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161.
Ji-Dong Gu D. Eberiel S. P. McCarthy R. A. Gross 《Journal of Polymers and the Environment》1993,1(4):281-291
Residual cellulose acetate (CA) films with initial degree of substitution (DS) values of 1.7 and 2.5 (CA DS-1.7 and DS-2.5) were recovered from a simulated thermophilic compost exposure and characterized by gel permeation chromatography (GPC), proton nuclear magnetic resonance (1H NMR), and scanning electron microscopy (SEM) to determine changes in polymer molecular weight and DS and to study microbial colonization and surface morphology, respectively. During the aerobic degradation of CA DS-1.7 and CA DS-2.5 films exposed for 7 and 18 days, respectively, the number-average molecular weight (M
n) of residual polymer decreased by 30.4% on day 5 and 20.3% on day 16, respectively. Furthermore, a decrease in the degree of substitution from 1.69 to 1.27 (4-day exposure) and from 2.51 to 2.18 (12-day exposure) was observed for the respective CA samples. In contrast, CA films (DS-1.7 and DS-2.5) which were exposed to abiotic control vessels for identical time periods showed no significant changes inM
n and DS. SEM photographs of CA (DS-1.7 and DS-2.5) film surfaces after compost exposures revealed severe erosion and corresponding microbial colonization. Similar exposure times for CA films in abiotic control vessels resulted in only minor changes in surface characteristics by SEM observations. The conversion of CA DS-1.7 and DS-2.5 to CO2 was monitored by respirometry. In these studies, powdered CA was placed in a predigested compost matrix which was maintained at 53°C and 60% moisture content throughout the incubation period. A lag phase of 10- and 25-day duration for CA DS-1.7 and DS-2.5, respectively, was observed, after which the rate of degradation increased rapidly. Mineralization of exposed CA DS-1.7 and DS-2.5 powders reported as the percentage theoretical CO2 recovered reached 72.4 and 77.6% in 24 and 60 days, respectively. The results of this study demonstrated that microbial degradation of CA films exposed to aerobic thermophilic laboratory-scale compost reactors not only results in film weight loss but also causes severe film pitting and a corresponding decrease in chainM
n and degree of substitution for the residual material. Furthermore, conversions to greater than 70% of the theoretical recovered CO2 for CA (DS 1.7 and 2.5) substrates indicate high degrees of CA mineralization.Guest Editor: Dr. Graham Swift, Rohm & Haas. 相似文献
162.
Glyphosate (N-phosphonomethyl glycine) is the most used herbicide worldwide. The degradation of 14C-labeled glyphosate was
studied under controlled laboratory conditions in three di erent agricultural soils: a silt clay loam, a clay loam and a sandy loam soil.
The kinetic and intensity of glyphosate degradation varied considerably over time within the same soil and among di erent types of
soil. Our results demonstrated that the mineralization rate of glyphosate was high at the beginning of incubation and then decreased
with time until the end of the experiment. The same kinetic was observed for the water extractable residues. The degradation of
glyphosate was rapid in the soil with low adsorption capacity (clay loam soil) with a short half-life of 4 days. However, the persistence
of glyphosate in high adsorption capacity soils increased, with half-live of 19 days for silt clay loam soil and 14.5 days for sandy
loam soil. HPLC analyses showed that the main metabolite of glyphosate, aminomethylphosphonic acid (AMPA) was detected after
three days of incubation in the extracts of all three soils. Our results suggested that the possibility of contamination of groundwater by
glyphosate was high on a long-term period in soils with high adsorption capacity and low degrading activities and/or acid similar to
sandy loam soil. This risk might be faster but less sustainable in soil with low adsorption capacity and high degrading activity like the
clay loam soil. However, the release of non-extractable residues may increase the risk of contamination of groundwater regardless of
the type of soil. 相似文献
163.
采用UV/H2O2/微曝气工艺对水中内分泌干扰物双酚A(BPA)的降解与矿化进行了试验研究.该工艺是在UV/H2O2的基础上发展起来的一种新工艺,微曝气在UV光照射下产生了一定量的O3,提高了·OH的发生率.本试验研究了UV光强、H2O2投加量以及pH值对BPA矿化速率的影响.结果表明,随着UV光强的增大,BPA的矿化速率呈线性增加;当H2O2投加量由5 mg/L增大到20 mg/L时,BPA矿化速率常数k由0.003 2上升到0.025 0;当pH为6.68时,在相同条件下BPA的矿化效果最好.在同一工况条件下,UV/H2O2/微曝气工艺降解BPA的速率远远大于其矿化速率,分析得出在开始反应阶段BPA首先被降解为小分子有机物,随着反应的进一步进行小分子有机物逐步被矿化为无机物. 相似文献
164.
The direct and sensitized photodegradations of imidacloprid, 1-(6-chloro-3-pyridinylmethyl)-N-nitro-2-imidazolidinimine, were investigated in aqueous solution and with and without various photo-sensitizers. Results of the study revealed that the intensity of lamp-house and irradiation wavelength had significant effects on the photolysis of imidacloprid. Complete degradation of 20 mg/L imidacloprid in aqueous phase was observed in 40 min under ultraviolet(UV) irradiation system, suggesting the ultraviolet ray played significant role in direct photolysis of imidacloprid. The additions of various photo-sensitizers lead to improve the degradation efficiency of imidacloprid under the irradiation of black light fluorescent lamp. TiO2 was the most efficient in the photo-catalytic degradation of imidacloprid among other photo-sensitizers in used this study. However, addition of acetone inhibited the photolysis of imidacloprid under the irradiation of UV, indicating the occurrence of competition between acetone and imidacloprid for photos. Mineralization of the imidacloprid was examined to clarify the final photochemical degradation products of the insecticide which were CO2, CI^- and NO3^-. Complete photo-oxidation of nitrogen to NO3^- occurred very slowlyvia the intermediate formation of NH4^ and NO2^- . 相似文献
165.
