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   4743篇
  免费   46篇
  国内免费   3篇
电工技术   21篇
综合类   2篇
化学工业   342篇
金属工艺   76篇
机械仪表   43篇
建筑科学   92篇
矿业工程   10篇
能源动力   31篇
轻工业   195篇
水利工程   9篇
石油天然气   24篇
无线电   241篇
一般工业技术   361篇
冶金工业   3059篇
原子能技术   18篇
自动化技术   268篇
  2021年   24篇
  2019年   20篇
  2018年   19篇
  2016年   30篇
  2015年   24篇
  2014年   36篇
  2013年   101篇
  2012年   53篇
  2011年   60篇
  2010年   70篇
  2009年   71篇
  2008年   80篇
  2007年   78篇
  2006年   76篇
  2005年   53篇
  2004年   58篇
  2003年   64篇
  2002年   64篇
  2001年   42篇
  2000年   58篇
  1999年   127篇
  1998年   882篇
  1997年   483篇
  1996年   325篇
  1995年   171篇
  1994年   202篇
  1993年   197篇
  1992年   65篇
  1991年   68篇
  1990年   89篇
  1989年   70篇
  1988年   83篇
  1987年   74篇
  1986年   59篇
  1985年   45篇
  1984年   37篇
  1983年   47篇
  1982年   42篇
  1981年   35篇
  1980年   63篇
  1979年   37篇
  1978年   35篇
  1977年   71篇
  1976年   151篇
  1975年   32篇
  1974年   14篇
  1972年   19篇
  1971年   14篇
  1970年   21篇
  1969年   12篇
排序方式: 共有4792条查询结果,搜索用时 13 毫秒
11.
Abstract The SelfSpell programs provide a multi-media environment for dyslexic children which uses synthesised speech to augment the written text. In earlier research we established that by encouraging users to enter a rule to help them remember how to spell each word, SelfSpell was very effective in improving spelling ability. The evaluation study reported here confirmed the efficacy of the rule-based approach using a group of 11-year-old dyslexic children with severe impairments in spelling. Of particular theoretical significance, however, was the finding that use of a mastery learning technique for learning spellings was just as effective as the rule-based approach. These findings are interpreted in the light of Frith's influential framework for the development of reading and spelling ability. It is suggested that the multimedia presentation approach may provide a uniquely effective method for helping dyslexic children to acquire the 'alphabetic' stage of linguistic processing.  相似文献   
12.
The behavior during creep in shear of eutectic indium-tin joints on copper and nickel substrates was examined in order to determine the effect of creep deformation on the microstructure of the alloy. Primary creep was absent in all the samples tested. The stress exponent at 20° C was much higher for samples on nickel than for those on copper, indicating a different creep deformation mechanism. Also, the microstructure within the indium-tin joints differed significantly with a change of substrate. Samples with a nickel substrate showed a colony microstructure that was not observed in those with a copper substrate. Thus, eutectic morphology is important in determining deformation mechanism during creep. The microstructure within the joints in tested and untested regions of the samples was effectively the same. This is quite distinct from the behavior of eutectic lead-tin observed in previous work. Lead-tin formed a recrystallized band of material along a region of concentrated shear deformation. While the deformation pattern in the indium-tin samples appeared to be the same as for lead-tin, the microstructural changes did not occur. This implies that the behavior observed in lead-tin is not universal to eutectic alloys.  相似文献   
13.
14.
15.
16.
Hardenability is one of the most important parameters controlling the heat treated properties of engineering steels. It affects the consistency of response for microstructure, hardness, strength, toughness, and dimensional change (distortion). This study illustrates that a major benefit of controlling hardenability is improving the consistency of dimensional distortion resulting from heat treatment. To facilitate the supply of steels to hardenability limits, especially restricted hardenability, a new technique was developed for the prediction of Jominy hardenability from chemical composition. The technique, termed the “Database Method,” uses measured Jominy hardenability and chemical composition data, contained in a database, to calculate the hardenability for a query composition. Using up to ten known steels, selected from the database with compositions closely matching that of the query steel, a small adjustment is made to the measured hardenability of each known steel allowing for the small difference in composition between the query and chosen steel. The final calculated result for the query steel is taken as the average of the various estimates. The basis of the Database Method is explained, and the advantages are illustrated for selecting engineering grades.  相似文献   
17.
An explicit finite difference scheme is proposed for nonlinear convective problems. The procedure is applied to a nonlinear convective diffusion problem with a nonlinear boundary condition. It is shown that the nonlinear boundary condition may be treated directly without linearization which has to be carried out in the implicit method to avoid a nonlinear system of algebraic equations. The explicit procedure is more direct and less cumbersome than the implicit procedure and the answers are in excellent agreement with those of the implicit method.  相似文献   
18.
The VIrtual Planning Test (VIP) was developed to investigate the planning and organisational abilities of 25 patients with frontal lobe neurosurgical lesions, comparing their performance with 25 matched control subjects. The task, presented in the form of a board game, simulates planning and execution of a set of target activities that have to take place over a four day period, involving those that are either preparatory for a fictional "trip" abroad, or those that relate to the subject's current environment (context). The frontal lobe patients were impaired overall, tending to select inappropriate activities associated with their current context and showing greater impairment on subtasks requiring only one, rather than two, preparatory acts. The findings are discussed in terms of the validity of the VIP test in identifying executive functioning impairment and the degree to which the pattern of deficits are consistent with neuropsychological models of executive function.  相似文献   
19.
Prophylactic efficacy of tilmicosin for bovine respiratory tract disease   总被引:3,自引:0,他引:3  
The prophylactic administration of injectable tilmicosin for pneumonia in weaned beef calves was investigated in 1,806 animals. Comparisons were made among calves receiving an "on-arrival" injection of tilmicosin, calves receiving a single injection of long-acting oxytetracycline, and calves receiving no prophylaxis. Morbidity and mortality attributable to pneumonia, morbidity and mortality attributable to all causes, and case fatality were significantly lower in the group of calves that received tilmicosin, compared with calves that received long-acting oxytetracycline and calves that received no prophylactic antibiotic. Mean time to initial pneumonia treatment was significantly extended in calves that received prophylaxis, compared with those that received no antibiotic on arrival at the feedlot. Calves that received tilmicosin gained significantly more weight than calves that received oxytetracycline. Calves that were not treated for pneumonia during the trial period gained significantly more weight than did those calves that were treated for pneumonia regardless of experimental group. The majority of mortalities were attributable to fibrinous pneumonia (31/34). Important bacterial isolates (Pasteurella spp, Haemophilus somnus, Actinomyces pyogenes) obtained at necropsy did not have resistance to tilmicosin in association with administration of tilmicosin as prophylaxis for pneumonia. However, bacterial resistance to trimethoprim/sulfonamide and to oxytetracycline were commonly found in these postmortem isolates.  相似文献   
20.
Fizeau wavemeter for pulsed laser wavelength measurement   总被引:1,自引:0,他引:1  
  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