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981.
Spiteri C Slomp CP Regnier P Meile C Van Cappellen P 《Journal of contaminant hydrology》2007,92(1-2):87-108
A 1D reactive transport model (RTM) is used to obtain a mechanistic understanding of the fate of phosphorus (P) in the saturated zone of two contrasting aquifer systems. We use the field data from two oxic, electron donor-poor, wastewater-impacted, sandy Canadian aquifers, (Cambridge and Muskoka sites) as an example of a calcareous and non-calcareous groundwater system, respectively, to validate our reaction network. After approximately 10 years of wastewater infiltration, P is effectively attenuated within the first 10 m down-gradient of the source mainly through fast sorption onto calcite and Fe oxides. Slow, kinetic sorption contributes further to P removal, while precipitation of phosphate minerals (strengite, hydroxyapatite) is quantitatively unimportant in the saturated zone. Nitrogen (N) dynamics are also considered, but nitrate behaves essentially as a conservative tracer in both systems. The model-predicted advancement of the P plume upon continued wastewater discharge at the calcareous site is in line with field observations. Model results suggest that, upon removal of the wastewater source, the P plume at both sites will persist for at least 20 years, owing to desorption of P from aquifer solids and the slow rate of P mineral precipitation. Sensitivity analyses for the non-calcareous scenario (Muskoka) illustrate the importance of the sorption capacity of the aquifer solids for P in modulating groundwater N:P ratios in oxic groundwater. The model simulations predict the breakthrough of groundwater with high P concentrations and low N:P ratios after 17 years at 20 m from the source for an aquifer with low sorption capacity (<0.02% w/w Fe(OH)(3)). In this type of system, denitrification plays a minor role in lowering the N:P ratios because it is limited by the availability of labile dissolved organic matter. 相似文献
982.
Vandenhove H Van Hees M Wannijn J Wouters K Wang L 《Environmental pollution (Barking, Essex : 1987)》2007,145(2):577-586
The present study aimed to quantify the influence of soil parameters on uranium uptake by ryegrass. Ryegrass was established on eighteen distinct soils, spiked with (238)U. Uranium soil-to-plant transfer factors (TF) ranged from 0.0003 to 0.0340kgkg(-1). There was no significant relation between the U soil-to-plant transfer (or total U uptake or flux) and the uranium concentration in the soil solution or any other soil factor measured, nor with the U recovered following selective soil extractions. Multiple linear regression analysis resulted in a significant though complex model explaining up to 99% of variation in TF. The influence of uranium speciation on uranium uptake observed was featured: UO(2)(+2), uranyl carbonate complexes and UO(2)PO(4)(-) seem the U species being preferentially taken up by the roots and transferred to the shoots. Improved correlations were obtained when relating the uranium TF with the summed soil solution concentrations of mentioned uranium species. 相似文献
983.
Tree species effect on the redistribution of soil metals 总被引:1,自引:0,他引:1
Mertens J Van Nevel L De Schrijver A Piesschaert F Oosterbaan A Tack FM Verheyen K 《Environmental pollution (Barking, Essex : 1987)》2007,149(2):173-181
Phytostabilization of metals using trees is often promoted although the influence of different tree species on the mobilization of metals is not yet clear. Soil and biomass were sampled 33 years after planting four tree species (Quercus robur, Fraxinus excelsior, Acer pseudoplatanus, Populus 'Robusta') in a plot experiment on dredged sediment. Poplar took up high amounts of Cd and Zn and this was associated with increased Cd and Zn concentrations in the upper soil layer. The other species contained normal concentrations of Cd, Cu, Cr, Pb and Zn in their tissues. Oak acidified the soil more than the other species and caused a decrease in the concentration of metals in the upper soil layer. The pH under poplar was lower than expected and associated with high carbon concentrations in the top soil. This might be assigned to retardation of the litter decomposition due to elevated Cd and Zn concentrations in the litter. 相似文献
984.
Phytoextraction of metals from soils: how far from practice? 总被引:2,自引:0,他引:2
Van Nevel L Mertens J Oorts K Verheyen K 《Environmental pollution (Barking, Essex : 1987)》2007,150(1):34-40
For most trace elements, the technique of phytoextraction needs significant improvements to become practically feasible. Calculations for Cd revealed that the amount of Cd taken up by Thlaspi caerulescens or Salix spp. needs at least to be the double of the present amount to slightly decrease the Cd concentration in the upper 0.5m of the soil within a period of 10 years. Additionally, metals taken up by the plants might pose an important risk. Alternatives as bioavailable contaminant stripping and phytostabilization might be more appropriate. 相似文献
985.
Shi L Bayless DJ Kremer G Stuart B 《Journal of the Air & Waste Management Association (1995)》2007,57(4):489-496
A numerical model for simulation of the electrohydrodynamic flow in an electrically enhanced cyclone is presented. A finite element approach was applied to solve the coupled equations for the positive corona-induced electric field. Three-dimensional simulations of gas flow were carried using Reynolds-Averaged Navier-Stokes equations including the Reynolds stress model and the electrohydrodynamic effect. Numerical results show that the change in the flow profile because of the influence of the corona-induced electric field is apparent when the inlet flow rate is low but is negligible at higher flow rates. 相似文献
986.
