全文获取类型
收费全文 | 1146篇 |
免费 | 99篇 |
国内免费 | 101篇 |
专业分类
电工技术 | 249篇 |
综合类 | 55篇 |
化学工业 | 202篇 |
金属工艺 | 50篇 |
机械仪表 | 111篇 |
建筑科学 | 12篇 |
矿业工程 | 1篇 |
能源动力 | 4篇 |
武器工业 | 4篇 |
无线电 | 311篇 |
一般工业技术 | 283篇 |
冶金工业 | 4篇 |
原子能技术 | 3篇 |
自动化技术 | 57篇 |
出版年
2023年 | 13篇 |
2022年 | 5篇 |
2021年 | 23篇 |
2020年 | 18篇 |
2019年 | 15篇 |
2018年 | 24篇 |
2017年 | 34篇 |
2016年 | 36篇 |
2015年 | 31篇 |
2014年 | 37篇 |
2013年 | 195篇 |
2012年 | 42篇 |
2011年 | 71篇 |
2010年 | 30篇 |
2009年 | 76篇 |
2008年 | 92篇 |
2007年 | 105篇 |
2006年 | 97篇 |
2005年 | 75篇 |
2004年 | 72篇 |
2003年 | 32篇 |
2002年 | 41篇 |
2001年 | 34篇 |
2000年 | 22篇 |
1999年 | 23篇 |
1998年 | 21篇 |
1997年 | 21篇 |
1996年 | 14篇 |
1995年 | 20篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 1篇 |
排序方式: 共有1346条查询结果,搜索用时 15 毫秒
1.
Lingfang Zou Zhuan Li Zonglong Gao Fu Chen Wenjie Li Yong Yu Yimin Li Peng Xiao 《Ceramics International》2021,47(14):19328-19339
Improving the piezoelectric activity of lead zirconate titanate (PZT) ceramics is of great importance for practical applications. In this study, the influence of Pr3+ doping on the ferroelectric phase composition, microstructure, and electric properties on the A-site of (Pb1-1.5xPrx)(Zr0.52Ti0.48)O3 is extensively investigated. A dense and fine microstructural sample is obtained with the introduction of Pr3+. The results show that the morphotropic phase boundary (MPB) moves to the rhombohedral phase region. The rhombohedral and tetragonal phases exhibit an ideal coexistence in the 4 mol.% Pr3+ doped (PPZT4) samples. Lead vacancy and the reduction of the potential energy barrier are considered to be the key mechanisms for donor doping, which is upheld by the Pr3+ doping. Combining the I-E hysteresis loops with the P-E hysteresis loops, it becomes apparent that both contribution maximums of the domain switching and residual polarisation are in PPZT4. Moreover, the thermal aging resistance of PZT is improved by doping, and the temperature stability is optimised from 83% in PZT to 96% in PPZT4. Hence, an appropriate amount of Pr3+ doping can effectively improve the piezoelectric activity of PZT ceramics in the MPB area and optimise the performance stability of the material under application temperatures. 相似文献
2.
《Ceramics International》2022,48(21):31111-31120
The current work reports a comparison between the structural and optical attributes of PZT (52/48) powder and thin film prepared via solid-state reaction and sol-gel spin-coating technique, respectively. The two obtained PZT samples, PZT-I corresponding to powder which was calcined at 875°C for 2 h, and PZT-II corresponding to a thin film which was annealed at 650°C for 2 h, were investigated via X-Ray Diffraction, Raman Spectroscopy, UV–Vis Spectroscopy, and SEM analysis. The diffraction spectra suggested the creation of a polycrystalline perovskite structure in both the samples. The optical band gap was evaluated using Tauc's relation. The bandgap values were found to be 3.2 eV for PZT-I and 3.87 eV for PZT-II. The bandgap values are significantly different for the PZT materials prepared by the two different methods. 相似文献
3.
