全文获取类型
收费全文 | 1368篇 |
免费 | 19篇 |
国内免费 | 70篇 |
专业分类
电工技术 | 7篇 |
综合类 | 55篇 |
化学工业 | 159篇 |
金属工艺 | 359篇 |
机械仪表 | 56篇 |
建筑科学 | 30篇 |
矿业工程 | 29篇 |
能源动力 | 160篇 |
轻工业 | 96篇 |
石油天然气 | 5篇 |
武器工业 | 4篇 |
无线电 | 47篇 |
一般工业技术 | 289篇 |
冶金工业 | 48篇 |
原子能技术 | 22篇 |
自动化技术 | 91篇 |
出版年
2024年 | 1篇 |
2023年 | 14篇 |
2022年 | 30篇 |
2021年 | 43篇 |
2020年 | 33篇 |
2019年 | 28篇 |
2018年 | 29篇 |
2017年 | 47篇 |
2016年 | 35篇 |
2015年 | 65篇 |
2014年 | 77篇 |
2013年 | 69篇 |
2012年 | 92篇 |
2011年 | 115篇 |
2010年 | 62篇 |
2009年 | 98篇 |
2008年 | 84篇 |
2007年 | 61篇 |
2006年 | 61篇 |
2005年 | 53篇 |
2004年 | 47篇 |
2003年 | 40篇 |
2002年 | 41篇 |
2001年 | 40篇 |
2000年 | 33篇 |
1999年 | 30篇 |
1998年 | 36篇 |
1997年 | 21篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1994年 | 14篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有1457条查询结果,搜索用时 9 毫秒
991.
《材料与设计》2015
Three metallic coatings with textured surfaces, made of rhenium, tungsten and molybdenum, were studied in the frame of the Solar Probe Plus mission (NASA) as candidate materials. The role of these coatings is to dissipate a maximum of energy from a hot instrument facing the Sun, by the mean of their high total hemispherical emissivity. The total hemispherical emissivity of the three coatings was measured in the temperature range 1100–1900 K, as well as over time in order to study their high temperature stability. Various emissivity levels were obtained depending on the surface texture. The highest total hemispherical emissivity was obtained on a rhenium coating, with an emissivity of 0.8 in the temperature range 1300–1700 K. However, this rhenium coating with a fine, sharp surface texture, presented an instability at high temperature, which might limit its optimal operating temperature to about 1500 K. As for the tungsten coating, the total hemispherical emissivity was increased by a factor 2 due to the enhanced surface texturation and its great stability over the whole temperature range was shown. 相似文献
992.
Notch Effect of Materials: Strengthening or Weakening? 总被引:2,自引:0,他引:2
Ruitao Qu Peng Zhang Zhefeng Zhang 《材料科学技术学报》2014,30(6):599-608
Notch is a very important geometry with widespread applications in engineering structural components. Finding a universal equation to predict the effect of notch on strength of materials is of much significance for structural design and materials selection. In the present work, we tried to find this universal equation from experimental results of metallic glasses (MGs) and other materials as well as theoretical derivations based on a universal fracture criterion (Qu and Zhang, Sci. Rep. 3 (2013) 1117). Experimental results showed that the notch effect of the studied MG was affected by the notch geometry characterized by the stress concentration factor Kt. As Kt becomes smaller, the notch strength ratio (NSR, which is the ratio of nominal ultimate tensile strength (UTS) of the notched sample to UTS of the unnotched sample) increases. By comparing MGs with other materials like brittle ceramics and ductile for ductile metals but smaller for brittle effect on strength of materials: NSR = equation was found to be consistent with crystalline metals, we find that when Kt is same, the NSR is larger ceramics. Theoretically, we derived a universal equation for notch M/Kt, where M is a constant related to materials. This universal the experimental results. 相似文献
993.
