全文获取类型
收费全文 | 168231篇 |
免费 | 16940篇 |
国内免费 | 10136篇 |
专业分类
电工技术 | 11917篇 |
技术理论 | 9篇 |
综合类 | 13590篇 |
化学工业 | 25883篇 |
金属工艺 | 9958篇 |
机械仪表 | 11102篇 |
建筑科学 | 12788篇 |
矿业工程 | 4398篇 |
能源动力 | 4433篇 |
轻工业 | 16389篇 |
水利工程 | 3872篇 |
石油天然气 | 7254篇 |
武器工业 | 1715篇 |
无线电 | 19896篇 |
一般工业技术 | 18786篇 |
冶金工业 | 6425篇 |
原子能技术 | 2028篇 |
自动化技术 | 24864篇 |
出版年
2024年 | 649篇 |
2023年 | 2512篇 |
2022年 | 5019篇 |
2021年 | 6956篇 |
2020年 | 5149篇 |
2019年 | 4324篇 |
2018年 | 4800篇 |
2017年 | 5269篇 |
2016年 | 5058篇 |
2015年 | 7307篇 |
2014年 | 8986篇 |
2013年 | 10907篇 |
2012年 | 12513篇 |
2011年 | 13734篇 |
2010年 | 12444篇 |
2009年 | 11781篇 |
2008年 | 11780篇 |
2007年 | 10879篇 |
2006年 | 10073篇 |
2005年 | 8335篇 |
2004年 | 6071篇 |
2003年 | 5150篇 |
2002年 | 5267篇 |
2001年 | 4430篇 |
2000年 | 3384篇 |
1999年 | 2665篇 |
1998年 | 1864篇 |
1997年 | 1563篇 |
1996年 | 1339篇 |
1995年 | 1143篇 |
1994年 | 932篇 |
1993年 | 724篇 |
1992年 | 515篇 |
1991年 | 440篇 |
1990年 | 319篇 |
1989年 | 240篇 |
1988年 | 184篇 |
1987年 | 121篇 |
1986年 | 101篇 |
1985年 | 60篇 |
1984年 | 47篇 |
1983年 | 27篇 |
1982年 | 42篇 |
1981年 | 31篇 |
1980年 | 43篇 |
1979年 | 24篇 |
1977年 | 12篇 |
1976年 | 25篇 |
1975年 | 18篇 |
1959年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 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
2.
Xiao Zhu Chen Yanxun Jiang Hongbo Hu Zhenzhen Lui John C. S. Min Geyong Dustdar Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of... 相似文献
3.
采用直流磁控溅射和后退火氧化工艺在p型GaAs单晶衬底上成功制备了n-VO_2/pGaAs异质结,研究了不同退火温度和退火时间对VO_2/GaAs异质结性能的影响,并分析其结晶取向、化学组分、膜层质量以及光电特性。结果表明,在退火时间2 h和退火温度693 K下能得到相变性能最佳的VO_2薄膜,相变前后电阻变化约2个数量级。VO_2/GaAs异质结在308 K、318 K和328 K温度下具有较好的整流特性,对应温度下的阈值跳变电压分别为6.9 V、6.6 V和6.2 V,该结果为基于VO_2相变特性的异质结光电器件的设计与应用提供了可行性。 相似文献
6.
7.
Hong Sae Jin Park Nam Il Hwang Dae Keun Yi Tae Gyu Eum Hyang Lan 《Food science and biotechnology》2022,31(6):669-679
Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex... 相似文献
8.
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
9.
Yixuan ZHOU Huajie WANG Yi YU Yihang CHEN Rui KE Min XU Chijie XIAO Zhanhui WANG Jiquan LI Xuru DUAN Minyou YE 《等离子体科学和技术》2021,23(7):75105-52
In this article, we present the optical design of a novel diagnostic on the HL-2 A tokamak, i.e. the20-channel edge Lyman-alpha beam emission spectroscopy, which is a promising solution for edge density turbulence research on tokamaks, as it offers the possibility of density fluctuation measurement with a 3.3 mm spatial resolution while maintains a high temporal resolution of1 μs. The optical path, including the reflective collection optics, the high-dispersion spectrometer, and the linear detector array, is carefully optimized to obtain a good image quality and a high throughput. The maximum root mean square radius of the collection optics is 64 μm.The detected photon flux is estimated to be about 10~(11) photons/s/channel. 相似文献
10.