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171.
The 2,4,6-trinitrotoluene(TNT)is a potential carcinogens and TNT contaminated wastewater,which could not be effectively disposed with conventional treatments.The supercritical water oxidation(SCWO)to treat TNT contaminated wastewater was studied in this article.The TNT concentration in wastewater was measured by high-performance liquid chromatograph(HPLC)and the degraded intermediates were analyzed using GC-MS.The results showed that SCWO could degrade TNT efficiently in the presence of oxygen.The reaction temperature,pressure,residence time and oxygen excess were the main contributing factors in the process.The decomposition of TNT was accelerated as the temperature or residence time increased.At 550℃,24 MPa,120 s and oxygen excess 300%,TNT removal rate could exceed 99.9%.Partial oxidation occured in SCWO without oxygen.It was concluded that supercritical water was a good solvent and had excellent oxidation capability in the existence of oxygen.The main intermediates of TNT during SCWO included toluene,1,3,5-trinitrobenzene,nitrophenol,naphthalene,fluorenone,dibutyl phthalate,alkanes and several dimers based on the intermediate analysis.Some side reactions,such as coupled reaction,hydrolysis reaction and isomerization reaction may take place simultaneously when TNT was oxidized by SCWO. 相似文献
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HAO Li-qing WANG Zhen-y FANG Li ZHANG Wei-jun WANG Wei LI Cheng-xiang SHENG Liu-si 《环境科学学报(英文版)》2006,18(5):903-909
Photooxidation reaction of toluene in smog chamber systems was initiated by the UV radiation of tolucne/CH5ONO/NOx mixtures. The products of the photooxidation reaction of toluene and its subsequent reactions were analyzed directly utilizing Fourier transform infrared spectrometer (FTIR). Detailed assignments to FTIR spectrum of gas-phase products were given. The information of some important functional groups in the products, such as, carbonyl groups (C-O), hydroxyl groups (-OH), carboxylic acid (- COOH), C-C bonding, N O bonding and C-H bonding (C H), was got from this analysis. These results were compared to those analyzed by aerosol time of flight mass spectrometer (ATOFMS). It was found that there are some differcnccs between FTIR analysis of gas-phase products and that of particle-phase, for example, the products with carbonyl groups, which were connected to unsaturated chemical bonds, was relatively higher in the gas phase, while kctoncs, aldehydes, carboxylic acid and organonitrates were the dominant functional groups in the aerosol-phase reaction products. The possible reaction pathways of some important products in the gas phase were also discussed. 相似文献
179.
Jackson MM 《Environmental monitoring and assessment》2006,116(1-3):363-382
The emission estimation of nine volatile organic compounds (VOCs) from eight organic liquids storage tanks companies in Dar-es-Salaam
City Tanzania has been done by using US EPA standard regulatory storage tanks emission model (TANKS 4.9b). Total VOCs atmospheric
emission has been established to be 853.20 metric tones/yr. It has been established further that petrol storage tanks contribute
about 87% of total VOCs emitted, while tanks for other refined products and crude oil were emitting 10% and 3% of VOCs respectively.
Of the eight sources (companies), the highest emission value from a single source was 233,222.94 kg/yr and the lowest single
source emission value was 6881.87 kg/yr. The total VOCs emissions estimated for each of the eight sources were found to be
higher than the standard level of 40,000 kg/yr per source for minor source according to US EPA except for two sources, which
were emitting VOCs below the standard level. The annual emissions per single source for each of the VOCs were found to be
below the US EPA emissions standard which is 2,000~kg/yr in all companies except the emission of hexane from company F1 which
was slightly higher than the standard. The type of tanks used seems to significantly influence the emission rate. Vertical
fixed roof tanks (VFRT) emit a lot more than externally floating roof tanks (EFRT) and internally floating roof tanks (IFRT).
The use of IFRT and EFRT should be encouraged especially for storage of petrol which had highest atmospheric emission contribution.
Model predicted atmospheric emissions are less than annual losses measured by companies in all the eight sources. It is possible
that there are other routes for losses beside atmospheric emissions. It is therefore important that waste reduction efforts
in these companies are directed not only to reducing atmospheric emissions, but also prevention of the spillage and leakage
of stored liquid and curbing of the frequently reported illegal siphoning of stored products. Emission rates for benzene,
toluene, and xylene were used as input to CALPUFF air dispersion model for the calculation of spatial downwind concentrations
from area sources. By using global positioning system (GPS) and geographical information system (GIS) the spatial benzene
concentration contributed by organic liquid storage tanks has been mapped for Dar-es-Salaam City. Highest concentrations for
all the three toxic pollutants were observed at Kigamboni area, possibly because the area is located at the wind prevailing
direction from the locations of the storage tanks. The model predicted concentrations downwind from the sources were below
tolerable concentrations by WHO and US-OSHA. The highest 24 hrs averaging time benzene concentration was used for risk assessment
in order to determine maximum carcinogenic risk amongst the population exposed at downwind. Established risk for adult and
children at 2.9×10-3 and 1.9×10-3 respectively, are higher than the acceptable US-EPA risk of 1×10-6. It is very likely that the actual VOCs concentrations in some urban areas in Tanzania including Dar-es-Salaam City are much
higher than the levels reported in this study when other sources such as petrol stations and motor vehicles on the roads are
considered. Tanzania Government therefore need to put in place: an air quality policy and legislation, establish air quality
guidelines and acquire facilities which will enable the implementation of air quality monitoring and management programmes. 相似文献
180.
生物膜法净化甲苯二甲苯混合废气的研究 总被引:8,自引:4,他引:4
在生物滴滤器中对低质量浓度甲苯、二甲苯混合废气的净化性能进行试验研究。结果表明:甲苯、二甲苯的净化率均随入口浓度增加而降低,同样条件下二甲苯净化率明显低于甲苯;单负荷进气且气体流量为200L/h时,甲苯最大生化降解量为79.5g/(m3.h),二甲苯最大生化降解量为47.5g/(m3.h);多负荷进气由于竞争抑制作用导致两者净化程度均有所降低。维持甲苯、二甲苯质量浓度不变,两种废气的净化率η均随气量的增加而减少;在气量为260L/h时,两种化合物生化降解量均达到最大值,适宜停留时间为119s。 相似文献