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   170篇
  免费   9篇
电工技术   1篇
化学工业   23篇
金属工艺   6篇
机械仪表   2篇
建筑科学   2篇
矿业工程   4篇
能源动力   3篇
轻工业   20篇
石油天然气   2篇
无线电   14篇
一般工业技术   44篇
冶金工业   35篇
原子能技术   2篇
自动化技术   21篇
  2022年   1篇
  2021年   1篇
  2020年   1篇
  2018年   1篇
  2017年   5篇
  2016年   5篇
  2015年   4篇
  2014年   4篇
  2013年   12篇
  2012年   8篇
  2011年   6篇
  2010年   7篇
  2009年   8篇
  2008年   6篇
  2007年   11篇
  2006年   2篇
  2005年   8篇
  2004年   5篇
  2003年   3篇
  2002年   4篇
  2001年   1篇
  2000年   3篇
  1999年   1篇
  1998年   9篇
  1997年   11篇
  1996年   8篇
  1995年   3篇
  1994年   2篇
  1992年   1篇
  1991年   2篇
  1990年   3篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1986年   3篇
  1985年   2篇
  1984年   7篇
  1983年   3篇
  1981年   1篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
  1969年   1篇
  1963年   1篇
  1962年   1篇
  1961年   3篇
  1959年   1篇
排序方式: 共有179条查询结果,搜索用时 15 毫秒
81.
Ontologies have been intensively applied for improving multimedia search and retrieval by providing explicit meaning to visual content. Several multimedia ontologies have been recently proposed as knowledge models suitable for narrowing the well known semantic gap and for enabling the semantic interpretation of images. Since these ontologies have been created in different application contexts, establishing links between them, a task known as ontology matching, promises to fully unlock their potential in support of multimedia search and retrieval. This paper proposes and compares empirically two extensional ontology matching techniques applied to an important semantic image retrieval issue: automatically associating common-sense knowledge to multimedia concepts. First, we extend a previously introduced textual concept matching approach to use both textual and visual representation of images. In addition, a novel matching technique based on a multi-modal graph is proposed. We argue that the textual and visual modalities have to be seen as complementary rather than as exclusive sources of extensional information in order to improve the efficiency of the application of an ontology matching approach in the multimedia domain. An experimental evaluation is included in the paper.  相似文献   
82.
We present two comparative models of the GABA(A) receptor. Model 1 is based on the 4-A resolution structure of the nicotinic acetylcholine receptor from Torpedo marmorata and represents the unliganded receptor. Two agonists, GABA and muscimol, two benzodiazepines, flunitrazepam and alprazolam, together with the general anaesthetic halothane, have been docked to this model. The ion flow is also explored in model 1 by evaluating the interaction energy of a chloride ion as it traverses the extracellular, transmembrane and intracellular domains of the protein. Model 2 differs from model 1 only in the extracellular domain and represents the liganded receptor. Comparison between the two models not only allows us to explore commonalities and differences with comparative models of the nicotinic acetylcholine receptor, but also suggests possible protein sub-domain interactions with the GABA(A) receptor not previously addressed.  相似文献   
83.
This work shows a method for the determination of iodine in a variety of food samples and reference materials using inductively coupled plasma-mass spectrometry (ICP-MS) following alkaline extraction. Optimisation of the addition of organic carbon showed that a minimum of 3% 2-propanol was necessary for a constant ratio of iodine to internal standard. The limit of quantification (LOQ), calculated as 30σ for the method, was 36 ng g–1 in solid food samples. For method validation, seven standard reference materials (SRM) and 21 fortified food samples were used. The precision (%RSD) of the measurements was in the 2–7% range. Accuracies for the SRMs were 85–105%, while the fortified food samples showed 81–119% recoveries, including a number of samples fortified at 50% of the LOQ.  相似文献   
84.
Isolated were pathogenic micromycetes from tap drinking water among which the most typical were Aspergillus niger, Aspergillus flavus, Aspergillus ochraceus, Penicillum cyclopium, Penicillium expansum, Cladosporium cladosporioides. The article has studied inactivation of microscopic fungus by UV radiation. It has also established a series of sensitivity of microorganisms to the effect of ultraviolet. It has been shown that such sanitary-indicative test microorganisms as Escherichia coli, Bacillius subtilis, Candida albicans cannot be used for assessing the degree of water decontamination by UV radiation by the mycological criterion. The stability of micromycetes to UV radiation is an evidence of a necessity to use complex methods of water decontamination.  相似文献   
85.
