全文获取类型
收费全文 | 7517篇 |
免费 | 650篇 |
国内免费 | 473篇 |
专业分类
化学 | 1561篇 |
晶体学 | 65篇 |
力学 | 4495篇 |
综合类 | 97篇 |
数学 | 654篇 |
物理学 | 1768篇 |
出版年
2024年 | 10篇 |
2023年 | 48篇 |
2022年 | 216篇 |
2021年 | 266篇 |
2020年 | 198篇 |
2019年 | 138篇 |
2018年 | 153篇 |
2017年 | 214篇 |
2016年 | 276篇 |
2015年 | 214篇 |
2014年 | 270篇 |
2013年 | 477篇 |
2012年 | 277篇 |
2011年 | 350篇 |
2010年 | 280篇 |
2009年 | 348篇 |
2008年 | 367篇 |
2007年 | 424篇 |
2006年 | 432篇 |
2005年 | 383篇 |
2004年 | 386篇 |
2003年 | 319篇 |
2002年 | 246篇 |
2001年 | 267篇 |
2000年 | 275篇 |
1999年 | 225篇 |
1998年 | 189篇 |
1997年 | 187篇 |
1996年 | 191篇 |
1995年 | 150篇 |
1994年 | 127篇 |
1993年 | 123篇 |
1992年 | 112篇 |
1991年 | 96篇 |
1990年 | 63篇 |
1989年 | 54篇 |
1988年 | 47篇 |
1987年 | 51篇 |
1986年 | 45篇 |
1985年 | 30篇 |
1984年 | 25篇 |
1983年 | 13篇 |
1982年 | 33篇 |
1981年 | 19篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1973年 | 3篇 |
1957年 | 4篇 |
排序方式: 共有8640条查询结果,搜索用时 828 毫秒
871.
Adriano Montanaro 《Journal of Elasticity》1997,46(3):217-221
The proofs of the Fedorov–Stippes and Fedorov's theorems, which hold for linearly elastic homogeneous bodies in natural configurations, remain valid for any linearly elastic medium with initial stress provided that Hooke's tensor be replaced by a suitable elasticity tensor. 相似文献
872.
Shape memory polymers are novel materials that can be easily formed into complex shapes, retaining memory of their original
shape even after undergoing large deformations. The temporary shape is stable and return to the original shape is triggered
by a suitable mechanism such as heating. In this paper, we develop constitutive equations to model the mechanical behavior
of crystallizable shape memory polymers. Crystallizable shape memory polymers are called crystallizable because the temporary
shape is fixed by a crystalline phase, while return to the original shape is due to the melting of this crystalline phase.
The modeling is done using a framework that was developed recently for studying crystallization in polymers ([28], [25], [27],
[31]) and is based on the theory of multiple natural configurations. In this paper we formulate constitutive equations for
the original amorphous phase and the semi-crystalline phase that is formed after the onset of crystallization. In addition
we model the melting of the crystalline phase to capture the return of the polymer to its original shape. The model has been
used to simulate a typical uni-axial cycle of deformation, the results of this simulation compare very well with experimental
data. In addition to this we also simulate circular shear of a hollow cylinder and present results for different cases in
this geometry.
Received: January 5, 2005 相似文献
873.
A configuration of reversal shear interferometer suitable for measurement of spatial coherence of high average power, large cross-section laser beam has been discussed. Ghost-less beam splitters in which unwanted multiple reflections from the surfaces have been suppressed by total internal reflection are used for beam splitting and re-combination. Advantages and drawbacks of this configuration have been discussed. 相似文献
874.
In this paper we develop a theory for the calculation of the surface shear viscosity of a planar liquid-vapor interface. The theory is an extension of the generalized hydrodynamics formalism, originally developed for the calculation of linear transport coefficients in isotropic bulk fluids. We develop an expression for the surface shear viscosity in terms of the actual shear viscosity profile in the interfacial region. We derive an expression for this profile in terms of the first four moments of the autocorrelation function of the transverse parallel velocity (the component of velocity parallel to k, which is the projection of k on to the interface). Finally, we calculate these moments for a planar liquid-vapor interface. 相似文献
875.
沿抛物线分布的各向异性曲线裂纹问题 总被引:8,自引:1,他引:7
文章利用Stroh法及映射法研究了沿抛物线Ω分布的各向异性曲线裂纹问题,获得了有关的应力及位移场,这种解不仅适用于平面问题,而且也适用于反平面变形或两者偶合的情形,对于单位边裂纹和双曲边裂纹问题,文章还获得了它们的应力和位移场的封闭解,并求得了相应斥强主因子及裂纹面上的张开位移。 相似文献
876.
低温胁迫下香蕉叶片Chla荧光动力学参量的变化及其品种差异性 总被引:7,自引:0,他引:7
低温胁迫下,广东2号香蕉品种和巴西香蕉品种Williams的叶绿素(Chla)荧光动力学参量FⅤ/Fm、ΔFⅤ/FT以及williams品种的FIV/FⅤ均呈下降趋势,两个品种的荧光上升半时间T1/2及广东2号的FIV/FⅤ呈上升趋势.其中,Williams的FⅤ/Fm、ΔFⅤ/FT和T1/2的变化幅度小于广东2号,表明低温胁迫通过抑制光合电子传递速度和PSⅡ无活性中心含量的提高使香蕉叶片PSⅡ原初光能转换效率下降,相同低温对广东2号的影响大于对Williams的影响.FⅤ/Fm和ΔFⅤ/FT可以作为评价香蕉幼苗抗冷性的物理指标. 相似文献
877.
878.
The paper proposes an approach to form (by special heat treatment) a structure and phase composition of martensitic steel
that would enhance its ductility in the high-strength state. A correlation is experimentally established between the stability
of fracture resistance and ductility in linear and plane stress states. The behavior of the scatterband of the ultimate strength
with increase in the degree of ductility is analyzed. The possibility of predicting the ultimate strength from the lower edge
of its scatterband is demonstrated with an example of a circular cylindrical shell
__________
Translated from Prikladnaya Mekhanika, Vol. 42, No. 8, pp. 68–78, August 2006. 相似文献
879.
用X射线衍射(XRD)技术和显微Raman散射方法对金属有机化学气相沉积(MOCVD)法生长的六方相InxGa1-xN薄膜样品进行了研究,观察到了相分离现象和LO声子-等离子耦合模(LPP+),讨论了InxGa1-xN的A1(LO)模被屏蔽的主要物理机制.同时,对Raman谱中E2和A1(TO)声子模进行了分析和讨论.在InxGa1-xN样品的低温Raman谱中还观察到单电子跃迁产生的Raman散射信号.
关键词:
Raman散射
X射线衍射
相分离
应力
LO声子-等离子耦合 相似文献
880.
The residual stresses in a shrink-fit specimen were measured ultrasonically, using shear-horizonal (SH) waves transmitted and received by noncontacting electromagnetic acoustic transducers. The presence of stress induces a small change in the velocity of the SH-waves. The difference in velocities of orthogonally polarized SH-waves (acoustic birefringence) was measured with a simple time-interval averaging system; this velocity difference can be related to the difference of principal stresses. The presence of material anisotropy (texture) in the specimen also causes relative velocity changes comparable to stress-induced changes. A simple method was used to remove the anisotropy-dependent component of the total relative velocity change, thereby allowing a determination of residual stress. This method consisted of measuring the birefringence in unstressed reference specimens and subtracting it from the birefringence measured at stressed locations. For the specimen used here, good agreement between theoretical and experimental values of stress was obtained. 相似文献