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131.
Parizad Sheikhi Seyed Rahman Djafari Petroudy 《Journal of Polymers and the Environment》2018,26(9):3710-3717
Xylan is the second most abundant polysaccharide and the predominant hemicellulose component of soda bagasse pulp. The present endeavor focuses on increasing the value addition to underutilized agro-industrial residue such as bagasse. For this purpose, xylan was isolated by two conventional alkali extraction methods i.e. NaOH and KOH. The recovery rate and sugar composition of different reaction times and alkali consumptions were monitored with advanced method such as High Performance Liquid Chromatography (HPLC). The Fourier Transform Infrared Spectroscopy (FTIR) and Wide Angle X-ray spectroscopy (WAXS) were respectively employed to characterize the functional groups and Crystallinity Index (CrI) changes during the extraction process. It was explored that highest xylan recovery rates were obtained with 6% of NaOH at 120 min and 6% KOH at 45 min. The xylan morphology via WAXS was found that its structure to be amorphous. HPLC results also showed KOH had higher effectiveness than NaOH in terms of extracted xylan purity. Highest XGRs (Xylose to Glucose Ratios) were also achieved by KOH processes. Hence, this study contributes to the adequate utilization of agricultural residues, with promising potential for applications in the production of certain novel materials and chemical conversion industries. 相似文献
132.
Mohammad-Reza Zare Mohammad Mehdi Amin Saeedeh Hemmati-Borji Mahnaz Nikaeen Seyed Hamed Mirhosseini 《毒物与环境化学》2015,97(5):552-562
In this study, a traditional assay was modified to evaluate the effect of Hg, Cd, and Zn on the bacterial community of a sequencing batch reactor and activated sludge plants and heavy metal-resistant bacterial species were determined. After the isolation of metal-resistant bacteria, their 16S rRNA gene fragments were sequenced. The BLAST program was used to compare the resulting 16S rRNA sequences with those in GenBank database to identify the isolated bacterial species. Hg was found to be the most toxic metal for both bacterial communities investigated. Sequence batch reactor bacteria were comparatively more resistant to Hg, Cd, and Zn than those from activated sludge. The resistant strains were close to the members of genus Pseudomonas, Kocuria, Stenotrophomonas, Enterococcus, and Staphylococcus. The modified dehydrogenase enzyme assay seems to be simple, robust, and competent for evaluation of the impact of metals on bacterial activity. Sequencing batch reactor systems should be preferred over activated sludge when wastewaters containing hazardous metals are to be treated. 相似文献
133.
Behrooz RD Esmaili-Sari A Ghasempouri SM Bahramifar N Covaci A 《Environment international》2009,35(2):285-290
Persistent organochlorine pesticides (OCPs), such as dichlorodiphenyltrichloroethane (DDT) and its metabolites, hexachlorobenzene (HCB), alpha, beta and gamma-hexachlorocyclohexane (HCH) isomers, together with polychlorinated biphenyl (PCB) congeners (IUPAC Nos. 28, 52, 101, 138, 153 and 180), were determined in tail feathers from 37 birds belonging to 18 species, all originating from the South-West of Iran (Khuzestan, coast of the Persian Gulf). This is the first report on organochlorine contaminants in feathers from museum collections and it is an indication of the concentrations of OCPs and PCBs in the past (1991-1996). Median concentrations of HCHs, DDTs, PCBs and HCB were 22, 14, 11 and 10 ng/g feather, respectively. Significant correlations (p<0.05) were calculated between OCPs (except HCB) and PCBs in the bird feathers. p,p'-DDE and gamma-HCH were the most abundant OCPs, while CB 180, CB 138 and CB 101 were the predominant PCB congeners in almost all species. Significant differences (p<0.05) in the mean concentrations of DDTs and PCBs were detected among species grouped according to their feeding habits. Levels of DDTs and PCBs were highest in the carnivorous species and lowest in the herbivorous species. Levels of OCPs and PCBs in feathers of bids in the 1990s were generally below the thresholds reported to affect reproduction. 相似文献
134.
A Monte Carlo simulation technique was applied to assess the effect of stormwater quality volume captured by best management practices (BMPs) on the frequency of discharging concentrations of constituents above certain designated threshold limits. The method used an assumption of a power law relationship between the cumulative load and flow to incorporate the first flush effect. The exponent of this relationship was considered a random variable and its frequency distribution was obtained from 78 measured pollutographs from three urban highway sites in West Los Angeles, California. Although the effect of rain depth captured by BMPs is site-specific, the method offered here provides a systematic approach to evaluate the effect of selecting various regulatory guidelines for controlling urban stormwater pollution on the overall discharge of pollutants into waterways. This allows selecting the requirements for capturing runoff volume by BMPs based on the tradeoff between the probability of concentration criteria violation and economic factors. 相似文献
135.