Abstract

We investigate light propagation through materials with both linear and circular anisotropy and find the relation of the amplitude and polarization transfer functions to the four anisotropic characteristics: linear circular birefringence, and linear and circular dichroism. We determine these four characteristics of anisotropic samples by measuring the output intensity and polarization corresponding to different input polarization azimuths and fitting the theoretical and experimental results. In our experiments we have used films of side-chain azobenzene polyesters in which optical anisotropy had been previously induced on illumination with elliptically polarized light.  相似文献   
86.
A theory for determining the existence, number and position of limit cycles in perturbed Hamiltonian systems, that depends on a small parameter, is presented. The limit cycle emerges from the periodic trajectories surrounding a centre of the unperturbed system. By means of this theory a sinusoidal oscillator with a nonlinear element has been analysed. It is shown that only the terms with odd degrees in the approximation polynomial of the nonlinear element's characteristic exert an influence on the initiation of limit cycles.  相似文献   
87.
This work reports an in situ wide‐angle X‐ray scattering (WAXS) study of the structural evolution of PET with distinct initial morphologies during step uniaxial stretching in the solid state. Two types of samples were analyzed under synchrotron X‐ray radiation, namely quasi‐amorphous (QA) and semicrystalline (SC) (with 2D and 3D order). Results show that initially different QA morphologies evolve following the same stages: (i) stage I (before neck), at almost constant orientation level the amorphous phase evolves into mesophase; (ii) stage II (neck formation), there is a rapid increase of polymer orientation and the appearance of a periodical mesophase from the highly oriented mesophase; (iii) stage III (necking propagation), there is a leveling off of the average polymer orientation together with partial conversion of the periodical mesophase and mesophase into highly oriented amorphous. The behaviors of the two SC morphologies are completely distinct. A 2D order crystalline morphology evolves with stretching likewise the QA through three stages: (i) at early stages of deformation the polymer orientation remains unchanged while the amorphous phase amount increases slightly, stage I; (ii) in stage II, a fast increase of polymer orientation is accompanied by large formation of mesophase; and (iii) in stage III there is the level off of polymer orientation as the chains approach their finite extensibility and the 3D crystalline order is achieved. Evolution of SC sample with 3D crystalline order mainly features constant orientation increase together with mesophase increment. Structure deformation models are suggested. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   
88.
Ion implants of 2.0 and 5.0 keV 11B+ and 2.2, 5.0, and 8.9 keV 49BF 2 + at a dose of 1E15/cm2 were investigated. Anneal conditions were developed which produced highly activated yet shallow junctions. The effects of oxygen were studied previously by us1–12 and found to be an important variable to control in order to produce uniform and repeatable sheet resistance and junction depths. A purge procedure and integrated oxygen sensor were developed to measure and control the oxygen background concentration for each anneal to assure repeatable results. “Shelf-life,” that is dwell time between implant and anneal, was investigated. It was found that, for low energy implants, the amount of native oxide grown affects retained dose, sheet resistance (Rs), and uniformity. Controlled oxygen level repeatability and shelf life results are presented and equipment designs are discussed.  相似文献   
89.
An analytical procedure based on L. M. Kachanov's model of fracture front propagation is examined. Its purpose is to predict the fracture of sheet glass in the course of tempering. The conditions under which fracture is likely to take place and the time to fracture are determined. Translated from Steklo i Keramika No. 10, pp. 10–11, October, 1997.  相似文献   
90.
We report for the first time the inducing of large circular anisotropy in previously unoriented films of side-chain azobenzene polyesters on illumination with circularly polarized light at a wavelength of 488 nm. The circular dichroism and optical activity are measured simultaneously in real time at two wavelengths, 488 nm and 633 nm. The photoinduced optical activity has been measured to be 104 deg/cm and the circular dichroism has been found to be on the order of 0.3.  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