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301.
M. Srensen M. D. Hurley T. J. Wallington T. S. Dibble O. J. Nielsen 《Atmospheric environment (Oxford, England : 1994)》2002,36(39-40)
Smog chamber/FTIR techniques were used to study the relative reactivity of OH radicals with methanol, ethanol, phenol, C2H4, C2H2, and p-xylene in 750 Torr of air diluent at 296±2 K. Experiments were performed with, and without, 500–8000 μg m−3 (4000–50 000 μm2 cm−3 surface area per volume) of NaCl, (NH4)2SO4 or NH4NO3 aerosol. In contrast to the recent findings of Oh and Andino (Atmospheric Environment 34 (2000) 2901, 36 (2002) 149; International Journal of Chemical Kinetics 33 (2001) 422) there was no discernable effect of aerosol on the rate of loss of the organic compounds via reaction with OH radicals. Gas kinetic theory arguments cast doubt upon the findings of Oh and Andino. The available data suggest that the answer to the title question is “No”. As part of this work the rate constants for reactions of OH radicals with methanol, ethanol, and phenol in 750 Torr of air at 296 K were determined to be: kOH+CH3OH=(8.12±0.54)×10−13, kOH+C2H5OH=(3.47±0.32)×10−12 and kOH+phenol=(3.27±0.31)×10−11 cm3 molecule−1 s−1. 相似文献
302.
采用共沉淀法制备了铁锰双金属复合催化剂(MnFe2O4),用于活化过一硫酸盐(PMS)产生强氧化性的硫酸根自由基(SO4-·)氧化降解水中阴离子表面活性剂(LAS).采用傅立叶变换红外光谱仪(FTIR)、X射线粉末衍射仪(XRD)、扫描电子显微镜(SEM)对催化剂进行表征,表明成功合成了具有尖晶石结构的MnFe2O4催化剂.考察了催化剂投加量、PMS投加量以及初始pH值等各种因素条件对LAS的降解效率以及反应动力学的影响.实验结果表明,MnFe2O4活化PMS降解LAS的过程符合准一级动力学(R2>0.9).在LAS初始浓度为80mg/L,催化剂投加量为2.0g/L,PMS的浓度为2.5mmol/L,初始pH值为7.0,反应时间为30min的情况下,LAS降解效率达到94.1%,此时LAS的降解速率常数达到0.192min-1.通过自由基猝灭实验证明了MnFe2O4/PMS体系中起主要氧化降解作用的活性自由基为SO4-·.通过反应前后催化剂的X射线光电子能谱(XPS),证实Fe和Mn之间存在协同作用,提高了MnFe2O4对PMS的活化效率. 相似文献
303.
采用鼠李糖脂构建逆胶束体系,并利用电子自旋共振(ESR)技术研究了鼠李糖脂逆胶束及鼠李糖脂逆胶束酶体系的性能.采用ESR光谱技术计算得出逆胶束体系中超精细分裂常数变化,研究表明鼠李糖脂在正己烷中的临界胶度为0.07mmol/L.通过分析ESR光谱中旋转相关时间的变化,探究电子自旋探针在逆胶束中运动受阻和翻转所需时间的情况同时,ESR光谱的峰值体现了样品中自由基含量的多少.通过对比逆胶束体系、逆胶束酶体系以及逆胶束酶-苯酚体系的ESR光谱,结果表明鼠李糖脂逆胶束-苯酚体系的自由基最多.通过研究对16-氮氧自由基硬脂酸对两个体系作用,推测出电子自旋探针自由基团定位于逆胶束水核中,并且推断电子自旋探针位于水核的边缘区域,即结合水水层.该研究为逆胶束酶体系的应用提供了坚实的理论基础. 相似文献
304.
