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41.
The antioxidant activity of the microalgal ethanolic extracts of Porphyridium cruentum, Phaeodactylum tricornutum and Chlorella vulgaris was determined by means of the β-carotene–linoleate model system. The results show that the activity of C. vulgaris extract was higher than those obtained for the other microalgal extracts tested and for the synthetics BHA (butylated hydroxyanisole), and BHT (butylated hydroxytoluene). In addition, the major constituents present in the ethanolic extracts of the three microalgae species were analyzed by means of GC and GC–mass spectrometry. The results showed that the tested microalgae may be an important source of natural antioxidants, as an alternative to higher plants or the production by chemical synthesis. 相似文献
42.
Guilhem Pagès Alireza Salehi M. Sergey V. Dvinskikh Mats K.G. Johansson István Furó 《Progress in Organic Coatings》2012
Despite having been used for ages to protect wood against the influence of outdoor elements, the chemistry of vegetable oils within wood is poorly known. We propose a method based on solid-state magic-angle sample spinning NMR to in situ characterize oil oxidation as well as its immobilization. To eliminate signal coming from wood molecules but to keep signal from the oil, direct 13C excitation is performed with low-power 1H decoupling during signal acquisition. To suppress the effect of anisotropic spin-interactions and magnetic field inhomogeneity, the sample is spun at the magic-angle. Mono- and polyunsaturated fatty acid derivatives show a difference in their oxidation process: the monounsaturated methyl oleate reacts with wood components and becomes immobilized while the polyunsaturated methyl linoleate becomes oxidized and form oligomers but does not seem to bind to wood. Linola® oil behaves as would be expected on the basis of its composition by monounsaturated and polyunsaturated chains. This method can be generalized to all coating treatments to characterize chemical pathways and reactions. A better understanding of coating effects on wood is a crucial step to design more efficient protective mixtures. 相似文献
43.
研究采用DEAE-Sepharose F.F离子交换层析和Sephadex G-100凝胶过滤层析对嗜酸乳杆菌发酵液中的亚油酸异构酶进行了分离纯化,酶回收率为6.39,纯化倍数为37.9倍。经研究确定酶最适pH为6.0,最适反应温度为30℃。在pH 6~8之间,亚油酸异构酶可保持较高活力,超出此范围,酶活力明显下降;该酶对高温敏感,50℃保温2 h,酶活力即变得很低;亚油酸异构酶受底物LA的抑制,酶反应最适LA浓度为1.5×10-5g/mL,过高LA则对酶产生抑制作用。 相似文献
44.
A. G. Gopala Krishna J. V. Prabhakar 《Journal of the American Oil Chemists' Society》1994,71(11):1245-1249
The components responsible for increased stability of raw peanut oil at a high relative humidity (RH) of 91% were examined
in peanut oil and methyl linoleate systems. Of the constituents, the native gums, which were mostly phospholipids and glycolipids,
showed increased antioxidant activity at 91% RH. The isolated components of the gums, namely phospholipids and glycolipids,
were prooxidant individually or in combination. Tocopherols did not show increased antioxidant activity at 91% RH. 相似文献
45.
Marja P Khknen Johanna Heinmki Velimatti Ollilainen Marina Heinonen 《Journal of the science of food and agriculture》2003,83(14):1403-1411
Anthocyanins from bilberry, blackcurrant and cowberry were isolated for antioxidant evaluation. Individual compounds were identified and quantified using HPLC and HPLC/ESI–MS techniques. Antioxidant and radical‐scavenging capacities of the isolates were studied in emulsified methyl linoleate and human low‐density lipoprotein (LDL) in vitro and in the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) test. The total anthocyanin contents in the phenolic extracts of bilberry, blackcurrant and cowberry were 6000, 2360 and 680 mg kg?1 fresh weight respectively. There were four dominant compounds in blackcurrant (glucosides and rutinosides of cyanidin and delphinidin), three in cowberry (monoglycosides of cyanidin) and 15 in bilberry (monoglycosides of cyanidin, delphinidin, malvidin, peonidin and petunidin). Quantification as cyanidin‐3‐glucoside equivalents gave markedly lower results regarding the total anthocyanin concentration and the content of individual delphinidin and malvidin compounds compared with quantification based on corresponding standard compounds. Berry anthocyanins were highly active radical scavengers in the DPPH test and effective antioxidants in emulsion and human LDL. Copyright © 2003 Society of Chemical Industry 相似文献
46.
George J. Piazza Thomas A. Foglia Alberto Nuñez 《Journal of the American Oil Chemists' Society》1996,73(8):1045-1049
Lipoxygenase (EC 1.13.11.12) catalyzes the reaction between oxygen and polyunsaturated fatty acids to give fatty acid hydroperoxides.
