全文获取类型
收费全文 | 11218篇 |
免费 | 1412篇 |
国内免费 | 514篇 |
专业分类
化学 | 968篇 |
晶体学 | 5篇 |
力学 | 634篇 |
综合类 | 115篇 |
数学 | 2918篇 |
物理学 | 2055篇 |
无线电 | 6449篇 |
出版年
2024年 | 21篇 |
2023年 | 154篇 |
2022年 | 218篇 |
2021年 | 278篇 |
2020年 | 324篇 |
2019年 | 245篇 |
2018年 | 273篇 |
2017年 | 402篇 |
2016年 | 517篇 |
2015年 | 463篇 |
2014年 | 788篇 |
2013年 | 822篇 |
2012年 | 810篇 |
2011年 | 753篇 |
2010年 | 602篇 |
2009年 | 619篇 |
2008年 | 657篇 |
2007年 | 710篇 |
2006年 | 668篇 |
2005年 | 573篇 |
2004年 | 462篇 |
2003年 | 472篇 |
2002年 | 472篇 |
2001年 | 357篇 |
2000年 | 282篇 |
1999年 | 230篇 |
1998年 | 184篇 |
1997年 | 136篇 |
1996年 | 138篇 |
1995年 | 115篇 |
1994年 | 68篇 |
1993年 | 57篇 |
1992年 | 45篇 |
1991年 | 35篇 |
1990年 | 29篇 |
1989年 | 16篇 |
1988年 | 23篇 |
1987年 | 15篇 |
1986年 | 13篇 |
1985年 | 28篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1971年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Boris Andreianov Franck Boyer Florence Hubert 《Numerical Methods for Partial Differential Equations》2007,23(1):145-195
Discrete duality finite volume schemes on general meshes, introduced by Hermeline and Domelevo and Omnès for the Laplace equation, are proposed for nonlinear diffusion problems in 2D with nonhomogeneous Dirichlet boundary condition. This approach allows the discretization of non linear fluxes in such a way that the discrete operator inherits the key properties of the continuous one. Furthermore, it is well adapted to very general meshes including the case of nonconformal locally refined meshes. We show that the approximate solution exists and is unique, which is not obvious since the scheme is nonlinear. We prove that, for general W?1,p′(Ω) source term and W1‐(1/p),p(?Ω) boundary data, the approximate solution and its discrete gradient converge strongly towards the exact solution and its gradient, respectively, in appropriate Lebesgue spaces. Finally, error estimates are given in the case where the solution is assumed to be in W2,p(Ω). Numerical examples are given, including those on locally refined meshes. © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 相似文献
12.
Signature analyzers are very efficient output response compactors for BIST design. The only limitation of signature analysis is the fault coverage reduction (aliasing) due to the information loss inherent to any data compaction. In this article, in order to increase the effectiveness of ROM BIST, we take advantage from the simplicity of the error patterns generated by ROMs and we show that aliasing free signature analysis can be achieved in ROM BIST.This work was performed when the author was on leave from Minsk Radio Engineering Institute, Computer Department, Belorus. 相似文献
13.
YAG脉冲激光器快速连通保护系统 总被引:1,自引:1,他引:0
本文阐述了YAG脉冲激光器的一种快速连通保护系统,利用大功率二极管作为连通故障信号检出的关键元件,采用了可控硅与继电器双重保护,使得整个保护系统既快速可靠,又简便适用。 相似文献
14.
Inexact Newton methods for the nonlinear complementarity problem 总被引:2,自引:0,他引:2
Jong-Shi Pang 《Mathematical Programming》1986,36(1):54-71
An exact Newton method for solving a nonlinear complementarity problem consists of solving a sequence of linear complementarity
subproblems. For problems of large size, solving the subproblems exactly can be very expensive. In this paper we study inexact
Newton methods for solving the nonlinear, complementarity problem. In such an inexact method, the subproblems are solved only
up to a certain degree of accuracy. The necessary accuracies that are needed to preserve the nice features of the exact Newton
method are established and analyzed. We also discuss some extensions as well as an application.
This research was based on work supported by the National Science Foundation under grant ECS-8407240. 相似文献
15.
The paper deals with a singularly perturbed reaction diffusionmodel problem. The focus is on reliable a posteriori error estimatorsfor the H1 seminorm that can be applied to anisotropic finiteelement meshes. A residual error estimator and a local problemerror estimator are proposed and rigorously analysed. They arelocally equivalent, and both bound the error reliably. Threemodifications of these estimators are introduced and discussed. Much attention is given to the performance of the error estimatorin numerical experiments. This helps to identify those estimatorsthat are suitable for practical applications. 相似文献
16.
M. Nicolaidis 《Journal of Electronic Testing》1991,1(4):257-273
It has been noted by several authors that the classical stuck-at logical fault model might not be an appropriate representation of certain real failures occurring in integrated circuits. Shorts are an important class of such faults. This article gives a detailed analysis of the effects of shorts in self-checking circuits and proposes techniques for dealing with them. More precisely, we show that, unlike other faults such as stuck-at, stuck-on, and stuck-open—which produce only single errors in the place they occur—shorts can produce double errors on the two shorted lines. In particular, feedback shorts can produce double errors on the two shorted lines. The double error is unidirectional for some feedback shorts and non-unidirectional for some others. Furthermore, in some technologies (e.g., CMOS), non-feedback shorts can also produce double non-unidirectional errors. We also show that unlike stuck-at, stuck-on, and stuck-open faults, redundant shorts can destroy the SFS property. Then we propose several techniques for coping with these problems and we illustrate the results by circuit implementation examples.The present study is given for NMOS and CMOS circuits but we show that it is valid for any other technology. 相似文献
17.
18.
19.
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
20.
Irfan Ahmad Rather Gulshan Kumar Rahul Saha 《International Journal of Communication Systems》2023,36(9):e5473
In heterogeneous access network, Multiple-Input Multiple-Output (MIMO) radio-over-fiber (RoF) system is an efficient approach for multiple signal transmission with low cost and complexity. The performance of RoF fronthaul system in MIMO system will be varied with different nonlinear effects. By adjusting various transmission parameters, such as the input signal power or the laser bias current, the nonlinear impacts produced by the RoF system can be reduced. In this paper, a novel algorithm Improved Aquila Optimization (IAO) is proposed to optimize transmission circumstances of MIMO RoF system. It determines the appropriate bias current for both lasers and Radio Frequency (RF) signal power in a short period. The input signals are wavelength multiplexed with Intensity Modulation and Direct Detection (IM/DD) applied. The carrier as well as transmission frequency is governed by the MIMO-Long-Term Evolution (LTE) standard. The proposed system is implemented in MATLAB, and the performance is evaluated. The experimental results show that fast convergence and trade-off between noise and nonlinearity are obtained with varying bandwidth. In the experimental scenario, the maximum Error Vector Magnitude (EVM) of 1.88, 3.14, and signal-to-noise ratio (SNR) of 3.204, and 2.698 was attained for both quadrature phase shift keying (QPSK) and quadrature amplitude modulation (QAM) modulation. [Correction added on 24 April 2023, after first online publication: the SNR values were corrected in the preceding sentence.] For 100 iterations, the processing time was reduced to 0.137 s. When compared with the conventional state-of-the-art approaches, the accuracy and computational complexity of the proposed approach are improved. 相似文献