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801.
Throughout 2004, PM(10) concentrations were measured at 10 min intervals at Hazelrigg, a remote location in NW England. The annual mean concentration was 6.1 microg m(-3) and likely origins were determined using directional and particle size characteristics. The fine temporal resolution of the monitoring also allowed several short periods (< 20 h) of persistently high PM(10) concentration to be identified and then 'typed' by event start time, duration, wind direction and particle size characteristics. A series of night time PM(10) anomalies (concentration < 465 microg m(-3)) of no obvious source were identified, and by elimination assumed to have originated from a ground-based fire of particle-rich fodder. A novel methodology combining Stokes' Law with systematic and rigorous modelling of source strength (using ADMS3.2) was developed to locate a possible burn site. The process was limited by the lack of previous modelling studies related to ground-based fires, and also by the capacity of ADMS3.2 to model sub-hourly time-varying emissions and fluctuations in wind speed and direction in the near field. However, modelling did suggest the source was located <400 m SSE of Hazelrigg, and investigation of this area revealed a burn site where tyres and plastic bags were piled nearby. Few studies have combined directional analysis and modelling to locate a source based on sampled data. This innovative methodology could be used by regulatory bodies to investigate the origins of unidentified PM(10) observed within the particle record. 相似文献
802.
Buma B 《Environmental monitoring and assessment》2012,184(6):3849-3860
Forest disturbances around the world have the potential to alter forest type and cover, with impacts on diversity, carbon
storage, and landscape composition. These disturbances, especially fire, are common and often large, making ground investigation
of forest recovery difficult. Remote sensing offers a means to monitor forest recovery in real time, over the entire landscape.
Typically, recovery monitoring via remote sensing consists of measuring vegetation indices (e.g., NDVI) or index-derived metrics,
with the assumption that recovery in NDVI (for example) is a meaningful measure of ecosystem recovery. This study tests that
assumption using MODIS 16-day imagery from 2000 to 2010 in the area of the Colorado’s Routt National Forest Hinman burn (2002)
and seedling density counts taken in the same area. Results indicate that NDVI is rarely correlated with forest recovery,
and is dominated by annual and perennial forb cover, although topography complicates analysis. Utility of NDVI as a means
to delineate areas of recovery or non-recovery are in doubt, as bootstrapped analysis indicates distinguishing power only
slightly better than random. NDVI in revegetation analyses should carefully consider the ecology and seasonal patterns of
the system in question. 相似文献
803.
DeLorenzo ME Thompson B Cooper E Moore J Fulton MH 《Environmental monitoring and assessment》2012,184(1):343-359
Stormwater ponds are commonly used in residential and commercial areas to control flooding. The accumulation of urban contaminants
in stormwater ponds can lead to water-quality problems including nutrient enrichment, chemical contamination, and bacterial
contamination. This study presents 5 years of monitoring data assessing water quality of a residential subdivision pond and
adjacent tidal creek in coastal South Carolina, USA. The stormwater pond is eutrophic, as described by elevated concentrations
of chlorophyll and phosphorus, and experiences periodic cyanobacterial blooms. A maximum monthly average chlorophyll concentration
of 318.75 μg/L was measured in the stormwater pond and 227.63 μg/L in the tidal creek. Fecal coliform bacteria (FCB) levels
were measured in both the pond and the tidal creek that exceeded health and safety standards for safe recreational use. A
maximum monthly average FCB level of 1,247 CFU/100 mL was measured in the stormwater pond and 12,850 CFU/100 mL in the tidal
creek. In addition, the presence of antibiotic resistant bacteria and pathogenic bacteria were detected. Low concentrations
of herbicides (atrazine and 2,4-D), a fungicide (chlorothalonil), and insecticides (pyrethroids and imidacloprid) were measured. Seasonal trends were identified,
with the winter months having the lowest concentrations of chlorophyll and FCB. Statistical differences between the stormwater
pond and the tidal creek were also noted within seasons. The tidal creek had higher FCB levels than the stormwater pond in
the spring and summer, whereas the stormwater pond had higher chlorophyll levels than the tidal creek in the summer and fall
seasons. Chlorophyll and FCB levels in the stormwater pond were significantly correlated with monthly average temperature
and total rainfall. Pesticide concentrations were also significantly correlated with temperature and rainfall. Pesticide concentrations
in the stormwater pond were significantly correlated with pesticide concentrations in the adjacent tidal creek. Chlorophyll
and FCB levels in the tidal creek, however, were not significantly correlated with levels in the pond. While stormwater ponds
are beneficial in controlling flooding, they may pose environmental and human health risks due to biological and chemical
contamination. Management to reduce residential runoff may improve water quality in coastal stormwater ponds and their adjacent
estuarine ecosystems. 相似文献
804.
