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91.
Emo Chiellini Andrea Corti Salvatore D’Antone Norman C. Billingham 《Journal of Polymers and the Environment》2007,15(3):169-178
Most of the standardized biodegradation tests used to assess the ultimate biodegradation of environmentally degradable polymers
are based solely on the determination of net evolved carbon dioxide. However, under aerobic conditions, it has to be considered
that heterotrophic microbial consortia metabolize carbon substrates both to carbon dioxide and in the production of new cell
biomass. It is generally accepted that in the relatively short term, 50% of the carbon content of most organic substrates
is converted to CO2, with the remaining carbon being assimilated as biomass or incorporated into humus. The latter is particularly important
when the metabolism of the organic matter occurs in a soil environment. A straightforward relationship between the free-energy
content of a carbon substrate (expressed as the standard free-energy of combustion) and its propensity for conversion to new
microbial biomass rather than mineralization to CO2 has been established. This can potentially lead to underestimation of biodegradation levels of test compounds, especially
when they consist of carbon in a fairly low formal oxidation state and relatively high free-energy content. In the present
work, the metabolism of different kind of carbon substrates, especially in soil, is reviewed and compared with our own experimental
results from respirometric tests. The results show that conversion of highly oxidized materials, such as the commonly used
reference materials, cellulose or starch, to CO2 may be significantly overestimated. The addition of glucosidic material to soil leads to greatly increased respiration and
is accompanied by a very low conversion to biomass or humic substances. In contrast, relatively less oxidized substrates metabolize
more slowly to give both CO2 and biomass to an extent which may be significantly underestimated if glucosidic materials are used as the reference. The
need for an overall carbon balance taking into account both the carbon immobilized as biomass and that volatized as CO2 must be considered in standard respirometric procedures for assessing the biodegradability of slowly degrading macromolecules. 相似文献
92.
/ To understand the total impact of humans on the carbon cycle, themodeling and quantifying of the transfer of carbon from terrestrial pools tothe atmosphere is becoming more critical. Using previously published data,this research sought to assess the change in carbon pools caused by humans inthe Lower Fraser Basin (LFB) in British Columbia, Canada, since 1827 anddefine the long-term, regional contribution of carbon to the atmosphere. Theresults indicate that there has been a transfer of 270 Mt of carbon frombiomass pools in the LFB to other pools, primarily the atmosphere. The majorlosses of biomass carbon have been from logged forests (42%), wetlands(14%), and soils (43%). Approximately 48% of the forestbiomass, almost 20% of the carbon of the LFB, lies within old-growthforest, which covers only 19% of the study area. Landfills are nowbecoming a major sink of carbon, containing 5% of the biomass carbonin the LFB, while biomass carbon in buildings, urban vegetation, mammals, andagriculture is negligible. Approximately 26% of logged forest biomasswould still be in a terrestrial biomass pool, leaving 238 Mt of carbon thathas been released to the atmosphere. On an area basis, this is 29 times theaverage global emissions of carbon, providing an indication of the pastcontributions of developed countries such as Canada to global warming andpossible contributions from further clearing of rainforest in both tropicaland temperate regions.KEY WORDS: Carbon pools; Global warming; Carbon release to atmosphere;Greenhouse effect 相似文献
93.
It was found that the total adsorptive capacity of activated carbon was enhanced by using a multicomponent solution with glucose, peptone and phenylphosphonic acid. A maximum use of the carbon adsorptive capacity is possible if the carbon is used for tertiary treatment followed by treating a stronger waste. 相似文献
94.
