全文获取类型
收费全文 | 49117篇 |
免费 | 4459篇 |
国内免费 | 2448篇 |
专业分类
电工技术 | 3262篇 |
综合类 | 3464篇 |
化学工业 | 12351篇 |
金属工艺 | 8027篇 |
机械仪表 | 2172篇 |
建筑科学 | 4556篇 |
矿业工程 | 1497篇 |
能源动力 | 1524篇 |
轻工业 | 4314篇 |
水利工程 | 1048篇 |
石油天然气 | 1984篇 |
武器工业 | 495篇 |
无线电 | 2602篇 |
一般工业技术 | 5166篇 |
冶金工业 | 2152篇 |
原子能技术 | 315篇 |
自动化技术 | 1095篇 |
出版年
2024年 | 212篇 |
2023年 | 841篇 |
2022年 | 1611篇 |
2021年 | 2003篇 |
2020年 | 1702篇 |
2019年 | 1353篇 |
2018年 | 1280篇 |
2017年 | 1799篇 |
2016年 | 1713篇 |
2015年 | 1731篇 |
2014年 | 2478篇 |
2013年 | 2611篇 |
2012年 | 3265篇 |
2011年 | 3635篇 |
2010年 | 2588篇 |
2009年 | 2954篇 |
2008年 | 2425篇 |
2007年 | 3027篇 |
2006年 | 3038篇 |
2005年 | 2575篇 |
2004年 | 2143篇 |
2003年 | 1825篇 |
2002年 | 1540篇 |
2001年 | 1364篇 |
2000年 | 1159篇 |
1999年 | 998篇 |
1998年 | 795篇 |
1997年 | 681篇 |
1996年 | 510篇 |
1995年 | 486篇 |
1994年 | 402篇 |
1993年 | 265篇 |
1992年 | 248篇 |
1991年 | 174篇 |
1990年 | 128篇 |
1989年 | 118篇 |
1988年 | 71篇 |
1987年 | 54篇 |
1986年 | 30篇 |
1985年 | 26篇 |
1984年 | 24篇 |
1983年 | 23篇 |
1982年 | 25篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1974年 | 6篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Antonio Vinci Luca Zoli Diletta Sciti 《Journal of the European Ceramic Society》2018,38(11):3767-3776
The microstructure and the oxidation resistance in air of continuous carbon fibre reinforced ZrB2–SiC ceramic composites were investigated. SiC content was varied between 5–20?vol.%, while maintaining fibre content at ~40?vol.%. Short term oxidation tests in air were carried out at 1500 and 1650?°C in a bottom-up loading furnace. The thickness, composition and microstructure of the resulting oxide scale were analysed by SEM-EDS and X-Ray diffraction. The results show that contents above 15?vol.% SiC ensure the formation of a homogeneous protective borosilicate glass that covers the entire sample and minimizes fibre burnout. The scale thickness is ~90?μm for the sample containing 5?vol.% SiC and decreases with increasing SiC content. 相似文献
33.
ABSTRACTImproving the hydration resistance of CaO particle in manufacturing and application of free CaO-containing materials has practical significance. In this study, CaO granules was made from Ca(OH)2 particles, which were fabricated by the granulation method. The results showed that the hydration resistance of the CaO granules which was prepared under 1700?r?min?1 was the best, the CaO granules was sintered well in calcination process, the shell of CaO granules was relatively dense, which improves the hydration resistance of CaO granules, and the rate of hydration weight increment was 0.58% after placed in the air for 20 days under a temperature of 10–14°C and a relative humidity of 57–81%. 相似文献
34.
Clay polyurethane nanocomposite (CPN) coating films were fabricated by uniformly dispersing nanoclay, organically modified with 25–30 wt.% octadecylamine in varying concentrations up to 5 wt.%, in a commercial two component, glossy, acrylic aliphatic polyurethane using ultrasonication. Organo-modified nanoclay was characterized by X-ray diffraction (XRD). The dispersion of the nanoclay into the matrix was investigated by scanning electron microscopy (SEM). CPN coating films were characterized by thermogravimetric analysis (TGA), and flame retardant, corrosion resistance and mechanical properties were also investigated. The XRD measurement indicated that, the organo-modified nanoclay particles were mainly constituted of montmorillonite with traces of quartz and calcite also found to be present. The SEM analysis showed that the nanoclay layers were dispersed and intercalated into the polyurethane coating. Thermogravimetric analysis showed that incorporating 5 wt.% organo-nanoclay into polyurethane considerably enhanced the thermal stability and increased the char residue to 14.11 wt.% relative to 4.58 for the sample without organo-nanoclay (blank polyurethane). The limiting oxygen index (LOI) test revealed that incorporation of organo-nanoclay led to a further increase in LOI values, which indicate an improvement in flame retardancy properties. The corrosion resistance also improved and this improvement increases with increase nanoclay wt.%. The mechanical resistance measurements demonstrated that the gloss of the CPN coating films slightly decreased, although hardness, adhesion and impact resistance of the CPN coating films improved with the incorporation of the organo-nanoclay. 相似文献
35.
36.
37.
《Ceramics International》2020,46(15):24204-24212
The effects of in-situ synthesis columnar mullite and pore structure on the hot modulus of rupture (HMOR), thermal shock resistance and corrosion resistance of corundum castables have been investigated in this paper. When 2% nano silica was added, the pore diameters of castables could be decreased to 15 nm (at 110 °C), 1 μm (1100 °C) and 6 μm (1500 °C), respectively. The corresponding reducing magnitude of pore size is 98.5%, 83.3% and 33.3%. The HMOR of castables fired at 1500 °C increased by 110% to 3.64 MPa. Furthermore, after three thermal shock cycles, the residual strength ratio of castables increased from 5.2% to 15.3%. A large amount of cross-distributed columnar mullite was formed between nano silica and α-Al2O3 by the two-dimensional nucleation mechanism, which remarkably enhanced the high temperature properties. The penetration index reduced from 30.86% to 19.88%, suggesting that smaller pore size and higher viscosity had a great influence to the penetration process. 相似文献
38.
39.
40.
Xianghui Wang Pengda Zhao Jianwei Chen Huizhong Zhao Kai He 《Ceramics International》2018,44(11):12162-12168
Al–Cr slag is the solid waste generated by the smelting of Cr metal. It presents a range of environmental hazards. This study addressed the corrosion resistance of Al–Cr slag containing chromium–corundum refractories to slags with different basicity. Herein, we provide suggestions for the use of Cr–corundum of different basicity in kilns. Al–Cr slag, brown fused Al2O3, and chrome green were used as the raw materials, with pure calcium aluminate cement being used as a binder. The brick samples, prepared using different blends of chrome green and corundum, were fired at 1600?°C, and subsequently subjected to a slag corrosion test. After corrosion by slag of different basicity, the phase composition and microstructure of the sample were analyzed by X-ray diffraction, energy dispersive spectrometer and scanning electron microscopy. There were two major findings. First, Cr–corundum brick made from Al–Cr slag has a better slag corrosion resistance than that made from Cr2O3 and brown fused Al2O3. Second, Cr–corundum brick made from Al–Cr slag has superior corrosion resistance to slag with a CaO:SiO2 ratio of 2:1. 相似文献