全文获取类型
收费全文 | 9824篇 |
免费 | 669篇 |
国内免费 | 1134篇 |
专业分类
电工技术 | 105篇 |
综合类 | 476篇 |
化学工业 | 1734篇 |
金属工艺 | 4057篇 |
机械仪表 | 480篇 |
建筑科学 | 73篇 |
矿业工程 | 153篇 |
能源动力 | 204篇 |
轻工业 | 64篇 |
水利工程 | 2篇 |
石油天然气 | 247篇 |
武器工业 | 198篇 |
无线电 | 491篇 |
一般工业技术 | 2178篇 |
冶金工业 | 960篇 |
原子能技术 | 101篇 |
自动化技术 | 104篇 |
出版年
2024年 | 32篇 |
2023年 | 183篇 |
2022年 | 260篇 |
2021年 | 306篇 |
2020年 | 329篇 |
2019年 | 297篇 |
2018年 | 270篇 |
2017年 | 345篇 |
2016年 | 328篇 |
2015年 | 380篇 |
2014年 | 423篇 |
2013年 | 532篇 |
2012年 | 465篇 |
2011年 | 588篇 |
2010年 | 476篇 |
2009年 | 552篇 |
2008年 | 454篇 |
2007年 | 667篇 |
2006年 | 621篇 |
2005年 | 435篇 |
2004年 | 450篇 |
2003年 | 431篇 |
2002年 | 476篇 |
2001年 | 450篇 |
2000年 | 409篇 |
1999年 | 347篇 |
1998年 | 243篇 |
1997年 | 225篇 |
1996年 | 187篇 |
1995年 | 107篇 |
1994年 | 100篇 |
1993年 | 75篇 |
1992年 | 70篇 |
1991年 | 23篇 |
1990年 | 38篇 |
1989年 | 20篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
F. Schröder R. M. Ward A. R. Walpole R. P. Turner M. M. Attallah J.-C. Gebelin 《Materials Science & Technology》2015,31(3):372-384
Linear friction welding of the Ti6Al4V alloy is studied. A new definition of the energy input rate is proposed, based on an integration over time of the in-plane force and velocity; a strong correlation with the upset rate is then found. The effective friction coefficient is estimated to be 0·5±0·1 for varying frequencies and amplitudes, with only a weak dependence on the processing conditions displayed. A model is proposed that accounts for both the conditioning and equilibrium stages of the process, which is shown to be in good agreement with the experimental data. The model is used to study the mechanism by which the flash is formed. A criterion is proposed by which the rippled nature of its morphology can be predicted. 相似文献
3.
4.
采用凝胶成型法制备加氢催化剂载体,并进行了工业放大试验。通过BET、NH3-TPD、H2-TPR等表征手段及实际的加氢反应性能评价对凝胶成型法制备的载体及加氢催化剂与常规方法进行对比分析,结果表明,采用凝胶成型法所制得的载体及催化剂均具有较高的孔体积和比表面积、较低的堆密度,其机械强度可满足工业要求,总酸量及中强酸酸量得到提升,催化剂活性组分与载体强结合力得到削弱,金属利用率提高,应用性能明显优于传统方法制备的加氢催化剂载体。通过该方法完成了加氢催化剂载体的工业生产,所生产的载体应用于天津院THDS-3加氢精制催化剂取得了良好的工业应用效果。 相似文献
5.
The bonding of β'-Al2O3 and pyrex glass to Al matrix composites by anodic bonding process is achieved. The microstructure of the bonded interface and the joining mechanisms are analyzed with scanning electron microscope (SEM), energy dispersive X-ray fluorescence spectrometer (EDX). It is observed that the bonding region across the interface consists of the metal layer, oxide transitional layer and the ceramic layer, with the transitional layer composed of surface region and sub-surface region. The bonding process can mainly be categorized into anodic bonding process and solid state diffusing process. The pile-up of the ions and its drift in the interface area are the main reasons for anode oxidation and joining of the interface. The temperature, voltage and the drift ions in the ceramic or glass during the bonding process are the essential conditions to solid state diffusing and oxide bonding at the interface. The voltages, temperature, pressure as well as the surface state are the main factors that influence the anodic bonding. 相似文献
6.
Takayuki Honma Yuichiro Kuroki Tomoichiro Okamoto Masasuke Takata Yukihiro Kanechika Masanobu Azuma Hitofumi Taniguchi 《Ceramics International》2008,34(4):943-946
Aluminum nitride ceramics were prepared by sintering with 0–4.8 mass% of Ca3Al2O6 (C3A) as a sintering additive. The transmittance in the range of 260–550 nm increased with increasing amount of C3A. The cathodoluminescence intensity attributed to oxygen-induced defects decreased with increasing amount of C3A. From the results, the increase of the transmittance in the range of 260–550 nm was considered to be related to the decrease of the oxygen-induced defect density. 相似文献
7.
均匀设计法分析制备过程对钴钼硫化物催化剂机械强度的影响 总被引:1,自引:1,他引:0
建立了CoMoP/Al2O3加氢精制催化剂机械强度及其可靠性在制备过程中的数学模型,采用均匀设计考察了浸渍、干燥、煅烧、硫化4个制备过程中,浸渍时间、干燥温度、干燥时间、煅烧温度、煅烧时间、硫化温度和硫化升温速率7个实验因子对催化剂强度均值、Weibull模量的影响,同时考察了这些因素对颗粒密度的影响。方差分析表明所有模型都是充足的。实验结果表明,硫化过程是影响催化剂强度均值的主要过程。在实验范围内提高硫化温度、降低硫化时的升温速率有利于提高催化剂的强度。影响催化剂Weibull模量的因素主要为各个制备过程的交互效应。要提高催化剂强度的可靠性就必须全面考虑催化剂制备的各个过程,特别是各个制备过程的交互效应。 相似文献
8.
9.
Exchange and oxidation of C16O were investigated at 450°C on 18O-predosed Rh and Pt catalysts supported on A12O3, CeO2 and CeO2-Al2O3. In all cases, a rapid exchange of C16O with the surface can be observed. CO oxidation leads to C16O2, C16O18O and C18O2. Significant formation of C16O2 is due to the relatively high 16O coverage in reaction resulting from the C16O exchange and from an exchange between O surface species and 16O internal atoms. Hydrogen is also formed via a water-gas shift reaction (CO + surface OH) in higher proportion on CeO2-containing catalysts than on A12O3. Chlorine inhibits all the reactions (exchange, oxidation and WGS) and particularly the internal exchange. 相似文献
10.