K.P. Andryushin L.A. Shilkina I.N. Andryushina M.O. Moysa D.I. Rudsky L.A. Reznichenko 《Ceramics International》2021,47(1):138-148
Experimental research of the crystal structure, polarization properties, and reverse nonlinearity of ceramic solid solutions of the (1-x) (Na0·5K0.5)NbO3-xPb(Ti0·5Zr0.5)O3 (KNN-PZT) quasi-binary system with 0.0 = x ≤ 1.0 in a wide range of external influences (temperatures, strength of dc/ac fields) has been done. Based on the X-ray structural data, an x-T diagram of the system has been constructed, and correlations of the behavior of the macroproperties of solid solutions with the features of their phase states with the temperature change have been established. It has been concluded that it is advisable to use the proposed compositions when designing microelectronic devices operating in various extreme conditions. 相似文献
4.
《Journal of the European Ceramic Society》2020,40(15):5369-5375
This work reports on direct crystallization of PbZr0.53Ti0.47O3 (PZT) thin films on glass and polymeric substrates, using pulsed thermal processing (PTP). Specifically, xenon flash lamps deliver pulses of high intensity, short duration, broadband light to the surface of a chemical solution deposited thin film, resulting in the crystallization of the film. Structural analysis by X-ray diffraction (XRD) and transmission electron microscopy show the existence of perovskite structure in nano-sized grains (≤5 nm). Local functional analysis by band excitation piezoelectric spectroscopy and electrostatic force microscopy confirm the presence of a ferroelectric phase and retention of voltage-written polarization for multiple days. Based on structural and functional analyses, strategies are discussed for optimization of pulse voltage and duration for the realization of crystalline ferroelectric thin films. For ∼200 nm-thick PZT films on glass substrates, 500 μs-long pulses were required for crystallization, starting with 100 pulses at 350 V, 10 or 25 pulses at 400 V and in general lower number of pulses at higher voltages (resulting in higher radiant energy). Overall power densities of >6.4 kW/cm2 were needed for appearance of peaks corresponding to the perovskite phase in the XRD. Films on glass processed at 350–400 V had a higher degree of 111-oriented perovskite grains. Higher applied radiant energy (through increased pulse voltage or count) resulted in more random and/or partially 001-oriented films. For ∼1 μm-thick PZT films on polymeric substrates, 10 to 25 250 μs-long pulses at voltages ranging between 200 to 250 V, corresponding to power densities of ∼2.8 kW/cm2, were optimal for maximized perovskite phase crystallization, while avoiding substrate damage. 相似文献
5.
Yan Zhang James Roscow Mengying Xie Chris Bowen 《Journal of the European Ceramic Society》2018,38(12):4203-4211
High performance lead zirconate titanate (PZT) ceramics with aligned porosity for sensing applications were fabricated by an ice-templating method. To demonstrate the enhanced properties of these materials and their potential for sensor and hydrophone applications, the piezoelectric voltage constants (g33 and g31), hydrostatic parameters (dh, gh, ?d33/d31, dh·gh and dh·gh/tanδ) and AC conductivity as a function of the porosity in directions both parallel and perpendicular to the freezing temperature gradient were studied. As the porosity level was increased, PZT poled parallel to the freezing direction exhibited the highest dh, ?d33/d31 and figures of merit dh·gh, dh·gh/tanδ compared to the dense and PZT poled perpendicular to the freezing direction. The gh, g33 and g31 coefficients were highest for the PZT poled perpendicular to the freezing direction; the gh was 150%–850% times higher than dense PZT, and was attributed to the high piezoelectric activity and reduced permittivity in this orientation. This work demonstrates that piezoelectric ceramics produced with aligned pores by freeze casting are a promising candidate for a range of sensor applications and the polarisation orientation relative to the freezing direction can be used to tailor the microstructure and optimise sensitivity for sensor and hydrostatic transducer applications. 相似文献
6.
