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   1116篇
  免费   39篇
  国内免费   6篇
电工技术   10篇
综合类   1篇
化学工业   218篇
金属工艺   37篇
机械仪表   17篇
建筑科学   24篇
矿业工程   2篇
能源动力   82篇
轻工业   55篇
水利工程   4篇
石油天然气   2篇
无线电   143篇
一般工业技术   262篇
冶金工业   100篇
原子能技术   29篇
自动化技术   175篇
  2024年   6篇
  2023年   18篇
  2022年   50篇
  2021年   51篇
  2020年   55篇
  2019年   47篇
  2018年   63篇
  2017年   47篇
  2016年   34篇
  2015年   34篇
  2014年   40篇
  2013年   65篇
  2012年   49篇
  2011年   54篇
  2010年   35篇
  2009年   37篇
  2008年   36篇
  2007年   39篇
  2006年   24篇
  2005年   16篇
  2004年   11篇
  2003年   12篇
  2002年   17篇
  2001年   18篇
  2000年   18篇
  1999年   13篇
  1998年   25篇
  1997年   17篇
  1996年   22篇
  1995年   17篇
  1994年   16篇
  1993年   20篇
  1992年   11篇
  1991年   18篇
  1990年   17篇
  1989年   15篇
  1988年   10篇
  1987年   5篇
  1986年   12篇
  1985年   9篇
  1984年   5篇
  1983年   14篇
  1982年   10篇
  1980年   3篇
  1978年   4篇
  1977年   3篇
  1976年   3篇
  1975年   3篇
  1974年   3篇
  1970年   2篇
排序方式: 共有1161条查询结果,搜索用时 15 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.
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   
3.
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   
4.
5.
6.
7.
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   
8.
9.
Views stored in a data warehouse need to be kept current. As recomputing the views is very expensive, incremental maintenance algorithms are required. Over recent years, several incremental maintenance algorithms have been proposed. None of the proposed algorithms handle the general case of relational expressions involving aggregate and outerjoin operators efficiently.  相似文献   
10.
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