全文获取类型
收费全文 | 84969篇 |
免费 | 8092篇 |
国内免费 | 4792篇 |
专业分类
电工技术 | 6219篇 |
技术理论 | 5篇 |
综合类 | 6623篇 |
化学工业 | 12284篇 |
金属工艺 | 4947篇 |
机械仪表 | 6021篇 |
建筑科学 | 7008篇 |
矿业工程 | 2639篇 |
能源动力 | 2649篇 |
轻工业 | 4748篇 |
水利工程 | 1874篇 |
石油天然气 | 5065篇 |
武器工业 | 885篇 |
无线电 | 9801篇 |
一般工业技术 | 9256篇 |
冶金工业 | 3842篇 |
原子能技术 | 1065篇 |
自动化技术 | 12922篇 |
出版年
2024年 | 326篇 |
2023年 | 1146篇 |
2022年 | 2227篇 |
2021年 | 3172篇 |
2020年 | 2389篇 |
2019年 | 1985篇 |
2018年 | 2277篇 |
2017年 | 2582篇 |
2016年 | 2317篇 |
2015年 | 3244篇 |
2014年 | 4372篇 |
2013年 | 5111篇 |
2012年 | 5797篇 |
2011年 | 6288篇 |
2010年 | 5670篇 |
2009年 | 5336篇 |
2008年 | 5497篇 |
2007年 | 5311篇 |
2006年 | 5170篇 |
2005年 | 4388篇 |
2004年 | 3227篇 |
2003年 | 2950篇 |
2002年 | 3079篇 |
2001年 | 2651篇 |
2000年 | 2139篇 |
1999年 | 1959篇 |
1998年 | 1357篇 |
1997年 | 1127篇 |
1996年 | 1103篇 |
1995年 | 819篇 |
1994年 | 717篇 |
1993年 | 524篇 |
1992年 | 390篇 |
1991年 | 273篇 |
1990年 | 216篇 |
1989年 | 196篇 |
1988年 | 174篇 |
1987年 | 106篇 |
1986年 | 64篇 |
1985年 | 41篇 |
1984年 | 31篇 |
1983年 | 22篇 |
1982年 | 25篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1976年 | 1篇 |
1971年 | 2篇 |
1959年 | 2篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Xin Li Yurui Wang Minxuan Xu Yueqin Shi Hemiao Wang Xin Yang Haoting Ying Qi Zhang 《应用聚合物科学杂志》2021,138(19):50406
Polymer electrets have revealed great potential application in electromechanical devices because of the low weight, large quasi-piezoelectric sensitivity, and excellent flexibility. For an electret, a permanent and macroscopic electric field exists on the surface, principally led by a macroscopic electrostatic charge on the surface or a net orientation of polar groups inside the object. Here, progress in the development of polymer electrets is reviewed. After a brief retrospect of the research courses and those typical polymer electrets that are classified into fluorine polymer and nonfluorine polymer, we present a survey on the charging methods, including corona, soft X-ray, contact, thermal and monoenergetic particle beams. The latest representative applications (i.e., power harvesting, sensors, field effect transistors, and biomedicine) based on polymer electrets are also summarized. Finally, we complete this review with a discussion on perspectives and challenges in this field. 相似文献
2.
低轨互联网星座是当前全球研究和发展的热点,互联网星座支持随遇接入遥感卫星和信息在轨直接处理的应用前景备受期待,但由于轨道高度不同会产生双向高动态异构星座的接入互联问题。首先,通过设定低轨卫星互联网星座在不同轨道特性、不同卫星数量情况下的随遇接入仿真场景,重点探讨了时空非连续可视性和多普勒频移问题对遥感卫星接入性能的影响;其次,基于遥感卫星随遇接入互联网星座场景的特点,分析了不同时延性在轨处理任务的流程及其星地功能分配;最后,对当前在轨智能处理算法存在的问题和未来研究重点进行阐述,为未来低轨互联网星座及遥感卫星的发展和联合组网应用提供可靠的理论支撑。 相似文献
3.
International Journal of Speech Technology - With the development of multimedia technology and network technology applications, it is possible to implement online teaching systems in schools. This... 相似文献
4.
Kai Liu Chenyang Zhou Jiaming Hu Song Zhang Qingqing Zhang Ce Sun Yusheng Shi Huajun Sun Changxia Yin Yuzhen Zhang Yu Fu 《Journal of the European Ceramic Society》2021,41(12):5909-5917
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices. 相似文献
5.
内容导读目前,针对潜在6G关键技术的场景与需求研究成为学术界的热点。面向未来更多类型终端的智能互联与新兴服务的需求,人工智能应用于无线通信物理层的信道估计、编译码及接收机设计,解决基于大数据的网络自主优化,基于泛在无线感知和边缘侧的强大算力构成的多接入边缘计算,已成为6G无线技术发展的重要趋势。在未来智能车联网、物联网、有人/无人交互、全息通信等场景下,面向未来的智能通信计算融合需求,存在许多拟待解决的关键科学问题。 相似文献
6.
7.
Xiaoyan Dong Xu Li Xiuli Chen Hongyun Chen Congcong Sun Junpeng Shi Feihong Pang Huanfu Zhou 《Ceramics International》2021,47(3):3079-3088
Dielectric capacitors with decent energy storage and fast charge-discharge performances are essential in advanced pulsed power systems. In this study, novel ceramics (1-x)NaNbO3-xBi(Ni2/3Nb1/3)O3(xBNN, x = 0.05, 0.1, 0.15 and 0.20) with high energy storage capability, large power density and ultrafast discharge speed were designed and prepared. The impedance analysis proves that the introducing an appropriate amount of Bi(Ni0·5Nb0.5)O3 boosts the insulation ability, thus obtaining a high breakdown strength (Eb) of 440 kV/cm in xBNN ceramics. A high energy storage density (Wtotal) of 4.09 J/cm3, recoverable energy storage density (Wrec) of 3.31 J/cm3, and efficiency (η) of 80.9% were attained in the 0.15BNN ceramics. Furthermore, frequency and temperature stability (fluctuations of Wrec ≤ 0.4% over 5–100 Hz and Wrec ≤ 12.3% over 20–120 °C) were also observed. The 0.15BNN ceramics exhibited a large power density (19 MW/cm3) and ultrafast discharge time (~37 ns) over the range of ambient temperature to 120 °C. These enhanced performances may be attributed to the improved breakdown strength and relaxor behavior through the incorporation of BNN. In conclusion, these findings indicate that 0.15BNN ceramics may serve as promising materials for pulsed power systems. 相似文献
8.
Zhenkun Ke Xin Cao Chuanli Shan Lifen Shi Pingping Wang Yong Yang Fengyang Zhao Jiedong Cui Jinwei Li Gang Zhou Min Guan Tao Yu 《Ceramics International》2021,47(14):19605-19613
The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R2O–CaO–B2O3–SiO2) systematically. Because the glass would emulsify when Li2O was added to the glass batch, this article did not discuss Li2O. The results showed that when the amount of Na2O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na2O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased. 相似文献
9.