全文获取类型
收费全文 | 13066篇 |
免费 | 1069篇 |
国内免费 | 241篇 |
专业分类
电工技术 | 766篇 |
技术理论 | 1篇 |
综合类 | 1110篇 |
化学工业 | 4447篇 |
金属工艺 | 174篇 |
机械仪表 | 225篇 |
建筑科学 | 1751篇 |
矿业工程 | 2083篇 |
能源动力 | 1183篇 |
轻工业 | 261篇 |
水利工程 | 249篇 |
石油天然气 | 414篇 |
武器工业 | 8篇 |
无线电 | 102篇 |
一般工业技术 | 748篇 |
冶金工业 | 506篇 |
原子能技术 | 71篇 |
自动化技术 | 277篇 |
出版年
2024年 | 17篇 |
2023年 | 125篇 |
2022年 | 302篇 |
2021年 | 404篇 |
2020年 | 449篇 |
2019年 | 329篇 |
2018年 | 338篇 |
2017年 | 345篇 |
2016年 | 413篇 |
2015年 | 421篇 |
2014年 | 737篇 |
2013年 | 655篇 |
2012年 | 832篇 |
2011年 | 1014篇 |
2010年 | 762篇 |
2009年 | 806篇 |
2008年 | 640篇 |
2007年 | 888篇 |
2006年 | 784篇 |
2005年 | 688篇 |
2004年 | 595篇 |
2003年 | 547篇 |
2002年 | 447篇 |
2001年 | 302篇 |
2000年 | 282篇 |
1999年 | 259篇 |
1998年 | 186篇 |
1997年 | 177篇 |
1996年 | 107篇 |
1995年 | 92篇 |
1994年 | 89篇 |
1993年 | 51篇 |
1992年 | 41篇 |
1991年 | 33篇 |
1990年 | 31篇 |
1989年 | 25篇 |
1988年 | 24篇 |
1987年 | 29篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1975年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Shilin Du Yichen Dong Feiqiang Guo Beile Tian Songbo Mao Lin Qian Chengyun Xin 《International Journal of Hydrogen Energy》2021,46(27):14138-14147
The potential of using high metals containing coal gangue and lignite to prepare high-activity coal char-based catalysts is investigated for effective biomass tar decomposition. Loose structure and rough surface are formed for these char-based catalysts with heterogeneous distribution of a large number of inorganic particles. In the biomass tar decomposition, the performance of the coal char-based catalysts is significantly influenced by the content of the metals in the raw materials and coal gangue char (GC) with the ash content as high as 50.80% exhibits the highest activity in this work. A high biomass tar conversion efficiency of 93.5% is achieved at 800 °C along with a significant increase in the fuel gas product. During the five-time consecutive tests, the catalytic performance of GC increases a little at the second or third times reuse and remains relatively stable, showing the remarkable stability of the catalyst in biomass tar decomposition applications. 相似文献
2.
Abdulrahman S. Albidah 《Ceramics International》2021,47(11):14923-14943
The growth of demand for concrete raises concerns about the consumption of natural resources and ordinary Portland cement. Geopolymer composites show promise as a sustainable alternative for conventional cement concrete. Considering the wide range of potential geopolymer composites applications (including suitability for transportation infrastructure, underwater applications, repair and rehabilitation of structures as well as recent developments in 3D printing), the desired fresh and mechanical properties of the geopolymer composite may vary between applications: for example, rapid setting can be a merit for certain applications and a demerit for others. Therefore, the desired fresh and mechanical properties (e.g., workability, setting time, compressive strength, etc.) can be controlled for a given geopolymer source material through its partial substitution by natural or by-product materials. Recognizing the critical role of various replacement materials in enhancing the potential applications of geopolymer composites, the present review was undertaken to quantify and understand the effect of partial replacement by fly ash, metakaolin, kaolin, red mud, slag, ordinary Portland cement, and silica fume on the setting time, workability, compressive strength and flexural strength of various source materials addressed in the literature. The review also provides insights into research gaps in the field to promote future research. 相似文献
3.
This paper reports an assessment of the performance of concrete based on a calcium sulfoaluminate–anhydrite–fly ash cement combination. Concretes were prepared at three different w/c ratios and the properties were compared to those of Portland cement and blast-furnace cement concretes. The assessment involved determination of mechanical and durability properties. The results suggest that an advantageous synergistic effect between and ettringite and fly ash (Ioannou et al., 2014) was reflected in the concrete’s low water absorption rates, high sulfate resistance, and low chloride diffusion coefficients. However, carbonation depths, considering the dense ettringite-rich microstructure developed, were higher than those observed in Portland cement concretes at a given w/c ratio. It was concluded that the amount of alkali hydroxides present in the pore solution is as important factor as the w/c ratio when performance of this type of concrete is addressed. 相似文献
4.
Chaoxin Li Yi Zhou Yuming Tian Yuanyuan Zhao Kaiyue Wang Guomin Li Yuesheng Chai 《Ceramics International》2019,45(5):5613-5616
Ceramics with mullite whiskers were prepared from coal fly ash and Al2O3 raw materials, with AlF3 used as an additive. The phase structures and microstructures of the ceramics were identified via X-ray diffraction and scanning electron microscopy, respectively. The results show that pickling of coal fly ash is an effective method for enhancing the flexural strength of ceramics. Sintering temperature and AlF3 addition were also key factors influencing the creation of ideal ceramics. The ceramic made from pickled coal fly ash, 6?wt% AlF3, and sintered at 1200?°C, exhibited the highest flexural strength of 59.1?MPa, and had a bulk density of 1.32?g/cm3 and porosity of 26.8%. The results show that ceramic materials made under these conditions are ideal candidates for manufacturing ceramic proppants for the exploitation of unconventional oil and gas resources. 相似文献
5.
6.
7.
采用轴向式气胎离合、制动器,改造了旧飞剪,解决了原剪机电磁离合、制动器控制不准确的问题;该剪机改造后在成品轧机后使用,剪切用120mm×120mm坯生产的大规格产品(18mm以上),增产、增效,年总经济效益为97.8万元 相似文献
8.
һ����ӱ����˹����ȼ����ȼ�Զ���Ͽ���װ�� 总被引:1,自引:0,他引:1
我国是煤资源大国,长期来在采煤的同时,抽放排空大量煤层瓦斯,不仅浪费大量资源,还严重污染大气。利用煤层瓦斯发电是解决煤层瓦斯放空的重要途径 。文章介绍一种全新的有别于传统 发动机的瓦斯内燃机空燃自动混合控制装置,其中包括:煤层瓦斯的理化特性、装置的结构、工作原理及工作过程,阐述了结构参数对发动机性能的影响。经过在中心瓦斯工区内燃发动机组群上安装试运行,结果表明:该装置可以适用于高、中、低不同浓度的煤层瓦斯,性能稳定、可靠,达到了设计性能指标,完全满足燃气,内燃机组的使用要求,并取得了很好的经济效益、生态效益和环保效益。 相似文献
9.
10.