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   1202篇
  免费   42篇
  国内免费   5篇
电工技术   12篇
化学工业   211篇
金属工艺   45篇
机械仪表   23篇
建筑科学   31篇
矿业工程   2篇
能源动力   58篇
轻工业   56篇
水利工程   3篇
石油天然气   2篇
无线电   165篇
一般工业技术   316篇
冶金工业   113篇
原子能技术   30篇
自动化技术   182篇
  2023年   12篇
  2022年   30篇
  2021年   58篇
  2020年   48篇
  2019年   42篇
  2018年   62篇
  2017年   48篇
  2016年   36篇
  2015年   26篇
  2014年   34篇
  2013年   77篇
  2012年   49篇
  2011年   62篇
  2010年   43篇
  2009年   48篇
  2008年   52篇
  2007年   47篇
  2006年   30篇
  2005年   20篇
  2004年   16篇
  2003年   17篇
  2002年   19篇
  2001年   18篇
  2000年   21篇
  1999年   19篇
  1998年   28篇
  1997年   18篇
  1996年   24篇
  1995年   25篇
  1994年   22篇
  1993年   24篇
  1992年   12篇
  1991年   18篇
  1990年   18篇
  1989年   14篇
  1988年   10篇
  1987年   5篇
  1986年   12篇
  1985年   11篇
  1984年   7篇
  1983年   19篇
  1982年   11篇
  1980年   3篇
  1978年   4篇
  1977年   4篇
  1976年   4篇
  1975年   3篇
  1974年   5篇
  1973年   4篇
  1970年   2篇
排序方式: 共有1249条查询结果,搜索用时 281 毫秒
1.
Semiconductors - In the present paper, analytical modeling of surface potential and drain current for hetero-dielectric double gate tunnel FET (HDG-TFET) has been done. The two dimensional (2D)...  相似文献   
2.
3.
Knowledge of the length–weight relationships (LWRs) of fish is an important tool to understand fish body form, growth pattern, stock management and their conservation. The present study focused on investigating the length–weight relationships for five catfish species, Pachypterus atherinoides (Bloch, 1794), belonging to family Horabagridae; Batasio batasio (Hamilton, 1822) family Bagridae; Bagarius yarrelli (Sykes, 1839), family Gogangra viridescens (Hamilton, 1822); and Sisor rhabdophorus (Hamilton, 1822) belonging to family Sisoridae. Specimens were collected from the middle stretch of the Ganga River in India from November 2016 to May 2018. A total of 174 specimens of five fish species were collected, and their total lengths were measured to the nearest centimetre and the body weight to the nearest gram. The value of the parameter slope (b) of LWRs of the five species ranged from 2.86 (B. yarrelli) to 3.16 (G. viridescens), with a mean value of 2.99. The results of the present study documented the new maximum total length (TL) for P. atherinoides and S. rhabdophorus. The present study also provides the first reference regarding LWRs for S. rhabdophorus.  相似文献   
4.
Eighteen compositions of MoO3-Te at 800 °C and seven of each of MoO3-Cd (at 500 °C) and MoO3-Sb (at 600 °C) were heat treated in vacuum-sealed quartz ampules. The phases of the heat-treated compositions were analyzed using x-ray diffraction (XRD) patterns. The interactions in the three systems are summarized. Three phases in equilibrium are (1) in the MnO3-Te system at 800 °C, Te, Mo4O11, TeMo4O13—(0<xMoO 3<0 889) and MoO3, Mo4O11, TeMo4O13—(0.889<xMoO 3<1); (2) in the MoO3_Cd system at 500 °C, Cd, MoO2, CdMoO4—(0<xMoO 3<0.6667) and MoO3, MoO2, CdMoO4—(0.6667<xMoO 3<1); and (3) in the MoO3-Sb system at 600 °C, Sb, MoO2, Sb4Mo10O31—(0<xMoO 3<0.734) and MoO3+MoO2+Sb4Mo10O31 (0.734<xMoO 3<1). The results lead to construction of ternary phase diagrams: Te-MoO3-TeMo4O13, Cd-MoO3-CdMoO4, and Sb-MoO3-Sb4Mo10O31.  相似文献   
5.
6.
7.
8.
A parameter-free geometric model for nuclear absorption is derived from microscopic theory. The expression for the absorption cross section in the eikonal approximation taken in integral form is separated into a geometric contribution, described by an energy-dependent effective radius, and two surface terms which are shown to cancel in an asymptotic series expansion. For collisions of light nuclei, an expression for the effective radius is derived using harmonic-oscillator nuclear density functions. A direct extension to heavy nuclei with Woods-Saxon densities is made by identifying the equivalent half density radius for the harmonic-oscillator functions. Coulomb corrections are incorporated and a simplified geometric form of the Bradt-Peters type obtained. Results spanning the energy range of 1 MeV/nucleon to 1 GeV/nucleon are presented. Good agreement with experimental results are obtained.  相似文献   
9.
10.
Vikram K Kinra  Vinay Dayal 《Sadhana》1987,10(3-4):419-432
A framework is presented for examining the effectiveness of limiting and modelling arguments used in the analysis of fluid flows. It consists of examining the consequences of the arguments on the flow problem as a whole and breaking down the limiting/modelling process into a sequence of steps and associated sequence of flow problems, termed here as ‘lidels’. The notion of validity of lidels is given. Several examples are given to explain the present approach. Invited general lecture at 3rd ACFM, Tokyo, September 1986  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