全文获取类型
收费全文 | 821篇 |
免费 | 10篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 15篇 |
综合类 | 6篇 |
化学工业 | 366篇 |
金属工艺 | 45篇 |
机械仪表 | 21篇 |
建筑科学 | 4篇 |
矿业工程 | 1篇 |
能源动力 | 3篇 |
武器工业 | 2篇 |
无线电 | 272篇 |
一般工业技术 | 98篇 |
冶金工业 | 5篇 |
自动化技术 | 13篇 |
出版年
2023年 | 32篇 |
2022年 | 48篇 |
2021年 | 41篇 |
2020年 | 29篇 |
2019年 | 38篇 |
2018年 | 53篇 |
2017年 | 46篇 |
2016年 | 26篇 |
2015年 | 10篇 |
2014年 | 47篇 |
2013年 | 25篇 |
2012年 | 31篇 |
2011年 | 58篇 |
2010年 | 34篇 |
2009年 | 47篇 |
2008年 | 48篇 |
2007年 | 46篇 |
2006年 | 56篇 |
2005年 | 51篇 |
2004年 | 20篇 |
2003年 | 24篇 |
2002年 | 14篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
排序方式: 共有851条查询结果,搜索用时 0 毫秒
121.
122.
介绍了近几年无铅钎料的应用研究和发展情况以及与无铅钎料有关的立法。为国内电子材料行业无铅钎料的研究和发展提出建议。 相似文献
123.
Hao Qian Zhenglei Yu Minmin Mao Yunfei Liu Yinong Lyu 《Journal of the European Ceramic Society》2018,38(1):361-369
BiAlO3-doped Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 (BA-doped BNT-BKT) ceramics are greatly concerned due to their sufficient electric-field-induced strain with small hysteresis and remnant strain for high precision positioning devices and other actuators. In this paper, the structural analysis especially the high-resolution transmission electron microscope (HRTEM) is used to reveal the origin of excellent properties obtained in 0.96(0.75BNT-0.25BKT)-0.04BA, which exhibits a large strain of 0.21% at ~70 kV/cm, a small strain hysteresis of only 24% and a near-zero remnant strain. Using HRTEM, the antiferroelectric nano-domains composited by three variants of in-phase a0a0c+ octahedral tilting coexisted with the remnant ferroelectric nano-domains of anti-phase a?a?a? octahedral tilting are directly identified. Then a continuous tilting model is proposed to interpret the gradually transitional tilting involving nano-domains leading to the small hysteresis and near-zero remnant strain. The findings may pave a way for further optimizing the properties through creating stable antiferroelectric nano-domains in BNT-based ceramics and the analogues. 相似文献
124.
Sagar M. Mane Pravin M. Tirmali Snehal L. Kadam Dadasaheb J. Salunkhe Chandrakant B. Kolekar 《应用陶瓷进展》2017,116(6):325-332
0.5[(Ba0.7Ca0.3)TiO3]–0.5[Ba(Zr0.2Ti0.8)O3] lead-free ceramics were synthesised by coprecipitation method and sintered by fast microwave sintering (MWS) and by conventional sintering (CS) at 1200°C. After being sintered with the two different methods, the materials were characterised for structural, microstructural, frequency and temperature-dependent dielectric properties, Raman spectroscopy, and ferroelectric measurements. Results are compared and discussed in the present paper. X-ray diffraction confirms the presence of the tetragonal and rhombohedral phases in the composites sintered by both methods. The ferroelectric to paraelectric transition temperature (Tc) is increased in microwave-sintered composite. Diffuse constant (γ) values show BCT–BZT ceramics to be neither normal ferroelectrics nor relaxor ferroelectrics. Raman spectra confirm phase transition in the ceramic samples. Saturation polarisation (Ps) values are 7.62 and 4.28?µC?cm?2 and nearly equal remanant polarisation (Pr) values were observed for BCT–BZT composite sintered with MWS and CS, respectively. 相似文献
125.
Minna Arra Dongkai Shangguan Erro Ristolainen Toivo Lepistö 《Journal of Electronic Materials》2002,31(11):1130-1138
Solder balling in Sn/Ag/Cu solder pastes was studied in this work. Three different solder pastes, several different reflow
profiles and conditions, and two stencil thicknesses were used in the investigation. During the first phase, called the verification
phase, the solder pastes were checked to ensure they met the minimum requirements. In the process-screening phase, the reflow
profile was varied. Results show that besides flux chemistry, reflow atmosphere plays the major role in solder balling. The
average number of solder balls with the best paste was one fifth of that with the worst paste. Furthermore, with all the pastes,
the number of solder balls dropped close to zero when nitrogen atmosphere was used. Another finding during the reflow process
screening was the influence of the stencil thickness on the solder-balling result. With a thinner stencil, two of the pastes
exhibited significant solder balling. This is assumed to be caused by the different ability of fluxes to withstand oxidation
during the preheating in the reflow process. In the last phase, the effect of the solder-paste particle size on solder balling
was studied more closely. The flux chemistry was kept unchanged, and the solder particle size was varied between type 3 and
type 4. The results show that, with type 4 paste, significantly more solder balls are formed compared to type 3 paste. It
was also confirmed that, regarding the reflow profile, the ramp-up rate from 150°C to 217°C and the reflow atmosphere were
the most significant factors that determine the solder-ball formation for both types of paste. 相似文献
126.
