全文获取类型
收费全文 | 206篇 |
免费 | 24篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 44篇 |
综合类 | 67篇 |
化学工业 | 4篇 |
机械仪表 | 2篇 |
建筑科学 | 2篇 |
矿业工程 | 1篇 |
能源动力 | 2篇 |
轻工业 | 1篇 |
水利工程 | 1篇 |
无线电 | 12篇 |
一般工业技术 | 2篇 |
冶金工业 | 2篇 |
自动化技术 | 104篇 |
出版年
2023年 | 1篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 2篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 1篇 |
2015年 | 6篇 |
2014年 | 16篇 |
2013年 | 50篇 |
2012年 | 9篇 |
2011年 | 7篇 |
2010年 | 15篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 8篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 20篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1982年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有244条查询结果,搜索用时 31 毫秒
71.
S. B. Krupanidhi 《Integrated ferroelectrics》2013,141(2-4):161-180
Abstract Recent developments in ferroelectric thin film deposition involving plasma based approaches, are described, which include a) multi-magnetron sputter deposition, b) Multi-ion-beam reactive sputter (MIBERS) deposition, c) Pulsed excimer laser ablation and d) ECR (Electron cyclotron resonance) plasma assisted deposition. These methods commonly prevailed intrinsic low energy ion bombardment during the growth process, which may be used for the control over composition, crystallization temperature and microstructure. A low energy (60–75 eV) ion bombardment of the ferroelectric Pb(Zr, Ti)O3 thin films indicated a reduction in the phase formation/crystallization temperature, improved the electrical properties, microstructure and the surface smoothness. Discussion is presented exphasizing the effects of low energy bombardment in different deposition processes. Recent findings using rapid thermal annealing process are also described. 相似文献
72.
Abstract Pb(Zh x , Ti1-x )O3(PZT) thin films were deposited on Si substrates using MgTiO3 as the buffer layer and the electrical properties of those MFIS structures were investigated. PZT and MgTiO3 films were made by MOCVD using ultrasonic spraying technique. Perovskite PZT films have been succesfully made at the substrate temperature of 550 to 600°C only when using MgTiO3 buffer layer. AES depth profile analysis and RBS analysis revealed that there is no remarkable interdiffusion and no formation of reaction layer between PZT and MgTiO3 and/or between MgTiO3 and Si substrate. The capacitance-voltage (C-V) curves of the MFIS structure which were made with PZT and MgTiO3buffer layer have shown the hysteresis resulted from the ferroelectric switching of the PZT films. 相似文献
73.
Abstract Ferroelectric PZT/PLZT thin films have been fabricated using the metallo-organic precursor compounds. The structural development, spectroscopic and dielectric properties of these films have been investigated using atomic force microscopy (AFM), X-ray diffraction, Raman scattering and dielectric measurements. Experimental results show that Raman spectroscopy is an effective tool of monitoring the structural development of the small sized PZT films in the tetragonal phase field. Dielectric characteristics have been improved by the rapid thermal processing approach. A rosette growth model is proposed to explain the observation of the tri-intersection of the perovskite phase in PZT films. 相似文献
74.
Li Xiaohui Lin Shengwei Qu Cuifeng Yao Chunhua Jin Qihua 《Integrated ferroelectrics》2013,141(1-3):71-77
Abstract 9 Al2O3·2B2O3 whisker was used to reinforce PZT95/5 type ferroelectric transitional ceramics. The relation between properties (including electric and mechanical properties) and whisker content was studied. Experiment results indicate: Composites with proper whisker content can keep electric properties almost as good as that of base material, while improve mechanical properties effectively. Whisker pulling and bridging play important roles in the process of reinforcing. 相似文献
75.
