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排序方式: 共有133条查询结果,搜索用时 31 毫秒
101.
亚硫酸盐氧化失效机理研究 总被引:1,自引:0,他引:1
通过模拟贮存试验,了亚硫酸盐失效原因及防止方法。结果表明,目前广泛应用的亚硫酸盐法防止氧腐蚀效果有时不佳的原因主要是亚硫酸盐溶液在期间的氧化。 相似文献
102.
103.
邻苯三酚自氧化法测定抗氧化活性的方法研究 总被引:14,自引:0,他引:14
通过对邻苯三酚自氧化反应体系的光谱吸收、缓冲液pH值和邻苯三酚浓度对自氧化速率的影响进行研究,建立邻苯三酚自氧化-分光光度法最佳应用体系。确定反应体系总体积为3mL,检测波长在319nm时的测定条件为:缓冲液pH值7.3,邻苯三酚浓度60mmol/L,自氧化速率可达0.060△A/min,线性时间4min;检测波长在420nm时的测定条件为:缓冲液pH值7.8,邻苯三酚浓度80mmol/L,自氧化速率可达0.050△A/min、线性时间3min。新方法建立的紫外和可见光两种检测波长体系,可针对样品的吸收光谱特征选择检测波长,避免了样品自身吸收强对测定检测限的影响,测定pH值接近生物体内真实条件,自氧化速率为最佳检测值且线性时间良好。 相似文献
104.
荸荠皮提取物的抗氧化活性研究 总被引:2,自引:0,他引:2
用邻苯三酚自氧化法、Feton反应法、Na_2S_2O_3-I_2滴定法研究了荸荠皮提取物的抗氧化活性。结果表明:荸荠皮提取物的有明显的抗氧化活性,当浓度为0.10g/L时,对超氧高子自由基(O_2~-·)的抑制率为48.45%,对羟自由基(·OH)的清除率为67.52%,其0.1%提取物对猪油的抗氧化效果优于0.02%的抗氧化剂BHT,且其活性具有剂量效应关系。荸荠皮提取物是一种应用前景广阔的具有抗氧化活性的天然资源。 相似文献
105.
Ground, blanched, raw, and roasted peanuts with varying oil contents were analyzed for oxidation products. Peroxide values (PV) of blanched, ground raw (BRAW) peanuts, demonstrating enzymatic oxidation, and heat-treated rancid roasted peanuts (RRST), demonstrating autoxidation, exhibited decreases (p ≦ 0.05) with decreasing oil content. The Oxidative Stability Index (OSI) time at 110 °C increased (p < 0.05) with decrease in oil content of raw (BRAW) and roasted (BRST) ground peanuts. A higher OSI indicated more oxidative stability, thereby supporting the hypothesis of higher potential for autoxidation at higher oil contents. In addition, BRST exhibited a shorter OSI than BRAW, indicating slower autoxidation in BRAW. Roasted peanutty odor, burnt odor, and roasted peanutty flavor, rancid/oxidized flavor, and burnt flavor scores of rancid roasted peanuts decreased (p ≦ 0.05) with decreasing oil content. 相似文献
106.
A methanolic extract of Noble oat (Avena sativa L.) was tested for its antipolymerization activity in soybean and cottonseed oils heated to 180°C for 10 h per day for 10
d and for its carry-through properties in fried bread cubes. The soybean and cottonseed oils containing 0.005 or 0.007% oat
extract (based on total phenolic content) formed significantly lesser amounts of polar compounds with high molecular weight
than did the oils containing 0.02% tertiary butyl hydroquinone (TBHQ), 1 ppm dimethylpolysiloxane (DMS) and oils containing
no additives (control) as measured by high-performance size-exclusion chromatography. Fatty acid composition, also monitored,
showed that oils with either level of oat extract maintained a significantly higher linoleic-to-palmitic acid ratio (18∶2/16∶0)
than did the other treatments. Oil extracted from bread cubes fried (180°C) in oils containing TBHQ and oat extract and then
stored at 60°C in the dark for up to 14 d had significantly lower (P≤0.05) peroxide values and higher (P≤0.05) 18∶2/16∶0 ratios than did oil extracted from cubes fried in oil containing DMS and in the control oil. 相似文献
107.
The effect of α-tocopherol (αTOH) (50–2000 ppm), γ-tocopherol (γTOH) (100–2000 ppm), and δ-tocopherol (δTOH) (100–2000 ppm)
on the formation and decomposition of hydroperoxides in purified fish oil triacylglycerols (TAG) was studied. The tests were
conducted at 30°C in the dark. Purified fish oil TAG oxidized very rapidly with no apparent induction period. The relative
ability of the tocopherols to retard the formation of hydroperoxides decreased in the order αTOH> γTOH>δTOH at a low level
of addition (100 ppm), but a reverse order of activity was found when the initial tocopherol concentration was 1000 ppm. This
dependence of relative antioxidant activity on tocopherol concentration was caused by the existence of concentrations for
maximal antioxidant activity for αTOH and for γTOH. An inversion of activity, on the basis of hydroperoxide formation, was
observed for αTOH at 100 ppm and for γTOH at 500 ppm, whereas the antioxidant activity of δTOH increased with level of addition
up to 1500–2000 ppm. None of the tocopherols displayed any prooxidant activity. All three tocopherols strongly retarded the
formation of volatile secondary oxidation products in a concentration-dependent manner. At concentrations above about 250
ppm there appeared to be a linear relationship between rate of consumption of αTOH and initial αTOH concentration, in accordance
with the linear relationship observed between the initial rate of formation of hydroperoxides and the initial αTOH concentration.
The rate of consumption of γTOH also increased with initial concentration, but to a lesser extent than for αTOH. At high levels
of addition the rate of consumption of δTOH was independent of initial concentration, appearing to reflect the greater stability
of this tocopherol homolog and participation in reactions with lipid peroxyl radicals only.
Presented in part at the AOCS annual meeting in San Diego, California, April 2000. 相似文献
108.
109.
Walt Partenheimer 《Advanced Synthesis \u0026amp; Catalysis》2004,346(12):1495-1500
DMtoluene (3,4‐dimethoxytoluene; DM=3,4‐dimethoxy), a model compound for lignin oxidation, can be autoxidized in acetic acid using a Co/Mn/Br catalyst to its benzaldehyde in 51 mol % yield, and to its acid in 85–92 mol % yield. This synthesis is unusual because a number of unprecedented phenomena occur. 1) The rate of molecular oxygen reacting with the substrate is bi‐phasic, i.e., two maximum in the rate of reaction are observed. 2) In the first phase, all of the 3,4‐dimethoxytoluene is converted to intermediates, but very little to the carboxylic acid. 3) During the second maximum of activity, virtually all the intermediates are converted to the carboxylic acid with 95–100% mass accountability. 4) The rate of carbon monoxide and carbon dioxide formation is considerably higher during the second phase during which 5) 9–12% of methyl 3,4‐dimethoxybenzoate (the methyl ester of the benzoic acid) is formed. Mechanisms are suggested for these unusual phenomena. 相似文献
110.