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991.
Abhimanyu Jayakumar Ashay Javadekar Jacob Gissinger John M. Vohs George W. Huber Raymond J. Gorte 《American Institute of Chemical Engineers》2013,59(9):3342-3348
The long‐term stability of direct carbon fuel cells, based on solid oxide fuel cells with molten Sb and Sb–Bi anodes, was examined for operation with activated charcoal, rice starch, and bio‐oil fuels at 973 K. With intermittent stirring of the fuel–metal anode interface, the anode performance was stable, and reasonable power densities (~250 mW/cm2) were achieved for periods up to 250 h. With Sc‐stabilized zirconia, severe thinning of the electrolyte occurred in regions of high current flow. No electrolyte thinning was observed with yttria‐stabilized zirconia as the electrolyte operating at the same current densities. © 2012 American Institute of Chemical Engineers AIChE J, 59: 3342–3348, 2013 相似文献
992.
P. Ulrich Biedermann Tien-Yau Luh David T.-C. Wengc Chi-Hong Kuo John J. Stezowski Israel Agranat 《Polycyclic Aromatic Compounds》2013,33(2-3):167-175
Abstract Overcrowded polycyclic aromatic enes (1), e.g., bi-9H-fluoren-9-ylidene (2) and bi-4H-cyclopenta[def]-phenanthren-4-ylidene (3) are potential starting materials for the preparation of bowl-shaped fragments of fullerenes. Semiempirical MNDO-PM3 calculations of C26 Hn and C30 Hn (n = 12,14,16) species 2–14 are used to analyze energetic and steric effects on the dehydrocyclization and isomerization reactions of these molecules. the out-of-plane bending and pyramidalization in these species are ascribed to intramolecular overcrowding in the fjord and cove regions and to strain introduced by C5 rings in the PAH skeleton. Oxidative photocyclization reactions on Z-2,2′-bridged derivatives of 2 and 3 are briefly outlined. 相似文献
993.
John Wawrowski 《化工设备与管道》2005,42(6):I0001-I0002
阀门选用不当,给工业界每年都造成了数百万美元的损失。不合适的阀门会导致阀门失灵,从而造成系统流体泄漏、产品偏离规格、停工检修费用、工作场所不安全以及对环境的危害。 相似文献
994.
995.
Garrett BC Dixon DA Camaioni DM Chipman DM Johnson MA Jonah CD Kimmel GA Miller JH Rescigno TN Rossky PJ Xantheas SS Colson SD Laufer AH Ray D Barbara PF Bartels DM Becker KH Bowen KH Bradforth SE Carmichael I Coe JV Corrales LR Cowin JP Dupuis M Eisenthal KB Franz JA Gutowski MS Jordan KD Kay BD Laverne JA Lymar SV Madey TE McCurdy CW Meisel D Mukamel S Nilsson AR Orlando TM Petrik NG Pimblott SM Rustad JR Schenter GK Singer SJ Tokmakoff A Wang LS Wettig C Zwier TS 《Chemical reviews》2005,105(1):355-390
996.
Polyethylene multiwalled carbon nanotube composites 总被引:4,自引:0,他引:4
Tony McNally Petra Pötschke Michael Murphy Steven E.J. Bell Daniel Bein John Paul Quinn 《Polymer》2005,46(19):8222-8232
Polyethylene (PE) multiwalled carbon nanotubes (MWCNTs) with weight fractions ranging from 0.1 to 10 wt% were prepared by melt blending using a mini-twin screw extruder. The morphology and degree of dispersion of the MWCNTs in the PE matrix at different length scales was investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and wide-angle X-ray diffraction (WAXD). Both individual and agglomerations of MWCNTs were evident. An up-shift of 17 cm−1 for the G band and the evolution of a shoulder to this peak were obtained in the Raman spectra of the nanocomposites, probably due to compressive forces exerted on the MWCNTs by PE chains and indicating intercalation of PE into the MWCNT bundles. The electrical conductivity and linear viscoelastic behaviour of these nanocomposites were investigated. A percolation threshold of about 7.5 wt% was obtained and the electrical conductivity of PE was increased significantly, by 16 orders of magnitude, from 10−20 to 10−4 S/cm. The storage modulus (G′) versus frequency curves approached a plateau above the percolation threshold with the formation of an interconnected nanotube structure, indicative of ‘pseudo-solid-like’ behaviour. The ultimate tensile strength and elongation at break of the nanocomposites decreased with addition of MWCNTs. The diminution of mechanical properties of the nanocomposites, though concomitant with a significant increase in electrical conductivity, implies the mechanism for mechanical reinforcement for PE/MWCNT composites is filler-matrix interfacial interactions and not filler percolation. The temperature of crystallisation (Tc) and fraction of PE that was crystalline (Fc) were modified by incorporating MWCNTs. The thermal decomposition temperature of PE was enhanced by 20 K on addition of 10 wt% MWCNT. 相似文献
997.
