全文获取类型
收费全文 | 379篇 |
免费 | 129篇 |
国内免费 | 7篇 |
专业分类
化学 | 30篇 |
晶体学 | 1篇 |
力学 | 143篇 |
综合类 | 5篇 |
数学 | 60篇 |
物理学 | 276篇 |
出版年
2023年 | 1篇 |
2022年 | 12篇 |
2021年 | 17篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 5篇 |
2017年 | 26篇 |
2016年 | 13篇 |
2015年 | 21篇 |
2014年 | 32篇 |
2013年 | 41篇 |
2012年 | 69篇 |
2011年 | 64篇 |
2010年 | 42篇 |
2009年 | 30篇 |
2008年 | 21篇 |
2007年 | 27篇 |
2006年 | 14篇 |
2005年 | 13篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 4篇 |
1992年 | 1篇 |
排序方式: 共有515条查询结果,搜索用时 31 毫秒
1.
2.
现有考核评价方式侧重期末考试而忽略过程考核,结合材料力学课程,探索一套注重过程考核的评价体系,综合评价学生对本课程的掌握程度,即将期末考试成绩在总评中的占比由70%降低至50%,平时作业、随堂测验、模块测验、实验考核和案例分析成绩各占比10%。新评价方式更加注重对学生学习过程的考核,使学生在整个课程学习过程中保持高度紧张感,提高学习的时效性和目的性,进而提高学生学习材料力学的热情和材料力学课堂教学效果。 相似文献
3.
4.
《Physics letters. A》2020,384(13):126253
This letter is concerned with acoustic wave propagation and transmission in acoustic waveguides with periodically grafted detuned Helmholtz resonators. The interplay of local resonances and Bragg band gaps in such periodic systems is examined. It is shown that, when the resonant frequencies of the resonators are tuned close to a Bragg band gap, the behavior of the Bragg band gap can be affected dramatically. Particularly, by introducing appropriately tuned resonators, the bandwidth of a Bragg band gap can be reduced to zero, leading to a very narrow pass band with great wave attenuation performance near both band edges. The band formation mechanisms of such periodic waveguides are further examined, providing explicit formulae to locate the band edge frequencies of all the band gaps, as well as the conditions to achieve very narrow pass bands in such periodic waveguides. 相似文献
5.
碳化硅块状气凝胶的制备及应用 总被引:1,自引:0,他引:1
碳化硅气凝胶具有高温稳定性、低热膨胀系数、良好的抗热震性以及抗氧化和耐腐蚀等优异的性质,在高温和高腐蚀性环境下的隔热、电磁吸波、过滤和吸附等领域具有较大的应用潜力。然而,块状碳化硅气凝胶的可控制备一直是一项较大的挑战。本文综述了块状碳化硅气凝胶在制备工艺和应用两个方面的研究进展,首先分析总结了各种制备工艺及其优缺点,包括有机/SiO2复合气凝胶碳热还原法、预陶瓷化聚合物裂解法、化学气相沉积法、高温气相渗硅法和碳化硅纳米线组装法;然后,详细介绍了碳化硅气凝胶在高温隔热和电磁吸波两个领域的应用研究进展;最后,展望了碳化硅气凝胶未来的若干发展方向。 相似文献
6.
7.
8.
《International Journal of Solids and Structures》2006,43(14-15):4578-4594
In order to clarify the developmental mechanism of the local plastic buckling and the interaction between axial wave and buckling deformation in an axially impacted slender-bar, the non-linear dynamic equations in the incremental form are derived and solved by use of the finite difference method, with the axial wave front treated as a moving boundary. The initial local-buckling deflection given by the characteristic-value analysis is used as the initial condition of the solution of the equations, instead of the initial imperfection that is assumed in literatures. It is found that the initial buckling deflection with one half-wave, occurring near the impacted end, develops into the higher post-buckling mode with several half-waves, as the axial compression waves propagate forward. The numerical results show that no strain reversal occurs at the early stage of post-buckling process, and the solution corresponding to the tangent-modulus theory is valid for the dynamic plastic post-buckling response of the bar at this stage. The theoretical results are in good agreement with the experimental results reported in the literature. 相似文献
9.
The chaotic dynamics of the softening-spring Duffing system with multi-frequency external periodic forces is studied. It is found that the mechanism for chaos is the transverse heteroclinic tori. The Poincare map, the stable and the unstable manifolds of the system under two incommensurate periodic forces were set up on a two-dimensional torus. Utilizing a global perturbation technique of Melnikov the criterion for the transverse interaction of the stable and the unstable manifolds was given. The system under more but finite incommensurate periodic forces was also studied. The Melnikov‘s global perturbation technique was therefore generalized to higher dimensional systems. The region in parameter space where chaotic dynamics may occur was given. It was also demonstrated that increasing the number of forcing frequencies will increase the area in parameter space where chaotic behavior can occur. 相似文献
10.
TNNS(真航向导航系统)由MS860接收机、INS及处理数据的PC/104架构的嵌入式工控机构成。针对TNNS推导了INS(惯性导航系统)的误差模型,提出了适合于TNNS的降阶扩展卡尔曼滤波算法组合GPS和INS。系统在东海作了三次海试,软件及滤波算法平台由C/C 编制。海上试验表明,组合滤波后,INS的位置误差由100m降低到40m以下;进行最优化滤波后的航向误差σ由原来的0.105°减小为0.034°,纵横摇的误差也大幅减小。整个海试结果表明,在TNNS中组合GPS/INS采用的降阶扩展卡尔曼滤波算法,大幅提高了系统精度和可靠性。 相似文献