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   1667944篇
  免费   25451篇
  国内免费   7216篇
电工技术   35677篇
综合类   6636篇
化学工业   280625篇
金属工艺   67318篇
机械仪表   48701篇
建筑科学   49716篇
矿业工程   12052篇
能源动力   50710篇
轻工业   131414篇
水利工程   16980篇
石油天然气   38598篇
武器工业   199篇
无线电   202246篇
一般工业技术   310368篇
冶金工业   236840篇
原子能技术   34857篇
自动化技术   177674篇
  2021年   15843篇
  2020年   12174篇
  2019年   14928篇
  2018年   20267篇
  2017年   20038篇
  2016年   23744篇
  2015年   17931篇
  2014年   29040篇
  2013年   88680篇
  2012年   40118篇
  2011年   56406篇
  2010年   47540篇
  2009年   54866篇
  2008年   51504篇
  2007年   49731篇
  2006年   48264篇
  2005年   44384篇
  2004年   45275篇
  2003年   44822篇
  2002年   43224篇
  2001年   40279篇
  2000年   38244篇
  1999年   38535篇
  1998年   67636篇
  1997年   53084篇
  1996年   44288篇
  1995年   36059篇
  1994年   33030篇
  1993年   32929篇
  1992年   27474篇
  1991年   24789篇
  1990年   25018篇
  1989年   24122篇
  1988年   22659篇
  1987年   20803篇
  1986年   20193篇
  1985年   23510篇
  1984年   22982篇
  1983年   20950篇
  1982年   19791篇
  1981年   19974篇
  1980年   18625篇
  1979年   18940篇
  1978年   18222篇
  1977年   19097篇
  1976年   21840篇
  1975年   16335篇
  1974年   15748篇
  1973年   15900篇
  1972年   13352篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
A redundant multivalued logic is proposed for high-speed communication ICs. In this logic, serial binary data are received and converted into parallel redundant multivalued data. Then they are restored into parallel binary data. Because of the multivalued data conversion, this logic makes it possible to achieve higher operating speeds than that of a conventional binary logic. Using this logic, a 1:4 demultiplexer (DEMUX, serial-parallel converter) IC was fabricated using a 0.18-/spl mu/m CMOS process. The IC achieved an operating speed of 10 Gb/s with a supply voltage of only 1.3 V and with power consumption of 38 mW. This logic may achieve CMOS communication ICs with an operating speed several times greater than 10 Gb/s.  相似文献   
93.
The hydrogen content, its depth distribution, and its bonding configuration have been studied in hydrogenated amorphous silicon prepared by plasma-enhanced chemical vapor deposition with hydrogen-diluted silane. Nuclear reaction analysis and infrared spectroscopy were used to determine the total amount of hydrogen and its bonded component, respectively. It has been established that the total concentration of hydrogen does not depend on the film thickness, and has a uniform depth profile. The concentration of bonded hydrogen changes with the film thickness within the measurement accuracy. The data obtained suggest the presence of molecular (non-bonded) hydrogen, uniformly distributed in concentration across the film thickness.  相似文献   
94.
Lateral scattering of retrograde well implants is shown to have an effect on the threshold voltage of nearby devices. The threshold voltage of both NMOSFETs and PMOSFETs increases in magnitude for conventional retrograde wells, but for triple-well isolated NMOSFETs the threshold voltage decreases for narrow devices near the edge of the well. Electrical data, SIMS, and SUPREM4 simulations are shown that elucidate the phenomenon.  相似文献   
95.
Deformation behavior of stoichiometric blends made from poly(styrene-co-styrenesulfonic acid) (SPS) and poly(styrene-co-4-vinylpyridine) (SVP) was investigated by TEM observation of strained thin films. An FTIR investigation revealed that ionic cross-links were formed between the component polymers upon blending due to intermolecular ion-ion interactions, which arose from proton transfer from sulfonic acid groups to pyridine groups. TEM observations indicate that the deformation mode of the blends changed from crazing only to crazing plus shear deformation, with the shear contribution becoming larger, as the ion content in the blends increased. Such changes in deformation mode can be understood as arising from an increase in the ‘effective’ strand density due to the formation of ionic cross-links upon blending. It was also found that the ionic cross-links via pyridinium cation/sulfonate anion ion pairs were more effective in inducing the transition of deformation mode than ionic cross-links via -SO3/Na+ or -SO3/Ca2+ ion pairs.  相似文献   
96.
番禺30-1砂岩强水驱气藏储层非均质性研究   总被引:7,自引:5,他引:2  
针对垂向非均质性严重且边底水能量强的番禺30-1气田面临的潜在开发问题,通过岩心分析及测井二次解释,对其夹层特征及储层非均质性等进行了研究,划分出19个流动单元并定量描述了各流动单元的特征参数,建立了该气田的精细地质模型。综合评价表明,新建的地质模型具有较高的精度,为该气藏合理开发提供了坚实的地质基础。  相似文献   
97.
涡轮搅拌桨反应器混合过程的数值计算   总被引:1,自引:1,他引:0  
利用CFD方法计算单层涡轮反应器搅拌槽内流体混合过程的速度场和浓度场,研究物料在搅拌槽内的混合过程,以及不同监测点对混合时间的影响。结果表明,搅拌槽内物料的混合主要受槽内流体的流动形式所影响;混合时间的长短与监测点位置有关;在搅拌桨的桨叶附近进行监测所得到的混合时间较短,在液面附近进行监测所得的混合时间较长。在实际生产和试验中,应注意对监测点位置的选取。  相似文献   
98.
降低成品油二次物流运输成本的思考   总被引:4,自引:0,他引:4  
介绍了传统成品油进货和管理模式存在的诸如成品油物流以行政区划、中问环节多、信息化程度不高、运输路线未优化造成物流成本提高等问题。提出要降低成品油二次物流运输成本,当务之急是加强成品油物流的信息化建设;调整管理模式,打破行政区域界限,开展经济辐射半径内的库站物流配送;引进竞争机制,打破运输垄断,一、二次物流结合,大、小车型搭配,提高运营效率;做好运杂费全面预算、核算及运行费用的过程控制。  相似文献   
99.
Reducing CIC filter complexity   总被引:1,自引:0,他引:1  
This paper provides several tricks to reduce the complexity and enhance the usefulness of cascaded integrator-comb (CIC) filters. The first trick shows a way to reduce the number of adders and delay elements in a multi-stage CIC interpolation filter. The result is a multiplierless scheme that performs high-order linear interpolation using CIC filters. The second trick shows a way to eliminate the integrators from CIC decimation filters. The benefit is the elimination of unpleasant data word growth problems.  相似文献   
100.
We perform a systematic measurement of the degree-of-polarization (DOP) and eye-closure penalty for optical signals with orthogonal polarizations. We find that the symmetry of DOP is maintained for the orthogonal polarizations under both first and higher order polarization-mode dispersion (PMD), whereas the symmetry of eye-closure penalty is broken under second-order PMD. An orthogonal polarization pair can have large disparity of eye-closure penalty despite an identical DOP. We also demonstrate a novel approach to estimate the maximum eye-closure penalty asymmetry with three orthogonal polarizations on the Poincare/spl acute/ sphere.  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