全文获取类型
收费全文 | 1228篇 |
免费 | 5篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 6篇 |
综合类 | 5篇 |
化学工业 | 448篇 |
金属工艺 | 152篇 |
机械仪表 | 12篇 |
建筑科学 | 3篇 |
矿业工程 | 8篇 |
能源动力 | 253篇 |
轻工业 | 3篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
武器工业 | 1篇 |
无线电 | 34篇 |
一般工业技术 | 250篇 |
冶金工业 | 42篇 |
原子能技术 | 7篇 |
自动化技术 | 26篇 |
出版年
2023年 | 141篇 |
2022年 | 50篇 |
2021年 | 17篇 |
2020年 | 115篇 |
2019年 | 123篇 |
2018年 | 6篇 |
2017年 | 53篇 |
2016年 | 51篇 |
2015年 | 59篇 |
2014年 | 98篇 |
2013年 | 59篇 |
2012年 | 41篇 |
2011年 | 20篇 |
2010年 | 22篇 |
2009年 | 48篇 |
2008年 | 13篇 |
2007年 | 41篇 |
2006年 | 48篇 |
2005年 | 27篇 |
2004年 | 11篇 |
2003年 | 17篇 |
2002年 | 23篇 |
2001年 | 22篇 |
2000年 | 16篇 |
1999年 | 22篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 8篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有1253条查询结果,搜索用时 31 毫秒
41.
《材料与设计》2015
This study investigated the microstructure, phase transformation and mechanical property of Ni–Mn–Ga particles/Mg composites with a strong interfacial reaction between the particles and the matrix. The strong interfacial reaction was related to the large surface area and energy per unit volume of the flaky shape Ni–Mn–Ga particles that favors the reaction between the particles and matrix. The martensitic transformation behavior was largely weakened due to the interfacial reactions and thus the reduced volume fraction of Ni–Mn–Ga particles. The composites exhibited a much improved compressive strength and ductility in comparison with that of the Ni–Mn–Ga alloy. The compressive plasticity of the composites was decreased when the Ni–Mn–Ga particle content exceeded 40 wt%. In comparison with the Mg-composites with large size Ni–Mn–Ga particles, the composites with small size particles would have a much stronger interfacial reactions, which was detrimental to the phase transformation and mechanical ductility of the composites. The investigation results in this article could provide a reference for the design and preparation of the particles reinforced metal matrix functional composites. 相似文献
42.
《Ceramics International》2016,42(3):4517-4525
One-dimensional spindle-like BiVO4/TiO2 nanofibers heterojunction nanocomposites with high visible light photocatalytic activity have been successfully obtained by combining the electrospinning technique and solvothermal method. The as-obtained products were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis spectra and photoluminescence (PL) spectra. The results revealed that spindle-like BiVO4 nanostructures were successfully grown on TiO2 nanofibers. Photocatalytic tests showed that the BiVO4/TiO2 nanofibers heterojunction nanocomposites showed enhanced visible light photocatalytic activity than that of pure TiO2 nanofibers, which might be attributed to the effective photogenerated electrons-holes separation based on the photosynergistic effect of the BiVO4/TiO2 heterojunction. Moreover, the BiVO4/TiO2 nanofibers heterojunction nanocomposites could be easily recycled without any decrease of the photocatalytic activity. 相似文献
43.
《Ceramics International》2016,42(8):9851-9857
Because of their potential applications in gas sensing and catalysis, reduced graphene oxide (RGO) and ZnO have been the focus of much recent attention. However, few reported materials have been produced via the combination of hierarchical ZnO structures with RGO to achieve high sensing performances. In this paper, a hydrothermal method was used to synthesize hierarchical porous ZnO nanoflowers, which were then combined with graphene to enhance their sensing performances. The rapid detection of 1 ppm NO2 was achieved at 174 °C. The morphologies and structures of these materials were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Photoluminescence measurements and X-ray photoelectron spectroscopy were also used to investigate the mechanism of gas sensing by these materials. 相似文献
44.
