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81.
M. A. Castillo-Santiago A. Hellier R. Tipper B. H. J. de Jong 《Mitigation and Adaptation Strategies for Global Change》2007,12(6):1213-1235
This study examines the correlation between deforestation, carbon dioxide emissions and potential causal factors of land-use
change within an area of 2.7 million ha in Chiapas, southern Mexico between 1975 and 1996. Digitized land-use maps and interpreted
satellite images were used to quantify land-use changes. Geo-referenced databases of population and digitized maps of roads
and topography were used to determine which factors could be used to explain observed changes in land-use. The study analyzed
the relationship between carbon emissions during this period and two types of possible causal factors: “predisposing” factors
that determine the susceptibility of a particular area of forest to change (slope, distance to agriculture and roads, land
tenure) and “driving” factors representing the pressures for change (population density, poverty). The correlated factors
were combined in risk matrices, which show the proportion of vulnerable carbon stocks lost in areas with defined social, economic
and environmental characteristics. Such matrices could be used to predict future deforestation rates and provide a verifiable
evidence-base for defining baseline carbon emissions for forest conservation projects. Based on the results of the analysis,
two matrices were constructed, using population density as the single most important driving factor and distance from roads
and distance from agriculture as the two alternatives for the predisposing factors of deforestation. 相似文献
82.
Koh CH Khim JS Kannan K Villeneuve DL Senthilkumar K Giesy JP 《Environmental pollution (Barking, Essex : 1987)》2004,132(3):489-501
Sediment, pore water and water samples from the Hyeongsan River, Korea were analyzed for several classes of halogenated aromatic hydrocarbons (HAHs) and their dioxin-like activities were evaluated using the in vitro H4IIE-luc bioassay. Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) were detected in sediments from all six sampling locations with mean concentrations of 2.8 x 10(2) pg/g, 190 pg/g, and 61.4 ng/g, dw, respectively. Polycyclic aromatic hydrocarbons (PAHs) were predominated by 4-6 ring compounds with concentrations in the range of 5.30-7680 ng/g, dw. Chemical profiles of target analytes in sediment and water samples revealed that there was a gradient of concentrations along the river from upstream to downstream, which suggested that the primary source was a wastewater reservoir adjacent to a sewage treatment plant (STP). TEQs derived by summing the product of concentrations of individual congeners by their respective relative potencies (REPs or TEFs) ranged from 4.3 x 10(-1) to 1.1 x 10(3) pg/g, dw. Raw Soxhlet extracts from all six sampling locations induced significant dioxin-like responses in the H4IIE-luc bioassay. TCDD-EQs derived from H4IIE bioassay ranged from 7 x 10(-3) to 1.5 x 10(3) pg/g, dw, which were significantly correlated with TEQs (r2 = 0.994, p < 0.05). Among the three Florisil fractions tested, PCDD/Fs in fraction (F2) induced the greatest magnitude of response (range: 24-83%-TCDD-max.) in the H4IIE-luc assay. Comparison of the TEQ and TCDD-EQ suggested little non-additive interaction between fractions and AhR-active and inactive compounds. Concentrations of individual congeners as well as TEQs and TCDD-EQs suggest inputs from the industrial center waste stream in the Hyeongsan River. 相似文献
83.
Samples from two Dutch raw water sources were chlorinated in the laboratory at different pH:s and chlorine doses, and were analysed for mutagenic activity and the mutagenic compound 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX). Chlorination produced mutagenic activity as well as MX in both waters. The formation of MX was favoured by acidic reaction conditions and high chlorine doses, but in waters treated with excess chlorine at pH 9, no MX was detected. The mutagenicity was approximately on the same level after chlorination of both water types but the MX concentration was significantly higher in the water containing mainly humic material.
MX was found to be quantitatively extracted from acidified waters by the XAD resin adsorption technique. 相似文献
84.
(137)Cs is one of the major artificial radionuclides found in environments; but the mechanisms behind fertilizer-induced (137)Cs desorption from soil remain unknown. This study aimed to investigate the kinetics and mechanisms underlying the various cations and anions that cause Cs release from soil under acidic conditions. NH(4)H(2)PO(4) (1M), 0.5M (NH(4))(2)SO(4), 1M NH(4)Cl, 1M KCl or 1M NaCl solutions were added to (137)Cs-contaminated soil. The power function model well described the short term (137)Cs desorption with the solutions. The rate coefficients for (137)Cs release from soil in NH(4)H(2)PO(4), (NH(4))(2)SO(4), NH(4)Cl, and KCl solutions were 7.7, 7.3, 6.8, and 6.1 times higher than the rate observed in a NaCl solution, respectively. The NH(4)H(2)PO(4) and (NH(4))(2)SO(4) solutions induced significantly greater (137)Cs release from the contaminated soil than the NH(4)Cl, KCl and NaCl solutions. After four times repeated extractions with the fertilizer solutions, the total amount of (137)Cs extracted by (NH(4))(2)SO(4) and NH(4)Cl solutions reached equilibrium, while that extracted using an NH(4)H(2)PO(4) solution continued to increase. The combined effect of phosphate and protons was the major mechanism behind (137)Cs release from contaminated soils, when an NH(4)H(2)PO(4) solution was used. 相似文献
85.
