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   3655篇
  免费   89篇
  国内免费   9篇
电工技术   44篇
综合类   1篇
化学工业   478篇
金属工艺   134篇
机械仪表   82篇
建筑科学   151篇
矿业工程   66篇
能源动力   86篇
轻工业   309篇
水利工程   21篇
石油天然气   15篇
武器工业   1篇
无线电   334篇
一般工业技术   578篇
冶金工业   928篇
原子能技术   37篇
自动化技术   488篇
  2021年   25篇
  2020年   30篇
  2019年   33篇
  2018年   42篇
  2017年   31篇
  2016年   41篇
  2015年   40篇
  2014年   58篇
  2013年   212篇
  2012年   90篇
  2011年   131篇
  2010年   127篇
  2009年   125篇
  2008年   139篇
  2007年   111篇
  2006年   108篇
  2005年   89篇
  2004年   93篇
  2003年   87篇
  2002年   88篇
  2001年   69篇
  2000年   68篇
  1999年   71篇
  1998年   246篇
  1997年   155篇
  1996年   117篇
  1995年   86篇
  1994年   84篇
  1993年   92篇
  1992年   48篇
  1991年   47篇
  1990年   47篇
  1989年   27篇
  1988年   34篇
  1987年   38篇
  1986年   39篇
  1985年   52篇
  1984年   52篇
  1983年   48篇
  1982年   45篇
  1981年   54篇
  1980年   72篇
  1979年   60篇
  1978年   51篇
  1977年   59篇
  1976年   62篇
  1975年   39篇
  1974年   28篇
  1973年   23篇
  1971年   18篇
排序方式: 共有3753条查询结果,搜索用时 125 毫秒
41.
The Wabash River Integrated Methanol and Power Production from Clean Coal Technologies (IMPPCCT) project is investigating an Early Entrance Coproduction Plant (EECP) concept to evaluate integrated electrical power generation and methanol production from coal and other carbonaceous feedstocks. Research, development and testing (RD&T) that is currently being conducted under the project is evaluating cost effective process systems for removing contaminants, particularly sulfur species, from the generated gas which contains mainly synthesis gas (syngas), CO2 and steam at concentrations acceptable for the methanol synthesis catalyst. The RD&T includes laboratory testing followed by bench-scale and field testing at the SG Solutions Gasification Plant located in West Terre Haute, Indiana. Actual synthesis gas produced by the plant was utilized at system pressure and temperature for bench-scale field testing.  相似文献   
42.
43.
A 16-Mb magnetic random access memory (MRAM) is demonstrated in 0.18-/spl mu/m three-Cu-level CMOS with a three-level MRAM process adder. The chip, the highest density MRAM reported to date, utilizes a 1.42/spl mu/m/sup 2/ 1-transistor 1-magnetic tunnel junction (1T1MTJ) cell, measures 79 mm/sup 2/ and features a /spl times/16 asynchronous SRAM-like interface. The paper describes the cell, architecture, and circuit techniques unique to multi-Mb MRAM design, including a novel bootstrapped write driver circuit. Hardware results are presented.  相似文献   
44.
45.
46.
This paper reviews the prospects of thin-film silicon-on-sapphire (TFSOS) CMOS technology in microwave applications in the 1-5 GHz regime and beyond and presents the first demonstration of microwave integrated circuits based on this technology, MOSFET's optimized for microwave use, with 0.5-μm optically defined gate lengths and a T-gate structure, have ft values of 25 GHz (14 GHz) and fmax values of 66 GHz (41 GHz) for n-channel (p-channel) devices and have noise figure values below 1 db at 2 GHz, some of the best reported performance characteristics of any silicon-based MOSFET's to date. On-chip spiral inductors exhibit quality factors above ten. Circuit performance compares favorably with that of other CMOS-based technologies and approach performance levels similar to those obtained by silicon bipolar technologies. The results demonstrate the significant potential of this technology for microwave applications  相似文献   
47.
The United States has historically excelled in the design of products, processes and new technologies. Capitalizing on this historical strength to teach applied mathematics and science has many positive implications on education. First, engineering design can be used as a vehicle for addressing deficiencies in mathematics and science education. Second, as achievement in mathematics and science is enhanced, a greater number of students at an earlier age will be exposed to technical career opportunities. Third, enhancing elementary and secondary curricula with engineering design can attract underrepresented populations, such as minorities and females, to engineering as a profession. This paper describes a new and innovative engineering design curriculum, under development in the Austin Independent School District (AISD) in Austin, TX. The philosophic goals upon which the curriculum is based include: integrating the design problem-solving process into elementary schools, demonstrating the relationship of technical concepts to daily life, availing teachers with instructional strategies for teaching applied (as opposed to purely theoretical) science and mathematics, and teaching teamwork skills that are so greatly needed in industry and everyday life. Based on these goals, kindergarten, first grade, and second grade engineering design lessons have been piloted in AISD, in conjunction with a University of Texas program for teacher enhancement and preparation.  相似文献   
48.
Interval Heaps     
van Leeuwen  J.; Wood  D. 《Computer Journal》1993,36(3):209-216
  相似文献   
49.
The energies of resonances in the 27Al(p, γ) reaction at 992 and 1317 keV and of the threshold of the 27Al(p, n) reaction at 5804 keV have been measured accurately with respect to a 1 V standard. Both calibration energies and energies suitable for Q-value calculations are given. Corrections are made for the effects of the energy distribution of the proton beam, of nonuniform energy loss of the protons in the target and of ionisation of the target atoms.  相似文献   
50.
Regenerative axon growth in peripheral neurons is accompanied by increased expression of the growth-associated protein GAP-43. We examined the increase of GAP-43 immunoreactivity in DRG neurons following lesions at different distances along the sciatic nerve, using immunocytochemistry. To control for the variable involvement of DRG axons following injury at different sites, injured neurons were identified by retrograde labeling with Fluoro-Gold. GAP-43 labeling was similar for proximal, distal, and far-distal injuries when only injured neurons are considered. Our results stand in contrast to studies which show that GAP-43 upregulation in neurons of the central nervous system occurs only when lesions are made close to the cell body. This suggests that the mechanisms which control GAP-43 expression following injury differ between central and peripheral neurons.  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