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   181篇
  免费   15篇
  国内免费   1篇
电工技术   1篇
化学工业   57篇
金属工艺   5篇
机械仪表   8篇
建筑科学   3篇
能源动力   13篇
轻工业   41篇
水利工程   1篇
石油天然气   4篇
无线电   4篇
一般工业技术   38篇
冶金工业   8篇
自动化技术   14篇
  2024年   1篇
  2022年   7篇
  2021年   9篇
  2020年   4篇
  2019年   9篇
  2018年   5篇
  2017年   6篇
  2016年   9篇
  2015年   5篇
  2014年   13篇
  2013年   19篇
  2012年   17篇
  2011年   14篇
  2010年   6篇
  2009年   11篇
  2008年   13篇
  2007年   7篇
  2006年   5篇
  2005年   5篇
  2004年   4篇
  2003年   4篇
  2002年   2篇
  2001年   1篇
  2000年   3篇
  1999年   2篇
  1998年   5篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1992年   1篇
  1991年   2篇
  1982年   1篇
  1970年   2篇
排序方式: 共有197条查询结果,搜索用时 15 毫秒
1.
The purpose of this study was to contrast the discharge patterns of the same motor units during movements and during isometric contractions that were produced with comparable torque-time characteristics. Subjects performed elbow flexion and extension movements with predetermined acceleration characteristics. The average acceleration and deceleration profiles for the movements were reproduced in the isometric setting by presenting the kinematic profiles as templates for torque production. Trained subjects were able to match the first agonist (AG1) and antagonist (ANT) electromyographic (EMG) bursts, but tended to produce a smaller second agonist burst (AG2) in the isometric contraction. Twenty-five motor units from triceps brachii were studied. The same motor units (with one exception) were recruited and subsequently discharged in a similar fashion in both the isometric and movement tasks in the AG1 and ANT EMG bursts, with fewer motor unit discharges in the AG2 burst in the isometric contraction. The central control mechanisms appear to be the same for the acceleration phase of movement and isometric contraction, but differ during the deceleration phase.  相似文献   
2.
B. Petrova  E. Ekinci  N. Petrov  F. Yardim 《Carbon》2007,45(4):704-709
The influence of pitch composition and surface properties of petroleum coke on the interaction of pitch and coke in the composite is studied. The adsorption results and EPR data indicate that recombination of paramagnetic centers and interaction of oxygen functional groups occur during the preparation of the composite. As a result of interaction between petroleum coke and pitch, polar compounds are concentrated in the adsorption layer. The baking criterion is used for the characterization of the baking ability of the pitches obtained as a result of different oxidation treatments of commercial coal tar pitch. It is determined that physico-chemical properties of the obtained pitches influence the value of the “baking criterion”. The kind of thermo-oxidation treatment of the parent pitch should be chosen hence achieving the maximum value of the baking criterion. For this purpose, the maximal part of the pitch has to take part in the adsorption layer.  相似文献   
3.
Palmprint Recognition by Applying Wavelet-Based Kernel PCA   总被引:2,自引:0,他引:2       下载免费PDF全文
This paper presents a wavelet-based kernel Principal Component Analysis (PCA) method by integrating the Daubechies wavelet representation of palm images and the kernel PCA method for palmprint recognition. Kernel PCA is a technique for nonlinear dimension reduction of data with an underlying nonlinear spatial structure. The intensity values of the palmprint image are first normalized by using mean and standard deviation. The palmprint is then transformed into the wavelet domain to decompose palm images and the lowest resolution subband coeffcients are chosen for palm representation. The kernel PCA method is then applied to extract non-linear features from the subband coeffcients. Finally, similarity measurement is accomplished by using weighted Euclidean linear distance-based nearest neighbor classifier. Experimental results on PolyU Palmprint Databases demonstrate that the proposed approach achieves highly competitive performance with respect to the published palmprint recognition approaches.  相似文献   
4.
Recognizing people by gait promises to be useful for identifying individuals from a distance; in this regard, improved techniques are under development. In this paper, an improved method for gait recognition is proposed. Binarized silhouette of a motion object is first represented by four 1-D signals that are the basic image features called the distance vectors. The distance vectors are differences between the bounding box and silhouette, and extracted using four projections to silhouette. Fourier Transform is employed as a preprocessing step to achieve translation invariant for the gait patterns accumulated from silhouette sequences that are extracted from the subjects’ walk in different speed and/or different time. Then, eigenspace transformation is applied to reduce the dimensionality of the input feature space. Support vector machine (SVM)-based pattern classification technique is then performed in the lower-dimensional eigenspace for recognition. The input feature space is alternatively constructed by using two different approaches. The four projections (1-D signals) are independently classified in the first approach. A fusion task is then applied to produce the final decision. In the second approach, the four projections are concatenated to have one vector and then pattern classification with one vector is performed in the lower-dimensional eigenspace for recognition. The experiments are carried out on the most well-known public gait databases: the CMU, the USF, SOTON, and NLPR human gait databases. To effectively understand the performance of the algorithm, the experiments are executed and presented as increasing amounts of the gait cycles of each person available during the training procedure. Finally, the performance of the proposed algorithm is comparatively illustrated to take into consideration the published gait recognition approaches.  相似文献   
5.
