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   328篇
  免费   18篇
  国内免费   4篇
安全科学   8篇
废物处理   6篇
环保管理   60篇
综合类   59篇
基础理论   106篇
环境理论   3篇
污染及防治   49篇
评价与监测   32篇
社会与环境   22篇
灾害及防治   5篇
  2023年   8篇
  2022年   3篇
  2021年   10篇
  2020年   10篇
  2019年   16篇
  2018年   13篇
  2017年   18篇
  2016年   26篇
  2015年   16篇
  2014年   9篇
  2013年   24篇
  2012年   17篇
  2011年   18篇
  2010年   16篇
  2009年   15篇
  2008年   21篇
  2007年   14篇
  2006年   16篇
  2005年   10篇
  2004年   6篇
  2003年   7篇
  2002年   8篇
  2001年   5篇
  2000年   4篇
  1998年   4篇
  1997年   2篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1992年   1篇
  1990年   3篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1984年   2篇
  1979年   2篇
  1978年   1篇
  1975年   2篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
  1967年   1篇
  1966年   1篇
  1953年   1篇
  1918年   2篇
  1917年   1篇
  1914年   1篇
  1913年   2篇
排序方式: 共有350条查询结果,搜索用时 15 毫秒
81.
This study employed polyphasic chlorophyll a fluorescence transients (OJIP), a non-invasive marker of environmental stress in plants, to evaluate salt tolerance in three different Juncus roemerianus age classifications (6-, 24-, and 60-months). Following exposure to elevated salts (30 psu), the younger plants sustained growth, which was comparable to freshwater controls. While older (60-month) plants receiving only freshwater also grew over the 8-week study, the older salt-treated plants did not increase in size. Similarly, there were significant declines in variable chlorophyll a fluorescence parameters (F v/F m and F v/F o), electron transport flux per reaction center (ETo/RC), and photosystem II performance index (PIABS) for 60-month J. roemerianus following salt treatment. These responses were not evident in the two younger salt-treated age classifications. Our results suggest that older J. roemerianus are less tolerant to rapid and sudden increases in salinity relative to younger plants and that this age-specific response may help explain observed discrepancies in salt tolerance in J. roemerianus.  相似文献   
82.
83.
84.
Kannan K  Agusa T  Perrotta E  Thomas NJ  Tanabe S 《Chemosphere》2006,65(11):2160-2167
Infectious diseases have been implicated as a cause of high rates of adult mortality in southern sea otters. Exposure to environmental contaminants can compromise the immuno-competence of animals, predisposing them to infectious diseases. In addition to organic pollutants, certain trace elements can modulate the immune system in marine mammals. Nevertheless, reports of occurrence of trace elements, including toxic heavy metals, in sea otters are not available. In this study, concentrations of 20 trace elements (V, Cr, Mn, Co, Cu, Zn, Rb, Sr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, Hg, Tl, Pb, and Bi) were measured in livers of southern sea otters found dead along the central California coast (n = 80) from 1992 to 2002. Hepatic concentrations of trace elements were compared among sea otters that died from infectious diseases (n = 27), those that died from non-infectious causes (n = 26), and otters that died in emaciated condition with no evidence of another cause of death (n = 27). Concentrations of essential elements in sea otters varied within an order of magnitude, whereas concentrations of non-essential elements varied by two to five orders of magnitude. Hepatic concentrations of Cu and Cd were 10- to 100-fold higher in the sea otters in this study than concentrations reported for any other marine mammal species. Concentrations of Mn, Co, Zn, and Cd were elevated in the diseased and emaciated sea otters relative to the non-diseased sea otters. Elevated concentrations of essential elements such as Mn, Zn, and Co in the diseased/emaciated sea otters suggest that induction of synthesis of metallothionein and superoxide dismutase (SOD) enzyme is occurring in these animals, as a means of protecting the cells from oxidative stress-related injuries. Trace element profiles in diseased and emaciated sea otters suggest that oxidative stress mediates the perturbation of essential-element concentrations. Elevated concentrations of toxic metals such as Cd, in addition to several other organic pollutants, may contribute to oxidative stress-meditated effects in sea otters.  相似文献   
85.
Ecohealth is a process for identifying key environmental determinants causing mortality or morbidity and combating them by mobilizing multiple social sectors. Evolving out of the concept of environmental health, ecohealth provides a framework for long‐term sustainability. The health outcomes anticipated by environmental interventions are part of a long‐term agenda and require fundamental groundwork for the growth of community‐driven development. Building long‐term sustainability requires that two key approaches be developed through ecohealth. The first is the strengthening of local community institutions, whether formal or informal. The second is building financial mechanisms that are more diversified and less reliant on a single donor. As a result, the ecohealth system provides an opportunity for foundations to empower communities, build cross‐cutting cooperation, and gain knowledge through projects. If people's environmental behaviour is to change and be sustained in the long term to produce desired health outcomes, this will require all members of society to be capable of functioning within the existing institutional infrastructure. This means that not only do formal institutions need to become more accessible but also that concepts relating to local informal institutions must be incorporated into ecohealth projects. It is imperative that we identify and understand relevant local institutions and how they can be transformed so that new environmental forms of behaviour can be sustained and result in positive health outcomes. The intersection of environmental and health concerns provides an ideal area in which the gap between government and civil society can be bridged — not only providing solutions to ecohealth concerns, but building government capacity in general and making these positive changes sustainable in the long term. This article is a case study, based on several United Nations Foundation grants. It outlines the significance of traditional community organizations, the breadth of their long‐term relations with communities, their resources, and the adoption of sustained forms of behaviour. In addition, the article highlights the role that international foundations can play in creating innovative financing mechanisms through community‐based foundations.  相似文献   
86.
