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排序方式: 共有435条查询结果,搜索用时 843 毫秒
31.
Hydrocracking of diphenylmethane and tetralin over bifunctional NiW sulfide catalysts supported on three kinds of zeolites 总被引:1,自引:0,他引:1
Koichi Sato Yoshiki Iwata Toshikazu Yoneda Akio Nishijima Yasuo Miki Hiromichi Shimada 《Catalysis Today》1998,45(1-4):367-374
Hydrocracking reactions of diphenylmethane and tetralin were carried out over three kinds of zeolites with or without NiW sulfide to discuss the roles of catalytic bifunctionality in two types of hydrocracking reactions. It was found that strong acid sites were not needed for the hydrocracking of diphenylmethane, while the conversion of tetralin required relatively strong acid sites. Ultra-stable Y zeolite with strong acidity exhibited high hydrocracking activity for both reactions. In contrast, mordenite catalysts did not show high activity for either hydrocracking, though isomerization of tetralin and excess hydrocracking to gaseous products proceeded. The superior performances of ultra-stable Y zeolite in the tetralin hydrocracking were suggested to be related to the hydrogen transfer ability. In most cases, the loading of NiW sulfide enhanced catalytic activity. In the diphenylmethane hydrocracking, the role of NiW sulfide was found to supply active hydrogen to the hydrocracking active sites on zeolite and to prevent polymerization of benzyl cations. In the tetralin hydrocracking, the dehydrogenated products from tetralin were re-hydrogenated over NiW sulfide. 相似文献
32.
Hiromichi Yanagihara Wilhelm Brandstätter Nobumoto Ohashi Bernhard Gschaider Johannes Leixnering Igor Stankovic 《Topics in Catalysis》2009,52(13-20):1842-1846
Wall-flow channel models and soot deposition models based on micro scale considerations are integrated into global 3D diesel particulate filter simulations. In addition, transient and steady-state simulations are combined to understand at the same time short- and long-time behaviour of the diesel particulate filter (DPF). The functionality of the simulation tool is achieved and correlations with measured data encourage the use of the model as a tool to predict DPF behaviour. 相似文献
33.
A study was made of a centrifugal pressure nozzle with large orifice diameter (8-10 nun) for producing dry milk in capacity of 2-3 tons per hour to develop some performance data on spray distribution, drop size distribution, and capacity with changing spray drying conditions such as nozzle pressure, orifice diameter and spray angle. Experimental results were shown as follows. (1) A centrifugal pressure nozzle of large capacity such as 5,000- 5,500 l/hr at 150 kg/cm2 spray pressure and 110°s ray angle was designed by using the nozzle parameter Si/dedi√di/di. (2) Atomization characteristics were greatly affected by the ratio of orifice diameter (de) to the length (L) of the nozzle core. The smaller the ratio, around 0.125, the better are the atomizing effects. (3) The large orifice can be used at least 3,000 hr in the spray drying operation for milk without any wear in the orifice although it is only made of stainless steel. As a result, a spray dryer of large capacity for dry milk has been operated by a mono nozzle with a large orifice without any trouble for a long time 相似文献
34.
Hiromichi Fujii Victoria A. Yardley Takashi Matsuzaki Sadahiro Tsurekawa 《Journal of Materials Science》2008,43(11):3837-3847
The effect of a magnetic field on the nature of nanocrystallization from a melt-spun Fe73.5Si13.5B9Nb3Cu1 amorphous precursor has been studied with the aim of controlling microstructures and magnetic properties. Annealing for magnetic
crystallization was carried out at temperatures between the Curie temperature of the amorphous phase (586 K) and that of the
crystalline phase (920 K). It was found that the {110} texture component in crystallized α-Fe(Si) phase increased in importance
with increasing magnetic-field strength. An X-ray diffraction analysis based on the Shultz method revealed that the magnetic
field caused preferential formation of {110}-oriented nuclei. In addition, the applied field enhanced crystallization kinetics,
particularly the nucleation rate. No significant difference in grain growth behavior was observed as a result of applying
a magnetic field. We therefore conclude that the development of the {110} texture by magnetic crystallization is predominantly
attributable to preferential nucleation, rather than preferential growth, of {110}-oriented nuclei. The saturation magnetization
of nanocrystallized specimens, evaluated using a vibrating sample magnetometer (VSM), was increased by the application of
a magnetic field up to 4T during nanocrystallization. 相似文献
35.
36.
