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81.
SiO2·Bi2O3对NiZn铁氧体的烧结和磁性能的影响 总被引:2,自引:0,他引:2
本文采用溶胶-凝胶法制备NiZn铁氧体-SiO2·Bi2O3复合材料。结果表明:烧结过程中Bi2O3与SiO2形成非晶态玻璃相促进烧结,使瓷体烧结温度降至1030℃,并且瓷体的磁导率随非磁性玻璃相的增加显著减少。磁导率的变化主要是由于非磁性相的引入导致磁路隔断、退磁场增加以及铁氧体晶粒减小所致。加入适量非磁性相有助于改善瓷体的高频特性。 相似文献
82.
为提高石蜡相变乳液的传热性能,通过添加氧化石墨烯(GO),制备了GO/石蜡复合相变乳液并对其相关性能进行了表征。搭建了流动阻力、对流换热试验台,对比研究了石蜡相变乳液及GO/石蜡复合相变乳液的流动阻力特性和对流换热特性,试验结果表明,由于GO的亲水性,复合相变乳液都表现出较好的稳定性。当GO的质量分数为0.01%、0.02%、0.03%时,复合相变乳液的热导率分别增加了20.01%、30.50%、35.18%。添加GO使乳液的流动阻力略有增加,直管段最大增加了6.70%,90°弯管处最大增加了13.20%;对流传热系数随着GO浓度的增加而增大,当GO浓度为0.03%时,对流传热系数最大提高了43.90%。 相似文献
83.
Fischer–Tropsch synthesis was carried out in slurry phase over uniformly dispersed Co–SiO2 catalysts prepared by the sol–gel method. When 0.01–1 wt.% of noble metals were added to the Co–SiO2 catalysts, a high and stable catalytic activity was obtained over 60 h of the reaction at 503 K and 1 MPa. The addition of noble metals increased the reducibility of surface Co on the catalysts, without changing the particle size of Co metal significantly. High dispersion of metallic Co species stabilized on SiO2 was responsible for stable activity. The uniform pore size of the catalysts was enlarged by varying the preparation conditions and by adding organic compounds such as N,N-dimethylformamide and formamide. Increased pore size resulted in decrease in CO conversion and selectivity for CO2, a byproduct, and an increase in the olefin/paraffin ratio of the products. By modifying the surface of wide pore silica with Co–SiO2 prepared by the sol–gel method, a bimodal pore structured catalyst was prepared. The bimodal catalyst showed high catalytic performance with reducing the amount of the expensive sol–gel Co–SiO2. 相似文献
84.
B. Stypuła J. Banaś M. Starowicz H. Krawiec A. Bernasik A. Janas 《Journal of Applied Electrochemistry》2006,36(12):1407-1414
The anodic behaviour of copper was investigated in ethanol solution containing LiClO4, LiCl electrolyte and water. The type of electrolyte and the water content influences the mechanism of the anodic process and the formation of anodic products. In LiClO4 electrolyte the dissolution of copper is related to the oxidation of Cu(I) to Cu(II). In solutions of LiCl the etching of copper begins with the creation of soluble complexes of Cu(I) with chloride ions and solvent molecules. At potentials above 0.4 V the formation of alkoxides was observed in both solutions, characterized by a yellow tint. On the other hand, above 0.8 V (i.e. above the equilibrium potential of alcohol oxidation) copper dissolution is accompanied by the formation of a blue colloidal suspension of Cu (II) copper salt. Anodic etching of copper in solutions containing 3% H2O at potentials higher than 0.4 V leads to the formation of colloidal suspension of copper oxide nanoparticles. 相似文献
85.
利用导电高分子聚(3,4-二氧乙基噻吩)/聚(对苯乙烯磺酸)(PEDOT/PSS)作保护剂,制备了银纳米颗粒,用UV-Vis和TEM对其进行了表征.结果表明,选择合适量的PEDOT/PSS保护剂可以得到大小分布较窄银纳米颗粒. 相似文献
86.
The cobalt(II) chloride-catalyzed oxidative cleavage of -methylstyrene with oxygen in t-BuOH gives acetophenone and formaldehyde in good yield. The competing reactions between C=C cleavage and formation of polymeric products are strongly affected by the solvent, cobalt catalyst and concentration used, as well as the reaction temperature. A free radical mechanism involving a cyclic peroxide intermediate is proposed to give the cleavage products. Oxidation of various alkenes using CoCl2/t-BuOH/O2 system shows that only activated styrenes can be oxidized effectively. The reactivity of various styrenes and their selectivity towards giving cleavage products or polymers are strongly influenced by the electronic and steric properties of the substrate. 相似文献
87.
Hua Song Lingzhi Zhang Rick B. Watson Drew Braden Umit S. Ozkan 《Catalysis Today》2007,129(3-4):346-354
The catalytic performance of cobalt catalysts supported on γ-Al2O3, TiO2, ZrO2 were studied for bio-ethanol steam reforming (BESR) reaction. The supported catalysts (10 wt%Co) were prepared by impregnation and characterized through Thermogravimetric analysis (TGA), H2 chemisorption, laser Raman Spectroscopy, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), and temperature-programmed reaction (TPRxn). The metallic cobalt sites were found to correlate with the BESR reaction activity. The reaction and H2 chemisorption showed that ZrO2 supported catalyst showed the best dispersion and best catalytic activity. Over the 10% Co/ZrO2 catalyst, using a H2O:EtOH:inert molar ratio of 10:1:75 and a GHSV = 5000 h−1, 100% ethanol conversion and a yield of 5.5 mol H2/mol EtOH were obtained at 550 °C and atmospheric pressure. 相似文献
88.
89.
A. Goifman J. Gun V. Gitis A. Kamyshny Jr. O. Lev J. Donner H. Brnick E. Worch 《Applied catalysis. B, Environmental》2004,54(4):225-235
Pyrolysed carbon supported cobalt porphyrin, an electrocatalyst that is frequently used for oxygen reduction in fuel cells, is evaluated for catalytic oxidation of hydrogen sulfide by dissolved dioxygen. The catalyst performs best after heat treatment at 880 °C, at pH 8. Analysis of the reaction products reveals that sulfur is the dominant product throughout the investigated pH range 5–10. The catalyst performs much better than powdered activated carbon, granular activated carbon and different other forms of unmodified carbon catalysts. This is as far as we know the first time that heat treated cobalt porphyrins are evaluated for non-electrocatalytic applications. 相似文献
90.
Preparation of methanol oxidation electrocatalysts: ruthenium deposition on carbon-supported platinum nanoparticles 总被引:3,自引:0,他引:3
Methanol oxidation electrocatalysts were prepared from Ru electrochemical or spontaneous deposition on commercial-grade carbon-supported Pt nanoparticles (Pt-Vulcan XC72, E-TEK). The resulting Ru coverage was estimated by cyclic voltammetry in supporting electrolyte. The maximum electrocatalytic activity for methanol oxidation at room temperature was observed at lower Ru coverage for spontaneous deposition than for electrodeposition;
Ru 10% vs 20%, respectively. On the other hand, higher current densities for methanol oxidation were obtained in the case of electrodeposited Ru. These two results were related to the presence of non-reducible ruthenium oxides in the spontaneous deposit. The present work provides evidence that (i) efficient DMFC electrocatalysts can be achieved by Ru deposition on Pt nanoparticles, and (ii) formation of a PtRu alloy is not a required condition for effective methanol electrooxidation. 相似文献