全文获取类型
收费全文 | 1031篇 |
免费 | 77篇 |
国内免费 | 135篇 |
专业分类
综合类 | 46篇 |
化学工业 | 13篇 |
金属工艺 | 817篇 |
机械仪表 | 22篇 |
矿业工程 | 9篇 |
能源动力 | 12篇 |
轻工业 | 1篇 |
武器工业 | 5篇 |
无线电 | 14篇 |
一般工业技术 | 222篇 |
冶金工业 | 81篇 |
原子能技术 | 1篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 35篇 |
2021年 | 22篇 |
2020年 | 25篇 |
2019年 | 32篇 |
2018年 | 20篇 |
2017年 | 28篇 |
2016年 | 24篇 |
2015年 | 30篇 |
2014年 | 62篇 |
2013年 | 34篇 |
2012年 | 45篇 |
2011年 | 69篇 |
2010年 | 39篇 |
2009年 | 49篇 |
2008年 | 44篇 |
2007年 | 45篇 |
2006年 | 69篇 |
2005年 | 46篇 |
2004年 | 47篇 |
2003年 | 41篇 |
2002年 | 66篇 |
2001年 | 54篇 |
2000年 | 54篇 |
1999年 | 53篇 |
1998年 | 61篇 |
1997年 | 30篇 |
1996年 | 34篇 |
1995年 | 26篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 1篇 |
排序方式: 共有1243条查询结果,搜索用时 5 毫秒
31.
Shigeji Taniguchi Toshio Shibata Naoyuki Asanuma Hanyi Lou Fuhui Wang Weitao Wu 《Oxidation of Metals》1993,39(5-6):457-473
The oxidation behavior of TiAl coupons coated with a fine-grain Co-30Cr-4Al (mass %) film of about 30-m thickness has been studied at 1100–1400 K in a flow of purified oxygen at atmospheric pressure for up to 500 ks. Three oxidation stages were recognized: initial transient, parabolic, and accelerated stages. However, at 1100 K a parabolic stage continues for more than 800 ks. The activation energy for parabolic oxidation agrees with reported values for the oxidation of alumina-former alloys, although the mass gains during the parabolic stages are relatively small at 1200 and 1300 K. Micropores developed mainly at the scale/coating and coating/substrate interfaces as oxidation proceeded. This is attributable to recrystallization of the coating during oxidation and a Kirkendall effect due to preferential diffusion of Co into the substrate. The accelerated oxidation can be explained in terms of the formation of rutile mounds on the scale. 相似文献
32.
33.
In this study, TiB2 cermet and TiAl-based alloy are vacuum brazed successfully by using Ag-Cu-Ti filler metal.The microstructural analyses indicate that two reaction products, Ti ( Cu, Al ) 2 and Ag bused solid solution ( Ag ( s. s ) ) , are present in the brazing seam, and the iuterface structure of the brazed joint is TiB2/TiB2 Ag ( s. s ) /Ag ( s. s ) Ti ( Cu,Al)2/Ti( Cu, Al)2/TiAl. The experimental results show that the shear strength of the brazed TiB2/TiAl joints decreases us thebrazing time increases at a definite brazing temperature. When the joint is brazed at 1 223 K for 5 min, a joint strength up to 173 MPa is achieved. 相似文献
34.
电磁无接触成形过程熔体形状的数值模拟及实验研究 总被引:1,自引:0,他引:1
应用有限元方法模拟计算了电磁约束成形过程中感应器结构、固/液界面位置、熔体上顶面位置、电流频率及熔体种类对熔体形状的作用规律。结果表明:喇叭形内壁的感应器中熔体可获得侧面基本垂直的理想形状;固/液界面、熔体上顶面位置对熔体形状有明显的影响:电流频率的变化对熔体成形形状的影响很小:在感应器结构、固/液界面及熔体上顶面位置等确定后,合金种类对熔体形状几乎没有影响。同时对电磁成形规律进行了研究,表明实验与模拟计算的结果取得了很好的吻合。用电磁成形方法完成了Al合金、TiAl化合物和Ni基高温合金的无接触成形,制备出了样件,并对组织实现了定向控制。 相似文献
35.
