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191.
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
192.
193.
通过铂颗粒吸附法制备得到Pt/CeO2催化剂应用于臭氧催化氧化甲苯反应,研究了Pt颗粒负载对CeO2臭氧催化氧化甲苯的增强作用.采用氢气程序升温还原(H2-TPR)、氧气程序升温脱附(O2-TPD)、X射线光电子能谱(XPS)和拉曼光谱(Raman)等手段对催化剂进行表征,结果显示,CeO2负载Pt颗粒后,Pt与CeO2存在相互作用,提高了CeO2上氧空位的含量.臭氧分解实验证实了Pt/CeO2催化剂具有更好的臭氧分解性能.臭氧催化氧化甲苯评价结果表明,Pt/CeO2具有比CeO2更优异的催化性能,在80℃时甲苯降解率、CO2产率和臭氧分解率分别达到92.3%、92.1%和99.9%.原位拉曼进一步研究了臭氧分解生成的氧物种种类及含量,以及甲苯存在时氧物种的变化,结果表明,臭氧在氧空位上分解产生的过氧物种较为稳定,是氧化甲苯的重要活性物质.因此,P... 相似文献
194.
应用FLUENT软件中的大涡模拟模型对飞机喷漆厂房内风幕的有效性进行了研究。以某一飞机喷漆厂房内的局部为原型构建网格模型,针对若干种工况,对甲苯蒸气的扩散过程进行了数值模拟,主要研究了甲苯量和风幕速度对甲苯扩散的影响规律。对计算结果进行分析,得到了不同工况下能有效阻止甲苯扩散的临界风幕速度,研究表明在飞机喷漆厂房内设置风幕,只要风幕速度不低于该种工况下的临界风幕速度,就可有效阻止甲苯扩散,降低厂房内可燃气体的爆炸危险性。 相似文献
195.
196.
不同孔径HZSM-5协同低温等离子体催化降解甲苯性能研究 总被引:1,自引:1,他引:0
研究了HZSM-5分子筛孔径对其在等离子体场内催化降解甲苯的影响.采用化学液相沉积法对HZSM-5分子筛进行改性,利用XRD、氮气吸附脱附等方法表征样品的骨架结构和表面性质,并用择形吸附实验对样品孔径进行表征.同时,评价了HZSM-5分子筛体系中降解甲苯的性能,研究了分子筛吸附甲苯性能及臭氧的产量,并采用飞行时间质谱(TOF-MS)和气相色谱-质谱联用仪(GC-MS)分析了反应产生的有机副产物.结果表明:液相沉积法成功调控了HZSM-5孔径,样品孔径随沉积剂用量增加而减小;同时,样品均具有相同的MFI骨架结构,比表面积和孔容相差不大.HZSM-5的孔径尺寸对甲苯去除率影响不大,但对碳平衡有影响,孔径越大,碳平衡越好.孔径较大的HZSM-5分子筛对甲苯具有更大的吸附速率和吸附容量,同时更多臭氧参与反应,生成·OH和O·,促进甲苯深度氧化,减少副产物,提高碳平衡. 相似文献
197.
酸碱改性活性炭及其对甲苯吸附的影响 总被引:6,自引:1,他引:5
分别用酸溶液(H_2SO_4、HNO_3、H_3PO_4)和碱溶液(NaOH或NH_3·H_2O)浸渍方法对活性炭进行改性,并对酸改性活性炭进行碱溶液二次改性处理,通过表征改性前后活性炭BET比表面积、孔结构、表面官能团等理化特征和测定其对甲苯蒸气的饱和吸附量,研究了影响活性炭吸附甲苯蒸气的关键因素.结果表明,酸改性使BET比表面积、微孔面积、微孔容积减少、表面酸性官能团增加,而碱改性呈现相反的理化特征变化.活性炭理化特征的变化可能与改性溶液的酸碱性、氧化还原性有关,并且这种相反的变化直接关系到活性炭对甲苯蒸气的吸附.3种酸改性的活性炭对甲苯蒸气饱和吸附量相对于原活性炭减少9.6%~20.0%,而两种碱改性的活性炭则增加29.2%~39.2%.相关性分析显示甲苯吸附量与BET比表面积、微孔面积、微孔容积正相关,而与表面酸性官能团负相关;多元回归分析进一步表明微孔容积和酸性官能团数量是影响活性炭甲苯吸附的关键因素.二次改性活性炭甲苯吸附量与表面含氧酸性官能团拟合结果则表明,—COOH、C=O和—OH都对活性炭甲苯吸附能力有影响,其中—COOH影响较大.研究结果表明有效提高活性炭对甲苯吸附能力,改性宜以提高活性炭微孔容积和减小活性炭表面酸性官能团数量,特别是—COOH数量为目标导向. 相似文献
198.
通过等体积浸渍法制备了单金属Pd/γ-Al2O3催化剂和双金属Pd-Ce/γ-Al2O3催化剂,考察掺杂CeO2对Pd/γ-Al2O3催化剂催化氧化甲苯性能的影响.并通过N2吸脱附、SEM、H2-TPR表征催化剂比表面积、表面形貌及氧化还原性能.结果发现,CeO2的掺杂一定程度上降低了Pd/γ-Al2O3催化剂的比表面积,但增加了10nm孔径的孔密度,且催化剂仍保持介孔结构,当添加4% CeO2时(质量分数,下同),催化剂比表面积降至165m2/g,孔道存在一定程度的堵塞,阻碍污染物和反应产物的扩散,降低催化剂催化性能.H2-TPR结果表明,Pd和Ce之间存在较强的协同作用,与PdO相邻的CeO2更容易打开Ce-O键,相较于单金属0.2% Pd/γ-Al2O3,掺杂了0.3% CeO2的催化剂具有更强的还原峰,表明CeO2的引入为催化剂提供了更多的表面氧空位,增强了催化剂的催化氧化能力,其T10和T90与单贵金属催化剂相比分别降低10和40℃. 相似文献
199.
将低温等离子体、催化和流向变换技术相结合,以反应系统参数(接地极方式、反应管壁厚)和电源参数(电压、频率)为影响因素,探究了上述因素对系统温度升高(△T)、放电能量密度(SED)和能量效率(EE)的影响,考察了不同条件对甲苯的去除效果(η)和反应产物的影响.结果表明:流向变换低温等离子体协同催化系统中,甲苯去除效果最好,能量利用率最高,为3.76g/(kW·h).连续升压时,3种接地条件下的温度升高△T差距不明显;铝箔接地时,O3浓度最高、甲苯去除率η、SED和EE最高;增加反应管壁厚,系统△T、η、SED和EE减小.3种技术结合时,NO2生成浓度低、有机副产物生成种类较少,CO2选择性高,甲苯矿化率最高.固定频率,改变电压时,△T、η、SED与电压值呈正比,EE则相反,铝箔接地时,17kV时△T达到110.7℃,η达到74.05%;副产物O3浓度先上升后下降,最终趋于0mg/m3;固定电压,改变频率时,变化规律一致. 相似文献
200.
IntroductionTrichloroethyleneisaveryeffectivesolventtoremoveoilfromsiliconandothermaterialsusedinsemiconductorindustry.TheC2HC... 相似文献