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   247篇
  免费   3篇
  国内免费   3篇
安全科学   21篇
废物处理   10篇
环保管理   52篇
综合类   23篇
基础理论   66篇
污染及防治   54篇
评价与监测   20篇
社会与环境   7篇
  2023年   3篇
  2021年   4篇
  2019年   4篇
  2018年   2篇
  2017年   5篇
  2016年   5篇
  2015年   10篇
  2014年   1篇
  2013年   13篇
  2012年   8篇
  2011年   10篇
  2010年   5篇
  2009年   11篇
  2008年   10篇
  2007年   20篇
  2006年   17篇
  2005年   11篇
  2004年   11篇
  2003年   9篇
  2002年   10篇
  2001年   9篇
  2000年   5篇
  1999年   4篇
  1998年   2篇
  1997年   3篇
  1996年   6篇
  1995年   4篇
  1994年   2篇
  1993年   4篇
  1992年   6篇
  1991年   4篇
  1990年   2篇
  1989年   1篇
  1988年   2篇
  1987年   4篇
  1986年   1篇
  1985年   1篇
  1984年   3篇
  1983年   1篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1979年   3篇
  1978年   2篇
  1977年   1篇
  1976年   2篇
  1973年   2篇
  1972年   1篇
  1968年   1篇
  1966年   1篇
排序方式: 共有253条查询结果,搜索用时 15 毫秒
71.
The Superfund Innovative Technology Evaluation (SITE) program is a program mandated by Congress through the 1986 Superfund Amendments and Reauthorization Act (SARA). The original Superfund allowed no provisions for research and development of needed remediation technologies. Problems arose when the demand for involved, complex treatment could not be met by the traditional contain, haul, and dispose process that hazardous waste handlers had become familiar with. In response to the increasing complexity of hazardous waste site remediation, SARA called for an “Alternative or Innovative Treatment Technology Research and Demonstration Program.” As a result, EPA's Office of Solid Waste and Emergency Response and the Office of Research and Development established the SITE program. This article is a historical analysis of the unique cost savings of the SITE program.  相似文献   
72.
Considerable progress has been made during the past decade in the development of mechanistic models that allow complex chemical, physical, and biological processes to be evaluated in the global change context. However, quantitative predictions of the response of individual trees, stands, and forest ecosystems to pollutants and climatic variables require extrapolation of existing data sets, derived largely from seedling studies, to increasing levels of complexity with little or no understanding of the uncertainties associated with these extrapolations. Consequently, a project designed to address concerns associated with scaling from seedling to mature tree responses was initiated. During the 1990 and 1991 growing seasons, mature northern red oak (Quercus rubra L.) trees and seedlings were exposed to subambient, ambient, and twice ambient ozone (O(3)) concentrations. The initial focus of the study was to identify possible trends and obvious differences between mature trees and seedlings, both in terms of growth and physiology and in response to O(3). Generally, mature trees exhibited a greater decrease in photosynthesis rates over the growing season than did the seedlings. Ozone treatments had no consistent effect on gas exchange rates of seedlings, but the twice ambient O(3) treatment resulted in reduced photosynthesis rates in the mature tree. Despite no effect of O(3) on seedling gas exchange rates, total seedling biomass was significantly less at the end of the 1991 growing season for those seedlings exposed to twice ambient O(3) levels. Disproportionate reductions in root biomass also resulted in reduced root to shoot ratios at elevated O(3) concentrations.  相似文献   
73.
This paper represents an initial effort to explore the empirical relationship between business ideologies and perceptions of organizational downsizing. The results of four studies, two conducted in the US and one each in Singapore and Korea, suggest that respondents' belief in the ideology of employee self‐reliance reduces the degree to which they perceive layoffs as a breach of the psychological contract. This finding appears to generalize to respondents' perceptions of their own layoffs and also to respondents' perceptions of layoffs happening to others. We spell out the implications of these results for the evolving theory of the ideological foundations of perceptions of downsizing. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
74.
75.
The ‘Perfect Storm’ metaphor describes a combination of events that causes a surprising or dramatic impact. It lends an evolutionary perspective to how social-ecological interactions change. Thus, we argue that an improved understanding of how social-ecological systems have evolved up to the present is necessary for the modelling, understanding and anticipation of current and future social-ecological systems. Here we consider the implications of an evolutionary perspective for designing research approaches. One desirable approach is the creation of multi-decadal records produced by integrating palaeoenvironmental, instrument and documentary sources at multiple spatial scales. We also consider the potential for improved analytical and modelling approaches by developing system dynamical, cellular and agent-based models, observing complex behaviour in social-ecological systems against which to test systems dynamical theory, and drawing better lessons from history. Alongside these is the need to find more appropriate ways to communicate complex systems, risk and uncertainty to the public and to policy-makers.  相似文献   
76.
