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   221篇
  免费   4篇
电工技术   5篇
化学工业   45篇
金属工艺   8篇
机械仪表   3篇
建筑科学   3篇
能源动力   3篇
轻工业   9篇
无线电   36篇
一般工业技术   38篇
冶金工业   46篇
原子能技术   1篇
自动化技术   28篇
  2023年   1篇
  2022年   6篇
  2021年   6篇
  2020年   4篇
  2019年   4篇
  2018年   1篇
  2017年   1篇
  2016年   3篇
  2014年   9篇
  2013年   10篇
  2012年   10篇
  2011年   6篇
  2010年   8篇
  2009年   13篇
  2008年   11篇
  2007年   9篇
  2006年   5篇
  2005年   11篇
  2004年   4篇
  2003年   4篇
  2002年   3篇
  2001年   6篇
  2000年   5篇
  1999年   3篇
  1998年   21篇
  1997年   9篇
  1996年   4篇
  1995年   5篇
  1994年   7篇
  1993年   6篇
  1992年   2篇
  1991年   4篇
  1990年   6篇
  1989年   5篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1985年   1篇
  1984年   2篇
  1981年   1篇
  1978年   2篇
  1976年   2篇
  1968年   1篇
排序方式: 共有225条查询结果,搜索用时 0 毫秒
21.
An architecture for a nonvolatile RAM (NVRAM) suitable for high-density applications is described. In the cell, a dynamic RAM cell is merged into an EEPROM cell. A capacitor is constructed between the control gate and the drain diffusion layer of the FLOTOX-type EEPROM memory cell. The equivalent circuit in the dynamic RAM mode consists of two transistors and a capacitor, which eliminates a dummy cell. A dynamic RAM sense amplifier is used in both modes, and it works as a data latch when data are transferred between the dynamic RAM and the EEPROM. The process of the NVRAM is compatible with ordinary EEPROMs  相似文献   
22.
23.
24.
25.
26.
The following paper describes a mitral valve replacement (SJM 27 mm), the patch closure (EPTFE) of an ostium primum atrial septal defect and tricuspid annuloplasty (De Vega's method) in a 64-year-old female patient with an incomplete endocardial cushion defect and mitral stenosis. Surgery revealed thickened, mitral valve leaflets and the presence of a cleft, findings similar to those observed in case of rheumatic degeneration. Investigation of patient hemodynamics confirmed a diagnosis of Lutembacher syndrome and a lower with left ventricle volume. After surgery, the volume of left ventricle increased and the patients clinical course was uneventful.  相似文献   
27.
As the memory cell array of DRAM has been scaled down, inter-bit-line coupling noise has emerged as a serious problem. The signal loss due to this noise is estimated at about 40% of the signal amplitude in a polycide-bit-line 16-Mb DRAM with a technologically attainable scaling scheme. Twisted bit-line architectures to reduce or eliminate the noise are proposed and demonstrated by the soft-error rate improvement of a 1-Mb DRAM. The effective critical charge is improved by 35%, which is attributed not only to the improvement of the signal amplitude but also to the elimination of large coupling noise during the sensing operation. The impact of these twisted bit-line architectures from a scaling viewpoint is also examined, and they are shown to be promising candidates for overcoming the scaling problems of DRAMs  相似文献   
28.
Landmarks in the development of treatment of retinal detachment include the recognition of the significance of retinal breaks that resulted in the distinction between rhegmatogenous retinal detachment (RRD) and exudative retinal detachment, the development of indirect ophthalmoscopy and scleral depression that allow better visualization of the peripheral area of the retina and better identification of retinal breaks, the recognition of the need to seal all retinal breaks, and the realization that vitreous traction is the major underlying cause of retinal tears and RRD. Scleral buckling procedures combine retinopexy to provide a scar around retinal breaks to seal them and scleral indentation to neutralize vitreous traction; they provided the first effective treatment of RRD. As surgeons gained experience with scleral buckling, they became aware that some RRDs, particularly those with fixed folds and/or a funnel configuration, often could not be repaired using this approach. It was thought that excessive vitreous traction was at fault, and the condition was called "massive vitreous retraction."  相似文献   
29.
Hybrid copolymers with aluminum-organic moiety frameworks were successfully prepared by reacting aluminum tri-sec-butoxide with several organic diols. The compositions of the resulting copolymers were determined using IR spectroscopy, ICP, elemental analysis and CP/MASS 13C-NMR spectroscopy. The UV-VIS spectra of the copolymers were also obtained. ESR spectral examinations of the copolymers and ab-initio calculations of the copolymer models indicate that an electron transfer takes place from the organic moiety to the aluminum atom in the framework.  相似文献   
30.
A two-step electrodischarge machining method was proposed for fabricating microgrooves with varied cross-sections on hard materials. Firstly, tungsten tool electrodes were shaped by wire electrodischarge grinding, and then the resulting tool electrodes were used to electrodischarge machine microgrooves on stainless steel. Preliminary experimental results showed that, in the first step, a sharp tool electrode with surface roughness of 0.3 µmRa could be achieved, and the surface roughness of the resulting groove was 0.16 µmRa in the second step. Voltage strongly affects the machining speed. A high voltage (>70 V) was preferable for improving the material removal rate. However, significant tool wear took place when using a high condenser capacitance at high voltages. To suppress tool wear, a high voltage and a small capacitance should be used. As test pieces, microgrooves having rectangular, triangular, circular and semi-closed cross-sections were fabricated.  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