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   1629篇
  免费   43篇
  国内免费   2篇
电工技术   43篇
综合类   2篇
化学工业   467篇
金属工艺   33篇
机械仪表   17篇
建筑科学   88篇
矿业工程   8篇
能源动力   28篇
轻工业   253篇
水利工程   10篇
石油天然气   1篇
无线电   81篇
一般工业技术   233篇
冶金工业   252篇
原子能技术   8篇
自动化技术   150篇
  2022年   21篇
  2021年   34篇
  2020年   23篇
  2019年   28篇
  2018年   21篇
  2017年   15篇
  2016年   31篇
  2015年   29篇
  2014年   37篇
  2013年   54篇
  2012年   50篇
  2011年   66篇
  2010年   58篇
  2009年   45篇
  2008年   49篇
  2007年   62篇
  2006年   45篇
  2005年   36篇
  2004年   40篇
  2003年   39篇
  2002年   35篇
  2001年   16篇
  2000年   28篇
  1999年   15篇
  1998年   35篇
  1997年   37篇
  1996年   30篇
  1995年   24篇
  1994年   30篇
  1993年   27篇
  1992年   40篇
  1991年   19篇
  1990年   31篇
  1989年   22篇
  1988年   14篇
  1987年   24篇
  1986年   15篇
  1985年   30篇
  1984年   24篇
  1983年   25篇
  1982年   16篇
  1981年   27篇
  1980年   14篇
  1979年   15篇
  1978年   24篇
  1977年   16篇
  1976年   18篇
  1974年   17篇
  1972年   15篇
  1970年   16篇
排序方式: 共有1674条查询结果,搜索用时 734 毫秒
1.
Experimental and theoretical studies are performed in order to illuminate, for first time, the intercalation mechanism of polycyclic aromatic molecules into graphite oxide. Two representative molecules of this family, aniline and naphthalene amine are investigated. After intercalation, aniline molecules prefer to covalently connect to the graphene oxide matrix via chemical grafting, while napthalene amine molecules bind with the graphene oxide surface through π–π interactions. The presence of intercalated aromatic molecules between the graphene oxide layers is demonstrated by X‐ray diffraction, while the type of interaction between graphene oxide and polycyclic organic molecules is elucidated by X‐ray photoelectron spectroscopy. Combined quantum mechanical and molecular mechanical calculations describe the intercalation mechanism and the aniline grafting, rationalizing the experimental data. The present work opens new perspectives for the interaction of various aromatic molecules with graphite oxide and the so‐called “intercalation chemistry”.  相似文献   
2.
3.
A new type of bottom‐emission electroluminescent device is described in which a metal oxide is used as the electron‐injecting contact. The preparation of such a device is simple. It consists of the deposition of a thin layer of a metal oxide on top of an indium tin oxide covered glass substrate, followed by the solution processing of the light‐emitting layer and subsequently the deposition of a high‐workfunction (air‐stable) metal anode. This architecture allows for a low‐cost electroluminescent device because no rigorous encapsulation is required. Electroluminescence with a high brightness reaching 5700 cd m–2 is observed at voltages as low as 8 V, demonstrating the potential of this new approach to organic light‐emitting diode (OLED) devices. Unfortunately the device efficiency is rather low because of the high current density flowing through the device. We show that the device only operates after the insertion of an additional hole‐injection layer in between the light‐emitting polymer (LEP) and the metal anode. A simple model that explains the experimental results and provides avenues for further optimization of these devices is described. It is based on the idea that the barrier for electron injection is lowered by the formation of a space–charge field over the metal‐oxide–LEP interface due to the build up of holes in the LEP layer close to this interface.  相似文献   
4.
Meeting time and cost objectives in complex projects involves specific problems and risks. An attempt is made to analyse the components of total cost increase of a project caused by time delay. An outline is given as to how these considerations can be used to estimate cost increases in investors' decision situations as well as to ascertain fair contractual penalties and claims for compensation and for the evaluation of justified project acceleration costs.  相似文献   
5.
6.
7.
8.
9.
10.
This paper reports on an evaluation of real-time properties of MAP (Manufacturing Automation Protocol) networks by analytical considerations and measurements. Based on a model of the time schedule of a communication cycle figures for response times (transport system) and message delays (MAC layer) are given. The influence of some options for handling acknowledgments within the transport layer is shown. The message delay at MAC layer is separated into an implementation-dependent and a protocol-dependent protion, and an upper bound is derived. Rules for selecting protocol parameters affecting real time behavior are given. Aspects for improved implementations of communication controllers for MAP networks are discussed.  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