全文获取类型
收费全文 | 2238篇 |
免费 | 61篇 |
国内免费 | 38篇 |
专业分类
电工技术 | 20篇 |
综合类 | 82篇 |
化学工业 | 736篇 |
金属工艺 | 135篇 |
机械仪表 | 154篇 |
建筑科学 | 47篇 |
矿业工程 | 43篇 |
能源动力 | 167篇 |
轻工业 | 165篇 |
石油天然气 | 4篇 |
武器工业 | 3篇 |
无线电 | 37篇 |
一般工业技术 | 644篇 |
冶金工业 | 44篇 |
原子能技术 | 42篇 |
自动化技术 | 14篇 |
出版年
2023年 | 16篇 |
2022年 | 36篇 |
2021年 | 44篇 |
2020年 | 44篇 |
2019年 | 54篇 |
2018年 | 45篇 |
2017年 | 51篇 |
2016年 | 67篇 |
2015年 | 79篇 |
2014年 | 82篇 |
2013年 | 167篇 |
2012年 | 100篇 |
2011年 | 146篇 |
2010年 | 123篇 |
2009年 | 105篇 |
2008年 | 102篇 |
2007年 | 110篇 |
2006年 | 125篇 |
2005年 | 115篇 |
2004年 | 85篇 |
2003年 | 88篇 |
2002年 | 84篇 |
2001年 | 38篇 |
2000年 | 50篇 |
1999年 | 66篇 |
1998年 | 52篇 |
1997年 | 34篇 |
1996年 | 34篇 |
1995年 | 27篇 |
1994年 | 32篇 |
1993年 | 29篇 |
1992年 | 27篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有2337条查询结果,搜索用时 15 毫秒
1.
D. Sciti L. Zoli A. Vinci L. Silvestroni S. Mungiguerra P. Galizia 《Journal of the European Ceramic Society》2021,41(5):3045-3050
In this paper the microstructure and mechanical properties of two different Cf/ZrB2-SiC composites reinforced with continuous PyC coated PAN-derived fibres or uncoated pitch-derived fibres were compared.Pitch-derived carbon fibres showed a lower degree of reaction with the matrix phase during sintering compared to PyC/PAN-derived fibres. The reason lies in the different microstructure of the carbon. The presence of a coating for PAN-derived fibres was found to be essential to limit the reaction at the fibre/matrix interface during SPS. However, coated bundles were more difficult to infiltrate, resulting in a less homogeneous microstructure.As far as the mechanical properties are concerned, specimens reinforced with coated PAN-derived fibres provided higher strengths and damage tolerance than uncoated pitch-derived fibres, due to the higher degree of fibre pull-out. On the other hand, the weaker fibre/matrix interface resulted in lower interlaminar shear, off-axis strength and ablation resistance. 相似文献
2.
Francesca R. Lamastra Mehdi Chougan Emanuele Marotta Samuele Ciattini Seyed Hamidreza Ghaffar Stefano Caporali Francesco Vivio Giampiero Montesperelli Ugo Ianniruberto Mazen J. Al-Kheetan Alessandra Bianco 《Ceramics International》2021,47(14):20019-20031
The impact of graphite nanoplatelets (GNPs) on the physical and mechanical properties of cementitious nanocomposites was investigated. A market-available premixed mortar was modified with 0.01% by weight of cement of commercial GNPs characterized by two distinctively different aspect ratios.The rheological behavior of the GNP-modified fresh admixtures was thoroughly evaluated. Hardened cementitious nanocomposites were investigated in terms of density, microstructure (Scanning Electron Microscopy, SEM and micro–Computed Tomography, μ-CT), mechanical properties (three-point bending and compression tests), and physical properties (electrochemical impedance spectroscopy, EIS and thermal conductivity measurements). At 28 days, all GNP-modified mortars showed about 12% increased density. Mortars reinforced with high aspect ratio GNPs exhibited the highest compressive and flexural strength: about 14% and 4% improvements compared to control sample, respectively. Conversely, low aspect ratio GNPs led to cementitious nanocomposites characterized by 36% decreased electrical resistivity combined with 60% increased thermal conductivity with respect to the control sample. 相似文献
3.
《Journal of the European Ceramic Society》2021,41(13):6238-6247
Ni-based alloys are believed to be the most suitable brazing fillers for SiC ceramic application in a nuclear environment. However, graphite, which severely deteriorates the mechanical property of the joint, is inevitable when Ni reacts with SiC. In this paper, Different amounts of Zr powders are mixed with Inconel 625 powders to braze SiC at 1400 °C. When Zr addition reaches 40 wt%, the brazed seam confirms the absence of graphite. This research proves that Zr can avoid the graphite’s formation by suppressing Ni’s activity. The room-temperature shear strength of the joint with graphite’s absence is tested to be 81.97 MPa, which is almost three times higher than that of the joint with graphite. The interfacial reaction process and mechanism of the SiC joint are investigated and explained in this paper using thermodynamic calculations. 相似文献
4.
《International Journal of Hydrogen Energy》2022,47(6):3580-3586
Renewable electricity-powered hydrogen production is an attractive alternative to unsustainable industrial processes, but the large-scale implantation of such sustainable technology still requires efficient and noble-metal-free electrocatalysts for driving cathodic hydrogen evolution reaction (HER), especially under alkaline conditions. In this paper, CoP nanowire array was in-situ developed on porous graphite felt (CoP/GF) as a new 3D electrocatalyst in facilitating hydrogen evolution electrocatalysis. This CoP/GF presents outstanding HER activity, requiring a low overpotential of 130 mV to deliver a current density of 20 mA cm?2 as tested in 1.0 M KOH. Furthermore, this free-standing catalyst exhibits impressive long-term durability of up to 50 h under working conditions. 相似文献
5.
