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121.
Laegu Kang Byoung Hun Lee Wen-Jie Qi Yongjoo Jeon Nieh R. Gopalan S. Onishi K. Lee J.C. 《Electron Device Letters, IEEE》2000,21(4):181-183
Electrical and reliability properties of ultrathin HfO2 have been investigated. Pt electroded MOS capacitors with HfO2 gate dielectric (physical thickness ~45-135 Å and equivalent oxide thickness ~13.5-25 Å) were fabricated. HfO2 was deposited using reactive sputtering of a Hf target with O2 modulation technique. The leakage current of the 45 Å HfO2 sample was about 1×10-4 A/cm 2 at +1.0 V with a breakdown field ~8.5 MV/cm. Hysteresis was <100 mV after 500°C annealing in N2 ambient and there was no significant frequency dispersion of capacitance (<1%/dec.). It was also found that HfO2 exhibits negligible charge trapping and excellent TDDB characteristics with more than ten years lifetime even at VDD=2.0 V 相似文献
122.
E Fu S Nieh CT Hsiao YD Hsieh UM Wikesj? EC Shen 《Canadian Metallurgical Quarterly》1998,69(7):765-771
The first case report of gingival overgrowth induced by nifedipine (NIF), a calcium-beta blocker, was in 1984. However, the association between gingival alterations and the drug therapy of sodium diphenyl hydantoinate was initially described in 1939. The purpose of the experimental study was to examine the effect of NIF on gingival morphology in an animal model. Forty-five male Sprague-Dawley rats were randomly divided into 3 groups. Animals in each group daily received NIF in dimethyl sulfoxide by gastric feeding at a dosage of 0 (control), 30, or 50 mg/kg body weight for 9 weeks. Gingival gross morphology was assessed tri-weekly from stone models obtained from the mandibular incisal region. Animals were sacrificed at the end of study and tissue blocks were processed for histopathologic and histometric evaluation. Histometric analysis was performed at 5 selected tissue levels. Macro- and microscopic significantly increased gingival dimensions were demonstrated in NIF-treated animals compared to control. Although a fibrovascular tissue was observed in the tooth-gingiva interface for both NIF-treated and control animals, it was thicker and appeared earlier in NIF-treated animals. The results of the present study suggest that gingival overgrowth can be induced by NIF in rats and that the gingival overgrowth appears dose dependent. 相似文献
123.
Warm-temperature tensile ductility in Al−Mg alloys 总被引:1,自引:0,他引:1
Eric M. Taleff Gregory A. Henshall T. G. Nieh Donald R. Lesuer Jeffrey Wadsworth 《Metallurgical and Materials Transactions A》1998,29(13):1081-1091
Several binary and ternary Al alloys containing from 2.8 to 5.5 wt pct Mg were tested in tension at elevated temperatures
(200°C to 500°C) over a range of strain rates (10−4 to 2.0 s−1). Tensile ductilities of up to 325 pct were obtained in binary Al−Mg alloys with coarse grains deformed in the solute-drag
creep regime. Under test conditions in which solute-drag creep controls deformation, Mg in concentrations from 2.8 to 5.5
wt pct neither affects tensile ductility nor influences strain-rate sensitivity or flow stress significantly. Strength is
shown to increase with increasing Mg concentration, however, in the power-law-break down regime. The solute-drag creep process,
which leads to superplastic-like elongations, is shown to have no observable grain-size dependence in a binary Al−Mg material.
Ternary alloying additions of Mn and Zr are shown to decrease the strain-rate sensitivity during solute-drag creep, negatively
influencing ductility. An important cause of reduced ductility in the ternary alloys during creep deformation is found to
be a transition from necking-controlled failure in the binary alloys to cavitation-controlled failure in the ternary alloys
investigated. An increase in ternary element concentration, which can increase the relative volume percentage of proeutectic
products, increases cavitation. 相似文献
124.
T. G. Nieh Ph.D. C. M. McNally B.S. J. Wadsworth Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1989,41(9):31-35
Surprisingly, certain materials which are commonly seen as brittle may exhibit superplastic behavior under the proper conditions, and the ability to use superplastic forming methods on intermetallics and ceramics opens a realm of possibilities. By using unique processing techniques, superplasticity has been observed in such advanced materials as nickel silicides (Ni3Si), yttria-stabilized tetragonal zirconia (YTZ) and an Al2O3-reinforced YTZ composite (Al2O3/YTZ). 相似文献
125.
The character of plastic deformation in metallic glasses is investigated through instrumented nanoindentation experiments on amorphous Pd40Ni40P20 and Mg65Cu25Gd10. Using a customized experimental apparatus, nanoindentation experiments have been conducted over four decades of indentation strain rate and from ambient temperature up to the glass transition, allowing rapid evaluation of an extensive deformation map with only small volumes of experimental material. At low rates and temperatures, inhomogeneous or serrated flow is observed, owing to the discrete operation of individual shear bands. Two distinct regimes of homogeneous flow can be identified. The first, expected, regime of homogeneous flow corresponds to the onset of viscous deformation at high temperatures and low rates, and is well described by existing mechanistic models. The second homogeneous regime occurs at high deformation rates even well below the glass transition, and arises when deformation rates exceed the characteristic rate for shear band nucleation, kinetically forcing strain distribution. By extending an existing model for glass deformation to explore shear band nucleation kinetics, this second regime is quantitatively rationalized and the natural frequency for shear band nucleation is extracted from the data. From this analysis the critical radius of a shear band as it transitions from nucleation to propagation is estimated to be in the submicron range. 相似文献
126.