全文获取类型
收费全文 | 152896篇 |
免费 | 14434篇 |
国内免费 | 8201篇 |
专业分类
电工技术 | 10660篇 |
技术理论 | 6篇 |
综合类 | 11258篇 |
化学工业 | 22964篇 |
金属工艺 | 8838篇 |
机械仪表 | 9290篇 |
建筑科学 | 11640篇 |
矿业工程 | 3741篇 |
能源动力 | 4319篇 |
轻工业 | 14304篇 |
水利工程 | 3383篇 |
石油天然气 | 6658篇 |
武器工业 | 1444篇 |
无线电 | 18981篇 |
一般工业技术 | 17594篇 |
冶金工业 | 7010篇 |
原子能技术 | 1740篇 |
自动化技术 | 21701篇 |
出版年
2024年 | 691篇 |
2023年 | 2383篇 |
2022年 | 4717篇 |
2021年 | 6284篇 |
2020年 | 4578篇 |
2019年 | 3690篇 |
2018年 | 4199篇 |
2017年 | 4889篇 |
2016年 | 4387篇 |
2015年 | 6280篇 |
2014年 | 7954篇 |
2013年 | 9821篇 |
2012年 | 11029篇 |
2011年 | 12120篇 |
2010年 | 10728篇 |
2009年 | 10283篇 |
2008年 | 10311篇 |
2007年 | 9650篇 |
2006年 | 8931篇 |
2005年 | 7217篇 |
2004年 | 5048篇 |
2003年 | 4178篇 |
2002年 | 4126篇 |
2001年 | 3505篇 |
2000年 | 2954篇 |
1999年 | 2672篇 |
1998年 | 2284篇 |
1997年 | 1950篇 |
1996年 | 1701篇 |
1995年 | 1438篇 |
1994年 | 1100篇 |
1993年 | 894篇 |
1992年 | 692篇 |
1991年 | 555篇 |
1990年 | 458篇 |
1989年 | 337篇 |
1988年 | 275篇 |
1987年 | 201篇 |
1986年 | 173篇 |
1985年 | 147篇 |
1984年 | 109篇 |
1983年 | 79篇 |
1982年 | 72篇 |
1981年 | 69篇 |
1980年 | 71篇 |
1979年 | 40篇 |
1978年 | 32篇 |
1977年 | 34篇 |
1976年 | 58篇 |
1973年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Pengfei Liang Jie Zhu Di Wu Hui Peng Xiaolian Chao Zupei Yang 《Journal of the American Ceramic Society》2021,104(6):2702-2710
Due to the demand of miniaturization and integration for ceramic capacitors in electronic components market, TiO2-based ceramics with colossal permittivity has become a research hotspot in recent years. In this work, we report that Ag+/Nb5+ co-doped (Ag1/4Nb3/4)xTi1−xO2 (ANTOx) ceramics with colossal permittivity over a wide frequency and temperature range were successfully prepared by a traditional solid–state method. Notably, compositions of ANTO0.005 and ANTO0.01 respectively exhibit both low dielectric loss (0.040 and 0.050 at 1 kHz), high dielectric permittivity (9.2 × 103 and 1.6 × 104 at 1 kHz), and good thermal stability, which satisfy the requirements for the temperature range of application of X9R and X8R ceramic capacitors, respectively. The origin of the dielectric behavior was attributed to five dielectric relaxation phenomena, i.e., localized carriers' hopping, electron–pinned defect–dipoles, interfacial polarization, and oxygen vacancies ionization and diffusion, as suggested by dielectric temperature spectra and valence state analysis via XPS; wherein, electron-pinned defect–dipoles and internal barrier layer capacitance are believed to be the main causes for the giant dielectric permittivity in ANTOx ceramics. 相似文献
4.
Applied Composite Materials - In this paper, the low-velocity impact deformation behavior of biaxial warp-knitted flexible composite was investigated. A simplified finite element model (FEM) of the... 相似文献
5.
