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81.
Tatsuo Maruyama Shoji Umezaki Mitsutoshi Nakajima Minoru Seki 《European Journal of Lipid Science and Technology》2002,104(5):255-261
Native lipases often exhibit poor interesterification activity. We previously developed a fatty acid modification method to improve the activity of lipases. In this study, we applied this fatty acid modification method to several lipases and evaluated their interesterification and hydrolytic activities. The resulting interesterification activity was strongly dependent on the modifying fatty acid used. Of the saturated fatty acids tested, stearic acid modification substantially improved the interesterification activity of three lipases. Hydrolytic activity was affected slightly by the modifying fatty acid used. Substrate specificity of the modified lipase with triglycerides was also investigated and it was found that fatty acid modification changed the substrate specificity of some lipases. 相似文献
82.
J
M Winterbottom Z Khan S Raymahasay G Knight N Roukounakis 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2000,75(11):1015-1025
The hydrogenation of the triglyceride oil, soya bean oil, has been studied in the temperature range 130–160 °C and in the pressure range 100–600 kPa using (i) a 5% w/w Pd/C slurry catalyst and (ii) a 3% w/w Pd/Al2O3 Raschig ring catalyst in a cocurrent downflow contactor (CDC) reactor. Separate studies of residence time distribution (RTD) were carried out in a modified CDC device in order to determine dispersion numbers and dispersion coefficients. The RTD measurements indicated that the overall flow was a mixture of well‐mixed and plug flow for the unpacked CDC, so that the entry section (0–30 cm from entrance) was perfectly mixed and the remainder of the column (30–130 cm) gave predominantly plug flow behaviour. The introduction of random packing in the form of 13 mm Raschig rings gave rise to increased back mixing in the lower part of the CDC and the overall dispersion number increased due to liquid and gas circulation around the packing elements. Kinetic studies revealed an initial rate reaction order of 1.24–1.26 with respect to hydrogen concentration both in slurry and fixed bed CDC reactors and is interpreted as a combination of a parallel pair of first and second order reactions during the initial stages of reaction. Mass transfer coefficients for gas absorption (kLa) and liquid–solid mass transport (ks) were determined for both types of reactor. The kLa values lay in the range 1.0–3.33 s−1 and the liquid–solid transport resistances (XLS) were all <1%, so that the reaction was almost totally surface reaction rate controlled. Apparent energy of activation measurements gave values of EA = 49 ± 6 kJ mol−1, which is strongly indicative of surface reaction rate control involving the hydrogenation of an olefinic double bond. The selectivity in respect of linolenate (three double bonds) removal and linoleate (two double bonds) retention was high with, for palladium, relatively low trans‐isomer production (<30%). The overall selectivity was slightly, but significantly, better for the fixed bed CDC reactor and this is attributed to the greater degree of plug flow behaviour in the latter, despite the bed causing an increase in dispersion number. However, there is no reaction in the well‐mixed section of the fixed bed CDC reactor as there is in the slurry CDC reactor and this is likely to improve selectivity in a consecutive reaction sequence. © 2000 Society of Chemical Industry 相似文献
83.
An investigation was carried out to evaluate the oxidative and hydrolytic degradation of 37 olive‐pomace oils marketed in southern Italy and to compare the results with those obtained from 10 deodorised olive‐pomace oils representative of large stocks of oil obtained after the final step of refining. One aim of the research was to ascertain the quality characteristics of commercial olive‐pomace oils; another was to verify whether the legally prescribed addition of virgin olive oil to refined pomace oil, so that the final product may be classified commercially as olive‐pomace oil, was actually sufficient to justify upgrading. The analytical methods used were silica gel column chromatography and high‐performance size exclusion chromatography. The data obtained showed that the final retail olive‐pomace oils had a lower degree of oxidative degradation than the refined oils, as indicated by the lower values obtained when summing the proportions of triglyceride oligopolymers and oxidised triglycerides. Conversely, hydrolytic degradation, which was evaluated by determining diglycerides, proved to be the same in the two categories of oil. The proportions of virgin olive oil added are small, as indicated by the statistically indistinguishable values of triglyceride oligopolymers and free fatty acids obtained. The possibility of setting a limit to the amount of triglyceride oligopolymers present in the commercial category of olive‐pomace oil has been considered. This limit would ensure standardisation of the level of oxidation and, consequently, of the quality of marketed oils and would enhance differentiation between olive‐pomace oil and refined olive‐pomace oil. © 2000 Society of Chemical Industry 相似文献
84.
85.
Dorota Johansson 《Journal of the American Oil Chemists' Society》1995,72(10):1235-1237
The formation of fat crystal gels in soybean oil has been studied by sedimentation in a low concentration region at 10–25°C.
At 10°C, weak gels were formed with 1% crystals, and no gels formed at concentrations of 2–5%. At temperatures of 15–25°C,
no gels were formed at concentrations of 1–5%, and samples sedimented. Stronger gels of fat crystals were formed with ∼10%
fat crystals at all temperatures examined. Formation of weak gels is a consequence of the fractal nature of fat crystal aggregates
and sediments. At low temperature, the interaction is weak. The fractal dimension is then high, and the floc size is large
for low crystal concentrations. These large flocs form a three-dimensional network that act as a weak gel and withstand gravitational
force. When the temperature is increased, the fat crystal interaction becomes stronger, fractal dimension decreases, and floc
size decreases. Smaller flocs have a higher density, pack more easily, and sediment. Similar effects are observed when the
concentration of fat crystals is increased at low temperature due to a decrease in floc size. 相似文献
86.