Haibo Niu Adam Drozdowski Tahir Husain Brian Veitch Neil Bose Kenneth Lee 《Environmental Modeling and Assessment》2009,14(5):585-594
The benthic boundary layer transport (bblt) model was widely used in the Atlantic Canadian offshore region to assess the potential
impact zones from drilling wastes discharges from offshore oil and gas drilling. The current version of the bblt uses a single-class
settling velocity scenario, which may affect its performance, as settling velocity is size, shape, and material dependent.
In this study, the effects of settling velocity on bblt predictions were assessed by replacing this single-class settling
velocity scenario with a multi-class size-dependent settling velocity scenario. The new scenario was used in a hypothetical
study to simulate the dispersion of barite and fine-grained drilling cuttings. The study showed that the effects of settling
velocity on bblt predictions are spatial, temporal, and material dependent. 相似文献
805.
Annette Dathe Yuniati Zevi Brian K. Richards Bin Gao J.-Yves Parlange Tammo S. Steenhuis 《Environmental science and pollution research international》2014,21(15):9067-9080
Spectral confocal microscope visualizations of microsphere movement in unsaturated porous media showed that attachment at the Air Water Solid (AWS) interface was an important retention mechanism. These visualizations can aid in resolving the functional form of retention rates of colloids at the AWS interface. In this study, soil adsorption isotherm equations were adapted by replacing the chemical concentration in the water as independent variable by the cumulative colloids passing by. In order of increasing number of fitted parameters, the functions tested were the Langmuir adsorption isotherm, the Logistic distribution, and the Weibull distribution. The functions were fitted against colloid concentrations obtained from time series of images acquired with a spectral confocal microscope for three experiments performed where either plain or carboxylated polystyrene latex microspheres were pulsed in a small flow chamber filled with cleaned quartz sand. Both moving and retained colloids were quantified over time. In fitting the models to the data, the agreement improved with increasing number of model parameters. The Weibull distribution gave overall the best fit. The logistic distribution did not fit the initial retention of microspheres well but otherwise the fit was good. The Langmuir isotherm only fitted the longest time series well. The results can be explained that initially when colloids are first introduced the rate of retention is low. Once colloids are at the AWS interface they act as anchor point for other colloids to attach and thereby increasing the retention rate as clusters form. Once the available attachment sites diminish, the retention rate decreases. 相似文献
806.
807.
Sonia R. Peter Kerry M. Peru Brian Fahlman Dena W. McMartin John V. Headley 《Journal of environmental science and health. Part. B》2013,48(11):819-826
As part of an exchange technology program between the government of Barbados and Environment Canada, methanolic and aqueous extracts from the flavonoid-rich Lamiaceae family were characterized using negative-ion electrospray mass spectrometry. The species investigated is part of the Caribbean Pharmacopoeia, and is used for a variety of health issues, including colds, flu, diabetes, and hypertension. The extracts were investigated for structural elucidation of phenolics, identification of chemical taxonomic profile, and evidence of bio-accumulator potential. The methanolic and aqueous leaf extracts of Plectranthus amboinicus yielded rosmarinic acid, ladanein, cirsimaritin, and other methoxylated flavonoids. This genus also shows a tendency to form conjugates with monosaccharides, including glucose, galactose, and rhamnose. The aqueous extract yielded four isomeric rhamnosides. The formation of conjugates by Plectranthus amboinicus is thus evidence of high bioaccumulator significance. 相似文献
808.
