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   1390篇
  免费   74篇
  国内免费   9篇
电工技术   25篇
化学工业   422篇
金属工艺   36篇
机械仪表   33篇
建筑科学   27篇
能源动力   93篇
轻工业   121篇
水利工程   5篇
石油天然气   5篇
无线电   141篇
一般工业技术   357篇
冶金工业   62篇
原子能技术   10篇
自动化技术   136篇
  2024年   6篇
  2023年   50篇
  2022年   79篇
  2021年   102篇
  2020年   67篇
  2019年   74篇
  2018年   88篇
  2017年   63篇
  2016年   74篇
  2015年   52篇
  2014年   63篇
  2013年   100篇
  2012年   74篇
  2011年   81篇
  2010年   59篇
  2009年   51篇
  2008年   56篇
  2007年   40篇
  2006年   23篇
  2005年   17篇
  2004年   21篇
  2003年   19篇
  2002年   13篇
  2001年   14篇
  2000年   13篇
  1999年   8篇
  1998年   20篇
  1997年   20篇
  1996年   11篇
  1995年   8篇
  1994年   9篇
  1993年   12篇
  1992年   8篇
  1991年   5篇
  1990年   5篇
  1989年   6篇
  1988年   8篇
  1987年   2篇
  1986年   6篇
  1985年   10篇
  1984年   5篇
  1983年   6篇
  1982年   4篇
  1981年   6篇
  1980年   4篇
  1979年   3篇
  1976年   3篇
  1971年   1篇
  1970年   1篇
  1968年   1篇
排序方式: 共有1473条查询结果,搜索用时 15 毫秒
1.
Wireless Personal Communications - Recently, the theory of effective rate has attracted much attention, since it can take the delay aspect into account when performing channel capacity analysis. In...  相似文献   
2.
Covalent organic frameworks (COFs) show advantageous characteristics, such as an ordered pore structure and a large surface area for gas storage and separation, energy storage, catalysis, and molecular separation. However, COFs usually exist as difficult-to-process powders, and preparing continuous, robust, flexible, foldable, and rollable COF membranes is still a challenge. Herein, such COF membranes with fiber morphology for the first time prepared via a newly introduced template-assisted framework process are reported. This method uses electrospun porous polymer membranes as a sacrificial large dimension template for making self-standing COF membranes. The porous COF fiber membranes, besides having high crystallinity, also show a large surface area (1153 m2 g−1), good mechanical stability, excellent thermal stability, and flexibility. This study opens up the possibility of preparation of large dimension COF membranes and their derivatives in a simple way and hence shows promise in technical applications in separation, catalysis, and energy in the future.  相似文献   
3.
4.
Wireless Personal Communications - Traffic network is basically a “network of networks” consisting of mainly two types of networks: road network and a travel network. Due to drastic...  相似文献   
5.
6.
7.
Multimedia Tools and Applications - In the way of communication, facial expression act as non-verbal communication and play an important role in social interaction by providing some contextual...  相似文献   
8.
Many researchers approach the problem of programming distributed memory machines by assuming a global shared name space. Thus the user views the distributed memory of the machine as though it were shared. A major issue that arises at this point is how to manage the memory. When a processor accesses data stored on another processor's memory, data must be moved between the two processors. Once these data are retrieved from another processor's memory, several interesting issues are raised. Where should these data be stored locally? What transformations must be performed to the code to guarantee that the nonlocal accesses reference the correct memory location? What optimizations can be performed to reduce the time spent in accessing the nonlocal data? In this paper we examine various data migration mechanisms that allow an explicit and controlled mapping of data to memory. We describe, experimentally evaluate, and model a set of schemes for storing and retrieving off-processor array elements. The schemes are all based on using hash tables for efficient access of nonlocal data. The three different techniques evaluated are the basic hashed cache, partial enumeration, and full enumeration, the details of which are described in the paper. In all three schemes, nonlocal data are stored in hash tables—the difference is in the amount of memory used by the schemes and the retrieval mechanisms for nonlocal data.  相似文献   
9.
Higher order elastic constants have been calculated in ZnS at 300 K and 500 K following the interaction potential model. Ultrasonic attenuation, velocity and other related parameters have been calculated using the higher order elastic constants for the different size of the material at 500 K. The size dependency of the ultrasonic properties is discussed in correlation with elastic, thermal and electrical properties. It has been found that the thermal conductivity is the main contributor to the behaviour of the ultrasonic attenuation as a function of the size and the responsible cause of attenuation is phonon-phonon interaction. The semiconducting nature of ZnS film has been achieved with the study of size variation of thermal relaxation time and ultrasonic attenuation.  相似文献   
10.
Ion irradiation of Si8+ ion beam of 100 MeV was scattered by a gold foil on a Mylar membrane of 25 Μm thickness in the form of film roll (width, 12.5 cm and length, 400 cm) at the Nuclear Science Centre, New Delhi. The characterization of etched nuclear tracks was carried out by gas permeation measurements. The samples cut from the film roll of required size for permeability measurements were etched in a controlled manner in a constant temperature bath of 6N NaOH solution. The opening of the conical etched tracks was characterized by hydrogen gas permeation.  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