全文获取类型
收费全文 | 267篇 |
免费 | 17篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 53篇 |
综合类 | 11篇 |
化学工业 | 41篇 |
金属工艺 | 3篇 |
机械仪表 | 3篇 |
建筑科学 | 4篇 |
矿业工程 | 1篇 |
能源动力 | 1篇 |
轻工业 | 2篇 |
石油天然气 | 1篇 |
武器工业 | 1篇 |
无线电 | 102篇 |
一般工业技术 | 74篇 |
冶金工业 | 5篇 |
自动化技术 | 9篇 |
出版年
2023年 | 7篇 |
2022年 | 4篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 9篇 |
2013年 | 39篇 |
2012年 | 14篇 |
2011年 | 13篇 |
2010年 | 13篇 |
2009年 | 19篇 |
2008年 | 14篇 |
2007年 | 36篇 |
2006年 | 35篇 |
2005年 | 24篇 |
2004年 | 22篇 |
2003年 | 8篇 |
2002年 | 14篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 1篇 |
排序方式: 共有311条查询结果,搜索用时 31 毫秒
301.
Hyun-Suk Kim Il-Doo Kim Ki-Byoung Kim Tae-Soon Yun Jong-Chul Lee Harry L. Tuller Won-Youl Choi Ho-Gi Kim 《Journal of Electroceramics》2006,17(2-4):421-425
We report on high tunablity of Ba0.6Sr0.4TiO3 (BST) thin films realized through the use of atomic layer deposited TiO2 films as a microwave buffer layer between BST and a high resistivity (HR) Si substrate. Coplanar waveguide (CPW) meander-line
phase shifters using BST/TiO2/HR-Si and BST/MgO structures exhibited a differential phase shift of 95∘ and 24.4∘, respectively, at 15 GHz under an electric field of 10 kV/cm. The figure of merit of the phase shifters at 15 GHz was 30.6∘/dB for BST film grown on a TiO2/HR-Si substrate and 12.2∘/dB for BST film grown on a MgO single crystal substrate. These results constitute significant progress in integrating BST
films with conventional silicon technology. 相似文献
302.
《Integrated ferroelectrics》2013,141(1):863-869
Epitaxial (111) oriented ferroelectric (Ba1 ? xSrx)TiO3 (BST) films were deposited on MgO (111) single crystals using pulsed laser deposition. Structural properties of BST films were investigated using X-ray diffractometer. The dielectric properties of BST films were investigated under the dc bias field of 0–40 V using interdigital capacitors (IDT) fabricated by photolithography and etching process. The small signal dielectric properties of BST films were calculated by modified conformal mapping both the measured data using an impedance gain/phase analyzer and the reflection coefficient data measured using a HP 8510C vector network analyzer in 0.05–10 GHz at room temperature. The IDT capacitor based on (111) oriented BST film exhibits about 40% of capacitance change with an dc bias of 40 V which value is somewhat smaller than that of the IDT device based on (001) oriented BST film. But the dielectric quality factor value is about twice that of the device based on (001) oriented BST film. 相似文献
303.
采用传统陶瓷工艺制备了Fe2O3掺杂BST/MgO铁电陶瓷材料。研究了Fe2O3掺杂量对该复合体系εr、tanδ等参数的影响。结果表明,适量的掺杂能有效改善体系的电性能。控制掺杂量x(Fe2O3)为0.1%,陶瓷介质在微波频段(S波段)的εr为100.5;tanδ约为5.3×10–3;4000V/mm偏压下的调谐性可达14.2%。采用极化理论对掺杂机理进行了探讨。 相似文献
304.
采用sol-gel工艺制备了(Ba0.5Sr0.5)TiO3(BST)-SiO2-B2O3系铁电玻璃陶瓷。对其显微结构进行了分析,并通过阻抗分析仪测试其介电温谱(–50~+100℃)。结果表明:SiO2-B2O3系BST铁电玻璃陶瓷的相结构为立方钙钛矿相,显微结构呈微晶结构,当BST相与玻璃相的摩尔比为4:1时,颗粒平均粒径为1.35μm。随着SiO2-B2O3玻璃相含量的增加,εr明显降低,同时居里峰宽化,tC向低温方向移动。 相似文献
305.