In Great Britain, advice on land-use planning decisions in the vicinity of major hazard sites and pipelines is provided to Local Planning Authorities by the Health and Safety Executive (HSE), based on quantified risk assessments of the risks to the public in the event of an accidental release. For potential exposures to toxic substances, the hazard and risk is estimated by HSE on the basis of a “toxic load”. For carbon dioxide (CO2), this is calculated from the time-integral of the gas concentration to the power eight. As a consequence of this highly non-linear dependence of the toxic load on the concentration, turbulent concentration fluctuations that occur naturally in jets or plumes of CO2 may have a significant effect on the calculated hazard ranges. Most dispersion models used for QRA only provide estimates of the time- or ensemble-averaged concentrations. If only mean concentrations are used to calculate the toxic load, and the effects of concentration fluctuations are ignored, there is a danger that toxic loads and hence hazard ranges will be significantly under-estimated.This paper explores a simple and pragmatic modification to the calculation procedure for CO2 toxic load calculations. It involves the assumption that the concentration fluctuates by a factor of two with a prescribed square-wave variation over time. To assess the validity of this methodology, two simple characteristic flows are analysed: the free jet and the dense plume (or gravity current). In the former case, an empirical model is used to show that the factor-of-two approach provides conservative estimates of the hazard range. In the latter case, a survey of the literature indicates that there is at present insufficient information to come to any definite conclusions.Recommendations are provided for future work to investigate the concentration fluctuation behaviour in dense CO2 plumes. This includes further analysis of existing dense gas dispersion data, measurements of concentration fluctuations in ongoing large-scale CO2 release experiments, and numerical simulations. 相似文献
95.
We exploit recent advances in climate science to develop a physically consistent, yet surprisingly simple, model of climate policy. It seems that key economic models have greatly overestimated the delay between carbon emissions and warming, and ignored the saturation of carbon sinks that takes place when the atmospheric concentration of carbon dioxide rises. This has important implications for climate policy. If carbon emissions are abated, damages are avoided almost immediately. Therefore it is optimal to reduce emissions significantly in the near term and bring about a slow transition to optimal peak warming, even if optimal steady-state/peak warming is high. The optimal carbon price should start relatively high and grow relatively fast. 相似文献
96.
Gang Yi Xinfei Fan Xie Quan Shuo Chen Hongtao Yu 《Frontiers of Environmental Science & Engineering》2019,13(2):23
97.
Ancillary benefits of reduced air pollution in the US from moderate greenhouse gas mitigation policies in the electricity sector 总被引:3,自引:0,他引:3
Dallas Burtraw Alan Krupnick Karen Palmer Anthony Paul Michael Toman Cary Bloyd 《Journal of Environmental Economics and Management》2003,45(3):650
Actions to slow atmospheric accumulation of greenhouse gases also would reduce conventional air pollutants yielding “ancillary” benefits that tend to accrue locally and in the near-term. Using a detailed electricity model linked to an integrated assessment framework to value changes in human health, we find a tax of $25 per metric ton of carbon emissions would yield NOx-related health benefits of about $8 per metric ton of carbon reduced in the year 2010 (1997 dollars). Additional savings of $4–$7 accrue from reduced investment in NOx and SO2 abatement in order to comply with emission caps. Total ancillary benefits of a $25 carbon tax are $12–$14, which appear to justify the costs of a $25 tax, although marginal benefits are less than marginal costs. At a tax of $75, greater total benefits are achieved but the value per ton of carbon reductions remains roughly constant at about $12. 相似文献
98.
R. D. Diab S. J. Foster K. François B. S. Martincigh L. F. Salter 《Environmental Chemistry Letters》2005,3(2):91-94
Reliable measurements of pollutant levels in the vicinity of a toll plaza appear to be rare. In order to assess the exposure
of toll booth operators to carbon monoxide, a continuous carbon monoxide monitor was installed at head height in the booth
of a medium density traffic lane at the Mariannhill toll plaza, situated on a busy highway near Durban, South Africa. Measurements
in excess of 500 ppmv were recorded and the high daily mean carbon monoxide concentrations may account for some of the symptoms
such as headaches and general malaise that have been reported by workers in the booths. Generally, carbon monoxide levels
recorded far exceed the recommended limit set by the South African authorities. These results have led to recommendations
regarding the structure of new and existing toll booths to minimize the exposure of toll booth workers to adverse effects
of vehicle-emitted pollutants. 相似文献
99.