Nanotechnology is a promising technique to increase the bioavailability of herbal medicines. This paper presents the nanosuspension approach for increasing the aqueous solubility and thereby bioactivity of important herbal extracts. Nanosuspensions of the seeds of three plants extract (Silybum marianum, Elettaria cardamomum and Coriandrum sativum) were prepared by using polyvinyl alcohol (1.5% w/v) as a stabiliser. Prepared nanoparticles were characterised by scanning electron microscope. Activity of nanosuspension formulation was assessed by using four in vitro antioxidant assays. S. marianum, E. cardamomum and C. sativum particle size was observed to fall in range of 446.1 ± 112.6, 456.63 ± 339.2 and 432.1 ± 172.8 nm, respectively, most of the particles were having spherical shape and smooth topology. These synthesised nanoparticles were found to be more effective against quenching free radical than their crude extracts and standards [butylated hydroxyl toluene and ascorbic acid]. C. sativum nanosuspension showed most free radical scavenging potential against 2,2-diphenyl-1-picrylhdrazyl (DPPH) and superoxide free radical scavenging assays (IC50 0.59 ± 0.01 and 0.81 ± 0.11 mg/ml). S. marianum nanosuspension was found to be most effective against DPPH radicals scavenging (IC50 0.34 ± 0.02 mg/ml). It was concluded that nanosuspension of herbal medicines potentiates the antioxidant potential.  相似文献   
6.
7.
Carbon/poly(3,4‐ethylene dioxythiophene) (C/PEDOT) composites are synthesized by in situ chemical oxidative polymerization of EDOT monomer on carbon black in order to decrease carbon corrosion that occurred in carbon‐supported catalysts used in proton exchange membrane fuel cell. The effects of different dopants including polystyrene sulfonic acid, p‐toluenesulfonic acid and camphorsulfonic acid with the addition of ethylene glycol or dimethyl sulfoxide on the properties of the composites are investigated. The synthesized composites are characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, surface area analysis and scanning electron microscope. Electrical conductivity is determined by using the four‐point probe technique. Electrochemical oxidation characteristics of the synthesized C/PEDOT composites are investigated by cyclic voltammetry by applying 1.2 V for 24 h. The composite prepared at 25 °C with p‐toluenesulfonic acid and ethylene glycol shows the best carbon corrosion resistance. Platinum‐supported catalyst by using this composite was prepared using microwave irradiation technique, and it was seen that the prepared catalyst did not significantly lose its hydrogen oxidation and oxygen reduction reaction activities after electrochemical oxidation. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
8.
The readily available mixed‐valent iron trifluoroacetate complex [Fe2IIIFeII3‐O)(O2CCF3)6(H2O)3] is an effective catalyst for the polymerization of epoxides. A very small amount of the catalyst (1.0–0.01 mol%) could initiate the polymerization of cyclohexene oxide, cyclopentene oxide and epichlorohydrin. Based on quantitative end‐group analysis by 19F NMR spectroscopy, a Lewis acid (LA) catalyzed anionic reaction mechanism is proposed. Copyright © 2012 Society of Chemical Industry  相似文献   
9.
Multimedia Tools and Applications - Single image super resolution (SR) based on sparse representation is a promising technique where the SR problem is solved by searching for the most robust...  相似文献   
10.
Chronic liver disease (CLD) is a global threat to the human population, with manifestations resulting from alcohol-related liver disease (ALD) and non-alcohol fatty liver disease (NAFLD). NAFLD, if not treated, may progress to non-alcoholic steatohepatitis (NASH). Furthermore, inflammation leads to liver fibrosis, cirrhosis, and hepatocellular carcinoma. Vitexin, a natural flavonoid, has been recently reported for inhibiting NAFLD. It is a lipogenesis inhibitor and activates lipolysis and fatty acid oxidation. In addition, owing to its antioxidant properties, it appeared as a hepatoprotective candidate. However, it exhibits low bioavailability and low efficacy due to its hydrophobic nature. A novel rat model for liver cirrhosis was developed by CCL4/Urethane co-administration. Vitexin encapsulated liposomes were synthesized by the ‘thin-film hydration’ method. Polyethylene glycol (PEG) was coated on liposomes to enhance stability and stealth effect. The diseased rats were then treated with vitexin and PEGylated vitexin liposomes, administered intravenously and orally. Results ascertained the liposomal encapsulation of vitexin and subsequent PEG coating to be a substantial strategy for treating liver cirrhosis through oral drug delivery.  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