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   1379086篇
  免费   28783篇
  国内免费   7464篇
化学   687147篇
晶体学   13432篇
力学   76654篇
综合类   96篇
数学   246749篇
物理学   391255篇
  2020年   15999篇
  2019年   16113篇
  2018年   16653篇
  2017年   15191篇
  2016年   29075篇
  2015年   20723篇
  2014年   30174篇
  2013年   74100篇
  2012年   41816篇
  2011年   43271篇
  2010年   40303篇
  2009年   42056篇
  2008年   41173篇
  2007年   37797篇
  2006年   39280篇
  2005年   34820篇
  2004年   33927篇
  2003年   30755篇
  2002年   27671篇
  2001年   29512篇
  2000年   24153篇
  1999年   20853篇
  1998年   18995篇
  1997年   19479篇
  1996年   19291篇
  1995年   18606篇
  1994年   18212篇
  1993年   17748篇
  1992年   18022篇
  1991年   18252篇
  1990年   17461篇
  1989年   17495篇
  1988年   17140篇
  1987年   17092篇
  1986年   15987篇
  1985年   22470篇
  1984年   23626篇
  1983年   19664篇
  1982年   21342篇
  1981年   20574篇
  1980年   19860篇
  1979年   20313篇
  1978年   21540篇
  1977年   21203篇
  1976年   20938篇
  1975年   19645篇
  1974年   19292篇
  1973年   19774篇
  1972年   14270篇
  1967年   12683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.
Publications mathématiques de l'IHÉS - We show that stationary characters on irreducible lattices $\Gamma < G$ of higher-rank connected semisimple Lie groups are conjugation...  相似文献   
10.
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   
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