Glenn J.T. Leighton Paul M. Jones Quentin Lonne Robert A. Dorey Fabien Giuliano 《Journal of the European Ceramic Society》2018,38(10):3483-3488
Using thick and thin films instead of bulk functional materials presents tremendous advantages in the field of flexible electronics and component miniaturization. Here, a low-cost method to grow and release large-area, microscale thickness, freestanding, functional, ceramic foils is reported. It uses evaporation of sodium chloride to silicon wafer substrates as sacrificial layers, upon which functional lead titanate zirconate ceramic films are grown at 710?°C maximum temperature to validate the method. The freestanding, functional foils are then released by dissolution of the sacrificial sodium chloride in water and have the potential to be integrated into low-thermal stability printed circuits and flexible substrates. The optimization of the sodium chloride layer surface quality and bonding strength with the underlying wafer is achieved thanks to pre-annealing treatment. 相似文献
7.
D. Kajewski P. Zajdel A. Soszyński J. Koperski I. Lazar K. Roleder 《Ceramics International》2019,45(8):9871-9877
Lead zirconate-titanate PbZr0.70Ti0.30O3 ceramics doped with bismuth oxide has been investigated. Dielectric and optical measurements were performed to check the dopant influence on phase transitions and pre-transitional effects. It has been postulated that the temperature at which maximum permittivity occurs is not connected with structural phase transitions. 相似文献
8.
Yu Chen Jiageng Xu Qian Xu Shaoxiong Xie Qingyuan Wang Jianguo Zhu 《Journal of the American Ceramic Society》2020,103(2):1067-1078
In this work, ferroelastic domain switching and R-curve behavior in lead zirconate titanate (Nb/Ce co-doped Pb(Zr0.52Ti0.48)O3, ab. PZT-NC)-based ferroelectric ceramics were investigated, using the indentation-strength-in-bending (ISB) method. Firstly, Vickers indentation test examined the notable fracture anisotropy of PZT-NC ceramics between the poling direction and its perpendicular direction, and the crack open displacement (COD) profiles in the two directions were also theoretically calculated from the indentation fracture mechanics. And then two kinds of ferroelastic domain switching modes (in-plane and out-of-plane) were used for explaining such anisotropic propagation behavior of indentation cracks. The subsequent three-point bending test illustrated the dependence of fracture strength on indentation load and the rising crack growth resistance curves (R-curves) in two directions. The resulted R-curves were fitted by the Hill's type Growth Function successfully, giving the reasonable values of crack extension exponential (n), plateau fracture toughness (Kmax), and initial fracture toughness (Kini). The in-plane ferroelastic domain switching was identified as a more significant toughening mechanism for PZT-NC ceramics than the out-of-plane switching due to more switchable domains. 相似文献
9.
You Jeong Eum Jungho Ryu Chang Young Koo Jung Min Park Jai-Yeoul Lee Hee Young Lee 《Ceramics International》2021,47(5):6371-6375
Magnetoelectric (ME) property modulation in heterostructured (Ni0.5Zn0.5)Fe2O4/Pt/Pb(Zr0.3Ti0.7)O3 (NZFO/Pt/PZT) thin films on platinized Si substrate by thermal annealing condition variation was studied. In an attempt to prevent interfacial reaction between NZFO and PZT layers during high temperature annealing, thin Pt layer was deposited which can serve as inter-diffusion barrier as well as electrode. The ferroelectric, magnetic, and ME properties of the heterostructured film were noticeably modulated due to microstructural evolution and clamping relaxation developed during thermal annealing process. Room temperature ME voltage coefficient of the heterostructured thin films was enhanced with increasing annealing temperature and reached to 29 mV/cm·Oe when annealed at 650 °C. 相似文献
10.
Poly(vinylidene fluoride), PVDF, and its copolymers are the family of polymers with the highest dielectric constant and electroactive response, including piezoelectric, pyroelectric and ferroelectric effects. The electroactive properties are increasingly important in a wide range of applications such as in biomedicine, energy generation and storage, monitoring and control, and include the development of sensors and actuators, separator and filtration membranes and smart scaffolds, among others. For many of these applications the polymer should be in one of its electroactive phases. This review presents the developments and summarizes the main characteristics of the electroactive phases of PVDF and copolymers, indicates the different processing strategies as well as the way in which the phase content is identified and quantified. Additionally, recent advances in the development of electroactive composites allowing novel effects, such as magnetoelectric responses, and opening new applications areas are presented. Finally, some of the more interesting potential applications and processing challenges are discussed. 相似文献