全文获取类型
收费全文 | 329篇 |
免费 | 8篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 2篇 |
综合类 | 11篇 |
化学工业 | 47篇 |
金属工艺 | 13篇 |
机械仪表 | 64篇 |
建筑科学 | 22篇 |
矿业工程 | 19篇 |
能源动力 | 40篇 |
水利工程 | 2篇 |
石油天然气 | 7篇 |
无线电 | 15篇 |
一般工业技术 | 49篇 |
冶金工业 | 4篇 |
原子能技术 | 21篇 |
自动化技术 | 25篇 |
出版年
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 2篇 |
2014年 | 13篇 |
2013年 | 26篇 |
2012年 | 12篇 |
2011年 | 23篇 |
2010年 | 18篇 |
2009年 | 14篇 |
2008年 | 24篇 |
2007年 | 21篇 |
2006年 | 22篇 |
2005年 | 24篇 |
2004年 | 21篇 |
2003年 | 22篇 |
2002年 | 12篇 |
2001年 | 2篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有341条查询结果,搜索用时 15 毫秒
11.
M. Turkyilmazoglu 《Computers & Fluids》2003,32(3):353-371
A numerical study has been undertaken to investigate the notion of absolute/convective instability in laminar incompressible trailing edge flows past wedge-like shapes with curved boundaries of the form y=α(−x)m. The effects of various trailing edge shapes m and relative thickness α on the flow separation and the development of instabilities in the vicinity of trailing edge are investigated. The nonlinear viscous-inviscid interaction equations, which have been derived by means of the asymptotic theory of flow separation, are solved first numerically to construct genuine mean velocity profiles representing the correct flow in the vicinity of the trailing edge. The absolute/convective nature of the asymptotically formed velocity profiles via a composite expansion is then ascertained by using a spatio-temporal analysis based on the Briggs-Bers pinching criterion. Although no absolute growth is encountered upstream of the trailing edge of the airfoil shapes considered, in particular the wake region behind the trailing edge of Joukowski type profiles is found to be persistently susceptible to absolute instability. It is found that separation is enhanced as the relative thickness of the airfoil gets bigger. This, in turn, is shown to lead to an additional enhancement of the absolute instability character by both increasing the absolute growth rate as well as the extent of the unstable region. Shedding frequency of the Karman vortex street is also determined behind the trailing edge shapes considered. 相似文献
12.
13.
《矿业科学技术学报(英文版)》2016,26(3):471-476
A limestone mine in Ohio has had instability problems that have led to massive roof falls extending to the surface. This study focuses on the role that weak, moisture-sensitive floor has in the instability issues.Previous NIOSH research related to this subject did not include analysis for weak floor or weak bands and recommended that when such issues arise they should be investigated further using a more advanced analysis. Therefore, to further investigate the observed instability occurring on a large scale at the Ohio mine, FLAC3 D numerical models were employed to demonstrate the effect that a weak floor has on roof and pillar stability. This case study will provide important information to limestone mine operators regarding the impact of weak floor causing the potential for roof collapse, pillar failure, and subsequent subsidence of the ground surface. 相似文献
14.
Silver nanowire transparent electrodes have received much attention as a replacement for indium tin oxide, particularly in organic solar cells. In this paper, we show that when silver nanowire electrodes conduct current at levels encountered in organic solar cells, the electrodes can fail in as little as 2 days. Electrode failure is caused by Joule heating which causes the nanowires to breakup and thus create an electrical discontinuity in the nanowire film. More heat is created, and thus failure occurs sooner, in more resistive electrodes and at higher current densities. Suggestions to improve the stability of silver nanowire electrodes are given. 相似文献
15.
The focus of this study is the analysis of the onset of a shear band in saturated soils under biaxial stress conditions taking into account bifurcation in both pore pressure and soil skeleton. By considering the saturated soil as a two-phase medium, the inhomogeneous displacement and pore pressure fields are assumed to be nonlinear and satisfy the continuity conditions of displacements, displacement gradients and excess pore pressure on the boundaries of the band. It is shown that bifurcation may take place in loose, contractive soils in the form of two-phase diffuse mode or localized mode of soil skeleton deformation. For low permeability saturated soils, the onset of a shear band occurs at peak friction, with the shear band parallel to Coulomb's failure plane. Numerical examples using a simple stress–strain model are given to demonstrate the occurrence of the onset of a shear band and its inclination, as a function of the void ratio and the initial consolidation pressure. 相似文献
16.
An experimental study was carried out to investigate the effect of a splitter plate on wake flows downstream of a circular cylinder symmetrically placed in a confined channel. A particle image velocimetry (PIV) measurement was applied to visualize the flow structure and analyze changes in the vortex shedding process. The control elements of the splitter plate length, L/D (D is the cylinder diameter) was varied from 0 to 1.5 and Reynolds number, ReD was considered at 2400 and 3000. The experimental results showed that the splitter plate had an influence on stabilization of wake turbulences in a confined channel. For shorter splitter plate length of L/D=0.5 and 0.75 cases, flow structures were significantly modified and the vortex shedding frequency decreased as compared with bare cylinder cases. For longer splitter plate length of L/D=1, 1.25 and 1.5 cases, the generation of a secondary vortex was observed based on the snapshot proper orthogonal decomposition (snapshot POD) analysis. In addition, turbulent characteristics corresponding to turbulent kinetic energy (TKE) and Reynolds shear stress correlations took the lowest values and the dominant vortex shedding frequency disappeared. There was an optimal value of the splitter plate length at L/D=1 on suppression of velocity fluctuations. Moreover, the stabilizing effect of a splitter plate was more obvious at Reynolds number of ReD=3000 than that at ReD=2400. 相似文献
17.
利用边坡监测结果和室内试验,对湘江阶地上的粉质粘土边坡失稳机理进行全面的研究。研究结果表明,土体开挖成坡后,边坡中出现了由应力重分布引起的应力集中和张应力带;而大量的水进入土体后,一方面降低了土的粘聚力和内摩擦角,并使土的粒间吸力丧失,另一方面增加了土的容重,产生了不利于边坡稳定的静水和动水压力。张应力和水的共同作用,是导致了边坡失稳的直接原因。 相似文献
18.
针对成庄煤矿四盘区层一次采全高煤壁失稳问题,对观测统计数据进行分析,发现片帮主要表现形式分五种:顶部、腰部、顶底部、底部以及斜切片帮,据此采用对顶板超前预爆破和煤壁超前预加固技术来控制大采高煤壁稳定性,不仅对煤壁失稳的控制取得了良好的效果,而且经济效益显著。可为相似条件下的厚煤层一次采全高煤壁失稳控制提供借鉴。 相似文献
19.
20.