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   47679篇
  免费   1584篇
  国内免费   169篇
化学   26518篇
晶体学   242篇
力学   1213篇
综合类   13篇
数学   7997篇
物理学   13449篇
  2021年   375篇
  2020年   587篇
  2019年   458篇
  2018年   591篇
  2017年   566篇
  2016年   1232篇
  2015年   965篇
  2014年   1050篇
  2013年   2205篇
  2012年   2066篇
  2011年   2258篇
  2010年   1478篇
  2009年   1281篇
  2008年   2113篇
  2007年   1983篇
  2006年   1893篇
  2005年   1762篇
  2004年   1531篇
  2003年   1259篇
  2002年   1149篇
  2001年   1012篇
  2000年   820篇
  1999年   619篇
  1998年   538篇
  1997年   552篇
  1996年   649篇
  1995年   599篇
  1994年   608篇
  1993年   633篇
  1992年   680篇
  1991年   495篇
  1990年   487篇
  1989年   476篇
  1988年   451篇
  1987年   448篇
  1986年   432篇
  1985年   654篇
  1984年   601篇
  1983年   527篇
  1982年   548篇
  1981年   533篇
  1980年   540篇
  1979年   502篇
  1978年   488篇
  1977年   483篇
  1976年   455篇
  1975年   425篇
  1974年   443篇
  1973年   389篇
  1960年   315篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
111.
Directed and elliptic flow for the 197Au+197Au system at incident energies between 40 and 150 MeV per nucleon has been measured using the INDRA 4π multi-detector. For semi-central collisions, the excitation function of elliptic flow shows a transition from in-plane to out-of-plane emission at around 100 MeV per nucleon. The directed flow changes sign at a bombarding energy between 50 and 60 MeV per nucleon and remains negative at lower energies. Molecular dynamics calculations (CHIMERA) indicate sensitivity of the global squeeze-out transition on the σ NN and demonstrate the importance of angular momentum conservation in transport codes at low energies.  相似文献   
112.
This is summary of the activities of the working group on collider physics in the IXth Workshop on High Energy Physics Phenomenology (WHEPP-9) held at the Institute of Physics, Bhubaneswar, India in January 2006. Some of the work subsequently done on these problems by the subgroups formed during the workshop is included in this report.  相似文献   
113.
114.
115.
116.
117.
The standard method to diagnose and follow-up osteoporosis is the measurement of bone mineral density (BMD) using dual X-ray absorptiometry (DEXA). Manufacturers' manuals of DEXA devices state the intrascanner coefficient of variance is less than 0.01 g/cm2. The aim of this study was to evaluate the in vivo coefficient of variance of a Lunar DPX scanner in male and female healthy adult subjects. Average BMD for females and males were 1.170±0.091 g/cm2 and 1.272±0.115 g/cm2, respectively. Monthly phantom measurements provided and controlled by the manufacturer were 1.243±0.008 g/cm2 (range 1.222 to 1.257) and the coefficient of variance was 0.006. It is concluded that the in vivo coefficient of variance of DEXA devices can slightly be higher than that proposed by the manufacturer. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
118.
The structure of a sofic shift space is investigated, and Krieger's embedding theorem and Boyle's factor theorem are generalized to a large class of sofic shifts.

  相似文献   

119.
Problem fields with one or two generating problems and possibilities of varying existing problems give a good chance for self-activities of students and can be used for reaching different general aims. In this paper some topics concerning quadrilaterals will be presented. I hope they will animate teachers for more problem orientation in mathematics education. First we will reflect about different types of convex and non-convex quadrilaterals and possibilities of ordering them. Then we focus on middle-quadrilaterals and types of quadrilaterals with special middle-quadrilaterals as well as their logical ordering. Finally we investigate the analogies in space to the parallelogram and its sub-types and order them in the “house of parallelepipeds”.  相似文献   
120.
Since a comprehensive survey published in 1999 [1] much work was done in standardizing measuring methods to characterize the surface geometry of dispersed and/or porous solids and to certify reference materials. The present paper is an extension of a short communication [2]. It gives a survey on existing standards and reports on new drafts and proposals.  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