全文获取类型
收费全文 | 37089篇 |
免费 | 3328篇 |
国内免费 | 2779篇 |
学科分类
工业技术 | 43196篇 |
出版年
2024年 | 102篇 |
2023年 | 499篇 |
2022年 | 604篇 |
2021年 | 751篇 |
2020年 | 915篇 |
2019年 | 758篇 |
2018年 | 732篇 |
2017年 | 1002篇 |
2016年 | 1187篇 |
2015年 | 1375篇 |
2014年 | 2059篇 |
2013年 | 2171篇 |
2012年 | 2303篇 |
2011年 | 2684篇 |
2010年 | 2107篇 |
2009年 | 2588篇 |
2008年 | 2775篇 |
2007年 | 2805篇 |
2006年 | 2467篇 |
2005年 | 2210篇 |
2004年 | 1902篇 |
2003年 | 1806篇 |
2002年 | 1536篇 |
2001年 | 1219篇 |
2000年 | 1075篇 |
1999年 | 785篇 |
1998年 | 600篇 |
1997年 | 500篇 |
1996年 | 398篇 |
1995年 | 311篇 |
1994年 | 228篇 |
1993年 | 188篇 |
1992年 | 130篇 |
1991年 | 78篇 |
1990年 | 54篇 |
1989年 | 46篇 |
1988年 | 33篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 43篇 |
1984年 | 39篇 |
1983年 | 36篇 |
1982年 | 40篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
S. F. Edwards 《Polymer International》1985,17(2):122-125
Elasticity is discussed as an aspect of viscoelasticity, which is described by the tube model. The effects of both crosslinks and entanglements contribute to this model and a discussion of how these effects can be quantified is given. At high enough concentration, entanglements ensure the existence of elastic effects even without crosslinks, and a theory is presented on how this dynamical phase change comes about. 相似文献
82.
83.
Generation of Technology-Independent Retargetable Analog Blocks 总被引:1,自引:0,他引:1
R. Castro-López F. V. Fernández F. Medeiro A. Rodríguez-Vázquez 《Analog Integrated Circuits and Signal Processing》2002,33(2):157-170
This paper introduces a complete methodology for retargeting of analog cells to different sets of specifications. This methodology is technology-independent, thus allowing the migration, from one technology to another, of the circuit under retargeting. Careful integration of the device sizing and layout generation tasks via the incorporation of layout constraints during the sizing process allows to generate fully functional designs in a few minutes. The methodology is illustrated via the retargeting of a fully-differential Miller-compensated two-stage operational amplifier for a new set of specifications and two different technological processes.An erratum to this article can be found at 相似文献
84.
85.
E.A. Soliman A.K. Abdelmageed M.A. El-Gamal 《AEUE-International Journal of Electronics and Communications》2002,56(3)
In this paper a new artificial neural network (ANN) based model for the calculation of the method of moments (MoM) matrix elements is presented. Training sets that characterize the matrix elements are first constructed. These sets are then utilized to effectively train two radial basis function (RBF) neural networks to accurately estimate all the elements of the MoM matrix for any mesh used. The potential of the proposed approach is demonstrated in the case of a narrow microstrip line. The current distribution on the microstrip line produced by the trained RBF networks agrees very well with the exact distribution. In addition, the proposed ANN model is much faster than the conventional MoM procedure. 相似文献
86.
87.
Adaptive motion control using neural network approximations 总被引:1,自引:0,他引:1
In this paper, we present a new adaptive technique for tracking control of mechanical systems in the presence of friction and periodic disturbances. Radial Basis Functions (RBFs) are used to compensate for the effects of nonlinearly occurring parameters in the friction and periodic disturbance model. Theoretical analysis, such as stability and transient performance, is provided. Furthermore, the performance of the adaptive RBF controller and its non-adaptive counterpart are compared. 相似文献
88.
