全文获取类型
收费全文 | 124671篇 |
免费 | 11591篇 |
国内免费 | 6257篇 |
专业分类
电工技术 | 7954篇 |
技术理论 | 8篇 |
综合类 | 9279篇 |
化学工业 | 20219篇 |
金属工艺 | 6296篇 |
机械仪表 | 7851篇 |
建筑科学 | 10978篇 |
矿业工程 | 3400篇 |
能源动力 | 3630篇 |
轻工业 | 9225篇 |
水利工程 | 2417篇 |
石油天然气 | 6649篇 |
武器工业 | 1077篇 |
无线电 | 13991篇 |
一般工业技术 | 14862篇 |
冶金工业 | 5694篇 |
原子能技术 | 1552篇 |
自动化技术 | 17437篇 |
出版年
2024年 | 548篇 |
2023年 | 1990篇 |
2022年 | 3556篇 |
2021年 | 4844篇 |
2020年 | 3739篇 |
2019年 | 3194篇 |
2018年 | 3428篇 |
2017年 | 3959篇 |
2016年 | 3589篇 |
2015年 | 4734篇 |
2014年 | 6086篇 |
2013年 | 7175篇 |
2012年 | 7759篇 |
2011年 | 8412篇 |
2010年 | 7571篇 |
2009年 | 7165篇 |
2008年 | 7322篇 |
2007年 | 6863篇 |
2006年 | 6882篇 |
2005年 | 5797篇 |
2004年 | 4203篇 |
2003年 | 4258篇 |
2002年 | 4729篇 |
2001年 | 4163篇 |
2000年 | 3404篇 |
1999年 | 3305篇 |
1998年 | 2398篇 |
1997年 | 2144篇 |
1996年 | 2035篇 |
1995年 | 1675篇 |
1994年 | 1342篇 |
1993年 | 967篇 |
1992年 | 748篇 |
1991年 | 553篇 |
1990年 | 418篇 |
1989年 | 384篇 |
1988年 | 331篇 |
1987年 | 193篇 |
1986年 | 150篇 |
1985年 | 103篇 |
1984年 | 57篇 |
1983年 | 37篇 |
1982年 | 50篇 |
1981年 | 42篇 |
1980年 | 55篇 |
1979年 | 29篇 |
1977年 | 7篇 |
1962年 | 42篇 |
1961年 | 39篇 |
1960年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 32 毫秒
1.
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
2.
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
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.
6.
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
7.
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.
10.