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   370篇
  免费   30篇
  国内免费   1篇
电工技术   3篇
化学工业   154篇
金属工艺   5篇
机械仪表   12篇
建筑科学   9篇
矿业工程   1篇
能源动力   9篇
轻工业   83篇
水利工程   1篇
石油天然气   2篇
无线电   13篇
一般工业技术   45篇
冶金工业   39篇
自动化技术   25篇
  2023年   4篇
  2022年   17篇
  2021年   23篇
  2020年   8篇
  2019年   13篇
  2018年   9篇
  2017年   11篇
  2016年   15篇
  2015年   14篇
  2014年   20篇
  2013年   28篇
  2012年   27篇
  2011年   32篇
  2010年   12篇
  2009年   13篇
  2008年   13篇
  2007年   12篇
  2006年   11篇
  2005年   11篇
  2004年   12篇
  2003年   14篇
  2002年   11篇
  2001年   4篇
  1999年   4篇
  1998年   5篇
  1997年   2篇
  1996年   5篇
  1995年   4篇
  1994年   3篇
  1993年   2篇
  1992年   6篇
  1991年   1篇
  1990年   2篇
  1989年   4篇
  1987年   3篇
  1986年   4篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1982年   3篇
  1979年   1篇
  1978年   2篇
  1975年   1篇
  1974年   1篇
  1972年   1篇
  1970年   1篇
  1965年   1篇
  1964年   1篇
  1963年   1篇
  1960年   2篇
排序方式: 共有401条查询结果,搜索用时 62 毫秒
1.
2.
3.
In a series of 10-day pair feeding experiments it was found that the nutritional value of diets containing beans was essentially the same for rats aged between 30 and 123 days. Thus net protein utilisation (NPU) values of 25–39 on diets containing Processor bean (35 g protein kg?1) + egg albumin (65g protein kg?1) were obtained. As food intakes were considerably reduced when rats were fed diets containing more than 35g protein kg?1 of Processor bean, the measurement of protein utilisation became increasingly more difficult. The severe disruption of the brush borders of duodenal and jejunal enterocytes, originally observed when bean-containing diets were fed to young (30-day-old) rats was also found with rats up to the age of 120 days on similar diets. Similarly, the development of circulating anti-lectin antibodies in the animals showed no age dependence within the age limits investigated. It was also shown that oral immunisation did not protect the rats from the effects of toxicity and that the immune response was a result of continuous absorption of lectin throughout the feeding period. Thus the extent and the mechanism of toxicity of Phaseolus vulgaris bean lectins were found not to be dependent on the age or maturity of the animal.  相似文献   
4.
Gamma-ray irradiations induced various alterations in sulfur- and selenium-based chalcogenide glasses. The absorbed dose was in the range of 0.01–3.6 MGy. The glasses exhibit prominent sensitivity to γ-ray irradiation, characterized by changes in some of the physical properties of the glasses, e.g., optical transmission, optical band gap, density, and thermal expansion coefficient. The effects on glass structure and microscopic morphology were also studied by Raman spectra and scanning electron microscopic observations.  相似文献   
5.
The authors report on the viscoelastic characterization of guar hydrogels obtained through complexation reactions with borax ions. These gels are compared with hydrogels obtained from poly(vinyl alcohol) of different degree of hydrolysis through complexation reactions with congo red. The effect of the degree of hydrolysis and both, the concentration of PVA and the concentration of congo red, on the viscoelastic properties of the hydrogels is analyzed. The potential use of the PVA‐based hydrogels as hydraulic fracturing liquids is discussed in relation to the commonly used fracturing liquid based on the guar–borax system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   
6.
