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   692167篇
  免费   8836篇
  国内免费   1812篇
电工技术   12525篇
综合类   755篇
化学工业   106225篇
金属工艺   26224篇
机械仪表   20269篇
建筑科学   16656篇
矿业工程   3371篇
能源动力   17956篇
轻工业   63270篇
水利工程   6977篇
石油天然气   12629篇
武器工业   68篇
无线电   76314篇
一般工业技术   131492篇
冶金工业   136635篇
原子能技术   14358篇
自动化技术   57091篇
  2021年   6255篇
  2020年   4486篇
  2019年   5834篇
  2018年   9904篇
  2017年   9687篇
  2016年   10277篇
  2015年   6993篇
  2014年   11653篇
  2013年   31202篇
  2012年   18499篇
  2011年   25385篇
  2010年   20034篇
  2009年   22412篇
  2008年   22964篇
  2007年   22821篇
  2006年   20043篇
  2005年   18201篇
  2004年   17488篇
  2003年   17151篇
  2002年   16452篇
  2001年   16426篇
  2000年   15409篇
  1999年   16144篇
  1998年   41381篇
  1997年   28961篇
  1996年   22176篇
  1995年   16751篇
  1994年   14629篇
  1993年   14291篇
  1992年   10459篇
  1991年   9735篇
  1990年   9826篇
  1989年   9494篇
  1988年   8900篇
  1987年   7920篇
  1986年   7827篇
  1985年   8819篇
  1984年   8279篇
  1983年   7376篇
  1982年   6966篇
  1981年   7080篇
  1980年   6768篇
  1979年   6557篇
  1978年   6432篇
  1977年   7581篇
  1976年   9929篇
  1975年   5613篇
  1974年   5273篇
  1973年   5441篇
  1972年   4493篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
This paper is intended to be a state of the art review of geothermal reservoir simulation. Its recent application to the modelling of real geothermal reservoirs is described and put in the context of an emerging general approach to reservoir modelling. The use of computer simulation for geothermal well test analysis is described. One of the main recent uses of reservoir simulators has been for conducting numerical experiments aimed at improving the understanding of geothermal reservoir physics. Such studies on fractured reservoirs, the thermal structure of reservoirs and the effects of non-condensable gases and dissolved salts are outlined.  相似文献   
994.
995.
This article describes WHIM, the Window Handler and Input Manager, a window management system being developed as part of the QuickSilver operating system project at IBM's Almaden Research Center. Another version of WHIM runs under AIX on the IBM PC RT. This article contrasts and compares the overlapped window scheme used in WHIM with the tiled window scheme used in other systems. The advantages of the window management scheme used in WHIM are detailed, and the effect of display interfaces on the window manager is described.  相似文献   
996.
A Graphene Field-Effect Device   总被引:2,自引:0,他引:2  
In this letter, a top-gated field-effect device (FED) manufactured from monolayer graphene is investigated. Except for graphene deposition, a conventional top-down CMOS-compatible process flow is applied. Carrier mobilities in graphene pseudo-MOS structures are compared to those obtained from the top-gated Graphene-FEDs. The extracted values exceed the universal mobility of silicon and silicon-on-insulator MOSFETs  相似文献   
997.
We describe a novel microfluidic perfusion system for high-resolution microscopes. Its modular design allows pre-coating of the coverslip surface with reagents, biomolecules, or cells. A poly(dimethylsiloxane) (PDMS) layer is cast in a special molding station, using masters made by photolithography and dry etching of silicon or by photoresist patterning on glass or silicon. This channel system can be reused while the coverslip is exchanged between experiments. As normal fluidic connectors are used, the link to external, computer-programmable syringe pumps is standardized and various fluidic channel networks can be used in the same setup. The system can house hydrogel microvalves and microelectrodes close to the imaging area to control the influx of reaction partners. We present a range of applications, including single-molecule analysis by fluorescence correlation spectroscopy (FCS), manipulation of single molecules for nanostructuring by hydrodynamic flow fields or the action of motor proteins, generation of concentration gradients, trapping and stretching of live cells using optical fibers precisely mounted in the PDMS layer, and the integration of microelectrodes for actuation and sensing.  相似文献   
998.
Infiltration systems are frequently used as an option to manage urban storm drainage. By reducing flows and volumes in downstream sewers or in surface waters, they decrease the overflows and make it possible to recharge groundwater. They come in various forms with different uses; therefore, their performance is diverse and integrates multiple aspects. Consequently, a multicriteria approach was developed in order to quantify the performance of these systems and to help in decision making problems. For that purpose, a list of performance indicators integrating technical, economical, environmental and social aspects was developed. The performances were defined with the help of a working group composed of engineers from different technical or strategic departments from Greater Lyon and researchers from different fields. The paper presents the last version of the performance indicators tested according to a set of quality requirements: availability of data, relevance, fidelity, precision, sensitivity/robustness. This critical review of the set of indicators has led us to redefine a certain number of indicators, identify numerous biases and allow putting forward general instructions for criterion or indicator construction. The last phase is to propose multicriteria decision aid methods; a procedure using ELECTRE methods should be used.  相似文献   
999.
1000.
The design principals of fast-operating electromagnetic drives with prescribed dynamic performances are examined. The represented procedure permits the command parameters to be to determined with the guaranteed prescribed parameters of the drive.  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