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排序方式: 共有686条查询结果,搜索用时 31 毫秒
11.
Georg Menge Hannes Lorenz Zongwen Fu Franziska Eichhorn Florian Schader Kyle G. Webber Tobias Fey Peter Greil Nahum Travitzky 《Advanced Engineering Materials》2018,20(7)
12.
Fiber-optic transmission of Q-switched ruby laser pulses is limited by fiber damage owing to the high laser-beam intensities. Pulse stretching with a semiconductor-based control circuit for the Pockels cell of the ruby laser to reduce the peak intensities is described. Pulses with durations from 200 ns to 1 μs and a coherence length of ~3 m were generated. These pulses were coupled into multimode optical fibers to investigate the transmission characteristics and the limits of transmittable pulse energies. Stretched pulses can be transmitted in quartz fibers with a 600-μm core diameter to pulse energies of 300 mJ, which is an increase by a factor of 4 compared with standard Q-switched pulses. It is expected that beam guiding of ruby laser pulses by fiber optics will significantly facilitate the use of holographic interferometry in technical applications such as vibration analysis. 相似文献
13.
Kuk-Jin Yoon Emmanuel Prados Peter Sturm 《International Journal of Computer Vision》2010,86(2-3):192-210
We propose a generative model based method for recovering both the shape and the reflectance of the surface(s) of a scene from multiple images, assuming that illumination conditions and cameras calibration are known in advance. Based on a variational framework and via gradient descents, the algorithm minimizes simultaneously and consistently a global cost functional with respect to both shape and reflectance. The motivations for our approach are threefold. (1) Contrary to previous works which mainly consider specific individual scenarios, our method applies indiscriminately to a number of classical scenarios; in particular it works for classical stereovision, multiview photometric stereo and multiview shape from shading. It works with changing as well as static illumination. (2) Our approach naturally combines stereo, silhouette and shading cues in a single framework. (3) Moreover, unlike most previous methods dealing with only Lambertian surfaces, the proposed method considers general dichromatic surfaces. We verify the method using various synthetic and real data sets. 相似文献
14.
Falk Hüffner Christian Komusiewicz Hannes Moser Rolf Niedermeier 《Theory of Computing Systems》2010,47(1):196-217
We initiate the first systematic study of the NP-hard Cluster Vertex Deletion (CVD) problem (unweighted and weighted) in terms of fixed-parameter algorithmics. In the unweighted case, one searches for a minimum
number of vertex deletions to transform a graph into a collection of disjoint cliques. The parameter is the number of vertex
deletions. We present efficient fixed-parameter algorithms for CVD applying the fairly new iterative compression technique.
Moreover, we study the variant of CVD where the maximum number of cliques to be generated is prespecified. Here, we exploit
connections to fixed-parameter algorithms for (weighted) Vertex Cover. 相似文献
15.
Walter Lang Frank Jakobs Elena Tolstosheeva Hannes Sturm Azat Ibragimov Antonia Kesel Dirk Lehmhus Ursula DickeAuthor vitae 《Sensors and actuators. A, Physical》2011,171(1):3-11
Ubiquitous computing is about to become part of our everyday lives by integrating hundreds of “invisible” to us computing devices in our environment, so that they can unobtrusively and constantly assist us. This will imply more and smaller “invisible” sensors, homogeneously distributed and at the same time densely packed in host materials, responding to various stimuli and immediately delivering information. In order to reach this aim, the embedded sensors should be integrated within the host material, heading towards sensorial materials. The first step is to omit all parts that are not needed for the sensorial task and to find new solutions for a gentle integration. This is what we call function scale integration. The paper discusses sensor embedding in the human hand as an example of integration in nature, new technological applications and main challenges associated with this approach. 相似文献
16.
We present a tracking method where full camera position and orientation is tracked from intensity differences in a video sequence. The camera pose is calculated based on 3D planes, and hence does not depend on point correspondences. The plane based formulation also allows additional constraints to be naturally added, e.g., perpendicularity between walls, floor and ceiling surfaces, co-planarity of wall surfaces etc. A particular feature of our method is that the full 3D pose change is directly computed from temporal image differences without making a commitment to a particular intermediate (e.g., 2D feature) representation. We experimentally compared our method with regular 2D SSD tracking and found it more robust and stable. This is due to 3D consistency being enforced even in the low level registration of image regions. This yields better results than first computing (and hence committing to) 2D image features and then from these compute 3D pose. 相似文献
17.
