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   6613篇
  免费   1129篇
  国内免费   656篇
化学   1422篇
晶体学   79篇
力学   696篇
综合类   105篇
数学   1330篇
物理学   2223篇
无线电   2543篇
  2024年   22篇
  2023年   74篇
  2022年   131篇
  2021年   143篇
  2020年   190篇
  2019年   146篇
  2018年   156篇
  2017年   240篇
  2016年   265篇
  2015年   265篇
  2014年   370篇
  2013年   568篇
  2012年   436篇
  2011年   500篇
  2010年   392篇
  2009年   434篇
  2008年   421篇
  2007年   445篇
  2006年   398篇
  2005年   319篇
  2004年   320篇
  2003年   304篇
  2002年   266篇
  2001年   193篇
  2000年   187篇
  1999年   181篇
  1998年   149篇
  1997年   104篇
  1996年   123篇
  1995年   103篇
  1994年   95篇
  1993年   81篇
  1992年   55篇
  1991年   49篇
  1990年   42篇
  1989年   37篇
  1988年   27篇
  1987年   26篇
  1986年   16篇
  1985年   23篇
  1984年   16篇
  1983年   9篇
  1982年   15篇
  1981年   9篇
  1980年   8篇
  1979年   11篇
  1978年   6篇
  1977年   6篇
  1976年   10篇
  1957年   3篇
排序方式: 共有8398条查询结果,搜索用时 15 毫秒
11.
本文提出生种新的带限信号的外推方法,该方法能够很好地抑制噪声干扰,且计算复杂性较低,本文给出算法,证明了收敛性,最后给出了误差计算机实验结果。  相似文献   
12.
A singularly perturbed parabolic equation with a nonlinear right-hand side of a special form is examined. A numerical analytical study of such equations is performed.  相似文献   
13.
The characteristic exponent α of a Lévy-stable law S α (σ, β, μ) was thoroughly studied as the extreme value index of a heavy tailed distribution. For 1 < α < 2, Peng (Statist. Probab. Lett. 52: 255–264, 2001) has proposed, via the extreme value approach, an asymptotically normal estimator for the location parameter μ. In this paper, we derive by the same approach, an estimator for the scale parameter σ and we discuss its limiting behavior.   相似文献   
14.
The general problem of finding a distribution in hyperfine interaction parameters from experimental Mössbauer spectra is outlined. Existing methods may lack flexibility to be easily applicable to simple problems. A line shape for hyperfine parameter distributions is given, which is based on linear segments in the probability function. This method is applied in the analysis of samples containing iron in a silicate glass.  相似文献   
15.
In this paper, the possibility of using the gradients of the temperature and of the internal parameters as additional state variables in Continuum Thermodynamics is considered. The expressions of the two principles are discussed and Clausius–Duhem inequality is derived under an appropriate statement of the internal entropy production. Several formulations are proposed and compared to existing results in the literature. To cite this article: P. Ireman, Q.S. Nguyen, C. R. Mecanique 332 (2004).  相似文献   
16.
A detailed study of the generalized M2 factor of hard-edged diffracted beams based on the truncated second-order moments method, asymptotic analysis and self-convergent beam width approach is performed. The dependence of the generalized M2 factor on the parameters characterizing the spatial profile, and beam truncation, etc. is analyzed.  相似文献   
17.
18.
Summary The solubility parameters of cationic surfactants were obtained using the inverse gas chromatographic technique. The surfactants didodecyl dimethyl ammonium bromide, dioctadecyl dimethyl ammonium bromide and dodecyl pyridinium chloride were used as stationary phase and retention data of different probe solutes were measured at different temperatures. The results were analysed by the combination of Flory-Huggins and Hildebrand theories, and the solubility parameters of the surfactants were obtained in a range of temperatures between 80–120°C.  相似文献   
19.
R. Hedjar  M. Bounkhel  L. Tadj 《TOP》2004,12(1):193-208
In this paper a predictive control strategy is applied to a periodic-review dynamic inventory system with deteriorating items. Given the current inventory level, we determine the optimal production rates to be implemented at the beginning of each of the following periods over the control horizon. The effectiveness of this approach is the use of future information of the inventory target level and the desired production rate, which are available, along the fixed horizon. The deterioration coefficient may be known or unknown and both cases are considered. In the case where it is unknown, the self-tuning predictive control is applied. The proposed control algorithms are illustrated by simulations.  相似文献   
20.
The influence of the parameter of amplitude-phase coupling for nonlinear amplification on the phase-frequency characteristics of an injection laser in the regime of pumping current modulation has been investigated theoretically. The parameter is defined as the coefficient of proportionality between changes in the real and imaginary parts of the refractive index during variation of the density of photons in the cavity. The substantial dependence of the coefficient of phase modulation on the parameter of the amplitude-phase coupling for nonlinear amplification at small modulation frequencies is shown. A technique to determine the indicated parameter based on the frequency dependence of the ratio between the coefficients of phase and amplitude modulation is suggested.  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