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   282篇
  免费   1篇
  国内免费   1篇
安全科学   4篇
废物处理   18篇
环保管理   57篇
综合类   54篇
基础理论   62篇
环境理论   1篇
污染及防治   66篇
评价与监测   10篇
社会与环境   9篇
灾害及防治   3篇
  2021年   4篇
  2020年   4篇
  2019年   9篇
  2017年   6篇
  2016年   6篇
  2015年   3篇
  2014年   5篇
  2013年   36篇
  2012年   14篇
  2011年   15篇
  2010年   8篇
  2009年   9篇
  2008年   11篇
  2007年   13篇
  2006年   12篇
  2005年   8篇
  2004年   8篇
  2003年   17篇
  2002年   8篇
  2001年   8篇
  2000年   7篇
  1999年   1篇
  1998年   5篇
  1997年   2篇
  1996年   3篇
  1995年   5篇
  1994年   3篇
  1993年   1篇
  1991年   3篇
  1990年   4篇
  1989年   3篇
  1988年   3篇
  1987年   1篇
  1986年   5篇
  1985年   6篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1980年   2篇
  1978年   4篇
  1976年   2篇
  1975年   1篇
  1974年   3篇
  1973年   2篇
  1972年   2篇
  1971年   1篇
  1968年   1篇
  1967年   1篇
  1966年   1篇
  1958年   1篇
排序方式: 共有284条查询结果,搜索用时 15 毫秒
1.
Molecular methods, including DNA probes, were used to identify and enumerate pathogenic Vibrio species in the Chesapeake Bay; our data indicated that Vibrio vulnificus exhibits seasonal fluctuations in number. Our work included a characterization of total microbial communities from the Bay; development of microarrays that identify and quantify the diversity of those communities; and observation of temporal changes in those communities. To identify members of the microbial community, we amplified the 16S rDNA gene from community DNA isolated from a biofilm sample collected from the Chesapeake Bay in February, 2000. The resultant 75 sequences were 95% or more similar to 7 species including two recently described Shewanella species, baltica and frigidimarina, that have not been previously isolated from the Chesapeake. When the genera of bacteria from biofilm after culturing are compared to those detected by subcloning amplified 16S fragments from community DNA, the cultured sample exhibited a strong bias. In oysters collected in February, the most common bacteria were previously unknown. Based on our 16S findings, we are developing microarrays to detect these and other microbial species in these estuarine communities. The microarrays will detect each species using four distinct loci, with the multiple loci serving as an internal control. The accuracy of the microarray will be measured using sentinel species such as Aeromonas species, Escherichia coli, and Vibrio vulnificus. Using microarrays, it should be possible to determine the annual fluctuations of bacterial species (culturable and non-culturable, pathogenic and non-pathogenic). The data may be applied to understanding patterns of environmental change; assessing the health of the Bay; and evaluating the risk of human illness associated with exposure to and ingestion of water and shellfish.  相似文献   
2.
The food-concentrating filter within the house of Oikopleura vanhoeffeni Lohmann consists of three layers, upper and lower fine-mesh layers and an intermediate coarse-mesh layer. The filter is a natural analogue of man-made tangential, or cross-flow, filters that are used to concentrate fine particulate and colloidal material by the exclusion of water. Flow analysis using video microscopy of O. vanhoeffeni, collected in 1989 and 1990 at Logy Bay, insular Newfoundland, indicates concentration of particles of 74 to 1089 times that of ambient seawater ( ,n=23), for individuals 1.8 to 5.4 mm long. The smallest individuals had the highest concentration factors. Flow through the house is predominately affected by viscous forces and values of Reynolds numbers are 1. Flow rates through the house of O. vanhoeffeni indicate a maximum filtration capacity of ca. 1.4 to 26 liters d-1 and clearance rates (assuming ca. 50% of the time is spent not actively pumping) of 0.7 to 13 liters d-1, depending on body size. The estimated thickness of the boundary layer around individual fibers of the food-concentrating filter is 0.08 m, which is less than the pore width. The estimated concentration factors suggest that colloidal and fine particulate material may aggregate into larger particles within the food-concentrating filter and food tube during feeding.  相似文献   
3.