目的搭建一套近红外光腔衰荡光谱测量系统,实现水汽吸收的探测。方法通过测量有无样品存在时的衰荡时间,实现腔内介质吸收的探测。通过测量空腔衰荡时间,计算腔镜反射率。通过测量不同浓度的水汽吸收,验证系统是否可用于分子吸收的测量。结果该装置的空腔衰荡时间约为3.75μs,对应的腔镜反射率为99.982%,有效吸收光程为1.1 km。测量了6627.7 cm~(-1)处水汽的吸收,结果与HITRAN数据库一致。结合文献报道结果和HITRAN数据库吸收谱线,模拟得到了NH_3、C_2H_2、HO_2自由基在6625~6626 cm~(-1)范围内的吸收系数。结论该装置实现了水汽吸收的探测,在该装置的激光器工作波长范围内,可应用于NH_3、C_2H_2、HO_2自由基的实时探测。 相似文献
305.
Detomaso A Lopez A Lovecchio G Mascolo G Curci R 《Environmental science and pollution research international》2003,10(6):379-384
BACKGROUND: Chlorophenols (CPs) constitute a group of organic pollutants that are introduced into the environment as a result of several man-made activities, such as uncontrolled use of pesticides and herbicides, and as byproducts in the paper pulp bleaching. Promising removal technologies of chlorinated aromatics consist in the application of advanced oxidation processes (AOPs) that can provide an almost total degradation of a variety of contaminants. Among these, wide application find Fenton systems based on generation of reactive species having a high oxidizing power, such as hydroxyl radical HO*. Our objective was that of determining the overall degradation efficiency of the model compound 2,4-dichlorophenol (DCP) by thermal Fenton-type oxidation systems with a view toward defining in more details relevant process parameters, the effect of reaction temperature and of co-catalyst Cu2+. METHODS: Reaction conditions were similar to those generally adopted as optimal in many practical applications, i.e. pollutant/Fe2+ (as FeSO4) ratio ca. 20, Fe2+/Cu2+ (co-catalyst) 2:1, pH adjusted and controlled at pH 3, and H2O2 in excess (up to four-fold over the stoichiometric amount required for complete mineralization). RESULTS AND DISCUSSION: The results demonstrate that it is advantageous to carry out the reaction at a temperature markedly higher (70 degrees C) than ambient. The stepwise addition of H2O2 in aliquots yields an efficient transformation, while allowing a convenient control of the reaction exothermicity. Under these conditions, the essentially complete removal of the initial DCP is accomplished using just one equiv of H2O2 during 15 min; excess H2O2 (5 equivalents) yields extensive substrate mineralization. Also relevant, at 70 degrees C dechlorination of the initial DCP (and of derived reaction intermediates) is remarkably extensive (3-5% residual TOX), already with the addition of 1 equiv of H2O2. At the end of the reaction, IC and IC-MS analyses of the solution reveal that only low-molecular weight carboxylic acid (acetic, formic, oxalic, malonic, tartaric, etc.) contribute to the residual TOC. CONCLUSIONS: The whole of the results herein point to the advantage of performing the process at temperatures substantially higher than ambient (70 degrees C). Under the conditions adopted, almost complete degradation of the initial toxic compound can be achieved using hydrogen peroxide in fair excess (e.g., 3.5 equiv H2O2). RECOMMENDATIONS AND OUTLOOK: In applying practical Fenton-type degradation systems to heavily polluted wastes, either for the pre-treatment of waters with a high COD value prior to biodegradation or for complete mineralization of pollutants, the set up of appropriate reaction conditions appears to be a key factor. Also, it is desirable to keep the concentration of iron salts within the lower limits in order to minimize the production and disposal of iron oxide sludges. 相似文献
306.
307.
大气氢氧自由基测量技术研究进展 总被引:2,自引:0,他引:2
大气氢氧自由基在对流层大气化学中占有重要地位,但由于其浓度极低而活性极高,所以至今没有合适的测量方法。文章通过总结20多年来大气氢氧自由基测量技术研究的成果,分析讨论了大气氢氧自由基浓度测量的研究现状和发展趋势。 相似文献
308.
该文分析了饮用水消毒的现状,提出保持氯消毒不变,用羟基自由基氧化法对饮用水进行后处理,去除氯消毒产生的卤代烃,以提高饮用水的质量。 相似文献
309.
310.
A new method of determining the cumulate concentration of hydroxyl radicals in the TiO2/Ti photoelectrocatalytic(PEC)oxidation system was established by o-phenanthroline-Fe(Ⅱ)(Fe(phen)32+) spectrophotometry and using anion 相似文献