罗秋明 《计算机应用与软件》2008,25(1):66-69
分析电路的Protel设计文档中网表文件描述的器件电气连接信息和所采用器件的BSDL文件所描述的边界扫描特性,然后生成逻辑测试向量,再进一步根据网络中驱动与响应点来影射到扫描过程中的测试数据,实现电路中stack-at-1、stack-at-1、短路和开路等故障. 相似文献
306.
Mn-Mg共掺杂对钛酸锶钡薄膜介电性能的影响 总被引:2,自引:0,他引:2
用溶胶-凝胶法在Pt/Ti/SiO 2/Si衬底上制备了系列Mn-Mg共掺杂的钛酸锶钡(Ba 0.25 Sr 0.75 TiO 3)薄膜. X射线衍射以及场发射扫描电镜分析表明: 薄膜为钙钛矿结构且无杂相生成, 薄膜表面晶粒均匀、无裂纹. 测试了不同浓度掺杂薄膜的介电性能, 掺杂浓度为1mol% 时, 薄膜的介电常数、损耗、可调性和漏电流密度分别为200、0.010、38%、1×10-5 A/cm 2. 性能改善后的薄膜材料可以用来制作微波可调器件. 相似文献
307.
308.
309.
Saurabh Tiwari Akshay Gaur Rahul Vaish 《International Journal of Applied Ceramic Technology》2023,20(5):3127-3139
The photocatalytic, sonocatalytic, and sono-photocatalytic performances of Ba0.5Sr0.5TiO3 (BST) ceramic (synthesized through solid-state reaction route) were investigated for the degradation of an organic dye named methylene blue (MB). The as-prepared BST ceramic powder was characterized using a scanning electron microscope, X-ray diffraction, X-ray photoelectron, and Raman spectroscopy techniques. The optical energy band gap of BST ceramic was found to be ∼3.17 eV. BST has shown significant catalytic activity following sonocatalysis and photocatalysis processes, i.e, ∼48% and ∼65% in 3 h, respectively. The synergic effect of the sonocatalysis and photocatalysis processes had shown an excellent degradation of 81% in 3 h. To determine the reactive species responsible for the degradation of MB dye, a scavenger test was also performed using isopropyl alcohol (IPA), ethylenediaminetetraacetic acid (EDTA), and benzoquinone (BQ) scavengers. The degree of MB dye degradation was quantified by a phytotoxicity test on “Vigna radiata” seeds. Furthermore, the potentiality of BST ceramic was explored for water cleaning applications while irradiating it to solar radiation in real-time conditions. 相似文献
310.
《Journal of the European Ceramic Society》2023,43(8):3250-3265
Dense fine-grained Ba0.6Sr0.4TiO3 ceramics with submicronic grains sizes (GS) have been prepared using nanopowders synthesized via sol-gel route and consolidated by Spark Plasma Sintering (SPS). By changing SPS parameters, the GS was reduced from 214 nm to 74 nm. Diffuse ferroelectric-paraelectric phase transitions and low values of dielectric permittivity (<1000) at the Curie temperature (TC ∼280 K) were revealed by Impedance Spectroscopy in all sintered ceramics. The GS reduction from submicron to nanoscale range reflects in a gradually diminishment of dielectric constant, tunability, polarisation and storage energy properties. Raman spectroscopy investigations pointed out the presence of polar nanoclusters above the TC. The short-range polar order is affected by the GS decrease, but becomes more thermally stable. The observed properties of Ba0.6Sr0.4TiO3 nanostructured ceramics are interpreted by considering the interplay between the GS reduction, the role of low-permittivity grain boundaries and the diffuse character of the ferroelectric-to-paraelectric transformation. 相似文献