Tardif Jean-Philippe Sturm Peter Trudeau Martin Roy Sebastien 《IEEE transactions on pattern analysis and machine intelligence》2009,31(9):1552-1566
We present algorithms for plane-based calibration of general radially distorted cameras. By this, we understand cameras that have a distortion center and an optical axis such that the projection rays of pixels lying on a circle centered on the distortion center form a right viewing cone centered on the optical axis. The camera is said to have a single viewpoint (SVP) if all such viewing cones have the same apex (the optical center); otherwise, we speak of NSVP cases. This model encompasses the classical radial distortion model [5], fisheyes, and most central or noncentral catadioptric cameras. Calibration consists in the estimation of the distortion center, the opening angles of all viewing cones, and their optical centers. We present two approaches of computing a full calibration from dense correspondences of a single or multiple planes with known euclidean structure. The first one is based on a geometric constraint linking viewing cones and their intersections with the calibration plane (conic sections). The second approach is a homography-based method. Experiments using simulated and a broad variety of real cameras show great stability. Furthermore, we provide a comparison with Hartley-Kang's algorithm [12], which, however, cannot handle such a broad variety of camera configurations, showing similar performance. 相似文献
18.
Bahman Hekmatshoar Alex Z. Kattamis Kunigunde Cherenack Sigurd Wagner James C. Sturm 《Journal of the Society for Information Display》2008,16(1):183-188
Abstract— The direct voltage programming of active‐matrix organic light‐emitting‐diode (AMOLED) pixels with n‐channel amorphous‐Si (a‐Si) TFTs requires a contact between the driving TFT and the OLED cathode. Current processing constraints only permit connecting the driving TFT to the OLED anode. Here, a new “inverted” integration technique which makes the direct programming possible by connecting the driver n‐channel a‐Si TFT to the OLED cathode is demonstrated. As a result, the pixel drive current increases by an order of magnitude for the same data voltages and the pixel data voltage for turn‐on drops by several volts. In addition, the pixel drive current becomes independent of the OLED characteristics so that OLED aging does not affect the pixel current. Furthermore, the new integration technique is modified to allow substrate rotation during OLED evaporation to improve the pixel yield and uniformity. The new integration technique is important for realizing active‐matrix OLED displays with a‐Si technology and conventional bottom‐anode OLEDs. 相似文献
19.
Generating feature spaces for linear algorithms with regularized sparse kernel slow feature analysis
Wendelin B?hmer Steffen Grünew?lder Hannes Nickisch Klaus Obermayer 《Machine Learning》2012,89(1-2):67-86
Without non-linear basis functions many problems can not be solved by linear algorithms. This article proposes a method to automatically construct such basis functions with slow feature analysis (SFA). Non-linear optimization of this unsupervised learning method generates an orthogonal basis on the unknown latent space for a given time series. In contrast to methods like PCA, SFA is thus well suited for techniques that make direct use of the latent space. Real-world time series can be complex, and current SFA algorithms are either not powerful enough or tend to over-fit. We make use of the kernel trick in combination with sparsification to develop a kernelized SFA algorithm which provides a powerful function class for large data sets. Sparsity is achieved by a novel matching pursuit approach that can be applied to other tasks as well. For small data sets, however, the kernel SFA approach leads to over-fitting and numerical instabilities. To enforce a stable solution, we introduce regularization to the SFA objective. We hypothesize that our algorithm generates a feature space that resembles a Fourier basis in the unknown space of latent variables underlying a given real-world time series. We evaluate this hypothesis at the example of a vowel classification task in comparison to sparse kernel PCA. Our results show excellent classification accuracy and demonstrate the superiority of kernel SFA over kernel PCA in encoding latent variables. 相似文献
20.
Jér?me?CourchayEmail author Arnak?S.?Dalalyan Renaud?Keriven Peter?Sturm 《International Journal of Computer Vision》2012,97(1):71-90
A technique for calibrating a network of perspective cameras based on their graph of trifocal tensors is presented. After
estimating a set of reliable epipolar geometries, a parameterization of the graph of trifocal tensors is proposed in which
each trifocal tensor is linearly encoded by a 4-vector. The strength of this parameterization is that the homographies relating
two adjacent trifocal tensors, as well as the projection matrices depend linearly on the parameters. Two methods for estimating
these parameters in a global way taking into account loops in the graph are developed. Both methods are based on sequential
linear programming: the first relies on a locally linear approximation of the polynomials involved in the loop constraints
whereas the second uses alternating minimization. Both methods have the advantage of being non-incremental and of uniformly
distributing the error across all the cameras. Experiments carried out on several real data sets demonstrate the accuracy
of the proposed approach and its efficiency in distributing errors over the whole set of cameras. 相似文献