全文获取类型
收费全文 | 1531篇 |
免费 | 136篇 |
国内免费 | 55篇 |
专业分类
电工技术 | 79篇 |
综合类 | 143篇 |
化学工业 | 297篇 |
金属工艺 | 75篇 |
机械仪表 | 53篇 |
建筑科学 | 149篇 |
矿业工程 | 33篇 |
能源动力 | 68篇 |
轻工业 | 100篇 |
水利工程 | 34篇 |
石油天然气 | 92篇 |
武器工业 | 12篇 |
无线电 | 220篇 |
一般工业技术 | 145篇 |
冶金工业 | 38篇 |
原子能技术 | 22篇 |
自动化技术 | 162篇 |
出版年
2024年 | 3篇 |
2023年 | 11篇 |
2022年 | 43篇 |
2021年 | 47篇 |
2020年 | 44篇 |
2019年 | 36篇 |
2018年 | 25篇 |
2017年 | 33篇 |
2016年 | 28篇 |
2015年 | 39篇 |
2014年 | 55篇 |
2013年 | 82篇 |
2012年 | 83篇 |
2011年 | 71篇 |
2010年 | 80篇 |
2009年 | 95篇 |
2008年 | 114篇 |
2007年 | 94篇 |
2006年 | 94篇 |
2005年 | 55篇 |
2004年 | 53篇 |
2003年 | 69篇 |
2002年 | 98篇 |
2001年 | 97篇 |
2000年 | 65篇 |
1999年 | 43篇 |
1998年 | 34篇 |
1997年 | 23篇 |
1996年 | 13篇 |
1995年 | 24篇 |
1994年 | 18篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有1722条查询结果,搜索用时 0 毫秒
61.
62.
63.
Ji Zou Shui‐Gen Huang Kim Vanmeensel Guo‐Jun Zhang Jef Vleugels Omer Van der Biest 《Journal of the American Ceramic Society》2013,96(4):1055-1059
A carbide boronizing method was first developed to produce dense boron carbide‐ zirconium diboride (“B4C”–ZrB2) composites from zirconium carbide (ZrC) and amorphous boron powders (B) by Spark Plasma Sintering at 1800°C–2000°C. The stoichiometry of “B4C” could be tailored by changing initial boron content, which also has an influence on the processing. The self‐propagating high‐temperature synthesis could be ignited by 1 mol ZrC and 6 mol B at around 1240°C, whereas it was suppressed at a level of 10 mol B. B8C–ZrB2 ceramics sintered at 1800°C with 1 mole ZrC and 10 mole B exhibited super high hardness (40.36 GPa at 2.94 N and 33.4 GPa at 9.8 N). The primary reason for the unusual high hardness of B8C–ZrB2 ceramics was considered to be the formation of nano‐sized ZrB2 grains. 相似文献
64.
65.
Carbon black, graphite and carbon fibre were employed to design and prepare electrically conductive asphalt mixtures containing single filler or mixed fillers of conductive powder plus carbon fibre. The effects of filler type, filler content and mixed fillers on the resistivity of asphalt concrete were investigated. Experimental results showed that the insulating-conductive percolation transition of the resistivity under the function of filler content appears in the single-filler composites and the percolation threshold is approximately 12%, 10%, and 5% by volume percentage of the binder phase for carbon black, graphite and carbon fibre respectively. The combination function of mixed fillers has appreciable advantages over single powder filler, but no obvious advantages over simple fiber in the conductivity improvement at the same total filler content. But the addition of small amounts of expensive fibers to larger amounts of cheaper CB or graphite can be a cost effective system. Scanning electron microscope images provide insight into the mechanisms of conductivity enhancement for mixed fillers. Conductive filler particles exhibit the short-range contacts or connections in asphalt concrete, whereas carbon fibres exhibit a long-range conductive bridging effect and short-circuit effect because of the high aspect ratio. 相似文献
66.
