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排序方式: 共有168条查询结果,搜索用时 12 毫秒
61.
An effective method is developed for low temperature metal oxide deposition through thermal decomposition of metal diketonates in supercritical carbon dioxide (scCO2) solvent. The rates of Al(acac)3 (Aluminum acetyl acetonate) and Ga(acac)3 (Gallium acetyl acetonate) thermal decomposition in scCO2 to form conformal Al2O3 and Ga2O3 thin films on planar surfaces were investigated. The thermal decomposition reaction of Al(acac)3 and Ga(acac)3 was found to be initialized at 150 °C and 160 °C respectively in scCO2 solvent, compared to 250 °C and 360 °C in analogous vacuum-based processes. By measuring the temperature dependence of the growth rates of metal oxide thin films, the apparent activation energy for the thermal decomposition of Al(acac)3 in scCO2 is found to be 68 ± 6 kJ/mol, in comparison with 80–100 kJ/mol observed for the corresponding vacuum-based thermal decomposition reaction. The enhanced thermal decomposition rate in scCO2 is ascribed to the high density solvent which effectively reduces the energy of the polar transition states in the reaction pathway. Preliminary results of thin film deposition of other metal oxides including ZrOx, FeOx, Co2O3, Cr2O3, HfOx from thermal decomposition of metal diketonates or fluorinated diketonates in scCO2 are also presented. 相似文献
62.
Two-dimensional model for twin-roll continuous casting 总被引:11,自引:0,他引:11
T. Saitoh H. Hojo H. Yaguchi C. G. Kang 《Metallurgical and Materials Transactions B》1989,20(3):381-390
A numerical algorithm for the two-dimensional solidification problem in the twin-roll continuous casting system is presented
in this paper. Attention is focused on the elucidation of heat transfer and flow characteristics in both the liquid and the
solid phases. The present mathematical model can be applied to general full Navier-Stokes and energy equations, thereby covering
the wide range of twin-roll casting conditions. The boundary fixing method (BFM) is adopted to handle the moving boundary,
and the resultant transformed governing equations for the solid and liquid regions are solved separately by using a usual
explicit-type finite difference method. In this paper, a general numerical methodology is presented, and the quantitative
relationships between the important control parameters in continuous casting of twin-roll type (such as the roll speed, the
roll gap, the initial temperature of molten materials, the material properties, the solidification profile, and the endpoint
of solidification) are clarified in detail. The present numerical results have been compared with experimental results obtained
separately to check the validity of the proposed method. 相似文献
63.
Realization of Large Electric Polarization and Strong Magnetoelectric Coupling in BiMn3Cr4O12 下载免费PDF全文
Long Zhou Jianhong Dai Yisheng Chai Huimin Zhang Shuai Dong Huibo Cao Stuart Calder Yunyu Yin Xiao Wang Xudong Shen Zhehong Liu Takashi Saito Yuichi Shimakawa Hajime Hojo Yuichi Ikuhara Masaki Azuma Zhiwei Hu Young Sun Changqing Jin Youwen Long 《Advanced materials (Deerfield Beach, Fla.)》2017,29(44)
Magnetoelectric multiferroics have received much attention in the past decade due to their interesting physics and promising multifunctional performance. For practical applications, simultaneous large ferroelectric polarization and strong magnetoelectric coupling are preferred. However, these two properties have not been found to be compatible in the single‐phase multiferroic materials discovered as yet. Here, it is shown that superior multiferroic properties exist in the A‐site ordered perovskite BiMn3Cr4O12 synthesized under high‐pressure and high‐temperature conditions. The compound experiences a ferroelectric phase transition ascribed to the 6s2 lone‐pair effects of Bi3+ at around 135 K, and a long‐range antiferromagnetic order related to the Cr3+ spins around 125 K, leading to the presence of a type‐I multiferroic phase with huge electric polarization. On further cooling to 48 K, a type‐II multiferroic phase induced by the special spin structure composed of both Mn‐ and Cr‐sublattices emerges, accompanied by considerable magnetoelectric coupling. BiMn3Cr4O12 thus provides a rare example of joint multiferroicity, where two different types of multiferroic phases develop subsequently so that both large polarization and significant magnetoelectric effect are achieved in a single‐phase multiferroic material. 相似文献
64.
Poly(vinyl alcohol) (PVAc) composite porous membrane has been prepared from PVAc latex film by extraction with acetone. The PVAc latex was prepared by emulsion polymerization of vinyl acetate in the presence of PVA, employing the hydrogen peroxide–tartaric acid systemm as an initiator. The extraction degree of PVAc could be controlled in a wide range by changing the addition method of the initiator, and, acoordingly, PVA–PVAc omposite porous membranes which had variosu void volumes were obtained. The maximum void volume attained was ca. 90%. Permation characteristics of organic solvents wre investigated on the membranes whose extraction degrees were 95.6% and 80.7%. Thge feeds were benzene, n-hexane, cyclohexane, and their mixtures. neither swelling nor shrinkage in tje appearance size of the while benzene hardly permeated even at 20 kg/cm2. The grafted PVAc in the mebrane was removed or converted into grafted PVA by treatment with sodium methylate, and then the depression of benzene permeation was lost. The grafted PVAc was suggested to be localizd on the cell wall and was found to function as a valve which closes with nenzene or a good solvent for PVAc and opens with n-haxane or a poor solvent for PVAc. 相似文献
65.
