全文获取类型
收费全文 | 1795篇 |
免费 | 233篇 |
国内免费 | 95篇 |
专业分类
化学 | 754篇 |
晶体学 | 61篇 |
力学 | 137篇 |
综合类 | 7篇 |
数学 | 12篇 |
物理学 | 1152篇 |
出版年
2024年 | 4篇 |
2023年 | 9篇 |
2022年 | 28篇 |
2021年 | 30篇 |
2020年 | 46篇 |
2019年 | 53篇 |
2018年 | 56篇 |
2017年 | 40篇 |
2016年 | 66篇 |
2015年 | 68篇 |
2014年 | 57篇 |
2013年 | 250篇 |
2012年 | 109篇 |
2011年 | 114篇 |
2010年 | 84篇 |
2009年 | 91篇 |
2008年 | 107篇 |
2007年 | 103篇 |
2006年 | 148篇 |
2005年 | 65篇 |
2004年 | 69篇 |
2003年 | 72篇 |
2002年 | 87篇 |
2001年 | 60篇 |
2000年 | 54篇 |
1999年 | 44篇 |
1998年 | 34篇 |
1997年 | 20篇 |
1996年 | 14篇 |
1995年 | 19篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 19篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1959年 | 1篇 |
排序方式: 共有2123条查询结果,搜索用时 15 毫秒
51.
Characterisation of precipitate phases in magnesium alloys using electron microdiffraction 总被引:1,自引:0,他引:1
Recent results of the characterisation of the structure, morphology and orientation of fine-scale, strengthening precipitate phases in selected magnesium alloys using transmission electron microscopy and microdiffraction are reviewed. The strengthening precipitate phases in Mg–Y–Nd alloys, aged to maximum hardness at 250°C, have been found to include two metastable precipitate phases β′ and β1, and the equilibrium precipitate β. The β′ phase has a globular form, a base-centred orthorhombic structure (potential point group of mmm), and an orientation relationship such that (100)β′//(1
10)α, [001]β′//[0001]α. The β1 phase has an f.c.c. structure (space group
and an orientation relationship that may be described by
(100)β1//[0001]α, and forms as plates parallel to
The β phase has an f.c.c. structure (space group
) and also forms as plates on
with an orientation relationship with the matrix phase that is identical to that observed for β1 phase. Precipitates in Mg–Al alloys, aged isothermally at 200°C, invariably have the b.c.c. structure of the equilibrium precipitate phase β (Mg17Al12). Three orientation relationships have been observed between β and the matrix phase. Most precipitates have an irrational orientation relationship that approximates to the Burger's relationship, (001)β//(0001)α,
and a faceted lath morphology with habit plane parallel to (0001)α. A minor fraction of precipitates posses an orientation relationship that is of the form
and have a prismatic rod morphology. The long axes of these rods are parallel to [0001]α, and their faceted surfaces are parallel to
A few precipitates are observed to have an orientation relationship such that
and a rod shape, with their long axes apparently inclined with respect to [0001]α. 相似文献
Full-size image
Full-size image
52.
53.
A. Díaz-Sánchez A. Pérez-Garrido 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(4):483-486
The relaxation of the specific heat and the entropy to their equilibrium values is investigated numerically for the three-dimensional
Coulomb glass at very low temperatures. The long time relaxation follows a stretched exponential function, f (t) = f
0exp - (t/τ)β
, with the exponent β increasing with the temperature. The relaxation time diverges as an Arrhenius law when T→ 0.
Received 24 May 2001 and Received in final form 12 September 2001 相似文献
54.
