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991.
The influence of the chemical reactions occurring in the gas phase of a gas suspension flowing in a channel with penetrable
walls and the combustion of the condensed-impurity particles in this flow on its gasdynamic structure has been investigated.
It is shown that the order of the system of equations defining a flow of a chemically reactive gas suspension with a homogeneous
exothermic reaction proceeding at a definite rate and a heterogeneous combustion of the condensed-phase particles can be decreased
if certain assumptions are mode. The distributions of the parameters of the gas and dispersed phases were calculated as functions
of the rate of blow and the sizes of the particles.
__________
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 91–98, July–August, 2007. 相似文献
992.
M. V. Filipskii S. T. Surzhikov 《Journal of Engineering Physics and Thermophysics》2007,80(2):284-291
A method and results of numerical modeling of radiative heating of the back surface of the MSRO (Mars Sample Return Orbiter)
space vehicle of the European Space Agency are presented. To determine radiation heat fluxes, the method of discrete ordinates
on unstructured tetrahedral grids is used. The radiative model is based on the radiation-transfer equation in a multigroup
approximation. Numerical calculation has been performed for the most thermally stressed point of the assumed trajectory of
the entry of an MSRO-type space vehicle into the Mars atmosphere. A comparison with the discrete ordinates method on structured
grids is made. Good agreement between the results of calculations on structured and unstructured grids is demonstrated. The
level of radiation heat fluxes to the back surface of the MSRO space vehicle is predicted.
__________
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 71–78, March–April, 2007. 相似文献
993.
Analytical expressions for the shape of a charged drop of an incompressible liquid nonlinearly oscillating upon multimode
initial deformation have been obtained for the first time to within the third order of smallness. The second-order corrections
to oscillation frequencies are calculated depending on the spectrum of modes determining the initial deformation. The third-order
calculations show that the fundamental mode amplitude may increase due to the energy exchange with higher modes in a large
number of possible four-mode resonance interactions. 相似文献
994.
We report an unexpectedly rich variety of new flow patterns on a granular heap that is centrifuged so as to simulate a reduction
in gravity. These surface patterns exhibit coexisting static and flowing regions that depend strongly on centrifugal stress,
but surprisingly not on mass flow rate. A discrete cellular automata model reproduces some of the patterning features and
indicates that subsurface jamming may precipitate the formation of localized frozen patterns on the surface. This model provides
insights into the mechanics of granular flows under controlled stress environment and jammed-to-flowing transitions in granular
media. 相似文献
995.
We present the design and realization of cylindrical dielectric resonators operating in the 40–60 GHz frequency range, designed
for the measurement of the surface resistance and of the surface reactance shift in High-T
c Superconductors (HTS) thin films in a dc magnetic field. The resonators are single tone, based on the TE
011 mode, and multiple tone, the latter allowing in principle to exploit the simultaneous determination of the surface impedance
at different frequencies. As an application example, we report the temperature and field dependencies of the effective surface
impedance of some cuprate superconductors thin films. The results are compared with those obtained through the use of a standard
metal cavity with a similar Q-factor and operating in the same frequency range. The comparison highlights a superior stability and a higher sensitivity,
resulting in an increase of about two orders of magnitude in the resolution of the surface impedance measurement. By contrast,
the dissipative part of the superconducting transition (above T/T
c = 0.97) is better studied with the metal cavity. We also present measurements in the vortex state in YBaCa2Cu3O7−δ and Tl2Ba2CaCu2O8+x
that show significantly different physics.
PACS: 74.25 Nf. 相似文献
996.
This paper presents a new concept for symmetric boundary element method (SBEM) applicable to 2-D steady-state and transit potential problems. Two kinds of SBEM formulations are derived. Symmetry is obtained simply through matrix manipulation, and no hypersingularity appears. Therefore, SBEM is much easier than the traditional symmetric Galerkin BEM. Compared with the traditional asymmetric BEM, the present SBEM can reduce the computational cost for time domain problems only. However, when applied to BEM/FEM coupling procedure, SBEM can reduce the computational cost for both steady-state and time domain problems. Three numerical examples are included to illustrate the effectiveness and accuracy of the present formulations. 相似文献
997.
Sang C. Park 《The Visual computer》2003,19(1):38-49
A sweeping operation called polygonal extrusion is defined to improve the modeling power of CSG-based modeling. It is assumed that a 2D cross-sectional polygon (sweeping
polygon) moves in space while its containing plane is kept orthogonal to the tangent direction of the trajectory curve, a planar
polygonal chain having no self-intersections. The objective of the paper is to compute the boundary of the swept volume of
the sweeping polygon as a set of polygons (or triangles). The most significant challenge to accomplishing this objective is
the problem of trimming the swept volume. To solve the trimming problem, 2D-curve offsetting methods are employed. Two algorithms
are presented for polygonal extrusion that are based on different offsetting methods, the Voronoi diagram and PWID offset.
The proposed algorithms have been implemented and tested with various examples.
Published online: 28 January 2003 相似文献
998.
J. R. Díaz-Estrada E. Camps L. Escobar-Alarcón J. A. Ascencio 《Journal of Materials Science》2007,42(4):1360-1368
Deposition of Ti was carried out by laser ablation onto hydroxyapatite porous discs in an Ar atmosphere. Ti nanoparticles
were deposited onto HAp surface in order to modify its roughness and morphology as it is observed by scanning electron microscopy
(SEM) and scanning probe microscopy (SPM). A homogeneous distribution of Ti over the disc surface was corroborated by elemental
mapping. A comparison of the hydroxyapatite hardness before and after deposition was performed using SPM nanoindentation.
Transmission Electron Microscopy (TEM) showed that the Ti nanoparticles obtained were covered by an oxygen shell. It is shown
that surface modifications of the covered HAp by Ti result in better mechanical properties, reducing the possible damage to
the HAp ceramic by friction or impacts as it often happens in meniscus, bone junctions and the inclusion of prosthesis for
human treatments. 相似文献
999.
A physical criterion is proposed for a change in the equilibrium shape of elastically strained germanium nanoclusters growing on a silicon substrate under the conditions of molecular beam expitaxy. The critical size of pyramidal Ge clusters is estimated and compared to the available experimental data. 相似文献
1000.
Xiao-Ying Wang Jonathan M. Garibaldi Benjamin Bird Michael W. George 《Applied Intelligence》2007,27(3):237-248
Recently Fourier Transform Infrared (FTIR) spectroscopic imaging has been used as a tool to detect the changes in cellular
composition that may reflect the onset of a disease. This approach has been investigated as a mean of monitoring the change
of the biochemical composition of cells and providing a diagnostic tool for various human cancers and other diseases. The
discrimination between different types of tissue based upon spectroscopic data is often achieved using various multivariate
clustering techniques. However, the number of clusters is a common unknown feature for the clustering methods, such as hierarchical
cluster analysis, k-means and fuzzy c-means. In this study, we apply a FCM based clustering algorithm to obtain the best number
of clusters as given by the minimum validity index value. This often results in an excessive number of clusters being created
due to the complexity of this biochemical system. A novel method to automatically merge clusters was developed to try to address
this problem. Three lymph node tissue sections were examined to evaluate our new method. These results showed that this approach
can merge the clusters which have similar biochemistry. Consequently, the overall algorithm automatically identifies clusters
that accurately match the main tissue types that are independently determined by the clinician. 相似文献