全文获取类型
收费全文 | 927篇 |
免费 | 108篇 |
国内免费 | 157篇 |
专业分类
电工技术 | 32篇 |
综合类 | 19篇 |
化学工业 | 69篇 |
金属工艺 | 36篇 |
机械仪表 | 8篇 |
建筑科学 | 3篇 |
能源动力 | 65篇 |
石油天然气 | 2篇 |
武器工业 | 3篇 |
无线电 | 717篇 |
一般工业技术 | 206篇 |
冶金工业 | 1篇 |
原子能技术 | 5篇 |
自动化技术 | 26篇 |
出版年
2024年 | 2篇 |
2023年 | 35篇 |
2022年 | 17篇 |
2021年 | 25篇 |
2020年 | 29篇 |
2019年 | 45篇 |
2018年 | 27篇 |
2017年 | 46篇 |
2016年 | 42篇 |
2015年 | 59篇 |
2014年 | 46篇 |
2013年 | 66篇 |
2012年 | 50篇 |
2011年 | 96篇 |
2010年 | 66篇 |
2009年 | 51篇 |
2008年 | 61篇 |
2007年 | 35篇 |
2006年 | 60篇 |
2005年 | 35篇 |
2004年 | 39篇 |
2003年 | 24篇 |
2002年 | 24篇 |
2001年 | 30篇 |
2000年 | 23篇 |
1999年 | 17篇 |
1998年 | 24篇 |
1997年 | 21篇 |
1996年 | 23篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
排序方式: 共有1192条查询结果,搜索用时 15 毫秒
1.
A modeling theory is developed to predict the performance of piezoresistors which incorporate Schottky diode electrical contacts. This new theory allows the design of high performance gauges which can be fabricated using Non-Lithographically-Based Microfabrication (NLBM) techniques. These semiconductor piezoresistors can be designed in customizable sizes and fabricated in parallel in order to integrate position sensing into MEMS flexural positioners. Customizable sensing for nanopositioning platforms will enable advances in a range of nano-scale fabrication and metrology applications. A semiconductor piezoresistor with Schottky diode contacts was fabricated and attached to a titanium flexure. This device is shown to match predicted electrical performance within about 8% and to show a gauge factor of 116, within 2% of the predicted value. Optimized performance limits for Schottky diode semiconductor piezoresistors are identified to be about 127 dB full noise dynamic range for a quarter bridge over a 10 kHz sensor bandwidth on a 600 μm width titanium flexure, making them ideal for sensing on meso-/micro-scale flexural positioners. Methods are suggested for achieving the performance limits indicated above and the impact of these methods on the sensor dynamic range are studied. 相似文献
2.
Zhongyuan Fu Xinyi Ma Bing Xia Xiaoyun Hu Jun Fan Enzhou Liu 《International Journal of Hydrogen Energy》2021,46(37):19373-19384
Schottky junction and p-n heterojunction are widely employed to enhance the charge transfer during the photocatalysis process. Herein, Cu and Cu3P co-modified TiO2 nanosheet hybrid (Cu–Cu3P/TiO2) was fabricated using an in situ hydrothermal method. The ternary composite achieved the superior H2 evolution rate of 6915.7 μmol g?1 h?1 under simulated sunlight, which was higher than that of Cu/TiO2 (4643.4 μmol g?1 h?1) and Cu3P/TiO2 (6315.8 μmol g?1 h?1) and pure TiO2 (415.7 μmol g?1 h?1). The enhanced activity can be attributed to the collaboration effect of Schottky junction and p-n heterojunction among Cu/TiO2 and Cu3P/TiO2, which can harvest the visible light, reduce the recombination of charge carriers and lower the overpotential of H2 evolution, leading to a fast H2 evolution kinetics. This work develops a feasible method for the exploration of H2 evolution photocatalyst with outstanding charge separation properties. 相似文献
3.
Poly (linoleic acid)-g-poly(methyl methacrylate) (PLiMMA) graft copolymer was synthesized and characterized. PLiMMA graft copolymer was synthesized from polymeric linoleic acid peroxide (PLina) possessing peroxide groups in the main chain by free radical polymerization of methyl methacrylate. Later, PLiMMA was characterized by proton nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Furthermore, Au/PLiMMA/n-Si diode was fabricated for the purpose of investigating PLiMMA׳s conformity in diodes. The main electrical characteristics of this diode were investigated using experimental current–voltage (I–V) measurements in dark and at room temperature. Obtained results, such as sufficiently high rectifying ratio of 4.5×104, indicate that PLiMMA is a promising organic material for electronic device applications. 相似文献
4.
The electrical characteristics of Al/strained Si-on-insulator (sSOI) Schottky diode have been investigated using current–voltage (I–V) and capacitance–voltage (C–V) measurements in the wide temperature range of 200–400 K in steps of 25 K. It was found that the barrier height (0.57–0.80 eV) calculated from the I–V characteristics increased and the ideality factor (1.97–1.28) decreased with increasing temperature. The barrier heights determined from the C–V measurements were higher than those extracted from the I–V measurements, associated with the formation of an inhomogeneous Schottky barrier at the interface. The series resistance estimated from the forward I–V characteristics using Cheung and Norde methods decreased with increasing temperature, implying its strong temperature dependence. The observed variation in barrier height and ideality factor could be attributed to the inhomogeneities in Schottky barrier, explained by assuming Gaussian distribution of barrier heights. The temperature-dependent I–V characteristics showed a double Gaussian distribution with mean barrier heights of 0.83 and 1.19 eV and standard deviations of 0.10 and 0.16 eV at 200–275 and 300–400 K, respectively. From the modified Richardson plot, the modified Richardson constant were calculated to be 21.8 and 29.4 A cm−2 K−2 at 200–275 and 300–400 K, respectively, which were comparable to the theoretical value for p-type sSOI (31.6 A cm−2 K−2). 相似文献
5.
