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   61778篇
  免费   3226篇
  国内免费   183篇
电工技术   1940篇
综合类   1482篇
化学工业   13911篇
金属工艺   882篇
机械仪表   1276篇
建筑科学   1559篇
矿业工程   572篇
能源动力   539篇
轻工业   3779篇
水利工程   733篇
石油天然气   121篇
武器工业   5篇
无线电   2195篇
一般工业技术   6730篇
冶金工业   21522篇
原子能技术   213篇
自动化技术   7728篇
  2023年   865篇
  2022年   467篇
  2021年   853篇
  2020年   748篇
  2019年   678篇
  2018年   1063篇
  2017年   1096篇
  2016年   1707篇
  2015年   1624篇
  2014年   1308篇
  2013年   1941篇
  2012年   2694篇
  2011年   2880篇
  2010年   1535篇
  2009年   1745篇
  2008年   1058篇
  2007年   1046篇
  2006年   865篇
  2005年   3659篇
  2004年   2891篇
  2003年   2346篇
  2002年   1103篇
  2001年   903篇
  2000年   352篇
  1999年   737篇
  1998年   6348篇
  1997年   3945篇
  1996年   2714篇
  1995年   1649篇
  1994年   1242篇
  1993年   1341篇
  1992年   418篇
  1991年   444篇
  1990年   472篇
  1989年   469篇
  1988年   440篇
  1987年   408篇
  1986年   405篇
  1985年   343篇
  1984年   253篇
  1983年   270篇
  1982年   300篇
  1981年   396篇
  1980年   364篇
  1977年   768篇
  1976年   1481篇
  1975年   319篇
  1974年   240篇
  1973年   427篇
  1972年   267篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
Summary An examination of possible forms of traction free surface wave in anisotropic elastic materials is undertaken. The results yield some interesting features of a certain arbitrariness which exists in displacement waves on a traction free surface in anisotropic media.  相似文献   
46.
47.
There are some foods that contain mutagenic or carcinogenic agents, some of which occur naturally and others that may be formed during preparation or cooking. Several foods such as legumes, also contain natural antimutagens and/or anticarcinogens. Lupine is one such legume that contains high amounts of protein (40%) and oils (14%). About 90 species of lupine have been reported throughout Mexico. However, the use of this crop as a source of food has been limited by the presence of antinutritional agents such as phenolic compounds (PC), carbohydrates (CH) and quinolizidinic alkaloids (Qas). It has also been suggested that consuming these compounds can affect human health and may even reduce the risk of disease. The objective of this work was to determine the effect of PC, CH and Qas, isolated and quantified from Lupinus campestris on the mutagenicity of 1-nitropyrene (1-NP) as a model mutagen and we used the Salmonella typhimurium tester strain YG1024 by the Kado microsuspension method. The results indicate that L. campestris seeds have 11 mg (+)catechin equivalent g(-1) seed coat; 120.3 mg g(-1) seeds and 2.13 mg g(-1) seeds of PC, CH and Qas, respectively. 1-NP mutagenicity was inhibited by 86% for PC, 76% for CH and 75% for Qas at concentrations of 200, 512 and 13.6 microg/tube, respectively.  相似文献   
48.
Programs for rule based electromyography (EMG) interpretation and reporting are described. A number of parameters are obtained during an EMG investigation. The combination of these data leads to a neurophysiological conclusion. Knowledge from the literature, research and experience is the basis for rule development. Rules have been developed for 14 of the most commonly used classifications of an EMG. The syntax is relatively easy and the user may change the rules, add rules or apply the system for other types of data. The results are displayed in a new graphical way. The system presented here is part of an integrated EMG laboratory with administrative routines, distributed databases for storage of results and routines for automatic report generation.  相似文献   
49.
Conductive plastics for electrical and electronic applications   总被引:2,自引:0,他引:2  
  相似文献   
50.
Summary The uniqueness of some helical flows of a second grade fluid, between two infinite circular cylinders, is proved. Initially, the fluid is at rest and flow is produced by the motion of the cylinders. Finally, the special case of a flow in a circular cylinder is considered.  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