采用熔融共混工艺和熔融浸渍分别制备了短玻璃纤维增强聚苯硫醚复合材料(PPS/SGF)和长玻璃纤维增强聚苯硫醚(PPS/LGF)复合材料,并对复合材料的力学性能和耐热性能进行了对比分析。研究结果表明,在玻璃纤维质量分数为30%时,PPS/SGF和PPS/LGF复合材料的拉伸强度分别为110 MPa和122 MPa;弯曲强度分别为175 MPa和208 MPa;弯曲弹性模量分别为8 GPa和9 GPa;缺口冲击强度和无缺口冲击强度分别为7.7,11.9 kJ/m2和31,37 kJ/m2。PPS/LGF复合材料的拉伸强度、弯曲强度、弯曲弹性模量、缺口冲击强度和无缺口冲击强度相较于PPS/SGF复合材料分别提高了11.0%,18.9%,11.3%,54.5%和19.4%。PPS/SGF和PPS/LGF复合材料的热变形温度分别达到250℃和275℃,PPS/LGF复合材料的热变形温度高于PPS/SGF复合材料热变形温度10%。 相似文献
67.
Qingliang Shan Qian Ma Jiawei Lian Caiyu Yao Anze Shui 《International Journal of Applied Ceramic Technology》2022,19(5):2675-2685
In this research, for studying the influence of size and heat treatment temperature of initial Al(OH)3 on the physical properties of porous mullite ceramics, porous mullite ceramics were prepared by in situ reaction sintering of amorphous silica and treated Al(OH)3. The transition phases χ-Al2O3, к-Al2O3, and stable phase α-Al2O3 can be obtained in turn when the treatment temperature of raw Al(OH)3 is 500, 1000, and 1500°C, respectively. The coarser the raw Al(OH)3, the higher the strength of porous mullite ceramics. When the sintering temperature is 1500°C, the bending strengths of PS500-C, PS1000-C, and PS1500-C (PSx-C represents that the specimen was prepared by the coarse grade Al(OH)3, which was previously treated at x°C) are 40.3 ± 2.1, 54.9 ± 5.2, and 64.8 ± 4.8 MPa, respectively. In addition, although the activated Al2O3 can decrease the formation temperature (∼100°C) of porous mullite ceramics, the strength and density of porous mullite ceramics prepared by activated Al2O3 will decrease at the same sintering temperature. It is believed that the increase of defects and pores during the phase transformation should be responsible for this phenomenon. 相似文献
68.
Junjie Qian Bin Du Chao He Mei Cai Xinrong Zhong Hao Xiong Shenghui Zeng Anze Shui 《Journal of the American Ceramic Society》2022,105(5):3456-3468
The hierarchical SiOC/SiCnws/CF composites (A/B/C structure) were designed via precursor infiltration and pyrolysis process. The SiOC ceramics served as the wave-transparent characteristic materials to adjust the impedance matching. Herein, the in situ growth of SiCnws not only was used for the absorber but served as the reinforcement of SiOC matrix composites. In detail, the SiOC/SiCnws/CF-1200°C-2 exhibits excellent electromagnetic absorption performance with minimum reflection loss of −46 dB at 14.4 GHz with the thickness of 1.6 mm, and its effective absorption band reaches 4.3 GHz. Its compressive strength reaches 8.69 and 16.41 MPa in z and x/y directions, separately. This contribution has a guidance for the application of carbon fiber/ceramics matrix composites in harsh environment. 相似文献
69.
本文用煤岩学方法研究离心法净化煤焦油沥青中间相的热转化过程,考察与评价了离心处理条件、原生与次生喹啉不溶物组成等对中间相热转化的影响。 相似文献
70.
对低压电器螺钉连接的强度进行了理论分析和探讨。得出螺钉连接的可靠性设计数据,对金属薄板件小螺纹孔翻边成形的设计提出了设计依据和数值。 相似文献