通过对一氧化碳危害性的论述,说明了环境中对一氧化碳浓度进行监测的必要性。对基于一氧化碳的理化性质进行的几种检测技术及在此基础上开发的监测仪器,设备进行了分析、比较,阐述了一氧化碳监测技术的现状。 相似文献
100.
Baselines for land-use change in the tropics: application to avoided deforestation projects 总被引:2,自引:0,他引:2
Sandra Brown Myrna Hall Ken Andrasko Fernando Ruiz Walter Marzoli Gabriela Guerrero Omar Masera Aaron Dushku Ben DeJong Joseph Cornell 《Mitigation and Adaptation Strategies for Global Change》2007,12(6):1001-1026
Although forest conservation activities, particularly in the tropics, offer significant potential for mitigating carbon (C)
emissions, these types of activities have faced obstacles in the policy arena caused by the difficulty in determining key
elements of the project cycle, particularly the baseline. A baseline for forest conservation has two main components: the
projected land-use change and the corresponding carbon stocks in applicable pools in vegetation and soil, with land-use change
being the most difficult to address analytically. In this paper we focus on developing and comparing three models, ranging
from relatively simple extrapolations of past trends in land use based on simple drivers such as population growth to more
complex extrapolations of past trends using spatially explicit models of land-use change driven by biophysical and socioeconomic
factors. The three models used for making baseline projections of tropical deforestation at the regional scale are: the Forest
Area Change (FAC) model, the Land Use and Carbon Sequestration (LUCS) model, and the Geographical Modeling (GEOMOD) model.
The models were used to project deforestation in six tropical regions that featured different ecological and socioeconomic
conditions, population dynamics, and uses of the land: (1) northern Belize; (2) Santa Cruz State, Bolivia; (3) Paraná State,
Brazil; (4) Campeche, Mexico; (5) Chiapas, Mexico; and (6) Michoacán, Mexico.
A comparison of all model outputs across all six regions shows that each model produced quite different deforestation baselines.
In general, the simplest FAC model, applied at the national administrative-unit scale, projected the highest amount of forest
loss (four out of six regions) and the LUCS model the least amount of loss (four out of five regions). Based on simulations
of GEOMOD, we found that readily observable physical and biological factors as well as distance to areas of past disturbance
were each about twice as important as either sociological/demographic or economic/infrastructure factors (less observable)
in explaining empirical land-use patterns.
We propose from the lessons learned, a methodology comprised of three main steps and six tasks can be used to begin developing
credible baselines. We also propose that the baselines be projected over a 10-year period because, although projections beyond
10 years are feasible, they are likely to be unrealistic for policy purposes. In the first step, an historic land-use change
and deforestation estimate is made by determining the analytic domain (size of the region relative to the size of proposed
project), obtaining historic data, analyzing candidate baseline drivers, and identifying three to four major drivers. In the
second step, a baseline of where deforestation is likely to occur–a potential land-use change (PLUC) map—is produced using
a spatial model such as GEOMOD that uses the key drivers from step one. Then rates of deforestation are projected over a 10-year
baseline period based on one of the three models. Using the PLUC maps, projected rates of deforestation, and carbon stock
estimates, baseline projections are developed that can be used for project GHG accounting and crediting purposes: The final
step proposes that, at agreed interval (e.g., about 10 years), the baseline assumptions about baseline drivers be re-assessed.
This step reviews the viability of the 10-year baseline in light of changes in one or more key baseline drivers (e.g., new
roads, new communities, new protected area, etc.). The potential land-use change map and estimates of rates of deforestation
could be re-done at the agreed interval, allowing the deforestation rates and changes in spatial drivers to be incorporated
into a defense of the existing baseline, or the derivation of a new baseline projection. 相似文献