Wensheng Wang Zhiming Chen Masatoshi Adachi Akira Kawabata 《Integrated ferroelectrics》2013,141(2-4):251-261
Abstract Zr-rich PZT and La-doped PT films were fabricated on a PLT/Pt/Ti/SiO2/Si or Pt/Ti/SiO2/Si substrate by an RF planar magnetron sputtering equipment using powder targets with compositions of PbZr0 94Ti0.06O3, PbZr0.92Ti0.08O3 and Pb0.85La0.15 Ti0.96O3 with excess PbO of 20 mol%. The dielectric constants of PZT and PLT films showed anomalies at the transition temperatures of around 246 and 300°C, and their dielectric constants at room temperature were 350 and 1070, respectively. Significant pytroelectric currents were observed in both as-grown PZT and PLT films even without a poling treatment. The pyroelectric coefficients of those films were 10 and 30 nC/cm2K, respectively. Therefore, Zr-rich PZT and [111]-oriented PLT films sputtered on Pt/Ti/SiO2/Si substrates possess desirable properties for potential applications to pyroelectric devices. 相似文献
76.
提出了一种检测篮球比赛视频中重要音频关键词(短管哨声)的方法。通过分析短管哨声的频谱分布特性提出一种二级检测方法:首先提取特定子带能量峰指数特征,并采用门限决策方法获得关键词候选集;第二级再结合梅尔频率倒谱系数和支持向量机得到最终的关键词检测结果。选取时长为1378s的NBA篮球比赛音频片段作为测试序列.验证了本方法具有正确率和检出率分别为95.45%和91.3%的性能。 相似文献
77.
为了改进传统以向量空间模型(VSM)为代表的基于词频统计的方法在中文段落相似度计算时存在的精度不高问题,在基于加权二部图匹配的思想上提出了一种计算中文段落之间相似度的方法。该方法将相似度计算分为段落和句子两个层次,将句子作为简单段落看待,也使用二部图匹配进行相似度计算。首先利用句子主干词汇提取算法来提取句子的主干词汇,将主干词汇作为二部图的顶点,把主干词汇之间的相似度作为二部图顶点之间的权值系数,进行句子相似度的计算。其次,将句子作为加权二部图的顶点,把句子之间的相似度作为二部图顶点之间的权值系数,进行段落之间的相似度计算。实验结果表明,该方法与VSM相比,由于它能准确识别同义词,自动匹配两个在段落中不同位置的相似词语,因而在准确度上有了很大的提高。 相似文献
78.
针对现有基于语义知识规则分析的文本相似性度量方法存在时间复杂度高的局限性,提出基于分类词典的文本相似性度量方法。利用汉语词法分析系统ICTCLAS对文本分词,运用TF×IDF方法提取文本关键词,遍历分类词典获取关键词编码,通过计算文本关键词编码的近似性来衡量原始文本之间的相似度。选取基于语义知识规则和基于统计两个类别的相似性度量方法作为对比方法,通过传统聚类与KNN分类分别对相似性度量方法进行效果验证。数值实验结果表明,新方法在聚类与分类实验中均能取得较好的实验结果,相较于其他基于语义分析的相似性度量方法还具有良好的时间效率。 相似文献
79.
80.
Xiangfeng Luo Ning Fang Weimin Xu Sheng Yu Kai Yan Huizhe Xiao 《Concurrency and Computation》2008,20(16):1917-1932
Domain keywords of text play a primary role in text classifying, clustering and personalized services. This paper proposes a term frequency inverse document frequency (TFIDF) based method called TDDF (TFIDF direct document frequency of domain) to extract domain keywords from multi‐texts. First, we discuss the optimal parameters of TFIDF, which are used to extract textual keywords and domain keywords. Second, TDDF is proposed to extract domain keywords from multi‐texts, which takes document frequency of domain into account. Finally, the distribution of domain keywords on scientific texts is studied. Experiments and applications show that TDDF is more effective than the optimal TFIDF in the extraction of domain keywords. Domain keywords accord with normal distribution on a single text after deleting the ubiquitous domain keywords. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献