Most of the world's children live in resource-poor countries where people are at a relatively high risk of exposure to catastrophic situations arising from conflict and natural disasters.(6) Given the potential social, psychological and psychiatric consequences of exposure to disaster, mental health and psychosocial support programmes are increasingly part of humanitarian aid. A minimum standard on mental and social aspects of health is included in the recently revised Humanitarian Charter and Minimum Standards in Disaster Response (Sphere Handbook) (Sphere Project, 2004). Most recommendations for mental health and psychosocial interventions in guidance documents are based on expert opinion rather than research. Consequently, interventions are being implemented without full understanding of their potential benefit or harm. This paper offers a child-focused review of the evidence for each of the interventions described as indicators for the Sphere standard on mental and social aspects of health. It suggests some, but limited, support for each of them. However, the evidence base needs substantial strengthening.  相似文献   
4.
Stakeholder analysis means many things to different people. Various methods and approaches have been developed in different fields for different purposes, leading to confusion over the concept and practice of stakeholder analysis. This paper asks how and why stakeholder analysis should be conducted for participatory natural resource management research. This is achieved by reviewing the development of stakeholder analysis in business management, development and natural resource management. The normative and instrumental theoretical basis for stakeholder analysis is discussed, and a stakeholder analysis typology is proposed. This consists of methods for: i) identifying stakeholders; ii) differentiating between and categorising stakeholders; and iii) investigating relationships between stakeholders. The range of methods that can be used to carry out each type of analysis is reviewed. These methods and approaches are then illustrated through a series of case studies funded through the Rural Economy and Land Use (RELU) programme. These case studies show the wide range of participatory and non-participatory methods that can be used, and discuss some of the challenges and limitations of existing methods for stakeholder analysis. The case studies also propose new tools and combinations of methods that can more effectively identify and categorise stakeholders and help understand their inter-relationships.  相似文献   
5.
Aluminium-based water treatment residual (Al-WTR) is the most widely generated residual from water treatment facilities worldwide. It is regarded as a by-product of no reuse potential and landfilled. This study assessed Al-WTR as potential phosphate-removing substrate in engineered wetlands. Results indicate specific surface area ranged from 28.0 m2 g−1 to 41.4 m2 g−1. X-ray Diffraction, Fourier transform infrared and energy-dispersive X-ray spectroscopes all indicate Al-WTR is mainly composed of amorphous aluminium which influences its phosphorus (P) adsorption capacity. The pH and electrical conductivity ranged from 5.9 to 6.0 and 0.104 dS m−1 to 0.140 dS m−1 respectively, showing that it should support plant growth. Batch tests showed adsorption maxima of 31.9 mg P g−1 and significant P removal was achieved in column tests. Overall, results showed that Al-WTR can be used for P removal in engineered wetlands and it carries the benefits of reuse of a by-product that promotes sustainability.  相似文献   
6.
7.
In this paper, we review recent data for brominated flame retardants (particularly BDEs, HBCD and TBBP-A) in samples from the European and Asian environments, including recent temporal trend studies. Research is active and we cite over 100 studies published during 2005-2007. Environmental compartments studied comprise the atmosphere, indoor and outdoor air, sewage sludges, soils and sediments and a variety of biological samples and food chains. Findings include that the lack of reference materials for use in analytical quality control and method validation identified earlier has been addressed, and certified concentrations are now available for a number of BDE congeners in six pre-existing and one new reference materials. BDE209 was certified in three samples of indoor dust. The analysis of BDE209 remains problematic, but suitable methods for its determination are available and need to be applied. The contamination of indoor environments with BFRs has been recognised as representing a significant uptake pathway, particularly via dust. Additional data for TBBP-A are needed from areas, where it is produced and used, primarily Asia, as the worst-case scenario. As a reactive flame retardant it is less likely to leach from finished products. Also, issues regarding the importance of e-waste recycling as a source of BFRs to the local populations and the local environment require urgent study, certainly in China and possibly elsewhere. Generally, trends show a levelling in concentrations of BDEs and increases in concentrations of HBCD wherever determined and BDE209 in Asia.  相似文献   
8.
