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991.
Yoshitsugu Kimura Shinya Kawakami Hiroshi Kanayama Satoshi Asahi Shinichi Mizuguchi 《Tribology International》1994,27(4)
Frictional properties of typical tribomaterials are evaluated under sparse lubrication conditions where lubricating oil is supplied but its amount is far from sufficient even for boundary lubrication. These conditions are provided by employing a mist oiling system which can continuously supply oil at constant, extremely low and quantitatively controlled rates. First, basic data on the properties of the oil mist are given and a quantitative determination of oil supply onto a sliding surface is described. Then frictional properties evaluated under stepwise increasing loads are presented for iron/steel, surface modification, ceramics and self-lubricating materials, and their characteristic behaviour is discussed. 相似文献
992.
A simple and robust friction model is proposed for cold metal rolling in the mixed lubrication regime, based on physical phenomena across two length scales. At the primary roughness scale, the evolution of asperity contact area is associated with the asperity flattening process and hydrodynamic entrainment between the roll and strip surfaces. The friction coefficient on the asperity contacts is related to a theoretical oil film thickness and secondary-scale roll surface roughness. The boundary friction coefficient at the “true” asperity contacts is associated with tribo-chemical reactions between fresh metal, metal oxide, boundary additives, the tool and any transfer layer on the tool. The asperity friction model is verified by strip drawing simulations under thin film lubrication conditions with a polished tool, taking the fitting parameter of the boundary lubrication friction factor on the true contact areas equal to 0.1. Predicted values of average friction coefficient, using a boundary friction factor in the range 0.07–0.1, are in good agreement with measurements from laboratory and industrial rolling mill trials. 相似文献
993.
The possibilities of using advanced ceramics in water-lubricated journal bearings were studied by performing tests on journal bearings lubricated with water. The materials studied were two aluminas (Al2O3), a zirconia-toughened alumina (ZTA), a partially stabilized zirconia (PSZ), a sintered silicon carbide (SiC), a reaction-bonded silicon carbide (SiSiC) and a β′-sialon. From the present study it can be concluded that water-lubricated journal bearings utilizing silicon carbide against itself offer good performance. Moderate performance can be achieved with an all-alumina sliding pair, provided that the loads remain low and that a high surface quality can be ensured. 相似文献
994.
Strip drawing is used to investigate the friction behaviour under thin film lubrication in metal forming with plastic deformation. Friction coefficients are measured under a wide range of tribological conditions. The surface roughness is measured on an interferometric profilometer. The results show that the friction coefficient decreases with increasing oil film thickness hw, as estimated using a formula appropriate for smooth tool and workpiece. Measurements of the surface topography show that change in friction is associated with a change in contact ratio between the tool and strip. The effect of strip reduction, strip roughness and die roughness on the friction coefficient is also investigated. 相似文献
995.
水溶性3-(N,N-二正丁基二硫代氨基甲酸基)酸衍生物的摩擦学性能 总被引:2,自引:0,他引:2
通过摩擦学实验和表面分析研究了两种酸衍生物,3-(N,N-二正丁基二硫代氨基甲酸基)丙酸及3-(N,N-二正丁基二硫代氨基甲酸基)丙二酸的摩擦学性能及作用机理。实验表明:两种酸衍生物均具有优良的承载能力和抗磨性能.并能显著提高水基液的烧结负荷.且3-(N,N-二丁基二硫代氨基甲酸基)丙二酸的摩擦学性能优于3-(N,N-二正丁基二硫代氨基甲酸基)丙酸,其抗磨作用机理是在摩擦表面形成了吸附膜和化学反应膜,两类膜的共同作用有效地阻止了摩擦失效的发生。 相似文献
996.
It has been found that CF3CH2F (HFC-134a) gas is an effective lubricant for several ceramics because of the formation of fluorine-containing tribochemical products. To understand the influence of the molecular structure of fluorine-containing gases on the lubricating characteristics, the lubricating effects and tribochemical reactions of some fluorinated methanes for Al2O3 ceramic were studied. X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectroscopy (TOF-SIMS) were used to identify the chemical structure of tribochemical products. It was found that the friction and wear of Al2O3 ceramic were dependent on the molecular structure of the reacting fluorocarbon gases. The lowest friction was obtained in CH2F2. CHF3 showed the best anti-wear effect. The results of surface analyses indicate that greater amounts of tribochemical products are produced when Al2O3 rubs in CH2F2 than in CF4 and CHF3 gases. C–C/C–H/carbon and AlF3, which are mainly formed on the sliding surface in CH2F2, are responsible for the low friction. The mechanism of tribochemical reactions of the different environmental molecules on the nascent surface of Al2O3 was also discussed. 相似文献
997.
A fast multigrid approach is presented for the analysis of thermal elastohydrodynamic lubrication (EHL) under rolling/sliding circular contacts at high loads and high slip ratios with low computing time on a personal computer. This fast solver combines directiteration, multigrid, Newton-Raphson, Gauss-Seidel iteration, and multilevel multi-integration methods into one working environment that can reduce the computational complexity from O(n3 to O(nlnn) for the thermal EHL problem under rolling/sliding circular contacts. Since the couped Reynolds and energy equations are simultaneously solved by the Newton-Raphson scheme, the iteration for the convergence solution is less than those of the classical approach. Results show that thermal effects on the pressure profile and film thickness are significant for a wide range of loads, speeds and slip ratios. The maximum midfilm and surface temperature rise in the Hertzian contact region increases with increasing slip ratio, dimensionless speed, and load. The minimum film thickness decreases with increasing load and slip ratio, and decreasing dimensionless speed. 相似文献
998.
There has been debate for many years as to whether long-chain surfactant friction modifier additives reduce friction by forming adsorbed films of monolayer thickness or whether they form films equivalent to several or many multilayers thick. In the work described in this paper, a series of metal oleate friction modifier additives has been synthesized and their film-forming properties compared in rolling-contact conditions by means of ultrathin film interferometry. It has been found that some of these additives form thick boundary films while others do not. It is concluded that thick boundary-film formation results from the formation of insoluble iron(II) oleate on the rubbing surfaces and that, for metal oleates, this occurs only for metals lower than iron in the electrochemical series and is due to a redox reaction involving iron from the steel surface and the metal oleate. 相似文献
999.
1000.