The kinetics of the ligand exchange reaction of the Cu(II)-ammine complex with poly(vinyl alcohol) (PVA) has been studied by a stopped-flow method at pH 9–10, at μ=0.1 (NH4Cl) and at 25°C. The reaction is initiated by the formation of unstable [Cu(NH3)3]2+ by the attack of H+ on Cu(II)-ammine complex, and proceeds through the mixed complex {[Cu(NH3)3(O?PVA)]2+}. This step may be rate-determining, followed by a rapid reaction. Finally, the Cu(II) ion is taken up by PVA. The rate is given by d[Cu(II)?PVA]/dt=k[H+]{[Cu(NH3)4]2+}[PVA]/[NH4Cl], where k=k1 + k′2[H+], k1=4.25× 10s?1 and k′2=5.20× 1011l mol?1s?1. 相似文献
66.
67.
SiC ceramics were prepared from nanosized β-SiC powder with different compositions of AlN and Y2O3 sintering additives by spark plasma sintering (SPS) at 1900 °C for 600 s in N2. The relative density of the sintered SiC specimens increased with increasing amount of AlN, reaching a relative density higher than 99%, while at the same time grain size decreased significantly. The smallest average grain size of 150 nm was observed for SiC sample sintered with 10 vol% of additives consisting of 90 mol% AlN and 10 mol% Y2O3. Fully dense nanostructured SiC ceramics with inhibited grain growth were obtained by the AlN additive and SPS technique. The flexural strength of the SiC body containing 70 mol% AlN and 30 mol% Y2O3 additives reached the maximum value of 1000 MPa. The SiC bodies prepared with AlN and Y2O3 additives had the fracture toughness of around 2.5 MPam1/2. 相似文献
68.
Interfacial fatigue crack growth behavior in GF/epoxy model composites was investigated using bifiber shear (BFS) specimens in a scanning electron microscope. The specimen is composed of two E-glass filaments with diameters of 23 and 40 μm, and bisphenol A type epoxy is impregnated between the filaments. The crack growth behavior under different stress ratios was investigated to clarify the fatigue crack growth mechanism. The change in the crack growth rate, da/dN, was not monotonic with crack length, suggesting a variation in the resistance to fatigue crack growth along a single filament. The resistance to fatigue crack growth of the interface is much smaller than that of composite laminates. The fatigue crack growth mechanism of the glass fiber/epoxy interface under different stress ratios is controlled by the maximum energy release rate, Gmax, which is completely different from that of composite laminates. 相似文献
69.
M Hojo M Hoshimaru S Miyamoto W Taki I Nagata M Asahi N Matsuura R Ishizaki H Kikuchi N Hashimoto 《Canadian Metallurgical Quarterly》1998,89(4):623-629
N-Nitroso propoxur (NP) can be synthesized from a widely used N-methylcarbamate insecticide, propoxur, in vitro in the laboratory. Because of the extensive use of aerosol propoxur, the adverse effect on cells of respiratory origin is worth elucidating. In this report, two mammalian cell cultures from respiratory tissues [a hamster lung fibroblast, V79, and a primary rat tracheal epithelial cell (RTE)], were used to investigate the genotoxicity of propoxur and NP. NP was more cytotoxic than propoxur, with LC50s (20 and six times smaller, respectively in V79 and RTE cells. NP significantly induced sister chromatid exchange (> or = 0.01 microg/ml), chromosome aberration (> or = 2.5 microg/ml) and hprt gene mutation (> or = 0.5 microg/ml) in V79 cells, and cell transformation (> or = 0.2 microg/ml) in RTE cells. Results of chromosome aberration and hprt gene mutation indicated that the major pre-mutagenic lesion induced by NP must be the O6-methylguanine adduct, which frequently mispairs with thymine and thus gives rise to a GC-->AT transition. Propoxur was not mutagenic to either type of cells. However, it inhibited gap-junctional intercellular communication in V79 cells, which indicates that propoxur could act through some epigenetic mechanisms, such as tumor promotion or cell proliferation, in the multiple process of chemical carcinogenesis. 相似文献
70.
Ee Taek Hwang Khizar Sheikh Katherine L. Orchard Daisuke Hojo Valentin Radu Chong‐Yong Lee Emma Ainsworth Colin Lockwood Manuela A. Gross Tadafumi Adschiri Erwin Reisner Julea N. Butt Lars J. C. Jeuken 《Advanced functional materials》2015,25(15):2308-2315
In nature, charge recombination in light‐harvesting reaction centers is minimized by efficient charge separation. Here, it is aimed to mimic this by coupling dye‐sensitized TiO2 nanocrystals to a decaheme protein, MtrC from Shewanella oneidensis MR‐1, where the 10 hemes of MtrC form a ≈7‐nm‐long molecular wire between the TiO2 and the underlying electrode. The system is assembled by forming a densely packed MtrC film on an ultra‐flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP). The step‐by‐step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz‐crystal microbalance with dissipation (QCM‐D), and atomic force microscopy (AFM). Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit. In other words, in these TiO2/MtrC hybrid photodiodes, MtrC traps the conduction‐band electrons from TiO2 before transferring them to the electrode, creating a photobioelectrochemical system in which a redox protein is used to mimic the efficient charge separation found in biological photosystems. 相似文献