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471.
Yadong Li Jay B. Richardson R. Mark Bricka Xiaojun Niu Hongbin Yang Lin Li Arturo Jimenez 《Waste management (New York, N.Y.)》2009,29(7):2147-2150
In recent history the volume of electronic products purchased by consumers has dramatically escalated. As a result this has produced an ever-increasing electronic waste (E-waste) stream, which has generated concerns regarding the E-waste’s potential for adversely impacting the environment. The leaching of toxic substances from obsolete personal computers (PCs) and cathode ray tubes (CRTs) of televisions and monitors, which are the most significant components in E-waste stream, was studied using landfill simulation in columns. Five columns were employed. One column served as a control which was filled with municipal solid waste (MSW), two columns were filled with a mixture of MSW and CRTs, and the other two were filled with MSW and computer components including printed wire boards, hard disc drives, floppy disc drives, CD/DVD drives, and power supply units. The leachate generated from the columns was monitored for toxic materials throughout the two-year duration of the study. Results indicate that lead (Pb) and various other heavy metals that were of environmental and health concern were not detected in the leachate from the simulators. When the samples of the solids were collected from underneath the E-waste in the columns and were analyzed, significant amount of Pb was detected. This indicates that Pb could readily leach from the E-waste, but was absorbed by the solids around the E-waste materials. While Pb was not observed in the leachate in this study, it is likely that the Pb would eventually enter the leachate after a long term transport. 相似文献
472.
Johanna Riikonen Kevin E. Percy Mark E. Kubiske Elina Vapaavuori 《Environmental pollution (Barking, Essex : 1987)》2010,158(4):1029-1035
Betula papyrifera trees were exposed to elevated concentrations of CO2 (1.4 × ambient), O3 (1.2 × ambient) or CO2 + O3 at the Aspen Free-air CO2 Enrichment Experiment. The treatment effects on leaf surface characteristics were studied after nine years of tree exposure. CO2 and O3 increased epidermal cell size and reduced epidermal cell density but leaf size was not altered. Stomatal density remained unaffected, but stomatal index increased under elevated CO2. Cuticular ridges and epicuticular wax crystallites were less evident under CO2 and CO2 + O3. The increase in amorphous deposits, particularly under CO2 + O3, was associated with the appearance of elongated plate crystallites in stomatal chambers. Increased proportions of alkyl esters resulted from increased esterification of fatty acids and alcohols under elevated CO2 + O3. The combination of elevated CO2 and O3 resulted in different responses than expected under exposure to CO2 or O3 alone. 相似文献
473.
Mark H. Garnett Iain P. Hartley 《Atmospheric environment (Oxford, England : 1994)》2010,44(7):877-883
Radiocarbon (14C) analysis of atmospheric CO2 can provide information on CO2 sources and is potentially valuable for validating inventories of fossil fuel-derived CO2 emissions to the atmosphere. We tested zeolite molecular sieve cartridges, in both field and laboratory experiments, for passively collecting atmospheric CO2. Cartridges were exposed to the free atmosphere in two configurations which controlled CO2 trapping rate, allowing collection of sufficient CO2 in between 1.5 and 10 months at current levels. 14C results for passive samples were within measurement uncertainty of samples collected using a pump-based system, showing that the method collected samples with 14C contents representative of the atmosphere. δ13C analysis confirmed that the cartridges collected representative CO2 samples, however, fractionation during passive trapping means that δ13C values need to be adjusted by an amount which we have quantified. Trapping rate was proportional to atmospheric CO2 concentration, and was not affected by exposure time unless this exceeded a threshold. Passive sampling using molecular sieve cartridges provides an easy and reliable method to collect atmospheric CO2 for 14C analysis. 相似文献
474.
475.
This study examined the time series pattern of employment growth and stability in Fort Worth, Texas taking into account the March 28, 2000 tornado. The tornado is treated econometrically as an intervention and both the mean and conditional variance of employment growth were estimated. Overall, this regional labor market experienced a decline in the employment growth rate following the tornado. Among the sectors that exhibited differences in employment dynamics between the pre- and post-tornado periods, the mining sector experienced a significant increase in employment growth following the tornado while the service andwholesale, retail trade sectors experienced significant declines in employment growth in the post-tornado period. The manufacturing, service, and wholesale, retail trade sectors were characterized by greater stability (i.e., a lower level of employment growth volatility) in the post-tornado period than in the pre-tornado period. Interestingly, in several sectors, no differences in the time series dynamics of employment growth were detected between the pre- and post-tornado periods. These sectors included construction, finance, insurance, real estate, government, and transportation and public utilities. 相似文献
476.
Air quality is declining in urban areas, in part because of the rapid motorization of societies world-wide. To combat the problem, various pollution control strategies have been used or proposed for urban passenger transport. This paper develops a simple framework to analyse the impact of these strategies. The paper examines the point of impact of different policy levers and categorizes different instruments in a way that should help policy makers choose between them. The framework explicitly recognizes behavioural incentives, especially the fact that offsetting changes in consumer behaviour can often undermine the original intent of particular policies. The paper concludes that policies aimed at improving transport efficiency often improve air quality at the same time. However, supply side policies to relieve traffic congestion can conflict with the objective of controlling air pollution. It is hence vital that policy makers are aware of the incentives created by different interventions and weigh the impact of these incentives on subsidiary objectives before adoption of particular policies. 相似文献
477.
478.
Forest and agroecosystem fire management in Ghana 总被引:1,自引:0,他引:1
Mark Appiah Lawrence Damnyag Dominic Blay Ari Pappinen 《Mitigation and Adaptation Strategies for Global Change》2010,15(6):551-570
The threat of wildfires to the economic potential of forestry and agriculture is one of the persistent national and international
concerns. Improving and applying indigenous wildfire management (IWM) approaches is seen as one of the main hopes for mitigating
and adapting to this threat to rural forest communities. Identifying the contextual causes and adaptation measures practiced
by local people is essential for planning an appropriate mechanism for IWM. Yet only limited studies are available on IWM
practices and most of those studies were conducted outside of this study region. To fill this gap, this study examined the
wildfire mitigation and adaptation methods of forest communities in Ghana using interviews with 266 farming households. Their
perceptions of the causes, cost and risk factors were also examined. The result suggests that wildfires are annual events.
More than half of the wildfires reported were caused by slash-and-burn land preparation, with hunting-related fires in second
place. Forest households loose about 208 Ghana cedi (US$ 231 in 2006) in value due to damaged crops and tree seedlings annually
(i.e. about 50% of annual income of a Ghanaian farmer). The respondents had the operational skill and coping abilities to
deal with small-scale wildfires and were supported by well-established local arrangements, community rules and silvicutural
techniques. In addition, they were well informed about the basic risk factors (e.g. fuel load, climate, and presence of ignition
triggers) and how these can interact to cause devastating wildfire. Therefore it is critical that policies and institutions
that promote IWM initiatives build on the strong underlying community knowledge and local networks to enhance their effectiveness. 相似文献
479.
480.