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   286篇
  免费   9篇
电工技术   13篇
化学工业   116篇
金属工艺   6篇
机械仪表   11篇
建筑科学   3篇
能源动力   14篇
轻工业   9篇
水利工程   1篇
石油天然气   1篇
无线电   17篇
一般工业技术   66篇
冶金工业   16篇
原子能技术   7篇
自动化技术   15篇
  2022年   3篇
  2021年   4篇
  2020年   3篇
  2019年   4篇
  2018年   6篇
  2017年   4篇
  2016年   4篇
  2015年   5篇
  2014年   3篇
  2013年   9篇
  2012年   16篇
  2011年   13篇
  2010年   10篇
  2009年   6篇
  2008年   20篇
  2007年   11篇
  2006年   10篇
  2005年   8篇
  2004年   9篇
  2003年   8篇
  2002年   8篇
  2001年   11篇
  2000年   12篇
  1999年   9篇
  1998年   11篇
  1997年   6篇
  1996年   3篇
  1995年   5篇
  1994年   9篇
  1993年   6篇
  1992年   4篇
  1991年   3篇
  1990年   6篇
  1989年   6篇
  1988年   3篇
  1987年   5篇
  1986年   3篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1982年   4篇
  1981年   6篇
  1979年   7篇
  1978年   2篇
  1977年   4篇
  1974年   1篇
排序方式: 共有295条查询结果,搜索用时 203 毫秒
41.
The patients with strabismus, including 8 with superior oblique paresis, 1 with inferior rectus paresis, and 1 with congenital constant exotropia, were examined with MR imaging at 1.5 tesla (T) or 0.5T with a surface coil. Abnormal findings of extraocular muscles were identified in 8 of the 10 patients and most of them were consistent with the clinical findings. Deviation of the optic nerves was noted in 5 patients. Coronal short repetition time (RT) and echo time (ET) images were used to measure the concerned extraocular muscles and the optic nerves. The differences in diameters between the concerned extraocular muscles of both the diseased and normal eyes were calculated. MR imaging is considered to be advantageous and can be favorably used to observe and measure the extraocular muscles and other intraorbital structures in patients with strabismus.  相似文献   
42.
Thirty-seven joints in 36 patients with a fractured carpal scaphoid were evaluated by three-phase bone scintigraphy. They were classified into two groups according to their progress. Some were in good clinical condition and some in a non-union condition. Increased blood flow in the radial arteries and ample perfusion on and around the scaphoid bones on blood flow images suggested a good clinical course. The activity and the effectiveness of remodeling correlated well with the degree of scaphoid uptake on blood pool images taken more than seven days after the injury. Scaphoid uptake was more localized or there was almost none on blood pool images in cases with nearly complete recovery while it was amply visualized on static images. Blood pool images were indispensable for analyzing lesions and evaluating the clinical course. Two typical findings of scaphoid fractures were found on both blood pool and static images. One was diffusely increased scaphoid uptake seen in cases with a good clinical course, and the other was decreased uptake at proximal fragments seen in cases with non-union. It is concluded that three-phase bone scintigraphy provides useful information for evaluating the process of scaphoid fractures which cannot be obtained by means of conventional bone scintigraphy.  相似文献   
43.
Poly(4-vinylpyridine)-grafted magnetic nanoparticles were prepared by the "graft to" method. Surface-modified magnetic particles are covered with a hydrophobic layer because it can be dispersed in organic solvents such as methanol, toluene, benzene, and chloroform, but not in water. Surface charge control with magnetic nanoparticles of various isoelectric point was achieved by quaternization of pyridyl groups, and the positively charged particles can be dispersed in water within a wide range of pH.  相似文献   
44.