Groundwater and water resources management plays a key role in conserving the sustainable conditions in arid and semi-arid
regions. Applying management tools which can reveal the critical and hot conditions seems necessary due to some limitations
such as labor and funding. In this study, spatial and temporal analysis of monthly groundwater level fluctuations of 39 piezometric
wells monitored during 12 years was carried out. Geostatistics which has been introduced as a management and decision tool
by many researchers has been applied to reveal the spatial and temporal structure of groundwater level fluctuation. Results
showed that a strong spatial and temporal structure existed for groundwater level fluctuations due to very low nugget effects.
Spatial analysis showed a strong structure of groundwater level drop across the study area and temporal analysis showed that
groundwater level fluctuations have temporal structure. On average, the range of variograms for spatial and temporal analysis
was about 9.7 km and 7.2 months, respectively. Ordinary and universal kriging methods with cross-validation were applied to
assess the accuracy of the chosen variograms in estimation of the groundwater level drop and groundwater level fluctuations
for spatial and temporal scales, respectively. Results of ordinary and universal krigings revealed that groundwater level
drop and groundwater level fluctuations were underestimated by 3% and 6% for spatial and temporal analysis, respectively,
which are very low and acceptable errors and support the unbiasedness hypothesis of kriging. Although, our results demonstrated
that spatial structure was a little bit stronger than temporal structure, however, estimation of groundwater level drop and
groundwater level fluctuations could be performed with low uncertainty in both space and time scales. Moreover, the results
showed that kriging is a beneficial and capable tool for detecting those critical regions where need more attentions for sustainable
use of groundwater. Regions in which were detected as critical areas need to be much more managed for using the current water
resources efficiently. Conducting water harvesting systems especially in critical and hot areas in order to recharge the groundwater,
and altering the current cropping pattern to another one that need less water requirement and applying modern irrigation techniques
are highly recommended; otherwise, it is most likely that in a few years no more crop would be cultivated. 相似文献
136.
Smith LA Stock TH Chung KC Mukerjee S Liao XL Stallings C Afshar M 《Environmental monitoring and assessment》2007,128(1-3):369-379
In the summer of 2003, ambient air concentrations of volatile organic compounds (VOCs) were measured at 12 sites within a
3-km radius in Deer Park, Texas near Houston. The purpose of the study was to assess local spatial influence of traffic and
other urban sources and was part of a larger investigation of VOC spatial and temporal heterogeneity influences in selected
areas of Houston. Seventy 2-h samples were collected using passive organic vapor monitors. Most measurements of 13 VOC species
were greater than the method detection limits. Samplers were located at 10 residential sites, a regulatory air monitoring
station, and a site located at the centroid of the census tract in which the regulatory station was located. For residential
sites, sampler placement locations (e. g., covered porch vs. house eaves) had no effect on concentration with the exception
of methyl tertiary-butyl ether (MTBE). Relatively high correlations (Pearson r > 0.8) were found between toluene, ethylbenzene, and o,m,p-xylenes suggesting petroleum-related influence. Chloroform was not correlated with these species or benzene (Pearson r < 0.35) suggesting a different source influence, possibly from process-related activities. As shown in other spatial studies,
wind direction relative to source location had an effect on VOC concentrations. 相似文献
137.
Effect of fertilizer application on soil heavy metal concentration 总被引:22,自引:0,他引:22
Zahra Atafar Alireza Mesdaghinia Jafar Nouri Mehdi Homaee Masoud Yunesian Mehdi Ahmadimoghaddam Amir Hossein Mahvi 《Environmental monitoring and assessment》2010,160(1-4):83-89
A large amount of chemicals is annually applied at the agricultural soils as fertilizers and pesticides. Such applications may result in the increase of heavy metals particularly Cd, Pb, and As. The objective of this study was to investigate the variability of chemical applications on Cd, Pb, and As concentrations of wheat-cultivated soils. Consequently, a study area was designed and was divided into four subareas (A, B, C, and D). The soil sampling was carried out in 40 points of cultivated durum wheat during the 2006–2007 periods. The samples were taken to the laboratory to measure their heavy metal concentration, soil texture, pH, electrical conductivity, cationic exchange capacity, organic matter, and carbonate contents. The result indicated that Cd, Pb, and As concentrations were increased in the cultivated soils due to fertilizer application. Although the statistical analysis indicates that these heavy metals increased significantly (P value < 0.05), the lead and arsenic concentrations were increased dramatically compared to Cd concentration. This can be related to overapplication of fertilizers as well as the pesticides that are used to replant plant pests, herbs, and rats. 相似文献
138.
