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21.
I. EpifanioAuthor Vitae J. GutiérrezAuthor VitaeJ. MaloAuthor Vitae 《Pattern recognition》2003,36(8):1799-1811
Two types of redundancies are contained in images: statistical redundancy and psychovisual redundancy. Image representation techniques for image coding should remove both redundancies in order to obtain good results. In order to establish an appropriate representation, the standard approach to transform coding only considers the statistical redundancy, whereas the psychovisual factors are introduced after the selection of the representation as a simple scalar weighting in the transform domain.In this work, we take into account the psychovisual factors in the definition of the representation together with the statistical factors, by means of the perceptual metric and the covariance matrix, respectively. In general the ellipsoids described by these matrices are not aligned. Therefore, the optimal basis for image representation should simultaneously diagonalize both matrices. This approach to the basis selection problem has several advantages in the particular application of image coding. As the transform domain is Euclidean (by definition), the quantizer design is highly simplified and at the same time, the use of scalar quantizers is truly justified. The proposed representation is compared to covariance-based representations such as the DCT and the KLT or PCA using standard JPEG-like and Max-Lloyd quantizers. 相似文献
22.
Web站点的故障转移群集的应用 总被引:4,自引:0,他引:4
分析了故障转移群集的基本原理,运用“故障转移群集化”来规划网络,保证了Web站点的安全性和数据的可靠性,通过提供应用程序服务器中的冗余设计,来避免应用程序故障(可用性中断),并确保联机商业活动的安全性与可靠性。 相似文献
23.
一种基于C/S模式的分布式数据库服务器系统模型 总被引:6,自引:1,他引:6
田俊峰 《计算机工程与应用》2003,39(23):176-179
该文介绍了一种分布式数据库服务器的构成原理及工作模型,讨论了它的冗余关系、中间件结构、并发控制策略、实现机理及其性能分析等。 相似文献
24.
This paper combines universal moment generating function technique with stochastic Petri nets to solve the redundancy optimization problem for multi-state systems under repair policies. Redundant elements are included in order to achieve a desirable level of production availability. The elements of the system are characterized by their cost, performance and availability. These elements are chosen from a list of products available on the market. The number of repair teams is less than the number of reparable elements, and a repair policy specifies the maintenance priorities between the system elements. A heuristic is proposed to determine the minimal cost system configuration under availability constraints. This heuristic, first applies universal moment generating function technique to evaluate the system availability, assuming unlimited maintenance resources. Once a preliminary solution is found by the optimization algorithm, stochastic Petri nets are used to model different repair policies, and to find the best system configuration (architecture and number of repairmen) in terms of global performance (availability and cost). This combined procedure is applied to a reference example. 相似文献
25.
Common-cause failures (CCF) are one of the more critical and challenging issues for system reliability and risk analyses. Academic interest in modeling CCF, and more broadly in modeling dependent failures, has steadily grown over the years in the number of publications as well as in the sophistication of the analytical tools used. In the past few years, several influential articles have shed doubts on the relevance of redundancy arguing that “redundancy backfires” through common-cause failures, and that the latter dominate unreliability, thus defeating the purpose of redundancy. In this work, we take issue with some of the results of these publications. In their stead, we provide a nuanced perspective on the (contingent) value of redundancy subject to common-cause failures. First, we review the incremental reliability and MTTF provided by redundancy subject to common-cause failures. Second, we introduce the concept and develop the analytics of the “redundancy–relevance boundary”: we propose this redundancy–relevance boundary as a design-aid tool that provides an answer to the following question: what level of redundancy is relevant or advantageous given a varying prevalence of common-cause failures? We investigate the conditions under which different levels of redundancy provide an incremental MTTF over that of the single component in the face of common-cause failures. Recognizing that redundancy comes at a cost, we also conduct a cost–benefit analysis of redundancy subject to common-cause failures, and demonstrate how this analysis modifies the redundancy–relevance boundary. We show how the value of redundancy is contingent on the prevalence of common-cause failures, the redundancy level considered, and the monadic cost–benefit ratio. Finally we argue that general unqualified criticism of redundancy is misguided, and efforts are better spent for example on understanding and mitigating the potential sources of common-cause failures rather than deriding the concept of redundancy in system design. 相似文献
26.
从稀疏信号重建角度提出了一种改进的波达方向(DOA)估计方法。由于最小冗余线阵(MRLA)能以较少的阵元数获得较大的阵列孔径,将MRLA与l1-SVD方法相结合估计信号的DOA。仿真结果表明,经多次实验验证,所提方法是有效的,相比l1-SVD方法可以估计出更多信源的DOA,并且可以用较少的阵元数估计更多的信源DOA,具有信源过载能力。 相似文献
27.
以ARM9微处理器与VxWorks操作系统为基础设计实现冗余PROFIBUS-DP主站控制器.详细讨论了冗余DP主站控制器对从站的管理维护以及冗余通信与主备切换的实现方法,并提供了与上位机通信的以太网接口,通过该接口可以对冗余DP主站组态并监控运行状态.本设计对国内冗余DP主站方面的研究提供了一种参考. 相似文献
28.
29.
TMR计算机系统FT-HIT的冗余管理技术 总被引:4,自引:0,他引:4
FT-HIT是自行研制的3模冗余(TMR)航天容错计算机系统,系统通过硬件冗余和主要由软件实现容错的冗余管理模式实现系统的容错性能。其冗余管理主要包括:故障检测、故障屏蔽、故障隔离、系统重构与故障恢复等功能 相似文献
30.