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   445篇
  免费   12篇
  国内免费   2篇
电工技术   8篇
综合类   3篇
化学工业   98篇
金属工艺   8篇
机械仪表   5篇
建筑科学   12篇
矿业工程   9篇
能源动力   14篇
轻工业   27篇
石油天然气   3篇
无线电   46篇
一般工业技术   48篇
冶金工业   121篇
原子能技术   5篇
自动化技术   52篇
  2019年   4篇
  2017年   4篇
  2016年   9篇
  2015年   5篇
  2014年   7篇
  2013年   25篇
  2012年   12篇
  2011年   7篇
  2010年   11篇
  2009年   29篇
  2008年   14篇
  2007年   20篇
  2006年   20篇
  2005年   24篇
  2004年   22篇
  2003年   19篇
  2002年   11篇
  2001年   10篇
  2000年   11篇
  1999年   7篇
  1998年   11篇
  1997年   10篇
  1996年   6篇
  1995年   6篇
  1994年   11篇
  1993年   4篇
  1992年   6篇
  1990年   6篇
  1989年   3篇
  1988年   5篇
  1987年   4篇
  1986年   12篇
  1985年   10篇
  1984年   4篇
  1983年   11篇
  1982年   6篇
  1981年   8篇
  1979年   4篇
  1978年   4篇
  1977年   4篇
  1976年   9篇
  1975年   2篇
  1974年   5篇
  1972年   3篇
  1971年   4篇
  1970年   4篇
  1969年   3篇
  1967年   4篇
  1966年   3篇
  1965年   6篇
排序方式: 共有459条查询结果,搜索用时 62 毫秒
1.
2.
3.
4.
Fish silage was prepared from 96.5% offal obtained from Atlantic cod fillet processing and 3.5% (by wt) formic acid. The fish silage became an homogeneous liquid of low viscosity in 36–58 h at 20°C; however, the oil and protein components continued to be hydrolysed for several months. Addition of formaldehyde to fish silage (0.25 or 0.39% by wt) after liquefaction was complete, served to prevent continued protein hydrolysis and oxidative rancidity of the oil. It also decreased the development of ‘off-odours’, and the formation of total volatile bases. Fish silage was readily absorbed by hay at a ratio of 1.5 parts silage to 1.0 parts hay by weight; the product is referred to as ‘haylage’. Voluntary intake by wethers of ‘haylage’ prepared from de-oiled, formaldehyde-treated fish silage was better than for ‘haylage’ prepared from untreated fish silage. The crude protein content of ‘haylage’ rations was more than satisfactory for fattening lambs, although the energy content of ‘haylage’ rations may be a limiting factor. Retention of fish oil in the silage to increase the energy content of rations was unsuccessful because voluntary feed intake was depressed. The addition of formaldehyde to fish silage is advantageous when the product is to be fed to ruminant livestock since protein and lipid degradation in the feed, and also possibly in the rumen, are minimised and voluntary intake of ‘haylage’ by sheep is increased.  相似文献   
5.
6.
This paper reports the results of a pilot study conducted to determine whether there is a relationship between simulator sickness and measures of driver inputs, vection, and postural sway, in a fixed base driving simulator. Seven males and four females performed a series of alternating left and right turns (20 each), with straigth-aways inbetween. The task was designed to promote experiences of circular and linear vection, and associated sway. It was hypothesized that greater driver inputs (i.e., steering wheel and braking activity; deviation from the centerline) would correlate: with reports of vection and measures of postural sway. Ten of the eleven subjects reported moderate sickness, which precluded any statistical comparisons between “sick” and “not sick” however, there was a significant tendency for persons who reported vection to also report sickness. There were no gender differences in reported incidence of vection or sickness, however, males tended to exhibit greater lateral velocity. The next phase of investigation will necessitate reducing the strength of the stimulus (i.e., require less turns) to increase variability of sickness scores amongst subjects and permit comparisons between “sick” and “not sick.” Measurement considerations include increasing the sensitivity of vection ratings, and examination of the timecourse for the development of postural sway.  相似文献   
7.
Data from 296 sibling pairs (mean ages 10 and 13 years), their primary caregivers, and census records were used to test the hypothesis that African American children's likelihood of developing conduct problems associated with harsh parenting, a lack of nurturant-involved parenting, and exposure to an older sibling's deviance-prone attitudes and behavior would be amplified among families residing in disadvantaged neighborhoods. A latent construct representing harsh-inconsistent parenting and low levels of nurturant-involved parenting was positively associated with younger siblings' conduct disorder symptoms, as were older siblings' problematic attitudes and behavior. These associations were strongest among families residing in the most disadvantaged neighborhoods. Future research and prevention programs should focus on the specific neighborhood processes associated with increased vulnerability for behavior problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
8.
The neutron spectra transmitted across a fission-suppressed hybrid blanket and its components, driven by a low intensity 14 MeV Haefely neutron generator, were measured with a 2×2 NE213 detector at LOTUS facility. These experiments have been analyzed with 2D and 3D codes DOT3.5 and MCNP, respectively. The spectral integrals between 15 to 1 MeV show good agreement among the 2D, the 3D, and the NE213 for 15 cm lead, 18 cm beryllium, and 25 cm graphite slabs. However, there are large discrepancies for 6.2 cm stainless steel and 15 cm lithium carbonate slabs. The assemblies involving two or more of these slabs reflect these tendencies. We observe also considerable disagreement over pointwise spectra for a number of assemblies.Work done while on visiting assignment to Institut de Génie Atomique, E.P.F.L.  相似文献   
9.
New microporous hybrid organic/inorganic materials were obtained by modification of zeolites using chlorination of their surface, followed by treatment with a Grignard reagent. Loading of butyl groups and retained crystallinity of ZSM-5 type zeolites was higher than for zeolites Y. In contrast to zeolites Y, the lattice parameters of zeolites ZSM-5 increased after surface modification. The obtained hybrid materials on the basis of high-silica zeolites possess a high degree of crystallinity at increased hydrophobicity.  相似文献   
10.
A polystyrene (PS)/poly(butyl acrylate) (PBA) composite emulsion was produced by seeded emulsion polymerization of butyl acrylate (BA) with PS seed particles which were prepared by emulsifier‐free polymerization of styrene with potassium persulfate (KPS) under a nitrogen atmosphere at 70°C for 24 h with stirring at 60 rpm and swelled with the BA monomer in an ethanol/water medium. The structure of the PS/PBA composite particles was confirmed by the presence of the characteristic absorption band attributed to PS and PBA from FTIR spectra. The particles for pure PS and PS/PBA with a low content of the BA monomer were almost spherical and regular. As the BA monomer content was increased, the particle size of the PS/PBA composite particles became larger, and more golf ball‐like particles were produced. The surface morphology of the PS/PBA composite particles was investigated by AFM and SEM. The Tg's attributed to PS and PBA in the PS/PBA composite particles were found at 110 and ?49°C, respectively. The thermal degradation of the pure PS and PS/PBA composite particles occurred in one and two steps, respectively. With an increasing amount of PBA, the initial thermal decomposition temperature increased. On the contrary the residual weight at 450°C decreased with an increasing amount of PBA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 595–601, 2003  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