全文获取类型
收费全文 | 5024篇 |
免费 | 520篇 |
国内免费 | 242篇 |
专业分类
电工技术 | 361篇 |
综合类 | 290篇 |
化学工业 | 1015篇 |
金属工艺 | 294篇 |
机械仪表 | 300篇 |
建筑科学 | 419篇 |
矿业工程 | 152篇 |
能源动力 | 134篇 |
轻工业 | 315篇 |
水利工程 | 100篇 |
石油天然气 | 359篇 |
武器工业 | 33篇 |
无线电 | 559篇 |
一般工业技术 | 595篇 |
冶金工业 | 253篇 |
原子能技术 | 40篇 |
自动化技术 | 567篇 |
出版年
2024年 | 33篇 |
2023年 | 89篇 |
2022年 | 196篇 |
2021年 | 251篇 |
2020年 | 211篇 |
2019年 | 162篇 |
2018年 | 154篇 |
2017年 | 153篇 |
2016年 | 159篇 |
2015年 | 224篇 |
2014年 | 265篇 |
2013年 | 305篇 |
2012年 | 297篇 |
2011年 | 315篇 |
2010年 | 258篇 |
2009年 | 242篇 |
2008年 | 239篇 |
2007年 | 261篇 |
2006年 | 284篇 |
2005年 | 254篇 |
2004年 | 164篇 |
2003年 | 141篇 |
2002年 | 139篇 |
2001年 | 127篇 |
2000年 | 150篇 |
1999年 | 132篇 |
1998年 | 94篇 |
1997年 | 94篇 |
1996年 | 73篇 |
1995年 | 69篇 |
1994年 | 61篇 |
1993年 | 40篇 |
1992年 | 27篇 |
1991年 | 23篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有5786条查询结果,搜索用时 15 毫秒
1.
Sheng Mingming Yang Rongkun Gong Hongyu Zhang Yujun Lin Xiao Jing Jie 《Journal of Materials Science》2022,57(10):5805-5824
Journal of Materials Science - With the extensive use of high-power electronic appliances, polymer-based thermal insulation composites with excellent thermal properties are utilized in the field of... 相似文献
2.
The Fe/C/SiCN composite ceramics were synthesized by polymer-derived method to obtain the integration of structure and functions. The electromagnetic waves (EMW) absorption properties at X and Ku bands were investigated. The addition of nano-sized Fe particles improved the magnetic loss and impedance matching, and the carbon nanotubes generated by the iron in-situ catalysis increased the internal relaxation polarization and interfacial polarization, which together improved the EMW absorption properties significantly. In particular, the Fe/C/SiCN-9 showed the optimum reflection loss (RL) of ?31.06 dB at 10.03 GHz with an effective absorption bandwidth (EAB, RL < ?10 dB) of 3.03 GHz at 2.51 mm, indicating the excellent EMW absorption properties of Fe/C/SiCN composite ceramics. 相似文献
3.
某出口型号交流电力机车牵引控制系统要求变流器控制逻辑具备接触器控制、牵引系统数据交互、变流器故障保护、变流器启动自检等功能。针对以上功能,基于MATLAB中的Simulink/Stateflow可视化编程工具进行牵引控制模型的搭建,遵循模块化编程理念,采用较少的程序代码编写实现复杂的逻辑控制模型,生成逻辑清晰的控制功能流程图,进行半实物仿真测试,增强控制模型的可靠性。通过该变流器产品型式试验检验,验证变流器控制逻辑的功能可以满足控制系统的需求。 相似文献
4.
Longzhi Li Xiaowei Jiang Zhiguo Bian Jianwei Wang Fumao Wang Zhanlong Song 《Drying Technology》2019,37(2):173-185
Microwave lignite drying with assistance of biomass-derived char was addressed and effect of bio-char on drying rate and energy consumption was investigated in this work. Effective diffusion coefficient and activation energy for the drying process were also analyzed. The results indicated the drying process was largely dependent on the variation of sample temperature. Bio-char originated from pine wood was most favorable for lignite drying, considering its better promoting effect and advanced security. There existed an optimal bio-char addition ratio for drying process at different power. The corresponding optimal ratio was 10% at 231?W and 15% at 385?W, at which the biggest drying rate and the least energy consumption were reached. It was compared lignite drying initiated at 385?W was better for energy conservation. Effective diffusivity was improved and activation energy was simultaneously reduced, with the addition of bio-char. The minimum activation energy was 15.54?W?·?g?1, which was gained at bio-char addition ratio of 10%. The results revealed the effect of bio-char on depressing activation energy could rival that of metal-based additives. The drying process with assistance of microwave and bio-char could present technical and economical benefits on lignite upgrading. 相似文献
5.
Yu Zhang Xiaofei Dai Haonan Jin Chaoxin Man Yujun Jiang 《Journal of dairy science》2021,104(4):4023-4032
This study aimed to predict the optimal carbon source for higher production of exopolysaccharides (EPS) by Lactobacillus paracasei TD 062, and to evaluate the effect of this carbon source on the production and monosaccharide composition of EPS. We evaluated the EPS production capacity of 20 strains of L. paracasei under the same conditions. We further investigated L. paracasei TD 062, which showed the highest EPS-producing activity (0.609 g/L), by examining the associated biosynthesis pathways for EPS. Genomics revealed that fructose, mannose, trehalose, glucose, galactose, and lactose were carbon sources that L. paracasei TD 062 could use to produce EPS. We identified an EPS synthesis gene cluster that could participate in transport, export, and sugar chain synthesis, and generate 6 sugar nucleotides. Experimental results showed that the sugar content of the EPS produced using fermentation with the optimized carbon source (fructose, mannose, trehalose, glucose, galactose, and lactose) increased by 115%. Furthermore, use of the optimized carbon source changed the monosaccharide content of the associated EPS. The results of enzyme activity measurements showed significant increases in the activity of 2 key enzymes involved in the glycoside synthesis pathway. Our study revealed that optimizing the carbon source provided for fermentation not only increased the production of EPS, but also affected the composition of the monosaccharides by increasing enzyme activity in the underlying synthesis pathways, suggesting an important role for carbon source in the production of EPS by L. paracasei TD 062. 相似文献
6.
7.
8.
10.