Beverley Hale-Marie Ron G. Dutton O. Brian Allen Douglas P. Ormrod S. Norman Goodyear Larry G. Pyear 《Journal of the Air & Waste Management Association (1995)》2013,63(4):460-463
Abstract Landfills represent a source of distributed emissions source over an irregular and heterogeneous surface. In the method termed “Other Test Method-10” (OTM-10), the U.S. Environmental Protection Agency (EPA) has proposed a method to quantify emissions from such sources by the use of vertical radial plume mapping (VRPM) techniques combined with measurement of wind speed to determine the average emission flux per unit area per time from nonpoint sources. In such application, the VRPM is used as a tool to estimate the mass of the gas of interest crossing a vertical plane. This estimation is done by fitting the field-measured concentration spatial data to a Gaussian or some other distribution to define a plume crossing the vertical plane. When this technique is applied to landfill surfaces, the VRPM plane may be within the emitting source area itself. The objective of this study was to investigate uncertainties associated with using OTM-10 for landfills. The spatial variability of emission in the emitting domain can lead to uncertainties of –34 to 190% in the measured flux value when idealistic scenarios were simulated. The level of uncertainty might be higher when the number and locations of emitting sources are not known (typical field conditions). The level of uncertainty can be reduced by improving the layout of the VRPM plane in the field in accordance with an initial survey of the emission patterns. The change in wind direction during an OTM-10 testing setup can introduce an uncertainty of 20% of the measured flux value. This study also provides estimates of the area contributing to flux (ACF) to be used in conjunction with OTM-10 procedures. The estimate of ACF is a function of the atmospheric stability class and has an uncertainty of 10–30%. 相似文献
809.
Stuart M. Dalton Barbara Toole-O’Neil Brian K. Gullett Charles J. Drummond 《Journal of the Air & Waste Management Association (1995)》2013,63(8):1110-1117
The 1991 SO2 Control Symposium was held December 3-6, 1991, in Washington, D.C. The symposium, jointly sponsored by the Electric Power Research Institute (EPRI), the U.S. Environmental Protection Agency (EPA), and the U.S. Department of Energy (DOE), focused attention on recent improvements in conventional sulfur dioxide (SO2) control technologies, emerging processes, and strategies for complying with the Clean Air Act Amendments of 1990. Its purpose was to provide a forum for the exchange of technical and regulatory information on SO2 control technology. Over 800 representatives of 20 countries from government, academia, flue gas desulfurization (FGD) process suppliers, equipment manufacturers, engineering firms, and utilities attended. In all, 50 U.S. utilities and 10 utilities in other countries were represented. In 11 technical sessions, a diverse group of speakers presented 111 technical papers on development, operation, and commercialization of wet and dry FGD, Clean Coal Technologies, and combined sulfur dioxide/nitrogen oxides (SO2/NOx processes. 相似文献
810.
Edward G. Nagato Jessica C. D’eon Brian P. Lankadurai David G. Poirier Eric J. Reiner Andre J. Simpson Myrna J. Simpson 《Chemosphere》2013
Metal and metalloid contamination constitutes a major concern in aquatic ecosystems. Thus it is important to find rapid and reliable indicators of metal stress to aquatic organisms. In this study, we tested the use of 1H nuclear magnetic resonance (NMR) – based metabolomics to examine the response of Daphnia magna neonates after a 48 h exposure to sub-lethal concentrations of arsenic (49 μg L−1), copper (12.4 μg L−1) or lithium (1150 μg L−1). Metabolomic responses for all conditions were compared to a control using principal component analysis (PCA) and metabolites that contributed to the variation between the exposures and the control condition were identified and quantified. The PCA showed that copper and lithium exposures result in statistically significant metabolite variations from the control. Contributing to this variation was a number of amino acids such as: phenylalanine, leucine, lysine, glutamine, glycine, alanine, methionine and glutamine as well as the nucleobase uracil and osmolyte glycerophosphocholine. The similarities in metabolome changes suggest that lithium has an analogous mode of toxicity to that of copper, and may be impairing energy production and ionoregulation. The PCA also showed that arsenic exposure resulted in a metabolic shift in comparison to the control population but this change was not statistically significant. However, significant changes in specific metabolites such as alanine and lysine were observed, suggesting that energy metabolism is indeed disrupted. This research demonstrates that 1H NMR-based metabolomics is a viable platform for discerning metabolomic changes and mode of toxicity of D. magna in response to metal stressors in the environment. 相似文献