全文获取类型
收费全文 | 5087篇 |
免费 | 489篇 |
国内免费 | 680篇 |
专业分类
化学 | 1627篇 |
晶体学 | 27篇 |
力学 | 206篇 |
综合类 | 126篇 |
数学 | 3534篇 |
物理学 | 736篇 |
出版年
2024年 | 8篇 |
2023年 | 53篇 |
2022年 | 122篇 |
2021年 | 135篇 |
2020年 | 153篇 |
2019年 | 173篇 |
2018年 | 167篇 |
2017年 | 162篇 |
2016年 | 211篇 |
2015年 | 152篇 |
2014年 | 248篇 |
2013年 | 397篇 |
2012年 | 226篇 |
2011年 | 317篇 |
2010年 | 261篇 |
2009年 | 352篇 |
2008年 | 358篇 |
2007年 | 316篇 |
2006年 | 330篇 |
2005年 | 241篇 |
2004年 | 223篇 |
2003年 | 249篇 |
2002年 | 231篇 |
2001年 | 147篇 |
2000年 | 190篇 |
1999年 | 139篇 |
1998年 | 104篇 |
1997年 | 127篇 |
1996年 | 92篇 |
1995年 | 62篇 |
1994年 | 56篇 |
1993年 | 45篇 |
1992年 | 31篇 |
1991年 | 31篇 |
1990年 | 17篇 |
1989年 | 10篇 |
1988年 | 22篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 15篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1936年 | 3篇 |
排序方式: 共有6256条查询结果,搜索用时 15 毫秒
31.
S.P. Crane C. Bihler S.T.B. Goennenwein R. Ramesh 《Journal of magnetism and magnetic materials》2009,321(4):L5
Multifunctional thin film nanostructures containing soft magnetic materials such as nickel ferrite are interesting for potential applications in microwave signal processing because of the possibility to shrink the size of device architecture and limit device power consumption. An essential prerequisite to future applications of such a system is a firm understanding of its magnetic properties. We show that nanostructures composed of ferrimagnetic NiFe2O4 pillars in a multiferroic BiFeO3 matrix can be tuned magnetically by altering the aspect ratio of the pillars by depositing films of varying thickness. Magnetic anisotropy is studied using ferromagnetic resonance, which shows that the uniaxial magnetic anisotropy in the growth direction changes sign upon increasing the film thickness. The magnitude of this anisotropy contribution can be explained via a combination of shape and magnetostatic effects, using the object-oriented micromagnetic framework (OOMMF). The key factors determining the magnetic properties of the films are shown to be the aspect ratio of individual pillars and magnetostatic interactions between neighboring pillars. 相似文献
32.
Abstract The pulse-echo-overlap method was used to measure the longitudinal and transverse wave velocities in single-crystal (100) and (111) samples of InSb up to 3 GPa at room temperature. The peculiar variations of the elastic constants were observed near the covalent-metallic transition. 相似文献
33.
《Journal of Macromolecular Science: Physics》2013,52(3-4):753-760
We examined the free surface of a banded spherulite of poly (vinylidene fluoride) (PVDF) by atomic force microscopy. The directions of the slope of multilayer terraces of lamellar crystals are retained in each half of a banded spherulite; this evidence confirms the macroscopic selection of one-handedness in the formation of spiral terraces in each growth direction of the sheaf at the center of banded spherulite of PVDF. In a previous paper, it was confirmed that the three-dimensional morphology of all single crystals of PVDF grown from the melt is of chair-type, and hence, it is most probable that the stress in the chair crystal is responsible for the formation of spiral dislocations and terraces keeping the same handedness in each growth direction. The chair-type morphology is created because of the chain tilting to the fold surface, which can introduce symmetry breaking and, consequently, the selection of handedness in nonchiral polymers such as PVDF. 相似文献
34.
《Composite Interfaces》2013,20(5):451-466
Sheath-core type bicomponent fibers of polypropylene (PP) as a sheath component and thermotropic liquid crystalline polymer (TLCP) as a core component were prepared by the highspeed melt spinning process. Continuous fiber reinforced thermoplastic composites, in which TLCP acts as a reinforcing fiber and PP as a matrix polymer, were fabricated by the compression molding of these fibers. In the melt spinning, the attainable highest take-up velocity of TLCP was improved by co-processing with PP. Tensile modulus and strength of the TLCP component in the PP/TLCP bicomponent fibers increased with an increase in the take-up velocity. Comparison of wide-angle X-ray diffraction patterns of starting bicomponent fibers and fabricated composites indicated that the orientation relaxation of TLCP did not occur in the compression molding process. Accordingly, the tensile modulus and strength of the PP/TLCP composites were similar to those of the bicomponent fibers. Continuous fiber reinforced thermoplastic composites with various types of fiber content distributions were fabricated from the bicomponent fibers in which sheath-core composition was changed gradually in the spinning process. In the three-point bending test, the composites with two different types of symmetric structural gradients, one with higher TLCP fiber content near the surfaces than in the center and the other with higher TLCP content in the center than near the surfaces, exhibited different flexural moduli even though the overall TLCP contents were comparable. In the three-point bending test of a composite with asymmetric structural gradient, the yielding behavior and maximum flexural load varied depending on the direction of load application although the initial flexural moduli were similar. 相似文献
35.
A De Giorgi Type Result to Divergence Degenerate Elliptic Equation with Bounded Coefficients Related To Hörmander's Vector Fields 下载免费PDF全文
Lingling Hou 《偏微分方程(英文版)》2023,36(1):22-47
In this paper, we consider the divergence degenerate elliptic equation with bounded coefficients constructed by Hörmander's vector fields. We prove a De Giorgi type result, i.e., the local Hölder continuity for the weak solutions to the equation by providing a De Giorgi type lemma and extending the Moser iteration to the setting here. As a consequence, the Harnack inequality of weak solutions is also given. 相似文献
36.
《Indagationes Mathematicae》2023,34(5):1146-1180
Emden–Fowler type equations are nonlinear differential equations that appear in many fields such as mathematical physics, astrophysics and chemistry. In this paper, we perform an asymptotic analysis of a specific Emden–Fowler type equation that emerges in a queuing theory context as an approximation of voltages under a well-known power flow model. Thus, we place Emden–Fowler type equations in the context of electrical engineering. We derive properties of the continuous solution of this specific Emden–Fowler type equation and study the asymptotic behavior of its discrete analog. We conclude that the discrete analog has the same asymptotic behavior as the classical continuous Emden–Fowler type equation that we consider. 相似文献
37.
38.
The paper generalizes paraxial complex geometrical optics (PCGO) for Gaussian beam (GB) propagation in nonlinear media of Kerr type. Ordinary differential equations for the beam amplitude and for complex curvature of the wave front are derived, which describe the evolution of axially symmetric GB in a Kerr type nonlinear medium. It is shown that PCGO readily provides the solutions of NLS equation obtained earlier from diffraction theory on the basis of the aberration-free approach. Besides reproducing classical results of self-focusing PCGO readily describes an influence of the initial curvature of the wave front on the beam evolution in a medium of Kerr type including a nonlinear graded-index fiber. The range of applicability of the PCGO theory is discussed as well which is helpful for avoiding nonphysical solutions. 相似文献
39.
We consider the short-time heat content asymptotics for oblique boundary conditions. The first few coefficients in the asymptotic expansion are calculated. 相似文献
40.