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   303篇
  免费   11篇
  国内免费   2篇
电工技术   28篇
化学工业   63篇
金属工艺   6篇
机械仪表   10篇
建筑科学   9篇
能源动力   8篇
轻工业   22篇
水利工程   1篇
无线电   26篇
一般工业技术   58篇
冶金工业   41篇
原子能技术   13篇
自动化技术   31篇
  2023年   2篇
  2022年   7篇
  2021年   5篇
  2020年   3篇
  2019年   3篇
  2018年   8篇
  2017年   6篇
  2016年   4篇
  2014年   4篇
  2013年   19篇
  2012年   11篇
  2011年   17篇
  2010年   8篇
  2009年   13篇
  2008年   21篇
  2007年   13篇
  2006年   12篇
  2005年   17篇
  2004年   10篇
  2003年   17篇
  2002年   4篇
  2001年   4篇
  2000年   6篇
  1999年   7篇
  1998年   15篇
  1997年   11篇
  1996年   8篇
  1995年   2篇
  1994年   7篇
  1993年   6篇
  1992年   3篇
  1991年   4篇
  1990年   1篇
  1989年   5篇
  1988年   4篇
  1987年   1篇
  1986年   3篇
  1985年   4篇
  1984年   3篇
  1983年   3篇
  1982年   2篇
  1978年   2篇
  1977年   3篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1972年   1篇
  1971年   1篇
  1968年   1篇
  1936年   1篇
排序方式: 共有316条查询结果,搜索用时 15 毫秒
121.
Singh A  Li X  Protasenko V  Galantai G  Kuno M  Xing HG  Jena D 《Nano letters》2007,7(10):2999-3006
Polarization-sensitive photodetectors are demonstrated using solution-synthesized CdSe nanowire (NW) solids. Photocurrent action spectra taken with a tunable white light source match the solution linear absorption spectra of the NWs, showing that the NW network is responsible for the device photoconductivity. Temperature-dependent transport measurements reveal that carriers responsible for the dark current through the nanowire solids are thermally excited across CdSe band gap. The NWs are aligned using dielectrophoresis between prepatterned electrodes using conventional optical photolithography. The photocurrent through the NW solid is found to be polarization-sensitive, consistent with complementary absorption (emission) measurements of both single wires and their ensembles. The range of solution-processed semiconducting NW materials, their facile synthesis, ease of device fabrication, and compatibility with a variety of substrates make them attractive for potential nanoscale polarization-sensitive photodetectors.  相似文献   
122.
This article focuses on the multi-attribute multi-item negotiation between multiple manufacturer agents (MAs) and multiple material supplier agents (MSAs). A coalition formation-based negotiation protocol is proposed. The MSAs are allowed to establish coalitions when the orders of the MAs exceed their abilities. Three attributes (price, quantity and lead time) of the items are considered during the negotiation. Both the MAs and the MSAs can give concessions among the attributes in tradeoff relationships according to their own preferences. The non-cooperative game is introduced to find the equilibria of the negotiations. The final allocation scheme is determined to maximise the total profit of the supply chain networks based on the equilibria. Simulations are provided to verify the effectiveness and feasibility of the proposed protocol.  相似文献   
123.
After the severe accident at the Fukushima-1 nuclear power plant, large amounts of contaminated stagnant water have accumulated in turbine buildings and their surroundings. This rapid communication reports calculation of the radionuclide inventory in the core, collection of measured inventory in the stagnant water, and estimation of radionuclide release ratios from the core to the stagnant water. This evaluation is based on data obtained before 3 June 2011. The release ratios of tritium, iodine, and cesium were several tens of percent, whereas those of strontium and barium were smaller by one or two orders of magnitude. The release ratios in the Fukushima accident were equivalent to those in the accident of the Three Mile Island, Unit 2 (TMI-2).  相似文献   
124.
在水与绿宽阔平缓变化地形中的休闲式运动公园,跨出了宜兰县环境绿化整备的第一步.我们对规划的重要考虑,在于要能反映当地的自然、人文、历史、风土及人们的生活需求,故在规划初期便展开台湾风土的调查之旅,并在草案阶段与县府人员检讨调整,进而导出上述的基本理念.本公园虽名为运动公园,但不同以往提供竞技比赛专用或培训选手为主的运动公园,而是提供居民在日常生活中轻松休闲的活动去处.是在丰富的绿色空间中晨昏时散步、晨间体操等活动的一个自由度大、供民众自由活动的空间.目前,在早上或傍晚时有很多人来运动、散步或徜徉在绿色的休闲气氛中,从使用现状可看出达成目标的成果.  相似文献   
125.
Carbon films were prepared on a Si wafer substrate by using a plasma-based ion implantation (PBII) technique. The homogeneity of the carbon films formed on the three-dimensional object and the influence of the duty ratio of the pulse bias tothe target on the property of the carbon films were investigated. The homogeneity of the carbon films formed on a convex face and that formed on a concave face by the incidence of the microwave to the target with a low angle of about — 30° wasalmost a constant. The application of the ECR plasma source, with a mirror field, to the PBII system was efficient enoughtoimprove the homogeneity, even though the plasma density was not very high. Diamond-like carbon films with a flat surface and a low friction coefficient can be formed by applying negative high-voltage pulses to a substrate with a low duty ratio of 1%.  相似文献   
126.
