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   157篇
  免费   0篇
电工技术   3篇
化学工业   26篇
金属工艺   1篇
机械仪表   4篇
建筑科学   3篇
能源动力   2篇
轻工业   1篇
无线电   16篇
一般工业技术   14篇
冶金工业   64篇
原子能技术   2篇
自动化技术   21篇
  2022年   1篇
  2020年   1篇
  2019年   1篇
  2017年   1篇
  2015年   4篇
  2014年   1篇
  2013年   5篇
  2012年   2篇
  2011年   10篇
  2010年   4篇
  2009年   5篇
  2008年   5篇
  2007年   7篇
  2006年   3篇
  2005年   3篇
  2004年   4篇
  2003年   3篇
  2002年   1篇
  2001年   2篇
  2000年   2篇
  1999年   3篇
  1998年   21篇
  1997年   15篇
  1996年   16篇
  1995年   11篇
  1994年   4篇
  1993年   7篇
  1992年   4篇
  1989年   2篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1980年   1篇
  1977年   1篇
  1975年   1篇
  1939年   1篇
  1938年   1篇
排序方式: 共有157条查询结果,搜索用时 15 毫秒
1.
2.
The tendency toward higher packing densities and higher frequencies for telecommunication devices based on ceramic technology requires smaller dimensions for electrical wiring. Electrical thick-film circuits for ceramic and LTCC-substrates have, up to now, been printed with screen printing, where the printing lines width limit is about 125 /spl mu/m in mass production. A silicone polymer direct gravure printing (Si-DGP) process has been developed to perform smaller dimensions, down to 20 /spl mu/m lines width, for electrical circuitry. In the DGP process, the conductor paste is doctored to the grooves of the gravure and then it is pressed against the substrate. The paste is, thus, printed directly onto the substrate from the patterned gravure. The results showed that, using the DGP process, it was possible to print conductor lines down to 20 /spl mu/m in width. It was also noted that a 100% transfer of paste from the grooves of the gravure could be obtained with commercial pastes using the silicone polymer gravure. A dried thickness of up to 28 /spl mu/m was measured for the narrowest lines. Also conductor lines printed by the Si-DGP method were embedded inside LTCC-module.  相似文献   
3.
Diphtheria antitoxin was determined in serum from 44 pregnant women, of whom 26 had received one injection of diphtheria toxoid during pregnancy. Their infants were vaccinated with a combined diphtheria-tetanus vaccine at 3, 5 and 12 months of age. This vaccination schedule has been used in Sweden since 1986, replacing the old schedule of vaccination at 3, 4.5 and 6 months of age originally designed for diphtheria-tetanus-pertussis vaccine, which had not been used after cessation of general vaccination against pertussis in 1979. Serum samples from the infants were obtained at 3, 7 and 18 months of age. After 2 injections infants of mothers with high antitoxin titers, > or = 0.1 IU/ml, tended to have lower antitoxin titers than infants of mothers with low antitoxin concentrations (P = 0.067). All children had, however, antitoxin above the minimum protective level of 0.01 IU/ml. Median antitoxin titers were 1.6 IU/ml in both groups after the third booster injection. Four infants of mothers who had been vaccinated during pregnancy and who had titers of > or = 0.4 IU/ml did not reach the 0.1 IU/ml level after 2 injections: all 4 responded with high antitoxin titers after the third dose. Thus all infants were primed by 2 doses of vaccine, irrespective of maternal antibody concentration. The repressive effect of maternal antibody on titers noted after 2 doses was no longer observed after the third, booster dose.  相似文献   
4.
Anti-reflective (AR) boundary conditions (BC) have been introduced recently in connection with fast deblurring algorithms, both in the case of signals and images. Here we extend such BCs to d dimensions (d ≥ 1) and we study in detail the algebra induced by the AR-BCs, with strongly symmetric point spread functions (PSF), both from a structural and computational point of view. The use of the re-blurring idea and the computational features of the AR-algebra allow us to apply Tikhonov-like techniques within O(n d log(n)) arithmetic operations, where n d is the number of pixels of the reconstructed object. Extensive numerical experimentation concerning 2D images and strongly symmetric PSFs confirms the effectiveness of our proposal.   相似文献   
5.
This scientific literature review focuses on the relation between nursing work and low-back problems. Its aim was to estimate the risk of physical, psychosocial, and work organizational exposure factors that may lead to low-back problems. In addition this paper reviews and evaluates reported ergonomic intervention, with the object of decreasing the prevalence and incidence of low-back problems among nurses. A considerable number of studies of nursing staff has shown the connection between lifts and transfers of patients on one hand and low-back problems on the other. Factors in nursing work that may be significant in this connection are staff density and work satisfaction. In this review the single individual factor that was indisputably related to low-back problems was "history of back problems". Prevention programs do not show unequivocally positive results. There is a great need to carry out prospective studies with preventive programs.  相似文献   
6.
