全文获取类型
收费全文 | 39382篇 |
免费 | 3210篇 |
国内免费 | 3347篇 |
专业分类
电工技术 | 3927篇 |
技术理论 | 5篇 |
综合类 | 2578篇 |
化学工业 | 2482篇 |
金属工艺 | 316篇 |
机械仪表 | 1474篇 |
建筑科学 | 1335篇 |
矿业工程 | 240篇 |
能源动力 | 1371篇 |
轻工业 | 469篇 |
水利工程 | 273篇 |
石油天然气 | 234篇 |
武器工业 | 183篇 |
无线电 | 2978篇 |
一般工业技术 | 2984篇 |
冶金工业 | 961篇 |
原子能技术 | 152篇 |
自动化技术 | 23977篇 |
出版年
2024年 | 166篇 |
2023年 | 630篇 |
2022年 | 486篇 |
2021年 | 780篇 |
2020年 | 1075篇 |
2019年 | 1143篇 |
2018年 | 1073篇 |
2017年 | 1436篇 |
2016年 | 1537篇 |
2015年 | 1387篇 |
2014年 | 2332篇 |
2013年 | 3534篇 |
2012年 | 1908篇 |
2011年 | 2426篇 |
2010年 | 1747篇 |
2009年 | 2263篇 |
2008年 | 2255篇 |
2007年 | 2271篇 |
2006年 | 1972篇 |
2005年 | 1792篇 |
2004年 | 1470篇 |
2003年 | 1402篇 |
2002年 | 1282篇 |
2001年 | 1033篇 |
2000年 | 1008篇 |
1999年 | 916篇 |
1998年 | 809篇 |
1997年 | 729篇 |
1996年 | 656篇 |
1995年 | 564篇 |
1994年 | 507篇 |
1993年 | 487篇 |
1992年 | 370篇 |
1991年 | 355篇 |
1990年 | 279篇 |
1989年 | 216篇 |
1988年 | 189篇 |
1987年 | 167篇 |
1986年 | 137篇 |
1985年 | 181篇 |
1984年 | 187篇 |
1983年 | 167篇 |
1982年 | 147篇 |
1981年 | 96篇 |
1980年 | 71篇 |
1979年 | 86篇 |
1978年 | 61篇 |
1977年 | 67篇 |
1976年 | 19篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
51.
Jiři Gregor 《Mathematics of Control, Signals, and Systems (MCSS)》1991,4(2):205-215
A significant part of the theory of one-dimensional linear shift-invariant systems is based on the concept of weighting function
(or impulse response): the output is the convolution of the weighting function with the input. This paper introduces the concept
of linear translation-invariant systems and uses this notion in studying impulse response, z-transforms, and transfer functions
for multidimensional systems. 相似文献
52.
Parity space approach and H2 approach are two important fault detection approaches. This paper studies the relationship between these two approaches, which reveals frequency domain characteristics of the optimal solution of the parity space approach on the one side and provides a numerical solution of the H2-optimal design of residual generators on the other side. 相似文献
53.
Udayan Nandkeolyar David P. Christy 《International Journal of Flexible Manufacturing Systems》1992,4(3-4):267-292
Evaluating the design of flexible manufacturing systems is complex. Developing a measure of performance useful for evaluating alternate designs continues to be interesting. Here, total productivity of the system is proposed as an appropriate measure. Specification of parameters based upon strategic considerations for this measure are discussed. Finally, the usefulness of the measure is demonstrated through an example. 相似文献
54.
N. S. Nikitchenko 《Cybernetics and Systems Analysis》2003,39(1):97-112
Predicates that preserve their values on a larger (extended) body of data are called equitone. An algebra of such predicates is constructed, a system of its generators is specified, and a complete system of transformations of identities is defined. The results obtained are used for construction and investigation of complete classes of compositions of various types and levels of abstractions that are used in logics of partial predicates. 相似文献
55.
