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   286篇
  免费   6篇
  国内免费   1篇
安全科学   16篇
废物处理   7篇
环保管理   74篇
综合类   36篇
基础理论   76篇
环境理论   1篇
污染及防治   54篇
评价与监测   19篇
社会与环境   5篇
灾害及防治   5篇
  2023年   5篇
  2022年   3篇
  2021年   3篇
  2018年   2篇
  2017年   4篇
  2016年   11篇
  2015年   7篇
  2014年   5篇
  2013年   22篇
  2012年   10篇
  2011年   14篇
  2010年   4篇
  2009年   14篇
  2008年   14篇
  2007年   12篇
  2006年   10篇
  2005年   10篇
  2004年   15篇
  2003年   9篇
  2002年   12篇
  2001年   11篇
  2000年   3篇
  1999年   3篇
  1998年   6篇
  1997年   6篇
  1996年   2篇
  1995年   3篇
  1994年   4篇
  1993年   6篇
  1992年   6篇
  1991年   3篇
  1990年   8篇
  1989年   4篇
  1987年   6篇
  1985年   2篇
  1984年   5篇
  1983年   1篇
  1982年   3篇
  1981年   5篇
  1980年   2篇
  1979年   2篇
  1978年   2篇
  1977年   1篇
  1972年   3篇
  1971年   1篇
  1969年   1篇
  1968年   2篇
  1961年   1篇
  1959年   1篇
  1929年   1篇
排序方式: 共有293条查询结果,搜索用时 15 毫秒
231.
Human actions can contribute to degradation of coastal environments or they can increase the likelihood that these environments will be restored. Beach nourishment provides a basis for restoration, but ways must be found to add habitat improvement to projects designed for shore protection. This study examines how beach nourishment projects can help reinstate dune landscapes in locations where beaches and dunes had been replaced by static shore protection structures. Dune topography and vegetation on three nourished sites on the northern Adriatic Coast of Italy are compared to a reference site to evaluate changes after beach fill was emplaced. Results reveal how nourishment projects used for shore protection can restore the space available for dunes to form, increase the likelihood of sediment transfers inland and increase the diversity of topography and vegetation. Beach raking prevents formation and growth of hummocky, incipient backshore dunes that would otherwise evolve into a naturally functioning foredune. Sand-trapping fences can speed the process of foredune development but can be counterproductive if they interfere with transport to beach grass (Ammophila littoralis) planted landward of them. Shore protection structures can provide stability and more time for dune evolution on eroding shores, resulting in greater species richness and longer retention of ecological niches. These structures need not be required if re-nourishment occurs frequently enough to provide a beach wide enough to protect against storm wave uprush.  相似文献   
232.
233.
The English-Wabigoon River system in Northwestern Ontario, Canada, was one of the most heavily mercury-contaminated waterways in the world due to historical discharges in the 1960s from a chlor-alkali plant. This study examines long-term (1970-2010) monitoring data to assess temporal trends in mercury contamination in Walleye, Northern Pike and Lake Whitefish, three species important for sport and subsistence fishing in this region, using dynamic linear modeling and piecewise regression. For all lakes and species, there is a significant decline (36-94%) in mercury concentrations through time; however, there is evidence that this decline is either slowing down or levelling off. Concentrations in the English-Wabigoon fish are elevated, and may still present a potential health risk to humans consuming fish from this system. Various biotic and abiotic factors are examined as possible explanations to slowing rates of decline in mercury concentrations observed in the mid-1980s.  相似文献   
234.
The environment and its interactions with human systems, whether economic, social, or political, are complex. Relevant drivers may disrupt system dynamics in unforeseen ways, making it difficult to predict future conditions. This kind of “deep uncertainty” presents a challenge to organizations faced with making decisions about the future, including those involved in air quality management. Scenario Planning is a structured process that involves the development of narratives describing alternative future states of the world, designed to differ with respect to the most critical and uncertain drivers. The resulting scenarios are then used to understand the consequences of those futures and to prepare for them with robust management strategies. We demonstrate a novel air quality management application of Scenario Planning. Through a series of workshops, important air quality drivers were identified. The most critical and uncertain drivers were found to be “technological development” and “change in societal paradigms.” These drivers were used as a basis to develop four distinct scenario storylines. The energy and emissions implications of each storyline were then modeled using the MARKAL energy system model. NOx emissions were found to decrease for all scenarios, largely a response to existing air quality regulations, whereas SO2 emissions ranged from 12% greater to 7% lower than 2015 emissions levels. Future-year emissions differed considerably from one scenario to another, however, with key differentiating factors being transition to cleaner fuels and energy demand reductions.

Implications: Application of scenarios in air quality management provides a structured means of sifting through and understanding the dynamics of the many complex driving forces affecting future air quality. Further, scenarios provide a means to identify opportunities and challenges for future air quality management, as well as a platform for testing the efficacy and robustness of particular management options across wide-ranging conditions.  相似文献   
235.
