全文获取类型
收费全文 | 225140篇 |
免费 | 18717篇 |
国内免费 | 13481篇 |
专业分类
电工技术 | 35053篇 |
技术理论 | 22篇 |
综合类 | 25547篇 |
化学工业 | 11110篇 |
金属工艺 | 7749篇 |
机械仪表 | 18783篇 |
建筑科学 | 18788篇 |
矿业工程 | 9004篇 |
能源动力 | 8323篇 |
轻工业 | 4989篇 |
水利工程 | 6530篇 |
石油天然气 | 6748篇 |
武器工业 | 3863篇 |
无线电 | 22979篇 |
一般工业技术 | 12521篇 |
冶金工业 | 7040篇 |
原子能技术 | 2308篇 |
自动化技术 | 55981篇 |
出版年
2024年 | 788篇 |
2023年 | 2136篇 |
2022年 | 4178篇 |
2021年 | 5308篇 |
2020年 | 5709篇 |
2019年 | 4265篇 |
2018年 | 3813篇 |
2017年 | 5376篇 |
2016年 | 6378篇 |
2015年 | 7401篇 |
2014年 | 14085篇 |
2013年 | 12040篇 |
2012年 | 16615篇 |
2011年 | 17582篇 |
2010年 | 13316篇 |
2009年 | 13371篇 |
2008年 | 13741篇 |
2007年 | 17551篇 |
2006年 | 15728篇 |
2005年 | 14079篇 |
2004年 | 11513篇 |
2003年 | 10398篇 |
2002年 | 7908篇 |
2001年 | 6646篇 |
2000年 | 5492篇 |
1999年 | 4446篇 |
1998年 | 3339篇 |
1997年 | 2716篇 |
1996年 | 2396篇 |
1995年 | 2039篇 |
1994年 | 1686篇 |
1993年 | 1145篇 |
1992年 | 969篇 |
1991年 | 691篇 |
1990年 | 569篇 |
1989年 | 470篇 |
1988年 | 335篇 |
1987年 | 189篇 |
1986年 | 116篇 |
1985年 | 134篇 |
1984年 | 110篇 |
1983年 | 101篇 |
1982年 | 76篇 |
1981年 | 68篇 |
1980年 | 58篇 |
1979年 | 49篇 |
1978年 | 37篇 |
1977年 | 33篇 |
1976年 | 24篇 |
1959年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Javier Ramírez Antonio García Uwe Meyer-Bäse Fred Taylor Antonio Lloris 《The Journal of VLSI Signal Processing》2003,33(1-2):171-190
Currently there are design barriers inhibiting the implementation of high-precision digital signal processing (DSP) objects with field programmable logic (FPL) devices. This paper explores overcoming these barriers by fusing together the popular distributed arithmetic (DA) method with the residue number system (RNS) for use in FPL-centric designs. The new design paradigm is studied in the context of a high-performance filter bank and a discrete wavelet transform (DWT). The proposed design paradigm is facilitated by a new RNS accumulator structure based on a carry save adder (CSA). The reported methodology also introduces a polyphase filter structure that results in a reduced look-up table (LUT) budget. The 2C-DA and RNS-DA are compared, in the context of a FPL implementation strategy, using a discrete wavelet transform (DWT) filter bank as a common design theme. The results show that the RNS-DA, compared to a traditional 2C-DA design, enjoys a performance advantage that increases with precision (wordlength). 相似文献
2.
Takeshi Nakajo 《Quality and Reliability Engineering International》1993,9(2):111-119
Work system improvements are implemented in various manufacturing processes to prevent problems caused by human errors. However, they are almost always applied to problems which have already occurred. This paper examines a method of identifying latent human errors existing within the work systems beforehand. A procedure for applying failure mode and effect analysis to this identification problem was defined based on over 1000 empirical errors: a work system decomposition criterion and fundamental error modes for listing latent human errors, and then applied to three practical manufacturing processes in order to evaluate its effectiveness. 相似文献
3.
