全文获取类型
收费全文 | 61023篇 |
免费 | 6362篇 |
国内免费 | 4429篇 |
专业分类
电工技术 | 4624篇 |
技术理论 | 1篇 |
综合类 | 5064篇 |
化学工业 | 2922篇 |
金属工艺 | 996篇 |
机械仪表 | 4948篇 |
建筑科学 | 1102篇 |
矿业工程 | 1204篇 |
能源动力 | 826篇 |
轻工业 | 919篇 |
水利工程 | 442篇 |
石油天然气 | 496篇 |
武器工业 | 530篇 |
无线电 | 15448篇 |
一般工业技术 | 3839篇 |
冶金工业 | 621篇 |
原子能技术 | 131篇 |
自动化技术 | 27701篇 |
出版年
2024年 | 245篇 |
2023年 | 916篇 |
2022年 | 1300篇 |
2021年 | 1588篇 |
2020年 | 1778篇 |
2019年 | 1472篇 |
2018年 | 1338篇 |
2017年 | 2157篇 |
2016年 | 2409篇 |
2015年 | 2982篇 |
2014年 | 4298篇 |
2013年 | 4135篇 |
2012年 | 4967篇 |
2011年 | 5383篇 |
2010年 | 3707篇 |
2009年 | 4158篇 |
2008年 | 4265篇 |
2007年 | 4375篇 |
2006年 | 3612篇 |
2005年 | 2857篇 |
2004年 | 2374篇 |
2003年 | 2090篇 |
2002年 | 1687篇 |
2001年 | 1425篇 |
2000年 | 1212篇 |
1999年 | 959篇 |
1998年 | 805篇 |
1997年 | 860篇 |
1996年 | 585篇 |
1995年 | 464篇 |
1994年 | 354篇 |
1993年 | 270篇 |
1992年 | 202篇 |
1991年 | 141篇 |
1990年 | 98篇 |
1989年 | 61篇 |
1988年 | 48篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 43篇 |
1984年 | 44篇 |
1983年 | 39篇 |
1982年 | 41篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
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
102.
103.
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
104.
基于充放电原理实现的微电容测量电路 总被引:1,自引:0,他引:1
具有抗分布电容以及简单实用等特性的充放电电路是目前微电容测量中广泛采用的一种测量电路。本文对基于充放电原理的微电容测量电路进行了深入研究,并介绍一种基于充放电原理的实用电路。 相似文献
105.
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
106.
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
107.
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
108.
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
109.
枪械振动测试包含刚体线位移和角位移六维运动参数.其测试方法是,将光电传感器光源与被测体固结在一起,通过求解光源在三个投影屏上随着被测体运动变化的数学模型而实现的.该传感器由激光器、投影屏、光电探测器件及处理电路、数据采集、数据处理等部分组成.并以固结在被测体上的三个激光器的交点为基点,建立其线位移数学模型;以方向余弦法来确定被测体的角位移,建立其角位移数学模型. 相似文献
110.