This paper reports the findings of a detailed study of Web-based systems design (WBSD) practices in Ireland based on data
collected over a 3-year period (2002–2005), the objectives of which were to (1) contribute towards a richer understanding
of the current “real-world” context of WBSD by characterising the profile of a typical project (team size, timeframe, nature
of requirements, etc.) and identifying the key challenges, constraints, and imperatives (i.e. “mediating factors”) faced by
Web-based system designers, and (2) understand how those contextual parameters and mediating factors influence the activity
of WBSD as regards the selection and enactment of whatever design practices are therefore engaged (i.e. the use of methods,
procedures, etc.). Data was gathered through a survey which yielded 165 usable responses, and later through a series of semi-structured
qualitative interviews. Using grounded theory, an explanatory conceptual framework is derived, based on an extension of the
“method-in-action” model, the application of which to WBSD has not been previously investigated in depth. It is proposed that
this framework of WBSD issues is valuable in a number of ways to educators, researchers, practitioners, and method engineers. 相似文献
56.
Backlash is one of the most important non-linearities that limit the performance of speed and position control in industrial, robotics, automotive, automation and other applications. The control of systems with backlash has been the subject of study since the 1940s. This survey reveals that surprisingly few control innovations have been presented since the early path breaking papers that introduced the describing function analysis of systems with backlash. Promising developments are however taking place using adaptive and non-linear control strategies. 相似文献
57.
H.A. Barker Author Vitae A.H. Tan Author Vitae K.R. Godfrey Author Vitae 《Automatica》2003,39(1):127-133
Analysis of systems with direction-dependent dynamics is currently limited to cases in which the dynamics in the two directions of the output are first order; results for such systems have been published for both pseudo-random maximum-length binary (MLB) and inverse-repeat maximum-length binary (IR-MLB) inputs. These relatively limited analytical results make it useful to examine alternative ways of modelling such systems and in this paper, Wiener models are considered for this purpose. Methods for optimising the Wiener model parameters by matching the system and model cross-correlation functions, outputs, and discrete Fourier transforms of the outputs are considered, and the results are compared. These methods are also applied to a first-order direction-dependent system with a maximum-length ternary (MLT) input, for which no analytical results are currently available, and to a second-order system with an IR-MLB input. 相似文献
58.
The State of the Art in Text Filtering 总被引:1,自引:0,他引:1
This paper develops a conceptual framework for text filtering practice and research, and reviews present practice in the field.
Text filtering is an information seeking process in which documents are selected from a dynamic text stream to satisfy a relatively
stable and specific information need. A model of the information seeking process is introduced and specialized to define text
filtering. The historical development of text filtering is then reviewed and case studies of recent work are used to highlight
important design characteristics of modern text filtering systems. User modeling techniques drawn from information retrieval,
recommender systems, machine learning and other fields are described. The paper concludes with observations on the present
state of the art and implications for future research on text filtering.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
59.
Recently, efficient scheduling algorithms based on Lagrangian relaxation have been proposed for scheduling parallel machine
systems and job shops. In this article, we develop real-world extensions to these scheduling methods. In the first part of
the paper, we consider the problem of scheduling single operation jobs on parallel identical machines and extend the methodology
to handle multiple classes of jobs, taking into account setup times and setup costs. The proposed methodology uses Lagrangian
relaxation and simulated annealing in a hybrid framework. In the second part of the paper, we consider a Lagrangian relaxation
based method for scheduling job shops and extend it to obtain a scheduling methodology for a real-world flexible manufacturing
system with centralized material handling.
This research was supported in part by the Office of Naval Research and the Department of Science and Technology grant N00014-93-1017. 相似文献
60.
生物超微弱发光的光子计数成象方法 总被引:1,自引:0,他引:1
介绍了我们研制和设计的用于测量生物超微弱发光的光子计数成象系统,包括光子成象头,高帧频CCD摄象机,图象采集系统和计算机,可以定量地探测出生物的发光强度分布 ,还能够显示出其发光的图象,确定发光的形状和位置,本系统的信噪比为10:1,最小探测功率达10^-16W,灵敏度高,动态范围大。 相似文献