全文获取类型
收费全文 | 3056篇 |
免费 | 59篇 |
国内免费 | 62篇 |
专业分类
电工技术 | 82篇 |
综合类 | 56篇 |
化学工业 | 698篇 |
金属工艺 | 480篇 |
机械仪表 | 68篇 |
建筑科学 | 35篇 |
矿业工程 | 115篇 |
能源动力 | 823篇 |
轻工业 | 17篇 |
水利工程 | 1篇 |
石油天然气 | 20篇 |
无线电 | 98篇 |
一般工业技术 | 471篇 |
冶金工业 | 174篇 |
原子能技术 | 18篇 |
自动化技术 | 21篇 |
出版年
2024年 | 5篇 |
2023年 | 56篇 |
2022年 | 86篇 |
2021年 | 101篇 |
2020年 | 97篇 |
2019年 | 133篇 |
2018年 | 93篇 |
2017年 | 113篇 |
2016年 | 43篇 |
2015年 | 44篇 |
2014年 | 156篇 |
2013年 | 183篇 |
2012年 | 118篇 |
2011年 | 279篇 |
2010年 | 157篇 |
2009年 | 217篇 |
2008年 | 216篇 |
2007年 | 168篇 |
2006年 | 131篇 |
2005年 | 77篇 |
2004年 | 76篇 |
2003年 | 102篇 |
2002年 | 66篇 |
2001年 | 51篇 |
2000年 | 52篇 |
1999年 | 66篇 |
1998年 | 61篇 |
1997年 | 57篇 |
1996年 | 36篇 |
1995年 | 36篇 |
1994年 | 20篇 |
1993年 | 21篇 |
1992年 | 20篇 |
1991年 | 12篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有3177条查询结果,搜索用时 0 毫秒
71.
金川镍闪速熔炼炉现状及前景展望 总被引:2,自引:0,他引:2
介绍了金川镍闪速熔炼炉的历史、现状及发展方向、尤其是金川镍闪速熔炼炉目前亟待解决的难题 相似文献
72.
The effect of water salinity on the reactions occurring during pressure acid leaching of an arid-region laterite ore, using hypersaline water, seawater, sub-potable water and tap water, is examined. Particular emphasis is placed on the mineralogy of the residue and its implications with regard to residue volume/mass, overall acid consumption and nickel extraction. Analysis of a pressure acid leach residue by electron microprobe indicates that the residual nickel is present in phases that contain silicon and varying concentrations of aluminium, but are deficient in sulphur. Incomplete extraction of nickel from the ore may not be attributed to any one mineral phase. 相似文献
73.
Microstructures and mechanical behavior of Inconel 718 fabricated by selective laser melting 总被引:3,自引:0,他引:3
K.N. Amato S.M. Gaytan L.E. Murr E. Martinez P.W. Shindo J. Hernandez S. CollinsF. Medina 《Acta Materialia》2012,60(5):2229-2239
In this study Inconel 718 cylinders were fabricated by selective laser melting in either argon or nitrogen gas from a pre-alloyed powder. As-fabricated cylinders oriented in the build direction (z-axis) and perpendicular to the build direction (x-axis) exhibited columnar grains and arrays of γ″ (body-centered tetragonal) Ni3Nb oblate ellipsoidal precipitates oriented in a strong [2 0 0] texture determined by combined optical metallography, transmission electron microscopy, and X-ray diffraction analysis. Fabricated and hot isostatic pressed (HIP) components exhibited a more pronounced [2 0 0] columnar γ″ phase precipitate architecture parallel to the laser beam or build direction (spaced at ∼0.8 μm), and a partially recrystallized fcc grain structure. Fabricated and annealed (1160 °C for 4 h) components were ∼50% recrystallized and the recrystallized regions contained spheroidal γ′ precipitates distributed in a dense field of fine γ″ precipitates. The γ″ precipitates were always observed to be coincident with {1 0 0} planes of the γ-fcc NiCr matrix. Some δ phase precipitates in the unrecrystallized/recrystallized interfaces and recrystallized grain boundaries were also observed in the annealed samples. The microindentation (Vickers) hardness was 3.9 GPa for the as-fabricated materials, 5.7 GPa for the HIP material, and 4.6 GPa for the annealed material. Corresponding tensile properties were comparable with wrought Inconel 718 alloy. 相似文献
74.
