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   382611篇
  免费   2333篇
  国内免费   1182篇
化学   163462篇
晶体学   5743篇
力学   22209篇
综合类   1篇
数学   74999篇
物理学   119712篇
  2020年   1801篇
  2019年   2052篇
  2018年   18845篇
  2017年   19320篇
  2016年   12277篇
  2015年   3857篇
  2014年   4348篇
  2013年   10485篇
  2012年   14249篇
  2011年   28528篇
  2010年   17506篇
  2009年   17897篇
  2008年   23285篇
  2007年   28103篇
  2006年   8637篇
  2005年   14742篇
  2004年   11247篇
  2003年   10897篇
  2002年   8246篇
  2001年   7443篇
  2000年   5904篇
  1999年   4407篇
  1998年   3781篇
  1997年   3619篇
  1996年   3594篇
  1995年   3200篇
  1994年   3095篇
  1993年   3199篇
  1992年   3266篇
  1991年   3457篇
  1990年   3195篇
  1989年   3146篇
  1988年   3212篇
  1987年   3090篇
  1986年   2926篇
  1985年   3945篇
  1984年   4146篇
  1983年   3324篇
  1982年   3545篇
  1981年   3459篇
  1980年   3360篇
  1979年   3477篇
  1978年   3571篇
  1977年   3411篇
  1976年   3527篇
  1975年   3210篇
  1974年   3211篇
  1973年   3300篇
  1972年   2290篇
  1971年   1881篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
6.
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined.  相似文献   
7.
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic.  相似文献   
8.
9.
An attempt is made to find out the suitable entrainment and exit boundary conditions in laminar flow situations. Streamfunction vorticity formulation of the Navier–Stokes equations are solved by ADI method. Two‐dimensional laminar plane wall jet flow is used to test different forms of the boundary conditions. Results are compared with the experimental and similarity solution and the proper boundary condition is suggested. The Kind 1 boundary condition is recommended. It consists of zero first derivative condition for velocity variable and for streamfunction equation, mixed derivative at the entrainment and exit boundaries. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
10.
The paper discusses the applicability of quasi-crystalline approximation to describing the thermal motion of water molecules in their normal and supercooled states. The problem is subjected to the critical analysis of experimental data on incoherent scattering of slow neutrons based on theories developed by Singwi-Sjolander [1] and Oskotsky [2] modified to duly take into account the limited applicability range of diffusion approximation. The applicability conditions of quasi-crystalline approximation are shown to be consistently satisfied only when water is in supercooled state and within a narrow temperature range above the melting temperature.  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