Seyed Hamidreza Sadeghi Shirko Ebrahimi Mohammadi Vijay P. Singh Kamran Chapi 《Environmental monitoring and assessment》2017,189(5):238
The temporal variability of phosphorus (P) transport and the relationships between discharge, suspended sediment concentration and particulate (PP), and soluble (SP) phosphorus were examined. The study was conducted at the event scale in seven tributaries of the Zarivar Lake watershed in Kurdistan Province (Iran) from March 2011 to April 2012. Based on eight runoff events, 82% of the total P was the PP carried out by suspended sediment. Results showed a high variability of P transport during different runoff events. It was found that soil erosion was the source of the high P load. For all tributaries, PP was linearly related to both discharge and suspended sediment concentration. However, the relationships of SP and PP with discharge and suspended sediment concentration showed different hysteresis patterns. The relationship between PP and discharge was generally characterized by a clockwise pattern (i.e., lower part contribution of the sub-watersheds) but the patterns between SP and discharge were mainly anticlockwise (i.e., upper part contribution of the sub-watersheds or perhaps due to a subsurface flow contribution). 相似文献
139.
Trend and concentrations of legacy lead (Pb) in highway runoff 总被引:2,自引:0,他引:2
Kayhanian M 《Environmental pollution (Barking, Essex : 1987)》2012,160(1):169-177
This study presents the results of lead (Pb) concentrations from both highway runoff and contaminated soil along 32 and 23 highway sites, respectively. In general, the Pb concentration on topsoil (0-15 cm) along highways was much higher than the Pb concentration in subsurface soil (15-60 cm). The Pb deposited on soil appears to be anthropogenic and a strong correlation was found between the Pb concentration in surface soil and highway runoff in urban areas. The concentration of Pb measured during 1980s from highways runoff throughout the world was up to 11 times higher than the measured values in mid 1990 s and 2000s. The current Pb deposited on soil near highways appears to be a mixture of paint, tire weight balance and old leaded gasoline combustion. Overall, the Pb phase-out regulation reduced the Pb deposits in the environment and consequently lowered Pb loading into receiving waters. 相似文献
140.
Characterization of ionic composition of TSP and PM10 during the Middle Eastern Dust (MED) storms in Ahvaz, Iran 总被引:1,自引:0,他引:1
Shahsavani A Naddafi K Jaafarzadeh Haghighifard N Mesdaghinia A Yunesian M Nabizadeh R Arhami M Yarahmadi M Sowlat MH Ghani M Jonidi Jafari A Alimohamadi M Motevalian SA Soleimani Z 《Environmental monitoring and assessment》2012,184(11):6683-6692
Because of the recent frequent observations of major dust storms in southwestern cities in Iran such as Ahvaz, and the importance of the ionic composition of particulate matters regarding their health effects, source apportionment, etc., the present work was conducted aiming at characterizing the ionic composition of total suspended particles (TSP) and particles on the order of ~10?μm or less (PM(10)) during dust storms in Ahvaz in April-September 2010. TSP and PM(10) samples were collected and their ionic compositions were determined using an ion chromatography. Mean concentrations of TSP and PM(10) were 1,481.5 and 1,072.9?μg/m(3), respectively. Particle concentrations during the Middle Eastern Dust (MED) days were up to four times higher than those in normal days. Ionic components contributed to only 9.5% and 11.3% of the total mass of TSP and PM(10), respectively. Crustal ions were most abundant during dust days, while secondary ions were dominant during non-dust days. Ca(2+)/Na(+) and Cl(-)/Na(+) ratios can be considered as the indicators for identification of the MED occurrence. It was found that possible chemical forms of NaCl, (NH(4))(2)SO(4), KCl, K(2)SO(4), CaCl(2), Ca(NO(3))(2), and CaSO(4) may exist in TSP. Correlation between the anionic and cationic components suggests slight anion and cation deficiencies in TSP and PM(10) samples, though the deficiencies were negligible. 相似文献