaminated medical wastes find their way into municipal garbage where people are known to scavenge and recycle. This poses obvious health risks, both in terms of direct exposure and environmental contamination. This study of issues and options for the safe destruction and disposal of used injection materials was undertaken using document analysis was to bring together and summarise approaches to the inter-related issues of "syringe re-use" and "clinical waste disposal". The authors suggest that holistic approaches to syringe use and clinical waste disposal need to be utilized in addressing the situation outlined. The focus is on technology and procedures that may be adaptable to rural areas in developing countries.  相似文献   
252.
253.
254.
Made-up ground collected from layers of a trial pit excavated on a former industrial site was treated with artificial rainwater in a series of column leaching and sorption experiments. Metal mobility and the ability of various layers of material obtained from the pit to act as sources or sinks of potentially toxic elements were assessed. Samples from different layers varied in their abilities to raise the pH of rainwater applied at pH 3.5 and 4.3, and this was reflected in the amounts of metals mobilised by the rainwater as it percolated through the soil column. Material from the top two layers of the pit released cadmium, copper, manganese, lead, nickel and zinc to the aqueous phase, but the lower layers, with higher buffering capacity, were able to resist acidification even when the equivalent of 12 months' rainfall (western UK) was applied. Column sorption experiments confirmed the ability of material from layer 4 (48-50 cm) to take up copper, manganese and zinc. Metals were determined in the leachates by flame and electrothermal atomic absorption spectrometry and principle anions by ion chromatography.  相似文献   
255.
The northern Great Plains of Saskatchewan is one of the most significantly modified landscapes in Canada. While the majority of anthropogenic disturbances to Saskatchewan’s grasslands are the result of agricultural practices, development of petroleum and natural gas (PNG) resources is of increasing concern for grassland conservation. Although PNG developments require formal assessment and regulatory approval, follow-up and monitoring of the effects of PNG development on grasslands is not common practice. Consequently, the effects of PNG activity on grasslands and the spatial and temporal extent of such impacts are largely unknown. This paper examines the spatial and temporal extent of PNG development infrastructure from 1955 to 2006 in a grassland ecosystem in southwest Saskatchewan. The effects of PNG development on grassland ecology were assessed from measurements of ground cover characteristics, soil properties, and plant community composition at 31sites in the study area. PNG lease sites were found to have low cover of herbaceous plants, club moss (Lycopodiaceae), litter, and shallow organic (Ah) horizons. Lease sites were also characterized by low diversity of desirable grassland plants and low range health values compared to off-lease reference sites. These impacts were amplified at active and highly productive lease sites. Impacts of PNG development persisted for more than 50 years following well site construction, and extended outward 20 m–25 m beyond the direct physical footprint of PNG well infrastructure. These results have significant implications with regard to the current state of monitoring and follow-up of PNG development, and the cumulative effective of PNG activity on grassland ecosystems over space and time.  相似文献   
256.
Abstract

This paper presents an evaluation framework that aims to improve the outcomes of triple bottom line (TBL) reporting. Currently, most assessments of TBL reporting focus on report content. Our view is that effective evaluation of TBL reporting should go beyond reports as the outputs of a process and focus on what is being learned through the process, the capacity- and relationship-building that might eventuate, and how this impacts on the development of sustainability. To enable more effective reflection of TBL reporting processes, we developed a set of evaluation criteria focused on the process of reporting. These criteria were identified from case studies of social, environmental and/or sustainability reporting processes documented in the literature. A large number of potential criteria were synthesised into three desired outcomes of TBL reporting and 10 prompts for discussion and reflection during evaluation. This evaluation framework should assist those dedicated to challenging assumptions that inhibit progress towards a sustainable future for society.  相似文献   
257.
Objectives: Motor vehicle crashes remain a leading cause of death in the United States (US). Thoracic aortic dissection due to blunt trauma remains a major injury mechanism, and up to 90% of these injuries result in death on the scene. The objective of this study is to understand the modern risk factors and etiology of fatal thoracic aortic injuries in the current US fleet.

Methods: Using a unique, linked, Fatality Analysis Reporting System (FARS) and Multiple Cause of Death (MCOD) database from 2000–2010, 144,169 drivers over 16 years of age who suffered fatal injuries were identified. The merged database provides an unparalleled fidelity for identifying thoracic aortic injuries due to motor vehicle accidents. Thoracic aortic injuries were defined by ICD-10 codes S250. Univariate and multivariate logistic regression models for presence of any thoracic aortic injuries were fitted. Age, gender, BMI weight categories, vehicle class, model year, crash type/direction, severity of crash damage, airbag deployment location, and seatbelt use, fatal injury codes, and location of injury were considered. Odds ratios (OR) and corresponding 95% confidence intervals (95%CI) are calculated.

Results: There were 2953 deaths (2.10%) related to thoracic aortic injuries that met the inclusion criteria. Nearside crashes were associated with an increased odds (OR = 1.42, 1.1-1.83), while rollover crashes (OR =.44,.29-.66) were associated with a reduced odds of fatal thoracic aortic injury. Using backward selection on the full multivariate model, the only significant model effects that remained were vehicle type, crash type, body region, and injury type.

Conclusions: The increased prevalence of fatal thoracic aortic injury in nearside crashes, increasing age, and vehicle type provide some insight into the current US fleet. Important factors, including model year, had significantly lower levels of the injury in univariate analysis, demonstrating the effect of safety improvements in newer model vehicles. Further study of this fatal injury is warranted, including comparisons of those who survive the injury.  相似文献   

258.
The problem and promise of scale dependency in community phylogenetics   总被引:1,自引:0,他引:1  
The problem of scale dependency is widespread in investigations of ecological communities. Null model investigations of community assembly exemplify the challenges involved because they typically include subjectively defined "regional species pools." The burgeoning field of community phylogenetics appears poised to face similar challenges. Our objective is to quantify the scope of the problem of scale dependency by comparing the phylogenetic structure of assemblages across contrasting geographic and taxonomic scales. We conduct phylogenetic analyses on communities within three tropical forests, and perform a sensitivity analysis with respect to two scaleable inputs: taxonomy and species pool size. We show that (1) estimates of phylogenetic overdispersion within local assemblages depend strongly on the taxonomic makeup of the local assemblage and (2) comparing the phylogenetic structure of a local assemblage to a species pool drawn from increasingly larger geographic scales results in an increased signal of phylogenetic clustering. We argue that, rather than posing a problem, "scale sensitivities" are likely to reveal general patterns of diversity that could help identify critical scales at which local or regional influences gain primacy for the structuring of communities. In this way, community phylogenetics promises to fill an important gap in community ecology and biogeography research.  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