全文获取类型
收费全文 | 3301篇 |
免费 | 227篇 |
国内免费 | 251篇 |
专业分类
电工技术 | 137篇 |
综合类 | 194篇 |
化学工业 | 817篇 |
金属工艺 | 622篇 |
机械仪表 | 111篇 |
建筑科学 | 101篇 |
矿业工程 | 59篇 |
能源动力 | 103篇 |
轻工业 | 393篇 |
水利工程 | 14篇 |
石油天然气 | 212篇 |
武器工业 | 18篇 |
无线电 | 127篇 |
一般工业技术 | 538篇 |
冶金工业 | 213篇 |
原子能技术 | 99篇 |
自动化技术 | 21篇 |
出版年
2024年 | 25篇 |
2023年 | 108篇 |
2022年 | 131篇 |
2021年 | 120篇 |
2020年 | 110篇 |
2019年 | 83篇 |
2018年 | 72篇 |
2017年 | 130篇 |
2016年 | 107篇 |
2015年 | 102篇 |
2014年 | 150篇 |
2013年 | 177篇 |
2012年 | 255篇 |
2011年 | 272篇 |
2010年 | 197篇 |
2009年 | 218篇 |
2008年 | 125篇 |
2007年 | 205篇 |
2006年 | 224篇 |
2005年 | 171篇 |
2004年 | 140篇 |
2003年 | 124篇 |
2002年 | 74篇 |
2001年 | 78篇 |
2000年 | 58篇 |
1999年 | 28篇 |
1998年 | 31篇 |
1997年 | 35篇 |
1996年 | 43篇 |
1995年 | 45篇 |
1994年 | 29篇 |
1993年 | 21篇 |
1992年 | 27篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有3779条查询结果,搜索用时 31 毫秒
91.
Andreas Förner Jan Vollhüter Anna Krapf Abdullah Jamjoom Daniel Hausmann Benjamin Wahlmann Zongwen Fu Carolin Körner Steffen Neumeier Mathias Göken 《Advanced Engineering Materials》2023,25(15):2300407
By increasing the density of interfaces in NiAl–CrMo in situ composites, the mechanical properties can be significantly improved compared to conventionally cast material. The refined microstructure is achieved by manufacturing through electron beam powder bed fusion (PBF-EB). By varying the process parameters, an equiaxed or columnar cell morphology can be obtained, exhibiting a plate-like or an interconnected network of the (Cr,Mo) reinforcement phase which is embedded in a NiAl matrix. The microstructure of the different cell morphologies is investigated in detail using scanning electron microscope, transmission electron microscopy, and atom probe tomography. For both morphologies, the mechanical properties at elevated temperatures are analyzed by compression and creep experiments parallel and perpendicular to the building direction. In comparison to cast NiAl and NiAl–(Cr, Mo), the yield strength of the PBF-EB fabricated specimens is significantly improved at temperatures up to 1,027 °C. While the columnar morphology exhibits the best improved mechanical properties at high temperatures, the equiaxial morphology shows nearly ideal isotropic mechanical behavior, which is a substantial advantage over directionally solidified material. 相似文献
92.
High-temperature oxidation of Al-deposited stainless-steel foils 总被引:2,自引:0,他引:2
The oxidation resistance of Al-deposited Fe–Cr–Al foils containing small amounts of La and Ce was assessed by a cyclic oxidation test with temperature varying between room temperature and 1323 K to 1423 K in static air. (1) The Al content of Fe–Cr–Al–La, Ce foils can be increased by depositing an Al layer from the vapor phase. The deposition of a 1-m-thick Al layer on both sides of the 50-m-thick foil is equivalent to a 1.5 mass% increase in the Al content. The deposited Al diffuses into the foil during heat treatment. The uniform distribution of Al is obtained by heating at 1273 K for 18 ks. (2) After the initial transition stage the oxidation follows the parabolic law until breakaway sets in. The scale consists mainly of -Al2O3 during the parabolic period. (3) The increase in the Al content by more than 5 mass% by the Al-deposition remarkably improves high-temperature oxidation resistance (smaller parabolic rate constant and longer protection time). (4) The Al-deposited foils have better oxidation resistance than the conventional foils with the same contents of Al and rare-earth elements. This is attributable to the different nature of the initially formed oxide on the Al-deposited foil. (5) The so-called rare-earth element effect was also observed for the Al-deposited foils. Predominant diffusion of oxygen through the Al2O3 scale and vacancy-sink mechanism are applicable to the present results. 相似文献
93.
