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51.
I. G. Siddhalingeshwar A. Behera R. Mitra M. Chakraborty 《Transactions of the Indian Institute of Metals》2009,62(4-5):379-382
In situ Al-4.5Cu-5TiB2 composite has been processed through stir casting method, in which, the TiB2 particles have been precipitated in situ by mixed salt route involving reactions between K2TiF6 and KBF4.The as-cast specimens containing 20 volume percent liquid content have been subjected to three mushy state roll passes, each leading to 5 percent reduction in thickness. The grain structure has been found to be globular in the mushy state rolled composites. Measurements along the cross-section have shown decrease in average grain size and increase in hardness, as one proceeds along the direction of rolling. On the other hand, grain size and hardness have been found to be more or less similar, when compared for sections perpendicular to the rolling direction. 相似文献
52.
Sharmilee Pal V. V. Bhanuprasad R. Mitra K. K. Ray 《Metallurgical and Materials Transactions A》2009,40(13):3171-3185
The tensile creep behavior of powder metallurgy (P/M)–processed and hot-rolled commercially pure Al and Al-5 or Al-10 vol
pct SiC particulate composites has been evaluated after subjecting to 0, 2, and 8 thermal cycles between 500 °C and 0 °C with
rapid quenching. The images of microstructures obtained using scanning and transmission electron microscopy as well as changes
in the electrical resistivity, Young’s modulus, and microhardness have been examined in the samples subjected to thermal cycling,
in order to compare the effects of structural damage and strengthening by dislocation generation. The damage is caused by
voids formed by vacancy coalescence, and is more severe in pure Al than in Al-SiCp composites, because the particle-matrix interfaces in the composites act as effective sinks for vacancies. Creep tests have
shown that the application of 2 thermal cycles lowers the creep strain rates in both pure Al and Al-SiCp composites. However, the creep resistance of pure Al gets significantly deteriorated, unlike the mild deterioration in the
Al-5 SiCp composite, while the time to rupture for the Al-10 SiCp composite is increased. The dislocation structure and subgrain sizes in the Al and in the matrices of the Al-SiCp composites in the as-rolled condition, after thermal cycling, and after creep tests, have been compared and related to the
creep behavior. The dimple sizes of the crept fracture surfaces appear to be dependent on the void density, tertiary component
of strain, and time to rupture. 相似文献
53.
54.
Rough-fuzzy collaborative clustering. 总被引:3,自引:0,他引:3
Sushmita Mitra Haider Banka Witold Pedrycz 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2006,36(4):795-805
In this study, we introduce a novel clustering architecture, in which several subsets of patterns can be processed together with an objective of finding a common structure. The structure revealed at the global level is determined by exchanging prototypes of the subsets of data and by moving prototypes of the corresponding clusters toward each other. Thereby, the required communication links are established at the level of cluster prototypes and partition matrices, without hampering the security concerns. A detailed clustering algorithm is developed by integrating the advantages of both fuzzy sets and rough sets, and a measure of quantitative analysis of the experimental results is provided for synthetic and real-world data. 相似文献
55.
Density-based multiscale data condensation 总被引:10,自引:0,他引:10
Mitra P. Murthy C.A. Pal S.K. 《IEEE transactions on pattern analysis and machine intelligence》2002,24(6):734-747
A problem gaining interest in pattern recognition applied to data mining is that of selecting a small representative subset from a very large data set. In this article, a nonparametric data reduction scheme is suggested. It attempts to represent the density underlying the data. The algorithm selects representative points in a multiscale fashion which is novel from existing density-based approaches. The accuracy of representation by the condensed set is measured in terms of the error in density estimates of the original and reduced sets. Experimental studies on several real life data sets show that the multiscale approach is superior to several related condensation methods both in terms of condensation ratio and estimation error. The condensed set obtained was also experimentally shown to be effective for some important data mining tasks like classification, clustering, and rule generation on large data sets. Moreover, it is empirically found that the algorithm is efficient in terms of sample complexity 相似文献
56.
