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991.
992.
埋地管道腐蚀机理及应对措施 总被引:3,自引:0,他引:3
介绍了埋地管道的腐蚀机理,分析了影响腐蚀的因素,从内、外防腐蚀、阴极保护等方面论述了防腐蚀的应对措施,并指出了防腐蚀层、阴极保护并重的防腐蚀措施的重要性。 相似文献
993.
Abstract. One method of describing the properties of a fitted autoregressive model of order p is to show the p roots that are implied by the lag operator. Considering autoregressive models fitted to 215 US macro series, with lags chosen by either the Bayesian or Schwarz information criteria or Akaike information criteria, the roots are found to constitute a distinctive pattern. Later analysis suggests that much of this pattern occurs because of overfitting of the models. An extension of the results shows that they have some practical multivariate time‐series modelling implications. 相似文献
994.
Density functional theory (DFT) is applied to study the structure and electronic properties of oligomers based on bithiophene bridged by a sp2 carbon substituted by a chalcogen atom (O, S, Se and Te), and their polybifurane and polybipyrrole analogues. The important reduction of the energy gap which is observed for the whole series of biheterocyclic compounds, when going down the chalcogen group, is explained on the basis of an orbital interaction analysis. Bithiophene polymers bridged by a selenium or a tellurium substituted carbon atom are expected to exhibit very low energy band gaps. 相似文献
995.
The EPR magnetic susceptibility behavior of the camphorsulfonic acid doped polyaniline (PANCSA) blends with polyethylene oxide (PEO) is reported in fibers and films. In particular, EPR investigations on electrospun (PANCSA)0.72(PEO)0.28 nanofibers, cast films of (PANCSA)0.72(PEO)0.28 and cast films of (PANCSA) were performed to investigate differences in the mesoscopic disorder as induced by the process of electrospinning. The changes observed in the Pauli susceptibility, EPR lineshape, EPR linewidth, and dc conductivity are interpreted as due to increased chain alignment in the fibers compared with the cast films. 相似文献
996.
Switching and memory devices based on a polythiophene derivative for data-storage applications 总被引:1,自引:0,他引:1
In this article, we report electrical characteristics of devices based on oriented and unoriented films of a polymer, namely poly[3-(6-methoxyhexyl)thiophene]. The current–voltage characteristics of sandwiched devices, based on unoriented polymer, showed hysteresis behavior, while oriented versions exhibited switching characteristics, i.e. presence of two conducting states depending on sweep direction of voltage scans. The ratio between the device current of two conducting states has been as high as 105. This is comparable, if not better, than the results reported so far with complicated device architecture or doped polymeric materials. We have also demonstrated that the switching devices have an associated memory effect for data-storage applications. 相似文献
997.
Organic light emitting devices performance improvement by inserting thin parylene layer 总被引:1,自引:0,他引:1
Lin Ke Ramadas Senthil Kumar Keran Zhang Soo Jin Chua A. T. S. Wee 《Synthetic Metals》2004,140(2-3):295-299
An organic light emitting device (OLED) structure with a thin parylene layer deposited by low-temperature chemical vapour deposition (CVD) at the anode–organic interface was fabricated. Such a structure gives off higher efficiency, a smaller number and smaller size dark non-emissive areas, slower growth rate of the dark areas and a longer device lifetime compared to one without the parylene layer. The parylene modified indium tin oxide (ITO) surface shows an increased work-function and a reduced surface roughness compared to that of the bare ITO surface. The interface optimisation contributes to the device performance improvement. 相似文献
998.
Mu-Tian Yan Pin-Hsum Huang 《International Journal of Machine Tools and Manufacture》2004,44(7-8):807-814
In this paper, a closed-loop wire tension control system for a wire-EDM machine is presented to improve the machining accuracy. Dynamic models of the wire feed control apparatus and wire tension control apparatus are derived to analyze and design the control system. PI controller and one-step-ahead adaptive controller are employed to investigate the dynamic performance of the closed-loop wire tension control system. In order to reduce the vibration of wire tension during wire feeding, dynamic absorbers are added to the idle rollers of wire transportation mechanism. Experimental results not only demonstrate that the developed control system with dynamic absorbers can obtain fast transient response and small steady-state error than an open-loop control system, they also indicate that the geometrical contour error of corner cutting is reduced with approximately 50% and the vertical straightness of a workpiece can be improved significantly. 相似文献
999.
A. V. Morozkin 《Journal of Alloys and Compounds》2004,370(1-2):L1-L3
Phase equilibria in the Ce–Ti–Ge system were investigated by X-ray powder diffraction, electron probe X-ray analysis and the isothermal section at 1170 K was obtained. We confirmed the CeFeSi-type CeTiGe compound (a=0.4135 (1) nm, c=0.7921 (1) nm, space group P4/nmm, No. 129). A new compound, Ce20Ti20Ge60, was found (a=0.3967(6) nm, c=6.054 (2) nm, space group P4). It is obvious that the ThSi2-type Ce33Ti7Ge54 compound (a=0.4217 (1) nm, c=1.4184 (3) nm, space group I41/amd, No. 141) belongs to the extended solid solution region of the ThSi2-type CeGe2 compound. 相似文献
1000.
I.I Bulyk V.V Panasyuk A.M Trostianchyn G.M Grygorenko Yu.M Pomarin T.G Taranova V.A Kostin Yu.G Putilov 《Journal of Alloys and Compounds》2004,370(1-2):261-270
Features of the conventional hydrogenation, disproportionation, desorption, recombination (HDDR) and solid-HDDR processes in some R–Fe–B (R is a mixture of Nd, Pr, Ce, La, Dy) ferromagnetic alloys were studied in the temperature range 20–990 °C and pressure range from 1×10−3 Pa to 0.1 MPa. This was carried out by means of differential thermal analysis (DTA), X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) methods. The hydride of the initial phase is formed by heating to 115 °C. The disproportionation of the alloys occurs in the temperature range from 320 to 800 °C. Φ-phase constitutes the base of the initial alloys. Among the disproportionation products, R-hydride, -Fe and two borides (Fe2B and R1.1Fe4B4) were revealed. The initial phase in all the alloys is recovered after heating in vacuum to a temperature of 990 °C. Full hydrogen desorption occurs in two temperature ranges with the peaks at 200–320 and 630–715 °C. 相似文献