首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   190篇
  免费   5篇
  国内免费   2篇
电工技术   6篇
化学工业   28篇
金属工艺   2篇
机械仪表   11篇
建筑科学   4篇
能源动力   20篇
轻工业   29篇
石油天然气   1篇
无线电   31篇
一般工业技术   12篇
冶金工业   9篇
自动化技术   44篇
  2023年   4篇
  2022年   2篇
  2021年   7篇
  2020年   12篇
  2019年   10篇
  2018年   12篇
  2017年   14篇
  2016年   8篇
  2015年   2篇
  2014年   11篇
  2013年   26篇
  2012年   7篇
  2011年   14篇
  2010年   14篇
  2009年   9篇
  2008年   8篇
  2007年   5篇
  2006年   3篇
  2005年   4篇
  2004年   2篇
  2003年   3篇
  2002年   1篇
  2000年   3篇
  1999年   2篇
  1998年   2篇
  1997年   2篇
  1996年   2篇
  1995年   1篇
  1994年   1篇
  1988年   1篇
  1987年   2篇
  1985年   1篇
  1982年   2篇
排序方式: 共有197条查询结果,搜索用时 15 毫秒
11.
Pose retrieval of a rigid object from monocular video sequences or images is addressed. Initially, the object pose is estimated in each image assuming flat depth maps. Shape-from-silhouette is then applied to make a 3-D model (volume), which is used for a new round of pose estimations, this time by a model-based method that gives better estimates. Before repeating this process by building a new volume, pose estimates are adjusted to reduce error by maximizing a novel quality factor for shape-from-silhouette volume reconstruction. The feedback loop is terminated when pose estimates do not change much, as compared with those produced by the previous iteration. Based on a theoretical study of the proposed system, a test of convergence to a given set of poses is devised. Reliable performance of the system is also proved by several experiments on both synthetic and real image sequences. No model is assumed for the object and no feature point is detected or tracked as there is no problematic feature matching or correspondence. Our method can be used for 3-D object tracking in video, 3-D modeling, and volume reconstruction from video.  相似文献   
12.
The control of a permanent-magnet synchronous motor is a nontrivial issue in AC drives, because of its nonlinear dynamics and time-varying parameters. Within this paper, a new passivity-based controller designed to force the motor to track time-varying speed and torque trajectories is presented. Its design avoids the use of the Euler–Lagrange model and destructuring since it uses a flux-based dq modelling, independent of the rotor angular position. This dq model is obtained through the three-phase abc model of the motor, using a Park transform. The proposed control law does not compensate the model’s workless force terms which appear in the machine’s dq model, as they have no effect on the system’s energy balance and they do not influence the system’s stability properties. Another feature is that the cancellation of the plant’s primary dynamics and nonlinearities is not done by exact zeroing, but by imposing a desired damped transient. The effectiveness of the proposed control is illustrated by numerical simulation results.  相似文献   
13.
Best maintenance practices in communications networks management are benchmarking standards that, if carefully implemented, will enhance the integrity, reliability and maintenance costs of communications networks. This paper defines best maintenance practices in communications network management within a concise framework encompassing measurable performance‐level goals as well as methods and procedures needed to achieve these goals. The best maintenance practice recommendations of this paper cover many segments of communications networks and services, including wireline and wireless networks as well as multiple network spaces and technologies. The paper also outlines certain recent trends in network maintenance and provides specific recommendations for action to be taken to ensure that best network maintenance practices are implemented and maintained. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
14.
In this paper a dual operating mode 8-bit, 1.1-V pipeline ADC for Gigabit Ethernet applications is presented. In the two operating modes, the ADC features different sampling frequency (125 and 250 MHz) and power consumption (9.4 and 22.8 mW). Considering a signal bandwidth of 60 MHz in both operating modes, as required by the Gigabit Ethernet standard, the ADC achieves a SNDR always larger than 39.4 dB at 125 MHz and 38.7 dB at 250 MHz (6.25-bit and 6.13-bit ENOB, respectively), with a FoM of 0.84 pJ/conv at 125 MHz and 2.2 pJ/conv at 250 MHz. The ENOB achieved is mainly limited by clock jitter. The ADC is fabricated with a 90-nm CMOS technology, with an active area of 1.25 × 0.65 mm2.  相似文献   
15.
Vertical handoff is one of the most important issues for the next generation heterogeneous wireless networks. However, in many situations, unbeneficial vertical handoffs occur across intersystem heterogeneous networks cause network performance degradation. Therefore, we propose a novel configuration architecture that can be deployed in the next generation of wireless networks. Second, we propose a predictive and adaptive Vertical Handoff Decision Scheme that optimizes the handoff initiation time as well as selection of the most optimal network. The proposed vertical handoff decision algorithm considers the technology type as well as the Signal to Interference Ratio (SIR), the Mobile Station (MS) velocity, the user preferences, the applications requirements and the terminal capabilities as the most important factors to make vertical handoff decision. In order to minimize handoff costs, the proposed decision algorithm uses the dwell timer concept. The handoff costs are analyzed in terms of unnecessary and unbeneficial handoffs rate.The simulation results show that the reduction of unnecessary handoffs proposed in our vertical handoff decision scheme reduces the handoff blocking probability, the packets loss rate and the handoff overhead  相似文献   
16.