A detailed study of the superconducting state parameters (SSP) viz. electron–phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature TC, isotope effect exponent and effective interaction strength NOV of ten alkali–alkali binary alloys i.e. Li1−xNax, Li1−xKx, Li1−xRbx, Li1−xCsx, Na1−xKx, Na1−xRbx, Na1−xCsx, K1−xRbx, K1−xCsx and Rb1−xCsx are made within the framework of the model potential formalism and employing the pseudo-alloy-atom (PAA) model for the first time. We use the Ashcroft’s empty core (EMC) model potential for evaluating the superconducting properties of alkali alloys. Five different forms of local field correction functions viz. Hartree (H), Taylor (T), Ichimaru–Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used to incorporate the exchange and correlation effects. A considerable influence of various exchange and correlation functions on λ and μ* is found from the present study. Reasonable agreement with the theoretical values of the SSP of pure components is found (corresponding to the concentration x = 0 or 1). It is also concluded that nature of the SSP strongly depends on the value of the atomic volume Ω0 of alkali–alkali binary alloys. 相似文献
55.
56.
The structural and magnetic phase diagrams of Coa(1−x)MnaxGeb epitaxial films near the composition of Heusler alloy Co2MnGe have been studied using combinatorial molecular beam epitaxy techniques. Epitaxial growth on Ge (1 1 1) has been stabilized over nearly the entire composition range of the ternary system. Epitaxial constraints play an important role for the small number of observed structural phases. The variety of high-temperature magnetic properties, and the structural and chemical compatibilities with group IV elements make the ternary system promising for the science and applications of spintronics. 相似文献
57.
P. T. Jochym K. Parlinski A. M. Oleś 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):173-179
The magnetization distribution, its energetic characterization by the
interlayer coupling constants and lattice dynamics of (001)-oriented
Fe/Pt multilayers are investigated using density functional theory
combined with the direct method to determine phonon frequencies.
It is found that ferromagnetic order between consecutive Fe layers is
favoured, with the enhanced magnetic moments at the
interface. The bilinear and biquadratic coupling coefficients between Fe
layers are shown to saturate fast with increasing thickness of
nonmagnetic Pt layers which separate them. The phonon calculations
demonstrate a rather strong dependence of partial iron phonon
densities of states on the actual position of Fe monolayer
in the multilayer structure. 相似文献
58.
59.
稀土及杂质元素对ZA27合金晶间腐蚀的影响 总被引:10,自引:0,他引:10
为了从本质上了解杂质与稀土元素对锌铝合金晶间腐蚀的影响 ,探索抑制合金晶间腐蚀的有效途径 ,依据晶界的大角度重位点阵理论编制出相应计算机软件 ,建立含稀土、杂质及 η相颗粒的α相大角度晶界原子集团模型 ,采用递归法计算了α相晶界间的电荷转移 ,由此讨论了杂质 (Pb、Sn、Cd)及稀土元素 (La、Y)对Zn、Al电极电位的影响 .结果表明 ,杂质Pb、Sn、Cd增大原子间的电荷转移量 ,提高Zn、Al电极电位差 ,加速合金的腐蚀 ,稀土元素减小原子间的电荷转移量 ,降低Zn、Al电极电位差 ,具有抑制晶间腐蚀的作用 . 相似文献
60.
C. Liu Z.Y. Gao X. An M. Saunders H. Yang H.B. Wang L.X. Gao W. Cai 《Journal of magnetism and magnetic materials》2008
A Ni54Mn25.7Ga20.3 ferromagnetic shape memory alloy thin film has been fabricated by using the RF magnetron-sputtering technique. The structure and magnetic properties of the film were systematically investigated. The results show that the film is in ferromagnetic martensite state at room temperature with the Curie temperature (Tc) of about 370 K. The saturation magnetization (Ms) of the film reaches 45 emu/g at 300 K, which is about 80% as large as that of Ni–Mn–Ga bulk material. The magnetization hysteresis loops significantly depend on temperatures. The residual magnetization (Mr) and the coercive force (Hc) increase with decreasing temperatures. The grains homogeneously distribute in the film. The microstructure of the film consists of martensite plates. The interface between the martensite variants is clear and straight, indicating a good mobility. 相似文献