全文获取类型
收费全文 | 9630篇 |
免费 | 2280篇 |
国内免费 | 569篇 |
专业分类
化学 | 1278篇 |
晶体学 | 46篇 |
力学 | 2462篇 |
综合类 | 122篇 |
数学 | 2319篇 |
物理学 | 6252篇 |
出版年
2024年 | 16篇 |
2023年 | 94篇 |
2022年 | 144篇 |
2021年 | 188篇 |
2020年 | 283篇 |
2019年 | 219篇 |
2018年 | 251篇 |
2017年 | 300篇 |
2016年 | 319篇 |
2015年 | 258篇 |
2014年 | 531篇 |
2013年 | 612篇 |
2012年 | 583篇 |
2011年 | 714篇 |
2010年 | 586篇 |
2009年 | 594篇 |
2008年 | 668篇 |
2007年 | 668篇 |
2006年 | 630篇 |
2005年 | 613篇 |
2004年 | 570篇 |
2003年 | 536篇 |
2002年 | 408篇 |
2001年 | 393篇 |
2000年 | 322篇 |
1999年 | 260篇 |
1998年 | 241篇 |
1997年 | 209篇 |
1996年 | 167篇 |
1995年 | 169篇 |
1994年 | 127篇 |
1993年 | 134篇 |
1992年 | 114篇 |
1991年 | 113篇 |
1990年 | 76篇 |
1989年 | 75篇 |
1988年 | 63篇 |
1987年 | 50篇 |
1986年 | 26篇 |
1985年 | 27篇 |
1984年 | 26篇 |
1983年 | 14篇 |
1982年 | 25篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1973年 | 6篇 |
1971年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
双驱动激波管稀疏波破膜技术研究 总被引:1,自引:0,他引:1
本文介绍了在双驱动激波管中运用稀疏波破膜的技术。在以压缩空气和氮气作实验气体的情形下,实验研究了中间段长度、稀疏波强度及中间段B膜的破膜压力(压差)对第二激波追韩第一激波的影响。实验结果表明:中间段的长短,显著地制约着前后两道激波的间隔;稀疏波强度及中间段B膜的破膜压力对稀疏波破膜时间及第二激小对反射稀疏波的追赶有重要影响。 相似文献
82.
On Free Nonlinear Vibrations of Fluid-Filled Cylindrical Shells with Multiple Natural Frequencies 总被引:1,自引:0,他引:1
Nonlinear free vibrations of a cylindrical shell fully filled with a perfect incompressible fluid are studied. The case is
examined where two natural frequencies of the shell are close
__________
Published in Prikladnaya Mekhanika, Vol. 41, No. 10, pp. 127–138, October 2005 相似文献
83.
P.J. Tan J.J. Harrigan Z. Zou S. Li 《Journal of the mechanics and physics of solids》2005,53(10):2174-2205
This study of the dynamic compressive strength properties of metal foams is in two parts. Part I presents data from an extensive experimental study of closed-cell Hydro/Cymat aluminium foam, which elucidates a number of key issues and phenomena. Part II focuses on modelling issues.The dynamic compressive response of the foam was investigated using a direct-impact technique for a range of velocities from 10 to . Elastic wave dispersion and attenuation in the pressure bar was corrected using a deconvolution technique.A new method of locating the point of densification in the nominal stress-strain curves of the foam is proposed, which provides a consistent framework for the definition of the plateau stress and the densification strain, both essential parameters of the ‘shock’ model in Part II. Data for the uniaxial, plastic collapse and plateau stresses are presented for two different average cell sizes of approximately 4 and 14 mm. They show that the plastic collapse strength of the foam changes significantly with compression rate. This phenomenon is discussed, and the distinctive roles of microinertia and ‘shock’ formation are described. The effects of compression rates on the initiation, development and distribution of cell crushing are also examined. Tests were carried out to examine the effects of density gradient and specimen gauge length at different rates of compression and the results are discussed. The origin of the conflicting conclusions in the literature on the correlation between nominal strain rate (ratio of the impact velocity Vi to the initial gauge length lo of the specimen) and the dynamic strength of aluminium alloy foams is identified and explained. 相似文献
84.
85.
86.
本文探讨了一种新的激波-非定常边界层相互干扰现象,这种激波-边界层干扰现象既不同于定常激波-边界层干扰现象,又不同于激波在端面反射后与该激波所诱导的边界层之间的干扰现象,而是运动激波与稀疏波和第一激波所诱导的非这常边界层之间的干扰现象,本文对这种现象用微波动力学理论进行分析,并把这种干扰现象看成激波的绕射现象,同时在稀疏波破膜的双驱动激波管中进行实验观察,最后把理论分析与实验观察进行了比较。 相似文献
87.
88.
Matthew E. Peters Christopher S. Bretherton 《Theoretical and Computational Fluid Dynamics》2006,20(5-6):501-524
A composite mesoscale precipitation event and a convectively coupled Kelvin wave produced by a diabatically accelerated cloud resolving model are compared. Special emphasis is placed on the vertical structure of density and moisture perturbations and the interaction of these perturbations with the composited dynamical fields. Both composites share the same general features, a gradual deepening and strengthening of convection followed by deep convection and a stratiform region, quite similar in character to observations and some recent idealized models. Composited frozen moist static energy (FMSE) perturbations are several times larger than virtual temperature perturbations, suggesting moisture is a dominant regulator of convection. An empirically derived two vertical mode decomposition of the dynamical and moisture fields is found to reproduce both composites quite well. The leading vertical modes of FMSE and virtual temperature variability are strongly correlated with the modes of vertical velocity variability; these correlations are strongest at near-zero time lags. Deep convection is associated with moistening in the lower and middle troposphere, while shallow convection is associated with a moist lower troposphere and dry middle and upper troposphere. To the extent that our numerical model is realistic, the empirical modal decomposition provides support for the use of two-mode idealized models for convective interaction with large-scale circulations and guidance for formulating feedbacks between convection and the thermodynamic profile in such models. The FMSE budget leads to an interpretation of the convective life-cycle as a recharge–discharge mechanism in column-integrated FMSE. The budget analysis places diabatic forcing, surface and radiative fluxes into the moist energetic framework. In particular, these fluxes are seen to prolong active convection, but play a passive role in its initiation. The modally decomposed FMSE budget highlights the dynamical importance of the second baroclinic mode in moistening the lower and middle troposphere before convective onset (recharging), and then discharging stored FMSE in the stratiform region. 相似文献
89.
利用Ham ilton变分原理,导出了计及有限变形和横向Possion效应的弹性杆中非线性纵向波动方程.利用Jacob i椭圆正弦函数展开和第三类Jacob i椭圆函数展开法,对该方程和截断的非线性方程进行求解,得到了非线性波动方程的两类准确周期解及相应的孤波解和冲击波解,讨论了这些解存在的必要条件. 相似文献
90.
Liu Zhifang Zhang Shanyuan 《Acta Mechanica Solida Sinica》2006,19(1):1-8
A nonlinear wave equation of elastic rod taking account of finite deformation, transverse inertia and shearing strain is derived by means of the Hamilton principle in this paper. Nonlinear wave equation and truncated nonlinear wave equation are solved by the Jacobi elliptic sine function expansion and the third kind of Jacobi elliptic function expansion method. The exact periodic solutions of these nonlinear equations are obtained, including the shock wave solution and the solitary wave solution. The necessary condition of exact periodic solutions, shock solution and solitary solution existence is discussed. 相似文献