全文获取类型
收费全文 | 296篇 |
免费 | 26篇 |
国内免费 | 12篇 |
专业分类
化学 | 2篇 |
力学 | 49篇 |
综合类 | 2篇 |
数学 | 4篇 |
物理学 | 277篇 |
出版年
2024年 | 2篇 |
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 8篇 |
2020年 | 5篇 |
2019年 | 1篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 20篇 |
2011年 | 24篇 |
2010年 | 16篇 |
2009年 | 8篇 |
2008年 | 18篇 |
2007年 | 29篇 |
2006年 | 33篇 |
2005年 | 21篇 |
2004年 | 23篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 14篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
排序方式: 共有334条查询结果,搜索用时 62 毫秒
91.
Melanie Voges Manfred Beversdorff Chris Willert Hartmut Krain 《Experiments in fluids》2007,43(2-3):371-384
As part of an ongoing research project the performance and internal flow field of a high-pressure ratio centrifugal compressor
is being investigated. Based on previous, primarily, point-wise laser-optical measurements the compressor was redesigned and
resulted in an improved impeller and diffuser with a single-stage pressure ratio of 6:1 at 50,000 rpm. Current research activities
involve the use of particle image velocimetry (PIV) to analyze and further improve the understanding of the complex flow phenomena
inside the vaned diffuser given the capability of PIV of capturing spatial structures. The study includes phase-resolved measurements
of the flow inside a diffuser vane passage with respect to the impeller blade position. Both, instantaneous and phase-averaged
velocity fields are presented. The flow field results obtained by PIV are to be used for future validation of the related
CFD calculations, which in turn are expected to lead to further improvements in compressor performance. In addition, the potential
of stereo PIV for this type of turbomachinery application could be successfully demonstrated. 相似文献
92.
93.
跨音速压气机级的三维周期性非定常流动计算 总被引:1,自引:0,他引:1
对跨音速压气机级动静叶排相干形成的三维非定常流场进行了数值研究,利用时间推进LU-SGS稳式迭代法求解三维非定常欧拉方程,对流项采用高分辨率NND格式离散。对某压气机第一级动静叶排相干非定常流场的计算结果表明,本文方法不仅在收敛速度上明显地优于一般显式方法,而且保持了流场中激波的高分辨率,适于推广到计算量巨大的的多级轴流压气机三维非定常流场的数值分析问题 相似文献
94.
In this study we develop the exact second order formalism of piezoelectric structures under an external mechanical stress. Indeed, previous models are approximated since they consist in deriving all the equations in the natural coordinate system (corresponding to the pre-stress free case). Hence, our exact formalism proposes to obtain the whole of equations in the current coordinate system (which is the coordinate system after the pre-deformation). Then, this exact formalism is used to derive the modified Christoffel equations and the modified KLM model. Finally, we quantify the correction with the approximate formalism on several transfer functions and electro-mechanical parameters for a non hysteretic material (lithium niobate). In conclusion, we show that for this material, significant corrections are obtained when studying the plane wave velocities and the electrical input impedance (about 4%), whereas other parameters such as coupling coefficient and impulse response are less influenced by the choice of coordinate systems (corrections less than 0.5%). 相似文献
95.
96.
RF脉冲展宽器用来把高功率窄脉冲变换为较低功率的长脉冲,CLIC实验装置CTFⅡ中的功率提取结构已经可以提供功率达280MW,脉宽16ns的30GHz RF脉冲,为了用它来研究加速结构的最高表面场强和脉宽的关系,设计了30GHz RF脉冲展宽器,完成了系统设计,微波部件的设计及加工,系统的调试,最后安装在CTFⅡ上,并成功进行了高功率实验. 相似文献
97.
98.
99.
多级轴流压气机全工况特性数值模拟 总被引:8,自引:1,他引:7
采用一种快速求解三维粘性流场的计算方法求解某多级轴流压气机内部流场及全工况特性。该方法以LU-SGS-GE隐式格式和 MUSCL TVD迎风格式为基础,结合壁面函数方法和简单的混合长度湍流模型,使用多重网格迭代加速收敛技术对三维可压缩雷诺平均Navie-Stokes方程进行求解.叶列间参数的传递采用混合平面方法并应用了微机网络并行计算技术.首先对一个五排压气机(进口导叶加两级)进行了全工况特性计算,并对计算结果做了详细分析.然后对前三排(进口导叶加一级)进行了全工况特性计算并与五排联赛的计算结果进行了对比,对多级环境对单级性能的影响机理做了初步探讨。 相似文献
100.
A theoretical method for calculating the absorption coefficient of the multi-layer absorbers composed of perforated plates, airspaces and porous materials is proposed. Initially, for multi-layer absorbers composed either of perforated plates and airspaces or perforated plates and porous materials, the acoustic impedance is calculated using an electro-acoustic analogy. Then, for multi-layer absorbers composed of perforated plates, airspaces and porous materials, the acoustic impedance is calculated using an iterative method. Finally, theoretical calculations for the absorption coefficient of three types of multi-layer absorbers composed of different materials and including perforated plates are carried out. The results are validated by experimental results. 相似文献