全文获取类型
收费全文 | 7021篇 |
免费 | 462篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 68篇 |
综合类 | 1篇 |
化学工业 | 1815篇 |
金属工艺 | 182篇 |
机械仪表 | 173篇 |
建筑科学 | 275篇 |
矿业工程 | 25篇 |
能源动力 | 268篇 |
轻工业 | 951篇 |
水利工程 | 47篇 |
石油天然气 | 42篇 |
无线电 | 503篇 |
一般工业技术 | 1522篇 |
冶金工业 | 318篇 |
原子能技术 | 56篇 |
自动化技术 | 1243篇 |
出版年
2024年 | 31篇 |
2023年 | 71篇 |
2022年 | 119篇 |
2021年 | 220篇 |
2020年 | 208篇 |
2019年 | 183篇 |
2018年 | 303篇 |
2017年 | 330篇 |
2016年 | 382篇 |
2015年 | 232篇 |
2014年 | 329篇 |
2013年 | 676篇 |
2012年 | 386篇 |
2011年 | 517篇 |
2010年 | 391篇 |
2009年 | 410篇 |
2008年 | 371篇 |
2007年 | 333篇 |
2006年 | 270篇 |
2005年 | 196篇 |
2004年 | 180篇 |
2003年 | 158篇 |
2002年 | 151篇 |
2001年 | 83篇 |
2000年 | 90篇 |
1999年 | 78篇 |
1998年 | 95篇 |
1997年 | 82篇 |
1996年 | 72篇 |
1995年 | 51篇 |
1994年 | 52篇 |
1993年 | 40篇 |
1992年 | 36篇 |
1991年 | 32篇 |
1990年 | 20篇 |
1989年 | 22篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 15篇 |
1985年 | 29篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 12篇 |
1979年 | 15篇 |
1978年 | 14篇 |
1977年 | 16篇 |
1976年 | 14篇 |
1974年 | 11篇 |
排序方式: 共有7489条查询结果,搜索用时 31 毫秒
101.
Nonnegative matrix factorization (NMF) is a data analysis technique used in a great variety of applications such as text mining, image processing, hyperspectral data analysis, computational biology, and clustering. In this letter, we consider two well-known algorithms designed to solve NMF problems: the multiplicative updates of Lee and Seung and the hierarchical alternating least squares of Cichocki et al. We propose a simple way to significantly accelerate these schemes, based on a careful analysis of the computational cost needed at each iteration, while preserving their convergence properties. This acceleration technique can also be applied to other algorithms, which we illustrate on the projected gradient method of Lin. The efficiency of the accelerated algorithms is empirically demonstrated on image and text data sets and compares favorably with a state-of-the-art alternating nonnegative least squares algorithm. 相似文献
102.
Jean-François Lalonde Alexei A. Efros Srinivasa G. Narasimhan 《International Journal of Computer Vision》2012,98(2):123-145
Given a single outdoor image, we present a method for estimating the likely illumination conditions of the scene. In particular, we compute the probability distribution over the sun position and visibility. The method relies on a combination of weak cues that can be extracted from different portions of the image: the sky, the vertical surfaces, the ground, and the convex objects in the image. While no single cue can reliably estimate illumination by itself, each one can reinforce the others to yield a more robust estimate. This is combined with a data-driven prior computed over a dataset of 6 million photos. We present quantitative results on a webcam dataset with annotated sun positions, as well as quantitative and qualitative results on consumer-grade photographs downloaded from Internet. Based on the estimated illumination, we show how to realistically insert synthetic 3-D objects into the scene, and how to transfer appearance across images while keeping the illumination consistent. 相似文献
103.
104.
Alessio Franci Antoine Chaillet Elena Panteley Fran?oise Lamnabhi-Lagarrigue 《Mathematics of Control, Signals, and Systems (MCSS)》2012,24(1-2):169-217
Motivated by neuroscience applications, and in particular by the deep brain stimulation treatment for Parkinson’s disease, we have recently derived a simplified model of an interconnected neuronal population under the effect of its mean-field proportional feedback. In this paper, we rely on that model to propose conditions under which proportional mean-field feedback achieves either oscillation inhibition or desynchronization. More precisely, we show that for small natural frequencies, this scalar control signal induces an inhibition of the collective oscillation. For the closed-loop system, this situation corresponds to a fixed point which is shown to be almost globally asymptotically stable in the fictitious case of zero natural frequencies and all-to-all coupling and feedback. In the case of an odd number of oscillators, this property is shown to be robust to small natural frequencies and heterogencities in both the coupling and feedback topology. On the contrary, for large natural frequencies, we show that scalar proportional mean-field feedback is able to induce desynchronization. After having recalled a formal definition for desynchronization, we show how it can be induced in a network of originally synchronized oscillators. 相似文献
105.
The review of literature in sociology and distributed artificial intelligence reveals that the occurrence of conflict is a remarkable precursor to the disruption of multi-agent systems. The study of this concept could be applied to human factors concerns, as man-system conflict appears to provoke perseveration behavior and to degrade attentional abilities with a trend to excessive focus. Once entangled in such conflicts, the human operator will do anything to succeed in his current goal even if it jeopardizes the mission. In order to confirm these findings, an experimental setup, composed of a real unmanned ground vehicle, a ground station is developed. A scenario involving an authority conflict between the participants and the robot is proposed. Analysis of the effects of the conflict on the participants' cognition and arousal is assessed through heart-rate measurement (reflecting stress level) and eye-tracking techniques (index of attentional focus). Our results clearly show that the occurrence of the conflict leads to perseveration behavior and can induce higher heart rate as well as excessive attentional focus. These results are discussed in terms of task commitment issues and increased arousal. Moreover, our results suggest that individual differences may predict susceptibility to perseveration behavior. 相似文献
106.
