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   204篇
  免费   8篇
  国内免费   2篇
安全科学   23篇
废物处理   17篇
环保管理   40篇
综合类   20篇
基础理论   21篇
污染及防治   76篇
评价与监测   11篇
社会与环境   6篇
  2023年   3篇
  2021年   3篇
  2020年   4篇
  2019年   6篇
  2018年   6篇
  2017年   4篇
  2016年   6篇
  2015年   11篇
  2014年   4篇
  2013年   16篇
  2012年   14篇
  2011年   19篇
  2010年   11篇
  2009年   12篇
  2008年   13篇
  2007年   7篇
  2006年   12篇
  2005年   5篇
  2004年   2篇
  2003年   7篇
  2002年   1篇
  2001年   3篇
  2000年   8篇
  1999年   1篇
  1998年   1篇
  1997年   1篇
  1996年   3篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1992年   3篇
  1990年   2篇
  1987年   3篇
  1986年   2篇
  1982年   1篇
  1981年   2篇
  1978年   1篇
  1976年   2篇
  1975年   3篇
  1974年   2篇
  1973年   1篇
  1969年   2篇
  1968年   1篇
  1967年   2篇
  1958年   1篇
排序方式: 共有214条查询结果,搜索用时 15 毫秒
51.
Agenda 21 requires that countries adopt ‘national sustainable development strategies’ (NSDS), and this has been emphasized in several international commitments. Ghana has contributed to the methodology for peer review of such national strategies, as well as to guidelines designed by OECD and the United Nations for the NSDS process. Ghana has also adopted mechanisms to manage its own development planning in a sustainable manner. This article highlights various types of frameworks for sustainable development currently operating in Ghana, and considers to what extent they conform to NSDS principles. The article concludes that Ghana has made progress in several ways, but faces some of the same challenges as other countries in adhering to sustainability principles. The article offers recommendations as to how Ghana can achieve sustainable development. The article is an independent assessment by the author, who has also formulated most of the recommendations, except where otherwise indicated.  相似文献   
52.
Solid or sludgy hydrocarbon waste is a by-product of oil and gas exploration and production. One commonly used method of disposing of this waste is landfarming. Landfarming involves spreading hydrocarbon waste on soils, tilling it into the soil, and allowing it to biodegrade. We used a dynamic flux chamber to measure fluxes of methane, a suite of 54 nonmethane hydrocarbons, and light alcohols from an active and a remediated landfarm in eastern Utah. Fluxes from the remediated landfarm were not different from a polytetrafluoroethylene (PTFE) sheet or from undisturbed soils in the region. Fluxes of methane, total nonmethane hydrocarbons, and alcohols from the landfarm in active use were 1.41 (0.37, 4.19) (mean and 95% confidence limits), 197.90 (114.72, 370.46), and 4.17 (0.03, 15.89) mg m?2 hr?1, respectively. Hydrocarbon fluxes were dominated by alkanes, especially those with six or more carbons. A 2-ha landfarm with fluxes of the magnitude we observed in this study would emit 95.3 (54.3, 179.7) kg day?1 of total hydrocarbons, including 11.2 (4.3, 33.9) kg day?1 of BTEX (benzene, toluene, ethylbenzene, and xylenes).

Implications: Solid and sludgy hydrocarbon waste from the oil and gas industry is often disposed of by landfarming, in which wastes are tilled into soil and allowed to decompose. We show that a land farm in Utah emitted a variety of organic compounds into the atmosphere, including hazardous air pollutants and compounds that form ozone. We calculate that a 2-ha landfarm facility would emit 95.0 ± 66.0 kg day?1 of total hydrocarbons, including 11.1 ± 1.5 kg day?1 of BTEX (benzene, toluene, ethylbenzene, and xylenes).  相似文献   
53.