《Journal of the European Ceramic Society》2022,42(6):2983-2993
In view of the practical application of γ-AlON as a promising transparent structural ceramic, in-depth insight into its mechanical and thermal properties is essential. The solid-state MAS NMR technique was combined with XRD Rietveld refinement to confirm the crystal structure of Al(8+x)/3O4-xNx (x = 0.299–0.575). These structural parameters were further applied to predict hardness and elastic properties based on theoretical exploration, which are in good agreement with the experimental values. A slight enhancement of mechanical properties with increasing nitrogen concentration is attributed to the stronger chemical bond in octahedra. The experimental thermal conductivity of γ-AlON transparent ceramics was improved slightly with the rise of x in the temperature range from 298 K to 1074 K. The intrinsic lattice thermal conductivity was determined by eliminating the extrinsic phonon scattering as well as the thermal radiation. The reason for the discrepancy between experimental and intrinsic thermal conductivity was revealed. The present methods provided powerful and accessible guidelines in optimizing the mechanical and thermal properties of oxynitride materials. 相似文献
45.
《Journal of the European Ceramic Society》2022,42(14):6435-6444
A chromium carbide (Cr-C) coating in-situ formed on the C/C substrate is successfully prepared by a novel reactive wetting strategy. The interfacial microstructure and oxidation resistance of coated C/C composites are investigated in detail. The as-prepared coating mainly consists of Cr23C6 and Cr7C3, forming a tight joining with the C/C substrate. Compared to uncoated samples, the oxidation weight loss of coated C/C composites is substantially reduced at high temperatures. Furthermore, the hardness of coated C/C composites is significantly increased, enhancing their ability to resist external damage. This reactive wetting strategy can also be used to prepare uniform coatings on C/C composites with complex grooved structure or large size. Surprisingly, coated C/C composites possess a low weight gain of 3.7% due to thin coating (< 10 µm), which can maintain their advantage of low density. 相似文献
46.
《Journal of the European Ceramic Society》2022,42(14):6391-6403
We propose a multi-physics numerical model for a self-healing ceramic matrix mini-composite under tensile load. Crack averaged PDEs are proposed for the transport of oxygen and of all the chemical species involved in the healing process and studied in the dimensionless form to perform the most appropriate discretization choices concerning time integration, and boundary conditions. Concerning the fibres’ degradation, a slow crack growth model explicitly dependent on the environmental parameters is calibrated using a particular exact solution and integrated numerically in the general case. The tow failure results from the statistical distribution of the fibres’ initial strength, the slow crack growth kinetics, and the load transfer following fibres breakage. The lifetime prediction capabilities of the model, as well as the effect of temperature, spatial variation of the statistical distribution of fibres strength, and applied load, are investigated highlighting the influence of the diffusion/reaction processes (healing) on the fibre breakage scenarios. 相似文献
47.
《Journal of the European Ceramic Society》2022,42(12):5023-5028
Lithium garnet oxides with 6.5 mol Li, such as Li6.5La3Zr1.5(Ta/Nb)0.5O12, typically crystallise in cubic structure and exhibit excellent room-temperature ionic conductivity close to 1 mS cm?1. However, it is challenging to densify garnet oxides. In this work, we investigated how the co-doping of tantalum (Ta) and niobium (Nb) affects the densification of pressureless sintered garnet electrolytes with compositions of Li6.5La3Zr1.5Ta(0.5?x)NbxO12, where x = 0–0.5. The highest densification (94.5% of relative density) was achieved in Li6.5La3Zr1.5Ta0.1Nb0.4O12 (TN-LLZO) when it was sintered at 1150 °C for 6 h. This TN-LLZO garnet electrolyte delivers an ionic conductivity of 1.04 × 10?3 S cm?1 (at 22 °C) with a low activation energy of 0.41 eV. Our findings demonstrate that the content of dopants (Ta and Nb) plays a critical role in enhancing the sintering performance of garnet ceramics at ambient pressure. 相似文献
48.
