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51.
A self‐flux method is the simplest technique for synthesizing Bi2Sr2CaCu2O8+δ (Bi‐2212) superconducting single crystals. However, the crystals are inevitably contaminated because of the Bi‐2212 stoichiometric melt reacting with the crucible material. In this paper, we investigate the nonsuperconducting subproduct that forms during heating in the self‐flux method for synthesizing Bi‐2212. This subproduct was identified as BiSr2CaAl3O9 by X‐ray diffraction. Bi‐2212 crystal growth was performed using A12O3 crucibles with three different purities (nominally 97, 99.7, and 99.9%). For both the 97 and 99.7% purity crucibles, the subproduct was observed in all five samples out of five, whereas for the 99.9% purity crucible, it was observed in only two samples out of five. Furthermore, the 99.9% purity crucible gave a much lower subproduct volume than the 97% purity crucible. The average superconducting critical temperature (Tc,zero) varied depending on the crucible purity; it was 89.6, 90.8, and 91.8 K for the 97, 99.7, and 99.9% purity crucibles, respectively. Finally, we fabricated Bi‐2212 stacked devices with intrinsic Josephson junctions (Bi‐2212 stack) using as‐grown crystals from the 97 and 99.9% purity crucibles. The Bi‐2212 stacks exhibited a highly hysteretic current–voltage characteristic even at liquid N2 temperature and they had identical quality parameters for Josephson junctions (i.e., Ir/Ic and voltage jump Vj). We conclude that the subproduct formation has little effect on the electrical characteristics of a Josephson junction device at 77 K. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.  相似文献   
52.
We examined the crystallization behavior of high-melting fractions in liquid oil containing high concentrations of diacylglycerols (DAG >80%) (hereafter referred to as DAG-rich oil). By differential scanning calorimetry and optical microscopy at moderate cooling rates, crystallization in the DAG-rich oil was detected at around 6 °C. It was found that the crystallization extent increased with decreasing temperatures of crystallization below 0 °C. A gas chromatographic analysis was performed on the crystallized fractions, which were separated by filtration at different periods of isothermal crystallization at 3 °C. The results indicated that at earlier crystallization periods, the concentrations of 1,3-disaturated DAG such as palmitic and stearic acid moieties (15 min) and 1,3-saturated–unsaturated mixed-acid DAG including oleic acid, palmitic, and stearic acid moieties (15 min–3 h) were predominant. However, the concentrations of 1,3-diunsaturated DAG including oleic acid moiety increased after a crystallization period of 6 h. To clarify the sequential crystallization process of DAG, we examined the binary mixing behavior of principal DAG components occurring in the rapeseed-based DAG-rich oil. It was evident that 1,3-disaturated DAG, 1,3-saturated–unsaturated mixed-acid DAG, and 1,3-diunsaturated DAG exhibited immiscible behavior. From these data, basic information on the precipitation processes in DAG-rich oils at chilled temperatures was obtained.  相似文献   
53.
传统圆孔翻边工艺中,翻边高度和形状精度是制约板料成形极限的主要因素。为了获得较为稳固的翻边凸起部位,提出采用镦粗一翻边复合工艺成形厚板翻边凸起结构。利用DEFORM有限元软件对镦粗一翻边复合工艺过程进行数值模拟,分析各工艺参数对翻边高度的影响规律;对A1050P-O厚板进行了镦粗一翻边工艺试验并讨论了翻边后的板料硬度分布规律。结果表明:与传统翻边工艺相比,镦粗一翻边工艺的翻边凸起部位精度更好、翻边高度更高,且有限元模拟结果与试验结果保持了较好的一致性。成形后的板料由于加工硬化影响,翻边凸起结构的硬度增大,有利于零件的后续加工组装工序。  相似文献   
54.
β‐Crystalline chitin was added to polylactic acid (PLA), and this PLA was then heat treated at 100 °C for 1 min. The crystallinity of the heat‐treated PLA increased to more than 40%, and its crystallization speed also increased significantly. Furthermore, the temperature dependence of the dielectric breakdown strength (EB) was checked, and it was found that at a temperature of 80 °C, the EB value of the PLA with chitin was around 1.8 times greater than that of the PLA without chitin. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.  相似文献   
55.
