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   707篇
  免费   9篇
电工技术   22篇
化学工业   130篇
金属工艺   13篇
机械仪表   12篇
建筑科学   13篇
矿业工程   1篇
能源动力   19篇
轻工业   43篇
水利工程   3篇
石油天然气   3篇
无线电   114篇
一般工业技术   144篇
冶金工业   83篇
原子能技术   8篇
自动化技术   108篇
  2023年   8篇
  2022年   5篇
  2021年   14篇
  2020年   9篇
  2019年   15篇
  2018年   12篇
  2017年   10篇
  2016年   9篇
  2015年   13篇
  2014年   9篇
  2013年   54篇
  2012年   22篇
  2011年   39篇
  2010年   26篇
  2009年   36篇
  2008年   15篇
  2007年   25篇
  2006年   32篇
  2005年   31篇
  2004年   17篇
  2003年   14篇
  2002年   17篇
  2001年   8篇
  2000年   10篇
  1999年   12篇
  1998年   25篇
  1997年   20篇
  1996年   21篇
  1995年   11篇
  1994年   18篇
  1993年   11篇
  1992年   12篇
  1991年   11篇
  1990年   8篇
  1989年   7篇
  1988年   6篇
  1987年   6篇
  1986年   7篇
  1985年   7篇
  1984年   6篇
  1983年   5篇
  1982年   7篇
  1981年   6篇
  1980年   5篇
  1979年   7篇
  1978年   5篇
  1977年   7篇
  1976年   12篇
  1971年   5篇
  1970年   4篇
排序方式: 共有716条查询结果,搜索用时 31 毫秒
71.
The performance of a statistical multiplexer whose inputs consist of a superposition of voice packet streams is studied. The delay for such a system is analyzed by solving the ΣDi/ D/1 queue. The analytic method can be used to find the approximate mean delay for an arbitrarily large number of trunks and the approximate delay distribution when the number of trunks is less than 100. An efficient hybrid simulation of the packet voice multiplexer which can be used to find the delay distribution for a large number of trunks is presented. In addition, easily computable error bounds for the present approximation are provided, and the accuracy of the M/ D/1 approximation is investigated  相似文献   
72.
Emf measurements have been made in cells without liquid junction of the type H2/HX (m1), MXn(m2)/AgCl, Ag . . (I) containing mixtures of HCl and CaCl2 in different proportions, but at constant total ionic strength (I = 2, 1, 0.5). The measurements have been carried out at 5°C intervals over the temperature range 5–35°C. AgAgCl electrodes prepared by two different methods (thermal and thermoelectrolytic) were used of which the thermoelectrolytic electrodes were found to give more consistent results. The results when extrapolated properly lead to E° values at the different temperatures which agree well with those reported in literature. The application of the Pitzer method leads to the calculation of the ionic interaction coefficients α12 and α21, at the different constant ionic strengths. The nature of variation of these α's with the total mixture ionic strength at different temperatures has been considered.  相似文献   
73.
74.
Fatty acid and triglyceride compositions of the seed oil of Thea sinensis (tea seed oil) of Indian origin have been determined by combination of techniques of low temperature crystallisation, spectrophotometry, pancreatic lipase hydrolysis, thin-layer chromatography, gas–liquid chromatography and densitometry. Percentages of individual fatty acids were found to be: palmitic, 17.8; stearic, 3.0; oleic, 59.9; linoleic, 18.0. Triglyceride composition was calculated from the fatty acid compositions of the native oil and of the monoglycerides produced from it by pancreatic lipase hydrolysis. The oil is composed of 0.7, 11.1, 41.9 and 46.3% GS3, GS2U, GSU2 and GU3 respectively. Prominent features of the oil is its content of 11.6, 21.4 and 22.0% dioleolinolein, triolein and dioleopalmitin respectively.  相似文献   
75.
76.
A. Sengupta  S. P. Basu  S. Saha 《Lipids》1975,10(1):33-40
The fatty acid composition ofSapindus mukorossi seed oil was determined by spectrophotometry, urea complexation, and gas liquid chromatography (GLC). The percentages of individual acids were found to be: palmitic, 4.0; stearic, 0.2; arachidic, 4.4; oleic 62.8; linoleic, 4.6; linolenic, 1.6; and eicosenoic, 22.4. Triglyceride composition was calculated from the fatty acid compositions of the native oil and of the monoglycerides produced from it by pancreatic lipase hydrolysis. The oil is composed of 0.1, 2.1, 22.0, and 75.8% trisaturated, monounsaturated disaturated, diunsaturated monosaturated, and triunsaturated glycerides, respectively. The special characteristic of theSapindus mukorossi seed oil is its content of 26.3 and 26.7% triolein and eicoseno-di-oleins, respectively.  相似文献   
77.
A modification of an existing technique for thermistor linearization is presented. A temperature-measuring circuit using a thermistor in a specially designed pulse generator is used to obtain a highly linear relation between absolute temperature and frequency. The use of a general-purpose operational amplifier and two switching transistors in the design of the pulse generator provides a temperature scale that is linear over a wide range of values on a high degree of sensitivity. The result shows that an extremely high degree of linearity is achieved by this method  相似文献   
78.
Nimesulide is a newer non-steroidal anti-inflammatory drug (NSAID) with selective cyclo-oxygenase (COX)-2 blocking property and has demonstrated a potent analgesic and anti-inflammatory activity on oral and rectal administration. However, the Cmax through both these routes is reached only after 3 h of administration. Dose-dependent gastrointestinal side effects also limit the concentration of drug that can be achieved at the site of inflammation when administered through these routes. The present study was conducted to evaluate the antinociception induced by a new gel formulation of nimesulide when applied on the skin. Efficacy of topical nimesulide gel 1% (w/w) was studied on mice in the acetic-acid-induced writhing, tail flick latency (TFL) test and formalin-induced pain models. The antinociceptive effect of nimesulide was compared to diclofenac gel (1% w/w). Both the drugs induced dose-dependent analgesia with peak effect seen between 90 and 120 min after treatment. Greater antinociceptive effect (expressed as percent maximum possible effect) was seen in the writhing test than in the TFL test, indicating the peripheral action of both drugs. Nimesulide evidenced significant protection in the first phase of formalin-induced pain indicating modulation of peripheral nociceptors unlike other conventional NSAIDs. This suggests that COX-2 may be a primary contributor to afferent evoked increase in prostanoid-mediated changes in pain processing. Antinociception seen following drug application on the skin was lower than that seen on intraperitoneal administration, indicating localised action following topical application. The findings of the present study suggest that the transgel formulation of nimesulide provides significant analgesic activity when applied topically.  相似文献   
79.
This paper deals with the propagation of 2-dimensional waves in a thermo-elastic micropolar solid layer which can stretch and contract. Thermo-elastic Rayleigh wave velocity equation in the micropolar medium with stretch has been deduced from the above theory. The wave velocity equation obtained is in agreement with the classical result of Rayleigh when the layer is unstretched and thermal and micropolar effects are negligibly small.  相似文献   
80.
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