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   2659篇
  免费   400篇
  国内免费   158篇
化学   325篇
晶体学   6篇
力学   241篇
综合类   39篇
数学   1282篇
物理学   1324篇
  2023年   19篇
  2022年   43篇
  2021年   56篇
  2020年   62篇
  2019年   57篇
  2018年   75篇
  2017年   70篇
  2016年   72篇
  2015年   73篇
  2014年   123篇
  2013年   220篇
  2012年   148篇
  2011年   150篇
  2010年   134篇
  2009年   177篇
  2008年   188篇
  2007年   165篇
  2006年   154篇
  2005年   138篇
  2004年   106篇
  2003年   108篇
  2002年   114篇
  2001年   80篇
  2000年   89篇
  1999年   80篇
  1998年   50篇
  1997年   63篇
  1996年   48篇
  1995年   35篇
  1994年   28篇
  1993年   32篇
  1992年   34篇
  1991年   33篇
  1990年   36篇
  1989年   21篇
  1988年   22篇
  1987年   30篇
  1986年   13篇
  1985年   9篇
  1984年   10篇
  1983年   6篇
  1982年   3篇
  1981年   8篇
  1980年   6篇
  1979年   7篇
  1978年   6篇
  1977年   3篇
  1976年   3篇
  1973年   2篇
  1971年   3篇
排序方式: 共有3217条查询结果,搜索用时 15 毫秒
931.
用类比推理的方法讨论了多元混合理想气体有关的物理量和方程,给出了一些有意义的结果.  相似文献   
932.
M.Konno 《中国物理 C》2007,31(12):1130-1132
Particle type dependences of hadron yield and emission patterns, especially its difference between mesons and baryons, at intermediate pT(2—5GeV/c) is one of the findings in heavy ion collisions at RHIC. A systematic study of identified hadron production was performed in Au+Au/Cu+Cu collisions at sNN=62.4/200GeV, to investigate the possible origins of this difference. In this paper, we show particle ratios, elliptic flow strengths, and their scaling properties.  相似文献   
933.
The absorption profile of the N = 1− fine structure line of oxygen was recorded by a resonator spectrometer at a frequency range of 110-130 GHz at atmospheric pressure and different temperatures ranging from −21 °C up to +22 °C. Analysis of the observed line shape allowed determination of the temperature dependence of the line pressure broadening. The measured value of the temperature exponent is n = 0.74(5) for self-broadening. Consistency of the measurements is supported by simultaneous measurements of the line intensity, the line mixing parameter and the line center frequency, and by comparison of obtained values with previously known data.  相似文献   
934.
The transmission properties of one-dimensional photonic crystals containing double-negative and singlenegative materials are studied theoretically.A special kind of photonic band gap is found in this structure.This gap is invariant with scaling and insensitive to thickness fluctuation.But when changing the ratio of the thickness of two media.the width of the gap could be enlarged.The defect modes are analyzed by inducing a linear defect layer in the structure.It is found that the number of defect modes will increase when the thickness of the defect layer becomes larger.  相似文献   
935.
The extension of ordinary Fourier transform to the fractional Fourier transform (FRFT) was first accomplished by Namias in 1980. He gave a complete mathematical definition and discussed the eigenfunction of the transform. Using a system of lenses Lohmann et al.[1] first successfully realized the FRFT optically and designed the single lens mode and double lens mode for the realization of the FRFT of continuously variable fractional order. The concept of fractals was first proposed by Man…  相似文献   
936.
This paper consists of two parts. First we set up a general scheme of local traps in a homogeneous deterministic quantum system. The current of particles caught by the trap is linked to the dynamical behaviour of the trap states. In this way, transport properties in a homogeneous system are related to spectral properties of a coherent dynamics. Next we apply the scheme to a system of Fermions in the one-particle approximation. We obtain in particular lower bounds for the dynamical entropy in terms of the current induced by the trap.  相似文献   
937.
Consider a system of particles which move in Rd according to a symmetric α-stable motion, have a lifetime distribution of finite mean, and branch with an offspring law of index 1+β. In case of the critical dimension d=α/β the phenomenon of multi-scale clustering occurs. This is expressed in an fdd scaling limit theorem, where initially we start with an increasing localized population or with an increasing homogeneous Poissonian population. The limit state is uniform, but its intensity varies in line with the scaling index according to a continuous-state branching process of index 1+β. Our result generalizes the case α=2 of Brownian particles of Klenke (1998), where p.d.e. methods had been used which are not available in the present setting. Supported in part by the DFG. Supported in part by the grants RFBR 02-01-00266 and Russian Scientific School 1758.2003.1.  相似文献   
938.
We characterize the scaling functions of a multiresolution analysis in a general context, where instead of the dyadic dilation one considers the dilation given by a fixed linear map such that and all (complex) eigenvalues of have absolute value greater than In the general case the conditions depend on the map We identify some maps for which the obtained condition is equivalent to the dyadic case, i.e., when is a diagonal matrix with all numbers in the diagonal equal to There are also easy examples of expanding maps for which the obtained condition is not compatible with the dyadic case. The complete characterization of the maps for which the obtained conditions are equivalent is out of the scope of the present note.

  相似文献   

939.
For a linear autonomous difference equation with a unique real eigenvalue  , it is shown that for every solution  the ratio of and the eigensolution corresponding to  is Cesàro summable to a limit which can be expressed in terms of the initial data. As a consequence, for most solutions the Lyapunov characteristic exponent is equal to  . The proof is based on a Tauberian theorem for the Laplace transform.

  相似文献   

940.
The quartic force field of pyrazine has been calculated in the B3LYP/6-31G(d) hybrid density-functional approximation. Based on the results of this calculation, the total IR (250–3800 cm–1) and Raman (400–3200 cm–1) spectra of pyrazine have been interpreted with consideration for the Fermi and Darling-Dennison resonances and their spectral manifestations. A precision method is proposed for anharmonic analysis of the vibrational states of polyatomic molecules on the basis of consideration of their theoretical anharmonicity constants in combination with the corresponding experimental frequencies. The method of linear scaling of frequencies has been theoretically substantiated.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 13–22, January–February, 2005.  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