全文获取类型
| 收费全文 | 649篇 |
| 免费 | 72篇 |
| 国内免费 | 57篇 |
专业分类
| 电工技术 | 10篇 |
| 综合类 | 125篇 |
| 化学工业 | 67篇 |
| 金属工艺 | 43篇 |
| 机械仪表 | 105篇 |
| 建筑科学 | 17篇 |
| 矿业工程 | 4篇 |
| 能源动力 | 116篇 |
| 轻工业 | 4篇 |
| 水利工程 | 2篇 |
| 石油天然气 | 1篇 |
| 无线电 | 24篇 |
| 一般工业技术 | 131篇 |
| 冶金工业 | 14篇 |
| 原子能技术 | 6篇 |
| 自动化技术 | 109篇 |
出版年
| 2025年 | 1篇 |
| 2024年 | 6篇 |
| 2023年 | 18篇 |
| 2022年 | 4篇 |
| 2021年 | 10篇 |
| 2020年 | 24篇 |
| 2019年 | 24篇 |
| 2018年 | 11篇 |
| 2017年 | 33篇 |
| 2016年 | 33篇 |
| 2015年 | 45篇 |
| 2014年 | 33篇 |
| 2013年 | 44篇 |
| 2012年 | 37篇 |
| 2011年 | 43篇 |
| 2010年 | 51篇 |
| 2009年 | 63篇 |
| 2008年 | 28篇 |
| 2007年 | 66篇 |
| 2006年 | 52篇 |
| 2005年 | 22篇 |
| 2004年 | 11篇 |
| 2003年 | 16篇 |
| 2002年 | 16篇 |
| 2001年 | 11篇 |
| 2000年 | 5篇 |
| 1999年 | 9篇 |
| 1998年 | 10篇 |
| 1997年 | 4篇 |
| 1996年 | 1篇 |
| 1995年 | 4篇 |
| 1994年 | 1篇 |
| 1993年 | 1篇 |
| 1992年 | 1篇 |
| 1991年 | 3篇 |
| 1990年 | 3篇 |
| 1987年 | 7篇 |
| 1986年 | 8篇 |
| 1985年 | 3篇 |
| 1984年 | 3篇 |
| 1983年 | 1篇 |
| 1982年 | 2篇 |
| 1979年 | 3篇 |
| 1975年 | 1篇 |
| 1973年 | 1篇 |
| 1970年 | 1篇 |
| 1967年 | 1篇 |
| 1960年 | 1篇 |
| 1959年 | 1篇 |
| 1954年 | 1篇 |
排序方式： 共有778条查询结果，搜索用时 15 毫秒
1.
The aerodynamic and aeroacoustic performances of outdoor unit with two different types of grille have been investigated in present study. Experimental results indicate that the grille sharp will affect the flow rate and increase broadband noise level of outdoor unit. Based on noise generation mechanism and CFD simulation, vortex shedding noise model and inlet turbulence noise model are adopted to predict the broadband noise level of outdoor unit. When vortex shedding noise is concerned, the wake parameters should be calculated at 3 mm downstream of grille to achieve good accuracy. Inlet turbulence noise is generated from the interaction between blade wake and the grille, and plays less important role in present outdoor unit configuration. In comparison with experimental results, it is shown that the broadband noise prediction method could provide reasonable accuracy and the error between prediction and experiment is less than 1 dBA. 相似文献
2.
运用莱卡显微镜、X射线衍射仪及电化学测试系统等仪器设备,对(Sn-9Zn)-xBi(x=0,1,3和5)钎料组织性能进行研究.结果表明:当x小于5时,Bi可明显影响(Sn-9Zn)-xBi钎料中富Zn相尺寸及分布,钎料的熔化温度随Bi含量的增加而降低至188℃;钎料的润湿性随Bi含量增加而得到改善,其中以x在1～3为最... 相似文献
3.
An ultra-fast removal process of a silicon sacrificial layer for the selective release of a metal structure on a Si substrate was studied, which uses a chemical dry etching method. The chemical dry etching of a Si layer was performed in an NF3 remote plasma with the direct injection of additive nitric oxide (NO) gas. When the NO gas was injected into the chamber into which F radicals were supplied from a remote plasma source using NF3 input gas, the silicon layer was removed selectively and the metal structure could be released easily. It was found that the etch rate on the sidewall (up to ≅ 18.7 μm/min for an opening width of 100 μm) and the bottom (up to ≅ 24.5 μm/min for an opening width of 100 μm) depends on the NO/(NO + Ar) gas flow ratio, time duration, and opening width. The developed dry etching process could be used to release a Ni structure with near infinite selectivity in a very short time. The process is well suited for fabricating various devices which require a suspended structure, such as in radio-frequency microelectromechanical system switches, tunable capacitors, high-Q suspended inductors and suspended-gate metal-oxide semiconductor field-effect transistors. 相似文献
4.