L.C. Agudelo-Morimitsu J. De La Roche A. Ruden D. Escobar E. Restrepo-Parra 《Ceramics International》2014
W/WC bilayers were grown using the DC magnetron sputtering technique and varying substrate temperature. The mechanical and tribological behaviors were characterized using the nanoindentation and pin-on-disk techniques. The hardness and Young's modulus tended to increase, while the coefficient of friction tended to be stable with increasing substrate temperature. Moreover, better mechanical and tribological performances were observed for all of the coated systems compared with the uncoated steel. Furthermore, the inclusion of a W interlayer did not significantly influence the hardness; nevertheless, this interlayer dramatically improved the coating tribological behavior, thus producing less coating damage and decreasing the wear rate. 相似文献
994.
995.
996.
The main focus of this paper is on materials for radiant burners application. Two advanced metallic alloys, a Ni and Fe-based alloy are studied and compared to a reference ferritic stainless steel. Oxidation kinetics of such alloys at different temperatures are reported. Oxide formation mechanisms are discussed. Furthermore, thermo-mechanical resistance and eventual strengthening mechanism in temperature are studied. Finally, technical and brief tentative economical analysis of different alloys as potential candidates for the fabrication of radiant burners are given. 相似文献
997.
Cooling rate-induced softening in Y-based metallic glasses were verified in this work. By varying the speed of the roller in the melt-spinning process, it is found the hardness of the ribbon decrease with the cooling rate. Nanoindentation test also indicated that the ribbon at a higher cooling rate shows higher deformation energy. Contrary to crystalline materials, whose hardness usually increases with the cooling rate, the softening of metallic glasses is attributed to high concentration of defects frozen by fast cooling, and thus more structural relaxation during deformation. 相似文献
998.
A micromechanical model for the prediction of the temperature fracture behaviour dependence in metallic alloys 总被引:1,自引:0,他引:1
Andrea Carpinteri Alan Davoli Sabrina Vantadori 《Engineering Fracture Mechanics》2008,75(12):3646-3662
In the present paper, a micro-mechanical model based on energetic considerations is developed to simulate the effect of environmental temperature on the fracture toughness of metallic alloys. By considering a reference elementary volume (REV) with the same composition of the real material, the stress-strain field inside such a volume and the corresponding strain energy due to a temperature variation is determined. The energy balance to determine the material fracture toughness is generalised in order to take into account the temperature effects. The proposed micro-mechanical model is governed by few parameters which can be simply estimated, and allows us to determine the fracture toughness for any temperature below the room temperature. Such a model is applied to three metallic alloys which show a ductile-brittle transition temperature: ASTM A471, Carbon Steel D6ac, Steel S275 J2. From the comparison of theoretical results with experimental data, it can be concluded that the model seems to be able to correctly predict the fracture toughness at low temperatures. 相似文献
999.
X-ray diffraction (XRD) analysis revealed that nanocrystalline Ti hydride(s) was in situ formed during mechanical milling 1:1 NaH/Al mixture with metallic Ti powder. The composition of the formed Ti hydrides varies slightly upon changing the milling atmosphere from inert Ar to reactive H2. Directly doping sodium alanate with commercial Ti hydride was found to result in similar dehydriding kinetics, hydrogen capacity, and cycling stability to those of the samples doped with metallic Ti. Moreover, according to the XRD results, the Ti hydride(s) remains stable in the de-/hydrogenation cycles. On the basis of these results, a discussion regarding the nature of catalytically active species was given. 相似文献
1000.
The influence of the quenching rate (from 5 m/s to 40 m/s) on the crystallization behaviors of melt-spun Mg63Ni22Pr15 metallic glasses has been studied. The isochronal differential scanning calorimeter (DSC) measurement at 20 K/min shows that the transition temperatures increase with the quenching rate, while the parameters of the glass-forming ability keep constant. The kinetics of isothermal crystallization performed at 481 K within the supercooled liquid region is discussed with some nucleation and growth models. The fittings show that with decreasing quenching rate, the quenched-in nucleation becomes more important and even dominant in the crystallization process. 相似文献