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951.
Laboratory studies have been performed on simultaneous dephosphorization and desulfurization of Si-free Fe-4.5 % C melts with [P]o = 0.11 wt.% and [S]o = 0.04 wt.% in MF induction furnaces at 1 350°C. In these investigations, CaO- or Na2CO3-based fluxes were used and the techniques of powder injection or single top slag addition were applied. The following results have been obtained:
- – The effectiveness of lime and soda-based fluxes with regard to dephosphorization is practically the same. But a lower sulfur level is attained when Na2CO3-based fluxes are used.
- – In the injection experiments, efficiencies of ηP = 80% for dephosphorization and ηs = 90% for desulfurization are easily reached at a powder consumption of 50 to 60 g/kg. But a further increase of the η values requires a remarkable increase in the amount of injected powder. Top slag addition instead of powder injection is less effective, in general.
- – Apparent rate constants k[P] and k[S] from 0.05 to 0.3 min?1 have been determined in the initial stage of injection depending on the relative amount of injected flux. In the top slag experiments, the k[P] and k[S] values were practically constant at a level of 0.1 min?1.
952.
A miniature electrostatic element has been designed to selectively apply a 90 degrees phase shift to the unscattered beam in the back focal plane of the objective lens, in order to realize Zernike-type, in-focus phase contrast in an electron microscope. The design involves a cylindrically shaped, biased-voltage electrode, which is surrounded by a concentric grounded electrode. Electrostatic calculations have been used to determine that the fringing fields in the region of the scattered electron beams will cause a negligible phase shift as long as the ratio of electrode length to the transverse feature size is greater than 5:1. Unlike the planar, three-electrode einzel lens originally proposed by Boersch for the same purpose, this new design does not require insulating layers to separate the biased and grounded electrodes, and it can thus be produced by a very simple microfabrication process. Scanning electron microscope images confirm that mechanically robust devices with feature sizes of approximately 1 microm can be easily fabricated. Preliminary experimental images demonstrate that these devices do apply a 90 degrees phase shift between the scattered and unscattered electrons, as expected. 相似文献
953.
954.
When biological materials are infiltrated by a water-soluble melamine resin and hardened, they become as hard as glass. This is a prerequisite for extreme thin-sectioning. In this paper, the structural information from unsupported transparent thin sections of beef liver catalase, calf thymus DNA, horse spleen ferritin, insect muscle and rat microtubules is compared to that of normal thin sections. While ferritin molecules (12 nm diameter), microtubule subunits (8 nm long axis) and catalase crystals (8 nm subunit diameter) appear to become mechanically damaged in a 10 nm section (as measured by resectioning), DNA-molecules (3 nm diameter) are satisfactorily preserved during sectioning. Remarkably, for electron phase contrast imaging of unstained cross-sectioned insect muscle, a minimum section thickness of about 30–40 nm is required. 相似文献
955.
Igor V. Andrianov Vladimir I. Bolshakov Vladyslav V. Danishevskyy Dieter Weichert 《International Journal of Mechanical Sciences》2007,49(12):1344-1354
An asymptotic approach for simulation of the imperfect interfacial bonding in composite materials is proposed. We introduce between the matrix and inclusions a flexible bond layer of a volume fraction c(3) and of a non-dimensional rigidity λ(3), derive a solution for such three-component structure, and then set c(3)→0, λ(3)→0. In the asymptotic limit depending on the ratio λ(3)/c(3) different degrees of the interface's response can be simulated. A problem of the axial shear of elastic fibre-reinforced composites with square and hexagonal arrays of cylindrical inclusions is considered. The performed analysis is based on the asymptotic homogenization method, the cell problem is solved using the underlying principles of the boundary shape perturbation technique. As a result, we obtain approximate analytical solutions for the effective shear modulus and for the stress field on micro level depending on the degree of the interfacial debonding. Developed solutions are valid for all values of the components’ volume fractions and properties. In particular, they work well in cases of rapid oscillations of local stresses (e.g., in the case of densely packed perfectly rigid inclusions), while many of other commonly used methods may face computational difficulties. 相似文献
956.
Integrated optical 4×4 star coupler on LiNbO3 总被引:1,自引:0,他引:1
A novel low-loss passive planar 4×4 star coupler consisting of four interconnected 3 dB couplers was fabricated on x-cut Ti: LiNbO3 using z-propagation. Almost even distribution was achieved for both TE and TM polarised light incident on any of the four inputs. Excess loss including fibre coupling was <4.2 dB. 相似文献
957.
The in-plane Young’s modulus and the shear modulus of carbon nanocrystallites were investigated during in-situ tension tests of single carbon fibers by X-ray diffraction using the shift of the 10 band in the meridional direction and the change in the azimuthal width of the 002 reflection. The limiting value for the Young’s modulus was found to be 1140 GPa, which is higher than the value for graphite obtained from macroscopic specimens, but coincides with recent measurements on nanotubes. Furthermore, the shear modulus was evaluated using a uniform stress approach and was found to increase with increasing misorientation of the crystallites. It turns out that both the in-plane Young’s modulus and the shear modulus are not constant, but dependent on the orientation parameter. 相似文献
958.
Gaul A.J. Handschin E. Hoffmann W. Lehmkoster C. 《Power Systems, IEEE Transactions on》1998,13(1):86-93
Electrical energy has to be generated at the time it is needed. This is in contrast to economic efficiency in power generation since the best operating point for a power plant is constant power generation at its best economical rating. The presented approach shows a way to schedule loads so that some energy is storaged when it is available at lower generation costs. An evolutionary algorithm is evaluated which computes the optimal operation times of the above-mentioned loads. Since the evolutionary strategies (ES) themselves do not consider special cases, a knowledge base is integrated into the algorithm. The resulting approach allows a more efficient application of telecontrol systems for power system load management 相似文献
959.
The pH of tobacco smoke 总被引:7,自引:0,他引:7
960.