全文获取类型
收费全文 | 6258篇 |
免费 | 934篇 |
国内免费 | 655篇 |
专业分类
化学 | 2018篇 |
晶体学 | 144篇 |
力学 | 1313篇 |
综合类 | 106篇 |
数学 | 1281篇 |
物理学 | 2985篇 |
出版年
2024年 | 14篇 |
2023年 | 60篇 |
2022年 | 100篇 |
2021年 | 147篇 |
2020年 | 127篇 |
2019年 | 125篇 |
2018年 | 118篇 |
2017年 | 190篇 |
2016年 | 252篇 |
2015年 | 179篇 |
2014年 | 305篇 |
2013年 | 450篇 |
2012年 | 359篇 |
2011年 | 441篇 |
2010年 | 371篇 |
2009年 | 406篇 |
2008年 | 410篇 |
2007年 | 456篇 |
2006年 | 385篇 |
2005年 | 395篇 |
2004年 | 318篇 |
2003年 | 307篇 |
2002年 | 272篇 |
2001年 | 214篇 |
2000年 | 203篇 |
1999年 | 189篇 |
1998年 | 147篇 |
1997年 | 134篇 |
1996年 | 84篇 |
1995年 | 95篇 |
1994年 | 90篇 |
1993年 | 81篇 |
1992年 | 57篇 |
1991年 | 52篇 |
1990年 | 39篇 |
1989年 | 31篇 |
1988年 | 27篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 12篇 |
1982年 | 30篇 |
1981年 | 14篇 |
1980年 | 20篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 11篇 |
1974年 | 4篇 |
排序方式: 共有7847条查询结果,搜索用时 15 毫秒
91.
研究一维半导体在外电磁场中的光吸收、涉及电子带间的直接跃迁与间接跃迁,考虑了电子-空穴相互作用的激子光吸收,导出一维半导体的光吸收系数公式。 相似文献
92.
93.
Francesca Aicardi 《Functional Analysis and Other Mathematics》2006,1(2):93-109
We give a recursive method for building X
p
(a,b) for each prime p. Arnold’s triangle is composed of positive integers: for a>1 and 0<b<a, X
p
(a,b) is the degree of the highest power of p dividing the difference of the binomial coefficients C
pa
pb
−C
a
b
.
相似文献
94.
Tim R. Dargaville Julie M. Elliott Mathew Celina 《Journal of Polymer Science.Polymer Physics》2006,44(22):3253-3264
Films of piezoelectric PVDF and P(VDF‐TrFE) were exposed to vacuum UV (115–300 nm VUV) and γ‐radiation to investigate how these two forms of radiation affect the chemical, morphological, and piezoelectric properties of the polymers. The extent of crosslinking was almost identical in both polymers after γ‐irradiation, but surprisingly, was significantly higher for the TrFE copolymer after VUV‐irradiation. Changes in the melting behavior were also more significant in the TrFE copolymer after VUV‐irradiation due to both surface and bulk crosslinking, compared with only surface crosslinking for the PVDF films. The piezoelectric properties (measured using d33 piezoelectric coefficients and D‐E hysteresis loops) were unchanged in the PVDF homopolymer, while the TrFE copolymer exhibited more narrow D‐E loops after exposure to either γ‐ or VUV‐radiation. The more severe damage to the TrFE copolymer in comparison with the PVDF homopolymer after VUV‐irradiation is explained by different energy deposition characteristics. The short wavelength, highly energetic photons are undoubtedly absorbed in the surface layers of both polymers, and we propose that while the longer wavelength components of the VUV‐radiation are absorbed by the bulk of the TrFE copolymer causing crosslinking, they are transmitted harmlessly in the PVDF homopolymer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3253–3264, 2006 相似文献
95.
In the present work, ferrites with compositions of (Ni0.27Zn0.64Cux)Fe1.98O4 (x=0.1, 0.2) were prepared by conventional ceramic methods. The relationship between the microstructure and the temperature dependence of relative initial permeability was investigated. It was found that intergranular pores in the ferrites generate large demagnetizing fields, reducing the temperature dependence of the effective anisotropy field Heff, and decreasing the temperature dependence of the relative initial permeability accordingly. However, intragranular pores pin the movement of domain walls. Compared with the permeability induced by domain wall motion, the permeability that resulted from the spin rotation is more sensitive to temperature. As a result, the relative initial permeability of ferrites becomes more sensitive to temperature with increasing micropores within grains. 相似文献
96.
This article will combine the finite element method, the interpolated coefftcient finite element method, the eigenfunction expansion method, and the search-extension method to obtain the multiple solutions for semilinear elliptic equations. This strategy not only grently reduces the expensive computation, but also is successfully implemented to obtain multiple solutions for a class of semilinear elliptic boundary value problems with non-odd nonlinearity on some convex or nonconvex domains. Numerical solutions illustrated by their graphics for visualization will show the efficiency of the approach. 相似文献
97.
用力敏传感器测量液体表面张力系数 总被引:17,自引:3,他引:14
利用力敏传感器测量液体表面张力系数,既改进了传统的实验方法和仪器,提高了实验的准确度和稳定性,同时因实现了非电量电测,也有助于测量过程中学生对物理过程的观察和规律的理解。 相似文献
98.
Seppo Hassi Manfred Mö ller Henk de Snoo 《Proceedings of the American Mathematical Society》2006,134(10):2885-2893
The class of Nevanlinna functions consists of functions which are holomorphic off the real axis, which are symmetric with respect to the real axis, and whose imaginary part is nonnegative in the upper halfplane. The Kac subclass of Nevanlinna functions is defined by an integrability condition on the imaginary part. In this note a further subclass of these Kac functions is introduced. It involves an integrability condition on the modulus of the Nevanlinna functions (instead of the imaginary part). The characteristic properties of this class are investigated. The definition of the new class is motivated by the fact that the Titchmarsh-Weyl coefficients of various classes of Sturm-Liouville problems (under mild conditions on the coefficients) actually belong to this class.
99.
100.
分布耦合系数对线性啁啾光栅色散的影响 总被引:7,自引:1,他引:6
本文从光栅反向耦合波方程出发,经相位共轭变换用Runge-Kuta-Gil方法对其数值求解。针对线性啁啾光栅耦合系数变化服从不同的分布,分析了各种分布对光栅反射谱特性和色散特性的影响。 相似文献