C. V. Subrahmanyam M. Venkateswara Rao D. N. Bhowmick 《European Journal of Lipid Science and Technology》2011,113(7):935-940
Ceramic membranes with pore size of 0.1 and 0.2 µm are used for the separation of nickel catalyst. Effect of trans‐membrane pressure (TMP), linear velocity, temperature and nickel content (solute) on flux and rejection has been investigated. The flux increased with increase in pore size of the membrane. The rejection characteristics were similar for 0.1 and 0.2 µm membranes. The nickel content and iodine value of the membrane‐filtered oil was comparable with that of conventional processes. Permeate flux increased with increase in temperature. Flux increased with increase in linear velocity and a marginal rise was observed above 2.09 m/s. The rejection characteristics were only slightly affected by higher linear velocity. The flux improved after back flushing. The average flux was higher with back flushing as compared to continuous (with out back flushing) filtration process. The results indicated that the secondary layer effect was more pronounced in microfiltration. The flux decreased with increase in solute concentration. The rejection characteristics were not affected by solute concentration. The rejection characteristic of the membranes remained unaltered after membranes were repeatedly cleaned with sodium hydroxide and HCl solutions, however, the flux was decreased marginally. 相似文献
75.
We have studied the effect of nickel oxide (NiO) on the sintering of yttria-stabilized zirconia (YSZ) at temperatures from 1100 to 1400 °C. Differences in the densification behaviour were observed between the direct use of NiO powders and Ni metal as precursor. Our results show that with the addition of Ni into YSZ, sintering was completed at 1300 °C instead of 1400 °C, a 100 °C reduction. The addition of Ni also increased the shrinkage rate at 1200 °C from −0.29×10−6 s−1 to −0.46×10−6 s−1. Young's modulus of the samples heat treated at 1200 °C measured by microindentation also increased from 26 GPa for YSZ to 65 or 191 GPa for YSZ plus NiO or Ni, respectively. Addition of NiO or Ni also stabilised the cubic phase and promoted grain growth in YSZ during sintering. 相似文献
76.
针对高镍奥氏体铸铁成本居高不下的特点,通过加入价格低廉的Mn代替部分昂贵的Ni,并调整Cu、Cr、Si等元素含量,制备低镍奥氏体铸铁,并进行磨粒磨损试验对比研究。结果表明:所制备的低镍铸铁可使基体达到几乎完全的奥氏体组织,且石墨形态和高镍铸铁相近;镍铸铁的力学性能及组织结构成分对材料的耐磨粒磨损性能均有影响,其中硬度和强度越高的镍铸铁,其磨损性能越好;所制备的低镍片状石墨铸铁的耐磨损性能均接近或高于高镍铸铁。 相似文献
77.
E. Sominski A. Gedanken N. Perkas H. P. Buchkremer N. H. Menzler L. Z. Zhang J. C. Yu 《Microporous and mesoporous materials》2003,60(1-3):91-97
A sonochemical process for the fabrication of the mesoporous composite NiO/yttria stabilized zirconia (YSZ) is described. Its surface area after the extraction of the surfactant is 193 m2/g for a sample containing 40 atom-% Ni. The main advantages of the sonochemical method, as compared with previous works, are the short reaction time (6 h) and that there is no requirement for the glycolation of the nickel, yttrium, and zirconium ions. The reduction of NiO/YSZ to the corresponding Ni/YSZ is also reported. 相似文献
78.
