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   334893篇
  免费   2258篇
  国内免费   825篇
化学   152385篇
晶体学   5419篇
力学   17476篇
综合类   1篇
数学   51222篇
物理学   111473篇
  2020年   1927篇
  2019年   2175篇
  2018年   11109篇
  2017年   11866篇
  2016年   8042篇
  2015年   3516篇
  2014年   4434篇
  2013年   10840篇
  2012年   12098篇
  2011年   21699篇
  2010年   13808篇
  2009年   13772篇
  2008年   18907篇
  2007年   22239篇
  2006年   8637篇
  2005年   13918篇
  2004年   10211篇
  2003年   9514篇
  2002年   7550篇
  2001年   7366篇
  2000年   5807篇
  1999年   4412篇
  1998年   3722篇
  1997年   3607篇
  1996年   3583篇
  1995年   3219篇
  1994年   3146篇
  1993年   3230篇
  1992年   3326篇
  1991年   3509篇
  1990年   3270篇
  1989年   3197篇
  1988年   3245篇
  1987年   3138篇
  1986年   2954篇
  1985年   4012篇
  1984年   4238篇
  1983年   3375篇
  1982年   3614篇
  1981年   3516篇
  1980年   3411篇
  1979年   3550篇
  1978年   3640篇
  1977年   3477篇
  1976年   3617篇
  1975年   3300篇
  1974年   3300篇
  1973年   3357篇
  1972年   2353篇
  1971年   1919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