全文获取类型
收费全文 | 2275篇 |
免费 | 25篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 11篇 |
综合类 | 1篇 |
化学工业 | 90篇 |
金属工艺 | 3篇 |
机械仪表 | 12篇 |
建筑科学 | 37篇 |
能源动力 | 17篇 |
轻工业 | 28篇 |
石油天然气 | 4篇 |
无线电 | 285篇 |
一般工业技术 | 121篇 |
冶金工业 | 1558篇 |
原子能技术 | 10篇 |
自动化技术 | 136篇 |
出版年
2023年 | 5篇 |
2022年 | 2篇 |
2021年 | 9篇 |
2020年 | 14篇 |
2019年 | 11篇 |
2018年 | 16篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 22篇 |
2014年 | 19篇 |
2013年 | 37篇 |
2012年 | 23篇 |
2011年 | 41篇 |
2010年 | 23篇 |
2009年 | 38篇 |
2008年 | 38篇 |
2007年 | 35篇 |
2006年 | 28篇 |
2005年 | 30篇 |
2004年 | 23篇 |
2003年 | 46篇 |
2002年 | 20篇 |
2001年 | 26篇 |
2000年 | 36篇 |
1999年 | 59篇 |
1998年 | 518篇 |
1997年 | 305篇 |
1996年 | 195篇 |
1995年 | 101篇 |
1994年 | 98篇 |
1993年 | 98篇 |
1992年 | 16篇 |
1991年 | 32篇 |
1990年 | 25篇 |
1989年 | 39篇 |
1988年 | 35篇 |
1987年 | 34篇 |
1986年 | 25篇 |
1985年 | 28篇 |
1984年 | 11篇 |
1983年 | 15篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 25篇 |
1976年 | 47篇 |
1975年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有2313条查询结果,搜索用时 114 毫秒
121.
We study the effects of a random rough surface on the power absorption between a dielectric and conductive medium in a 3-D configuration where the surface height varies in both horizontal directions. The analytic small perturbation method of second order and numerical T-matrix method are used. The absorption depends on the root mean square height, correlation length, and correlation function of the random rough surface. A closed-form expression of power absorption enhancement factor is obtained from small perturbation method of second order. Results show that the T-matrix method agrees with the small perturbation method for rough surfaces with a small slope. We further compare the 3-D results to the previous 2-D results and show significant difference. The power absorption enhancement factor exhibits saturation for the Gaussian correlation function, but not for the exponential correlation function 相似文献
122.
Xiaoxiong Gu Leung Tsang Braunisch H. 《Microwave and Wireless Components Letters, IEEE》2007,17(7):486-488
We present a methodology for extracting the 2D power spectral density of a statistically isotropic random rough surface from height measurements by utilizing fast Fourier-Bessel transform. We compute the additional propagation loss due to surface roughness by integrating the extracted spectral density via the formula of absorption enhancement factor. Results for a microstrip demonstrate good correlation between measured and estimated loss up to 20 GHz. It is also possible to choose a random rough surface model for the measured surface and use it to predict the roughness effect on power loss. 相似文献
123.
High Sensitivity,Wearable, Piezoresistive Pressure Sensors Based on Irregular Microhump Structures and Its Applications in Body Motion Sensing
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zongrong Wang Shan Wang Jifang Zeng Xiaochen Ren Adrian J. Y. Chee Billy Y. S. Yiu Wai Choi Chung Yong Yang Alfred C. H. Yu Robert C. Roberts Anderson C. O. Tsang Kwok Wing Chow Paddy K. L. Chan 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(28):3827-3836
A pressure sensor based on irregular microhump patterns has been proposed and developed. The devices show high sensitivity and broad operating pressure regime while comparing with regular micropattern devices. Finite element analysis (FEA) is utilized to confirm the sensing mechanism and predict the performance of the pressure sensor based on the microhump structures. Silicon carbide sandpaper is employed as the mold to develop polydimethylsiloxane (PDMS) microhump patterns with various sizes. The active layer of the piezoresistive pressure sensor is developed by spin coating PEDOT:PSS on top of the patterned PDMS. The devices show an averaged sensitivity as high as 851 kPa?1, broad operating pressure range (20 kPa), low operating power (100 nW), and fast response speed (6.7 kHz). Owing to their flexible properties, the devices are applied to human body motion sensing and radial artery pulse. These flexible high sensitivity devices show great potential in the next generation of smart sensors for robotics, real‐time health monitoring, and biomedical applications. 相似文献
124.