Process capability indices (PCIs) are used in industry to assess percentages of nonconforming parts. An underlying assumption is that the output process measurements are distributed as normal random variables. When normal distributions are assumed, but different distributions are present - such as skew, heavy-tailed, and short-tailed distributions - the percentages of nonconforming parts are significantly different than the computed PCIs indicate. Data arising from nonnormal distributions can sometimes be transformed to conform to the normality assumption and the PCI's computed for the transformed data. In this paper, the effect of the transformation on the estimate of nonconforming parts is examined for three examples of nonnormal distributions - gamma, lognormal, and Weibull. The results of this experimental analysis suggest that data transformation can be useful for estimating an interval for Cpk values and the number of nonconforming parts.  相似文献   
7.
Linear polyethers possess unusually high CO2 solubility and, hence, selectivity due to the presence of accessible ether linkages that can interact with the quadrupolar moment of CO2 molecules. In this work, membranes derived from crosslinked poly(propylene glycol) diacrylate (PPGda) oligomers differing in molecular weight (M), as well as PPGda nanocomposites containing either an organically-modified montmorillonite clay or a methacrylate-terminated fumed silica are investigated and compared with highly CO2-selective poly(ethylene glycol) diacrylate (PEGda) homopolymer and nanocomposite membranes previously reported. The rheological and permeation properties of PPGda depend sensitively on M, with the elastic modulus decreasing, but CO2 permeability and CO2/H2 selectivity increasing, with increasing M. Incorporation of either nanofiller into PPGda enhances the elastic modulus and reduces the gas permeability in the resultant nanocomposites without strongly affecting CO2/H2 selectivity. Blending PPGda and PEGda prior to chemical crosslinking yields binary membranes that exhibit intermediate gas-transport properties accurately described by a linear rule of mixtures.  相似文献   
8.
The EU‐funded project UAN (Underwater Acoustic Network) was aimed at conceiving, developing, and testing at sea an innovative and operational concept for integrating underwater and above‐water sensors in a unique communication system to protect offshore and coastline critical infrastructures. This work gives details on the underwater part of the project. It introduces a set of original security features and gives details on the integration of autonomous underwater vehicles (AUVs) as mobile nodes of the network and as surveillance assets, acoustically controlled by the command and control center to respond against intrusions. Field results are given of the final UAN project sea trial, UAN11, held in May 2011 in Norway. During the experimental activities, a UAN composed of four fixed nodes, two AUVs, and one mobile node mounted on the supporting research vessel was operated continuously and integrated into a global protection system. In this article, the communication performance of the network is reported in terms of round‐trip time, packet loss, and average delivery ratio. The major results of the experiment can be thus summarized: the implemented network structure was successful in continuously operating over five days with nodes seamlessly entering and exiting the network; the performance of the network varied greatly with fluctuations in the acoustic channel; the addition of security features induced a minor degradation in network performance with respect to channel variation; the AUVs were successfully controlled from a remote station through acoustic signals routed by the network. © 2013 Wiley Periodicals, Inc.  相似文献   
9.
We propose an experimental methodology to determine the secondary Bjerknes force between rigid particles. Measurements done for different particles sizes showed acoustical inter particles interactions. We use and extend the methodology presented in a previous work. The determination of this force will lead us a better understanding of the aggregation process in acoustic resonators. We report in this work, the results of two parabolic flights campaigns performed at the Airbus A300 ZERO-G (Novespace, France).  相似文献   
10.
The cerebral cortex is a gray lamina formed by bodies of neurons covering the cerebral hemispheres, varying in thickness from 1.25 mm in the occipital lobe to 4 mm in the anterior lobe. The brain's surface is about 30 times greater that of the skull because of its many folds; such folds form the gyri, sulci and fissures and mark out areas having specific functions, divided into five lobes. Convolution formation may vary between individuals and is an important feature of brain formation; such patterns can be mathematically represented as Turing patterns. This article describes how a phenomenological model was developed by describing the formation pattern for the gyri occurring in the cerebral cortex by reaction diffusion equations with Turing space parameters. Numerical examples for simplified geometries of a brain were solved to study pattern formation. The finite element method was used for the numerical solution, in conjunction with the Newton–Raphson method. The numerical examples showed that the model can represent cerebral cortex fold formation and reproduce pathologies related to gyri formation, such as polymicrogyria and lissencephaly.  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