A better understanding of high rate anodic dissolution processes is urgently required for electrochemical micromachining (EMM) to become a widely employed manufacturing process in the electronic and precision manufacturing industries particularly in the micromanufacturing domain. A successful attempt has been made to develop an EMM setup for carrying out in depth independent research for achieving satisfactory control of electrochemical machining process parameters to meet the micromachining requirements. The developed EMM setup mainly consists of various sub-components and systems, e.g., mechanical machining unit, microtooling system, electrical power and controlling system and controlled electrolyte flow system, etc. All these system components are integrated in such a way that the developed EMM system setup will be capable of performing basic and fundamental research in the area of EMM fulfilling the requirements of micromachining objectives. 相似文献
57.
Claude-Alain Gobet Sanjit K. Mitra Antonio Petraglia 《International Journal of Circuit Theory and Applications》1992,20(1):47-62
The low-sensitivity property of IIR digital filters designed using a parallel connection of two allpass sections has already been demonstrated in the past few years. This property is closely related to the use of a particular type of allpass structures, called structurally lossless networks, which remain allpass regardless of the coefficient quantization. In this paper we provide a general theory for the synthesis of low-passband-sensitivity switched capacitor (SC) filters using a similar technique. the design of stray-insensitive structurally allpass SC sections is emphasized, ensuring the passivity property for the overall filter. Design examples are presented with computer simulations and experimental results to compare the performance of the different proposed structures. Analytical sensitivity calculations are also derived yielding useful formulae for the prediction of the filter sensitivities with respect to capacitor ratios, particularly in the stopband. 相似文献
58.
Chemically deposited zinc oxide thin film gas sensor 总被引:4,自引:0,他引:4
Zinc oxide (ZnO) thin films were prepared by a low cost chemical deposition technique using sodium zincate bath. Structural characterizations by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM) indicate the formation of ZnO films, containing 0.05–0.50 m size crystallites, with preferred c-axis orientation. The electrical conductance of the ZnO films became stable and reproducible in the 300–450 K temperature range after repeated thermal cyclings in air. Palladium sensitised ZnO films were exposed to toxic and combustible gases e.g., hydrogen (H2), liquid petroleum gas (LPG), methane (CH4) and hydrogen sulphide (H2S) at a minimum operating temperature of 150 °C; which was well below the normal operating temperature range of 200–400 °C, typically reported in literature for ceramic gas sensors. The response of the ZnO thin film sensors at 150 °C, was found to be significant, even for parts per million level concentrations of CH4 (50 ppm) and H2S (15 ppm). 相似文献
59.
Modern imaging techniques for probing brain function, including functional magnetic resonance imaging, intrinsic and extrinsic contrast optical imaging, and magnetoencephalography, generate large data sets with complex content. In this paper we develop appropriate techniques for analysis and visualization of such imaging data to separate the signal from the noise and characterize the signal. The techniques developed fall into the general category of multivariate time series analysis, and in particular we extensively use the multitaper framework of spectral analysis. We develop specific protocols for the analysis of fMRI, optical imaging, and MEG data, and illustrate the techniques by applications to real data sets generated by these imaging modalities. In general, the analysis protocols involve two distinct stages: "noise" characterization and suppression, and "signal" characterization and visualization. An important general conclusion of our study is the utility of a frequency-based representation, with short, moving analysis windows to account for nonstationarity in the data. Of particular note are 1) the development of a decomposition technique (space-frequency singular value decomposition) that is shown to be a useful means of characterizing the image data, and 2) the development of an algorithm, based on multitaper methods, for the removal of approximately periodic physiological artifacts arising from cardiac and respiratory sources. 相似文献
60.
Development and comparison of models for light-pulse transport through scattering-absorbing media 总被引:1,自引:0,他引:1
We examine the transport of short light pulses through scattering-absorbing media through different approximate mathematical models. It is demonstrated that the predicted optical signal characteristics are significantly influenced by the various models considered, such as P(N) expansion, two-flux, and discrete ordinates. The effective propagation speed of the scattered radiation, the predicted magnitudes of the transmitted and backscattered fluxes, and the temporal shape and spread of the optical signals are functions of the models used to represent the intensity distributions. A computationally intensive direct numerical integration scheme that does not utilize approximations is also implemented for comparison. Results of some of the models asymptotically approach those of direct numerical simulation if the order of approximation is increased. In this study therefore we identify the importance of model selection in analyzing short-pulse laser applications such as optical tomography and remote sensing and highlight the parameters, such as wave speed, that must be examined before a model is adopted for analysis. 相似文献