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21.
Social networking sites (SNS) have transformed how individuals interact, build and maintain social relationships. We proposed a research model on the determinants of user continuance using Bagozzi's framework of self-regulation as the theoretical foundation. Following the process of appraisal → emotional reactions → coping responses, we developed the model by leveraging findings from social presence and IS continuance research. Based on survey data from Facebook users, we found that appraisal factors (pleasure, awareness, connectedness, and system quality) were strong determinants of emotional reaction (user satisfaction and sense of belonging). User satisfaction and sense of belonging together positively influenced continuance intention. 相似文献
22.
We present dynamic studies of surface reactions using video-Field Ion Microscopy (FIM) along with Pulsed Field Desorption
Mass Spectrometry (PFDMS). Catalytic water formation is followed using rhodium and platinum 3D field emitter crystals for
the oxidation of hydrogen with either oxygen (Rh) or NO (Pt). Strongly non-linear dynamics are observed with nanoscale spacial
resolution. For both reactions quasi-oscillatory behaviour exists under certain conditions of temperatures and partial pressures.
An influence of the probing electric field is observed and possibly essential in establishing oscillatory behaviour. Local
chemical probing of selected surface areas with up to 400 atomic surface sites proves catalytic water formation to take place.
Since water ions (H2O+/H3O+) cause image formation of the O2–H2 reaction on Rh, respective videos provide space-time resolved information on the catalytically active sites. Atom-probe data
also reveal that the surface of the Rh sample reversibly switches from a metallic to an oxidized state during oscillations.
As to the NO–H2 reaction on Pt, fast ignition phenomena are observed to precede wave fronts. After catalytic water formation, NO molecules
diffuse into emptied areas and cause high image brightness. Depending on the size of the Pt crystal, the reaction may ignite
in planes or kinked ledges along the <100> zone lines. Thus FIM provides clear experimental evidence that kinks are more reactive
than steps in the catalytic NO + H2 reaction. Pt surface oxidation occurs and has probably been underestimated in previous FIM studies. 相似文献
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26.
Cameron Talischi Glaucio H. Paulino Chau H. Le 《Structural and Multidisciplinary Optimization》2009,37(6):569-583
Traditionally, standard Lagrangian-type finite elements, such as linear quads and triangles, have been the elements of choice
in the field of topology optimization. However, finite element meshes with these conventional elements exhibit the well-known
“checkerboard” pathology in the iterative solution of topology optimization problems. A feasible alternative to eliminate
such long-standing problem consists of using hexagonal (honeycomb) elements with Wachspress-type shape functions. The features
of the hexagonal mesh include two-node connections (i.e. two elements are either not connected or connected by two nodes),
and three edge-based symmetry lines per element. In contrast, quads can display one-node connections, which can lead to checkerboard;
and only have two edge-based symmetry lines. In addition, Wachspress rational shape functions satisfy the partition of unity
condition and lead to conforming finite element approximations. We explore the Wachspress-type hexagonal elements and present
their implementation using three approaches for topology optimization: element-based, continuous approximation of material
distribution, and minimum length-scale through projection functions. Examples are presented that demonstrate the advantages
of the proposed element in achieving checkerboard-free solutions and avoiding spurious fine-scale patterns from the design
optimization process. 相似文献
27.
Errors in measurement of the object illumination angle affect fringe interpretation accuracies in speckle interferometry. To measure the object illumination angle we propose a method based on the moiré effect. The technique is easy to implement and was found to yield fast and accurate measurements. 相似文献
28.
A white-light reconstruction setup for shearograms using optical-fiber waveguides is presented. The setup is compact, is not susceptible to dust and scratches, and enables the two-dimensional fringe pattern on shearograms to be viewed directly under uniform and enhanced illumination with minimal image distortion. 相似文献
29.
M. B. Maple M. C. de Andrade J. Herrmann Y. Dalichaouch D. A. Gajewski C. L. Seaman R. Chau R. Movshovich M. C. Aronson R. Osborn 《Journal of Low Temperature Physics》1995,99(3-4):223-249
Experimental efforts to characterize and develop an understanding of non Fermi liquid (NFL) behavior at low temperature in f-electron materials are reviewed for three f-electron systems: M1–xUxPd3 (M = Sc, Y), U1–xThxPd2Al3, and UCu5–xPdx. The emerging systematics of NFL behavior in f-electron systems, based on the present sample of nearly ten f-electron systems, is updated. Many of the f-electron systems exhibit the following temperature dependences of the electrical resistivity p, specific heat C, and magnetic susceptibility for T T0, where To is a characteristic temperature: P(T) 1 –aT/T
0, where a < 0 or > 0, C(T)/T (-1/T
o) In (T/bT
0), and (T) 1 –c(T/To)1/2. In several of the f-electron systems, the characteristic temperature To can be identified with the Kondo temperature Tk. 相似文献
30.
Bifurcation of crack pattern in arrays of two-dimensional cracks 总被引:1,自引:0,他引:1
Theoretical calculations based on simple arrays of two-dimensional cracks demonstrate that bifurcation of crack growth patterns may exist. The approximation used involves the dipole asymptotic or pseudo-traction method to estimate the local stress intensity factor. This leads to a crack interaction parametrized by the crack length/spacing ratio =a/h. For parallel and edge crack arrays under far field tension, uniform crack growth patterns (all cracks having same size) yield to nonuniform crack growth patterns (bifurcation) if is larger than a critical value cr. However, no such bifurcation is found for a collinear crack array under tension. For parallel and edge crack arrays, respectively, the value of cr decreases monotonically from (2/9)1/2 and (2/15.096)1/2 for arrays of 2 cracks, to (2/3)1/2/ and (2/5.032)1/2/ for infinite arrays of cracks. The critical parameter cr is calculated numerically for arrays of up to 100 cracks, whilst discrete Fourier transform is used to obtain cr for infinite crack arrays. For infinite parallel crack arrays under uniaxial compression, a simple shear-induced tensile crack model is formulated and compared to the modified Griffith theory. Based upon the model, cr can be evaluated numerically depending on (the frictional coefficient) and c
0/a (c
0 and a are the sizes of the shear crack and tensile crack, respectively). As an iterative method is used, no closed form solution is presented. However, the numerical calculations do indicate that cr decreases with the increase of both and c
0/a. 相似文献