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101.
乙酰丙酮铜(Ⅱ)引发淀粉与甲基丙烯酸甲酯接枝共聚合的研究 总被引:5,自引:1,他引:5
<正> 淀粉与丙烯酸酯类单体的接枝共聚物有可能作为生物降解塑料,而被应用于农业、医药及食品等各个方面。因此寻求价廉、高效的引发剂,以用于引发淀粉与烯类单体的接枝共聚,已引起了人们的极大兴趣。 过渡金属离子与β二酮的配合物,如乙酰丙酮铁(Ⅲ)、乙酰丙酮锰(Ⅲ)、乙酰丙酮铜(Ⅱ)等是一类引起注目的新型引发剂,已在羊毛、蚕丝、纤维素等天然大分 相似文献
102.
High-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC–PAD) is a widely used technique to study the chain length distribution of amylopectin. The chromatograms, however, do not directly reflect this distribution, since the PAD response changes with the degree of polymerization. In this study, waxy maize starch was debranched and fractionated on a Bio-Gel P-6 column and the response factors for maltosaccharides with DP 3–65 were determined. The detector response per μg glucan chains was shown to decrease considerably for DP 3–7 while the curve leveled out for DP larger than 15. 相似文献
103.
Sangeeta Garg 《European Polymer Journal》2007,43(9):3976-3987
Corn starch was modified by cross-linking with epichlorohydrin and plasticizer glycerol. X-ray diffraction studies showed that relative crystallinity of the native and cross-linked starch were similar and were not affected by cross-linking. Different films were prepared by blending corn starch, cross-linked starch or glycerol modified starch in LDPE. The mechanical properties of the films were studied for tensile strength, elongation, melt flow index, and burst strength. The properties of the blend films were compared with LDPE films. It was observed that with the blending of 7.5% native starch, there was a decrease in tensile strength, elongation and melt flow index but burst strength increased. The tensile strength, elongation and melt flow index of the films containing cross-linked starch was considerably higher than those containing native starch but the burst strength showed a reverse trend. For native starch and cross-linked starch modified with glycerol, the elongation and melt flow index of the films increased but burst strength decreased. Surface scanning of the blend films were done by scanning electron microscope. Film containing cross-linked starch/glycerol modified starch in the blend was observed to be smoother than the native starch blend films. 相似文献
104.
The study addressed starch-based coatings on paper and fabrics. Coated materials and free starch films containing different
amounts of a well-established plasticizer (glycerol) or potential plasticizer (mainly polyols) were tested with respect to
water vapour permeance (WVPe), water vapour permeability (WVP), glass transition temperature (Tg), and mechanical strength (tensile tests). Both normal and high- amylose potato starch were used. These starches were modified
by (a) oxidation, (b) oxidation and hydroxypropylation or (c) oxidation and hydrophobically modified by reaction with octenyl-
or alkenyl-substituted succinic acid anhydride. Free films of hydroxypropylated high-amylose potato starch showed a lower
WVP than did the corresponding starches based on regular potato starch. The WVP of the hydrophobically modified regular potato
starches was substantially higher than that of films of the corresponding hydroxypropylated starches. The expected hydrophobic
effect of the succinic acid anhydrides in terms of a reduced WVP could not be observed. When glycerol was used as a plasticizer,
about 30 parts (by wt.) per hundred parts of starch were needed in order to reduce the Tg and to cause observable changes in the mechanical properties of the free films. 相似文献
105.
The effect of potassium and sodium cations on the adsorption of starch onto hematite and quartz was investigated. The role of these ions was analyzed in terms of their water structure-making or -breaking capabilities. In the presence of Na+, a structure maker, the polymer adsorption density did not change compared to the adsorption levels observed in distilled water. However, in the solutions of K+, a structure-breaking cation, the adsorption density of starch significantly increased. Assuming hydrogen bonding and chemical interaction to be the driving adsorption mechanism, it was proposed that the starch–oxide interactions can be envisioned as the competition between chemical interaction/hydrogen bonding and solvation energy:K+ reduces solvation energy by disturbing interfacial water structure and thus increases the free energy of adsorption, allowing the polymer to more closely approach the oxide surfaces. In contrast, Na+ which is indifferent to solvation energy does not interfere with the free energy of adsorption. 相似文献
106.
This paper reports a DSC study of the thermal decomposition of starch kept at constant moisture content (0-50%) in a sealed system comprising a high-pressure stainless steel pan with a gold-plated copper seal. The advantage of this technique is that it facilitates the detection and study of the processes of thermal decomposition of starch with constant moisture content, which is a common scenario in the processing of thermoplastic starches. It was found that the decomposition temperature decreased with increasing water content, and that the peak in decomposition temperature broadened, which is different to the case observed in open, unsealed systems. 相似文献
107.
Iuliana Spiridon 《Polymer Degradation and Stability》2008,93(10):1884-1890
A study of the enzymatic degradation of some montmorillonite-containing nanocomposites of poly(vinyl alcohol) with starch was based on the determinations of mass loss and the reducing sugars. The degraded residues have been examined by FT-IR spectroscopy and optical microscopy. It has been established that the nanoparticles hinder degradation, while the susceptibility to enzymatic degradation varies in the order: PVA/starch/nanocore > PVA/starch/Bentonite > PVA/starch/Peruvian clay. 相似文献
108.
109.
Atanu Biswas Sanghoon Kim Zhongqi He 《International Journal of Polymer Analysis and Characterization》2015,20(1):1-9
In this work, a microwave-assisted method was developed to prepare polyurethanes from starch or maltodextrin and tolylene-2,4-diisocyanate (TDI). As compared to conventional heating, this new synthetic procedure saves energy, significantly reduces reaction time, and yet entails product yields that are comparable to those of the conventional heating procedure. The reaction products were characterized with NMR, FT-IR, thermogravimetric analysis, and scanning electron microscopy. From these analyses, the polyurethanes made with the conventional and microwave methods are shown to be similar in chemical structure and physical morphology. Furthermore, the 1H and 13C NMR spectra of the starch polyurethanes have been fully assigned for the first time. 相似文献
110.
Hydrated starch alone and in composition with nanosilica A-300 and quercetin (natural antioxidant) was studied in the form of powders (mechanical mixture) and gels using 1H NMR (at 200-280 K), FTIR (293 K), TG (293-573 K), TSDC (90-265 K) and quantum chemistry methods. Influence of weakly polar (chloroform-d, CDCl3) and polar ((CD3)2SO, DMSO) deuterated solvents on bound water structure in these systems was also analysed at 200-280 K. The energetic and structural boundaries between weakly (unfrozen at 250-260 < T < 273 K) and strongly (unfrozen at 200 < T < 250-260 K) bound waters become nonabrupt after the addition of these solvents to quercetin/starch/nanosilica composites because of the differences in water interaction with these substances differently affecting its freezing point depression. 相似文献