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   556834篇
  免费   4914篇
  国内免费   1506篇
化学   274378篇
晶体学   8168篇
力学   27555篇
综合类   11篇
数学   78299篇
物理学   174843篇
  2021年   4279篇
  2020年   4656篇
  2019年   5246篇
  2018年   12744篇
  2017年   13283篇
  2016年   12859篇
  2015年   6388篇
  2014年   9773篇
  2013年   22933篇
  2012年   20196篇
  2011年   29176篇
  2010年   20095篇
  2009年   20064篇
  2008年   26296篇
  2007年   28704篇
  2006年   17889篇
  2005年   19984篇
  2004年   16560篇
  2003年   15204篇
  2002年   13767篇
  2001年   14683篇
  2000年   11291篇
  1999年   8591篇
  1998年   7239篇
  1997年   7123篇
  1996年   6795篇
  1995年   5771篇
  1994年   5777篇
  1993年   5705篇
  1992年   6150篇
  1991年   6424篇
  1990年   6114篇
  1989年   6017篇
  1988年   5786篇
  1987年   5846篇
  1986年   5582篇
  1985年   7147篇
  1984年   7319篇
  1983年   6052篇
  1982年   6343篇
  1981年   6005篇
  1980年   5782篇
  1979年   6186篇
  1978年   6300篇
  1977年   6229篇
  1976年   6236篇
  1975年   5857篇
  1974年   5796篇
  1973年   6015篇
  1972年   4164篇
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
991.
992.
The influence of ultrasonic shock treatment on variation in the pearlite structure and properties is studied in the surface layer of carburized steel. It is shown that plastic deformation results in carbon redistribution and formation of new phases.  相似文献   
993.
994.
995.
The PARRNe facility has been used to produce neutron-rich isotopes 83,84Gaby the ISOL method. Their decay has been studied, and β-γ coincidence and γ-γ coincidence data were collected as a function of time. The first two excited levels in 83Ge and the first excited level in 84Ge have been measured for the first time.  相似文献   
996.
Journal of Experimental and Theoretical Physics - The magnetoresistance effect in the SmCu3Mn4O12 compound with a perovskite-like structure is investigated for the first time. It is found that an...  相似文献   
997.
The steady motion of a spheroidal aerosol particle with inner nonuniformly distributed heat sources (sinks) that is placed in an external temperature gradient is theoretically studied in the Stokes approximation. The mean temperature of the particle surface is assumed to differ slightly from that of the gaseous environment. An analytic expression for the force and rate of thermophoresis are found by solving the gas-dynamic equations in view of the motion of the environment.  相似文献   
998.
Preface     
Set-Valued and Variational Analysis -  相似文献   
999.
In the present paper we give necessary and sufficient conditions for the subgroup separability of the fundamental group of a finite graph of groups with finitely generated abelian vertex groups.

  相似文献   

1000.
An experiment was designed to determine whether normally sighted human subjects would be able to adapt to the handicapping effects of sudden deprivation of visual cues on horizontal plane sound localization. Two groups of sighted normal-hearing young adults participated. One group was allowed the benefit of sight. The other group was blindfolded. Measurements of accuracy and the time to respond were made daily over the course of five consecutive days, in a semi-reverberant sound proof booth that modeled listening in a small office. Sound localization was assessed using an array of eight speakers that surrounded the subject in space. Each day, one block of 120 trials was presented for each of three stimuli, two one-third octave noise bands, centred at 0.5 and 4 kHz, and broadband noise, to assess the utilization of interaural temporal difference cues, interaural level difference cues and binaural and spectral cues in combination. Blindfolded subjects were relatively less accurate than sighted subjects. Both groups showed gains with practice, the blindfolded group to a greater degree, largely due to improvements in the use of spectral cues. The blindfolded group took longer to respond than the sighted group, but showed greater decrements in response time with practice.  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