《International Journal of Engineering Science》2006,44(11-12):683-698
This paper deals with the theoretical investigation of the effect of rotation on a layer of micropolar ferromagnetic fluid heated from below saturating a porous medium subjected to a transverse uniform magnetic field. For a flat fluid layer contained between two free boundaries, an exact solution is obtained using a linear stability analysis theory and normal mode analysis method. For the case of stationary convection, the effect of various parameters like medium permeability, rotation, non-buoyancy magnetization, coupling parameter, spin diffusion parameter and micropolar heat conduction has been analyzed. The critical magnetic thermal Rayleigh number for the onset of instability are also determined numerically for sufficiently large values of magnetic parameter M1 and results are depicted graphically. The principle of exchange of stabilities is found to hold true for the micropolar ferromagnetic fluid saturating a porous medium heated from below in the absence of micropolar viscous effect, microinertia and rotation. The oscillatory modes are introduced due to the presence of the micropolar viscous effect, microinertia and rotation, which were non-existent in their absence. The sufficient conditions for the non-existence of overstability are also obtained. 相似文献
5.
《International Journal of Fatigue》2002,24(2-4):477-495
The general purpose of this article is to review the main ideas in fatigue analysis of composites in the context of the application of probabilistic methods, both theoretical and computational. That is why most deterministic concepts of composite materials fatigue are summarized together with stochastic approaches. The application of the perturbation based Stochastic Finite Element Method (SFEM) to fatigue analysis of homogeneous and heterogeneous media is shown. Further, homogenization method in its effective modules approach is proposed below for application in fatigue processes modeling of linear elastic periodic random composites. Considering stochastic character of the analysis, the reliability tools appropriate to multicomponent materials are presented together with the specially adopted brittle and ductile fracture criteria. 相似文献
6.
《Engineering Fracture Mechanics》2004,71(4-6):513-528
Acrylic bone cement is used to fixate hip replacement implants into the bone. Creep and fatigue failure of the cement promote failure of the implant. For the purpose of implant testing, we derived a finite element algorithm that simulates creep and damage accumulation in acrylic bone cement. The simulation combines a Maxwell creep model, with a 3-D continuum damage mechanics approach modeling anisotropic damage accumulation. The technical details of the simulation are described. In a first application tensile fatigue tests on tubular cement specimens are simulated. The creep elongation and fatigue life of the specimens, as predicted by the simulations, are successfully correlated to the experimental results. In a second application, the simulation is used to predict creep and fatigue failure of the cement mantle around two hip implants with different clinical outcomes. It is shown how the simulation is able to predict the locations of cement damage around the implants, and the amounts of implant migration attributable to creep. 相似文献
7.
《低温学》1986,26(2):97-102
This Paper summarizes and correlates the liquid helium pump data obtained previously in two separate test programs. In normal helium the second set of data shows a large performance improvement over the first set as a result of changes in measurement methods and in the pump itself. Peak pump efficiencies of 46% were measured. The pump appeared to perform approximately the same in He II as in He I; however, the He II data are not adequate for system design or analyses. Therefore, a new pump test program is planned to test the improved version of the pump in an apparatus designed specifically for He II. 相似文献
8.
9.
《Acta Metallurgica Materialia》1990,38(12):2537-2552
Superplasticity during temperature cycling of particle reinforced metal matrix composites has been studied over a range of reinforcement sizes and volume fractions. Above a critical volume and thermal cycle amplitude, the mean strain per cycle is proportional to stress and approximately proportional to cycle amplitude. For a given thermal cycle the constant of proportionality with respect to stress increases with reinforcement fraction to a maximum at around 30%; it then decreases with further increase in reinforcement. Transmission electron microscopy revealed no characteristics dislocation substructure; even after 90% strain the material was indistinguishable from its undeformed state. The experimental results confirm an internal plastic flow model for the phenomenon rather than an enhanced creep. A model of the process derived from the Lévy-Von Mises equations predicts both the effect of thermal cycle amplitude the MMC microstructure on the enhanced creep rate. 相似文献
10.