全文获取类型
收费全文 | 876篇 |
免费 | 223篇 |
国内免费 | 107篇 |
专业分类
化学 | 106篇 |
晶体学 | 7篇 |
力学 | 82篇 |
综合类 | 6篇 |
数学 | 98篇 |
物理学 | 907篇 |
出版年
2024年 | 6篇 |
2023年 | 5篇 |
2022年 | 23篇 |
2021年 | 21篇 |
2020年 | 24篇 |
2019年 | 22篇 |
2018年 | 29篇 |
2017年 | 33篇 |
2016年 | 26篇 |
2015年 | 34篇 |
2014年 | 49篇 |
2013年 | 67篇 |
2012年 | 59篇 |
2011年 | 60篇 |
2010年 | 42篇 |
2009年 | 60篇 |
2008年 | 54篇 |
2007年 | 50篇 |
2006年 | 53篇 |
2005年 | 47篇 |
2004年 | 66篇 |
2003年 | 38篇 |
2002年 | 54篇 |
2001年 | 53篇 |
2000年 | 36篇 |
1999年 | 28篇 |
1998年 | 30篇 |
1997年 | 25篇 |
1996年 | 23篇 |
1995年 | 18篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 9篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1970年 | 2篇 |
排序方式: 共有1206条查询结果,搜索用时 390 毫秒
111.
112.
激光等离子体能量角分布及吸收定标律 总被引:1,自引:0,他引:1
主要研究激光平面靶等离子体发射能量角分布及吸收定标律。实验利用高斯型1.06μm激光脉冲,其能量为2~50J,脉冲宽度为0.3~2.2ns,靶面平均辐照强度为1.8×1013~1.1x10~(15)W/cm~2,光束以25°角入射。实验采用了Au、Ag、Ti、Al和C_8H_8等厚靶。用等离子体卡计测量靶面吸收的激光能量。用指数函数拟合实验数据,给出了吸收效率分别作为激光强度、脉冲宽度和靶材料原子序数的函数的定标关系式。这些关系式定性地与逆轫致吸收的理论关系式相一致。 相似文献
113.
Francesco Chiadini Antonio Scaglione Gaetano Panariello 《Optical and Quantum Electronics》2004,36(11):981-995
A numerical method for calculating cutoff frequencies of modes of weakly guiding optical fibers is described. Starting from a properly constructed field representation, the method follows a variational approach to obtain an eigenvalue problem for the cutoff frequencies which can be easily solved by a standard numerical routine. The field representation uses an expansion in terms of the Laguerre–Gauss functions in the fiber core and limiting form for small arguments of modified Bessel functions in the fiber cladding. Fibers with power-law refractive index profiles and fibers with a profile showing a dip on the axis are analyzed. Results obtained for modes of arbitrary order (both azimuthal and radial) show that our method is very efficient and accurate. 相似文献
114.
The differential cross-sections for the emission of M shell fluorescent X-rays from Th by 5·95 keV photons at eight angles
ranging from 50° to 120° have been measured. The differential cross-section is found to decrease with increase in the emission
angle showing anisotropic spatial distribution of M shell fluorescent X-rays. The present results contradict the predictions
of the calculations of Cooper and Zare [1] that the atomic inner shell vacancy states produced in photoionization are not
aligned but confirm those of Fluggeet al [2] and Scofield [3] that the vacancy states withJ > 1/2 are aligned. The integral M shell fluorescent emission cross sections have been determined from the measured angular
distribution coefficients and compared with theoretical integral cross-sections calculated by using theoretical values of
M subshell photoionization cross-sections, fluorescence yields and coster kronig transition probabilities available in literature.
The experimental and theoretical values of integral crosssections show a reasonable agreement. 相似文献
115.
Viraht Sahni 《International journal of quantum chemistry》2004,97(6):953-960
116.
117.
We obtain sufficient conditions for the set of roots of an entire function of order zero of strongly regular growth to possess an angular density. 相似文献
118.
A method for determination of the orientation distribution function of anisotropic paramagnetic species from the angular dependence of the ESR spectra based on simulation of the spectra was developed. The orientation distribution function is represented as a sum of orthonormal functions. The weight coefficients are determined by minimizing the deviations of the theoretical spectra from experimental ones. The method was numerically tested. The method is relatively insensitive to the presence of noise and foreign ESR signals not related to the sample orientation in the magnetic field.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2595–2601, December, 2004. 相似文献
119.
We propose a detailed method for the symmetrization of the standard O(3) or SU(2)⊗CI basis |jτ,m〉 (τ=g or u) into the Oh or Td point group. This is realized by means of an orientation matrix called G. The oriented basis obtained in this way allows matrix element calculations for rovibronic spectroscopic problems concerning octahedral or tetrahedral molecules. Particular attention has been put on careful phase choices. A numerical calculation of all the G matrix elements for both integer and half-integer j values up to 399/2 has been performed. Such high angular momentum values are necessary for the case of heavy molecules with high rotational excitation. To calculate the G coefficients with high precision at high j values we pre-calculated the necessary Wigner functions using symbolic MAPLE software and made then the numerical calculations with quadruple precision. The complete list of these coefficients can be obtained freely at the URL: http://www.u-bourgogne.fr/LPUB/group.html. As an illustration, we also present briefly an application to two typical spectroscopic calculations: the pure rotational levels of SF6 in its ground vibrational state and the ν3 band of ReF6 (an open-shell molecule with an odd number of electrons and a fourfold degenerate electronic ground state). 相似文献
120.
André Martin 《Journal of statistical physics》1994,76(1-2):497-504
We submit to the community of physicists and mathematical physicists the following problem: prove that the ground-state energy of a system ofN particles without spin, without statistics, and interacting by central forces increases with angular momentum. For two particles, this is obvious. For more than two we give a number of arguments which support our conjecture. 相似文献