全文获取类型
收费全文 | 53033篇 |
免费 | 5456篇 |
国内免费 | 2864篇 |
专业分类
电工技术 | 3722篇 |
技术理论 | 6篇 |
综合类 | 4041篇 |
化学工业 | 8767篇 |
金属工艺 | 2841篇 |
机械仪表 | 3410篇 |
建筑科学 | 4533篇 |
矿业工程 | 1585篇 |
能源动力 | 1761篇 |
轻工业 | 3921篇 |
水利工程 | 1110篇 |
石油天然气 | 2591篇 |
武器工业 | 557篇 |
无线电 | 6233篇 |
一般工业技术 | 6138篇 |
冶金工业 | 2164篇 |
原子能技术 | 628篇 |
自动化技术 | 7345篇 |
出版年
2024年 | 234篇 |
2023年 | 981篇 |
2022年 | 1859篇 |
2021年 | 2573篇 |
2020年 | 1858篇 |
2019年 | 1563篇 |
2018年 | 1703篇 |
2017年 | 1847篇 |
2016年 | 1640篇 |
2015年 | 2308篇 |
2014年 | 2812篇 |
2013年 | 3319篇 |
2012年 | 3726篇 |
2011年 | 3787篇 |
2010年 | 3627篇 |
2009年 | 3426篇 |
2008年 | 3302篇 |
2007年 | 2883篇 |
2006年 | 2881篇 |
2005年 | 2270篇 |
2004年 | 1635篇 |
2003年 | 1363篇 |
2002年 | 1471篇 |
2001年 | 1281篇 |
2000年 | 1137篇 |
1999年 | 1175篇 |
1998年 | 864篇 |
1997年 | 737篇 |
1996年 | 686篇 |
1995年 | 524篇 |
1994年 | 469篇 |
1993年 | 320篇 |
1992年 | 280篇 |
1991年 | 201篇 |
1990年 | 149篇 |
1989年 | 134篇 |
1988年 | 87篇 |
1987年 | 56篇 |
1986年 | 43篇 |
1985年 | 30篇 |
1984年 | 22篇 |
1983年 | 16篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1974年 | 2篇 |
1970年 | 2篇 |
1959年 | 3篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
101.
A model for preventive maintenance operations and forecasting 总被引:2,自引:1,他引:1
Equipment costs constitute the greatest majority of overall costs for semiconductor manufacturing. Therefore, maintaining
high equipment availability has been regarded as one of the major goals in the industry. The ability to forecast correctly
equipment preventive maintenance (PM) timing requirements not only can help optimizing equipment uptime but also minimizing
negative impacts on manufacturing production efficiency. This research used grey theory and evaluation diagnosis to construct
a PM forecasting model for prediction of PM timing of various machines. The results showed significant improvements of PM
timing predictions compared to the existing method based on experience and an alternative method proposed by Li and Chang
(Semiconductor Manufacturing Technology Workshop 2002: 10–11, pp. 275–277) for the same fab cases.
Received: June 2005 / Accepted: December 2005 相似文献
102.
The goal of face recognition is to distinguish persons via their facial images. Each person's images form a cluster, and a new image is recognized by assigning it to the correct cluster. Since the images are very high-dimensional, it is necessary to reduce their dimension. Linear discriminant analysis (LDA) has been shown to be effective at dimension reduction while preserving the cluster structure of the data. It is classically defined as an optimization problem involving covariance matrices that represent the scatter within and between clusters. The requirement that one of these matrices be nonsingular restricts its application to datasets in which the dimension of the data does not exceed the sample size. For face recognition, however, the dimension typically exceeds the number of images in the database, resulting in what is referred to as the small sample size problem. Recently, the applicability of LDA has been extended by using the generalized singular value decomposition (GSVD) to circumvent the nonsingularity requirement, thus making LDA directly applicable to face recognition data. Our experiments confirm that LDA/GSVD solves the small sample size problem very effectively as compared with other current methods. 相似文献
103.
