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991.
X.Sun Z.J.Ding H.MLi K.Salma Z.M.Zhang W.S.Tan 《金属学报(英文版)》2005,18(3):325-330
A Monte Carlo model considering the electron spin direction and spin asymmetry has been developed. The energy distribution of the secondary electron polarization and the primary energy dependence of the polarization from Fe are studied. The simulation results show that: (1) the intensity of the spin-up secondary electrons is larger thanvthat of thevspin-down secondary electrons, suggesting the secondary electrons are spin polarized; (2) the spin polarization of secondary electrons with nearly zero kinetic energy is higher than the average valance spin polarization, Pb=27% for Fe. With increasing kinetic energy, the spin polarization of the secondary electrons decreases to the value of Pu remaining constant at higher kinetic energies; (3) the spin polarization increases with an increase in the primary energy and reaches a saturation value at higher primary energy in both the Monte Carlo simulation and experimental results. 相似文献
992.
H.T.Cao Z.L.Pei X.B.Zhang J.Gong C.Sun L.S.Wen 《金属学报(英文版)》2005,18(3):356-362
Al and Mn co-doped-ZnO films have been prepared at room temperature by DC reactive magnetron sputtering technique. The optical absorption coefficient, apparent and fundamental band gap, and work function of the films have been investigated using optical spectroscopy, band structure analyses and ultraviolet photoelectron spectroscopy (UPS). ZnO films have direct allowed transition band structure, which has been confirmed by the character of the optical absorption coefficient. The apparent band gap has been found directly proportional to N^2/3, showing that the effect of Burstein-Moss shift on the band gap variations dominates over the many-body effect. With only standard cleaning protocols, the work function of ZnO: (Al, Mn) and ZnO: Al films have been measured to be 4.26 and 4.21eV, respectively. The incorporation of Mn element into the matrix of ZnO, as a relatively deepd onor, can remove some electrons from the conduction band and deplete the density of occupied states at the Fermi energy, which causes a loss in measured photoemission intensity and an increase in the su,rface work function. Based on the band gap and work function results, the energy band diagram of the ZnO: (Al, Mn) film near its surface is also given. 相似文献
993.
H.S.San Z.G.Wu B.Li B.X.Feng 《金属学报(英文版)》2005,18(3):403-410
Transparent conducting oxides Cdln2O4 thin films were prepared by radio-frequency reactive sputtering from a Cd-ln aUoy target in Ar O2 atmosphere. By transmission spectrum and Hall measurement for different samples prepared at different substrate temperatures, it could be found that the carrier concentration would increase with the decrease of substrate temperature, but absorption edge showed an abrupt variation from a blue shift to a red shift. TheoreticaUy, the paper formulated the effect of high-density point defects on band structures; it embodied the formation of band tailing, Burstein-Moss shift and band-gap narrowing. The density of holes will influence the magnitude of optical band gap and transmittance of light. Since extrapolation method does not fit degenerate semiconductor materials, a more accurate method of obtaining optical band gap is curve fitting. In addition, ionized impurities scattering is the main damping mechanism of the free electrons in Cdln2O4 films, the density of ionized impurities induced by altering substrate temperature will affect the carriers mobility. 相似文献
994.
L.C. Wang F. Wang X.H. You Department of Material Science Engineering Taiyuan University of Science Technology Taiyuan China 《金属学报(英文版)》2005,18(5):669-673
1. Introduction In mass production foundry, because of short production period, much repeatly using times of molding sand, heat released by liquid metal during solidification in the sand mould will make the tem- perature of sand attain to 60-70°C[1], tha… 相似文献
995.
This paper presents a new method for surface reconstruction from dexel data for virtual sculpting. This is part of our research efforts to develop a dexel model based sculpting system with the capability of interactive solid modeling with haptics interface. Dexel data are converted to a series of planar contours in parallel slices (i.e. cross sections). Then triangular meshes are created by connecting the contour points in adjacent slices. Examples are given to demonstrate the ability of the described method to convert from dexel data to triangular meshes for the viewing of a sculpted model in different directions. 相似文献
996.
