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31.
Giovannina Albano Ciro d'Apice Giuliano Gargiulo Benedetto Piccoli 《International journal of control》2013,86(10):1020-1032
Recently, significant interest has been raised in the study of hybrid systems. In this paper we analyse the performance of some hybrid controls to stabilize a model problem, comparing it with classical methods. We used computer simulations as well as analytic arguments which revealed the presence of periodic orbits for the considered hybrid dynamics. Existence and stability of the latter have also been considered in the framework of a single dynamical system on a suitable manifold (indeed, a stratified set), called the hybrid manifold. 相似文献
32.
Christopher M. Gribble Graham Peter Matthews Giuliano M. Laudone Andrew Turner Cathy J. Ridgway Joachim Schoelkopf Patrick A.C. Gane 《Chemical engineering science》2011,(16):3701
We present fundamental and quantitative comparisons between the techniques of porometry (or flow permporometry), porosimetry, image analysis and void network modelling for seven types of filter, chosen to encompass the range of simple to complex void structure. They were metal, cellulose and glass fibre macro- and meso-porous filters of various types. The comparisons allow a general re-appraisal of the limitations of each technique for measuring void structures. Porometry is shown to give unrealistically narrow void size distributions, but the correct filtration characteristic when calibrated. Shielded mercury porosimetry can give the quaternary (sample-level anisotropic) characteristics of the void structure. The first derivative of a mercury porosimetry intrusion curve is shown to underestimate the large number of voids, but this error can be largely corrected by the use of a void network model. The model was also used to simulate the full filtration characteristic of each sample, which agreed with the manufacturer's filtration ratings. The model was validated through its correct a priori simulation of absolute gas permeabilities for track etch, cellulose nitrate and sintered powder filters. 相似文献
33.
P. A. Giuliano Albo R. M. Gavioso G. Benedetto 《International Journal of Thermophysics》2010,31(7):1248-1258
A mathematical method is derived within the framework of classical Lagrangian field theory, which is suitable for the determination
of the eigenstates of acoustic resonators of nearly spherical shape. The method is based on the expansion of the Helmholtz
differential operator and the boundary condition in a power series of a small geometrical perturbation parameter e{\epsilon} . The method extends to orders higher than e2{\epsilon^2} the calculation of the perturbed acoustic eigenvalues, which was previously limited by the use of variational formalism and
the methods of Morse and Ingard. A specific example is worked out for radial modes of a prolate spheroid, with the frequency
perturbation calculated to order e3{\epsilon^3} . A possible strategy to tackle the problem of calculating the acoustic eigenvalues for cavities presenting non-smooth geometrical
imperfections is also described. 相似文献
34.
35.
Giovanni Di Nicola Giuliano Giuliani Fabio Polonara Giulio Santori Roman Stryjek 《International Journal of Thermophysics》2010,31(10):1880-1887
A recently built experimental setup was employed for the estimation of the solid–liquid equilibria of alternative refrigerant systems. In this paper two binaries, i.e., carbon dioxide + trifluoromethane (CO2 + R23) and nitrous oxide + trifluoromethane (N2O + R23), were studied down to temperatures of 117 K. In order to check the reliability of the apparatus, the triple points of the pure fluids contained in the mixture were measured, revealing good consistency with the literature. The results obtained for the mixtures were interpreted by means of the Schröder equation. 相似文献
36.
Relation Between the North-Atlantic Oscillation and Hydroclimatic Conditions in Mediterranean Areas 总被引:1,自引:0,他引:1
Luigia Brandimarte Giuliano Di Baldassarre Guendalina Bruni Paolo D’Odorico Alberto Montanari 《Water Resources Management》2011,25(5):1269-1279
Mediterranean basins are known for their susceptibility to water stress conditions resulting from a reduction in winter-season
precipitation. This region is also prone to the effects of the North Atlantic Oscillation (NAO), a large-scale climatic pattern
associated with a displacement of air mass between the arctic and the subtropical Atlantic. Even though previous studies have
demonstrated the impact of the NAO on winter climate conditions in Europe and Northern Africa, it is still unclear to what
extent the NAO is related to hydroclimatic patterns in Mediterranean areas and whether it can explain its recent drought history.
To this end, this study investigates the interdependence between the NAO and winter precipitation, river flow and temperature
in two Mediterranean regions: Southern Italy and Nile Delta (Egypt). The outcomes show the presence of significant connections
between the NAO, winter rainfall and river discharge. 相似文献
37.
A. Zucchelli M. Dignatici M. Montorsi R. Carlotti C. Siligardi 《Journal of the European Ceramic Society》2012,32(10):2243-2251
In this study, phase transformation of the vitreous enamel and the interface steel–enamel during firing was analyzed. The thermal transformation of vitreous coating on steel was observed “in situ” with an environmental scanning electron microscopy and the mechanical properties of the steel–enamel interface were studied by using a nano-indenter. The interface reactions and the resulting structure can strongly influence the adhesion mechanism between glass coatings and the metal substrate. An in-depth investigation and structural characterization was therefore performed to define the correlation between interface morphology and the final chemical and mechanical properties of the enamel–steel interface. 相似文献
38.
39.
On the coexistence of power-controlled ultrawide-band systems with UMTS, GPS, DCS1800, and fixed wireless systems 总被引:1,自引:0,他引:1
Ultrawide bandwidth (UWB) wireless technology will play a key role in short-range wireless connectivity supporting very high bit rates availability, low power consumption, and location capabilities. UWB can be conveniently deployed in the design of wireless local and personal area networks, providing advanced integrated multimedia services to nomadic users within hot-spot areas. The very large bandwidth required by the UWB signals cannot be exclusively allocated; thus, UWB band overlaps with the bands allocated to many other narrow-band systems. Therefore, the assessment of the interference caused by UWB devices on already-existing systems is of primary importance to ensure coexistence and, therefore, to guarantee acceptance of UWB technology worldwide. We study the coexistence issues between an UWB-based system and universal mobile telecommunication systems, global positioning systems, DCS1800, and fixed wireless access systems and point-to-point (PP) links terminals. UWB interference is evaluated accounting for the UWB signal model, a realistic UWB master/slave system architecture with power-controlled terminals. Furthermore, we analyze the dependence of the UWB interference from the UWB signal parameters and demonstrate through computer simulation that, in all practical cases, a UWB system can coexist with the selected victim terminals without causing any dangerous interference. 相似文献
40.
Luisa Barbieri Cristina Leonelli Tiziano Manfredini Cristina Siligardi Anna Bonamartini Corradi Piercarlo Mustarelli Corrado Tomasi 《Journal of the American Ceramic Society》1997,80(12):3077-3083
An aluminosilicate glass of composition 61SiO2 6Al2 O3 10MgO6ZnO·12Li2 O·5TiO2 (mol%) has been prepared by a melting process and investigated as far as crystallization is concerned. Glass-ceramic is easily obtained because glass shows a high tendency to crystallize starting from 700°C. The crystalline phases evolve with temperature, showing the aluminosilicates to be the main phase up to 1050°C, followed by metasilicates and silicates, some of which have lower melting points. The titanates of Mg and Zn develop from the phase-separated glass, soon after T g , and grow to form nucleation centers for the other crystalline phases. The evolution from phase-separated glass to glass-ceramic has been followed by many thermal, diffractometric, spectroscopic, and microscopic techniques. 相似文献