Hui Liu Yaohui Fu Jinhai Yuan Lei Yu Zhefei Wang Quan Liu Bo Wei Xuhong Wang 《Ceramics International》2021,47(12):16570-16578
To provide a basis for the high-temperature oxidation of ultra-high temperature ceramics (UHTCs), the oxidation behavior of Zr3[Al(Si)]4C6 and a novel Zr3[Al(Si)]4C6-ZrB2-SiC composite at 1500 °C were investigated for the first time. From the calculation results, the oxidation kinetics of the two specimens follow the oxidation dynamic parabolic law. Zr3[Al(Si)]4C6 exhibited a thinner oxide scale and lower oxidation rate than those of the composite under the same conditions. The oxide scale of Zr3[Al(Si)]4C6 exhibited a two-layer structure, while that of the composite exhibited a three-layer structure. Owing to the volatilization of B2O3 and the active oxidation of SiC, a porous oxide layer formed in the oxide scale of the composite, resulting in the degradation of its oxidation performance. Furthermore, the cracks and defects in the oxide scale of the composite indicate that the reliability of the oxide scale was poor. The results support the service temperature of the obtained ceramics. 相似文献
6.
7.
盾构隧道施工物料无人运输有助于提升运输效率、降低运输成本、减少运输安全事故率。与公路汽车无人驾驶、港口车辆无人驾驶、轨道交通无人驾驶等逐步成熟的无人驾驶技术不同,在隧道场景下实施施工物料无人运输存在运输物料种类繁多、运输调度困难、地下定位信号拒止、狭窄车道频繁会车、行车路面工况复杂、地上地下联动响应慢等诸多挑战。从实现盾构隧道施工物料无人运输的关键问题分析入手,综述当前盾构隧道施工物料运输方式、运输需求、无人运输发展现状及存在的挑战,提出盾构隧道施工物料无人运输的五大关键技术:多种类物料智能货控能效管理技术,无人化垂直装卸门机控制技术,多传感器融合同步定位与地图构建技术,隧道复杂环境路径规划与自主避障技术,隧-地一体化联动响应的高可靠性无线通信技术。 相似文献
8.
Tao Feng Mingde Tong Shuotian Yao Hejun Li Shifeng Wen Hongjiao Lin 《Journal of the European Ceramic Society》2021,41(1):158-166
Composites based on hafnium carbide and reinforced with continuous naked carbon fiber with and without PyC interface were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. The microstructure, mechanical property, cyclic ablation and fiber bundle push-in tests of the composites were investigated. The results show that after three times ablation cycles, the bending strength of samples without PyC interface decreased by 63.6 %; the bending strength of samples with PyC interface only decreased by 37.8 %. The force displacement curve of the samples with PyC interface presented a well pseudoplastic deformation state. The mechanical behavior difference of two kinds of composites was due to crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface. 相似文献
9.
Da-Wang Tan Zhen-Yong Lao Zhan Zhang Wei-Ming Guo Shi-Kuan Sun Hua-Tay Lin 《Journal of the American Ceramic Society》2021,104(6):2860-2867
B4C-TiB2 ceramics (TiB2 ranging 5~70 vol%) with Mo-Co-WC as the sintering additive were prepared by spark plasma sintering. In comparison with B4C-TiB2 without additive, the enhanced densification was evident in the sintered specimen with Mo-Co-WC additive. Core-rim structured grain was observed around TiB2 grains. The interface of the rim between TiB2 and B4C phases demonstrated different feature: the inner borderline of the rim exhibited a smooth feature, whereas a sharp curved grain boundary was observed between the rim and the B4C grain. The formation mechanism is discussed: the epitaxial growth of (Ti,Mo,W)B2 rim around the TiB2 core may occur as a result of the solid solution and dissolution-precipitation between TiB2 phase and the sintering additive. It was revealed that the fracture toughness increased as the content of TiB2 content increased, alongside the decreased hardness. B4C-30 vol% TiB2 specimen demonstrated the optimal combination of mechanical properties, reaching Vickers hardness of 24.3 GPa and fracture toughness of 3.33 MPa·m1/2. 相似文献
10.
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