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1.
Stereological measurements were performed to characterize the indentation crack path in a cubic zirconia-10 vol% alumina (c-ZrO2 -10 vol% Al2 O3 ) composite. Cracks were generated using Vickers indentation, and the crack propagation behavior was characterized as a function of the indentation loading/unloading rates. Cracks that were produced by Vickers indentation formed at higher crack velocities as the loading/unloading rates increased. The amount of contact between the crack and the Al2 O3 particles increased as the indentation rate decreased. The total number of crack-particle interactions per unit crack length also increased as the indentation rate decreased, because of an increase in the number of particles that were fractured per unit crack length, whereas the number of particles that were debonded remained relatively constant as the indentation rate changed. These results suggest that residual thermal mismatch stresses have predominant control of the crack path at lower crack velocities (low indentation loading/unloading rate), whereas elastic mismatch stresses predominate at higher crack velocities (high indentation loading/unloading rate). 相似文献
2.
High-throughput drilling of titanium alloys 总被引:3,自引:1,他引:3
Rui Li Parag Hegde Albert J. Shih 《International Journal of Machine Tools and Manufacture》2007,47(1):63-74
Experiments of high-throughput drilling of Ti–6Al–4V at 183 m/min cutting speed and 156 mm3/s material removal rate (MRR) using a 4 mm diameter WC–Co spiral point drill were conducted. The tool material and geometry and drilling process parameters, including cutting speed, feed, and fluid supply, were studied to evaluate the effect on drill life, thrust force, torque, energy, and burr formation. The tool wear mechanism, hole surface roughness, and chip light emission and morphology for high-throughput drilling were investigated. Supplying the cutting fluid via through-the-drill holes has proven to be a critical factor for drill life, which can be increased by 10 times compared to that of dry drilling at 183 m/min cutting speed and 0.051 mm/rev feed. Under the same MRR of 156 mm3/s with a doubled feed of 0.102 mm/rev (91 m/min cutting speed), over 200 holes can be drilled. The balance of cutting speed and feed is essential to achieve long drill life and good hole surface roughness. This study demonstrates that, using proper drilling process parameters, spiral point drill geometry, and fine-grained WC–Co tool material, the high-throughput drilling of Ti alloy is technically feasible. 相似文献
3.
Parag Chaudhuri George Papagiannakis Nadia Magnenat-Thalmann 《The Visual computer》2008,24(7-9):525-533
In this paper we present a new character animation technique in which the animation adapts itself based on the change in the user’s perspective, so that when the user moves and their point of viewing the animation changes, then the character animation adapts itself in response to that change. The resulting animation, generated in real-time, is a blend of key animations provided a priori by the animator. The blending is done with the help of efficient dual-quaternion transformation blending. The user’s point of view is tracked using either computer vision techniques or a simple user-controlled input modality, such as mouse-based input. This tracked point of view is then used to suitably select the blend of animations. We show a way to author and use such animations in both virtual as well as augmented reality scenarios and demonstrate that it significantly heightens the sense of presence for the users when they interact with such self adaptive animations of virtual characters. 相似文献
4.
In this paper, we propose a software defect prediction model learning problem (SDPMLP) where a classification model selects appropriate relevant inputs, from a set of all available inputs, and learns the classification function. We show that the SDPMLP is a combinatorial optimization problem with factorial complexity, and propose two hybrid exhaustive search and probabilistic neural network (PNN), and simulated annealing (SA) and PNN procedures to solve it. For small size SDPMLP, exhaustive search PNN works well and provides an (all) optimal solution(s). However, for large size SDPMLP, the use of exhaustive search PNN approach is not pragmatic and only the SA–PNN allows us to solve the SDPMLP in a practical time limit. We compare the performance of our hybrid approaches with traditional classification algorithms and find that our hybrid approaches perform better than traditional classification algorithms. 相似文献
5.
Distributed problem‐solving (DPS) systems use a framework of human organizational notions and principles of intelligent systems to solve complex problems. Human organizational notions are used to decompose a complex problem into sub‐problems that can be solved using intelligent systems. The solutions of these sub‐problems are combined to solve the original complex problem. In this paper, we propose a DPS system for probabilistic estimation of software development effort. Using a real‐world software engineering dataset, we compare the performance of the DPS system with a neural network (NN) and show that the performance of the DPS system is equal to or better than that of the NN with the additional benefits of modularity, probabilistic estimates, greater interpretability, flexibility and capability to handle incomplete input data. 相似文献
6.