Synthesis of a magnetically removable visible-light photocatalyst based on nickel-doped zinc ferrite
《Ceramics International》2023,49(4):6006-6014
In this study, a facile method to synthesize magnetically removable visible-light photocatalysts based on nickel-doped zinc ferrites is presented. Ferrite semiconductor ceramics with the general formula Zn1-xNixFe2O4 (0 ≤ x ≤ 0.5, Δx = 0.1) were prepared by high-energy ball milling followed by annealing at 873 K. X-ray diffraction analysis confirmed the spinel single-phase Fd-3m without secondary phases for all compositions. The slight decrease in lattice parameters confirmed the presence of Ni2+ ions in the crystal structure because Ni had a smaller ionic radius than Zn. Raman spectroscopy demonstrated that Ni2+ ions were distributed on both tetrahedral and octahedral sites, which increased the inversion parameter and affected the photocatalytic efficiency and ferromagnetism. Magnetic hysteresis loops suggested an increase in the specific magnetization as the doping content increased, enabling magnetic recovery and reuse of the photocatalyst in water remediation. Diffuse reflectance spectroscopy showed a reduction in the band gap values with increasing nickel content, which was attributed to forming a sub-level in the band structure in the presence of Ni2+. Photocatalytic tests revealed a degradation efficiency higher than 60%, confirming that the doped samples obtained by high-energy ball milling were highly efficient and easily removable photocatalytic materials. 相似文献
79.
《Ceramics International》2023,49(8):12408-12414
In the present investigation, nickel oxide nanoparticles (NiO) were biosynthesized utilizing an extract of Clerodendrum phlomidis leaves. Their size, phase study, and shape were investigated using a variety of research methods. In addition, we assessed the photocatalytic effects of NiO nanoparticles on the degradation of methylene blue (MB) and acid blue (AB) dyes. Throughout the research process, we found that these nanoparticles had extraordinary potential for photocatalysis when exposed to UV light. This is a 100% environmentally friendly method that makes no use of any harmful or poisonous solvents. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and ultraviolet–visible spectroscopy (UV–Vis) were used to analyze the biosynthesized NiO nanoparticles. The catalytic activity of the newly synthesized nanoparticles was evaluated by seeing how well they degraded dyes called methylene (MB) and acid blue (AB). Following the first-order reaction, kinetics was the photocatalytic effectiveness against the methylene blue (MB) and acid blue (AB) dyes, both of which exhibited a maximum degradation efficiency of 92% and 63%. Because of this, the biosynthesized NiO nanoparticles synthesized utilizing the extract of Clerodendrum phlomidis leaves have the potential to be used in photocatalytic applications. 相似文献
80.
《Ceramics International》2023,49(20):33099-33110
In this study, spinel Ni0.5Zn0.5Fe2O4 doped with transition metal ions as well as rare-earth ions Ni0.4Zn0.4M′0.2Fe2O4 (M′ = Cu, Dy, Gd and Lu) and M″0.5Zn0.5Fe2O4 (M″ = Ni, Mn and Co) are developed using the sol-gel auto-combustion route, and the role of substitution on electromagnetic properties is investigated. The powder X-ray diffraction accompanied by Rietveld refinement signifies a single-phase spinel ferrite that belongs to Fd-3m space group for all the compositions. Rietveld refinement confirms that doped Cu2+, Dy3+, Gd3+ and Lu3+ ions are at random distribution between spinel tetrahedral and spinel octahedral sites against their preferential occupancy. The saturation magnetisation (MS) of Ni0.5Zn0.5Fe2O4 (MS = 50.5 emu/g) increased with partial doping showing MS = 60.08 emu/g for transition-metal doped Ni0.4Zn0.4Cu0.2Fe2O4 and MS = 109.7 emu/g for rare-earth doped Ni0.4Zn0.4Dy0.2Fe2O4, which was the highest among all the doped compositions. Doping enhances the dielectric permittivity of Ni0.5Zn0.5Fe2O4 from 4.2 to 6.5 for Ni0.4Zn0.4Cu0.2Fe2O4 and 7.7 for Ni0.4Zn0.4Dy0.2Fe2O4. Further, the reflection coefficient (RL) of all the doped compositions of Ni0.4Zn0.4M′0.2Fe2O4 (M′ = Cu, Dy, Gd and Lu) was less than −8 dB (85% absorption) throughout the frequency band of 8–12 GHz with an optimum material thickness of 3.5 mm. Transition metal ion doped Ni0.4Zn0.4Cu0.2Fe2O4 resulted in further improvement of its absorption characteristics of the incident EM waves with reflection coefficient (RL) less than −10 dB (between 84.15% and 90%) between 10 and 12 GHz at a material thickness of 3.5 mm in the X-band frequency range. 相似文献