127.
ABSTRACT: A 2‐y carcinogenicity study of Aloe, Aloe arborescens Miller var. natalensis Berger, a food additive, was conducted for assessment of toxicity and carcinogenic potential in the diet at doses of 4% or 0.8% in groups of male and female Wistar Hannover rats. Both sexes receiving 4% showed diarrhea, with loss of body weight gain. The survival rate in the 4% female group was significantly increased compared with control females after 2 y. Hematological and biochemical examination showed increase of RBC, Hb, and Alb in the 4% males. The cause of these increases could conceivably have been dehydration through diarrhea. AST and Na were significantly decreased in the males receiving 4%, and Cl was significantly decreased in both 4% and 0.8% males. A/G was significantly increased in the 4% females, and Cl was significantly decreased (0.8%) in the female group. Histopathologically, both sexes receiving 4% showed severe sinus dilatation of ileocecal lymph nodes, and yellowish pigmentation of ileocecal lymph nodes and renal tubules. Adenomas or adenocarcinomas in the cecum, colon, and rectum were observed in 4% males but not in the 0.8% and control male groups. Similarly, in females, adenomas in the colon were also observed in the 4% but not 0.8% and control groups. In conclusion, Aloe, used as a food additive, exerted equivocal carcinogenic potential at 4% high‐dose level on colon in the 2‐y carcinogenicity study in rats. Aloe is not carcinogenic at nontoxic‐dose levels and that carcinogenic potential in at 4% high‐dose level on colon is probably due to irritation of the intestinal tract by diarrhea.  相似文献   
128.
The antimicrobial susceptibility of 144 Salmonella enterica serovar Typhimurium isolates collected from all over Japan between 1973 and 1998 were investigated. All the isolates exhibited resistance to four or more antimicrobials and 22 resistance patterns were observed. Isolates showing resistance patterns to ampicillin (A), chloramphenicol (C), streptomycin (S), sulfonamides (Su) and tetracycline (T), which are typical resistance patterns for S. Typhimurium DT104 (DT104), were predominant. Thirty-six of the 68 isolates that exhibited resistance to five or more antimicrobials (ACSSuT+) were identified as DT104 by phage typing. Another 103 S. Typhimurium strains gathered from cattle between 1977 and 1999 in a limited area of Japan were analyzed for molecular epidemiological studies. Results using fluorescent amplified-fragment length polymorphism and pulsed-field gel electrophoresis suggest that clonal exchange of S. Typhimurium among cattle in Japan has occurred since 1992, and that contemporary strains show a remarkable degree of homogeneity with DT104 at a molecular level. The clonal replacement by DT104 affected the antimicrobial resistance pattern of S. Typhimurium from cattle in Japan.  相似文献   
129.
Multi-walled carbon nanotube networks were confirmed to exhibit a linear decrease in resistivity with increasing temperature from 100 to above 400 K.The linearity was explained using a defect scattering model that involved Friedel oscillations(that is,electron-electron interactions).The applicability of this model,which was originally proposed for graphene,to carbon nanotubes was assessed based on a comparison of various experimental data.Increases in the slopes of the resistivity-temperature plots following the introduction of defects,as well as an effect of charge concentration on the slope were key predictions of this model.The results obtained from few-walled carbon nanotube networks are also shown.In the literature,linear resistivity-temperature plots were obtained from other graphene derivatives,indicating that the linearity originates from the hexagonal symmetry of these materials.The present work also indicated a relationship between the appearance of linearity and negative magnetoresistance above 100 K.Based on a mechanism incorporating scattering in association with Friedel oscillations and conventional electron conduction models,the universality of resistivity-temperature plots obtained from carbon nanotube networks is introduced.  相似文献   
130.
One of the most emphasized problems to be solved in power systems in recent years is the line‐current harmonics problem. This is due to the use of diode rectifiers, PWM converters, nonlinear loads, and so on. To reduce or eliminate such current harmonics, an active power filter (APF), which is a sophisticated power electronic converter, has been studied and used in some practical applications. In this paper, we propose and discuss two new control methods for three‐phase shunt APFs: the sinusoidal line‐current control method and the instantaneous‐reactive‐power compensation control method. They are based on pulsewidth prediction control, or a predictive‐instantaneous‐current PWM control. Neither any instantaneous power information nor coordinate transformation is necessary for control. In the sinusoidal line‐current control scheme, the controller governs the switching devices of the APF by using the pulse width that is optimally predetermined at the beginning of every switching period with the sinusoidal current reference. The line currents flow sinusoidally and are in phase with the voltage accordingly. In the instantaneous‐reactive‐power compensation control, the control is performed so that the resultant circuit of the load and the APF is regarded as a time‐variant conductance circuit model. The APF with this control scheme can cancel effectively the instantaneous reactive component produced by the load though the controller is simple. This paper discusses the performance characteristics of the APFs when a three‐phase diode rectifier and an unbalanced load are connected to the line. The practicability of the proposed methods is verified by experiment. © 1999 Scripta Technica, Electr Eng Jpn, 130(3): 68–76, 2000  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