Ultrafast Tool Servos for Diamond Turning 总被引:4,自引:0,他引:4
X.-D. Lu 《CIRP Annals》2005,54(1):383-388
This paper presents the design, implementation and control of a new class of fast tool servos, based on a novel ultrafast motor concept. A prototype ultrafast tool servo with a stroke of 30 |im is described. Experimental results demonstrate that the ultrafast tool servo achieves 23 kHz closed-loop bandwidth, as low as 1.7 nm RMS error, 500 G peak acceleration at 10 kHz open-loop operation, and 2.1 nm (0.04%) error in tracking a 3 kHz sinusoid of 16 |im p-v. A 1 kW linear power amplifier and a 1 MHz sampling rate high-speed real-time computer are designed to drive and control this ultrafast tool servo. A digital controller including loop shaping and adaptive feedforward cancellation is designed to control the tool motion. 相似文献
997.
A new concept of full vacuum manufacturing for Cu-Ⅲ-Ⅳ2 thin-film solar cells has been discussed. Cu-Ⅲ-Ⅳ2 thin-film solar cells manufactured using full in-line reactive sputtering will result in lower cost than that of the conventional method with CdS layer fabricated with chemical bath deposition (CBS) method. Using reactive sputtering process with organometallic gases, the compositions and electronic properties of Cu-Ⅲ-Ⅳ2 thin-film can be fine-tuned and precisely controlled. n-type Cu-Ⅲ-Ⅳ2 film and ZnS suffer layer can also be deposited using the in-line sputtering instead of using the CdS layer. The environmental pollution problems arising from using CdS can be eliminated and the ultimate goal of full in-line process development can then be realized. Some preliminary experimental results on a modal solar cell fabricated by the new technique in the new concept have been presented. 相似文献
998.
Research on dynamic micro-deformation under laser point source 总被引:2,自引:0,他引:2
X.F. Wang G.N. Chen Sh.G. Hu J. Takacs Gy. Krallics Y.P. Su 《International Journal of Machine Tools and Manufacture》2005,45(12-13):1515-1522
The dynamic micro-deformation of the specimen under laser point source is measured using a laser beam reflex amplifier system and numerically simulated by Msc.Marc software. Compared with experimental result and calculated result, the final deformation direction of the specimen depends on the result of the thermal strain and the phase transformation strain cooperation, away from the laser beam or towards the laser beam, the final deformation angle depends on temperature gradient in the thickness direction and the geometry constraint of the specimen. The conclusion lays the foundation for further research on the mechanism of laser bending. At the same time, it is proposed that the model of calculation based on classical Fourier heat transfer theory cannot be enough to simulate the dynamic micro-deformation of the specimen under laser point source, the model of calculation should be modified in the future. 相似文献
999.
G. X. Zhao M. Zheng X. H. Lv X. H. Dong H. L. Li 《Metals and Materials International》2005,11(2):135-140
The corrosion behavior of 13Cr martensitic stainless steel in a CO2 environment in a stimulated oilfield was studied with potentiodynamic polarization and the impedance spectra technique. The
results showed that the microstructure of the surface scale clearly changed with temperature. This decreased the sensitivity
of pitting corrosion and increased the tendency toward general (or uniform) corrosion. The capacitance, the charge transfer
resistance, and the polarization resistance of the corrosion product scale decrease with increasing temperature from 90 to
120 °C, and thus the corrosion is a thermal activation controlled process. Charge transfer through the scale is difficult
and the corrosion is controlled by a diffusion process at a temperature of 150 °C. Resistance charge transfer through the
corrosion product layer is higher than that in the passive film. 相似文献
1000.
J.X. Zhou R.X. Liu L.L. Chen D.M. Liao H. S. Wei 《金属学报(英文版)》2005,18(6):724-730
Numerical simulation of casting's mold filling process is the main and the most important aspect of the foundry CAE technology. But it is time-consuming; it may take dozens of hours or several days. While with the development of computer hardware, numerical simulation of casting' s mold filling process has made rapid progress. The simulation results, therefore, have become more and more practical. This study tries to find some clues of the computational time of mold filling process. Firstly, this paper introduces mathematic model and the basic route of numerical simulation of casting's mold filling process. Then the computational time of mold filling process has been carefully studied, and some new and useful results have been gained from the study of the computational time. Finally, this paper has given some real applications of numerical simulation of casting's mold filling process. 相似文献