Fast pyrolysis of chicken manure produced two biooils (Fractions I and II) and a residual char. All four materials were analyzed by chemical methods, 13C and 1H Nuclear Magnetic Resonance Spectrometry (13C and 1H NMR), and Fourier Transform Infrared Spectrosphotometry (FTIR). The char showed the highest C content and the highest aromaticity. Of the two biooils Fraction II was higher in C, yield and calorific value but lower in N than Fraction I. The S and ash content of the two biooil fractions were low. The Cross Polarization Magic Angle Spinning (CP-MAS) 13C NMR spectrum of the initial chicken manure showed it to be rich in cellulose, which was a major component of sawdust used as bedding material. Nuclear Magnetic Resonance (NMR) spectra of the two biooils indicated that Fraction I was less aromatic than Fraction II. Among the aromatics in the two biooils, we were able to tentatively identify N-heterocyclics like indoles, pyridines, and pyrazines. FTIR spectra were generally in agreement with the NMR data. FTIR spectra of both biooils showed the presence of both primary and secondary amides and primary amines as well as N-heterocyclics such as pyridines, quinolines, and pyrimidines. The FTIR spectrum of the char resembled that of the initial chicken manure except that the concentration of carbohydrates was lower.  相似文献   
9.
ABSTRACT

Time-series of daily mortality data from May 1992 to September 1995 for various portions of the seven-county Philadelphia, PA, metropolitan area were analyzed in relation to weather and a variety of ambient air quality parameters. The air quality data included measurements of size-classified PM, SO4 2-, and H+ that had been collected by the Harvard School of Public Health, as well as routine air pollution monitoring data. Because the various pollutants of interest were measured at different locations within the metropolitan area, it was necessary to test for spatial sensitivity by comparing results for different combinations of locations. Estimates are presented for single pollutants and for multiple-pollutant models, including gaseous pollutants and mutually exclusive components of PM (PM2.5 and coarse particles, SO4 2- and non-SO4 2- portions of total suspended particulate [TSP] and PM10), measured on the day of death and the previous day.

We concluded that associations between air quality and mortality were not limited to data collected in the same part of the metropolitan area; that is, mortality for one part may be associated with air quality data from another, not necessarily neighboring, part. Significant associations were found for a wide variety of gaseous and particulate pollutants, especially for peak O3. Using joint regressions on peak O3 with various other pollutants, we found that the combined responses were insensitive to the specific other pollutant selected. We saw no systematic differences according to particle size or chemistry. In general, the associations between daily mortality and air pollution depended on the pollutant or the PM metric, the type of collection filter used, and the location of sampling. Although peak O3 seemed to exhibit the most consistent mortality responses, this finding should be confirmed by analyzing separate seasons and other time periods.  相似文献   
10.
Stoeckel, James A., Jade Morris, Elizabeth Ames, David C. Glover, Michael J. Vanni, William Renwick, and María J. González, 2012. Exposure Times to the Spring Atrazine Flush Along a Stream-Reservoir System. Journal of the American Water Resources Association (JAWRA) 48(3): 616-634. DOI: 10.1111/j.1752-1688.2011.00633.x Abstract: We used enzyme-linked immunosorbent assay to examine reservoir-mediated shifts in spring to fall exposure of aquatic organisms to the spring atrazine pulse over four years in a Midwestern stream-reservoir system. Peak atrazine concentrations in the major inflowing stream exceeded 10 μg/l in all four years. The reservoir had a beneficial effect in two of four years by diluting atrazine below the 10 μg/l threshold. However, during the other two years, exposure times above 10 μg/l were approximately doubled in the reservoir compared to the major inflowing stream. Thresholds of 3 and 5 μg/l were exceeded during all four years in the reservoir. The uplake and downlake reservoir sites were four to five times more likely to exceed these thresholds and aquatic organisms were subjected to longer exposure times above these thresholds compared to the inflowing stream. Release of elevated atrazine concentrations from the reservoir extended exposure times in the outflowing stream. This effect was most pronounced just below the dam. Aquatic organisms upstream of the reservoir were most likely to experience acute exposures whereas organisms within and immediately downstream of the reservoir were more likely to experience chronic exposures. The ubiquity of reservoirs and the annual spring herbicide flush highlight the importance of considering the presence and relative location of reservoirs when assessing risk to aquatic communities as well as locations of drinking water intakes.  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