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31.
We consider a general nonlinear input-output system governed by operator equations that relate the system's input, state, and output, all of which are in extended spaces. It is assumed that the system variables are separated. Our results give conditions under which the stability of the nominal system is robust; i.e., it is not destroyed by any sufficiently small admissible perturbation of the system. Theorem 1 deals with the case when by stability we mean theincremental stability. Theorem 3 concerns the*-stability; i.e., the case when the stability is essentially the boundedness of the transmission operator. Moreover, in Theorem 2 it is shown that, under certain conditions, the incremental stability of the nominal system implies insensitivity. Basically, our results show that if the operators describing the nominal system are well behaved, and the transition from the nominal system to the perturbed system is not abrupt, then the nominal system stability is robust. The applications of the results are illustrated by several examples. 相似文献
32.
Generalized solutions of semistate equations and stability 总被引:1,自引:0,他引:1
Vaclav Dolezal 《Circuits, Systems, and Signal Processing》1986,5(4):391-403
In this paper, solvability and stability of nonlinear, time-varying semistate equations is discussed. It is shown that generalized solutions exist in a vicinity of an equilibrium. Moreover, results on a Liapunov-like (uniform, asymptotic) stability are given. 相似文献
33.
Vaclav Dolezal 《Circuits, Systems, and Signal Processing》1987,6(3):335-345
In this paper various conditions guaranteeing the ordinary, uniform, and asymptoticA-stability of semistate equations are given. These results are based on and given in terms of the semi-explicit form of a semistate equation. 相似文献
34.
Yevgeniya Kalachyova Oleksiy Lyutakov Andrey Solovyev Petr Slepi?ka Vaclav ?vor?ík 《Nanoscale research letters》2013,8(1):547
Porphyrin/Au and Au/porphyrin/Au systems were prepared by vacuum evaporation and vacuum sputtering onto glass substrate. The surface morphology of as-prepared systems and those subjected to annealing at 160°C was studied by optical microscopy, atomic force microscopy, and scanning electron microscopy techniques. Absorption and luminescence spectra of as-prepared and annealed samples were measured. Annealing leads to disintegration of the initially continuous gold layer and formation of gold nanoclusters. An amplification of Soret band magnitude was observed on the Au/meso-tetraphenyl porphyrin (TPP) system in comparison with mere TPP. Additional enhancement of luminescence was observed after the sample annealing. In the case of sandwich Au/porphyrin/Au structure, suppression of one of the two porphyrins’ luminescence maxima and sufficient enhancement of the second one were observed. 相似文献
35.
Mariapompea Cutroneo Lorenzo Torrisi Letteria Silipigni Alena Michalcova Vladimir Havranek Anna Mackova Petr Malinsky Vasily Lavrentiev Pavol Noga Jozef Dobrovodsky Petr Slepicka Dominik Fajstavr Lucio And Vaclav Holy 《International journal of molecular sciences》2022,23(20)
In the present study, graphene oxide foils 10 μm thick have been irradiated in vacuum using same charge state (one charge state) ions, such as protons, helium and oxygen ions, at the same energies (3 MeV) and fluences (from 5 × 1011 ion/cm2 to 5 × 1014 ion/cm2). The structural changes generated by the ion energy deposition and investigated by X-ray diffraction have suggested the generation of new phases, as reduced GO, GO quantum dots and graphitic nanofibers, carbon nanotubes, amorphous carbon and stacked-cup carbon nanofibers. Further analyses, based on Rutherford Backscattering Spectrometry and Elastic Recoil Detection Analysis, have indicated a reduction of GO connected to the atomic number of implanted ions. The morphological changes in the ion irradiated GO foils have been monitored by Transmission Electron, Atomic Force and Scanning Electron microscopies. The present study aims to better structurally, compositionally and morphologically characterize the GO foils irradiated by different ions at the same conditions and at very low ion fluencies to validate the use of GO for radiation detection and propose it as a promising dosimeter. It has been observed that GO quantum dots are produced on the GO foil when it is irradiated by proton, helium and oxygen ions and their number increases with the atomic number of beam gaseous ion. 相似文献
36.
