全文获取类型
收费全文 | 193篇 |
免费 | 38篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 17篇 |
化学工业 | 51篇 |
金属工艺 | 3篇 |
机械仪表 | 4篇 |
建筑科学 | 5篇 |
能源动力 | 3篇 |
轻工业 | 16篇 |
石油天然气 | 2篇 |
无线电 | 26篇 |
一般工业技术 | 36篇 |
冶金工业 | 10篇 |
原子能技术 | 1篇 |
自动化技术 | 58篇 |
出版年
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 17篇 |
2017年 | 5篇 |
2016年 | 17篇 |
2015年 | 13篇 |
2014年 | 21篇 |
2013年 | 18篇 |
2012年 | 17篇 |
2011年 | 21篇 |
2010年 | 7篇 |
2009年 | 5篇 |
2008年 | 13篇 |
2007年 | 3篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1977年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有232条查询结果,搜索用时 15 毫秒
1.
Simulation‐based optimization has become an important design tool in microwave engineering. However, using electromagnetic (EM) solvers in the design process is a challenging task, primarily due to a high‐computational cost of an accurate EM simulation. In this article, we present a review of EM‐based design optimization techniques exploiting response‐corrected physically based low‐fidelity models. The surrogate models created through such a correction can be used to yield a reasonable approximation of the optimal design of the computationally expensive structure under consideration (high‐fidelity model). Several approaches using this idea are reviewed including output space mapping, manifold mapping, adaptive response correction, and shape‐preserving response prediction. A common feature of these methods is that they are easy to implement and computationally efficient. Application examples are provided. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012. 相似文献
2.
A computationally efficient algorithm for electromagnetic (EM)‐simulation‐driven design optimization of microwave structures is proposed. Our technique exploits variable‐fidelity EM simulations and the multilevel design approach where an approximate optimum of the lower accuracy but faster EM model of the structure under design is used as a starting point for optimizing a more accurate model. Several enhancements of the basic multifidelity method are introduced, including an efficient algorithm of optimizing EM models that is based on local response surface approximations, as well as automated adjustment of model fidelity. Convergence of the procedure to the optimum design is ensured by defaulting to the higher fidelity model whenever the prediction given by the lower fidelity fails to improve the design. Distribution of the computational effort between the models of different fidelity allows for making larger steps in the design space at a low cost, as well as substantial reduction of the number of high‐fidelity model evaluations, because the high‐fidelity model is only referred to in the last design stage. The article provides comprehensive numerical verification of our technique. Substantial computational savings are demonstrated in comparison to the benchmark methods: over 40% on average as compared to a basic version of the multifidelity optimization approach and over 95% as compared to direct optimization of the high‐fidelity model. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:281–288, 2014. 相似文献
3.
Julian Chojnowski Slawomir Rubinsztajn Witold Fortuniak Jan Kurjata 《Journal of Inorganic and Organometallic Polymers and Materials》2007,17(1):173-187
Summary Reactions of hexamethylcyclotrisiloxane, D3, with 1,1,3,3-tetramethyldisiloxane, HMMH, 1,1,1,3,3-pentamethyldisiloxane, HMM, phenyldimethylsilane and phenylmethylsilane catalyzed by tris(pentafluorophenyl)borane were studied. These reactions lead
to ring opening of D3 by the SiH reactant producing open chain oligomers with hydrosilane functionality at one or both chain ends. The reactivity
of the hydrosilanes toward D3 decreases in the series: PhMeSiH2 > HMMH > PhMe2SiH > HMM. Competitive self-oligomerization of HMMH and HMM also occurs. Primary products of these processes are able to enter into reactions with the SiH and D3 reactants; some also undergo cyclization. Thus, consecutive and competitive processes lead to a series of various oligohomologues.
Gas chromatography in conjunction with chemical ionization mass spectroscopy permitted identification of structure and determination
of the basic directions of these oligomerization processes. Polysiloxanes of higher molecular weight may be also formed in
some of these systems. The reactions, which occur in the systems studied, are rationalized on the basis of the mechanism involving
the hydride transfer from silicon to trivalent boron. This includes the transient formation of tertiary trisilyloxonium borate
which decomposes by the hydride transfer to one of the silicon atoms of the trisilyloxonium center.
Footnote: This paper is dedicated to Professor Ian Manners in recognition of his significant contributions to the field of
organometallic polymers. 相似文献
4.
Maciej Klis Agnieszka Michota Slawomir Sek Renata Bilewicz 《Electrochimica acta》2007,52(18):5591-5598
Cerrena unicolor laccase was immobilized on the gold electrode by covalent bonding to self-assembled monolayers of mercaptoundecanoic or mercaptopropionic acids. STM images of immobilized laccase proved high population of the laccase molecules on the monolayer modified electrode. The SERS experiments in concert with resonance Raman effect confirmed that the structure at the “blue” copper site of the immobilized protein remained intact. The accessibility of individual copper sites for electron exchange with the gold electrode surface was investigated by voltammetry. The electrode behavior of laccase is different in the presence and absence of oxygen, showing that the immobilized enzyme is reactive towards oxygen. Addition of two common mediators improved the electrical connectivity of the enzyme with the electrode, increased the catalytic efficiency of immobilized laccase and switched the onset of catalytic current to the potentials of the mediator. Immobilization of laccase on well-organized mercaptoundecanoic acid separates efficiently the enzyme from the electrode and does not allow easy access of mediators to the surface. Attachment of the enzyme at smaller distance from the electrode by means of significantly shorter spacer molecule—mercaptopropionic acid improved the efficiency of catalytic reduction of oxygen on the monolayer modified electrode. 相似文献
5.