Oil‐in‐water (O/W) emulsions with varying concentration of oil phase, medium‐chain triglyceride (MCT), were prepared using phase‐separating gum arabic (GA)/sugar beet pectin (SBP) mixture as an emulsifier. Stability of the emulsions including emulsion phase separation, droplet size change, and oil migration were investigated by means of visual observation, droplet size analysis, oil partition analysis, backscattering of light, and interfacial tension measurement. It was found that in the emulsions prepared with 4.0% GA/1.0% SBP, when the concentration of MCT was greater than 2.0%, emulsion phase separation was not observed and the emulsions were stable with droplet size unchanged during storage. This result proves the emulsification ability of phase‐separating biopolymer mixtures and their potential usage as emulsifiers to prepare O/W emulsion. However, when the concentration of MCT was equal or less than 2.0%, emulsion phase separation occurred after preparation resulting in an upper SBP‐rich phase and a lower GA‐rich phase. The droplet size increased in the upper phase whereas decreased slightly in the lower phase with time, compared to the freshly prepared emulsions. During storage, the oil droplets exhibited a complex migration process: first moving to the SBP‐rich phase, then to the GA‐rich phase and finally gathering at the interface between the two phases. The mechanisms of the emulsion stability and oil migration in the phase‐separated emulsions were discussed.  相似文献   
56.
The wetting behavior of molten pure Mg droplets on pure Ti substrate, a crucial phenomenon in the design of Mg matrix composites reinforced with Ti particles, was investigated by the sessile drop method. The contact angle was measured in high-purity argon (99.999%) at 1073 K. In particular, the effects of two important parameters on the contact angle were evaluated: Mg evaporation during the wetting test; and surface oxide film of the substrate. The calculation method to estimate the modified contact angle involved taking the morphological changes of the droplet outline due to the evaporation into consideration. By changing the thickness of the surface oxide films on the Ti substrate, it was possible to examine the wettability and the chemical reactions at the interface between the solidified Mg drop and the substrate were investigated by scanning electron microscopy–energy dispersive X-ray spectrometry analysis. At the initial wetting stage, a large contact angle with 95–110° was obtained, which depended on the reduction of TiO2 surface films by Mg droplets. When the molten Mg contacts an area of pure Ti after reduction, the contact angle suddenly decreased. The equilibrium value at the stable state strongly depended on the surface roughness of the Ti plate.  相似文献   
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59.
Highly controlled InGaAs/InP MQW interfaces have been realized over two inch wafers by employing tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP) in place of AsH3 and PH3. This was accomplished by reducing arsenic contamination in the InP layer after InGaAs growth and an As-P exchange reaction at the interfaces.  相似文献   
60.
Simultaneous interpenetrating polymer networks (SINs) were prepared from nadic methyl anhydride-cured epoxy resin and bismaleimide (BMI) of which the composition ratios were, respectively, comprised of 3/1 (EM-25 series) and 1/1 (EM-50 series), under different gelling conditions for both resins. Dynamic mechanical and tensile properties were measured for these SINs. Turbidity was also measured to obtain some information regarding morphology. Although the rubbery modulus was constant irrespective of a gel-time ratio (Gt) of the epoxide resin to that of BMI for the EM-25 series, it increased with increasing Gt for the EM-50 series. The glass transition temperature (Tg) was nearly constant at Gt < 1 and then decreased with increasing Gt at Gt > 1 for the EM-25 series. On the other hand, Tg was nearly constant irrespective of Gt for the EM-50 series, though the values of Tg at Gt < 1 were somewhat higher than those at Gt > 1. There was an appropriate value of Gt that gave better tensile strength (σb) or toughness evaluated by the area under a stress-strain curve. The Tg and σb were found to be correlated to the turbidity of the SINs. The above mechanical behavior can be explained in terms of the molecular mixing and morphology that vary with a change in the relative polymerization rate of both the resins. © 1993 John Wiley & Sons, Inc.  相似文献   
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