全文获取类型
收费全文 | 844篇 |
免费 | 26篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 5篇 |
综合类 | 1篇 |
化学工业 | 206篇 |
金属工艺 | 21篇 |
机械仪表 | 19篇 |
建筑科学 | 17篇 |
矿业工程 | 1篇 |
能源动力 | 30篇 |
轻工业 | 34篇 |
水利工程 | 1篇 |
石油天然气 | 7篇 |
无线电 | 97篇 |
一般工业技术 | 231篇 |
冶金工业 | 48篇 |
原子能技术 | 12篇 |
自动化技术 | 142篇 |
出版年
2024年 | 5篇 |
2022年 | 16篇 |
2021年 | 25篇 |
2020年 | 19篇 |
2019年 | 28篇 |
2018年 | 30篇 |
2017年 | 29篇 |
2016年 | 28篇 |
2015年 | 13篇 |
2014年 | 21篇 |
2013年 | 59篇 |
2012年 | 28篇 |
2011年 | 49篇 |
2010年 | 34篇 |
2009年 | 26篇 |
2008年 | 26篇 |
2007年 | 21篇 |
2006年 | 19篇 |
2005年 | 17篇 |
2004年 | 19篇 |
2003年 | 20篇 |
2002年 | 10篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 16篇 |
1998年 | 18篇 |
1997年 | 23篇 |
1996年 | 13篇 |
1995年 | 20篇 |
1994年 | 17篇 |
1993年 | 19篇 |
1992年 | 25篇 |
1991年 | 15篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1971年 | 3篇 |
排序方式: 共有872条查询结果,搜索用时 15 毫秒
1.
Human faces undergo considerable amounts of varialions with aging. While face recognition systems have been proven to be sensitive to factors such as illumination and pose, their sensitivity to facial aging effects is yet to be studied. How does age progression affect the similarity between a pair of face images of an individual? What is the confidence associated with establishing the identity between a pair of age separated face images? In this paper, we develop a Bayesian age difference classifier that classifies face images of individuals based on age differences and performs face verification across age progression. Further, we study the similarity of faces across age progression. Since age separated face images invariably differ in illumination and pose, we propose preprocessing methods for minimizing such variations. Experimental results using a database comprising of pairs of face images that were retrieved from the passports of 465 individuals are presented. The verification system for faces separated by as many as nine years, attains an equal error rate of 8.5%. 相似文献
2.
Al-Li alloys being developed as lighter, substitutes for conventional high strength Al alloys are to be processed by routine
methods. During extrusion of a 8090 Al-Li alloy, the extrusion die container failed causing some alarm. This failed die container
was analysed to examine if the failure was caused by interaction of Li diffusing out of Al-Li alloy with the carbides of die
steel. The evidence, although not conclusive, is sufficient to exercise caution during such processing. 相似文献
3.
This paper presents a general framework for combined source-channel coding within the context of subband coding. The unequal importance of subbands in reconstruction of the source is exploited by an appropriate allocation of source and channel coding rates for the coding and transmission of subbands over a noisy channel. For each subband, the source coding rate as well as the level of protection (quantified by the channel coding rate) are jointly chosen to minimize the total end-to-end mean-squared distortion suffered by the source. This allocation of source and channel coding rates is posed as a constrained optimization problem, and solved using a generalized bit allocation algorithm. The optimal choice of source and channel coding rates depends on the state of the physical channel. These results are extended to transmission over fading channels using a finite state model, where every state corresponds to an additive white Gaussian noise (AWGN) channel. A coding strategy is also developed that minimizes the average distortion when the channel state is unavailable at the transmitter. Experimental results are provided that demonstrate application of these combined source-channel coding strategies on video sequences 相似文献
4.
A. A. Arafa Rama Subba Reddy Gorla 《International Journal of Engineering Science》1992,30(12):1745-1751
An analysis is presented to investigate the effects of buoyancy and curvature on convection along vertical cylinders and needles placed in a micropolar fluid. The governing equations for momentum, angular momentum and energy are solved numerically by finite difference scheme. The heat transfer results are presented for a range of values of the buoyancy parameters, the curvature parameter and the material parameters of the fluid. The effect of the microrotation boundary conditions on heat transfer is discussed. 相似文献
5.
In this paper, the problem of simultaneous structure from motion estimation for multiple independently moving objects from a monocular image sequence is addressed. Two Bayesian algorithms are presented for solving this problem using the sequential importance sampling (SIS) technique. The empirical posterior distribution of object motion and feature separation parameters is approximated by weighted samples. The first algorithm addresses the problem when only two moving objects are present. A singular value decomposition (SVD)-based sample clustering algorithm is shown to be capable of separating samples related to different objects. A pair of SIS procedures is used to track the posterior distribution of the motion parameters. In the second algorithm, a balancing step is added into the SIS procedure to preserve samples of low weights so that all objects have enough samples to propagate empirical motion distributions. By using the proposed algorithms, the relative motions of all the moving objects with respect to the camera can be simultaneously estimated. Both algorithms have been tested on synthetic and real-image sequences. Improved results have been achieved. 相似文献
6.
7.
Synthesis and characterization of acidic properties of Al-SBA-15 materials with varying Si/Al ratios
G. Muthu Kumaran Shelu Garg Kapil Soni Manoj Kumar J.K. Gupta L.D. Sharma K.S. Rama Rao G. Murali Dhar 《Microporous and mesoporous materials》2008,114(1-3):103-109
Al-SBA-15 of varying Si/Al ratios in the range 11.4–78.4 was synthesized using tri-block copolymer P123. The calcined materials were examined by XRD, pore size distribution, surface area, 27Al NMR spectroscopy. The acidity and acid strength distribution were studied using microcalorimetric adsorption of NH3. The acidic properties were also examined by cumene cracking reaction as a function of Si/Al ratios. Systematic variation of acidity and activity was observed as a function of Si/Al ratio. The initial heats of NH3 adsorption correlated well with activity indicate that acid sites with ΔH > 100 kJ/mole is responsible for cumene cracking activity. Linear correlations were obtained with total acidity and cumene cracking activities. The tetrahedral aluminum was found to be responsible for the observed acidities and catalytic activities. 相似文献
8.
Multimedia signal processing is more than simply “putting together” text, audio, images, and video. It is the integration and interaction among these different media that creates new systems and new research challenges and opportunities. In multimodal communication where speech is involved, audio-visual interaction is particularly significant 相似文献
9.
K V S Rama Rao 《Bulletin of Materials Science》1993,16(6):491-499
Pseudobinary alloy, Tb0·27Dy0·73Fe2−δ
, belonging to C-15 cubic Laves phase having MgCu2-type structure, possesses large magnetostriction and high magnetomechanical coupling coefficient. The advantages of this
material over existing piezoelectric materials, particularly for SONAR applications, are highlighted. Recent results on the
influence of cobalt (Co) on magnetic and magnetomechanical properties of Tb0·27Dy0·73Fe2 are discussed. 相似文献
10.
Bright red luminescent Eu3+ doped polyvinyl alcohol (PVA) films were made by solution casting technique. The emission performance of these films was studied from the measurement of excitation, emission, and lifetimes. On irradiation with an UV source, the doped films emitted bright red light. Such luminescent polymer films are expected to find potential applications as new optical materials. Emission process in the system was explained by an energy level scheme. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3273–3276, 2006 相似文献