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   366871篇
  免费   2927篇
  国内免费   1102篇
化学   158138篇
晶体学   5124篇
力学   21063篇
综合类   6篇
数学   74039篇
物理学   112530篇
  2021年   1956篇
  2020年   2167篇
  2019年   2458篇
  2018年   19056篇
  2017年   19449篇
  2016年   12607篇
  2015年   4265篇
  2014年   4483篇
  2013年   10299篇
  2012年   14867篇
  2011年   28873篇
  2010年   17545篇
  2009年   17731篇
  2008年   23389篇
  2007年   28300篇
  2006年   8829篇
  2005年   15020篇
  2004年   11353篇
  2003年   10837篇
  2002年   8041篇
  2001年   6981篇
  2000年   5618篇
  1999年   4120篇
  1998年   3391篇
  1997年   3325篇
  1996年   3228篇
  1995年   2929篇
  1994年   2712篇
  1993年   2582篇
  1992年   2866篇
  1991年   2850篇
  1990年   2764篇
  1989年   2556篇
  1988年   2619篇
  1987年   2619篇
  1986年   2441篇
  1985年   3151篇
  1984年   3396篇
  1983年   2781篇
  1982年   2971篇
  1981年   2932篇
  1980年   2789篇
  1979年   2884篇
  1978年   2981篇
  1977年   2904篇
  1976年   2994篇
  1975年   2750篇
  1974年   2724篇
  1973年   2891篇
  1972年   1819篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
In this work, the effect of various properties of materials on vacuum breakdown initiated by laser radiation is considered. Estimating calculations are performed which show that the material of the target electrode distinctly affects the minimum energy of laser radiation needed for igniting a vacuum spark. The experimental studies carried out confirm the estimating calculations, and a number of materials are revealed which can be arranged in order of increase in the energy needed for the formation of breakdown in vacuum by the impact of a laser pulse.  相似文献   
74.
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages.  相似文献   
75.
S. D. Campos 《中国物理C(英文版)》2020,44(10):103103-103103-10
This work presents the subtraction procedure and the Regge cut in the logarithmic Regge pole approach. The subtraction mechanism leads to the same asymptotic behavior as previously obtained in the non-subtraction case. The Regge cut, in contrast, introduces a clear role to the non-leading contributions for the asymptotic behavior of the total cross-section. From these results, some simple parameterization is introduced to fit the experimental data for the proton-proton and antiproton-proton total cross-section above some minimum value up to the cosmic-ray. The fit parameters obtained are used to present predictions for the \begin{document}$ \rho(s)$\end{document} -parameter as well as to the elastic slope \begin{document}$ B(s)$\end{document} at high energies.  相似文献   
76.
Molecular dynamics simulation was performed to study the formation of cluster structure, interfaces, and surfaces with different curvature radii in a perfect nanocrystal passed through by a nonlinear wave. It is shown that this process is a type of nanostructure self-organization in response to an external energy flux with subsequent development of a strong rotational field.  相似文献   
77.
Luyen  D. T. 《Mathematical Notes》2022,112(1-2):239-250
Mathematical Notes - We study the multiplicity of weak solutions to the boundary-value problem $$\begin{alignedat}{2} - M\biggl(\iint_{\mathbb R^{2N}}|u(x)-u(y)|^2 K(x-y)\,d x\,d y\biggr)\mathscr...  相似文献   
78.
Sargsyan  A.  Vartanyan  T. A.  Sarkisyan  D. 《Optics and Spectroscopy》2021,129(11):1173-1178
Optics and Spectroscopy - A cell with a submicron thickness was used to measure the broadening and shift of the D1 and D2 lines of Rb atoms by neon. The resolution of hypefine components...  相似文献   
79.
Journal of Dynamics and Differential Equations - We deal with a weakly coupled system of ODEs of the type $$\begin{aligned} x_j'' + n_j^2 \,x_j + h_j(x_1,\ldots ,x_d) = p_j(t), \qquad...  相似文献   
80.
Periodica Mathematica Hungarica - We present a tight parametrical Hermite–Hadamard type inequality with probability measure, which yields a considerably closer upper bound for the mean value...  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