The objective of this project was to study the interaction between HR1 and HR2, the stability of the complex formed, and to characterize the antibodies produced against monomeric HR1 and HR2 peptides as well as the HR1-HR2 complex. In this work, HR1 was mimicked by peptide N36, and HR2 was mimicked by peptide C34L and its analogues C34M2, C34M3, and C34D. Whereas C34M2 and C34M3 are partially composed of D-amino acids, C34D has same sequence as C34L, but is assembled entirely of D-amino acids. Using CD analysis, SPR assays, and gel filtration chromatography, we demonstrate the physical interaction between N36 and C34L and its analogues C34M2 and C34M3, but not C34D. We show that the HR1-HR2 complex is formed rapidly (<1?min) and remains stable, as demonstrated by its inability, in contrast to each free peptide, to inhibit the formation of syncytia. To generate antibodies with predetermined specificity against the transiently exposed intermediate that corresponds to the six-helix bundle structure, purified preformed HR1-HR2 complex was used, in parallel with monomeric HR1 and HR2 peptides, as immunogens in mice. Although the produced antibodies recognize total HIV-1 envelope glycoproteins in ELISA, they are unable to neutralize HIV-1-mediated fusion at 37?°C. However, if the incubation with these antibodies is carried out at 27?°C, a temperature that allows stabilization of the transient intermediate complex, anti-peptide antibodies are able to bind their corresponding domains in HeLa cells expressing HIV-1 gp41 in co-culture with HeLa CD4-CCR5/CXCR4 during the dynamic mechanism of membrane fusion. In agreement with the latter results, these antibodies, if previously incubated for 2?h at 27?°C, are able to strongly neutralize HIV-1 entry by membrane fusion, as shown by their ability to block the formation of syncytia.  相似文献   
17.
Three dinuclear coordination complexes generated from 1-n-butyl-2-((5-methyl-1H-pyrazole-3-yl)methyl)-1H-benzimidazole ( L ), have been synthesized and characterized spectroscopically and structurally by single crystal X-ray diffraction analysis. Reaction with iron(II) chloride and then copper(II) nitrate led to a co-crystal containing 78 % of [Cu(NO3)(μ-Cl)( L’ )]2 ( C1 ) and 22 % of [Cu(NO3)(μ-NO3)( L’ )]2 ( C2 ), where L was oxidized to a new ligand L . A mechanism is provided. Reaction with copper chloride led to the dinuclear complex [Cu(Cl)(μ-Cl)( L) ]2 ( C3 ). The presence of N−H⋅⋅⋅O and C−H⋅⋅⋅O intermolecular interactions in the crystal structure of C1 and C2 , and C−H⋅⋅⋅N and C−H⋅⋅⋅Cl hydrogen bonding in the crystal structure of C3 led to supramolecular structures that were confirmed by Hirshfeld surface analysis. The ligands and their complexes were tested for free radical scavenging activity and ferric reducing antioxidant power. The complex C1 / C2 shows remarkable antioxidant activities as compared to the ligand L and reference compounds.  相似文献   
18.
For machines? monitoring purpose, the classical motor current signature analysis has shown its weakness in distinguishing the eccentricity occurrence in presence of others mechanical faults. Although Park?s vector approach can cover this drawback, the high cost due to the requirement to use three current sensors associated with an advanced processing technique, makes it less desired by industrialists. In this paper, we suggest an alternative diagnosis method based on a suitable processing of the stray flux data. The experimental results have revealed the potential of a simple search coil for the detection and the distinction of the accurate eccentricity nature even in presence of similar mechanical faults.  相似文献   
19.
Abstract: Phenolics, flavonoids, anthocyanins, and tannins of pomegranate juices, obtained from 9 Tunisian ecotypes were quantified. Phenolics and flavonoids in the variety Tounsi (TN) (3299 mg gallic acid equivalents [GAE]/L and 636 mg quercetin equivalents [QE]/L of juice, respectively) were higher than in the variety Gabsi (GB) (1570 mg GAE/L and 135 mg QE/L of juice, respectively). The highest anthocyanins quantity was found in GB 2 with 156 mg cyanidin‐3‐glucoside equivalents (CGE)/L. TN 3 ecotype showed the highest tannins quantity with 2550 mg catechin equivalents (CE)/L of juice. TN 1 presented the highest radical‐scavenging activity (2, 2′‐azinobis‐3‐ethylbenzothiazoline‐6‐sulphonate [ABTS], IC50 [50% inhibition concentration] = 525 mg/L), as well as the highest concentration of micronutrient cations (potassium and sodium). A high correlation (R2= 0.80) between antioxidant capacity and proanthocyanin contents was found, this suggests that proanthocyanins are the principal contributor in the antioxidant capacity of pomegranate. Our data suggest also that the high concentrations of K+ and Na+ may play a role in the adaptation of pomegranate to arid environments.  相似文献   
20.
This paper focuses on the implementation of Multi-Criteria Decision Making (MCDM) methods to evaluate the workforce competence in apparel industry. In this study, the Analytic Hierarchy Process (AHP), the Weighted Sum Model (WSM) and the Weighted Product Model (WPM) are suggested to solve workforce selection problem. The use of these methods is expected to help choose the best operator among several alternatives. Based on three criteria, each worker is evaluated in each executed operation. The criteria are a Quality Index ‘QI’, an Activity ‘A’ and an Attendance Rate ‘AR’. Thanks to the MCDM methods, scores allowing an objective classification of operators are obtained. Experimental results on AHP, WSM and WPM methods show the same decisions with the same workers’ classification from the best to the worst alternative. The resulting database contributes to the line balancing optimization by choosing for each operation, and as far as possible, the most competent operator.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号