Spatial mapping of city-wide PBDE levels using an exponential decay model   总被引:1,自引:0,他引:1  
Passive air samplers (PAS) consisting of polyurethane foam (PUF) disks were deployed at 6 outdoor air monitoring stations in different land use categories (commercial, industrial, residential and semi-rural) to assess the spatial distribution of polybrominated diphenyl ethers (PBDEs) in the Brisbane airshed. Air monitoring sites covered an area of ~1143 km(2) and PAS were allowed to accumulate PBDEs in the city's airshed over three consecutive seasons commencing in the winter of 2008. The average sum of five (∑(5)) PBDEs (BDEs 28, 47, 99, 100 and 209) levels were highest at the commercial and industrial sites (12.7 ± 5.2 ng PUF(-1)), which were relatively close to the city center and were a factor of 8 times higher than residential and semi-rural sites located in outer Brisbane. To estimate the magnitude of the urban 'plume' an empirical exponential decay model was used to fit PAS data vs. distance from the CBD, with the best correlation observed when the particulate bound BDE-209 was not included (∑(5)-209) (r(2) = 0.99), rather than ∑(5) (r(2) = 0.84). At 95% confidence intervals the model predicts that regardless of site characterization, ∑(5)-209 concentrations in a PAS sample taken between 4-10 km from the city centre would be half that from a sample taken from the city centre and reach a baseline or plateau (0.6 to 1.3 ng PUF(-1)), approximately 30 km from the CBD. The observed exponential decay in ∑(5)-209 levels over distance corresponded with Brisbane's decreasing population density (persons/km(2)) from the city center. The residual error associated with the model increased significantly when including BDE-209 levels, primarily due to the highest level (11.4 ± 1.8 ng PUF(-1)) being consistently detected at the industrial site, indicating a potential primary source at this site. Active air samples collected alongside the PAS at the industrial air monitoring site (B) indicated BDE-209 dominated congener composition and was entirely associated with the particulate phase. This study demonstrates that PAS are effective tools for monitoring citywide regional differences however, interpretation of spatial trends for POPs which are predominantly associated with the particulate phase such as BDE-209, may be restricted to identifying 'hotspots' rather than broad spatial trends.  相似文献   
54.
55.
Quality assessment of water is essential to ensure sustainable safe use of it for drinking, agricultural, and industrial purposes. For the same purpose the study was conducted for the samples of water of Sambhar lake city and its adjoining areas. The standard methods of APHA were used to analysis 15 samples collected from hand pumps and tube wells of the specified area. The analytical results show higher concentration of total dissolved solids, electrical conductivity sodium, nitrate, sulfate, and fluoride, which indicate signs of deterioration but values of pH, calcium, magnesium, total hardness, and carbonate are within permissible limits as per WHO standards. From the Hill-piper trilinear diagram, it is observed that the majority of groundwater from sampling stations are sodium?Cpotassium?Cchloride?Csulfate type water. The values of sodium absorption ratio and electrical conductivity of the groundwater were plotted in the US salinity laboratory diagram for irrigation water. Only the one sample fall in C3S1 quality with high salinity hazard and low sodium hazard. Other samples fall in high salinity hazard and high sodium hazard. Chemical analysis of groundwater shows that mean concentration of cation is in order sodium > magnesium > calcium > potassium while for the anion it is chloride > bicarbonate > nitrate > sulfate.  相似文献   
56.
Organizational efforts to improve team effectiveness in crisis situations primarily have focused on team training initiatives and, to a lesser degree, on staffing teams with respect to members' ability, experience, and functional backgrounds. Largely neglected in these efforts is the emotional component of crises and, correspondingly, the notion of staffing teams with consideration for their affective makeup. To address this void, we examined the impact of team member dispositional positive affect (PA) on team crisis effectiveness and the role of felt negative emotion in transmitting that influence. A study of 21 nuclear power plant crews engaged in crisis training simulations revealed that homogeneity in PA, but not mean‐level PA, was associated with greater team effectiveness. Mediation analysis suggested that homogeneity in PA leads to greater team effectiveness by reducing the amount of negative emotions that team members experience during crises. Furthermore, homogeneity in PA compensated for lower mean‐level PA in predicting effectiveness. Discussion focuses on the implications of these findings for understanding and further exploring the importance of affective factors and especially team affective composition in team crisis performance. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
57.
