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51.
A type of fat bloom, which had not previously been fully characterized, was investigated to identify the state of its existence and its formation mechanism. Samples of bloom on solid chocolate resulting from the partial liquefaction of fat during temperature variations were analyzed to determine the crystal characteristics, fat contents, and triacylglycerol (TAG) compositions. Also, observation and elemental analyses were performed by scanning electron microscope with an energy-dispersive X-ray spectrometer, color analyses of minute regions were made by using PARISS®, and Fourier-transform infrared (FT-IR) analyses were performed. The dark- and light-brown areas did not show any differences in fat content or TAG compositions that could lead to the observed color differences. Although differences in component distributions were noted in micrometer-sized regions, no relation to the colors was confirmed. The bloom samples in this study and bloom developed without a tempering process resembled each other in the tone of color at their discolored regions, but the states they adopted differed from one another. It is suggested that the color in this type of bloom was affected by the roughness and/or porosity of the microstructure and could also be a result of the coarsened fat crystal network and of the liquid fat migration. 相似文献
52.
A. Neri M. S. Simonetti L. Cossignani P. Damiani 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1999,208(3):198-202
In a previous study the fatty acid compositions of triacylglycerol sub-fractions, separated by Ag+-HPLC, were studied in samples of cocoa butter, cocoa butter equivalents (CBE) and some of their mixtures. In this paper similar
research is described which was carried out on three other CBE (Illexao 30–61, Illexao 30–63, Illexao 30–71). The results
show the particular significance of the fully saturated sub-fraction, in which notable percentage changes in C16 : 0 and C18 : 0
contents were also detectable in the two mixtures with the lowest CBE content (5% or 15%, w/w) relative to genuine cocoa butter.
Multiple regression analysis was used to verify the percentages changes of fatty acid contents in the fully saturated sub-fraction
as a function of the percentage of CBE added to genuine cocoa butter.
Received: 19 December 1997 / Revised version: 25 June 1998 相似文献
53.
Stefan Bolliger Yuantong Zeng Erich J. Windhab 《Journal of the American Oil Chemists' Society》1999,76(6):659-667
In the present work cocoa butter and chocolate were precrystallized by means of a newly developed shear crystallizer. The
shear crystallizer was integrated into a circular loop. The handling of precrystallized cocoa butter showed a high dependency
on the timing of applied analysis. Differential scanning calorimetry, calorimetry, rheometry, and in-line near-infrared (NIR)
were all directly influenced by the fat crystal structure. Nevertheless, for cocoa butter it was shown that mechanical energy
input (rpm) had a significant influence on viscosity, melting enthalpy, and slope at the second point of inflection of a temper
curve. Experiments with cocoa butter at constant exit temperature showed a linear increase of viscosity between 0.1 and 0.8
Pa·s in the range of 300 to 1300 rpm. Melting enthalpy increased in the same rpm interval from 0.02 to 2.5 J/g. Solidification
time (from 4.5 to 0.5 min) and slope (from 0.82 to 0.15, second point of inflection of temper curve) consequently decreased
(both with exponential approximation). For cocoa butter, slope and solidification time correlated linearly whereas solidification
time and viscosity followed a power law fit. This proved that defined relationships exist between rheological data and data
from temper curve measurements. Viscosity was linearly dependent on crystal content. By means of NIR spectroscopy good correlation
models for cocoa butter viscosity, enthalpy (crystal content), and slope values were found. For precrystallized chocolate,
analytical values such as viscosity and slope values were detected off-line and used for calibration of NIR spectroscopy. 相似文献
54.
Xuebing Xu 《European Journal of Lipid Science and Technology》2000,102(4):287-303
Regiospecificity is one of the major advantages of using lipase technology for the modification of oils and fats to produce high‐value added products, such as cocoa butter equivalents, human milk fat substitutes, and other specific‐structured lipids. Due to the high cost of biocatalysts, the mainstream applications of lipases for normal oils and fats are still limited. Therefore, positional specificity of lipases has the priority and will be the target property to be exploited for commercial and industrial developments, because no chemical method has such a specificity and is promising or possible for this task. In this paper, encouraging products resulting from this regiospecificity are reviewed together with the critical evaluation of their reaction schemes, side reactions and by‐products, sources of substrate oils and acyl donors, and production processes. 相似文献
55.
Although fatty acid composition is the most important attribute used to control oxidation stability, all edible oils are affected by lipid oxidation irrespective of whether they are highly unsaturated or not. The aim of the study was to compare the oxidation of rapeseed oil (RO) and butter oil (BO) triacylglycerols (TAGs) and their mixtures containing 10% or 20% of the other. Oxidation of the TAGs at 40°C was followed by formation of primary and secondary products. Statistical methods were used to interpret the data. The RO and BO TAGs and their mixtures began to oxidise without any induction periods. In the RO TAGs more hydroperoxides and p‐anisidine reactive compounds were formed than in the BO TAGs. The BO TAGs oxidised more than would be expected by their fatty acid composition. High susceptibility of BO TAGs to oxidation was caused by the easy breakdown of their hydroperoxides. Heptadienal and heptenal were specific products of oxidised RO TAGs and heptanal and nonenal of oxidised BO TAGs. Mixtures of RO and BO TAGs behaved according to which was dominant in the mixture. However, as little as 10% of RO or BO TAG introduced its specific oxidation products to the mixture. © 1999 Society of Chemical Industry 相似文献
56.
57.
The enantiomeric composition of the monounsaturated triacylglycerols (TG) from cocoa butter was estimated. The monounsaturated
TG were separated into three fractions by reversed-phase high-performance liquid chromatography (HPLC), and each fraction
was subjected to the stereospecific analysis with chiral-phase HPLC. The results indicated that the major TG consisted of
equal amounts of 1-stearoyl-2-oleoyl-3-palmitoyl-sn-glycerol (SOP-sn-TG) and POS-sn-TG (47 mol%), 1,3-distearoyl-2-oleoyl-glycerol (SOS-TG) (33 mol%), and POP-TG (19 mol%). The contents of SOP-sn-TG and POS-sn-TG are 1.30 times that of the POP-TG content, and the SOS-TG content is 1.302 times that of the POP-TG content. The term “priority factor” is proposed for the ratio of the stearoyl group/palmitoyl group,
1:30 at thesn-1 andsn-3 or 1(3)-position. It shows a distinct specificity for particular fatty acids or their Coenzyme A esters in random esterification
at each position of the glycerol moiety in the biosynthesis of cocoa butter TG. 相似文献
58.
不同动物纤维的毡缩性能分析 总被引:2,自引:2,他引:0
应用毡缩球法研究了羊毛、马海毛、兔绒、山羊绒、绵羊绒和牦牛绒的毡缩性能.先测量出6种纤维的摩擦因数,然后采用毡缩球法分别测量6种纤维的毡缩性能,分析兔绒与羊毛混纺以及马海毛与羊毛混纺时混合比对纤维毡缩性能的影响.此外,还分析了羊毛和马海毛长度对纤维毡缩性能的影响.得出兔绒与羊毛混纺、马海毛与羊毛混纺时混纺比对混纺纤维毡缩性能的影响规律,以及纤维长度对其毡缩性能的影响规律. 相似文献
59.
60.
根据冲压机床振动缓冲特点,介绍一种具有缓冲吸振能力强,以小的变形承受大的载荷的碟形弹簧缓冲器,该缓冲器既有良好的吸振性能,又能大幅度降低设备自身的振幅。 相似文献