《International Journal of Hydrogen Energy》2022,47(19):10628-10637
Solar-to-hydrogen production has attracted increasing attention since it possesses great potential in alleviating energy and environmental crises to some extent. The key issue is to develop efficient photocatalysts exhibiting superior hydrogen production capability. In this work, Cu@TiO2 hybrid (Cu nanoparticles encapsulated in TiO2) has been successfully prepared by Cu2O self-template reduction through solvothermal treatment in ethylene glycol-water mixed solvent. When octahedral Cu2O is involved in the reaction system, the Cu2O@Ti-precursor octahedral structure is first formed and subsequently the Cu@TiO2 hybrid is prepared with the reduction of ethylene glycol (EG). The Cu@TiO2 hybrid derived with different mass of Cu exhibits improved photocatalytic hydrogen production performance compare to pure TiO2 and P25. Among those photocatalysts, the Cu@TiO2-10% (the copper content is 10 wt%) shows the highest hydrogen evolution rate of 4336.7 μmol g?1 h?1, and it is twice as much as the pure TiO2 and 1.9 times as much as P25, respectively. Based on the photo/electrochemical results, an efficient photo-generated electron-hole separation contributes to the enhancement of photocatalytic H2 evolution upon the Cu@TiO2 hybrid. When replacing octahedral Cu2O with cubic and truncated octahedrons ones, the Cu@TiO2 hybrid photocatalysts are also obtained and they also display superior solar-to-hydrogen evolution than pure TiO2 and P25. It is expected this work could develop an approach to design Cu-encapsulated hybrid photocatalysts for hydrogen generation. 相似文献
6.
提出在Ni中掺入夹层Zr的方法来提高NiSi的热稳定性.具有此结构的薄膜,600~800℃快速热退火后,薄层电阻保持较低值,小于2Ω/□.经XRD和Raman光谱分析表明,薄膜中只存在低阻NiSi相,而没有高阻NiSi2相生成.Ni(Zr)Si的薄层电阻由低阻转变为高阻的温度在800℃以上,比没有掺Zr的镍硅化物的转变温度上限提高了100℃.Ni(Zr)Si/Si肖特基势垒二极管能够经受650~800℃不同温度的快速热退火,肖特基接触特性良好,肖特基势垒高度为0.63eV,理想因子接近于1. 相似文献
7.
8.
金刚石因其优异的物理化学特性,被视为下一代电力电子器件的终极材料,金刚石半导体器件的制备受到了科研工作者的广泛关注。文章对金刚石基二极管、开关器件和边缘终止效应等方面的研究成果进行了概述。着重阐述了金刚石半导体器件的电学特性,尤其是,在500 ℃高温条件下得到高正向电流密度,阻断能力大于10 kV,并展现出长程稳定性的肖特基势垒二极管;在金属半导体场效应晶体管与金属氧化物半导体场效应晶体管上制得阻断电压超过2 kV的开关器件。同时,针对加工技术带来的表面缺陷,详细讨论了金刚石器件的表面终止技术和缺陷对器件性能的影响,并展望了金刚石半导体在肖特基势垒二极管及场效应晶体管等领域的应用前景。 相似文献
9.
《Journal of the European Ceramic Society》2022,42(1):162-168
Excellent electrical properties and the improved long-term stability of ZnO varistor ceramics were simultaneously achieved by doping NiO. The microstructural features were investigated using X-ray diffractometer, scanning electron microscopy, and energy dispersive spectroscopy, while the intrinsic point defects were characterized using frequency domain dielectric spectroscopy and verified by photoluminescence and Raman spectra. The results indicated that in the ZnO varistor ceramics, a reverse manipulation of donor point defects, i.e., suppressing mobile zinc interstitial but increasing stable oxygen vacancy, was achieved. The long-term stability of NiO-doped ZnO ceramics was improved via a decrease in zinc interstitial density, with a degradation rate of 0.064 μA cm?2 h?0.5. Meanwhile, due to an increase in oxygen vacancy density, the excellent nonlinear current–voltage performance, i.e., a high nonlinear coefficient (72.9), low leakage current density (0.08 μA cm?2), and low grain resistivity (13.43 × 10?3 Ω m), was maintained. The findings of this study provide a possible method for developing high-performance ZnO varistor ceramics by manipulating point defects. 相似文献
10.
CaCu3-xNixTi4O12 (x?=?0, 0.05, and 0.10) powders were synthesized using a solid state reaction method. Phase structure and microstructure analyses revealed that all sintered CaCu3-xNixTi4O12 ceramics were of a pure phase. The CaCu3Ti4O12 ceramics had a dense microstructure and grain sizes were enlarged by doping with Ni2+. Interestingly, the dielectric permittivity was significantly enhanced, whereas the loss tangent was greatly suppressed to ~0.046–0.034 at 1?kHz. All sintered ceramics exhibited non-Ohmic characteristics. Clarification of the influences of DC bias showed that the dielectric permittivity and loss tangent values were increased by DC bias. The resistance of grain boundaries and the associated conduction activation energy of CaCu3-xNixTi4O12 ceramics were reduced as the DC bias voltage increased. Therefore, the observed non-Ohmic behavior and significantly enhanced dielectric properties should be closely related to variation in the Schottky barriers at the grain boundaries. 相似文献