Dali Wang Zhaohua Jiang Bin Yang Shantao Zhang Mingfu Zhang Feifei Guo Wenwu Cao 《Journal of the American Ceramic Society》2014,97(10):3244-3251
Three composition groups in the BaTiO3–CaTiO3–BaHfO3 ternary system, (1 ? x)Ba(HfyTi1?y)O3–x(Ba1?zCaz)TiO3 (abbreviated as BHyT–xBCzT with x = 0–1.0, y = 0.16, z = 0.20; x = 0–1.0, y = 0.16, z = 0.30; x = 0–1.0, y = 0.20, z = 0.30, respectively), have been designed for investigating the variation of the intermediate O‐phase region and its effect on the electrical properties. The temperature‐composition phase diagram of each group has been proposed based on the X‐ray diffraction patterns and the temperature‐dependent dielectric behaviors. The enhanced piezoelectric properties are achieved in the O–T phase boundary compositions of the three groups, which are BH0.16T–0.58BC0.20T, BH0.16T–0.48BC0.30T and BH0.20T–0.53BC0.30T, respectively. Piezoelectric coefficient d33 of 448 pC/N is obtained in BH0.20T–0.53BC0.30T, which is higher than those of the other two phase boundary compositions. The O‐phase zone in BH0.20T–xBC0.30T is narrower than those in the BH0.16T–xBC0.20T and BH0.16T–xBC0.30T. In spite of its small O‐phase volume occupancy, the O‐phase plays a key role in the properties of the system. Our work confirms that the enhancement in piezoelectric properties is not only related to the O–T phase boundary near room temperature (RT), but also related to the shift of TR‐O toward RT. In addition, a quantitative relation between the phase boundary composition and atomic mole ratio of Hf to Ca (Rm) is proposed, which the Rm value corresponding to the phase boundary is about 0.58. The results clearly demonstrate that in this system high piezoelectric properties are achieved by tuning the specific Rm value. Such a work may provide new clues for designing lead‐free piezoelectric materials with enhanced piezoelectric property. 相似文献
49.
In this paper, we present the optimization of single-walled carbon nanotubes (SWCNTs) by acid-treatment, solution ultrasonication time and dispersion in photoactive layer for efficient organic solar cells. After non-covalently adhering with poly(3-hexylthiophene) (P3HT), pre-functionalized SWCNTs were blended into the composites of P3HT and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as photoactive layer, and a maximum power conversion efficiency (PCE) of 3.02% with a short-circuit current density of 11.46 mA/cm2 was obtained from photovoltaic cell indium-tin oxide (ITO)/poly(ethylene-dioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/P3HT:PCBM:SWCNTs/Al with an optimum 0.3 wt% SWCNTs in P3HT:PCBM:SWCNTs nanocomposite, the PCE can be enhanced by more than 10% as compared to the control device ITO/PEDOT:PSS/P3HT:PCBM/Al. The performance improvement by incorporating with functionalized SWCNTs is mainly attributed to the extension of excitons dissociation area and fastening charge carriers transfer across the active layer. 相似文献
50.
《Materials Research Bulletin》1987,22(4):439-445
The different phases observed during reduction of various Li/(1−n) Bi2O3, n PbO cells have been investigated using X Ray analysis and cyclic voltammetry. The results imply a pseudo single-phased behaviour. Comparisons between definite compounds and solid solutions occuring at the same compositions seem to indicate that the discharge kinetics is influenced by the degree of ordering of the ionic network. The existence of a large voltage plateau at 1,5 volt, the high energy density and the very good stability of the initial capacity during long time storage make Li, Bi Pb Oxyde cells specially suitable for watch supply applications. 相似文献