Jinfeng Lin Guanglong Ge Jiangfan Li Jin Qian Kun Zhu Yongqi Wei Cheng Shi Guihui Li Fei Yan Wenxu Li Jialiang Zhang Jiwei Zhai Haijun Wu 《Advanced functional materials》2023,33(42):2303965
The development of high-performance (K,Na)NbO3 (KNN)-based lead-free piezoceramics for next-generation electronic devices is crucial for achieving environmentally sustainable society. However, despite recent improvements in piezoelectric coefficients, correlating their properties to underlying multiscale structures remains a key issue for high-performance KNN-based ceramics with complex phase boundaries. Here, this study proposes a medium-entropy strategy to design “local polymorphic distortion” in conjunction with the construction of uniformly oversize grains in the newly developed KNN solid-solution, resulting in a novel large-size hierarchical domain architecture (≈0.7 µm wide). Such a structure not only facilitates polarization rotation but also ensures a large residual polarization, which significantly improves the piezoelectricity (≈3.2 times) and obtains a giant energy harvesting performance (Wout = 2.44 mW, PD = 35.32 µW mm−3, outperforming most lead-free piezoceramics). This study confirms the coexistence of multiphase through the atomic-resolution polarization features and analyzes the domain/phase transition mechanisms using in situ electric field structural characterizations, revealing that the electric field induces highly effective multiscale polarization configuration transitions based on T–O–R sequential phase transitions. This study demonstrates a new strategy for designing high-performance piezoceramics and facilitates the development of lead-free piezoceramic materials in energy harvesting applications. 相似文献
127.
This work summarizes the interfacial reaction between lead-free solder Sn-3.5Ag and electrolessly plated Ni-P metallization
in terms of morphology and growth kinetics of the intermetallic compounds (IMC). Comparison with pure Ni metallization is
made in order to clarify the role of P in the solder reaction. During reflow, the IMCs formed with the Ni-P under-bump metallization
(UBM) exist in chunky crystal blocks and small crystal agglomerates, while the ones with the sputtered Ni UBM exhibit uniformly
scallop grains with faceted surfaces. The IMC thickness increases with reflow time following approximately a t1/3 power law for both systems. The IMC growth rate is higher with the Ni-P UBM than the Ni UBM. The thickness of the Ni3Sn4 layer increases linearly with the square root of thermal aging time, indicating that the growth of the IMCs is a diffusion-controlled
process. The activation energy for Ni3Sn4 growth in solid-state reaction is found to be 110 kJ/mol and 91 kJ/mol for the Ni-P and sputtered Ni UBMs, respectively.
Kirkendall voids are detected inside the Ni3P layer in the Sn-3.5Ag/Ni-P system. No such voids are found in the Sn-3.5Ag/Ni system. 相似文献
128.
宁海霞 《稀有金属材料与工程》2016,45(5):1249-1252
采用高温固相法制备了钙钛矿结构的0.7BiFeO_3-0.2PbTiO_3-0.1BaTiO_3陶瓷,研究了该陶瓷的介电性能、压电性能及其老化性能。结果表明,该陶瓷是一种非常有潜力的高温压电陶瓷,其介电常数和介电损耗分别为390和0.015,铁电居里温度TC约为600℃,压电常数d_(33)约为100 pC/N,压电常数的时间稳定性和热稳定性好,热退极化温度Td约为500℃。压电常数热退极化机理主要为内在的剩余极化老化,辅以低浓度氧空位等外在缺陷对畴壁的钉扎作用。 相似文献
129.
Sn whisker growth in Sn-9Zn-0.5Ga-0.7Pr lead-free solder 总被引:1,自引:0,他引:1
Huan YeSongbai Xue Liang ZhangZhengxiang Xiao Yuhua HuZhongmin Lai Hong Zhu 《Journal of Alloys and Compounds》2011,509(5):L52
The spontaneous growth of Sn whisker in Sn-Zn series solder is newly reported in this work. It is found that during the exposure of Sn-9Zn-0.5Ga-0.7Pr bulk solder to ambient conditions for a few hours, many different lengths of needle-like Sn whiskers originate spontaneously from the Sn-Pr intermetallic compounds of the solder and grow rapidly at a rate of about 3.5 Å/s. It is proposed that the driving force for whisker formation is the compressive stress resulting from the oxidation of Sn-Pr compounds, and that the free Sn atoms released from oxidation reaction feed the whisker growth during exposure. 相似文献
130.
Haimin NiLaihui Luo Weiping LiYuejin Zhu Haosu Luo 《Journal of Alloys and Compounds》2011,509(9):3958-3962
Lead-free (1 − x)Bi0.47Na0.47Ba0.06TiO3-xKNbO3 (BNBT-xKN, x = 0-0.08) ceramics were prepared by ordinary ceramic sintering technique. The piezoelectric, dielectric and ferroelectric properties of the ceramics are investigated and discussed. The results of X-ray diffraction (XRD) indicate that KNbO3 (KN) has diffused into Bi0.47Na0.47Ba0.06TiO3 (BNBT) lattices to form a solid solution with a pure perovskite structure. Moderate additive of KN (x ≤ 0.02) in BNBT-xKN ceramics enhance their piezoelectric and ferroelectric properties. Three dielectric anomaly peaks are observed in BNBT-0.00KN, BNBT-0.01KN and BNBT-0.02KN ceramics. With the increment of KN in BNBT-xKN ceramics, the dielectric anomaly peaks shift to lower temperature. BNBT-0.01KN ceramic exhibits excellent piezoelectric properties and strong ferroelectricity: piezoelectric coefficient, d33 = 195 pC/N; electromechanical coupling factor, kt = 58.9 and kp = 29.3%; mechanical quality factor, Qm = 113; remnant polarization, Pr = 41.8 μC/cm2; coercive field, Ec = 19.5 kV/cm. 相似文献