全文获取类型
收费全文 | 235828篇 |
免费 | 21250篇 |
国内免费 | 10885篇 |
专业分类
电工技术 | 14677篇 |
技术理论 | 21篇 |
综合类 | 15421篇 |
化学工业 | 39049篇 |
金属工艺 | 13116篇 |
机械仪表 | 14727篇 |
建筑科学 | 19893篇 |
矿业工程 | 7044篇 |
能源动力 | 6744篇 |
轻工业 | 15447篇 |
水利工程 | 4506篇 |
石油天然气 | 14338篇 |
武器工业 | 1992篇 |
无线电 | 27408篇 |
一般工业技术 | 28570篇 |
冶金工业 | 11374篇 |
原子能技术 | 2567篇 |
自动化技术 | 31069篇 |
出版年
2024年 | 1073篇 |
2023年 | 4229篇 |
2022年 | 7547篇 |
2021年 | 10428篇 |
2020年 | 7882篇 |
2019年 | 6434篇 |
2018年 | 6951篇 |
2017年 | 7972篇 |
2016年 | 7168篇 |
2015年 | 9430篇 |
2014年 | 11796篇 |
2013年 | 14024篇 |
2012年 | 15211篇 |
2011年 | 16396篇 |
2010年 | 14267篇 |
2009年 | 13420篇 |
2008年 | 13110篇 |
2007年 | 12643篇 |
2006年 | 12592篇 |
2005年 | 11117篇 |
2004年 | 7376篇 |
2003年 | 6380篇 |
2002年 | 5897篇 |
2001年 | 5328篇 |
2000年 | 5364篇 |
1999年 | 5901篇 |
1998年 | 4966篇 |
1997年 | 4132篇 |
1996年 | 3974篇 |
1995年 | 3197篇 |
1994年 | 2819篇 |
1993年 | 1983篇 |
1992年 | 1579篇 |
1991年 | 1244篇 |
1990年 | 982篇 |
1989年 | 771篇 |
1988年 | 663篇 |
1987年 | 435篇 |
1986年 | 349篇 |
1985年 | 236篇 |
1984年 | 171篇 |
1983年 | 106篇 |
1982年 | 131篇 |
1981年 | 85篇 |
1980年 | 64篇 |
1979年 | 38篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1959年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 93 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.
Wireless Networks - Geolocation is important for many emerging applications such as disaster management and recommendation system. In this paper, we propose a multilayer recognition model (MRM) to... 相似文献
3.
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
4.
Sinan Zhang Yadonga Zhao Xueshuang Yao Zhenhong Zheng Chuyao Zheng Zhuo Jiang 《International Journal of Food Science & Technology》2022,57(7):4245-4253
Ripe carambolas are hard to store and transport, while freeze-dried ones are easy to store. However, its long production time leads to higher costs. This study shows that high hydrostatic pressure (HHP) treatment could shorten the freeze-drying time of carambola slices. After HHP treatment (25–250 MPa), the drying time of the fresh sample can be shortened by 33.3–44.4% and the distribution of water and pigment in tissues is much uniform. With the increment of the pressure, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging rate are increased. At 250 MPa, the total phenolic content (TPC) increased from 11.34 to 13.36 mg GAE g−1, and the total flavonoid content (TFC) of the control sample was increased from 10.77 to 12.73 mg RE g−1. Compared with the untreated sample, HHP treatment can enhance the flavour and shorten the freeze-drying time. This work guides the application of HHP technology for drying food processing. 相似文献
5.
Ya Gu Quanmin Zhu Hassan Nouri 《International Journal of Adaptive Control and Signal Processing》2022,36(1):138-154
This article presents a state-space model with time-delay to map the relationship between known input-output data for discrete systems. For the given input-output data, a model identification algorithm combining parameter estimation and state estimation is proposed in line with the causality constraints. Consequently, this article proposes a least squares parameter estimation algorithm, and analyzes its convergence for the studied systems to prove that the parameter estimation errors converge to zero under the persistent excitation conditions. In control system design, the U-model based control is introduced to provide a unilateral platform to improve the design efficiency and generality. A simulation portfolio from modeling to control is provided with computational experiments to validate the derived results. 相似文献
6.
International Journal of Thermophysics - The addition of nanoparticles to base fuel may bring about remarkable changes in a thermodynamic process such as evaporation, due to the intensified... 相似文献
7.
Wang Chen Bao Chun-Hui Wu Wan-Yu Hsu Chia-Hsun Zhao Ming-Jie Zhang Xiao-Ying Lien Shui-Yang Zhu Wen-Zhang 《Journal of Materials Science》2022,57(26):12341-12355
Journal of Materials Science - Molybdenum oxide (MoOx) films had been grown by using plasma-enhanced atomic layer deposition (PEALD) with Mo(CO)6 precursor and O2 plasma reactant in a substrate... 相似文献
9.
Yarn-dyed fabric is often woven from warp and weft yarns in the same color depth to ensure a uniform color appearance. The difference in color depth between warp and weft tends to result in the uneven color of the yarn-dyed fabric. This article aims to establish a color tolerance for yarn-dyed fabric that can be woven with a qualified color appearance but from the warp and weft yarns in different color depths. A total of 27 yarn-dyed fabric samples in three color series (red, yellow, and blue) were evaluated by using the yarn-dyed fabric from warp and weft yarns in the same color depth of 2% (on weight of fabric, owf) as the standard. Visual assessment and instrumental measurement of color were carried out to establish the color tolerance ellipse that was defined as CMC (Color Measurement Committee) color differences (2:1) of no more than 1.00. It was found that the color strengths (K/S) and color differences (ΔECMC(2:1)) of these fabric samples for each color series had linear relationships with the color depths of warp and weft yarns. The color tolerance ellipses indicated that, even though the warp and weft yarns had an apparent color difference, they could be woven in fabrics with relatively uniform color appearance and meet the requirements for yarn-dyed fabric. This work provided valuable insight into the production of qualified yarn-dyed fabrics from unqualified dyed yarns. 相似文献
10.
Multimedia Tools and Applications - In geometry-based point cloud compression, the geometry information is typically compressed using octree coding. In octree coding, the size of the blocks in the... 相似文献