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31.
Mixed halogenated dibenzo-p-dioxins and dibenzofurans (PXDD/PXDFs, X = Br, Cl) are formed through combustion processes, and may be more toxic than their corresponding chlorinated and brominated analogues. With 4600 potential congeners, limited analytical standards, and complex environmental matrices, PXDD/PXDFs present a significant analytical challenge. Gas chromatography tandem mass spectrometry (GC-MS/MS) offers both selectivity and sensitivity through multiple reaction monitoring of unique transitions in a novel approach to PXDD/PXDF congener identification. Method validation was performed through analysis of soil samples obtained from a recycling plant fire. Of the PXDD/PXDFs examined, monobromo-dichlorodibenzofuran was the most prevalent, ranging in concentration from 8.6 ng g−1 to 180 ng g−1. Dibromo-dichlorodibenzo-p-dioxin, a compound of toxicological concern, ranged from 0.41 ng g−1 to 10 ng g−1. Concentrations of PXDD/PXDFs were between 6% and 10% that of the corresponding polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDFs), with the exception of dibromo-dichlorodibenzo-p-dioxin concentrations, which were 36% that of tetrachlorodibenzo-p-dioxins. Higher levels of polybrominated PXDD/PXDFs may indicate a significant bromine source was present during combustion. 相似文献
32.
Haruhiro Ino Yoshihisa Matsumoto Ryo Takahashi Kazukiyo Takami Junya Nishino Masaaki Itoh 《Journal of Material Cycles and Waste Management》2008,10(2):129-133
H-ZSM-5 zeolite-supported gallium oxides were studied as aromatization catalysts for polyolefin pyrolysate. The catalysts
were prepared by a conventional physical mixing method with a gallium content of 1.0 and 4.5 wt% and were reduced in flowing
hydrogen at 585°C. To test their activity, a polyolefin sample was pyrolyzed and passed over a heated catalyst layer; the
product was analyzed by gas chromatography/mass spectrometry. A continuous-flow fixed-bed reactor was used for aromatization
of a model gas of polyolefin pyrolysate. For chlorine-free sources at 450°C, the catalyst with only 1.0 wt% gallium exhibited
activity comparable to a gallium silicate catalyst. For chlorine-contaminated sources, the catalyst with 4.5 wt% gallium sustained
catalytic activity for long periods. From the activity test results, it was found that zeolite-supported gallium catalysts
prepared by the physical mixing method are suitable for converting polyolefin into aromatic hydrocarbons. 相似文献
33.
Hazardous waste dechlorination reduces the potential of creating dioxins during the incineration process. To investigate the salt effect on waste dechlorination, molten hydroxides with a low melting temperature were utilized for the pre-dechlorination and decomposition of chlorine-containing organic wastes(COWs) including trichlorobenzene(TCB),perchloroethylene, hexachlorobenzene and chlordane. The results showed that a eutectic mixture of caustic sodium and potassium hydroxides(41 wt.% NaOH and 59 wt.% KOH) led to a low melting point below 300°C and a relatively high chlorine retention efficiency(CRE) with TCB as a representative COWs. The amounts of hydroxides, reaction time, and temperature all had notable influence on CRE. When the mass ratio of hydroxides to TCB reached 30:1,approximately 98.1% of the TCB was destroyed within 2.5 hr at 300°C with CRE of 71.6%.According to the residue analysis, the shapes of reaction residues were irregular with particles becoming swollen and porous. The benzene ring and C–Cl bonds disappeared, while carboxyl groups formed in the residues. The stripped chlorine was retained and condensed to form chloride salts, and the relative abundance of the chloride ions associated with the mass of TCB in residues increased from 0 to 75.0% within the 2.5 hr reaction time. The observed concentration of dioxins in residues was 5.6 ngTEQ/kg. A reaction pathway and possible additional reactions that occur in this dechlorination system were proposed. Oxidizing agents may attack TCB and facilitate hydrogenation/dechlorination reactions, making this process a promising and environmentally friendly approach for chlorine-containing organic waste treatment. 相似文献
34.
Daekyun Kim Nuray Ates Sehnaz Sule Kaplan Bekaroglu Meric Selbes Tanju Karanfil 《环境科学学报(英文版)》2017,29(8):155-162
The main objective of this study was to assess the combined use of chlorine dioxide (ClO2) and chlorine (Cl2) on the speciation and kinetics of disinfection by-product (DBP) formation in swimming pools using synthetic pool waters prepared with a body fluid analog (BFA) and/or fresh natural water. At 1:25 (mass ratio) of ClO2 to Cl2, there was no significant reduction in the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) for both BFA solution and natural water compared to the application of Cl2 alone. When the mass ratio of ClO2 to Cl2 increased to 1:1, substantial decreases in both THMs and HAAs were observed in the natural water, while there was almost no change of DBP formations in the BFA solution. Haloacetonitriles and halonitromethanes levels in both water matrices remained similar. In the presence of bromide, the overall DBP formation increased in both BFA solution and natural water. For the DBP formation kinetics, after 72 hr of contact time, very low formation of THMs and HAAs was observed for the use of ClO2 only. Compared to Cl2 control, however, applying the 1:1 mixture of ClO2/Cl2 reduced THMs by > 60% and HAAs by > 50%. Chlorite was maintained below 1.0 mg/L, while the formation of chlorate significantly increased over the reaction time. Finally, in a bench-scale indoor pool experiment, applying ClO2 and Cl2 simultaneously produced less THMs compared to Cl2 control and kept chlorite at < 0.4 mg/L, while HAAs and chlorate accumulated over 4-week operation period. 相似文献
35.