A two-step exocytosis/endocytosis protocol was used in rat pancreatic acini to study membrane trafficking events at the apical plasma membrane (APM) as a function of extracellular pH. Exocytosis, as measured by cholecystokinin (CCK)-8-induced release of amylase into the incubation medium, was relatively insensitive to changes in extracellular pH from 5.5 to 9.0. In contrast, endocytosis, as measured by temperature-dependent uptake of horseradish peroxidase (HRP), was robust at pH values between 6.5 and 8.3 but abolished at acidic pH values of 5.5 to 6.0. Energy metabolism and cell viability were maintained during pH 6-induced cessation of HRP uptake, and the vesicular block could be reversed upon raising the luminal pH to 7.4. Histochemical and morphometric studies of HRP uptake examined by electron microscopy indicated that extracellular pH regulates endocytosis at the apical plasma membrane. At pH 6.0 in prestimulated cells, HRP uptake at the APM was abolished, and acinar lumen membranes remained markedly dilated with decreased density of microvilli and "arrested" exocytic images. At pH 7.4, HRP was taken up into endolysosomal structures within the Golgi complex, and acinar lumen membranes were contracted. Cleavage of GP2, a glycosyl phosphatidylinositol-anchored protein, was associated with the pH-dependent activation of HRP uptake. These studies demonstrate that acinar lumen pH regulates endocytic but not exocytic activity at the APM and suggest that alkalinization of the acinar lumen by duct cells is required for retrieval of exocytic membranes into the acinar cell via vesicular uptake mechanisms. The role of acid-base interactions within the acinar lumen provides a novel basis for understanding the cellular and luminal defects observed within the exocrine pancreas in cystic fibrosis.  相似文献   
7.
Starting from the scattering data, the initial-value problem for the focusing nonlinear Schrödinger equation is solved numerically by following the path of the inverse scattering transform. The numerical results of an extensive experimentation suggest that: (a) our method is very effective, whenever the scattering data are analytically known; (b) the split-step Fourier method is not really effective if the exact solution is not smooth enough.  相似文献   
8.
The aim of this study was to investigate whether there are differences in technique between young adults with and without musculoskeletal symptoms when using a mobile phone for texting and whether there are differences in muscle activity and kinematics between different texting techniques. A total of 56 young adults performed a standardised texting task on a mobile phone. Their texting techniques were registered using an observation protocol. The muscular activity in six muscles in the right forearm/hand and both shoulders were registered by surface electromyography and the thumb abduction/adduction and flexion/extension were registered using a biaxial electrogoniometer. Differences in texting techniques were found between the symptomatic and the asymptomatic group, with a higher proportion of sitting with back support and forearm support and with a neutral head position in the asymptomatic group. Differences in muscle activity and kinematics were also found between different texting techniques. The differences in texting technique between symptomatic and asymptomatic subjects cannot be explained by them having symptoms but may be a possible contribution to their symptoms. STATEMENT OF RELEVANCE: There has been a dramatically increased use of mobile phones for texting especially among young people during the last years. A better understanding of the physical exposure associated with the intensive use is important in order to prevent the development of musculoskeletal disorders and decreased work ability related to this use.  相似文献   
9.
The Farwell and Donchin P300 speller interface is one of the most widely used brain-computer interface (BCI) paradigms for writing text. Recent studies have shown that the recognition accuracy of the P300 speller decreases significantly when eye movement is impaired. This report introduces the GeoSpell interface (Geometric Speller), which implements a stimulation framework for a P300-based BCI that has been optimised for operation in covert visual attention. We compared the Geospell with the P300 speller interface under overt attention conditions with regard to effectiveness, efficiency and user satisfaction. Ten healthy subjects participated in the study. The performance of the GeoSpell interface in covert attention was comparable with that of the P300 speller in overt attention. As expected, the effectiveness of the spelling decreased with the new interface in covert attention. The NASA task load index (TLX) for workload assessment did not differ significantly between the two modalities. PRACTITIONER SUMMARY: This study introduces and evaluates a gaze-independent, P300-based brain-computer interface, the efficacy and user satisfaction of which were comparable with those off the classical P300 speller. Despite a decrease in effectiveness due to the use of covert attention, the performance of the GeoSpell far exceeded the threshold of accuracy with regard to effective spelling.  相似文献   
10.
Solid state reaction between U-7 wt.%Mo and Al 6061 alloys at 550 °C and 340 °C was characterized in chemical diffusion couples made by Friction Stir Welding. Results were obtained from optical and scanning electron microscopy, electron probe microanalysis and X-ray diffraction. At 550 °C the interaction layer in γU(Mo)/Al 6061 is formed by U(Al,Si)3 phase but when γU(Mo) cellular decomposition occurs, UAl3 and Al43Mo4U6 also appear in the interaction layer. At 340 °C the use of X-ray diffraction with synchrotron radiation made it possible to analyze the interaction layer. It was found that it is only formed by U3Si5 phase with its cell volume enlarged respect to the original one.  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