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1.
Thermoplastic extrusion—the mechanism of the formation of extrudate structure and properties 总被引:6,自引:0,他引:6
Vladimir B. Tolstoguzov 《Journal of the American Oil Chemists' Society》1993,70(4):417-424
Systems processed by thermoplastic extrusion can be regarded as heterophase polymer melts of incompatible water-plasticized
biopolymers. In the process of thermoplastic extrusion, proteins and polysaccharides are melted at high pressure and temperature
below the temperature region of their thermal decomposition. Dispersed particles of these systems can be deformed in flow.
The mixed-melt anisotropic structure, formed in flow, is fixed by rapid conversion of the melt jet that lets the extruder
die from a viscous state to a rubber-like state and then to a glassy state caused by cooling and drying. Incompatibility of
proteins and polysaccharides in their water-plasticized melt mixtures impacts on structure formation and texturization during
thermoplastic extrusion.
Presented at the 20th ISF World Congress and 83rd AOCS Annual Meeting and Expo, May 10–14, 1992, Toronto, Ontario, Canada. 相似文献
2.
针对子学科具有物理目标的多目标协同优化问题, 研究基于NSGA-II 的求解策略. 鉴于子学科个体满足约束可行性的进化过程与系统级分配期望值无关, 提出具有良好的可行性和多样性的初始种群生成方法, 以提高多目标子学科的计算效率和计算精度. 为了解决由一致性目标函数与物理目标函数的作用不同而造成的NSGA-II 非支配级排序困难, 提出将子学科一致性目标函数转化为子学科自身约束的策略. 最后, 利用工程算例对所提出方法的有效性进行了验证.
相似文献3.
The intracellular endosymbiont Wolbachia pipientisis is well-known as one of the most common bacterial symbionts of arthropods. Recently, research has focused on the potential to utilize Wolbachia as a biocontrol agent of agricultural and medical pest insect species. Wolbachia blocks host infection from other pathogens and viruses in some species, however, it can also influence host life-history and reproductive traits. Therefore, in order to understand the biological impact and potential economic utility of Wolbachia, it is necessary to investigate the effects of Wolbachia infection on host traits. We compared life-history and reproductive traits between Wolbachia-infected and cured population in Mediterranean Flour Moth, Ephestia kuehniella. E. kuehniella is well known as a pest of stored products, and when infected with Wolbachia, it exhibits cytoplasmic incompatibility between uninfected females and infected males. We found that E. kuehniella suffers costs as a result of Wolbachia infection, through decreased larval survival and adult longevity, and prolonged developmental period. Moreover, reproductive performance was greater in the uninfected population, when excluding the effect of cytoplasmic incompatibility. Our results indicate that E. kuehniella suffers deleterious effects on both life-history and reproductive traits as a result of being infected with Wolbachia. We suggest such costs should be considered when evaluating the efficacy of utilizing Wolbachia in pest control. 相似文献
4.
The microstructure and elastic shear modulus of cold-set gels formed from high-sugar aqueous mixtures of gelatin (7 wt%) + oxidized starch (0-6 wt%) were investigated as a function of pH. Samples prepared at 90 °C, with citric acid added to adjust the pH, were rapidly quenched to ∼1 °C, subjected to a standard thermal treatment (40 °C for 10 min), and then investigated by confocal microscopy and small-deformation rheology at 24 °C. Under ‘natural’ conditions of pH ≈ 5.2 (no citric acid addition), the samples exhibited phase separation with a characteristic spinodal-type morphology. The spatial extent of the structural heterogeneity, expressed by a single length-scale parameter, was found to increase with starch concentration. Gradual acidification led to a reduction in this length-scale parameter, leading to complete inhibition of phase separation below a certain characteristic pH value in the range 4.5-4.9 (depending on starch content). Over the investigated pH range, the effect of starch addition was to reduce the storage modulus of the resulting gel. This reduction was more pronounced for the phase-separated samples. The pH of maximum rigidity was found to decrease from pHmax ≈ 4.6 for 0 wt% starch to pHmax ≈ 4.2 for 6 wt% starch. Taken all together, these observations can be understood in terms of the effects of pH on the cross-linking behaviour of the gelatin and the nature of the gelatin-starch electrostatic interactions. The microscopy results are consistent with a transition in behaviour from thermodynamic incompatibility (segregative interactions) at high pH to soluble complexation (associative interactions) at low pH. 相似文献
5.