为研究甜椒根际土壤中氮的行为,与既报同样的方法进行研究,即,利用15NH4+,15NO3-双标记的硝胺(NH,4>15NO3,15NH4NO3),在温室里对甜椒进行6周的根箱栽培.收割后,对土壤全氮,NO3-N,水溶性NH4-N,KCl抽出NH4-N和其各自的15N atom%进行测定.结果表明,土壤全氮从非根际到根际逐渐增加,与栽培前相比,土壤全氮在非根际中减少,却在根际中增大.土壤NO3-N浓度朝根际增加到离根际2 mm处,然后激减到根际.NO3-N的来自施给NO3-N的比例靠近根际逐渐升高,在根际达到了69%,反而,来自施给NH4-N的比例靠近根际逐渐降低,在根际将至7%左右.水溶性NH4-N和KCl抽出NH4-N浓度靠近根际逐渐降低,而且,从非根际到根际,二者匀保持3∶10的比例.KCl抽出NH4-N的来自施给NO3-N的比例靠近根际逐渐升高,但在根际仍低于3%,反而,其来自施给NH4-N的比例在非根际约为47%~55%,在根际降到41%.在整个根箱里,施用NO3-N的有機率达到62%,但其值在根际比非根圈要低.相反,施用NH4-N的有機率仅11%左右,但其值在根际比非根际要高.以上结果表明,在甜椒根际土壤中氮的无机化-有机化活性与水稻相比显著低. 相似文献
166.
167.
研究了苯酚在新型臭氧氧化体系O_3-Ca(OH)_2体系中的降解与矿化效果。实验结果表明:苯酚及TOC的去除率都随着Ca(OH)_2用量(小于2 g/L)、进气臭氧质量浓度(小于75 mg/L)、进气流量(小于3.0 L/min)的增大以及初始苯酚质量浓度的减小而增加,但受反应压力和液相温度的影响较小;当Ca(OH)_2用量大于3 g/L时,苯酚和TOC的去除率在30 min和55 min时分别达到了100%左右;Ca~(2+)的存在实现了羟基自由基清除剂CO_3~(2-)的实时分离去除,从而强化了臭氧氧化过程中苯酚的降解与矿化。这表明,O_3-Ca(OH)_2体系是一种处理难降解有机废水的高效臭氧氧化新体系。 相似文献
168.
Karsten E. Braun Burkhard Schmidt 《Journal of environmental science and health. Part. B》2017,52(2):122-130
The fate of 14C-labeled herbicide prosulfocarb was studied in an agricultural soil and in a sediment-water system, the sediment part of which was derived from Yangtze Three Gorges Reservoir, China. Time-course studies were performed for 28 d and 49 d, respectively. Main transformation routes of 14C-prosulfocarb were mineralization to 14CO2 and formation of nonextractable residues amounting to 12.13% and 10.43%, respectively, after 28 days (soil), and 9.40% and 11.98%, respectively, after 49 d (sediment-water system). Traces of prosulfocarbsulfoxide were detected by means of TLC, HPLC, and LC-MS; other transformation products were not found. Initial extraction of soil assays using 0.01 M CaCl2 solution showed that the bioavailability of the herbicide was considerably low; immediately after application (0.1 d of incubation), only 4.78% of applied radioactivity were detected in this aqueous fraction. DT50 values of 14C-prosulfocarb estimated from radio-TLC and -HPLC analyses were above 28 d in soil and ranged between 29 d and 49 d in the sediment-water system. Partitioning of 14C from water to sediment phase occurred with DT50 slightly above 2 d. With regard to the sediment-water system, adsorption occurred with log Koc = 1.38 (calculated from 2 day assays) and 2.35 (49 d assays). As similarly estimated from portions of 14C found in CaCl2 extracts of the 0.1 d assays, 14C-prosulfocarb's log Koc in soil was 2.96. With both experiments, similar portions of nonextractable radioactivity were associated with all soil organic matter fractions, i.e. nonhumics, fulvic acids, humic acids, and humin/minerals. Throughout all sample preparation, the experiments were severely impaired by losses of radioactivity especially with concentration of samples containing water in vacuo. All findings pointed to volatility of parent prosulfocarb in presence of water rather than volatility of transformation products. According to literature data, this behavior of prosulfocarb was not expected, though volatility was demonstrated under field conditions. 相似文献
169.
170.
以自制的介孔γ-A12O3为载体,通过等体积浸渍法合成了MnOx/介孔γ-A12O3催化剂。采用X射线衍射(XRD)、透射电镜(TEM)以及紫外一可见漫反射(uV—VisDRS)等手段对其进行表征。结果表明,锰氧化物在介孔氧化铝载体上具有较高的分散度,并且锰以多种价态存在。高度分散以及多价态的MnOx能够提高催化臭氧化过程中电荷转移,引起更高的催化活性。MnOx/介孑γ-A12O3催化剂能够有效地提高臭氧对水中安替比林的矿化效果,对含量为10mg/L的安替比林水溶液在反应60min后基本达到完全矿化。 相似文献