Wind erosion selectively winnows the fine, most chemically concentrated portions of surface soils and results in the inter-regional
transport of fugitive dust containing plant nutrients, trace elements and other soil-borne contaminants. We sampled and analyzed
surface soils, sediments in transport over eroding fields, and attic dust from a small area of the Southern High Plains of
Texas to characterize the physical nature and chemical constituents of these materials and to investigate techniques that
would allow relatively rapid, low cost techniques for estimating the chemical constituents of fugitive dust from an eroding
field. From chemical analyses of actively eroding sediments, it would appear that Ca is the only chemical species that is
enriched more than others during the process of fugitive dust production. We found surface soil sieved to produce a sub-sample
with particle diameters in the range of 53–74 μm to be a reasonably good surrogate for fugitive dust very near the source
field, that sieved sub-samples with particle diameters <10 μm have a crustal enrichment factor of approximately 6, and that
this factor, multiplied by the chemical contents of source soils, may be a reasonable estimator of fugitive PM10 chemistry from the soils of interest. We also found that dust from tractor air cleaners provided a good surrogate for dust
entrained by tillage and harvesting operations if the chemical species resulting from engine wear and exhaust were removed
from the data set or scaled back to the average of enrichment factors noted for chemical species with no known anthropogenic
sources. Chemical analyses of dust samples collected from attics approximately 4 km from the nearest source fields indicated
that anthropogenic sources of several environmentally important nutrient and trace element species are much larger contributors,
by up to nearly two orders of magnitude, to atmospheric loading and subsequent deposition than fugitive dust from eroding
soils. 相似文献
987.
Menchai P Van Zwieten L Kimber S Ahmad N Rao PS Hose G 《Environmental pollution (Barking, Essex : 1987)》2008,153(1):110-118
We describe the reduction in bioavailability of DDT in contaminated soil after it was incubated as sediment for 365 d. Bioavailability was assessed using semi-permeable membranes. Contaminated soils from three cattle dip sites, one spiked paired uncontaminated site, and one spiked OECD standard soil were studied. Sandy soil with residues of 1880 mg/kg summation operator DDT incurred since 1962, initially had 4.6% of summation operator DDT available, reducing to 0.6% following 365 d. Clay soil (1108 mg summation operator DDT/kg) had 4.1% initially available, reducing to 0.3% after 365 d. Freshly spiked soils had a greater amount of DDT initially available (10.9%), but this reduced to 1.5% by the end of the incubation. Of the DDT congeners, both o,p'-DDD and p,p'-DDD were most bioavailable in the soils, but also had the most significant decrease following incubation. 相似文献
988.
989.
A multi-stage sampling strategy for the delineation of soil pollution in a contaminated brownfield 总被引:4,自引:0,他引:4
A multi-stage sampling strategy, based on sequential Gaussian simulation, was presented to optimize the step-wise selection of a small numbers of additional samples to delineate soil pollution. This strategy was applied to a Belgian brownfield of 5.2 ha polluted with lead (Pb). Starting from an initial number of 240 samples in stage 1, additional samples were added, 25 per stage, and the reduction of the uncertainty in the Pb delineation was monitored. Twenty stages were used. Already in stage 6 a local optimum was found based on the median conditional coefficient of variation. An independent validation confirmed that this index was to be preferred over the median conditional variance. So for the brownfield considered our procedure indicated that 365 selected samples would have been sufficient, representing a gain of 70.7% in sampling effort compared to current practice which resulted in a sampling effort of 1245 samples. 相似文献
990.
Stress responses of Calluna vulgaris to reduced and oxidised N applied under 'real world conditions'
Sheppard LJ Leith ID Crossley A Van Dijk N Fowler D Sutton MA Woods C 《Environmental pollution (Barking, Essex : 1987)》2008,154(3):404-413
Effects and implications of reduced and oxidised N, applied under 'real world' conditions, since May 2002, are reported for Calluna growing on an ombrotrophic bog. Ammonia has been released from a 10 m line source generating monthly concentrations of 180-6 microg m(-3), while ammonium chloride and sodium nitrate are applied in rainwater at nitrate and ammonium concentrations below 4mM and providing up to 56 kg N ha(-1) year(-1) above a background deposition of 10 kg N ha(-1) year(-1). Ammonia concentrations, >8 microg m(-3) have significantly enhanced foliar N concentrations, increased sensitivity to drought, frost and winter desiccation, spring frost damage and increased the incidence of pathogen outbreaks. The mature Calluna bushes nearest the NH3 source have turned bleached and moribund. By comparison the Calluna receiving reduced and oxidised N in rain has shown no significant visible or stress related effects with no significant increase in N status. 相似文献