Under contract to the U.S. Environmental Protection Agency, Research Triangle Institute has been conducting research to improve the precision, accuracy and limit of detection attainable with the EPA Method 25 nonmethane organic (NMO) analyzer. In Method 25, volatile organic carbon (VOC) samples are collected by drawing gas from an emitting source through a dry ice cooled sample trap and into an evacuated collection tank. The hydrocarbon concentration emitted from the source is determined on a per-carbon basis by catalytically converting the trap and tank sample fractions to CO2 and quantitating the amount of CO2 produced using the NMO analyzer. A reduction catalyst evaluation led to the selection of an NMO analyzer reduction catalyst which operates at a moderate temperature and displays no appreciable effect on peak shape. A gas chromatographlc column system which provides better permanent gas separation and hydrocarbon quantitation was also selected for use in the NMO analyzer.  相似文献   
236.
Mercury (Hg) is a persistent environmental contaminant found in many freshwater and marine ecosystems. Historical Hg contamination in rivers can impact the surrounding terrestrial ecosystem, but there is little known about how far downstream this contamination persists. In 2009, we sampled terrestrial forest songbirds at five floodplain sites up to 137 km downstream of an historical source of Hg along the South and South Fork Shenandoah Rivers (Virginia, USA). We found that blood total Hg concentrations remained elevated over the entire sampling area and there was little evidence of decline with distance. While it is well known that Hg is a pervasive and long-lasting aquatic contaminant, it has only been recently recognized that it also biomagnifies effectively in floodplain forest food webs. This study extends the area of concern for terrestrial habitats near contaminated rivers for more than 100 km downstream from a waterborne Hg point source.  相似文献   
237.
METHOD: This study examined states' performance on Patient Safety Indicators (PSIs), statistics on malpractice lawsuits, and analogous data on automobile accidents to identify state-level patterns in safety and claiming. RESULTS: Hospital safety varied in a pattern similar to highway safety on the state level, suggesting that cultural traits may play a greater role than differences in legal or other environmental factors. States performing well or poorly in hospital and driver safety tended to correspond with states grouped together in regional culture typologies developed by Elazar and Lieske. Traits of regional culture also are associated with variations in tort claiming. CONCLUSIONS: The paper offers a theory of social capital as an important factor affecting safety and tort claiming. Where the regional culture is one of high cohesion and trust, people may exercise a higher degree of caution and vigilance in their interaction with others, and feel less inclination to file lawsuits subsequent to accidents.  相似文献   
238.
We predicted the effects of sulfate (SO(4)) deposition on wilderness areas designated as Class I air quality areas in western North Carolina using a nutrient cycling model (NuCM). We used three S deposition simulations: current, 50% decrease, and 100% increase. We measured vegetation, forest floor, and root biomass and collected soil, soil solution, and stream water samples for chemical analyses. We used the closest climate stations and atmospheric deposition stations to parameterize NuCM. The areas were: Joyce Kilmer (JK), Shining Rock (SR), and Linville Gorge (LG). They differ in soil acidity and nutrients, and soil solution and stream chemistry. Shining Rock and LG have lower soil solution base cation and higher acidic ion concentrations than JK. For SR and LG, the soil solution Ca/Al molar ratios are currently 0.3 in the rooting zone (A horizon), indicating Al toxicity. At SR, the simulated Ca/Al ratio increased to slightly above 1.5 after the 30-yr simulation regardless of S deposition reduction. At LG, Ca/Al ratios ranged from 1.6 to 2.4 toward the end of the simulation period, the 100% increase scenario had the lower value. Low Ca/Al ratios suggest that forests at SR and LG are significantly stressed under current conditions. Our results also suggest that SO(4) retention is low, perhaps contributing to their high degree of acidification. Their soils are acidic, low in weatherable minerals, and even with large reductions in SO(4) and associated acid deposition, it may take decades before these systems recover from depletion of exchangeable Ca, Mg, and K.  相似文献   
239.
Brownfields programmes provide environmental justice to distressed communities by applying private sector remediation and real estate expertise to abandoned and contaminated properties. This study examines how brownfields developers and community support organisations operating in socio-economically disadvantaged neighbourhoods work to increase awareness of projects in the community, build trust between stakeholders and create mechanisms for community members to participate in brownfields decision making. Analysis of case study data from brownfields sites in four US cities shows that developers and non-governmental organisations can play important roles in fashioning redevelopment outcomes which benefit both developers and communities. When standard required outreach efforts are combined with non-traditional community involvement mechanisms, the result is often long-term support for redevelopment projects.  相似文献   
240.
We introduce a generalized form of the common first-order (exponential) decay model, that has potential utility for describing contaminant declines in environmental applications, particularly when declines are a mixture of many underlying processes. The exponent on contaminant concentration is left as a free parameter allowing the order of the reaction to be determined by the data. The mixed-order model is more flexible than models with the exponent determined a priori, facilitating an improved fit to observed behavior. We demonstrate the utility of this model, and compare it to two other models, by estimating PCB concentration declines in Lake Michigan fishes.  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