Polyimide-silica hybrid films were prepared from tetraethoxysilane (TEOS) and polyamic acid (PAA) via sol-gel process in the solution of N,N-dimethylacetamide (DMAc). The cryogenic mechanical and electrical properties of polyimide-silica hybrid films were studied taking into account the effects of silica content. The results indicated that the cryogenic modulus increased with the increase of silica content while the tensile strength and failure strain had a maximum value at proper silica contents. Moreover, the tensile strength and modulus of the hybrid films at cryogenic temperature (77 K) were obviously higher than those at room temperature, while the failure strain of the hybrid films was much lower at cryogenic temperature (77 K) than that at room temperature. The mean electrical breakdown strength of the hybrid films was shown to range from 151 to 225 kV/mm at cryogenic temperature (77 K). 相似文献
998.
999.
Xingsen Gao Zhaohui Zhou Junmin Xue John Wang 《Journal of the American Ceramic Society》2005,88(4):1037-1040
Effects of excess Bi2 O3 content on formation of (Bi3.15 Nd0.85 )Ti3 O12 (BNT) films deposited by RF sputtering were investigated. The microstructures and electrical properties of BNT thin films are strongly dependent on the excess Bi2 O3 content and post-sputtering annealing temperature, as examined by XRD, SEM, and P – E hysteresis loops. A small amount of excess bismuth improves the crystallinity and therefore polarization of BNT films, while too much excess bismuth leads to a reduction in polarization and an increase in coercive field. P – E loops of well-established squareness were observed for the BNT films derived from a moderate amount of Bi2 O3 excess (5 mol%), where a remanent polarization 2P r of 25.2 μC/cm2 and 2E c of 161.5 kV/cm were shown. A similar change in dielectric constant with increasing excess Bi2 O3 content was also observed, with the highest dielectric constant of 304.1 being measured for the BNT film derived from 5 mol% excess Bi2 O3 . 相似文献
1000.
The Mechanics of Indentation Induced Lateral Cracking 总被引:1,自引:0,他引:1
Xi Chen John W. Hutchinson Anthony G. Evans 《Journal of the American Ceramic Society》2005,88(5):1233-1238
The mechanics governing the lateral cracks that form when a hard object plastically penetrates a ceramic is presented. The roles of indentation load, penetration depth, and work of indentation are all highlighted, as are the influences of the mechanical properties of the material. A closed form solution for cracking induced by expansion of a two-dimensional cavity is used to bring out essential features related to parametric dependence and scaling. The three-dimensional axisymmetric problem for an annular crack driven by a rigid spherical or conical indenter is solved using numerical methods. The region of highest tensile stress is identified corresponding to the location where a crack is most likely to nucleate. This location coincides with the depth below the surface where the crack will expand parallel to the surface under mode I conditions. The solutions have been substantiated by comparison with measurements of the cracks that form upon Vickers indentation. The basic formula for the crack radius has been used to predict trends in cracking upon static penetration and impact by a projectile. In both cases, the extent of the cracking is substantially diminished by increasing the toughness of the material. The yield strength has a much smaller effect. The cracks caused by penetration and the volume removed per impact both decrease marginally at higher yield strength. 相似文献