全文获取类型
收费全文 | 2207篇 |
免费 | 376篇 |
国内免费 | 155篇 |
专业分类
化学 | 425篇 |
晶体学 | 14篇 |
力学 | 149篇 |
综合类 | 21篇 |
数学 | 563篇 |
物理学 | 1566篇 |
出版年
2024年 | 2篇 |
2023年 | 26篇 |
2022年 | 53篇 |
2021年 | 54篇 |
2020年 | 59篇 |
2019年 | 50篇 |
2018年 | 54篇 |
2017年 | 53篇 |
2016年 | 85篇 |
2015年 | 54篇 |
2014年 | 132篇 |
2013年 | 165篇 |
2012年 | 123篇 |
2011年 | 163篇 |
2010年 | 112篇 |
2009年 | 153篇 |
2008年 | 152篇 |
2007年 | 163篇 |
2006年 | 144篇 |
2005年 | 102篇 |
2004年 | 77篇 |
2003年 | 97篇 |
2002年 | 77篇 |
2001年 | 64篇 |
2000年 | 53篇 |
1999年 | 59篇 |
1998年 | 96篇 |
1997年 | 38篇 |
1996年 | 45篇 |
1995年 | 38篇 |
1994年 | 32篇 |
1993年 | 20篇 |
1992年 | 26篇 |
1991年 | 17篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有2738条查询结果,搜索用时 15 毫秒
41.
42.
本文提出一个无粘的底部压力模型。证明了在给定反压的情况下,超音出口的涡轮叶栅的叶片尾缘的底压以及叶型损失可由该模型确定。与无粘的流场计算相结合,可用该模型计算二维叶栅的底压。对模型的参数研究表明:具有正曲率的喉道下游叶背型面将有利于减少损失;而出口为音速时流动则最为不利。 相似文献
43.
Xu Liping 《Acta Mechanica Sinica》1991,7(1):39-45
An inviscid base pressure model for transonic turbine blade has been presented. It has been shown that for a given back pressure
the base pressure at the trailing edge, and the profile loss of a turbine blade are fixed according to the model and the base
pressure can be calculated with the help of an inviscid numerical scheme. A parameteric study on the model shows that a blade
profile with positive curvature downstream of the throat is advantageous for generating less loss, whilst the worst situation
is when the exit flow reaches the sonic condition. 相似文献
44.
V.A. Osinov 《Continuum Mechanics and Thermodynamics》1998,10(5):253-268
The paper deals with propagation of plane wave fronts in a solid with a non-linear relation between stress and deformation.
The objective is to calculate the distance that a wave front covers before it loses continuity. The formulae derived for a
general quasi-linear system of two equations are applied to the propagation of plane compression waves in dry and partially
saturated granular bodies. In the case of a saturated body with gas bubbles, the influence of gas and capillary pressure on
the stiffness of the body is taken into account. Numerical calculations relevant to soil mechanics are presented. For the
numerical calculations a constitutive equation of the hypoplasticity theory for granular materials has been used.
Received November 1, 1997 相似文献
45.
Dimitre Hadjistamov 《Rheologica Acta》1996,35(4):364-368
The work describes a way to obtain loss modulus and storage modulus master curves from oscillatory measurements of silicone oils.The loss modulus master curve represents the dependence of the viscous flow behavior on ·
0
*
and the storage modulus master curve — the dependence of the elastic flow behavior on ·
0
*
.The relation between the values of the loss modulus and storage modulus master curves (at a certain frequency) is a measurement of the viscoelastic behavior of a system. The G/G-ratio depends on ·
0
*
which leads to a viscoelastic master curve. The viscoelastic master curve represents the relation between the elastic and viscous oscillatory flow behavior. 相似文献
46.
47.
V. M. Kulik 《Journal of Applied Mechanics and Technical Physics》2007,48(2):221-228
The longitudinal and transverse components of deformation of the surface of a flat layer of a viscoelastic material glued
onto a solid base under the action of a traveling pressure wave are determined. The coating compliance is described by two
components corresponding to two components of surface displacement. The dimensionless compliance components depend only on
the viscoelastic properties of the material, the ratio of the wave length to the layer thickness λ/H, and the ratio of the
wave velocity to the velocity of propagation of shear oscillations V/C
t
0
. Data on the dynamic compliance are presented for 0.3 < λ/H < 30 and 0.1 < V/C
t
0
< 10. The compliance is demonstrated to be determined by its absolute value and by the phase lag of strain from pressure.
The effect of viscous losses in the material and compressibility of the latter on the dynamic compliance is analyzed. An anomalous
behavior of the compliance with the wave velocity being greater than a certain critical value is explained.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 90–97, March–April, 2007. 相似文献
48.
板结构功率流的参数研究 总被引:1,自引:0,他引:1
板以及肋板结构在工程中有着广泛的应用,其振动嗓声问题一直受到理论和工程领域的关注。本文在板结构功率流理论的基础上 ̄[1],对板的损耗因子和不同加肋形式对其功率流的影响进行了分析和测量。 相似文献
49.
骨具有力电性质,这一性质可促进骨组织生长。骨既是生理器官又是介电材料,在交变电场作用下,其表现行为可能有生理作用。为此,本文测量了骨悬臂梁试样在交变电场下的表面温升与顶端挠度。发现在电压70V,频率为10~70kHz的交流电场下,最大表面温升达到2~4℃,最大挠度变化为9.0~78.7μm;在频率10kHz,电压为70~175V的交流电场下,最大表面温升达到4~6℃,最大挠度变化为13.0~114.3μm。同时测量了两种经典介电材料有机玻璃和聚乙烯在交变电场下的温升与顶端挠度,最大温升低于0.5℃,但是挠度与骨试样相当,所以相对高温升是骨特有的性质。将交流电压有效值替换成相同幅值的直流电压时,最大温升也低于0.5℃,基本没有挠度变化,所以相对的高温升反映了骨的交流性质。分析后认为,骨在交变电场作用下的温升由胶原的介电损耗引起。实验数据显示,骨在交变电场下,表面温度变化与加载电压的平方成正比,且在实验加载的10~70kHz频段内,骨的介电常数随频率的变化明显。 相似文献
50.
《Current Applied Physics》2020,20(5):638-642
A series of bio-silica incorporated barium-ferrite-composites with the composition of (x)Bio-SiO2:(80-x)γ-Fe2O3:(20)BaO, where x = 0, 1, 2, and 3 wt% were prepared using the modified solid-state reaction method. The influence of different bio-silica (extricated from sintered rice husk) contents on the surface morphologies, structures, and magnetic characteristics of these composites were assessed. The relative complex permittivity and permeability were resolved using the Nicholson-Ross-Weir strategy in the frequency range of 8–13 GHz. Meanwhile, the reflection loss was estimated through the transmission/reflection line theory to assess the MW absorption properties of the composites. Incorporation of the bio-silica in the barium ferrite composites generated a new hexagonal phase (Ba3Fe32O51) and a tetragonal phase (BaFeSi4O10) which led to a decrease in the saturation magnetization and significant shift in the MW frequency absorption peak positions. 相似文献