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   26252篇
  免费   587篇
  国内免费   30篇
电工技术   342篇
综合类   39篇
化学工业   5803篇
金属工艺   388篇
机械仪表   487篇
建筑科学   1428篇
矿业工程   100篇
能源动力   667篇
轻工业   1979篇
水利工程   267篇
石油天然气   105篇
无线电   1977篇
一般工业技术   4699篇
冶金工业   4759篇
原子能技术   211篇
自动化技术   3618篇
  2024年   161篇
  2023年   268篇
  2022年   371篇
  2021年   645篇
  2020年   466篇
  2019年   588篇
  2018年   547篇
  2017年   474篇
  2016年   672篇
  2015年   560篇
  2014年   758篇
  2013年   1443篇
  2012年   1168篇
  2011年   1526篇
  2010年   1090篇
  2009年   1031篇
  2008年   1167篇
  2007年   1099篇
  2006年   962篇
  2005年   780篇
  2004年   749篇
  2003年   664篇
  2002年   576篇
  2001年   439篇
  2000年   380篇
  1999年   414篇
  1998年   799篇
  1997年   580篇
  1996年   477篇
  1995年   426篇
  1994年   392篇
  1993年   380篇
  1992年   281篇
  1991年   206篇
  1990年   279篇
  1989年   273篇
  1988年   224篇
  1987年   236篇
  1986年   232篇
  1985年   273篇
  1984年   232篇
  1983年   229篇
  1982年   211篇
  1981年   196篇
  1980年   170篇
  1979年   203篇
  1978年   167篇
  1977年   195篇
  1976年   242篇
  1975年   164篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
AC thin film electroluminescent (ACTFEL) devices emit light laterally in addition to conventional surface emission. Because of the waveguiding in ACTFEL devices, lateral emission is stronger than surface emission. However, the former is ignored for displays. This note demonstrates that mirrors can be fabricated into substrates to reflect upward the lateral emission, which can then be summed with surface emission for displays. Use of standard silicon and thin film technology has demonstrated that the reflected lateral emission is a factor of three brighter than conventional surface emission. hence the effective efficiency of out-coupling the light has been improved for an ACTFEL device  相似文献   
22.
Improving the vacuum would increase the insulation capacity of commercially available glass containers by a factor of about two. To do this, pressures of 10?4 mbar must be attained. Different approaches were taken to meet this objective. As an alternative to today's commonly practiced sealing method, three possibilities are introduced which eliminate the necessity of pump stub narrowing which causes reduced conductance. Furthermore, depending on the sealing process used, the gases occuring during sealing are either avoided completly or they can at least be reduced by having the chance of exact temperature control resp. by a lower separation temperature. A completly different approach was taken by using Getters, of which a metal hydride on a TiVMn base proved especially suitable. It is activated by heat and can be integrated into the normal production process without any problem. Aside from a shorter pump period, the added advantage here is the containment of the gasses occuring during sealing as well as that of the longterm gasses.  相似文献   
23.
A rapid and easy analysis method for polymers is presented. The method involves sample preparation by SFE, separation of the extracted compounds by SFC and simultaneous quantitative detection by FID, as well as identification of unknowns by MS. The applications illustrate how structural research work and routine polymer analysis can be done with this time saving method.  相似文献   
24.
Two serious flaws in popular client firewall software have been uncovered in February  相似文献   
25.
Everyday memory performance was examined longitudinally in 2 groups of Ss meeting the diagnostic criteria for age-associated memory impairment (AAMI). One group of 157 participants in a drug trial for reversing memory loss in AAMI was tested over multiple sessions. The other group of 75 persons did not participate in a drug trial and thus was tested only twice. Both groups were retested for longitudinal follow-up about 4 yrs after initial session. Follow-up test performance remained fairly stable relative to initial performance in both groups. The drug study group showed large practice effects during the course of the drug studies, but these effects subsided after the drug studies' end. Implications regarding memory decline in the normal elderly and neuropsychological measurement issues are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
26.
Book review     
Published in 1989, 585 pages, $180; Available from the American Institute of Chemical Engineers, 345 East 47th St., Publication Sales Department, New York, NY 10017.  相似文献   
27.
28.
Performance on computer-simulated, everyday memory tasks was found to deteriorate with age in 434 Belgian (aged 14–88 yrs) and 434 American Ss matched on gender and age. This age-related memory decline was reasonably consistent across samples. Difficulties in cross-cultural research and the advantages of ecologically valid measurement instruments are discussed. Instruments included a grocery list selective reminding test, the Wechsler Memory Scale, the Benton Visual Retention Test, and the Wechsler Adult Intelligence Scale (WAIS). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
29.
The gas flow sputter technique was invented a few years ago particularly for the inexpensive fabrication of sophisticated ceramic layers. Meanwhile, it has matured and become increasingly powerful. Today it is on the verge of being applied in industrial fabrication processes. The present article gives an overview over the method, its characteristics and the numerous applications.  相似文献   
30.
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