Parag C. Pendharkar 《Expert systems with applications》2013,40(10):3918-3925
We consider a feature selection problem where the decision-making objective is to minimize overall misclassification cost by selecting relevant features from a training dataset. We propose a two-stage solution approach for solving misclassification cost minimizing feature selection (MCMFS) problem. Additionally, we propose a maximum-margin genetic algorithm (MMGA) that maximizes margin of separation between classes by taking into account all examples as opposed to maximizing margin of separation using a few support vectors. Feature selection is carried out by either an exhaustive or a heuristic simulated annealing approach in the first stage and a cost sensitive classification using either MMGA or cost sensitive support vector machines (SVM) in the second stage. Using simulated and real-world data sets and different misclassification cost matrices, we test our two-stage approach for solving the MCMFS problem. Our results indicate that feature selection plays an important role when misclassification cost asymmetries increase and the MMGA shows equal or better performance than the SVM. 相似文献
7.
All-optical two input parallel logic gates with bacteriorhodopsin (BR) protein have been designed based on nonlinear intensity-induced excited-state absorption. Amplitude modulation of a continuous wave (CW) probe laser beam transmission at 640 nm corresponding to the peak absorption of O intermediate state through BR, by a modulating CW pump laser beam at 570 nm corresponding to the peak absorption of initial BR state has been analyzed considering all six intermediate states in its photocycle using the rate equation approach. The transmission characteristics have been shown to exhibit a dip, which is sensitive to normalized small-signal absorption coefficient (/spl beta/), rate constants of O and N intermediate states and absorption of the O state at 570 nm. There is an optimum value of /spl beta/ for a given pump intensity range for which maximum modulation can be achieved. It is shown that 100% modulation can be achieved if the initial state of BR does not absorb the probe beam. The results have been used to design low-power all-optical parallel NOT, AND, OR, XNOR, and the universal NAND and NOR logic gates for two cases: 1) only changing the output threshold and 2) considering a common threshold with different /spl beta/ values. 相似文献
8.
Clinical disorders of language, known as aphasia, cause impaired comprehension of speech in written and spoken forms. This impairment is due to the patients inability to process semantics that arise from sequence independent co-occurrence of words with content in a short-term memory (STM) of preceding words. If Wi is the immediately forthcoming word in input to the patient, STM, in the context of this disorder, consists of a window, STMWin, that contains the k words that immediately precede Wi. We use a generative approach to model semantics that ensue from the co-occurrence of Wi and STMWin, and view these semantics as the output of a random process with parameters . The model uses supervised learning to maximize the likelihood of , given labeled content in STMWin. Experimental validation on standard text classification data sets gives an accuracy that is comparable to, or better than, that obtained using support vector machines (SVMs). 相似文献
9.
Bowang Xiao Qigui Wang Parag Jadhav Keyu Li 《Journal of Materials Processing Technology》2010,210(14):2023-2028
The influence of quenching orientation and agitation conditions on heat transfer of aluminum alloys during water quenching was experimentally investigated with a test casting. The results indicate that heat transfer in water quenching of casting aluminum alloy consists of film boiling, nucleate boiling and convection stages. The highest heat transfer coefficients (HTC) are observed in the nucleate boiling, while the lowest is in the convective cooling stage. The heat transfer coefficients on the horizontal surfaces facing down during quenching are lower than those of other surfaces regardless whether the water is agitated or not. Agitation enhances heat transfer process especially when castings are at high temperatures and heat transfer process is in the film boiling stage. 相似文献
10.
The effects of milling time on the rheological behavior of 70-vol% loaded fused silica slurries were studied. A transition from shear thickening to shear thinning behavior was observed with milling time. Slurry viscosity and thixotropy attained a minimum after 18 h of milling and remained almost unchanged with additional milling. Infrared spectroscopy and particle surface charge measurements confirmed the development of increasing amount of surface hydroxide and surface charge respectively with progress in milling time, leading to shear thinning behavior. An initial static aging treatment of 24 h aided the development of silanol groups, indicating that the milling time can be reduced to save energy and time. 相似文献