A lot of attention has beenfocused on workers ‘ perceptions of workplace safety but relatively little or no research has been done on the impact of job satisfaction on safety climate. This study investigated this relationship. It also examined the relationships between job satisfaction and workers’ compliance with safety management policies and accident frequency. A positive association was found between job satisfaction and safety climate. Workers who expressed more satisfaction at their posts had positive perceptions of safety climate. Correspondingly, they were more committed to safety management policies and consequently registered a lower rate of accident involvement. The results were thus consistent with the notion that workers ‘ positive perceptions of organisational climate influence their perceptions of safety at the workplace. The findings, which have implications in the work environment, are discussed.  相似文献   
58.
We assessed the foraging habits of California sea lions, Zalophus californianus, from Isla Santa Margarita, BCS, Mexico, by analyzing δ13C and δ15N values of dentin collagen. Since dentin is deposited annually in growth layer groups (GLGs), it can be subsampled to construct ontogenetic isotopic profiles at the individual level. We drilled 20 canine teeth and obtained 141 samples for isotopic analysis that were assigned to age-specific categories from GLG-based estimated ages. Pups’ GLGs had the highest mean δ15N values and the lowest mean δ13C values, a pattern likely driven by the consumption of milk. Juveniles had δ15N values between those of pups and adult females, which may reflect continued nursing into the second year or preferential consumption of coastal benthic versus pelagic prey. Significant differences were observed between the sexes of adults; adult females had lower mean δ13C and δ15N values than adult males. Higher isotope values in adult males relative to females may reflect a higher trophic position, but differences in foraging grounds cannot be excluded as a potential explanation because tracking data are not available at this time. Evidence of intra-specific foraging diversification may be related to a strategy to reduce competition within and among age and sex categories.  相似文献   
59.
Evergreen and deciduous plants are widely expected to have different impacts on soil nitrogen (N) availability because of differences in leaf litter chemistry and ensuing effects on net N mineralization (N(min)). We evaluated this hypothesis by compiling published data on net N(min) rates beneath co-occurring stands of evergreen and deciduous trees. The compiled data included 35 sets of co-occurring stands in temperate and boreal forests. Evergreen and deciduous stands did not have consistently divergent effects on net N(min) rates; net N(min) beneath deciduous trees was higher when comparing natural stands (19 contrasts), but equivalent to evergreens in plantations (16 contrasts). We also compared net N(min) rates beneath pairs of co-occurring genera. Most pairs of genera did not differ consistently, i.e., tree species from one genus had higher net N(min) at some sites and lower net N(min) at other sites. Moreover, several common deciduous genera (Acer, Betula, Populus) and deciduous Quercus spp. did not typically have higher net N(min) rates than common evergreen genera (Pinus, Picea). There are several reasons why tree effects on net N(min) are poorly predicted by leaf habit and phylogeny. For example, the amount of N mineralized from decomposing leaves might be less than the amount of N mineralized from organic matter pools that are less affected by leaf litter traits, such as dead roots and soil organic matter. Also, effects of plant traits and plant groups on net N(min) probably depend on site-specific factors such as stand age and soil type.  相似文献   
60.
Deliberation over and relative preference for general or specific (broad or narrow) constructs has long been an important issue in organizational behavior research. In this article, we provide a review of this general issue and some specific recommendations for researchers. We begin by discussing whether the general versus specific issue is an important debate and by discussing other underlying issues (the role of researcher preferences, distinction between reflective and formative indicators, and distinction between constructs and measures of constructs). Building on Chen's (this issue) analysis of core self‐evaluations, we first discuss how the general–specific debate has progressed in core self‐evaluations research. We then discuss three other important areas in which this debate has played out: intelligence, five‐factor model of personality, and job attitudes. Finally, we offer a framework to help guide decisions about whether to utilize general measures, specific measures, or both and conclude by providing recommendations for the use of general and specific measures in organizational behavior research. Copyright © 2011 John Wiley & Sons, Ltd.  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