全文获取类型
收费全文 | 39183篇 |
免费 | 4312篇 |
国内免费 | 2362篇 |
专业分类
电工技术 | 1352篇 |
综合类 | 3283篇 |
化学工业 | 10962篇 |
金属工艺 | 4783篇 |
机械仪表 | 1719篇 |
建筑科学 | 5365篇 |
矿业工程 | 820篇 |
能源动力 | 820篇 |
轻工业 | 1992篇 |
水利工程 | 434篇 |
石油天然气 | 960篇 |
武器工业 | 621篇 |
无线电 | 1250篇 |
一般工业技术 | 9285篇 |
冶金工业 | 1298篇 |
原子能技术 | 102篇 |
自动化技术 | 811篇 |
出版年
2024年 | 232篇 |
2023年 | 585篇 |
2022年 | 1047篇 |
2021年 | 1310篇 |
2020年 | 1377篇 |
2019年 | 1182篇 |
2018年 | 1139篇 |
2017年 | 1530篇 |
2016年 | 1594篇 |
2015年 | 1514篇 |
2014年 | 2009篇 |
2013年 | 2069篇 |
2012年 | 2715篇 |
2011年 | 2816篇 |
2010年 | 2228篇 |
2009年 | 2384篇 |
2008年 | 1894篇 |
2007年 | 2684篇 |
2006年 | 2543篇 |
2005年 | 2104篇 |
2004年 | 1694篇 |
2003年 | 1536篇 |
2002年 | 1322篇 |
2001年 | 1187篇 |
2000年 | 1027篇 |
1999年 | 843篇 |
1998年 | 666篇 |
1997年 | 580篇 |
1996年 | 466篇 |
1995年 | 387篇 |
1994年 | 316篇 |
1993年 | 282篇 |
1992年 | 178篇 |
1991年 | 142篇 |
1990年 | 74篇 |
1989年 | 53篇 |
1988年 | 39篇 |
1987年 | 28篇 |
1986年 | 5篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1977年 | 1篇 |
1967年 | 1篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
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
13.
以C9油与甲基丙烯酰氧乙基三甲基氯化胺的共聚物P(C9-DMC)为乳化剂制备苯/丙阳离子乳胶粒,并以其为模板,利用直接包覆法制备了由17 nm左右微晶体堆成的ZrO2空心微球。所制得的样品采用FT-IR、XRD、TEM和SEM等进行了表征。 相似文献
14.
15.
The formation of aluminum matrix composites fabricated by exothermic dispersion reaction in A1-TiO2-B2O3 system was investigated. The thermal analysis results show that the reactions are spontaneous and exothermic. The Gibbs free energy of α-Al2O3 is the lowest among all the combustion products, followed by TiB2 and Al3Ti. It is noted that when the B2O3/TiO2 mole ratio is below 1, the reaction products are composed of particle-like α-Al2O3, TiB2 and rod-like Al3Ti. The α-Al2O3 crystallites, resulting from the reaction between A1 and TiO2 or B2O3, are segregated at the grain boundaries due to a lower wettability with the matrix. SEM micrographs show that rod-like Al3Ti phase distributes uniformly in the matrix. When the BEO3/TiO2 mole ratio is around 1, the Al3Ti phase almost disappears in the composites, and the distribution of α-Al2O3 particulates is improved evidently. 相似文献
16.
G. Ranzi M. A. Bradford B. Uy 《International journal for numerical methods in engineering》2004,61(5):657-672
The use of the conventional semi-analytical stiffness method in finite element analysis, in which interpolation polynomials are used to develop the stiffness relationships, leads to problems of curvature locking when beam-type elements are developed for composite members with partial interaction between the materials of which it is comprised. The curvature locking phenomenon that occurs for composite steel–concrete members is quite well reported, and the general approach to minimizing the undesirable ramifications of curvature locking has been to use higher-order polynomials with increasing numbers of internal nodes. This paper presents an alternate formulation based on a direct stiffness approach rather than starting from pre-defined interpolation polynomials, and which does not possess the undesirable locking characteristics. The formulation is based on a more general approach for a bi-material composite flexural member, whose constituent materials are joined by elastic shear connection so as to provide partial interaction. The stiffness relationships are derived, and these are applied to a simply supported and a continuous steel–concrete composite beam to demonstrate the efficacy of the method, and in particular its ability to model accurately both very flexible and very stiff shear connection that causes difficulties when implemented in competitive semi-analytical algorithms. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
17.
WC对Cu/WC_P复合材料性能及组织的影响 总被引:8,自引:0,他引:8
通过WC含量对WC/Cu复合材料性能的影响,确定了冷压-烧结法制备Cu/WC材料的适宜WC含量为10vol%左右。并就WC对该材料组织和再结晶行为的影响进行了有益的探讨。 相似文献
18.
利用挤压铸造制备氧化铝/锌合金复合材料,在扫描电镜(SEM)上观察复合材料的界面。结果表明,在复合材料中纤维与基体间存在致密界面层,合金元素通过适当的化学反应可改善纤维与基体间的结合;在凝固过程中,纤维/基体界面上的硅在共晶体的共生生长过程中起了领先相作用,导致复合材料的共晶转变是由铝硅共晶转变和锌铝共晶转变两者组成。 相似文献
19.
用附聚法和降粘法浓缩SBR1502胶浆制取道路沥青改性用胶乳。结果表明:总固物质量分数可由(21±2)%上升到45%~50%。该胶乳与齐鲁石化公司炼油厂100号乙沥青混合,改性后的道路沥青具有良好的使用性能,可满足高等级路面沥青的技术要求。 相似文献
20.
单轴-平面W型复合锶铁氧体的制备及其吸波特性研究 总被引:3,自引:0,他引:3
用草酸盐共沉淀和微量掺杂法研制六角晶系W型Ni,Zn,Co,Al多元复合锶铁氧体,通过调节Ni2W同Co2W的摩尔比例,可使该种铁氧体易磁化方向从C单轴型向垂于C轴的平面型转化,控制置换锶铁氧体中部分Fe3 的微量掺杂Al3 ,可以调整4πMs值,提高磁晶各向异性场,测试分析了5种不同含Co量的W型复合锶铁氧体粉料涂层的吸波特性,发现其自然共振吸收峰随Co含量增加向低频方向偏移,最高吸收峰可达32.8dB,是适用于电子隐形技术的高品位的微波吸收剂。 相似文献