《Ceramics International》2020,46(8):11622-11630
In the last decades, the production of ultra-high temperature composites with improved thermo-mechanical properties has attracted much attention. This study focuses on the effect of graphite nano-flakes addition on the microstructure, densification, and thermal characteristics of TiB2–25 vol% SiC composite. The samples were manufactured through spark plasma sintering process under the sintering conditions of 1800 °C/7 min/40 MPa. Scanning electron microscopy images demonstrated a homogenous dispersion of graphite flakes within the TiB2–SiC composite causing a betterment in the densification process. The thermal diffusivity of the specimens was gained via the laser flash technique. The addition of graphite nano-flakes as a dopant in TiB2–SiC did not change the thermal diffusivity. Consequently, the remarkable thermal conductivity of TiB2–SiC remained intact. It seems that the finer grains and more interfaces obstruct the heat flow in TiB2–SiC–graphite composites. Adding a small amount of graphite nano-flakes enhances the densification of the mentioned composite by preventing the grain growth. 相似文献
6.
Maria Dimopoulou Vassilis Kontogiorgos 《International Journal of Food Science & Technology》2020,55(5):1943-1949
Soluble dietary fibres from sugarcane bagasse were extracted under alkaline conditions and characterised. Precipitated fibres were dialysed, and the fibre composition was evaluated before and after the dialysis step. Compositional analysis indicated that the fibres both before and after dialysis consisted of 39% w/w total sugars, 16% w/w protein, 10% w/w Klason lignin and 30% w/w ash. Xylose was the main neutral sugar followed by arabinose with glucose, galactose and uronic acids also present in all samples. The structural properties were also spectroscopically examined, which confirmed the presence of arabinoxylans. Macromolecular characterisation revealed that molecular weight is reduced after dialysis, indicating that a range of dietary fibres with different macromolecular characteristics may be obtained depending on the specific processing steps. The present work shows that soluble arabinoxylans may be obtained from sugarcane agricultural wastes that may be used as a source of novel dietary fibres. 相似文献
7.
Cr3C2 coatings were successfully prepared on the surface of graphite flakes via a molten salt route by mixing Cr powders with natural graphite flakes in a binary LiCl-KCl salt at 450–950?°C for 4–12?h. The phases and microstructures of the coatings were verified by its XRD/XPS spectra and SEM/AFM observations, respectively. Together with the dissolution/dispersion evidence of chromium powders after interaction with the salt, and the slightly increased particle sizes due to the formation of Cr3C2 coatings on graphite flakes, a ‘template-growth’ kinetic process was therefore proposed on the formation of such coatings in the molten salt. The resultant coatings decreased the contact angle between water and graphite from 101° to ~ 75° and lowered the apparent viscosities of graphite water slurry by two orders of magnitude accordingly, suggesting that the coatings will afford graphite with good processing abilities for carbon-water based materials. 相似文献
8.
Herein, electrically conductive natural and synthetic yarns through electrophoretic deposition (EPD) technique were fabricated. A parametric study on the conductivity enhancement of the yarns is carried out by Taguchi method. Using this method, the desirable conditions are determined by studying the effects of important parameters on the electrical conductivity of the yarns in the EPD coating process. Based on the L18 design of experiments table, the preferred combination of factors to obtain the highest electrical conductivity of the yarns is found by Taguchi analysis. In addition, the Pareto ANOVA analysis is conducted to identify the major contributing factors on the electrical conductivity of the yarns. Characterisation techniques, such as scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR) in attenuated total reflectance (ATR) mode, and thermogravimetric analysis (TGA) are utilised for better understanding the microstructure and physical properties. When powered by only 3 V, the maximum temperature of a Joule heated conductive sample based on natural fibre yarns reached 102°C in less than 25 s. 相似文献
9.
In this paper, the hybridisation of multidirectional carbon fibre-reinforced composites as a means of improving the compressive performance is studied. The aim is to thoroughly investigate how hybridisation influences the laminate behaviour under different compression conditions and thus provide an explanation of the “hybrid effect”. The chosen approach was to compare the compressive performance of two monolithic carbon fibre/epoxy systems, CYTEC HTS/MTM44-1 and IMS/MTM44-1, with that of their respective hybrids. This was done by keeping the same layup throughout ((0/90/45/−45)2S) while replacing the angle plies in one case or the orthogonal plies in the other case with the second material, thus producing two hybrid systems. To investigate the compressive performance of these configurations, compact and plain compression test methods were employed which also allowed studying the sensitivity of compressive failure to specimen geometry and loading conditions. The experimental results and the subsequent fractographic analysis revealed that the hybridisation of selective ply interfaces influenced the location and severity of the failure mechanisms. Finally, in light of this knowledge, an update of the generic sequence of events, previously suggested by the authors, which lead to global fracture in multidirectional fibre-reinforced composites under compression is presented. 相似文献
10.
The experimental investigation is focused on the thermo-mechanical behaviour of thin concrete panels reinforced with GFRP rebars. The considered thin panels (thickness of 4 cm) were exposed to increasing temperature and bending loading. These concrete elements are typical for low bearing function concrete layers in façade claddings. The influence of two aspects was studied: the concrete cover and the external surface of rebars. The heating condition was such that the temperature of the internal GFRP rebars reached about the transition temperature of the resins. This allowed to verify the variation of the deformability and the load carrying capacity of the panels with post-heating bending tests. As main outcome, the imposed temperature did not generate evident degradation of the GFRP reinforcement and of its adhesion to the concrete, while a reduction of the initial global stiffness was measured. 相似文献