Multi-valued and universal binary neurons (MVN and UBN) are the neural processing elements with the complex-valued weights and high functionality. It is possible to implement an arbitrary mapping described by partially defined multiple-valued function on the single MVN. An arbitrary mapping described by partially defined or fully defined Boolean function, which can be non-threshold, may be implemented on the single UBN. The quickly converging learning algorithms exist for both types of neurons. Such features of the MVN and UBN may be used for solving the different problems. One of the most successful applications of the MVN and UBN is their usage as basic neurons in the Cellular Neural Networks (CNN). It opens the new effective opportunities in nonlinear image filtering and its applications to noise reduction, edge detection and solving of the super resolution problem. A number of experimental results are presented to illustrate the performance of the proposed algorithms.An erratum to this article can be found at 相似文献
89.
Paul J. Flory 《Polymer International》1985,17(2):96-102
The earliest investigations on rubber elasticity, commencing in the 19th century, were necessarily limited to phenomenological interpretations. The realisation that polymers consist of very long molecular chains. commencing c. 1930, gave impetus to the molecular theory of rubber elasticity (1932-). according to which the high deformability of an elastomer, and the elastic force generated by deformation, stem from the configurations accessible to long molecular chains. Theories of rubber elasticity put forward from 1934-1946 relied on the assumption that the junctions of the rubber network undergo displacements that are affine in macroscopic strain. The theory of James and Guth (1947) dispensed with this premise, and demonstrated instead that the mean positions of the junctions of a ‘phantom’ network consisting of Gaussian chains devoid of material properties are affine in the strain. The vital significance of the distinction between the actual distribution of chain vectors in a network and their distribution if the junctions would be fixed at their mean positions went unnoticed for nearly 30 years. Experimental investigations, commencing with the incisive work of Gee in 1946. revealed large departures from the relationship of stress to strain predicted by the theories cited. This discrepancy prompted extensive studies, theoretical and experimental, during succeeding years. Inquiry into the fundamentals of polymer networks, formed for example by interlinking very long polymer molecules, exposed the need to take account of network imperfections, typically consisting of chains attached at only one end to a network junction. Various means were advocated to make corrections for these imperfections. The cycle rank ζ of the network has been shown (1976) to be the fundamental measure of its connectivity, regardless of the junction functionality and pattern of imperfections. Often overlooked is the copious interpenetration of the chains comprising typical elastomeric networks. Theories that attempt to represent such networks on a lattice are incompatible with this universal feature. Moreover, the dense interpenetration of chains may limit the ability of junctions in real networks to accommodate the fluctuations envisaged in the theory of phantom networks. It was suggested in 1975 that departures from the form predicted for the elastic equation of state are due to constraints on the fluctuations of junctions whose effect diminishes with deformation and with dilation. Formulation of a self-consistent theory based on this suggestion required recognition of the non-affine connection between the chain vector distribution function and the macroscopic strain in a real network, which may partake of characteristics of a phantom network in some degree. Implementation of the idea was achieved through postulation of domains of constraint affecting the equilibrium distribution of fluctuations of network junctions from their mean positions. This led in due course to a theory that accounts for the relationship of stress to strain virtually throughout the ranges of strain accessible to measurement. The theory establishes connections between structure and elastic properties. This is achieved with utmost frugality in arbitrary parameters. 相似文献
90.
Effects of modeling means on properties of monitoring models of spot welding quality 总被引:1,自引:0,他引:1
Analyzing and modeling the relation between monitoring information during welding and quality information of the joints is the foundation of monitoring resistance spot welding quality. According to the means of modeling, the known models can be divided into three large categories: single linear regression models, multiple linear regression models and multiple non-linear models. By modeling the relations between dynamic resistance information and welding quality parameters with different means, this paper analyzes effects of modeling means on performances of monitoring models of resistance spot welding quality. From the test results, the following conclusions can be drawn: By comparison with two other kinds of models, artificial neural network (ANN) model can describe non-linear and high coupling relationship between monitoring information and quality information more reasonably, improve performance of monitoring model remarkably, and make the estimated values of welding quality parameters more accurate and reliable. 相似文献