全文获取类型
收费全文 | 172篇 |
免费 | 14篇 |
国内免费 | 16篇 |
专业分类
化学 | 6篇 |
晶体学 | 1篇 |
力学 | 147篇 |
综合类 | 5篇 |
数学 | 6篇 |
物理学 | 37篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 5篇 |
2012年 | 2篇 |
2011年 | 11篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 8篇 |
2007年 | 13篇 |
2006年 | 14篇 |
2005年 | 14篇 |
2004年 | 6篇 |
2003年 | 19篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有202条查询结果,搜索用时 8 毫秒
91.
A linear oscillator (LO) coupled with two vibro-impact (VI) nonlinear energy sinks (NES) in parallel is studied under periodic and transient excitations, respectively. The objective is to study response regimes and to compare their efficiency of vibration control. Through the analytical study with multiple scales method, two slow invariant manifolds (SIM) are obtained for two VI NES, and different SIM that result from different clearances analytically supports the principle of separate activation. In addition, fixed points are calculated and their positions are applied to judge response regimes. Transient responses and modulated responses can be further explained. By this way, all analysis is around the most efficient response regime. Then, numerical results demonstrate two typical responses and validate the effectiveness of analytical prediction. Finally, basic response regimes are experimentally observed and analyzed, and they can well explain the complicated variation of responses and their corresponding efficiency, not only for periodic excitations with a fixed frequency or a range of frequency, but also for transient excitation. Generally, vibration control is more effective when VI NES is activated with two impacts per cycle, whatever the types of excitation and the combinations of clearances. This observation is also well reflected by the separate activation of two VI NES with two different clearances, but at different levels of displacement amplitude of LO. 相似文献
92.
93.
讨论了调谐耦合场作用下的Λ型三能级系统中的无反转光放大(AWI)现象,调谐耦合场同时激励两个基态精细结构能级与激发态能级之间的跃迁,使系统同时呈现电磁诱导透明(EIT)和自发诱导相干凹陷两种特性,而且当调节这个耦合场的频率失谐量在某一特定范围时,系统会在EIT信号上叠加出现AWI现象。研究结果表明:该系统中EIT和自发诱导相干凹陷之间存在能量转移现象,当EIT上出现AWI现象时,虽然激发态能级与基态能级之间没有出现粒子数反转,但是两个基态精细结构能级之间出现了粒子数反转。 相似文献
94.
本文以位移设计方法的概念为主,结合能力谱法提出附加黏滞流体阻尼器结构基于位移的初步设计方法.首先讨论了减震结构基于性能设计方法的实现途径并加以比较;其次定量研究了使用加速度反应谱转换为位移反应谱的条件,分析指出真实位移反应谱(均值)与转换得到的位移反应谱随着场地特征周期的增大,两者之间的差值逐渐增大;在场地条件相同的情况下,阻尼比越大两者的差异也越大.最后结合我国抗震设计规范,给出了主体结构保持弹性状态时,非迭代法确定附加黏滞流体阻尼器的减震结构设计流程.非线性时程分析结果表明该设计方法实用、有效. 相似文献
95.
We demonstrate the laser performances of Nd, Y:SrF2 crystals with Nd'3+ concentrations of 0.15 and 0.43 at.%. The sample with 0.43 at.% Nd3+ concentration yields a maximum output power of 1.023 W at 1056.9 nm with a slope efficiency of 53%. The focal length of the thermal lens is analyzed for the 0.15 at.% Nd3+-doped crystal sample. An improved cavity is designed considering the thermal lens. The maximum output power is 464 mW at 1056.9 nm, with a slope efficiency of 36.1%. The wavelength is tuned within the range of 1049.74-1059.13 nm. 相似文献
96.
Modelling and identifying the parameters of a magneto-rheological damper with a force-lag phenomenon
《Applied Mathematical Modelling》2014,38(15-16):3763-3773
In this study a model based on the Bouc–Wen–Baber–Noori (BWBN) method was proposed to describe the distorted hysteretic behaviour of a self-constructed magneto-rheological (MR) damper whose mechanical performance was measured with an Instron test machine. The experimental results indicated that the MR damper exhibited a force-lag phenomenon. The parameters of the modified BWBN model were identified with the MATLAB SIMULINK Design and Optimisation toolbox. A comparison between the experimental results and modelling predictions revealed that the proposed model could well present the force-lag phenomenon. 相似文献
97.
98.
任意荷载作用下液体粘滞阻尼器在桥梁工程中减震作用探讨 总被引:5,自引:0,他引:5
在桥梁工程中,当需要限制梁端的碰撞或过大的相对位移,经常会在梁端设置液体粘滞阻尼器。由于技术原因,液体粘滞阻尼器在桥梁设计中的参数选取基本上是通过全桥模型的地震非线性时程分析得到的。而在寿命期内,桥梁需要承受各种随机荷载,在具有不同力学特性荷载的激励作用下引起梁端纵向大的响应时,液体粘滞阻尼器是否始终起有利的减震作用,一直困扰着其在桥梁工程中的实践。在液体粘滞阻尼器力学特性研究的基础上,通过矩阵变换得到关于阻尼器的局部动力方程,从变形和受力两个方向对此问题进行探讨,得到液体粘滞阻尼器对于梁端的相对位移、相对速度、相对加速度均有减震作用。但不会得出始终对所有构件的受力有利的结论,并进行了验证。 相似文献
99.
100.
Abhijit Boruah Manash Protim Borpuzari Rahul Kar 《Journal of computational chemistry》2020,41(4):295-304
Performance of the density functionals mainly depends on the proper approximation of exchange-correlation functionals. Modification of various parameters of such functionals, according to the demand of the system, has brought their accuracy level to a new height. Recent reports highlight that Long-range Corrected (LC) functionals are not encouraging in reproducing orbital energies in solvent. Therefore, in this article, we have proposed a tuning scheme for the LC functional for improved orbital energies. In this scheme, the optimized long-range HF exchange and the dielectric constant of the medium are included to modify the form of functionals. The proposed tuning is tested over a set of 103 molecules from IP131 database and fifteen solvent dielectrics. The tuned range separated functionals reproduce orbital eigenvalues in solvent continuum with good accuracy. More importantly, there is a consistency in the error for the tuned functional across the solvent media. © 2019 Wiley Periodicals, Inc. 相似文献