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   573篇
  免费   14篇
  国内免费   3篇
电工技术   25篇
化学工业   96篇
金属工艺   42篇
机械仪表   17篇
建筑科学   4篇
矿业工程   1篇
能源动力   28篇
轻工业   51篇
水利工程   3篇
无线电   90篇
一般工业技术   87篇
冶金工业   110篇
原子能技术   14篇
自动化技术   22篇
  2023年   1篇
  2022年   15篇
  2021年   16篇
  2020年   3篇
  2019年   9篇
  2018年   6篇
  2017年   9篇
  2016年   8篇
  2015年   6篇
  2014年   13篇
  2013年   23篇
  2012年   18篇
  2011年   31篇
  2010年   19篇
  2009年   32篇
  2008年   28篇
  2007年   19篇
  2006年   8篇
  2005年   14篇
  2004年   13篇
  2003年   10篇
  2002年   7篇
  2001年   11篇
  2000年   14篇
  1999年   17篇
  1998年   43篇
  1997年   29篇
  1996年   28篇
  1995年   12篇
  1994年   21篇
  1993年   17篇
  1992年   10篇
  1991年   10篇
  1990年   5篇
  1989年   5篇
  1988年   5篇
  1987年   5篇
  1986年   6篇
  1985年   4篇
  1984年   4篇
  1983年   6篇
  1982年   3篇
  1981年   8篇
  1980年   6篇
  1979年   5篇
  1978年   3篇
  1977年   1篇
  1976年   2篇
  1971年   1篇
  1970年   1篇
排序方式: 共有590条查询结果,搜索用时 15 毫秒
31.
We joined aluminum alloy A5052 to cold-rolled steel SPCC (Steel Plate Cold Commercial) and austenitic stainless steel SUS304 using resistance spot welding with a cover plate. The interfacial microstructure was observed using transmission electron microscopy. A thick two-layered reaction layer contains Fe2Al5 and FeAl3 and a thin serration reaction layer contains Fe2Al5 and FeAl3 were observed at the A5052/SPCC and A5052/SUS304 interface, respectively. Mechanical property analysis suggested that the reaction layer has no effect on the tensile shear strength of the A5052/SUS304 joint and that the tensile shear strength of the A5052/SPCC joint is influenced by the reaction layer formed at its interface.  相似文献   
32.
The daily variation in an intensity of kaolin-induced writhing reaction was examined in mice kept under conditions of light; 07:00 - 19:00 and dark; 19:00 - 07:00. The number of writhes was counted for 30 minutes after a single intraperitoneal injection of kaolin at 00:00, 02:00, 04:00, 06:00, 08:00, 10:00, 12:00, 14:00, 16:00, 18:00, 20:00 and 22:00. The number of writhes showed a daily variation with a peak at 18:00 and a trough at 06:00. The intensity of writhing reaction was significantly reduced by pretreatment with the bradykinin B1 (Des-Arg9-[Leu8]-BK) and B2 (icatibant) receptor antagonists. Significant daily variation in this parameter was still observed in the group with the B1 antagonist, but disappeared in the B2 antagonist-treated group. These results suggest that the kaolin-induced writhing reaction shows the daily variation with a peak at the end of the resting period and a trough at the end of the active period. The B2 receptor mediated stimuli appears to be involved in this phenomenon.  相似文献   
33.
It is by now familiar that in the deployment of solar photovoltaic (PV) systems, the cost dynamics of major system component like solar cell/module is subjected to experience curve effects driven by production learning and research and development at the supplier side. What is less clear, however, is the economics of system integration or system deployment that takes place locally close to the user, involving other market players, in the downstream solar PV value chain. Experts have agreed that suppliers of solar PV system must customize their flexible characteristics to address local unique users’ and applications requirements and compete on price/performance basis. A lack of understanding of the drivers of the economics of system customization therefore is a deficiency in our understanding of the overall economics of this renewable energy technology option.  相似文献   
34.
Mesoporous carbon thin films with ordered structures were prepared by using resorcinol-surfactant self-assembly. A mixture of resorcinol, surfactant, and ethanol coated on silicon substrates was exposed to formaldehyde vapor as a cross-linking agent to form structured resorcinol/formaldehyde resin films. The films were then carbonized at 800 °C in an inert atmosphere to remove the surfactant and to obtain structured carbon materials. With this vapor infiltration method, thin films with several structures were obtained from the same precursor solution by employing different vapor infiltration temperatures. The results were interpreted from the transformation of the self-assembly during the vapor infiltration process.  相似文献   
35.
A new high repetition rate Nd:YAG Thomson scattering system is developed for the Heliotron J helical device.A main purpose of installing the new system is the temporal evolution measurement of a plasma profile for improved confinement physics such as the edge transport barrier (H-mode) or the internal transport barrier of the helical plasma.The system has 25 spatial points with ~10mm resolution.Two high repetition Nd:YAG lasers (>550mJ@ 50Hz) realize the measurement of the time evolution of the plasma profile with ~10ms time intervals.Scattered light is collected by a large concave mirror (D=800 mm,f/2.25) with a solid angle of ~100 mstr and transferred to interference filter polychromators by optical fiber bundles in a staircase form.The signal is amplified by newly designed fast preamplifiers with DC and AC output,which reduces the low frequency background noise.The signals are digitized with a multi-event QDC,fast gated integrators.The data acquisition is performed by a VME-based system operated by the CINOS.  相似文献   
36.
Hot carrier magnetophonon resonances of n-type Si, short channel InP and p-type InSb were investigated in pulsed high magnetic fields up to 40 T. Using a recently developed high resolution technique in pulsed high fields, many new features of the hot carrier-phonon interactions in high magnetic fields were found.  相似文献   
37.
38.
39.
40.
An algorithm for measuring an index of leakage in fluorescein fundus angiography is presented. The number of pixels whose gray level exceeds an automatically determined slice level is calculated. An automatic blood vessel elimination technique is introduced. Further, a method of measuring the short term change of leakage from a time series of the fluorescein fundus angiographs is described. Our system can also deal with the time series images obtained on different occasions (long term change).The features of this paper are: (1) this paper deals with double time sequence images (short and long term); (2) an automatic blood vessel recognition algorithm is employed.  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