Caroline Kulcsár Henri-François Raynaud Cyril Petit Jean-Marc Conan 《Automatica》2012,48(9):1939-1954
Adaptive Optics (AO) systems enable to compensate the adverse effects of atmospheric turbulence on ground-based telescopes’ images in real time, using a deformable mirror (DM) inserted in the telescope’s optical path, and measurements provided by a wavefront sensor (WFS). This paper revisits minimum-variance (MV) control design for astronomical AO systems in a state-space framework. It presents a survey of the modeling and control issues arising in this multi-variable disturbance rejection problem. In a linear time-invariant framework, and under some mild assumptions, the optimal solution to MV control for AO systems is shown to be a discrete-time LQG controller. This result holds for a DM with instantaneous response, and for a fairly general class of DM’s dynamics. The state-space approach is extended to Wide-field Adaptive Optics (WfAO) configurations involving several DMs and/or WFSs. Integral-action control used in existing AO systems is compared with the LQG controller. Experimental WfAO results obtained on a laboratory test bench are presented, showing significant improvement in performance. Finally, open issues and perspectives of applicative and/or theoretical interests are discussed. 相似文献
107.
In the design of concrete structures, estimation of the deflection of the structural members under the service loads is often
a critical factor. Strains and displacements are linked to the tension stiffening effect, which is not quantified in the standards.
The CEB-FIP model code proposes an interesting simplified method for evaluating the concrete tension stiffening effect on
reinforced concrete behavior. One of the parameters which enables the mechanical contribution of the concrete to be quantified
is the effective tensile active section of the reinforced concrete beams. In this paper, a new method for calculating the
effective tensile active section A
ct.ef is proposed. The calculation is based on an analytical model of stress distribution in the full depth of the concrete section.
An experimental study on several reinforced concrete beams is reported. The results show that the new proposed model enhances
the accuracy of the beam deflection predictions significantly. 相似文献
108.
This paper proposes a model of the mechanical behaviour of corroded reinforced concrete members subjected to bending under
service load. The model is based on the formulation of a macro-element to be used in FEM analysis, having a length equal to
the distance between two consecutive flexural cracks and a cross-section equal to the member cross-section. The mechanical
formulation is directly written in generalized variables (bending moment and curvature) and is based on the concept of the
transfer length necessary for the transmission of tensile load from re-bar to tensile concrete thanks to the bond. It is thus
possible to take into account the effect of reinforcement corrosion on the bond between re-bar and concrete, by increasing
the transfer length versus intensity of corrosion. The variation of the transfer length versus corrosion is expressed using
a scalar damage parameter. A first experimental validation is performed on a 17-year-old beam kept in a chloride environment
under its service load. 相似文献
109.
Viaduct roads have wide application in big cities with high traffic loads, in order to decrease traffic density and to connect
subways to highways. Viaduct roads are constructed using steel structures instead of concrete ones in areas of earthquake
risks. The low weight of steel structures however causes problems such as vibration and noise. There is increasing demand
especially in populated areas to suppress vibration and noise on highway roads for reducing noise-related environmental pollution.
In this study, bending vibrations of rectangular plate viaduct roads, which are supported by six fixed elements of rectangular
cross-sectional elements are considered. Natural frequencies are obtained using the Rayleigh-Ritz technique, finite elements
analysis, experimentally and neural networks (NN). 相似文献
110.
French Douglas J.; No?l Marc; Vigneau Fran?ois; French Julie A.; Cyr Chantal P.; Evans R. Thomas 《Canadian Metallurgical Quarterly》2005,37(3):181
This study examined the psychometric properties of the PCS-CF, a French-Canadian adaptation of the Pain Catastrophizing Scale (Sullivan, Bishop & Pivik, 1995). One hundred and twenty undergraduate students (83 women; 37 men) completed the PCS-CF and measures of anxiety and depression prior to immersing their hand in ice water for 1-minute. A subset of 39 participants (28 females; 11 males) also completed a second pain task involving an ascending series of electrocutaneous stimulations. Participants' verbal and non-verbal pain behaviours during and immediately after the immersion task were recorded and subsequently independently coded. Reliability analyses revealed that the PCS-CF total score and subscale scores have a high degree of internal consistency and test-retest reliabilities that are comparable to the original Pain Catastrophizing Scale. PCS-CF scores were associated with higher levels of self-reported pain during the ice water immersion task and decreased pain tolerance during electrocutaneous stimulation. Individuals with elevated PCS-CF scores also displayed a more diverse repertoire of pain behaviours than their low PCS-CF counterparts. Previous findings that catastrophizing scores are able to discriminate criterion groups of males and females were also replicated. Given the highly correlated factors obtained in analyses of the dimensionality of the PCS-CF, the structure suggested by the authors of the original scale is only partially supported. However, the results taken together suggest that the PCS-CF is both a reliable and valid measure of the pain catastrophizing construct that is psychometrically comparable to the original PCS. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献