Effect of magnesium aluminum silicate glass on the thermal shock resistance of BN matrix composite ceramics 下载免费PDF全文
Delong Cai Dechang Jia Zhihua Yang Qishuai Zhu Vaclav Ocelik Ilia D. Vainchtein Jeff Th.M. De Hosson Yu Zhou 《Journal of the American Ceramic Society》2017,100(6):2669-2678
The effects of magnesium aluminum silicate (MAS) glass on the thermal shock resistance and the oxidation behavior of h‐BN matrix composites were systematically investigated at temperature differences from 600°C up to 1400°C. The retained strength rate of the composites rose with the increasing content of MAS showing a maximum value at the 60 wt% MAS. Compared with the original strength, the retained strength of the specimen after thermal shock increased to 77% (ΔT=1000°C). The strengthening effect of MAS and the surface microstructural evolution of composites are responsible for the improved thermal shock resistance. Surface oxidation of the composites during the thermal shock process plays a positive role in enhancing the retained strength by self‐healing cracks and the appearance of the compressive stress. The oxide layer also acted as a thermal barrier to decelerate the actual thermal stress. Furthermore, this dense layer also improved the oxidation resistance of h‐BN matrix composites by prevent diffusion of oxygen. These results indicated that short‐term surface oxidation during thermal shock process is favorable to the enhancement of the thermal shock resistance of BN‐MAS composite ceramics. 相似文献
37.
This work proposes a method to reconstruct surfaces with higher-order smoothness from noisy 3D measurements. The reconstructed
surface is implicitly represented by the zero-level set of a continuous valued embedding function. The key idea is to find
a function whose higher-order derivatives are regularized and whose gradient is best aligned with a vector field defined by
the input point set. In contrast to methods based on the first-order variation of the function that are biased toward the
constant functions and treat the extraction of the isosurface without aliasing artifacts as an afterthought, we impose a higher-order
smoothness directly on the embedding function. After solving a convex optimization problem with a multiscale iterative scheme,
a triangulated surface can be extracted using the marching cubes algorithm. We demonstrated the proposed method on several
data sets obtained from raw laser-scanners and multiview stereo approaches. Experimental results confirm that our approach
allows us to reconstruct smooth surfaces from points in the presence of noise, outliers, large missing parts, and very coarse
orientation information. 相似文献
38.
Continuous global optimization in surface reconstruction from an oriented point cloud 总被引:1,自引:0,他引:1
We introduce a continuous global optimization method to the field of surface reconstruction from discrete noisy cloud of points with weak information on orientation. The proposed method uses an energy functional combining flux-based data-fit measures and a regularization term. A continuous convex relaxation scheme assures the global minima of the geometric surface functional. The reconstructed surface is implicitly represented by the binary segmentation of vertices of a 3D uniform grid and a triangulated surface can be obtained by extracting an appropriate isosurface. Unlike the discrete graph-cut solution, the continuous global optimization entails advantages like memory requirements, reduction of metrication errors for geometric quantities, and allowing globally optimal surface reconstruction at higher grid resolutions. We demonstrate the performance of the proposed method on several oriented point clouds captured by laser scanners. Experimental results confirm that our approach is robust to noise, large holes and non-uniform sampling density under the condition of very coarse orientation information. 相似文献
39.
40.
Preparation of bulk‐nanostructured UO2 pellets using high‐pressure spark plasma sintering for LWR fuel safety assessment 下载免费PDF全文
Vaclav Tyrpekl Marco Cologna Jean‐Francois Vigier Andrea Cambriani Wim De Weerd Joseph Somers 《Journal of the American Ceramic Society》2017,100(4):1269-1274
Nuclear fuel undergoes a significant restructuration during its lifetime in the nuclear reactor. Especially at the rim of the pellet, large UO2 grains disintegrate into a nanosized material. In this paper, we focus on the preparation of bulk UO2 with grain sizes below 100 nm to investigate the physico‐chemical properties of this so‐called “high burn up structure” (HBS). Preparation of bulk nanocrystalline materials is a challenge that can be overcome using the high‐pressure spark plasma sintering (HP SPS) technique. In‐house developed HP SPS with 500 MPa applied pressure was used for compaction of 11 nm UO2 powder obtained by oxalate conversion. The procedure yielded dense (>90%) compacts with grain size as low as 34 nm for samples sintered at 800°C. 相似文献