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61.
The synergistic influence of lanthanum and cobalt co-doping on room temperature ferromagnetism (RTFM) of TiO2 system is investigated. A series of Ti0.97?xCo0.03LaxO2 nanoparticles were prepared and their structures and properties were systematically studied with X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, UV–vis spectrophotometer, Raman spectra and magnetic measurement techniques, respectively. Detailed experimental characterizations indicate that the as-prepared La and Co co-doped samples exhibit single anatase phase, and all the samples exhibit strong visible photoluminescence associated with oxygen vacancies and a clear ferromagnetic hysteresis loop, both of which were dramatically enhanced with La and Co co-doping, and the maximum saturation magnetization (Ms) reaches 1.38 emu/g at the La content of 6 mol%. It is speculated that oxygen vacancies modulated by ionic La play an important role in the enhanced RTFM, which can be attributed to the bound magnetic polarons (BMPs) formed via ferromagnetic coupling between two neighboring Co2+ ions mediated by oxygen vacancy (F+ center). Our results present an alternative method to obtain high performance RTFM. 相似文献
62.
《Ceramics International》2017,43(3):3166-3170
Cu-doped ZnO was synthesized by hydrothermal method in a pulsed magnetic field. X-ray diffraction reveals the hexagonal wurtzite structure as with pure ZnO. The application of pulsed magnetic field increases the oxygen vacancy content and doping level of Cu2+ analyzed by Raman spectra and X-ray photoelectron spectroscopy. The origin of ferromagnetism is attributed to the oxygen vacancies induced Cu2+ ferromagnetic coupling. 相似文献
63.
Transition Metal Oxides: Electron‐Beam‐Induced Perovskite–Brownmillerite–Perovskite Structural Phase Transitions in Epitaxial La2/3Sr1/3MnO3 Films (Adv. Mater. 18/2014) 下载免费PDF全文
64.
Title of program: RANDOM VACANCY MIGRATION Catalog number: ACKO Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland (see application form in this issue) Computer: CDC 6600; Installation: University of Stuttgart Operating system: Scope 3.4 Programming language used: FORTRAN IV High speed storage required: 58 000 words No. of bits in a word: 60 Overlay structure: none No. of magnetic tapes required: none Other peripherals used: card reader, line printer No of cards in combined program and test deck: 718 Card punching code: BCD 相似文献
65.
A mathematical-physical model to describe the current response of p-type SrTiO3 ceramics in the low-temperature regime upon dc voltage step was developed, utilizing the numerical class library DIFFPACK (Numerical Objects, Norway). The current response in the time domain shows the experimentally observed Maxwell-Wagner relaxation (space charge polarization), followed by leakage current, and, eventually, resistance degradation. The relaxation behavior is analyzed by means of the simulation results for the spatial profiles of the electrical potential and the respective point defects. The impact of bias voltage and grain boundaries on the relaxation time is investigated. The simulation results are compared with experimental data. 相似文献
66.
Joan Daniel Prades Albert Cirera Joan Ramon Morante Albert Cornet 《Thin solid films》2007,515(24):8670-8673
The luminescence spectrum of ZnO exhibits, besides a UV band-edge recombination line, a broad visible band around 2.2-2.4 eV whose origin has not been satisfactorily established. Recently, analysis of the luminescence of nanostructured materials with high surface-to-volume ratios has led some authors to suggest that the band could be related to surface states. This work presents a novel ab initio study of the most relevant ZnO surfaces and their intrinsic point defects. It reveals the existence of intragap surface states 0.5 eV above the valence band maximum. If additional bulk defect levels are considered, several bulk-to-surface transitions are compatible with the observed visible luminescence. 相似文献
67.
冷轧变形纳米晶钴的X射线衍射研究 总被引:1,自引:0,他引:1
对冷轧变形前后纳米金属钴的微观应变。晶格常数以及晶粒尺寸的变化进行了研究,对X射线衍射图谱进行了分析计算,结果表明,变形过后晶体内部存有残余内应力并导致了微观应变,应变大小为ε=1.412×10q;对变形前后的晶格常数进行计算,得到变形后的晶格常数为a=0.25241nm;c=0.40782nm;透射电镜的观察和衍射谱线的计算表明变形后纳米金属钴的晶粒大小与形状基本未发生变化,平均晶粒尺寸为18.8nm。有可能是空位的活动降低了变形过程中的晶界迁移几率,使得变形后的晶粒尺寸基本没有发生变化。 相似文献
68.
Electrical conductivity measurements were made on the pyrochlore compounds (Gd1–xCax)2Sn2O7 (x =0, 0.0036, 0.0057, 0.03) as a function of temperature, oxygen partial pressure and Ca doping concentration. An effective Frenkel constant and oxygen vacancy mobility were derived. Intrinsic anion disorder was found to be lower than the expected value based on the relative radii of the cations in the A and B sites (A2B2O7). Low oxygen vacancy mobilities as well as low anion disorder resulted in considerably lower ionic conductivities in GdsSn2O7 relative to the previously studied Gd2(Ti1–xZrx)2O7 system. The temperature and composition dependence of the p-type electronic conductivity were evaluated and the oxidation enthalpy was derived. 相似文献
69.
70.