Xuejun Xie Siying Zhang 《International Journal of Adaptive Control and Signal Processing》2002,16(1):39-59
This paper considers the adaptive pole‐placement control problem for system (1) with unmodelled dynamics ηn dominated by a small constant ε multiplied by a quantity independent of ε but tending to infinity as the past input, output, and noise grow. Using bounded external excitation and randomly varying truncation techniques, we give a design method of adaptive pole‐placement controller. It is shown that the closed‐loop system is globally stable, the estimation error for the parameter contained in the modelled part is of order ε, and the closed‐loop system under the adaptive pole‐placement control law is suboptimal in the sense of $$\mathop{\lim\sup}\limits_{{n\to\infty }}{1\over n}\mathop{\sum}\limits_{i=0}^n{\left({A^{*}(z)y_{n}‐L(z)C(z)w_{n}‐B(z)R(z)y_{n}^{*}}\right)^{2}{\leq}O({\varepsilon}^{2})+\gamma^{2}\mathop{\sum}\limits_{j=1}^q{b_{j}^{2}}}$$\nopagenumbers\end while the SPR condition used usually in other papers is replaced by a stability condition. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
4.
宝钢研制的全氢罩式炉控制系统分析 总被引:4,自引:0,他引:4
对宝钢研制的全氢罩式炉计算机控制系统的逻辑结构、工作原理及硬件配置进行了分析.该系统与引进的系统相比,在通讯方式、程序结构、操作分析、报警和开放性等方面都有所改进. 相似文献
5.
介绍I/A’S系统在巨化热电厂八号50MW供热机组上应用实例,并从DCS系统的整体设计到实现的功能、控制效果等多方面进行了分折,总结了调试和运行经验。 相似文献
6.
The requirements on an object-oriented DBMS for management of information in a large, complex enterprise are presented. These requirements aid in the achievement of an environment characterized by data sharing, open architectures, application and data portability, and assurance of data integrity. They were defined from the point of view of a user of the DBMS; therefore they describe the expected functionality of the DBMS and do not specify the method of implementation to achieve this functionality. They encompass requirements on the data model, query and data manipulation languages, the system architecure, interfaces to the system, change management, and transaction management. 相似文献
7.
Chris Harty 《Building Research & Information》2005,33(6):512-522
An alternative approach to understanding innovation is made using two intersecting ideas. The first is that successful innovation requires consideration of the social and organizational contexts in which it is located. The complex context of construction work is characterized by inter-organizational collaboration, a project-based approach and power distributed amongst collaborating organizations. The second is that innovations can be divided into two modes: 'bounded', where the implications of innovation are restricted within a single, coherent sphere of influence, and 'unbounded', where the effects of implementation spill over beyond this. Bounded innovations are adequately explained within the construction literature. However, less discussed are unbounded innovations, where many firms' collaboration is required for successful implementation, even though many innovations can be considered unbounded within construction's inter-organizational context. It is argued that unbounded innovations require an approach to understand and facilitate the interactions both within a range of actors and between the actors and technological artefacts. The insights from a sociology of technology approach can be applied to the multiplicity of negotiations and alignments that constitute the implementation of unbounded innovation. The utility of concepts from the sociology of technology, including 'system building' and 'heterogeneous engineering', is demonstrated by applying them to an empirical study of an unbounded innovation on a major construction project (the new terminal at Heathrow Airport, London, UK). This study suggests that 'system building' contains outcomes that are not only transformations of practices, processes and systems, but also the potential transformation of technologies themselves. 相似文献
8.
9.
ETRⅠ-30调速器是瑞士爱舍维斯工厂生产的具有PID调节规律的电液调速器。本文对其液压控制系统作了较详细的介绍,供有关人员参考。 相似文献
10.
New technologies such as power electronics have made it possible to change continuously the impedance of a power system not only to control power flow but also to enhance stability. A power system incorporating a variable impedance apparatus such as a variable series capacitor (VSrC) and high-speed phase shifter (HSPS) is called VIPS (Variable Impedance Power System) by the authors. This paper proposes a novel control method of VIPS apparatus such as VSrC and HSPS installed at an interconnecting point for stabilizing inter-area unstable and/or oscillatory modes. The proposed design method of the control system is a kind of hierarchical decentralized control method of a large-scale power system based on a Lyapunov function. Under the proposed control scheme, each subsystem can be stabilized independently by local controllers such as AVR, speed governor and PSS, and then the whole interconnected system can be stabilized by VIPS apparatus taking into account interactions between subsystems. The effectiveness and robustness of the VIPS apparatus control are shown by numerical examples with model systems including a large-scale power system. 相似文献