Average consensus in networks of dynamic agents with switching topologies and multiple time-varying delays 总被引:5,自引:0,他引:5
In this paper, we discuss average consensus problem in undirected networks of dynamic agents with fixed and switching topologies as well as multiple time-varying communication delays. By employing a linear matrix inequality method, we prove that all the nodes in the network achieve average consensus asymptotically for appropriate communication delays if the network topology is connected. Particularly, several feasible linear matrix inequalities are established to determine the maximal allowable upper bound of time-varying communication delays. Numerical examples are given to demonstrate the effectiveness and the sharpness of the theoretical results. 相似文献
104.
通过对铰孔孔径增大,误差大产生原因的工艺探讨、分析,提出了有效、切实可行的避免措施,通过灵活应用,提高了产品质量。 相似文献
105.
106.
An innovative method for modelling biological processes under anaerobic conditions is presented and discussed. The method is based on titrimetric and off-gas measurements. Titrimetric data is recorded as the addition rate of hydroxyl ions or protons that is required to maintain pH in a bioreactor at a constant level. An off-gas analysis arrangement measures, among other things, the transfer rate of carbon dioxide. The integration of these signals results in a continuous signal which is solely related to the biological reactions. When coupled with a mathematical model of the biological reactions, the signal allows a detailed characterisation of these reactions, which would otherwise be difficult to achieve. Two applications of the method to the enhanced biological phosphorus removal processes are presented and discussed to demonstrate the principle and effectiveness of the method. 相似文献
107.
A systematic approach for synthesising gyrator-C active transformers using MOS transistors is presented. The topology of gyrator-C active inductors and their characteristics are briefly reviewed first. This is followed by the development of ideal gyrator-C active transformers, where only the capacitor loads of the transconductors synthesising active transformers are considered. The self and mutual inductances of both the primary and secondary windings of active transformers are investigated in detailed. Non-ideal gyrator-C active transformers are developed with the consideration of both the resistance and capacitance loads of transconductors. The intrinsic relation between the self and mutual inductances is derived. The configuration of gyrator-C active transformers with multiple primary and secondary windings is also developed. The proposed active transformers offer large and tunable self and mutual inductances with virtually no silicon area requirement. Several practical implementations of the proposed active transformers have been realised in TSMC-0.18 mum 1.8 V CMOS technology and analysed using SpectreRF with BSIM3v3 device models. Simulation results on voltage transfer characteristics, self and mutual inductances, quality factors, stability, the effect of process variations, and noise are presented. The application of the proposed active transformers is exemplified using a 1.6 GHz active transformer quadrature oscillator. 相似文献
108.
This paper studies a Kansas Department of Transportation welded plate girder bridge that developed fatigue cracks at small web gaps close to the girder top flange. Repair had been previously performed by softening the connection plate end with a slot retrofit, but cracks were recently found to have reinitiated at some of the repaired details and are again propagating. A comprehensive finite-element method study was performed to investigate the cracking behavior observed in the bridge and to recommend appropriate measures for future bridge retrofit. The analytical results show that stresses developed at the top flange web gaps could exceed yielding under the loading of an HS15 fatigue truck. The current slot repair used in the bridge was found to have introduced higher magnitude fatigue stresses in the web gap. To achieve a permanent repair of the bridge, it is recommended that a welded connection plate to flange attachment be used during future bridge retrofit. The web gap details should be able to withstand unlimited number of load cycles once this additional repair is performed. 相似文献
109.
JIANG Zengguo ZHAO Yuan 《武汉理工大学学报(材料科学英文版)》2005,20(3):110-112
1IntroductionLime-flyashstabilizedsoil as a semi-rigid base mate-rial in highwayis widely usedin China.The goodintegri-ty,great bearing capacity,highstiffness and water-proof-ing quality areits special advantages.But itsinherent lowearly strength makes it… 相似文献
110.
Prolog逻辑程序设计语言具有不同于传统程序设计语言的特点.本文根据测试Prolog程序的实践,提出了一系列为Prolog程序生成测试用例的准则.按这些准则测试实际程序效果良好.这是在逻辑程序测试新领域迈出的一步. 相似文献