全文获取类型
收费全文 | 3757篇 |
免费 | 252篇 |
国内免费 | 343篇 |
专业分类
化学 | 640篇 |
晶体学 | 9篇 |
力学 | 907篇 |
综合类 | 64篇 |
数学 | 1837篇 |
物理学 | 895篇 |
出版年
2024年 | 7篇 |
2023年 | 50篇 |
2022年 | 68篇 |
2021年 | 89篇 |
2020年 | 107篇 |
2019年 | 86篇 |
2018年 | 117篇 |
2017年 | 124篇 |
2016年 | 118篇 |
2015年 | 121篇 |
2014年 | 176篇 |
2013年 | 532篇 |
2012年 | 141篇 |
2011年 | 180篇 |
2010年 | 127篇 |
2009年 | 203篇 |
2008年 | 191篇 |
2007年 | 171篇 |
2006年 | 223篇 |
2005年 | 148篇 |
2004年 | 164篇 |
2003年 | 144篇 |
2002年 | 142篇 |
2001年 | 125篇 |
2000年 | 118篇 |
1999年 | 125篇 |
1998年 | 83篇 |
1997年 | 110篇 |
1996年 | 64篇 |
1995年 | 53篇 |
1994年 | 45篇 |
1993年 | 36篇 |
1992年 | 22篇 |
1991年 | 25篇 |
1990年 | 19篇 |
1989年 | 16篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有4352条查询结果,搜索用时 15 毫秒
1.
《Journal of Pure and Applied Algebra》2022,226(8):107024
We solve a combinatorial question concerning eigenvalues of the universal intertwining endomorphism of a subset representation. 相似文献
2.
3.
Knowledge of the vibrational properties of nanoparticles is of fundamental interest since it is a signature of their morphology, and it can be utilized to characterize their physical properties. In addition, the vibration characteristics of the nanoparticles coupled with surrounding media and subjected to magnetic field are of recent interest. This paper develops an analytical approach to study the radial breathing-mode frequency of elastically confined spherical nanoparticles subjected to magnetic field. Based on Maxwell's equations, the nonlocal differential equation of radial motion is derived in terms of radial displacement and Lorentz's force. Bessel functions are used to obtain a frequency equation. The model is justified by a good agreement between the results given by the present model and available experimental and atomic simulation data. Furthermore, the model is used to elucidate the effect of nanoparticle size, the magnetic field and the stiffness of the elastic medium on the radial breathing-mode frequencies of several nanoparticles. Our results reveal that the effects of the magnetic field and the elastic medium are significant for nanoparticle with small size. 相似文献
4.
L. Tong Y. Tian Q. Y. Wang Y. S. Ling 《International Journal of Infrared and Millimeter Waves》2006,27(9):1307-1314
The paper introduces a special system calibration technology in s-parameters measurement of microwave and millimeter wave
devices. The 8-term errors module is built by analyzing the signals flowing in the measurement system. Then the calibration
technology using non-standard kits is designed on the base. Finally, the experiment using the calibration technology is introduced. 相似文献
5.
Stefan Nörtemann 《Applied Categorical Structures》2002,10(4):417-429
The Hahn–Banach Theorem for partially ordered totally convex modules [3] and a necessary and sufficient condition for the existence of an extension of a morphism from a submodule C
0 of a partially ordered totally convex module C (with the ordered unit ball of the reals as codomain) to C, are proved. Moreover, the categories of partially ordered positively convex and superconvex modules are introduced and for both categories the Hahn–Banach Theorem is proved. 相似文献
6.
设R是环,M是R-拟连续左R-模.如果R关于形如l(m),m∈M的左理想满足升链条件,则M可写成一致子模的直和. 相似文献
7.
贝克曼Allegra^TM 21R型超高速离心机开机后,操作面板上出现错误代码“28”,离心机不旋转。离心机的电机采用无刷感应驱动,由电机驱动电源模块BSMl0GD60DN2驱动离心机的电机。故障是由于电源模块BSMl0GD60DN2损坏引起的。采用东芝三相桥式IGBT电源模块MG25Q6ES42代替BSMl0GD60DN2,并更换已烧毁的栅极电阻后。开机试验,仪器恢复正常。 相似文献
8.
马歇尔-勒纳条件的实证研究 总被引:6,自引:0,他引:6
本文从人民币实际汇率变动是否会对我国贸易收支产生影响出发,基于马歇尔.勒纳条件,对计算贸易弹性常用的OLS回归模型进行了改进,建立了向量自回归误差修正模型来估算我国的国际贸易弹性。实证研究表明:我国进出口需求的价格弹性之和大于1。因此人民币贬值可改善贸易收支;反之升值将使贸易收支恶化。 相似文献
9.
We consider the plane-strain buckling of a cylindrical shellof arbitrary thickness which is made of a Varga material andis subjected to an external hydrostatic pressure on its outersurface. The WKB method is used to solve the eigenvalue problemthat results from the linear bifurcation analysis. We show thatthe circular cross-section buckles into a non-circular shapeat a value of µ1 which depends on A1/A2 and a mode number,where A1 and A2 are the undeformed inner and outer radii, andµ1 is the ratio of the deformed inner radius to A1. Inthe large mode number limit, we find that the dependence ofµ1 on A1/A2 has a boundary layer structure: it is constantover almost the entire region of 0 < A1/A2 < 1 and decreasessharply from this constant value to unity as A1/A2 tends tounity. Our asymptotic results for A1 1 = O(1) and A1 1 = O(1/n) are shown to agree with the numerical resultsobtained by using the compound matrix method. 相似文献
10.