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排序方式: 共有226条查询结果,搜索用时 769 毫秒
111.
José A. Rodriguez Ping Liu Yoshiro Takahashi Kenichi Nakamura Francesc Viñes Francesc Illas 《Topics in Catalysis》2010,53(5-6):393-402
High-resolution photoemission and density functional (DF) calculations were used to study the interaction of atomic sulfur and S-containing molecules with metal carbides in which the carbon/metal ratio varies from 0.5 to 1 (M2C and MC, M = Ti, V or Mo). In these compounds, the C sites cannot be considered as simple spectators. They moderate the reactivity of the metal centers and provide bonding sites for adsorbates. For example, the adsorption of S on TiC(001) induces a large positive shift (1.0–1.3 eV) in the C 1s core level. DF calculations give a CTiTi hollow as the most stable site for the S adatoms. There is a correlation between the adsorption energy of S or thiophene and shifts in the centroid of the metal d band induced by metal–carbon bonding in the metal carbides. The M2C and MC carbides have difficulty obeying Sabatier’s principle for being good HDS catalysts because some of them interact too strongly with the products (M2C stoichiometry) and the others have problems dissociating the reactants (MC stoichiometry). The addition of small Au nanoparticles is an efficient way for enhancing the HDS activity of MC catalysts. In spite of the very poor desulfurization performance of TiC and MoC, the Au/TiC and Au/MoC systems display an HDS activity comparable or higher than that of conventional Ni/MoS x catalysts. The Au nanoparticles probably increase the HDS activity of the metal carbides by enhancing the adsorption energy of thiophene and by helping in the dissociation of H2 to produce the hydrogen necessary for the hydrogenolysis of C–S bonds and the removal of sulfur. 相似文献
112.
113.
Poly(acrylic acid) (PAA)/poly(vinyl alcohol) (PVA) membrane was prepared for the facilitated transport of CO2. The carrier of CO2 was monoprotonated ethylenediamine and was introduced in the membrane by ion exchange. The ion‐exchange capacity of the membrane was 4.5 meq/g, which was much higher than that of the Nafion 117 membrane. The membrane was highly swollen by the aqueous solution. Much higher selectivity of CO2 over N2 and higher CO2 permeability were obtained in the PAA/PVA membrane than in the Nafion membrane because of the higher ion‐exchange capacity and solvent content. The highest selectivity was more than 1900 when the CO2 partial pressure in the feed gas was 0.061 atm. Effects of ion‐exchange capacity, membrane thickness, and annealing temperature in conditions of membrane preparation on membrane performance were investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 936–942, 2001 相似文献
114.
Hirotaka Mutsuzaki Yoshiro Yokoyama Atsuo Ito Ayako Oyane 《International journal of molecular sciences》2013,14(9):19155-19168
A plasma- and precursor-assisted biomimetic process utilizing plasma and alternate dipping treatments was applied to a Leed-Keio artificial ligament to produce a thin coating of apatite in a supersaturated calcium phosphate solution. Following plasma surface modification, the specimen was alternately dipped in calcium and phosphate ion solutions three times (alternate dipping treatment) to create a precoating containing amorphous calcium phosphate (ACP) which is an apatite precursor. To grow an apatite layer on the ACP precoating, the ACP-precoated specimen was immersed for 24 h in a simulated body fluid with ion concentrations approximately equal to those in human blood plasma. The plasma surface modification was necessary to create an adequate apatite coating and to improve the coating adhesion depending on the plasma power density. The apatite coating prepared using the optimized conditions formed a thin-film that covered the entire surface of the artificial ligament. The resulting apatite-coated artificial ligament should exhibit improved osseointegration within the bone tunnel and possesses great potential for use in ligament reconstructions. 相似文献
115.
Seungchan Cho Keiko Kikuchi Takamichi Miyazaki Akira Kawasaki Yoshiro Arami Jean François Silvain 《Acta Materialia》2013,61(2):708-716
We have, for the first time, fabricated chromium (Cr) carbide nanostructures on multiwalled carbon nanotubes (MWCNTs) in a MWCNT–copper (Cu) composite by adding small amounts of Cr. A single nanocrystal of carbide was epitaxially grown on the sidewall of chemically treated MWCNTs through the diffusion of solute Cr atoms to defects in the MWCNTs. Carbide has an island-shaped morphology with a maximum size of several hundred nanometers. The phase of the generated Cr carbide nanostructures was mostly Cr7C3, as determined by electron beam diffraction using the nanobeam diffraction mode of a transmission electron microscope. In particular, the Cr carbide nanostructures formed at radially unzipped sites were connected to the outermost wall and some inner walls of the MWCNTs. This is expected to increase the load-bearing capacity of the MWNCTs because the inner walls contribute to the load transfer, which is very effective for improving the mechanical and thermomechanical properties of the composites. 相似文献
116.