PROBLEM: Intentional and unintentional injury prevention efforts have traditionally been independent and non-integrated. Fostering collaboration between the sub-fields would enhance work within both sub-fields and advance injury prevention work as a whole. METHOD: A systematic assessment of similarities and differences between the sub-fields was performed, including an examination of relevant definitions and norms, research methods and findings, key risk and resiliency factors, and prevention strategies that would promote collaboration and better advance current prevention efforts. RESULTS/SUMMARY: Several areas exist in which injury prevention efforts could be coordinated or ideas and practices could be cross-applied, including training of practitioners, data collection and analysis, application of tools and methodologies, examination of risk and resiliency factors, and identification of funding sources and partners. IMPACT ON INDUSTRY: This paper delineates how intentional and unintentional injury prevention practitioners can more effectively collaborate to promote safer environments and further reduce incidence of injury. An integrated injury prevention approach could significantly impact the underlying contributors to both types of injury, allowing practitioners within both sub-fields to achieve greater outcomes through increased credibility, reduced duplication of efforts, more efficient use of resources, and unified injury prevention messages.  相似文献   
87.
ABSTRACT: A multivariate approach was used to analyze hydrologic, geologic, geographic, and water-chemistry data from small order watersheds in the Quabbin Reservoir Basin in central Massachusetts. Eighty three small order watersheds were delineated and landscape attributes defining hydrologic, geologic, and geographic features of the watersheds were compiled from geographic information system data layers. Principal components analysis was used to evaluate 11 chemical constituents collected bi-weekly for 1 year at 15 surface-water stations in order to subdivide the basin into subbasins comprised of watersheds with similar water quality characteristics. Three principal components accounted for about 90 percent of the variance in water chemistry data. The principal components were defined as a biogeochemical variable related to wet. land density, an acid-neutralization variable, and a road-salt variable related to density of primary roads. Three subbasins were identified. Analysis of variance and multiple comparisons of means were used to identify significant differences in stream water chemistry and landscape attributes among subbasins. All stream water constituents were significantly different among subbasins. Multiple regression techniques were used to relate stream water chemistry to landscape attributes. Important differences in landscape attributes were related to wetlands, slope, and soil type.  相似文献   
88.
The multiple and interlinked problems that plague most peri-urban communities can only be successfully addressed and resolved if roles and responsibilities of all actors in the urban setting are redistributed. This will require fundamental changes in the way municipalities work and define their accomplishments. Behaviour needs to change at all levels, beginning with public sector institutions responsible for communities. Without changes at the municipal level, requisite changes at the community level to remedy the root causes of environment-related illness, do not occur. Public sector institutions and communities, working as partners with clearly defined roles and responsibilities, and, most importantly, with mutual trust, can together make real progress toward improving health and well-being in peri-urban settlements. This article discusses two recent projects sponsored by the Environmental Health Project of the U.S. Agency for International Development (USAID): an 18-month pilot project to improve peri-urban environmental health in two cities in Tunisia, and a project in Ecuador to support the Ministry of Health in combating cholera in affected provinces. The following examples, methodology, and results may be useful to officials and donor organizations in designing environmental health projects.  相似文献   
89.
This paper synthesizes information on the spatial and temporal dynamics of wood in small streams in the Pacific Northwest region of North America. The literature on this topic is somewhat confused due to a lack of an accepted definition of what constitutes “small” streams and what is the relative size of woody debris contained within the channel. This paper presents a matrix that defines woody debris relative to channel size and then discusses the components of a wood budget. Headwater streams are in close proximity to wood sources and, in steeplands, are often tightly constrained by steep hillslopes. Special consideration is given to ecosystem characteristics and to management practices that affect the wood dynamics in this context. Knowledge gaps and uncertainties that can be used to guide future research are identified. Very little is currently known about the role of mass wasting in wood recruitment and storage relative to other processes, such as bank erosion and mortality, in larger streams. Further, very little work has addressed the relative importance of different wood depletion processes, especially those associated with wood transport. The effect of other ecosystem variables on wood dynamics locally across a watershed (from valley bottom to mountaintop) and regionally across the landscape (from maritime to continental climates) is not addressed. Finally, the scientific community has only begun to deal with the effects of management practices on wood quantity, structure, and movement in small streams.  相似文献   
90.
Per‐ and polyfluoroalkyl substances (PFAS) are highly resistant to biotic and abiotic degradation and can withstand very high temperatures before breaking down. The storage of PFAS‐impacted water and sediments in a holding pond or stockpiled investigation or remedial action‐derived waste is occurring on an increasing number of sites. The most common PFAS water treatment options include granular‐activated carbon and resins and the most common soil treatment options have been primarily limited to excavation, offsite incineration, and, in some cases, soil stabilization. An increasing number of states across the United States are establishing part per trillion PFAS guidance levels for drinking water. Removing PFAS from soils removes PFAS source impacts to groundwater. In this study, volatilization of PFAS from soil treated using in situ thermal heating is evaluated as a treatment method to achieve a high degree of PFAS removal from soils. The evaluation of temperatures needed to achieve removal is described. To minimize vapor treatment required for PFAS thermal remediation, a scrubber was incorporated into the treatment train to transfer PFAS to the liquid phase in a concentrated, low‐volume solution. Vapor‐liquid equilibrium behavior and the extent of PFAS volatilization from impacted soil over a range of temperatures were evaluated. Results showed that heating soil to 350°C and 400°C reduces PFAS soil concentrations by 99.91% and 99.998%, respectively. It was also confirmed that sulfonate‐based PFAS generally required higher temperatures for volatilization to occur than carboxylate‐based PFAS.  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