全文获取类型
收费全文 | 44937篇 |
免费 | 4980篇 |
国内免费 | 2645篇 |
专业分类
电工技术 | 3806篇 |
综合类 | 3150篇 |
化学工业 | 11496篇 |
金属工艺 | 3812篇 |
机械仪表 | 2074篇 |
建筑科学 | 4605篇 |
矿业工程 | 649篇 |
能源动力 | 4097篇 |
轻工业 | 2335篇 |
水利工程 | 516篇 |
石油天然气 | 1662篇 |
武器工业 | 751篇 |
无线电 | 3535篇 |
一般工业技术 | 6663篇 |
冶金工业 | 1684篇 |
原子能技术 | 724篇 |
自动化技术 | 1003篇 |
出版年
2024年 | 264篇 |
2023年 | 882篇 |
2022年 | 1330篇 |
2021年 | 1686篇 |
2020年 | 1860篇 |
2019年 | 1643篇 |
2018年 | 1521篇 |
2017年 | 1839篇 |
2016年 | 1825篇 |
2015年 | 1862篇 |
2014年 | 2659篇 |
2013年 | 3061篇 |
2012年 | 3084篇 |
2011年 | 3194篇 |
2010年 | 2416篇 |
2009年 | 2522篇 |
2008年 | 2148篇 |
2007年 | 2754篇 |
2006年 | 2628篇 |
2005年 | 2028篇 |
2004年 | 1758篇 |
2003年 | 1414篇 |
2002年 | 1307篇 |
2001年 | 1121篇 |
2000年 | 979篇 |
1999年 | 764篇 |
1998年 | 665篇 |
1997年 | 602篇 |
1996年 | 492篇 |
1995年 | 371篇 |
1994年 | 290篇 |
1993年 | 254篇 |
1992年 | 246篇 |
1991年 | 221篇 |
1990年 | 183篇 |
1989年 | 151篇 |
1988年 | 114篇 |
1987年 | 68篇 |
1986年 | 63篇 |
1985年 | 65篇 |
1984年 | 59篇 |
1983年 | 44篇 |
1982年 | 46篇 |
1981年 | 24篇 |
1980年 | 18篇 |
1979年 | 5篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1959年 | 7篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
J. C. Jones H. Rahmati T. D. H. Do 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,54(4):317-318
Wood shaving samples were heated in both cubic baskets and in a previously described system realising the conditions of the ‘infinite slab’ in thermal ignition. Results from the two sets of experiment were found to be totally consistent with each other. 相似文献
72.
Thermal Shock Behavior of Porous Silicon Carbide Ceramics 总被引:1,自引:0,他引:1
Using the water-quenching technique, the thermal shock behavior of porous silicon carbide (SiC) ceramics was evaluated as a function of quenching temperature, quenching cycles, and specimen thickness. It is shown that the residual strength of the quenched specimens decreases gradually with increases in the quenching temperature and specimen thickness. Moreover, it was found that the fracture strength of the quenched specimens was not affected by the increase of quenching cycles. This suggests a potential advantage of porous SiC ceramics for cyclic thermal-shock applications. 相似文献
73.
The microstructure and thermal behavior of the Sn-Zn-Ag solder were investigated for 8.73–9% Zn and 0–3.0% Ag. The scanning
electron microscopy (SEM) analysis shows the Ag-Zn compound when the solder contains 0.1% Ag. X-ray diffraction (XRD) analysis
results indicate that Ag5Zn8 and AgZn3 become prominent when the Ag content is 0.3% and above. Meanwhile, the Zn-rich phase is refined, and the Zn orientations
gradually diminish upon increase in Ag content. The morphology of the Ag-Zn compound varies from nodular to dendrite structure
when the Ag content increases. The growth of the Ag-Zn compounds is accompanied by the diminishing of the eutectic structure
of the Sn-9Zn solder. Differential scanning calorimetry (DSC) investigation reveals that the solidus temperature of these
solders exists at around 198°C. A single, sharp exothermic peak was found for the solders with Ag content less than 0.5%.
Liquidus temperatures were identified with the DSC analysis to vary from 206°C to 215°C when the Ag content ranges from 1.0%
to 3.0% 相似文献
74.
Novel diols containing imide groups were prepared via condensation of aromatic dianhydrides with 5‐amino‐1‐naphthol. The diimide–dinaphthols prepared were characterized by conventional methods and used to synthesize new poly(urethane–imide)s (PUIs). All the polymers were characterized and their physical properties, such as solubility, solution viscosity, thermal stability, and thermal behaviour were studied. The polymers obtained showed more thermal stability than typical polyurethanes because of the presence of the imide groups. Copyright © 2003 Society of Chemical Industry 相似文献
75.
Addressing the potential for drop impact failure of Pb-free interconnects, the shear ductility after extensive aging of Sn-Ag-Cu
(SAC) solders has been improved radically by Co or Fe modifications. Several other SAC+X candidates (X=Mn, Ni, Ge, Ti, Si,
Cr, and Zn) now have been tested. Solder joint microstructures and shear strength results show that new SAC+X alloys also
suppress void formation and coalescence at the Cu (substrate)/Cu3Sn interface (and embrittlement) after aging at 150°C for up to 1,000 h. Microprobe measurements of 1,000 h aged samples suggest
that Cu substitution by X is usually accentuated in the intermetallic layers, consistent with X=Co and Fe results. 相似文献
76.
77.
78.
Plastisols, which are a blend of poly(vinyl chloride) resin and a plasticizer (DEHP), were used as a toughening agent of a resol resin in order to improve the mechanical properties. It was not possible to formulate resol blends by adding more than 10 % of plastisol owing to a lack of apparent homogeneity in the systems, which also showed many air bubbles. The relationship between dynamic mechanical, mechanical and thermal properties and the amount of plastisol added was studied. It was determined from the infrared spectroscopy and dynamic mechanical results that the resol–plastisol blends seem to be formed by a reaction between the phenol and PVC giving a higher crosslinked structure. An improvement in the thermal resistance of the blends at lower temperatures was observed with an increase in the percentage of plastisol. Flexural analysis showed the elastic behaviour of the systems. However, it was not possible to observe the effect of the plasticizer (DEHP) owing to the low quantity of plastisol that was added to the resol. Copyright © 2004 Society of Chemical Industry 相似文献
79.
Conducting composites of polythiophene (PTP) and polyfuran (PF) with acetylene black (AB) were prepared via chemical oxidative polymerization of thiophene and furan in a suspension of AB in CHCl3 at room temperature using anhydrous FeCl3 as the oxidant. Formation of PTP and PF and their subsequent incorporation in PTP–AB and PF–AB composite systems were confirmed by FTIR analysis. Scanning electron microscope analysis showed the presence of compact clusters of particles in both composites. Transmission electron micrographs of PTP–AB and PF–AB composites showed formation of globular polymer encapsulated AB particles with average diameters of the order of ~100 nm in both systems. Thermogravimetric analysis revealed that the overall thermal stability varied in the order: AB > PTP–AB > PTP and AB > PF–AB > PF. DC conductivity values for the PTP–AB and PF–AB composites were of the order of 10?2 and 10?3 S cm?1, respectively. Copyright © 2004 Society of Chemical Industry 相似文献
80.
董志武 《高分子材料科学与工程》1992,8(6):72-78
用TMA方法研究了双向拉伸PET膜和容器的热收缩特性,讨论了热收缩和分子结构的关系和各种影响因素。实验结果表明,TMA是研究和测试取向聚合物材料热收缩的简便有效方法。 相似文献