One impediment to the industrial use of enzymes in fat and oil transformations is the higher cost often associated with an
enzymatic process compared with the corresponding chemical process. Processes that utilize plant enzymes, however, may have
advantages because of their lower cost and ready availability. One example of such a plant-derived enzyme is Carica papaya latex (CPL), the principal source of the protease papain. Recently, it has been shown that this latex also catalyzes the
lipolysis of triacylglycerols and that this latex lipase has a selectivity for short-chain acyl groups as well as a 1,3-glycerol
selectivity. These selectivities can be used in the synthesis of structured triacylglycerols. In this paper we describe the
utility of CPL in lipase-catalyzed reactions, specifically the synthesis of low-calorie triacylglycerol analogs.
Presented in part at the American Oil Chemists’ Society’s 88th Annual Meeting & Expo, Seattle, WA, May 1997. 相似文献
87.
Shirom Arie; Melamed Samuel; Berliner Shlomo; Shapira Itzhak 《Canadian Metallurgical Quarterly》2009,28(6):649
Objective: The authors hypothesized that high-pleasure low-arousal (HPLA) would predict a subsequent decrease of low-density lipoprotein cholesterol (LDL-C) and triglycerides (TRI), as well as a subsequent increase of high-density lipoprotein cholesterol (HDL-C). The authors also hypothesized that high-pleasure high-arousal (HPHA) would have the opposite effects on these blood lipids, predicting a subsequent increase of LDL-C and TRI, and a decrease of HDL-C. Design: Participants were 990 male and 595 female apparently healthy employees who underwent a routine periodic health examination at two points in time, Time 1 (T1) and Time 2 (T2), about 24 months apart. Data were analyzed separately for the men and women, and the authors controlled for possible confounders shown in past research to be implicated with hyperlipidemia. Main Outcome Measures: HPHA and HPLA were assessed based on the Job-Related Affective Well-Being Scale, while LDL-C, TRI, and HDL-C were assessed based on fasting blood samples. Results: For the men, support for our hypotheses was found relative to HDL-C and TRI. The authors did not find support for our hypotheses for thee women. Conclusion: Our findings suggest that for men, the two types of positive affects may have opposite physiological consequences with respect to subsequent changes in blood lipid levels. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
Viscosity prediction for fatty systems 总被引:5,自引:4,他引:1
Juliana Rabelo Eduardo Batista Fl vio W. Cavaleri Antonio J. A. Meirelles 《Journal of the American Oil Chemists' Society》2000,77(12):1255-1262
Viscosity data have been measured as a function of temperature for two pure polyunsaturated fatty compounds (linoleic acid
and trilinolein), for two multicomponent fatty systems, for a commercial-grade oleic acid (approximately 80% pure), and for
canola oil. The measurements were performed in Cannon Fenske glass capillary kinematic viscometers. The contents of a large
data bank, containing viscosity data for saturated, monousaturated, and polyunsaturated pure fatty substances, were correlated
by an equation based on the number of carbon atoms and double bonds. By using this equation for pure compounds and the UNIMOD
group contribution method for mixtures, the viscosity data for model fatty systems, commercial oleic acid, and canola oil
were predicted. The good results obtained in the present work indicate that this approach can be a valuable tool for designing
or evaluating chemical process equipment for the oil industry. 相似文献
89.
Zhaojuan Shi Lili Cao Shengmei Kang Shaotong Jiang Min Pang 《International Journal of Food Science & Technology》2022,57(4):2003-2014
Camellia oil (CO) and medium chain triglycerides (MCTs), characterised by different carbon chain lengths, were gelled using beeswax (BW), candelilla wax (CLW) and carnauba wax (CRW). Critical concentrations, oil-binding capacity (OBC), textural parameters, thermal properties, microscopic properties and infrared spectra were used to evaluate their differences. The carbon chain length of oil sources showed different results for the critical concentration of the three wax-based gel oils at 25 °C, and the oleogel of MCT and CLW exhibited a minimum value (1%). The oleogels formed from CO and waxes with wax esters as the main components (BW and CRW) exhibit significantly lower OBC and textural value than the oleogels made from MCT with BW and CRW. Meanwhile, this is corroborated with the thermal behaviour and crystal morphology, and distribution of the oleogels. However, no differences in crystal types and generation of new functional groups were observed by X-ray diffraction and Fourier-transform infrared spectrometer, suggesting that the differences in the properties of wax-based oleogels with different carbon chain lengths are attributed to the interactions between the waxes and the oil sources (physical interaction). 相似文献
90.
Development of a spectroscopic method to determine the content of free radical scavenging compounds and oxidation products in thermally oxidised oils
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JuHee Song Eun Yeong Jang Mi‐Ja Kim Young‐Jun Kim JaeHwan Lee 《International Journal of Food Science & Technology》2016,51(11):2424-2432
A simple spectroscopic method using 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) was developed to simultaneously monitor the contents of free radical scavenging antioxidants (FRSs) and oxidised lipid products during oxidation through selection of proper solvents. Validation of the DPPH method was conducted in a stripped oil matrix, and practical applicability of the method was tested with heated oils. The absorbance of DPPH in isooctane simultaneously reflected the changing amounts of both FRSs and oxidised lipid products, whereas the absorbance in methanol mainly reflected changes in FRSs. Total polar materials (TPMs) were found to be representative of oxidised lipid products, which reacted with DPPH in isooctane better than in methanol. Validation parameters including accuracy, precision, linearity, limit of detection and limit of quantification were determined using α‐tocopherol as a model for FRSs and TPMs for oxidised lipid products. The DPPH protocol in isooctane and in methanol is useful for assessing the degree of oxidation in heated oils through comparing the contents of FRSs and oxidised lipids. 相似文献