6.
BACKGROUND: A slight change of polymer structure leads to a significantly different solubility parameter (SP), which is related to incompatibility and interface anchoring energy between a polymer and a liquid crystal (LC). RESULTS: Holographic gratings in polymer‐dispersed liquid crystals have been fabricated based on various urethane acrylate oligomer sizes and type of reactive diluent at two LC loadings. A large SP gap, using N‐vinylpyrrolidone as reactive diluent, gave much faster saturation of diffraction efficiency at higher level, but the grating failed to operate. On the contrary, films having a small SP gap, using 2‐ethylhexyl acrylate, operated under 20 V with a response time of about 10 ms, although their saturation of diffraction efficiency was relatively low. The results were interpreted in terms of morphology (determined using scanning electron microscopy), anchoring energy and resin elasticity. CONCLUSION: Low driving voltage and high diffraction efficiency are obtained by controlling the SP gap between LC and polymer. Copyright © 2007 Society of Chemical Industry 相似文献
7.
Harry L. Frisch 《Polymer International》1985,17(2):149-153
Interpenetrating polymer networks (IPNs) composed of two or more chemically distinct networks are not only intrinsically interesting as examples of macromolecular chemical topological isomerism but are in practice useful means of controlling mutual miscibility and phase morphology in crosslinked polymers. We will first review briefly the synthesis and properties of such IPN systems. This will be followed by an outline of a phenomenological theory of the phase stability and linearised theory of spinodal decomposition of binary, chemically quenched, low crosslink density IPNs recently developed by K. Binder and the author. Finally, we will discuss some aspects of the synthesis of ternary IPNs and the thermochromic properties of IPNs containing a crosslinked polydiacetylene. 相似文献
8.
D. Behera N. C. Mishra K. Patnaik 《Journal of Superconductivity and Novel Magnetism》1997,10(1):27-32
A series of samples of YBa2Cu3-xAgxO7-y with 0≤x≤0.12 composition was studied to probe into the Ag substitution effect on oxygen stoichiometry, lattice parameters,
and superconducting properties. With the samples prepared at a relatively lower sintering temperature, Ag could be doped in
the grains rather than precipitate at grain boundaries. Thus, unlike in the case of YBCO + Ag composites or in doped systems
annealed at high temperatures where Ag occupies mostly the grain boundary, the present system showed a drastic change inT
c, oxygen stoichiometry, and lattice parameters with Ag concentration, indicating the substitution of Ag at the Cu(l) sites
in the grains. The stable 2-fold oxygen coordination of Ag substituting Cu(l)’s explains the observed variation of oxygen
deficiency with Ag. A crystallochemical analysis has been made to reveal the crucial role of Ag-substitution-induced coordination
incompatibility and charge state instability on carrier concentration andT
c. 相似文献
9.
The necessity to associate two geometrically distinct meshes arises in many engineering applications. Current mesh‐association algorithms have generally been developed for piecewise‐linear geometry approximations, and their extension to the high‐order geometry representations corresponding to high‐order finite element methods is nontrivial. In the present work, we therefore propose a mesh‐association method for high‐order geometry representations. The associative map defines the image of a point on a mesh as its projection along a so‐called smoothed‐normal‐vector field onto the other mesh. The smoothed‐normal‐vector field is defined by the solution of a modified Helmholtz equation with right‐hand‐side data corresponding to the normal‐vector field. Classical regularity theory conveys that the smoothed‐normal‐vector field is continuously differentiable, which renders it well suited for a projection‐based association. Moreover, the regularity of the smoothed‐normal‐vector field increases with the regularity of the normal‐vector field and, hence, the smoothness of the association increases with the smoothness of the geometry representations. The proposed association method thus accommodates the higher regularity that can be provided by high‐order geometry representations. Several important properties of smoothed‐normal‐projection association are established by analysis and by numerical experiments on closed manifolds. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
10.
对采用不同材料修复的轴心受压钢筋砼柱进行了实验研究,并进行了ANSYS有限元模拟分析,研究了修复材料与柱本体砼的弹性模量比n.强度比α,修复时柱的卸载程度、修复区域相对深度等因素对修复后用筋砼柱力学性能的影响.认为修复材料与柱本体砼的弹性模量比n是导致钢筋砼柱力学性能不相容的最主要因素,它与强度比α共同决定修复柱的极限承载力. 相似文献