In this work, the issues of bandwidth enhancement of planar antennas and the relevance of precise and automated response control through numerical optimization have been investigated. Using an example of a planar antenna with parasitic radiator we illustrate possible effects of even minor modifications of the antenna geometry (here, applied to the ground plane) on its reflection performance. In particular, a proper handling of geometry parameters may lead to considerable broadening of the antenna bandwidth. For the sake of computational efficiency, the adjustment of geometry parameters is carried out using surrogate‐based optimization methods exploiting coarse‐discretization EM simulations as the underlying low‐fidelity antenna model. Additionally, suitably defined penalty function allows us to precisely control the maximum in‐band reflection so that sufficient margin to accommodate possible manufacturing tolerances can be achieved. The optimized designs of the two antenna structures considered in this work exhibit over 1.75 GHz (>31%) and 2.15 GHz (>38%) bandwidth, respectively, for the center frequency of 5.6 GHz. Simulation results are validated using measurements of the fabricated prototypes. Comparison with state‐of‐the‐art designs is also provided. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:653–659, 2016. 相似文献
6.
Slawomir J. Ambroziak Ryszard J. Katulski Jaroslaw Sadowski Jacek Stefanski 《通讯和计算机》2013,(9):1247-1252
The aim of this paper is the path loss modelling for the radiolocation services in radio communication networks, particularly in cellular networks. The main results of the measurements obtained in the physical layer of the UMTS are introduced. A new method for the utilization of the multipath propagation phenomenon to improve the estimation of the distance between the MS (mobile station) and the BS (base station) is outlined. This method significantly increases the quality of location services in systems which use a radio interface with DS (direct sequence) CDMA (code division multiple access). 相似文献
7.
Slawomir Pilarski 《Journal of Electronic Testing》1995,6(1):139-140
The analysis of aliasing probability presented in a recent article, Aliasing Properties of Circular MISRs [1], is based on an error model that cannot adequately represent real circuits. We show why conclusions presented in [1] should not be used in practice, substantiating our claim with experimental results.This work was supported in part by grants from the Natural Sciences and Engineering Research Council of Canada and in part by the British Columbia Advanced Systems Institute 相似文献
8.
Expedited simulation‐driven design optimization of UWB antennas by means of response features 下载免费PDF全文
In this work, a method for fast design optimization of broadband antennas is considered. The approach is based on a feature‐based optimization (FBO) concept where reflection characteristics of the structure at hand are formulated in terms of suitably defined feature points. Redefinition of the design problem allows for reducing the design optimization cost, because the dependence of feature point coordinates on antenna dimensions is less nonlinear than for the original frequency characteristics (here, S‐parameters). This results in faster convergence of the optimization algorithm. The cost of the design process is further reduced using variable‐fidelity electromagnetic (EM) simulation models. In case of UWB antennas, the feature points are defined, among others, as the levels of the reflection characteristic at its local in‐band maxima, as well as location of the frequency point which corresponds to acceptable reflection around the lower corner frequency within the UWB band. Also, the number of characteristic points depends on antenna topology and its dimensions. Performance of FBO‐based design optimization is demonstrated using two examples of planar UWB antennas. Moreover, the computational cost of the approach is compared with conventional optimization driven by a pattern search algorithm. Experimental validation of the numerical results is also provided. 相似文献
9.
Slawomir Koziel Stanislaw Szczepanski Rolf Schaumann 《International Journal of Circuit Theory and Applications》2004,32(6):565-589
Starting from a set of matrices describing a general Gm‐C filter topology, a procedure is developed for generating structures of lowpass filters. As the matrices and the filter topologies have a one‐to‐one correspondence, an algebraic method is used to identify filter topologies with desired properties, here, transfer functions with finite jω‐axis transmission zeros, specifically elliptic filters. Sensitivity expressions for these structures are derived and a performance comparison based on a set of chosen criteria is made. For a specified elliptic transfer function, filters with only grounded capacitors and those containing also floating capacitors emerge as alternative realizations, as are filters with a single input and those with distributed inputs. For third‐order functions, a detailed comparison is performed of leapfrog (LF) and inverse follow‐the‐leader‐feedback (IFLF), the most popular special cases, and of topologies that have also floating capacitors (LFf, IFLFf), as well as of a novel configuration that uses also distributed inputs (DIf) and leads to a reduced element count. Design guidelines and restrictions are given, which follow from the derived results with focus on the circuits' sensitivity performance and other properties important for IC implementation. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
10.
Multi‐objective design optimization of antennas for reflection,size, and gain variability using kriging surrogates and generalized domain segmentation 下载免费PDF全文
Cost‐efficient multi‐objective design optimization of antennas is presented. The framework exploits auxiliary data‐driven surrogates, a multi‐objective evolutionary algorithm for initial Pareto front identification, response correction techniques for design refinement, as well as generalized domain segmentation. The purpose of this last mechanism is to reduce the volume of the design space region that needs to be sampled in order to construct the surrogate model, and, consequently, limit the number of training data points required. The recently introduced segmentation concept is generalized here to allow for handling an arbitrary number of design objectives. Its operation is illustrated using an ultra‐wideband monopole optimized for best in‐band reflection, minimum gain variability, and minimum size. When compared with conventional surrogate‐based approach, segmentation leads to reduction of the initial Pareto identification cost by over 20%. Numerical results are supported by experimental validation of the selected Pareto‐optimal antenna designs. 相似文献