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   486016篇
  免费   3386篇
  国内免费   1404篇
化学   238287篇
晶体学   7535篇
力学   23730篇
综合类   7篇
数学   68011篇
物理学   153236篇
  2020年   3423篇
  2019年   3925篇
  2018年   11942篇
  2017年   12507篇
  2016年   10548篇
  2015年   5011篇
  2014年   7221篇
  2013年   17916篇
  2012年   16629篇
  2011年   26055篇
  2010年   17169篇
  2009年   17160篇
  2008年   23523篇
  2007年   26402篇
  2006年   14551篇
  2005年   18100篇
  2004年   14420篇
  2003年   13432篇
  2002年   11711篇
  2001年   11785篇
  2000年   9337篇
  1999年   7019篇
  1998年   6028篇
  1997年   5959篇
  1996年   5745篇
  1995年   4977篇
  1994年   5011篇
  1993年   5052篇
  1992年   5337篇
  1991年   5535篇
  1990年   5222篇
  1989年   5205篇
  1988年   5170篇
  1987年   5032篇
  1986年   4763篇
  1985年   6404篇
  1984年   6711篇
  1983年   5412篇
  1982年   5838篇
  1981年   5670篇
  1980年   5372篇
  1979年   5673篇
  1978年   5880篇
  1977年   5759篇
  1976年   5843篇
  1975年   5378篇
  1974年   5429篇
  1973年   5571篇
  1972年   3861篇
  1971年   3297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