94.
High-temperature superconductors in superconductor apparatuses are subjected to mechanical strains under operating conditions.These strains cause the degradation of the critical current densities and influence AC losses in the superconductors.Based on the dynamic process of thermomagnetic interaction,we report the results of numerical analysis of AC losses in an infinite high-temperature superconducting slab subjected to a uniform in-plane strain in an alternating external magnetic field parallel to the sample surface.The numerical analysis shows the details of electromagnetic phenomena in the slab and the dependences of AC loss on various external parameters including the uniform strain in the slab and the amplitude and frequency of the external magnetic field.In this paper,we find that whether the magnetic field fully penetrates the superconductor is the key factor that influences the features of AC loss.When the magnetic field cannot fully penetrate the superconductor,the loss rises with increasing strain or decreasing frequency.When the magnetic field can fully penetrate the superconductor,the feature is just opposite.We also analyze the effects of periodic strain on AC loss.It is interesting to find that when the periodic strain frequency equals the external magnetic field frequency,the AC loss reaches the maximum,regardless if the magnetic field fully penetrates the superconductor or not. 相似文献
95.
孔丽 《吉林化工学院学报》2012,(9):9-11
采用高温固相法合成了SrCaSiO4:Eu,并研究了其光谱性能以及Eu的掺杂浓度对发射光谱强度的影响.研究表明,荧光粉SrCaSiO4:Eu2+的激发光谱位于250~400 nm的宽带,而发射光谱是主峰为500 nm的宽带,所以此荧光粉可以和紫外LED匹配,发射蓝绿光.SrCaSiO4:Eu中的激活剂Eu2+的猝灭浓度为0.5mol%. 相似文献
96.
建筑用Q235钢在高温(火灾)条件下的力学性能研究 总被引:1,自引:0,他引:1
对建筑常用的Q235钢在火灾情况下的力学性能分析,获得了Q235钢在高温下的屈服强度、极限强度、弹性模量、伸长率等力学性能指标的变化规律,并在恒温加载和恒载加温两种试验下对Q235钢进行强度对比。 相似文献
97.
凝析气藏油气水三相PVT相态特征测试及分析 总被引:4,自引:4,他引:4
常规凝析油气体系PVT相态测试方法忽略了气态凝析水对凝析油气体系相态的影响,而国内外凝析气藏开发实践表明,气态凝析水对凝析油气体系相态特征的影响不应被忽略.为了更有效地指导凝析气藏的开发,必须建立考虑气态凝析水的凝析油气体系PVT相态测试和计算方法.探索设计了富含气态凝析水的凝析油气体系PVT相态测试方法,并与常规凝析油-气两相平衡体系的PVT测试结果进行了对比,分析了考虑气态水组分的存在对凝析油气体系相态的影响. 相似文献
98.
1 Introduction With the development of astronautical technology, more and more functions of the components of high-temperature materials are required. In order to meet the demand, far more advanced higher temperature materials, such as the high-temperature alloys or high-temperature melting point materials, should be first developed. In addition, the molding technological process of high-temperature materials should also be developed. Nowadays the traditional high-temperature technological pro… 相似文献
99.
为了防止微波高温烧结过程中,升温十分迅速,发生局部过烧,用单片机设计高温烧结微波炉的自动控制系统.介绍了其工作原理、组成框图、硬件设计以及软件程序流程;并详细说明电路设计.该系统已正常运行于所开发的YC-Ⅱ型微波高温烧结炉上. 相似文献
100.