Xile Wei Meili Lu Jiang Wang K.M. Tsang Bin Deng Yanqiu Che 《International journal of control》2013,86(5):1009-1024
We consider the assumption of existence of the general nonlinear internal model that is introduced in the design of robust output regulators for a class of minimum-phase nonlinear systems with rth degree (r ≥ 2). The robust output regulation problem can be converted into a robust stabilisation problem of an augmented system consisting of the given plant and a high-gain nonlinear internal model, perfectly reproducing the bounded including not only periodic but also nonperiodic exogenous signal from a nonlinear system, which satisfies some general immersion assumption. The state feedback controller is designed to guarantee the asymptotic convergence of system errors to zero manifold. Furthermore, the proposed scheme makes use of output feedback dynamic controller that only processes information from the regulated output error by using high-gain observer to robustly estimate the derivatives of the regulated output error. The stabilisation analysis of the resulting closed-loop systems leads to regional as well as semi-global robust output regulation achieved for some appointed initial condition in the state space, for all possible values of the uncertain parameter vector and the exogenous signal, ranging over an arbitrary compact set. 相似文献
125.
Conrad Nicole J.; Walsh Jennifer; Allen Jennifer M.; Tsang Christine D. 《Canadian Metallurgical Quarterly》2011,65(3):168
Caregivers around the world sing to their infants. Infants not only prefer to listen to infant-directed singing over adult-directed singing, but infant-directed singing also serves a function, communicating affective information to preverbal infants to aid in adjusting arousal levels. Pitch variation has previously been identified as one performance feature that may help to convey the message. Earlier research has indicated that infants' pitch preferences are context dependent, suggesting that infants are tuned in to the communicative intent of infant-directed singing. However, there are several other performance-based features present in infant-directed singing that may also contribute to the affective message. The current study examined the role of context on infants' tempo preferences in sung playsongs and lullabies. Using a head-turn preference procedure, we measured 24 preverbal infants' natural preferences for foreign language playsongs and lullabies as a function of tempo. Infants showed a preference for fast over slow tempo playsongs, but no such context dependent preference was found within lullabies. Results partially support the role of tempo as a communicative feature of infant directed singing. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
126.
Defects embedded in externally-bonded CFRP-concrete composite structures reduce the interfacial bond strength and durability. This paper classifies these defects into two types: flaws and delaminations. Flaws are formed during the first application of the CFRP strips onto the concrete surface due to poor workmanship. Delaminations are formed due to stress concentrations related to chemical/physical degradation of the binding layer. In this study, an aggressive environment was simulated by placing the specimens in water baths with elevated temperatures (40 °C and 60 °C). The sizes of the CFRP-flaws and delaminations were determined by (i) quantitative infrared thermography (QIRT) and (ii) processing of visual images after opening-up the CFRP by direct shear. Experimental results show that apparent flaw sizes determined by QIRT were in good agreement (88% accuracy) with actual flaw sizes determined by the image processing method. The results also show that flaws exhibited little change but the bonding layer showed significant deterioration after exposure to high water temperatures. 相似文献
127.
Wang X.-Z. Yeung D.S. Tsang E.C.C. 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2001,31(2):215-226
Fuzzy decision tree induction is an important way of learning from examples with fuzzy representation. Since the construction of optimal fuzzy decision tree is NP-hard, the research on heuristic algorithms is necessary. In this paper, three heuristic algorithms for generating fuzzy decision trees are analyzed and compared. One of them is proposed by the authors. The comparisons are twofold. One is the analytic comparison based on expanded attribute selection and reasoning mechanism; the other is the experimental comparison based on the size of generated trees and learning accuracy. The purpose of this study is to explore comparative strengths and weaknesses of the three heuristics and to show some useful guidelines on how to choose an appropriate heuristic for a particular problem. 相似文献
128.
129.
130.
Kim-Fung Tsang Wei Shen Sai-Kit Kwok Chow Y.L. 《Microwave and Wireless Components Letters, IEEE》2005,15(12):901-903
The near-field capacitive couplings are analyzed by using a hybrid method incorporating the finite difference method and the method of moment. A dielectric post is used as the model for analysis. Results from the formerly developed technique of synthetic asymptote are used for comparison. The speed of computation of the developed method is extremely fast. 相似文献