以辛醇废水为研究对象,采用空气催化氧化-ClO2助氧化相结合的方法,探讨了药用辛醇废水的处理方法.结果表明,该方法能有效的去除废水中的有机污染物,实现废水处理的资源化回收利用.处理后的废水中CODCr浓度达到国家排放标准(CODCr≤1 50 mg/L). 相似文献
36.
37.
二氧化氯是一种具有高氧化性和强消毒性的化合物,介绍了二氧化氯制备的化学法、电解法以及电化学法,并对几种工艺方法的优缺点进行了分析和比较,适合工业化生产的工艺主要是化学法中的氯酸钠法和亚氯酸钠法。 相似文献
38.
The formation and fate of chlorinated organic substances in temperate and boreal forest soils 总被引:1,自引:0,他引:1
Nicholas Clarke Květoslava Fuksová Milan Gryndler Zora Lachmanová Hans-Holger Liste Jana Rohlenová Reiner Schroll Peter Schröder Miroslav Matucha 《Environmental science and pollution research international》2009,16(2):127-143
Background, aim and scope Chlorine is an abundant element, commonly occurring in nature either as chloride ions or as chlorinated organic compounds
(OCls). Chlorinated organic substances were long considered purely anthropogenic products; however, they are, in addition,
a commonly occurring and important part of natural ecosystems. Formation of OCls may affect the degradation of soil organic
matter (SOM) and thus the carbon cycle with implications for the ability of forest soils to sequester carbon, whilst the occurrence
of potentially toxic OCls in groundwater aquifers is of concern with regard to water quality. It is thus important to understand
the biogeochemical cycle of chlorine, both inorganic and organic, to get information about the relevant processes in the forest
ecosystem and the effects on these from human activities, including forestry practices. A survey is given of processes in
the soil of temperate and boreal forests, predominantly in Europe, including the participation of chlorine, and gaps in knowledge
and the need for further work are discussed.
Results Chlorine is present as chloride ion and/or OCls in all compartments of temperate and boreal forest ecosystems. It contributes
to the degradation of SOM, thus also affecting carbon sequestration in the forest soil. The most important source of chloride
to coastal forest ecosystems is sea salt deposition, and volcanoes and coal burning can also be important sources. Locally,
de-icing salt can be an important chloride input near major roads. In addition, anthropogenic sources of OCls are manifold.
However, results also indicate the formation of chlorinated organics by microorganisms as an important source, together with
natural abiotic formation. In fact, the soil pool of OCls seems to be a result of the balance between chlorination and degradation
processes. Ecologically, organochlorines may function as antibiotics, signal substances and energy equivalents, in descending
order of significance. Forest management practices can affect the chlorine cycle, although little is at present known about
how.
Discussion The present data on the apparently considerable size of the pool of OCls indicate its importance for the functioning of the
forest soil system and its stability, but factors controlling their formation, degradation and transport are not clearly understood.
It would be useful to estimate the significance and rates of key processes to be able to judge the importance of OCls in SOM
and litter degradation. Effects of forest management processes affecting SOM and chloride deposition are likely to affect
OCls as well. Further standardisation and harmonisation of sampling and analytical procedures is necessary.
Conclusions and perspectives More work is necessary in order to understand and, if necessary, develop strategies for mitigating the environmental impact
of OCls in temperate and boreal forest soils. This includes both intensified research, especially to understand the key processes
of formation and degradation of chlorinated compounds, and monitoring of the substances in question in forest ecosystems.
It is also important to understand the effect of various forest management techniques on OCls, as management can be used to
produce desired effects. 相似文献
39.
40.
水中二氧化氯,氯,亚氯酸根和氯酸根区分测定法 总被引:7,自引:1,他引:6
为了保护人类健康制定卫生规范,同时为ClO2的研究和应用提供基础手段,必须要建立一种能准确区分测定水中ClO2,Cl2,ClO^-12,ClO^-3浓度的方法。回顾了现有水中ClO2,Cl2,ClO^-2和ClO^-3的区分测定方法,评述了各种测定方法的优缺点和适用性,指出了目前在区分测定这恨氧化物的方法中存在的问题,提出了解决问题的途径。 相似文献