Studies on hexavalent chromium biosorption by chemically-treated biomass of Ecklonia sp 总被引:10,自引:0,他引:10
The biomass of the brown seaweed, Ecklonia sp., is capable of reducing Cr(VI) to Cr(III). However, very little is known about the mechanism of Cr(VI) reduction by the biomass. The aims of the present investigation were to enhance the Cr(VI)-reducing capacity of the biomass using various chemical treatments and to elucidate the mechanisms governing Cr(VI) reduction. Among the various chemical treatments, acid-treatment showed the best performance with regards the improvement of Cr(VI) removal from the aqueous phase, while organic solvent-treatment significantly improved the removal efficiency of total Cr in the equilibrium state. Based on FTIR study, the biomass was subjected to chemical modification of its amino and carboxyl groups, to examine their roles in the Cr(VI) removal from the aqueous phase. Methylation of the amino group significantly decreased the Cr(VI) removal rate, but amination of the carboxyl group significantly increased the Cr(VI) removal rate. Meanwhile, esterification of the carboxyl group and carboxylation of the amino group decreased the Cr(VI) removal rate, but the former showed a more negative effect than the latter. These findings indicated that the amino and carboxyl groups take part in the Cr(VI) removal from the aqueous phase. In conclusion, mechanisms for direct and indirect Cr(VI) removal are proposed, and some aspects for the application of this biomass to Cr(VI) detoxification are discussed. 相似文献
86.
Eelgrass (Zostera marina L.) in the Dutch Wadden Sea historically covered an area varying from 65–150 km2 in the eulittoral as well as the sublittoral zones. At present, this area comprises less than 1 km2 eulittoral eelgrass stands, with an associated decrease in habitat diversity. The causes for this decline are presumably
connected with the ‘wasting disease’ and the closure of the former Zuiderzee in the early 1930s resulting in increased tidal
range and increased currents. After a slight recovery of the eelgrass populations on the intertidal flats a definite decline
started in the early 1970s, possibly connected to increased turbidity. The present water quality and turbidity do not negatively
influence eelgrass growth up to a depth of at least 0.6m below Mean Sea Level. Based on mesocosm experiments and field experiments
it is concluded that re-establishment of eelgrass should be possible in sheltered bays and on unexposed tidal flats. The most
suitable depths for a reintroduction are those between 0 and 20–40 cm below mean sea level. 相似文献
87.
Summary 2-spot ladybirds secrete alkaloid (adaline)-rich defence fluid (reflex blood) in response to predator attack. Reflex fluid was collected from individual ladybirds and weighed and the alkaloid content measured by GC. The amount of fluid produced built up rapidly following winter hibernation in animals feeding on aphids. The concentration of adaline in the fluid was highest in the first bleeding after winter hibernation. A large sample of beetles was reflex bled several times. Significant among beetle variation was found in the amount of fluid produced and the concentration of the reflex blood. The results are discussed in relation to the possibility that 2-spot ladybirds are Batesian mimics of 7-spot ladybirds and to the possible functions of adaline. 相似文献
88.
Eelgras (Zostera marina L.) in the Dutch Wadden Sea historically covered an area varying from 65–150 km2 in the eulittoral as well as the sublittoral zones. At present, this area comprises less than 1 km2 eulittoral eelgrass stands, with an associated decrease in habitat diversity. The causes for this decline are presumably
connected with the ‘wasting disease’ and the closure of the former Zuiderzee in the early 1930s resulting in increased tidal
range and increased currents. After a slight recovery of the eelgrass populations on the intertidal flats a definite decline
started in the early 1970s, possibly connected to increased turbidity. The present water quality and turbidity do not negatively
influence eelgrass growth up to a depth of at least 0.6m below Mean Sea Level. Based on mesocosm experiments and field experiments
it is concluded that re-establishment of eelgrass should be possible in sheltered bays and on unexposed tidal falts. The most
suitable depths for a reintroduction are those between 0 and 20–40 cm below mean sea level. 相似文献
89.
The Keelung port, which is located on the northern tip of Taiwan, right next to the Taipei metropolitan area, is an important
international harbor. However, any air pollutants generated from the Keelung port region, immediately travel to the neighboring
Keelung city, and greatly impact the residents' daily life and the quality of their environment. This study has investigated
and quantified pollution emissions, from the Keelung port region, between 1997 and 2002. Emissions from major air pollution
sources were estimated. The estimated results indicated that total TSP (total suspended particles) emissions had significantly
increased, from 5221 ton/yr in 1997 to 262 687 ton/yr in 2002, due to the greatly increased volume of sand imported into Keelung
Harbor. Quantities of other emissions, such as SO2, NO2, CO and HC remained stable and were 440, 207, 78 and 25 ton/yr, respectively, on average, with variations within 7% over
the previous six-year period. By examining the emissions from pollution sources, it was found that TSP emissions mainly originated
from re-suspension of dust, due to both vehicle movement and the sand unloading process; this accounted for over 99% of the
total TSP emissions produced in the port region. About 80% of the total SO2 emissions originated from the main ships' engines within the Keelung port region, due to the use of fuel with a high sulfur
content. In addition, loading/unloading machines within the port region were the major sources of NO2, CO and HC pollution emissions, which comprised 54, 58 and 66% of the total emissions of these pollutants, respectively.
TSP emissions from Keelung port were much higher than from the neighboring Keelung city; hence, alleviating TSP emissions
should be the first priority for air pollution reduction within both the port of Keelung and Keelung city. 相似文献
90.