Potassium tantalate powders were hydrothermally synthesized at 400 °C using Ta2O5 and KOH as starting materials with various KOH concentrations (0.1–1.0 M) and heating durations (2–48 h). A defect pyrochlore
phase of KTa2O5(OH)·nH2O, was obtained at low KOH concentration and short reaction time. The perovskite phase of KTaO3 predominated as the heating duration and the KOH concentration increased. Pure KTaO3 was obtained in 0.5–1.0 M KOH aqueous solutions and reaction times of 8–48 h. Heteroepitaxitial KTaO3 thin films were achieved on the (100) SrTiO3 substrate in 0.5 M KOH solution under supercritical water conditions. Based on the XRD, SEM-EDX and EBSP (Electron BackScatter
Pattern) results, epitaxial KTaO3 crystals were grown on the (100) oriented single-crystal SrTiO3 substrate. Synthesis of perovskite KTaO3 crystals in supercritical water employed significantly low KOH concentrations (<0.5 M), which was far less than the very
high concentrations (>7 M) required for conventional hydrothermal method. 相似文献
37.
Hiroshi Inoue Koshi Sekizawa Koichi Eguchi Hiromichi Arai 《Journal of the American Ceramic Society》1997,80(3):584-588
A coating of barium hexaaluminate (Ba0.75 Al11.0 O17.25 ) on an α-SiC substrate and the thermal stability of the formed film were investigated for a high-temperature catalytic application. The film prepared by sol coating consisted of BaAl2 Si2 O8 and α-Al2 O3 phases and always contained many cracks or exfoliations after heating at 1200C. A hexaaluminate porous film was successfully formed by slurry coating without void formation at the interface between the film and the substrate and exfoliation due to the formation of the intermediate layer after heating at 1200°C. The microstructure of the film remained unchanged, even after heating at 1300°C. 相似文献
38.
Paola Ayala Hidetsugu Shiozawa Katrien De Blauwe Yasumitsu Miyata Rolf Follath Hiromichi Kataura Thomas Pichler 《Journal of Materials Science》2010,45(19):5318-5322
Carbon based structures have been widely studied by X-ray absorption (XAS), also called NEXAFS, which is a very useful bulk
probing method that allows examining the unoccupied density of states (DOS) and the site selective bonding environment. Two
very well known spectral features in the XAS core level spectrum are the σ* and π* bands, and both have been analyzed in several
studies for graphitic-like systems. However, among all the carbon materials, the unique one-dimensional electronic properties
attributed to single-walled carbon nanotubes (SWCNTs) exhibit features that reveal clearly their electronic structure in the
core level XAS spectrum. In this article, we outline the C1s response in XAS, which is related to the DOS of the conduction band in SWCNTs and its fine structure, revealed by experiments
performed on metallicity-sorted SWCNT material. The progress in the identification of changes in the site selective conduction
band electronic structure with XAS is discussed in detail. 相似文献
39.
Takao Morimura Masayuki Hasaka Kunikazu Shimoda Hiromichi Nakashima 《Journal of Electronic Materials》2010,39(9):2149-2153
The thermoelectric half-Heusler compounds Ti
x
NiSn0.998Sb0.002 (x = 1.0 to 1.2) and Ti
y
Zr0.25Hf0.25NiSn0.998Sb0.002 (y = 0.5 to 0.65) with nonstoichiometric nominal compositions were prepared by spin-casting and subsequent annealing at 1073 K
for 24 h. The dimensionless figure of merit ZT at room temperature was maximized at x = 1.1 and y = 0.6 in Ti-rich compounds through an increase in absolute Seebeck coefficients despite a decrease in electrical conductivities.
ZT reached 0.07 at x = 1.1 and 0.14 at y = 0.6. In powder x-ray diffraction analysis, minor phases of β-Sn, TiNi, Ti2Sn, and Ti5Sn3 were observed in addition to a major phase of half-Heusler. The quantity of the minor phases was minimized at x = 1.1 and y = 0.55, where the absolute Seebeck coefficients are maximized. In transmission electron microscopic (TEM) analysis of Ti0.55Zr0.25Hf0.25NiSn0.998Sb0.002, crystal grains of the half-Heusler phase, from several hundred nanometers to several micrometers in size, were observed.
TEM energy-dispersive spectroscopy measurements indicated that fluctuations of Ti, Zr, and Hf compositions within the Ti-site
in the half-Heusler phase may occur. Thermoelectric properties were improved at x = 1.1 and y = 0.6 rather than at the stoichiometric compositions of x = 1.0 and y = 0.5 due to minimization of the precipitate quantities. 相似文献
40.
ABSTRACT Superheated steam drying of sintered spheres of glass beads with different diameters is investigated to reveal the effects of the gravitational force on drying rates. In a previous study, the drying rate curves of small samples with coarse glass beads in which the frictional resistance to flow of water and the effect of the gravitational force are negligible, were predicted by an evaporation zone model.In the present investigation, the drying rate curves of sintered spheres of glass beads with diameters ranging from 1.53×10-2m to 4.99×lO-2m are experimentally and theoretically obtained, and also the capillary pressure curves are measured by use of Haines' apparatus. The drying rate curves of large samples in which the effect of the gravitational force can not be negligible, are compared with those for small samples and the difference among these curves is discussed in terms of the moisture distributions which are estimated from the evaporation zone model with the observed capillary pressure curves. 相似文献