Steroids are essential for successful reproduction in all vertebrate species. Over the last several decades, extensive research has indicated that exposure to various environmental pollutants can disrupt steroidogenesis and steroid signaling. Although steroidogenesis is regulated by the hypothalamic-pituitary axis, it is also modified by various paracrine and autocrine factors. Furthermore, the classical two-cell model of steroidogenesis in the developing ovarian follicle, involving the granulosa and theca cells in mammals, may not be universal. Instead, birds and probably reptiles use the two thecal compartments (theca interna and theca externa) as sites of steroid production. We have documented that embryonic or juvenile exposure to a complex mixture of contaminants from agricultural and storm water runoff leads to altered steroid hormone profiles in American alligators. Our observations suggest that alterations in plasma steroid hormone concentrations are due in part to altered gene expression, modified hepatic biotransformation and altered gonadal steroidogenesis. Future studies must examine the interplay between endocrine and paracrine regulation in the development and expression of gonadal steroidogenesis in individuals exposed to endocrine disrupting contaminants at various life stages if we are to fully understand potential detrimental outcomes.  相似文献   
77.
There is a growing body of research about the etiology and prevention of falls. However, the persistently high incidence of falls among seniors calls for renewed efforts to develop, test, implement, and scale-up fall prevention strategies for older adults. This paper considers advances in the field and describes three priority areas for generating research and translating knowledge on fall prevention. Clinical practice guidelines, systems change approaches and environmental risk factors are discussed. Recommendations include transcending our health sector view of the fall prevention problem, supporting comparative research on system-oriented approaches to fall prevention, and examining ways to sustain and scale-up fall prevention efforts.  相似文献   
78.
Edwards KF  Klausmeier CA  Litchman E 《Ecology》2011,92(11):2085-2095
Trade-offs among functional traits are essential for explaining community structure and species coexistence. While two-way trade-offs have been investigated in many systems, higher-dimensional trade-offs remain largely hypothetical. Here we demonstrate a three-way trade-off between cell size and competitive abilities for nitrogen and phosphorus in marine and freshwater phytoplankton. At a given cell size, competitive abilities for N and P are negatively correlated, but as cell size increases, competitive ability decreases for both nutrients. The relative importance of the two trade-off axes appears to be environment dependent, suggesting different selective pressures: freshwater phytoplankton separate more along the N vs. P competition axis, and marine phytoplankton separate more along the nutrient competition vs. cell size axis. Our results demonstrate the multidimensional nature of key trade-offs among traits and suggest that such trade-offs may drive species interactions and structure ecological communities.  相似文献   
79.
Nature conservation organisations increasingly turn to new digital technologies to help deliver conservation objectives. This has led to collaborative forms of working with academia to spearhead digital innovation. Through in-depth interviews with three UK research-council-funded case studies, we show that by working with academics conservation organisations can receive positive and negative impacts, some of which cut across their operations. Positive impacts include new ways of engaging with audiences, improved data workflows, financial benefits, capacity building and the necessary digital infrastructure to help them influence policy. Negative impacts include the time and resources required to learn new skills and sustain new technologies, managing different organisational objectives and shifts in working practices as a result of the new technologies. Most importantly, collaboration with academics was shown to bring the opportunity of a profound change in perspectives on technologies with benefits to the partner organisations and individuals therein.  相似文献   
80.
Marine spatial planning is increasingly used to manage the demands on marine areas, both spatially and temporally, where several different users may compete for resources or space, to ensure that development is as sustainable as possible. Diminishing sea-ice coverage in the Arctic will allow for potential increases in economic exploitation, and failure to plan for cross-sectoral management could have negative economic and environmental results. During the ACCESS programme, a marine spatial planning tool was developed for the Arctic, enabling the integrated study of human activities related to hydrocarbon exploitation, shipping and fisheries, and the possible environmental impacts, within the context of the next 30 years of climate change. In addition to areas under national jurisdiction, the Arctic Ocean contains a large area of high seas. Resources and ecosystems extend across political boundaries. We use three examples to highlight the need for transboundary planning and governance to be developed at a regional level.  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