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   47697篇
  免费   1292篇
  国内免费   13篇
化学   28585篇
晶体学   254篇
力学   787篇
综合类   1篇
数学   8905篇
物理学   10470篇
  2023年   334篇
  2022年   293篇
  2021年   489篇
  2020年   695篇
  2019年   636篇
  2018年   1005篇
  2017年   934篇
  2016年   1751篇
  2015年   1409篇
  2014年   1403篇
  2013年   3126篇
  2012年   2942篇
  2011年   2773篇
  2010年   1871篇
  2009年   1563篇
  2008年   2432篇
  2007年   2199篇
  2006年   1969篇
  2005年   2010篇
  2004年   1730篇
  2003年   1440篇
  2002年   1253篇
  2001年   966篇
  2000年   980篇
  1999年   691篇
  1998年   536篇
  1997年   464篇
  1996年   583篇
  1995年   415篇
  1994年   486篇
  1993年   441篇
  1992年   470篇
  1991年   398篇
  1990年   444篇
  1989年   362篇
  1988年   369篇
  1987年   332篇
  1986年   323篇
  1985年   447篇
  1984年   413篇
  1983年   327篇
  1982年   327篇
  1981年   345篇
  1980年   282篇
  1979年   275篇
  1978年   277篇
  1977年   261篇
  1976年   285篇
  1974年   254篇
  1973年   264篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Ferric ferrocyanides synthesized from different sources of ferric cations and ferrocyanide anions and those derived from ferrous ferricyanide, ferrous ferrocyanide and ferric ferricyanide have been studied using Mössbauer and XRD techniques. Structural information of the effect of the provenance on the properties of the final compound is obtained. Significant correlations between isomer shift and quadrupole splitting of inner and outer iron cations have been observed.  相似文献   
82.
83.
84.
We consider the dynamics of the lowest order transversal vibration mode of a suspension bridge, for which the hangers are treated as one-sided springs, according to the model of Lazer and McKeena [SIAM Review 58, 1990, 537]. We analyze in particular the multi-stability of periodic attractors and the basin of attraction structure in phase space and its dependence with the model parameters. The parameter values used in numerical simulations have been estimated from a number of bridges built in the United States and in the United Kingdom, thus taking into account realistic, yet sometimes simplified, structural, aerodynamical, and physical considerations.  相似文献   
85.
Main properties of the excited states of 118Sn manifesting themselves in cascade γ decay of its compound state are studied. As in heavier nuclei studied earlier, qualitative interpretation of the whole set of observed properties of the nucleus appears to be impossible without accounting for coexistence and interaction of quasiparticle and collective nuclear excitations and their considerable influence on the main parameters of the process under study. From Yadernaya Fizika, Vol. 67, No. 10, 2004, pp. 1845–1849. Original English Text Copyright ? 2004 by Khitrov, Panteleev, Sukhovoj, Honzátko, Tomandl. This article was submitted by the authors in English.  相似文献   
86.
87.
This paper describes a robust and fast fitting procedure applicable for relaxing processes that cannot be understood as a discrete sum of single processes but require an activation energy distribution. The method is based on a set of closed-form expressions that allow the computation of the relaxation parameters directly from the isochronal curves obtained experimentally. The usefulness of this method is checked by analyzing the isochronal curves given by a theoretical energy distribution and the magnetic disaccommodation spectra observed in yttrium iron garnet (YIG) samples. PACS 02.60.Ed; 75.60.Lr; 75.50.Gg  相似文献   
88.
Summary. We prove that - under certain conditions - measurable solutions $f$ of the functional equation $f(x)=h(x,y,f(g_{1}(x,y)),\ldots,f(g_{n}(x,y))),\quad(x,y)\in D \subset \mathbb{R}^{s} \times \mathbb{R}^{l}$ are continuous, even if $1\le l\le s$. As a tool we introduce new classes of functions which - roughly speaking - interpolate between continuous and Lebesgue measurable functions. Connection between these classes are also investigated.  相似文献   
89.
The aim of the paper is to investigate the limit behaviour of the least squares estimator of the shift parameter of nearly unstable, nearly stable, and nearly explosive AR(1) models. Both zero start and stationary cases are treated. Connection with the maximum likelihood estimator of the shift parameter of continuous time AR(1) processes is also discussed.  相似文献   
90.
I. Jánossy 《Pramana》2003,61(2):435-445
It is suggested that liquid crystal—polymer interfaces are coupled systems, in which the components mutually influence the orientational state of each other. The photo-orientation process at liquid crystal-polymer interfaces provides a striking example of such a coupling. Experiments show that the anisotropic structure generated by polarised light at a polymer surface is strongly affected by the phase of the liquid crystal covering the polymer. Photo-orientation is significantly more efficient when the liquid crystal is in the isotropic phase than when it exhibits orientational order. The observations are interpreted by assuming that in the smectic and nematic phases the liquid crystal stabilises to a large extent polymer chain-segments aligned parallel to the director, while it blocks the photo-induced formation of chain-segments in the perpendicular direction. Other situations, in which the coupling between the liquid crystal and the polymer can be important, are also discussed briefly.  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