The electrical design, characteristics, construction, and test results of a 170-kVA static power supply using 2500-V 600-A gate turn-off (GTO) thyristors developed for a wide range of electric railway applications are discussed. This power supply is principally composed of a thyristor chopper at an elementary frequency of 360 Hz and three-phase gate turn-off thyristor inverters in the form of a twelve-phase bridge configuration. It is capable of stabilizing a 60-Hz ac voltage and twelve-phase waveform. The bulk and weight of this power supply are ascribed to the avoidance of an inverter commutating circuit, which contains parasitic thyristors, capacitors, and inductances. The applied strategy is derived from the trend of the state of the art regarding switching cells and commuter trains.  相似文献   
45.
Women might experience modulation in their perception and cognition of colours and odours during the menstrual cycle, but how women's impressions of and correspondence between colours and odours differ according to the cycle changes remains unknown. Here, we experimentally examined women's performance of several tasks, including evaluation of impressions of colours and odours, matching/nonmatching of colours with odours, and identification of odours, comparing two phases: the beginning of menstruation and ovulation. The results showed that participants had similar impressions of colours and odours and made similar colour choices for odours in both the menstrual and ovulation phases, while “pleasant-unpleasant” impressions of colour and odour might vary according to the menstrual cycle. We found no significant differences in odour identification between the phases. The findings imply that hormonal changes during the menstrual cycle might affect “pleasant-unpleasant” impressions of colour and odour but not other features regarding impressions or crossmodal correspondence. In future studies, examination with a large number of participants is necessary.  相似文献   
46.
47.
H. Ishigaki  I. Kawaguchi 《Wear》1981,68(2):203-211
The vertical movement of the skid caused by surface irregularities introduces some error into the measured value of surface roughness parameters. A theoretical and experimental investigation into the negative effect of the skid on measuring accuracy is reported.The effect of the skid for unidirectional surface roughness is greater than that for non-directional surface roughness. The effect increases with increase in the tip radius of the skid. The influence of the distance between the skid and the stylus on the effect of the skid is small and an electrical high pass filter reduces the effect.  相似文献   
48.
Organic thin‐film transistors (OTFTs) can be fabricated via a wet process and have exceptionally high flexibility. Therefore, production using the roll‐to‐roll (RtoR) method is expected. We succeeded in developing a new OTFT wet fabrication process adaptable to the RtoR process. Utilizing the electroless plating method for wiring formation, all materials can be formed in a wet process and can be patterned using the photolithography process. In addition, we succeeded in fabricating OTFT on an A4‐type flexible substrate using RtoR direct imaging exposure system.  相似文献   
49.
Thermal oxidative degradation behavior of polypropylene (PP) with different tacticities was studied based on the activation energy (ΔE) data obtained by thermogravimetric analysis (TGA). The ΔE value showed a negative proportion to the content of meso pentad fraction (mmmm) in all of isotactic PP (iPP) samples, and that of syndiotactic PP sample considerably deviated from this negative proportion relationship. Since the value of mmmm was directly related to polymer chain conformation, the ΔE value was thought to have close connection with the concentration of 31 helix conformation in the iPPs. The ΔE changes would be caused by the competition between uni- and bimolecular hydroperoxide decomposition, which was controlled by concentration and character of conformations of PPs.  相似文献   
50.
It has been considered that the contribution of the vapor-phase reaction (VPR) to the global three-phase reaction rate may become much lower as the catalyst effectiveness factor approaches unity. In this study, the hydrogenation of 1-methylnaphthalene was performed as an example of slow reactions using a laboratory-scale trickle-bed reactor (TBR) at 583 K, 8.0 MPa. It was qualitatively confirmed that VPR contributed to the product yields in TBR even in this slow reaction system when the liquid velocity was low and the volatility of the liquid was high. Langmuir–Hinshelwood type kinetic equations were established for the vapor-phase reaction. The product yields in TBR neither be explained by liquid- vapor-phase kinetics without external effects, nor the conventional partial wetting model. Therefore, a partial wetting model considering the contribution of VPR was proposed where the catalyst bed composed of externally partial and internally complete wet particles, and completely dry particles was assumed. Using this model, the product yields in TBR were suitably explained.  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