全文获取类型
收费全文 | 2712篇 |
免费 | 209篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 58篇 |
综合类 | 1篇 |
化学工业 | 841篇 |
金属工艺 | 34篇 |
机械仪表 | 66篇 |
建筑科学 | 72篇 |
矿业工程 | 3篇 |
能源动力 | 98篇 |
轻工业 | 315篇 |
水利工程 | 10篇 |
石油天然气 | 1篇 |
无线电 | 208篇 |
一般工业技术 | 437篇 |
冶金工业 | 41篇 |
原子能技术 | 33篇 |
自动化技术 | 712篇 |
出版年
2024年 | 4篇 |
2023年 | 44篇 |
2022年 | 191篇 |
2021年 | 206篇 |
2020年 | 80篇 |
2019年 | 99篇 |
2018年 | 115篇 |
2017年 | 91篇 |
2016年 | 137篇 |
2015年 | 115篇 |
2014年 | 153篇 |
2013年 | 224篇 |
2012年 | 171篇 |
2011年 | 196篇 |
2010年 | 137篇 |
2009年 | 164篇 |
2008年 | 137篇 |
2007年 | 98篇 |
2006年 | 97篇 |
2005年 | 90篇 |
2004年 | 65篇 |
2003年 | 49篇 |
2002年 | 43篇 |
2001年 | 30篇 |
2000年 | 25篇 |
1999年 | 16篇 |
1998年 | 26篇 |
1997年 | 16篇 |
1996年 | 24篇 |
1995年 | 14篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有2930条查询结果,搜索用时 15 毫秒
81.
82.
83.
Polyamides incorporating furan moieties. 5. Synthesis and characterisation of furan-aromatic homologues 总被引:1,自引:0,他引:1
2,2′-Bis (5-chloroformyl 2-furyl) propane and various aromatic diamines were used as monomers in the study of their interfacial polycondensation and the properties of the ensuing furanic-aromatic polyamides. The effects of such variables as the nature of the organic phase, the temperature, the reaction time, and the type and concentration of the catalyst were investigated as well as the properties of the polyamides in terms of structure, average chain length, Tg, Tm and thermal stability. 相似文献
84.
We consider a multiuser multiple-input multiple-output (MIMO) communication system using code-division multiple access (CDMA) and multiuser detection to discriminate the different users. Our focus is on the CDMA uplink of a frequency-nonselective Rayleigh fading channel. We study two types of receivers: joint receivers, which address simultaneously both spatial and multiple-access interference; and separate receivers, addressing the two types of interference individually. This approach allows assessing the benefits of adding MIMO processing capabilities to existing multiuser single-input single-output systems. For both receiver types, we analyze solutions based on linear (matched filter, decorrelator, minimum mean-square error) and maximum-likelihood receivers. For all the receivers considered, we provide closed-form expressions (as expectations of given functions) of the resulting pairwise error probabilities. Performance results are obtained in terms of frame-error rate versus E/sub b//N/sub 0/, following two different approaches. An analytic approach using large-system asymptotic methods, whereby the system parameters (number of users and antennas, spreading gain) are assumed to grow to infinity with finite limiting ratios. A computer-simulation approach is used to illustrate the differences between asymptotic and simulation results. 相似文献
85.
Capacitive micromachined ultrasonic transducers (CMUTs) bring the fabrication technology of standard integrated circuits into the field of ultrasound medical imaging. This unique property, combined with the inherent advantages of CMUTs in terms of increased bandwidth and suitability for new imaging modalities and high frequency applications, have indicated these devices as new generation arrays for acoustic imaging. The advances in microfabrication have made possible to fabricate, in few years, silicon-based electrostatic transducers competing in performance with the piezoelectric transducers. This paper summarizes the fabrication, design, modeling, and characterization of 1D CMUT linear arrays for medical imaging, established in our laboratories during the past 3 years. Although the viability of our CMUT technology for applications in diagnostic echographic imaging is demonstrated, the whole process from silicon die to final probe is not fully mature yet for successful practical applications. 相似文献
86.
This paper discusses some issues about the usage of SDL and related commercial SDL support tools for the validation of a railway signalling system: in particular, the issue of the multiple configurations presented by this system is addressed, discussing the possible strategies to validate the system regardless to the actual configuration. 相似文献
87.
This paper shows a parallel implementation of a priority queue with bandwidthPand maximum sizenPby means of a network with reconfigurable buses. The proposed solution is based on a tree of meshes architecture ofO(nP2) processors andO(Plogn) maximum subbus length. The computational times required by the operations of a priority queue with bandwidthPareO(1) for all the operations, using the unit-time delay model for broadcasting, while they areO(1) for MIN andO(logP+ log logn) for both DELETEMIN and INSERT, using the log-time delay model. The proposed network can be laid out in a classical H-shaped manner to occupyO(nP2) area in the VLSI model. WhenP=O(1), the required area is optimal and, using the unit-time delay model, the resultingAT2is also optimal. The paper presents also a very simple and efficient way of merging two sorted sequences on a reconfigurable mesh, which is used in the implementation of the priority queue operations. 相似文献
88.
两种补偿动态摩擦力的先进控制策略 总被引:12,自引:0,他引:12
在小型DC伺服电机中,静摩擦力和库仑摩擦力的影响是相当明显的.本文提出
了改善系统响应特性的两种控制策略.第一种基于摩擦力模型的在线补偿.适用于变化信
号的跟踪.第二种基于自学习原理的重复控制,适用于周期信号的跟踪.两种控制策略均已
实施在计算机控制的伺服系统中.给出了与常规控制结果的对比. 相似文献
89.
Software engineers of multi‐agent systems (MASs) are faced with different concerns such as autonomy, adaptation, interaction, collaboration, learning, and mobility, which are essentially different from classical concerns addressed in object‐oriented software engineering. MAS developers, however, have relied mostly on object‐oriented design techniques and programming languages, such as Java. This often leads to a poor separation of MAS concerns and in turn to the production of MASs that are difficult to maintain and reuse. This paper discusses software engineering approaches for MASs, and presents a new method for integrating agents into object‐oriented software engineering from an early stage of design. The proposed approach encourages the separate handling of MAS concerns, and provides a disciplined scheme for their composition. Our proposal explores the benefits of aspect‐oriented software development for the incorporation of agents into object‐oriented systems. We also illustrate our aspect‐oriented approach through the Portalware multi‐agent system, a Web‐based environment for the development of e‐commerce portals. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
90.
Alessandro Chiuso Author Vitae Author Vitae 《Automatica》2004,40(4):575-589
There is experimental evidence that the performance of standard subspace algorithms from the literature (e.g. the N4SID method) may be surprisingly poor in certain experimental conditions. This happens typically when the past signals (past inputs and outputs) and future input spaces are nearly parallel. In this paper we argue that the poor behavior may be attributed to a form of ill-conditioning of the underlying multiple regression problem, which may occur for nearly parallel regressors. An elementary error analysis of the subspace identification problem, shows that there are two main possible causes of ill-conditioning. The first has to do with near collinearity of the state and future input subspaces. The second has to do with the dynamical structure of the input signal and may roughly be attributed to “lack of excitation”. Stochastic realization theory constitutes a natural setting for analyzing subspace identification methods. In this setting, we undertake a comparative study of three widely used subspace methods (N4SID, Robust N4SID and PO-MOESP). The last two methods are proven to be essentially equivalent and the relative accuracy, regarding the estimation of the (A,C) parameters, is shown to be the same. 相似文献