全文获取类型
收费全文 | 8114篇 |
免费 | 1150篇 |
国内免费 | 834篇 |
专业分类
化学 | 2153篇 |
晶体学 | 87篇 |
力学 | 841篇 |
综合类 | 108篇 |
数学 | 1408篇 |
物理学 | 3138篇 |
无线电 | 2363篇 |
出版年
2024年 | 20篇 |
2023年 | 86篇 |
2022年 | 141篇 |
2021年 | 172篇 |
2020年 | 176篇 |
2019年 | 174篇 |
2018年 | 154篇 |
2017年 | 243篇 |
2016年 | 310篇 |
2015年 | 287篇 |
2014年 | 418篇 |
2013年 | 577篇 |
2012年 | 506篇 |
2011年 | 594篇 |
2010年 | 494篇 |
2009年 | 522篇 |
2008年 | 581篇 |
2007年 | 625篇 |
2006年 | 531篇 |
2005年 | 482篇 |
2004年 | 390篇 |
2003年 | 360篇 |
2002年 | 315篇 |
2001年 | 234篇 |
2000年 | 250篇 |
1999年 | 206篇 |
1998年 | 161篇 |
1997年 | 144篇 |
1996年 | 121篇 |
1995年 | 118篇 |
1994年 | 123篇 |
1993年 | 101篇 |
1992年 | 69篇 |
1991年 | 71篇 |
1990年 | 50篇 |
1989年 | 35篇 |
1988年 | 34篇 |
1987年 | 19篇 |
1986年 | 23篇 |
1985年 | 26篇 |
1984年 | 22篇 |
1983年 | 8篇 |
1982年 | 28篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1979年 | 10篇 |
1978年 | 12篇 |
1977年 | 5篇 |
1976年 | 14篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Solc型双折射滤波器离轴消光比的研究 总被引:3,自引:0,他引:3
提出了一种Solc型双折射滤波器的离轴消光比的一般性计算方法,利用所得结果模拟出了Solc型双折射滤波器的锥光干涉图以及发散光积分消光比与波长和发散角的关系曲线,实验结果证实了理论推算的合理性,此外本方法也适用于计算各种类型双折射滤波器的离轴消光比。 相似文献
92.
Na SUN 《数学学报(英文版)》2007,23(10):1909-1914
In this paper, we introduce an operator Hμ(z) on L^∞(△) and obtain some of its properties. Some applications of this operator to the extremal problem of quasiconformal mappings are given. In particular, a sufficient condition for a point r in the universal Teichmfiller space T(△) to be a Strebel point is obtained. 相似文献
93.
Conductive composite films of poly(styrene‐co‐n‐butylacrylate) copolymers filled with low‐density, Ni‐plated core‐shell polymeric particles were prepared and their behaviors of positive temperature coefficient of resistance (PTCR) were investigated. When the conductive fillers in the composite film were loaded beyond the critical volume, 10 up to 25 vol %, composite films exhibited a unique electrical resistant transition behavior, which the electrical resistance rapidly increased by several orders of magnitude at the critical temperature. The PTCR transition temperature, in general, occurred before the glass transition temperature of polymer matrix. Further increased the conductive filler loading to 30 vol %, the overpacked conduction paths were formed in the entire composite and the PTCR effects became blurred. While the composite film treated with thermal cycle several times from room temperature up to 120 °C, the electrical resistivity increased accompanied with the shift of the PTCR transition to lower temperature. The reason might have been caused by the formed interfacial cracks within the composite film. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 322–329, 2007 相似文献
94.
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
95.
96.
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
97.
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
98.
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
99.
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.
100.