首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1049篇
  免费   80篇
  国内免费   57篇
化学   193篇
晶体学   4篇
力学   63篇
综合类   15篇
数学   514篇
物理学   397篇
  2024年   2篇
  2023年   5篇
  2022年   10篇
  2021年   15篇
  2020年   17篇
  2019年   27篇
  2018年   20篇
  2017年   20篇
  2016年   28篇
  2015年   18篇
  2014年   42篇
  2013年   64篇
  2012年   44篇
  2011年   49篇
  2010年   46篇
  2009年   47篇
  2008年   61篇
  2007年   86篇
  2006年   71篇
  2005年   53篇
  2004年   59篇
  2003年   46篇
  2002年   53篇
  2001年   41篇
  2000年   47篇
  1999年   29篇
  1998年   35篇
  1997年   27篇
  1996年   16篇
  1995年   15篇
  1994年   16篇
  1993年   11篇
  1992年   11篇
  1991年   7篇
  1990年   7篇
  1989年   2篇
  1988年   4篇
  1987年   3篇
  1986年   2篇
  1985年   2篇
  1984年   5篇
  1983年   3篇
  1982年   3篇
  1980年   3篇
  1979年   2篇
  1978年   4篇
  1976年   2篇
  1971年   1篇
  1969年   1篇
  1959年   1篇
排序方式: 共有1186条查询结果,搜索用时 515 毫秒
31.
The main purpose of this paper is to present accurate infrared integrated intensities of liquid toluene, C6H5CH3, at 25 °C. Also presented are the decadic molar absorption coefficients, Em, the real and imaginary dielectric constants, ε′ and ε″, and the real and imaginary molar polarizabilities, m and m. Integrated intensities were determined as Cj, the area under bands in the spectrum, for all bands between 4800 and 440 cm−1. The contributions from the different bands were separated by fitting the spectrum with classical damped harmonic oscillator bands. The uncertainties in the integrated intensities of most bands are estimated to be 5–10%, with the uncertainties in very weak bands and in shoulders possibly up to 100%. The intensity that should be assigned to the fundamentals is more difficult to estimate due to Fermi resonance with overtone and combination bands, and a best estimate is given. The integrated intensities of the fundamental vibrations and the corresponding transition dipole moments are summarized and are compared with literature values for the gas.  相似文献   
32.
33.
使用凝血四项指标诊断凝血功能是临床的常规检查,但根据经验进行诊断正确率不高.剔除临床上最重要的指标FIB后,建立支持向量机模型诊断的正确率和根据凝血四项指标诊断的正确率没有显著差异,100次模拟的平均正确率分别达到了95.4496%和95.5039%.  相似文献   
34.
在非线性Black-Scholes模型下,研究了算术平均亚式期权定价问题.首先利用单参数摄动方法,将亚式期权适合的偏微分方程分解成一系列常系数抛物方程.其次通过计算这些常系数抛物型方程的解,给出了算术平均亚式期权的近似定价公式.最后分析了近似结论的误差估计,并通过数值算例验证了所得近似结论的合理性.  相似文献   
35.
36.
The temperature dependence of Bragg intensities in C60 is discussed for the simple cubic Pa3 phase occurring below 260 K. It is shown that, generally, the intensities of Bragg reflections may be surprisingly strongly affected even by seemingly minor variations of certain parameters. Among these the most important are the respective molecular orientational angles of the so-called pentagon and hexagon orientations, the fractions of molecules adopting these orientations and the lattice parameter. Correct determination of the Debye-Waller factor is found to be unusually difficult because of this behaviour. Numerical calculations are used to provide explicit examples and lead to the conclusion that the evaluation of Bragg intensities in this system requires considerable care.  相似文献   
37.
The calculation of relative intensities of the optical absorption lines of the fourth order pair of Cr3+ ions in ruby has been performed assuming the electro-dipole character of the transitions.  相似文献   
38.
39.
In a recent article, Y. Liu, X. Cheng, H. Cheng, J. Cheng and X. Song [Mol. Phys., 114:19, 2817–2823] report on the calculation of potential energy curves and the derivation of spectroscopic constants and line intensities for the lowest energy electronic states of HCl+. There are several shortcomings in the article; the most notable being the incorrect ordering of the 2П3/2 and 2П1/2 state energies, erroneous selection rules, which lead to the absence of a Q-branch in their predicted spectra, incorrect Höln–London factors, and a missing appendix.  相似文献   
40.
Yu and Oh (eprint) [1] have given a state-independent proof of the Kochen-Specker theorem in three dimensions using only 13 rays. The proof consists of showing that a non-contextual hidden variable theory necessarily leads to an inequality that is violated by quantum mechanics. We give a similar proof making use of 21 rays that constitute a SIC (symmetric informationally-complete positive operator-valued measure) and a complete set of MUB (mutually unbiased bases). A theory-independent inequality is also presented using the same 21 rays, as required for experimental tests of contextuality.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号