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   199篇
  免费   5篇
电工技术   2篇
化学工业   29篇
金属工艺   7篇
机械仪表   1篇
建筑科学   3篇
能源动力   3篇
轻工业   30篇
水利工程   2篇
无线电   24篇
一般工业技术   39篇
冶金工业   39篇
原子能技术   3篇
自动化技术   22篇
  2023年   2篇
  2021年   2篇
  2020年   1篇
  2019年   3篇
  2018年   2篇
  2017年   4篇
  2016年   3篇
  2015年   2篇
  2014年   2篇
  2013年   11篇
  2012年   13篇
  2011年   9篇
  2010年   6篇
  2009年   8篇
  2008年   11篇
  2007年   5篇
  2006年   5篇
  2005年   6篇
  2004年   2篇
  2003年   8篇
  2002年   10篇
  2001年   5篇
  2000年   5篇
  1999年   3篇
  1998年   16篇
  1997年   12篇
  1996年   6篇
  1995年   1篇
  1994年   3篇
  1993年   5篇
  1992年   2篇
  1990年   2篇
  1989年   5篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1976年   2篇
  1975年   3篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
  1967年   1篇
排序方式: 共有204条查询结果,搜索用时 0 毫秒
21.
22.
Up-to-date products and systems in industry want to offer many features at low production cost. Using a toolbox of components, individual systems with many variants are configured. Configurators using knowledge-bases with constraints fulfil those requirements. This has been shown with large industry applications.  相似文献   
23.
The diamondoids (nanodiamonds) diamantane and triamantane were selectively converted into diorganophosphinic acid chlorides by reacting them with phosphorus trichloride under Friedel–Crafts‐like conditions. The di‐diamondoid phosphinic acid chlorides were subsequently reduced with trichlorosilane to give the hitherto unknown corresponding di‐diamondoid phosphines. These diamondoid phosphinic acid chlorides and phosphines are of great utility as starting materials in organo‐element and coordination chemistry due to their extraordinary rigidity and steric bulk.  相似文献   
24.
25.
Fiducial markers are reference points used in the registration of image space(s) with physical (patient) space. As applied to interactive, image-guided surgery, the registration of image space with physical space allows the current location of a surgical tool to be indicated on a computer display of patient-specific preoperative images. This intrasurgical guidance information is particularly valuable in surgery within the brain, where visual feedback is limited. The accuracy of the mapping between physical and image space depends upon the accuracy with which the fiducial markers were located in each coordinate system. To effect accurate space registration for interactive, image-guided neurosurgery, the use of permanent fiducial markers implanted into the surface of the skull is proposed in this paper. These small cylindrical markers are composed of materials that make them visible in the image sets. The challenge lies in locating the subcutaneous markers in physical space. This paper presents an ultrasonic technique for transcutaneously detecting the location of these markers. The technique incorporates an algorithm based on detection of characteristic properties of the reflected A-mode ultrasonic waveform. The results demonstrate that ultrasound is an appropriate technique for accurate transcutaneous marker localization. The companion paper to this article describes an automatic, enhanced implementation of the marker-localization theory described in this article  相似文献   
26.
Parameters Influencing the Welding Force of Electric Contacts in Power Engineering . Main parameters influencing the accumulated frequency distribution of the welding force using bouncing contacts are: contact force, closing velocity, duration of bouncing, number of operations, testcurrent, phase displacement, frequency, moment of contact in relation to current zero at inductive load. The statistical distribution over a wide range of the values of the welding force is traced back on the relative position of the weldings on the surfaces of the contacts by means of a model. The influence of duration of bouncing, number of operations, contact force, opening velocity, value of test current and polarity on the welding force is described by accumulated frequency distribution plottings for various contact materials when making contact synchronous- and asynchronously.  相似文献   
27.
28.
The formation of complexes of uranyl and neptunyl (VI) ions with carbonate and hydrogen carbonate has been studied by titration microcalorimetry. The measurements were carried out with a computer-controlled microcalorimeter which is described in detail. Sample volumes are typically in the range of 1.5 to 2.5 ccm, containing about 0.05 millimole of the ionic species to be studied. The small volume renders the calorimeter useful for the measurement of uncommon and strongly radioactive substances.Enthalpies of reaction were obtained for the formation of the dicarbonato and the tricarbonato uranyl ions in a sulfate medium of ionic strength 1.6. The enthalpies are ΔH2 = ?39.6 ± 1 kJ/mol and ΔH3 = ?57.5 ± 1.5 kJ/mol, for the dicarbonato- and the tricarbonato-uranyl ions, respectively. The titration data for the neptunyl (VI) — carbonate system yield a value of ΔHNp ?50 ± 2 kJ/mol for the tricarbonato-neptunyl ion when interpreted in analogy to the uranyl system.  相似文献   
29.
30.
Relationship between udder and leg hygiene scores and subclinical mastitis   总被引:2,自引:0,他引:2  
The objective of this study was to determine the relationship between udder and leg hygiene scores of lactating dairy cattle and measures of subclinical mastitis. Study animals (n = 1250) consisted of lactating dairy cows from eight commercial dairy farms. Herds were enrolled during December 2000 and January 2001 and were visited bimonthly for a total of five visits per herd. Udder and leg hygiene scores were recorded by one person using a four-point scale ranging from one (very clean) to four (very dirty). Udder and leg hygiene scores were compared to bacteriological cultures of milk samples and monthly individual SCC values. Mean hygiene scores were 2.09 and 2.33 for udders and legs, respectively. Udder hygiene scores (UHS) were significantly associated with leg hygiene scores and varied among farms. Linear somatic cell scores increased as udder hygiene score increased. Significant differences in somatic cell scores were observed for all contrasts of udder hygiene score, except between scores of 1 and 2 and of 3 and 4. Linear somatic cell scores were associated with leg hygiene scores, but the only significant contrast was between leg hygiene scores of 2 and 4. There was a significant association between the prevalence of intramammary contagious pathogens and udder hygiene score. The prevalence of intramammary environmental pathogens was significantly associated with udder hygiene score and was 7.7, 10.0, 10.6, and 13.5% for UHS of 1, 2, 3, and 4, respectively. The prevalence of environmental pathogens was not associated with LHS. Cows with udder hygiene scores of 3 and 4 were 1.5 times more likely to have major pathogens isolated from milk samples compared with cows with hygiene scores of 1 and 2.  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