Powder metallurgically produced Ti-48% Al-2%W alloys were oxidized between 800 and 1050°C in air. The W-addition was quite
effective in providing isothermal and cyclic oxidation resistance. The alloys oxidized parabolically up to 1050°C during isothermal
oxidation, with small weight gains. The scales were adherent up to 900°C during cyclic oxidation. Oxide scales consisted primarily
of an outer TiO2 layer, an intermediate Al2O3 layer, and an inner (TiO2+Al2O3) mixed layer. Tungsten was present below the intermediate Al2O3 layer. and also at the scale-matrix interface as W-enriched compounds. Below the oxide scale, a Ti3Al zone containing some W and O existed. 相似文献
36.
SiO32-对TiAl合金微弧氧化陶瓷层的影响 总被引:3,自引:0,他引:3
采用自行研制的脉冲微弧氧化设备,在TiAl合金表面制备了微弧氧化陶瓷层.测定了TiAl合金微弧氧化陶瓷层在高温循环氧化条件下的氧化动力学曲线。研究了在微弧氧化处理溶液中加入SiO3^2-对陶瓷层性能的影响。实验结果显示:经过微弧氧化处理后试样的高温氧化动力学曲线大致呈抛物线规律,其表面的陶瓷氧化膜具有保护性;在微弧氧化处理溶液中加入SiO3^2-后,微弧氧化处理的TiAl合金的使用温度可提高到1273K。利用扫描电子显微镜(SEM)和X射线衍射仪(XRD)对陶瓷层的显微结构和物相组成进行分析,发现其物相组成为含量约占80%的Al2TiO5,11%的TiO2以及9%的SiO2。这表叫SiO2能仃效抑制Al2TiO5在高温下的分解,从而大幅提高TiAl合金的抗高温氧化性。 相似文献
37.
The oxidation behavior of the titanium aluminides Ti-50Al and Ti-48Al-5Nb has been investigated in Ar+20%O2 and in air at 900°C. Thermogravimetric studies in combination with structural analyses using optical metallography, SEM/EDX and X-ray diffraction show a marked influence of nitrogen on the composition and growth rate of the oxide scales. For a more detailed study concerning the effect of nitrogen on the scale-growth kinetics, thermogravimetrical analyses were carried out during which the gas atmosphere was changed from air to Ar–O2, and vice versa, without intermediate cooling of the specimen. The results show, that nitrogen adversely affects the formation of the initially formed alumina scale and that it enhances the growth rate of the rapidly growing Ti-rich oxide. This effect was observed in both alloys investigated, although the thermogravimetric results at first sight indicated an opposite effect for the Nb-containing alloy. This apparent contradiction is caused by internal oxidation which occurs in this alloy during exposure in Ar–O2. 相似文献
38.
Ti-Al-Nb-W-B合金不同工艺处理状态的组织演变及钨的作用 总被引:2,自引:1,他引:2
采用电子探针观察和分析了不同工艺处理状态下Ti-Al-Nb-w-B合金的背散射组织。结果表明,热处理后,由于合金中的γ等轴晶的数量增多、粒径长大,β(B2)析出相亦增多,合金的微观组织从近层片状组织转变为近双态组织;钨在γ相中的含量较低,且扩散能力很低,对γ晶的等轴化影响不大,不论钨含量(≤0.7%,摩尔分数)为多少,其γ等轴晶的尺寸差别不大;随着钨含量的增多,白色的第二相析出量越多,且优先在仅α2/γ界面和台阶处形核,析出相主要分布在α2相的两端。 相似文献
39.
Liu Zhijian Qu Xuanhui Huang Baiyun Powder Metallurgy Research Institute Central South University of Technology Changsha 《中国有色金属学会会刊》1997,(1)
TiAlALLOYSPREPAREDBYTHERMALEXTRUSIONOFELEMENTALPOWDERMIXTURES①LiuZhijian,QuXuanhui,HuangBaiyunPowderMetallurgyResearchInstitu... 相似文献
40.
ADVANCEINTi_3AlANDTiAlINTERMETALLICSRESEARCHINCISRIZHONGZengyong;ZOUDunxu;LIShiqiong(CentralIronandSteelResearchInstitute,Bei?.. 相似文献