Steffen Jockusch Nicholas J. Turro Yoshiro Mitsukami Makoto Matsumoto Taku Iwamura Torsten Lindner Andreas Flohr Giuseppe di Massimo 《应用聚合物科学杂志》2009,111(5):2163-2170
Superabsorbent polymer particles, consisting of partly neutralized, slightly crosslinked poly(acrylic acid), have been surface‐crosslinked photochemically. Surface crosslinking is required for many applications of superabsorbent polymers, such as disposable diapers, to control the flow and absorption of liquids in the gel bed. Photoinduced surface crosslinking has been achieved under UV irradiation (200–300 nm) with (NH4)2S2O8 as a photoactivated crosslinking agent. In comparison with the currently used thermal ester bridging method for surface crosslinking, the new photochemical method generates superabsorbent particles with superior properties, such as an improved flow of liquid through the gel bed, which utilizes the entire gel bed. These improved properties have been shown by water absorption capacity studies, fluid flow dynamics, environmental scanning electron microscopy, and low‐energy ion‐scattering studies. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
117.
Chang G Mori Y Mori S Irie T Nagai H Goto T Tatsu Y Imaishi H Morigaki K 《Analytical chemistry》2012,84(12):5292-5297
A microarray chip containing human P450 isoforms was constructed for the parallel assay of their metabolic activities. The chip had microwells that contained vertically integrated P450 and oxygen sensing layers. The oxygen sensing film was made of an organically modified silica film (ORMOSIL) doped with tris(4,7-diphenyl-1,10-phenanthroline) ruthenium dichloride (Ru(dpp)(3)Cl(2)). Human P450s (23 types) expressed in E. coli and purified as membrane fractions were immobilized in agarose matrixes on the oxygen sensing layer. The activities of P450s were determined by evaluating the fluorescence intensity enhancement of the oxygen sensor due to the oxygen consumption by the metabolic reaction. By normalizing the responses with the amounts of oxygen sensor and P450 enzymes in microwells, we could obtain fluorescence enhancement patterns that were characteristic to the combination of P450 isoforms and substrate material. The patterns obtained from two psoralen derivatives resembled each other, whereas a structurally different substrate (capsaicin) resulted in a distinct pattern. These results suggest the potential of the microarray to analyze the activities of diverse P450 isoforms in a high-throughput fashion. Furthermore, mechanism-based inactivation (MBI) of P450 could be detected by successively incubating a chip with different substrate solutions and measuring the residual activities. 相似文献
118.
Klaus Anhalt Yunfen Wang Yoshiro Yamada Jürgen Hartmann 《International Journal of Thermophysics》2008,29(3):969-983
Extending the application of metal (carbide)–carbon eutectic fixed-point cells to radiometry, e.g., for measurements in irradiance
mode, requires fixed-point cells with large apertures. In order to make large-aperture cells more readily usable in furnace
systems with smaller furnace tubes commonly used for small-aperture fixed-point cells, a novel cell design was developed.
For each of Cu, Pt–C, and Re–C fixed points, two types of fixed-point cells were manufactured, the small- and large-aperture
cell. For Pt–C and Re–C, the large-aperture cells were filled with a hyper-eutectic metal–carbon mixture; for the small cells,
a hypo-eutectic mixture was used for filling. For each material, the small and large cells were compared with respect to radiometric
differences. Whereas plateau shape and melting temperature are in good agreement for the small- and large-aperture Cu cells,
a larger difference was observed between small- and large-aperture cells of Pt–C and Re–C, respectively. The origin of these
observations, attributed to the temperature distribution inside the furnace, ingot contamination during manufacture, and non-uniform
ingot formation for the larger cells, is discussed. The comparison of measurements by a radiation thermometer and filter radiometer
of the Re–C and Pt–C large-aperture cells showed large differences that could be explained only by a strong radiance distribution
across the cavity bottom. Further investigations are envisaged to clarify the cause. 相似文献
119.
Masaki Narisawa Takashi Iseki Yoshiro Katase Kiyohito Okamura Kunio Oka Takaaki Dohmaru 《Journal of the American Ceramic Society》2003,86(2):227-233
The pyrolysis of polymethylsilane (PMS) in an argon gas environment with a flow rate of 1 L/min was investigated as a standard pyrolytic process, and the investigation showed SiSi network formation at 573 K. Subsequently, various condensed PMS resins were prepared by adjusting pre-heat-treatment or reflux conditions in the temperature range of 423–723 K. The effect of pre-heat treatment or refluxing on the ceramic yield at 1273 K was quantitatively evaluated. Structural evolution in the PMS resins prepared under various reflux conditions was investigated during pyrolysis up to 1873 K. The X-ray diffraction patterns of the pyrolysis products revealed crystallite growth of β-SiC and silicon at 1273–1473 K. 29 Si solid-state nuclear magnetic resonance with the single-pulse method was also conducted on the pyrolysis products at 1273 K. 相似文献
120.