Recent work showed that soybean lipoxygenase 1 can oxidize diacylglycerols when deoxycholate is present in the reaction medium.
Conditions were sought to maximize 1,3-dilinolein oxidation with a commercial soybean lipoxygenase preparation. It was found
that dilinolein was oxidized most rapidly in a multicomponent buffer medium that contained 10 mM deoxycholate between pH 8
and 9. When dilinolein oxidation was conducted in the individual components of the multicomponent buffer, the oxidation rate
decreased two- to threefold. Addition of 0.2 M NaCl to one of the components, Tricine buffer, caused a twofold increase in
the oxidation rate, demonstrating that high ionic strength is a major factor promoting rapid oxidation in the multicomponent
buffer. In the deoxycholate multicomponent buffer, the order of reactivity toward oxidation was monolinolein>methyl linoleate≈
linoleic acid>dilinolein. Competition experiments in which mixtures of the substrates were presented simultaneously to lipoxygenase
in the presence of deoxycholate showed that linoleic acid was the most reactive substrate. When no surfactant was present
or when the surfactant was Tween 20, linoleic acid was the most rapidly oxidized substrate. Overall, the results demonstrate
that monolinolein and methyl linoleate are just as reactive, or more so, as linoleic acid to oxidation by lipoxygenase under
specified reaction conditions. In competition experiments, linoleic acid oxidation predominates, probably because its free
carboxyl functionality allows it to be preferentially bound to the active site of lipoxygenase. 相似文献
47.
48.
Transesterification of phytosterol and edible oil by lipase powder at high temperature 总被引:2,自引:0,他引:2
Satoshi?NegishiEmail author Ichiro?Hidaka Isamu?Takahashi Shigeru?Kunita 《Journal of the American Oil Chemists' Society》2003,80(9):905-907
Phytosterol, which is hardly soluble in edible oil, was solubilized at a high concentration by converting it to FA esters
by lipase-catalyzed transesterification at temperatures higher than 100°C using powdered Lipase QLM (Meito Sangyo Co., Ltd.,
Nagoya, Japan). Transesterification was conducted, in sunflower oil containing 10% phytosterol, without adding water or solvent,
at 100°C. The conversion rate was 97.1% after 7 h of reaction. The effect of temperature on the conversion rate was also examined.
Maximum enzyme activity occurred in the 100–120°C range, and 20% of the maximum activity was retained even at 130°C. When
the lipase was recovered by filtration and recycled for repeated reactions at 90°C, the half-life of lipase activity was 260
h. Thus, edible oils with nutritional value could be produced by blending the phytosterol-containing sunflower oil into other
edible oils. 相似文献
49.
培养条件对一株嗜酸乳杆菌突变株亚油酸异构酶活力的影响 总被引:1,自引:0,他引:1
对一株嗜酸乳杆菌突变株产亚油酸异构酶的条件进行了研究,得到最佳产酶条件为:以脱脂乳作为培养基,添加3%的乳糖、1%的(NH4)2SO4、0 1%的亚油酸及1%的NaCl,接种量为1%,培养时间为36h.在此条件下,所合成的亚油酸异构酶活力达252 0U/mL. 相似文献
50.
Aziz?Tekin Earl?G.?HammondEmail author 《Journal of the American Oil Chemists' Society》2004,81(5):481-485
Methyl linoleate with 5% by weight of methyl palmitate as an internal standard was deposited as a monolayer (20% by weight)
on Silica gel H and oxidized at 7,25, and 40°C. Oxidation was followed by iodometric PV practiced directly on aliquots of
the silica gel. Lower temperatures gave higher PV maxima but after longer times. Oxidation of methyl linoleate at all three
temperatures followed first-order kinetics, and the energy of activation was 15.0 kcal/mol. The products recovered from the
chloroform-acetic acid layer of the peroxide determination were analyzed by GC and identified by El- and CI-MS. Calculation
based on methyl palmitate as an internal standard showed that the total peak area decreased to about 40% that of the original
methyl linoleate when the residual methyl linoleate was reduced to less than 2%. The chief nonscission products (NSP) of linoleate
oxidation were epoxy, hydroxy, hydroxy-epoxy, dihydroxy, and trihydroxy methyl esters. The greatest NSP concentrations were
obtained about the time of the greatest PV, and the yield at 40°C was greater than those at 7 and 25°C. Scission products
(SP) increased rapidly until the greatest PV was reached. After this time, SP declined slightly and plateaued at 40°C, but
at 7 and 25°C, SP continued to increase slowly with further oxidation. 相似文献