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   463745篇
  免费   5392篇
  国内免费   1323篇
化学   250132篇
晶体学   5214篇
力学   20757篇
综合类   16篇
数学   53991篇
物理学   140350篇
  2022年   3586篇
  2021年   5984篇
  2020年   6796篇
  2019年   7783篇
  2018年   6764篇
  2017年   6422篇
  2016年   8901篇
  2015年   5789篇
  2014年   8524篇
  2013年   20320篇
  2012年   15769篇
  2011年   19624篇
  2010年   15813篇
  2009年   16284篇
  2008年   18247篇
  2007年   17847篇
  2006年   16247篇
  2005年   14518篇
  2004年   14937篇
  2003年   13832篇
  2002年   12819篇
  2001年   15144篇
  2000年   10214篇
  1999年   8041篇
  1998年   6553篇
  1997年   6344篇
  1996年   6585篇
  1995年   5607篇
  1994年   5686篇
  1993年   5362篇
  1992年   5930篇
  1991年   5946篇
  1990年   5766篇
  1989年   5628篇
  1988年   5500篇
  1987年   5475篇
  1986年   5188篇
  1985年   6710篇
  1984年   6773篇
  1983年   5445篇
  1982年   5464篇
  1981年   5466篇
  1980年   4975篇
  1979年   5425篇
  1978年   5588篇
  1977年   5627篇
  1976年   5505篇
  1975年   5029篇
  1974年   4965篇
  1973年   4926篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
International Applied Mechanics - The motion of a solid body with a cavity containing a heavy multilayer ideal incompressible fluid is considered using a linear problem statement. An algorithm for...  相似文献   
2.
Mathematical Notes - The problem of finding the least number of variables of a first-order formula expressing the statement that an input-graph contains a subgraph isomorphic to a given...  相似文献   
3.
Differential Equations - We consider the Showalter–Sidorov problem for the stochastic version of the linear Ginzburg–Landau equation in Hilbert spaces of smooth differential forms...  相似文献   
4.
We consider the inverse problem of identifying a general source term, which is a function of both time variable and the spatial variable, in a parabolic PDE from the knowledge of boundary measurements of the solution on some portion of the lateral boundary. We transform this inverse problem into a problem of solving a compact linear operator equation. For the regularization of the operator equation with noisy data, we employ the standard Tikhonov regularization, and its finite dimensional realization is done using a discretization procedure involving the space $L^2(0,\tau;L^2(Ω))$. For illustrating the specification of an a priori source condition, we have explicitly obtained the range space of the adjoint of the operator involved in the operator equation.  相似文献   
5.
Doklady Mathematics - New properties of convex infinitely differentiable functions related to extremal problems are established. It is shown that, in a neighborhood of the solution, even if the...  相似文献   
6.
Crystallography Reports - The formation of β-Si3N4 for subsequent growth of AlGaN and GaN heterostructures of silicon wafers has been studied. It is established that the native oxide layer...  相似文献   
7.
Crystallography Reports - Methods of coherent X-ray diffraction imaging of the spatial structure of noncrystalline objects and nanocrystals (nanostructures) are considered. Particular attention is...  相似文献   
8.
Tinard  V.  François  P.  Fond  C. 《Experimental Mechanics》2021,61(7):1161-1170
Background

This paper is Part 2 of a study on the scope of the ultrasonic Surface Reflection Method (SRM). Part 1 deals with the theoretical conditions for a satisfactory usage of this method.

Objective

This second part validates the practical feasibility and reliability of the SRM method by comparison with the conventional Transmission Method (TM) in cases where the latter is applicable.

Methods

Two experimental devices (one for SRM and one for TM) are developed and measurements of shear and bulk moduli are carried out at ultrasonic frequency (610 kHz) and at room temperature.

Results

The experimental conditions in terms of sample geometry, pulse characteristics and interfacial transmission required to obtain a given accuracy on the measurement are stated. The SRM is then validated against other experimental methods and is used to determine the shear modulus of a carbon black filled neoprene at ambient temperature (T?=?21 °C) and ultrasonic frequency.

Conclusions

The benefit brought by this method is well demonstrated: a unique measurement allows the determination of all the moduli of a highly damping isotropic material (carbon black filled neoprene) not achievable by other methods.

  相似文献   
9.
International Journal of Theoretical Physics - In this paper, we present the annihilation and creation operators for a moving scalar massive particle on 1 + 1-de Sitter space. This presentation is...  相似文献   
10.
Physics of Atomic Nuclei - We review some results of diagnostics for the electromagnetic characteristics of the heliosphere and of the Earth magnetosphere within the model for cosmic ray modulation...  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