全文获取类型
收费全文 | 647篇 |
免费 | 61篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 29篇 |
综合类 | 2篇 |
化学工业 | 134篇 |
金属工艺 | 4篇 |
机械仪表 | 10篇 |
建筑科学 | 10篇 |
能源动力 | 25篇 |
轻工业 | 56篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 113篇 |
一般工业技术 | 168篇 |
冶金工业 | 48篇 |
原子能技术 | 2篇 |
自动化技术 | 105篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 14篇 |
2020年 | 11篇 |
2019年 | 18篇 |
2018年 | 31篇 |
2017年 | 26篇 |
2016年 | 28篇 |
2015年 | 19篇 |
2014年 | 24篇 |
2013年 | 65篇 |
2012年 | 33篇 |
2011年 | 41篇 |
2010年 | 25篇 |
2009年 | 32篇 |
2008年 | 23篇 |
2007年 | 30篇 |
2006年 | 35篇 |
2005年 | 21篇 |
2004年 | 21篇 |
2003年 | 15篇 |
2002年 | 16篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 15篇 |
1998年 | 17篇 |
1997年 | 21篇 |
1996年 | 16篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有710条查询结果,搜索用时 15 毫秒
21.
Fast image retrieval using color-spatial information 总被引:1,自引:0,他引:1
Beng Chin Ooi Kian-Lee Tan Tat Seng Chua Wynne Hsu 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(2):115-128
In this paper, we present an image retrieval system that employs both the color and spatial information of images to facilitate
the retrieval process. The basic unit used in our technique is a single-colored cluster, which bounds a homogeneous region of that color in an image. Two clusters from two images are similar if they are of the
same color and overlap in the image space. The number of clusters that can be extracted from an image can be very large, and
it affects the accuracy of retrieval. We study the effect of the number of clusters on retrieval effectiveness to determine
an appropriate value for “optimal' performance. To facilitate efficient retrieval, we also propose a multi-tier indexing
mechanism called the Sequenced Multi-Attribute Tree (SMAT). We implemented a two-tier SMAT, where the first layer is used to prune away clusters that are of different colors,
while the second layer discriminates clusters of different spatial locality. We conducted an experimental study on an image
database consisting of 12,000 images. Our results show the effectiveness of the proposed color-spatial approach, and the efficiency
of the proposed indexing mechanism.
Received August 1, 1997 / Accepted December 9, 1997 相似文献
22.
Nonclassical light and collapse-revival dynamics are consequences of dynamical quantum interference in transient photon-atom interaction. We study the time evolution of atom and photons in a high quality cavity for time-dependent atom-field coupling, with different initial field states and initial atomic states. The inversion for initial superposed atomic state seems to be independent of initial classical fields but can be stimulated by the Schrodinger cat field. Interesting effects of the transient coupling are found through analysis of the collapse-revival in population inversion and the features in the Wigner function. Oscillatory coupling coefficient can prolong the occurrence of collapse, in analogy to the Zeno effect. The intensity atom-field coupling duration is an important parameter for controlling atomic inversion and producing frozen nonclassical light in the cavity after the atom-field coupling ceases. 相似文献
23.
Abstract CORDIC is a rotation based computation kernel algorithm which has been found to be very attractive for problems which require intensive, frequent evaluations of elementary functions. This paper addresses the implementation issues in the design of a VLSI CORDIC processor for digital signal processing and numerical linear algebra computations. The first part of this paper will discuss various design considerations for practical CORDIC algorithms. In particular, we have established criteria for the selection of nearly optimal shift sequences which are crucial to the performance of the CORDIC computation. The various design considerations of a CORDIC processor are discussed. Finally, the architecture of a prototype CORDIC processor data path chip is described. 相似文献
24.
Ngo Quang Minh Khiem Guntur Ravindra Wei Tsang Ooi 《Signal Processing: Image Communication》2012,27(4):360-377
Zoomable video allows users to selectively zoom and pan into regions of interest within the video for viewing at higher resolutions. Such interaction requires dynamic cropping of RoIs on the source video. We have previously explored two different ways of encoding and transmitting video to support dynamic RoI cropping: (i) Monolithic streaming uses a standard video encoder to encode the video. When an RoI is requested, the bits belonging to the RoI along with other bits required to decode the RoIs (due to encoding dependencies) are transmitted. (ii) Tile streaming divides regions in the standard video into rectangular tiles that are encoded independently. The tiles that intersect with a requested RoI are transmitted. In this paper, we consider how the bandwidth needed to transmit the RoIs can be reduced by carefully encoding the source video for each of the two encoding schemes. The goal is to support bandwidth efficient compressed domain RoI cropping in the context of virtual zoom and pan by tuning encoder parameters. Our key idea is to exploit user access patterns to the RoIs, and encode different regions of the video with different encoding parameters based on the popularity of the region. We show that our encoding method can reduce the expected bandwidth by up to 43% in the test video sequence which we have used. 相似文献
25.
26.
A wide-band, passively Q-switched fibre lasers based on ytterbium- and thulium-doped fibre gain medium are proposed and demonstrated. The lasers employ a transition metal dichalcogenide, tungsten sulphoselenide as a saturable absorber (SA) which is prepared by mechanical exfoliation technique. By integrating the SA in the laser cavities, self-starting Q-switched at 1038 and 1982?nm are obtained. The generated pulses exhibit a microsecond pulse duration with few kilohertz repetition rate. The proposed SA has high potential as a new material to cater to the needs of various scientific, industrial and biomedical applications. 相似文献
27.
Synthesis and Characterization of NiO Nano‐Spheres by Templating on Chitosan as a Green Precursor
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Cheng Keong Choo Tze Lim Goh Ladan Shahcheraghi Gek Cheng Ngoh Ahmad Zuhairi Abdullah Bahman Amini Horri Babak Salamatinia 《Journal of the American Ceramic Society》2016,99(12):3874-3882
In this study, nickel oxide was prepared through the calcination of extrusion dripped chitosan/nickel nitrate beads. The morphology and structural properties of the products were studied using various characterization techniques. Uniformly distributed nickel oxide was formed as observed from the studies of surface morphology where the processing parameters play a huge role on the resulting morphology. TEM results have shown that nickel oxide with crystallite sizes of 10–30 nm was obtained. The Fourier‐transform infrared spectra studies show an intense peak at 525 cm?1, which is attributed to the vibration of Ni–O bond. Furthermore, the XRD results show NiO diffraction peaks correspond to (111), (200), (220), (311), and (222) which indicates that a bunsenite structure with a face‐centered cubic phase was produced in this study. The usage of 500°C as the lower limit in this study is justified due to the complete removal of the templating material as seen in the thermalgravimetric analysis studies. Furthermore, it was obtained that the largest surface area of nickel oxide synthesized using this technique is 48.024 m2/g with pore sizes of 19.843 nm. The usage of chitosan as a green template for the synthesis of nanoparticles has shown promising results which allows a more economical and sustainable approach for the fabrication of nanomaterials. 相似文献
28.
Yi Peng Teoh Zhong Xian Ooi Azhar Abu Bakar Hanafi Ismail 《Iranian Polymer Journal》2016,25(3):285-294
The present paper is focused on exploiting Plackett–Burman design to examine the formulation effect of various chemical components content on the curing characteristics of oil palm ash (OPA)-filled acrylonitrile butadiene rubber (NBR) compound. The filled-NBR compound was prepared by conventional laboratory-sized two roll mill and cured using sulfuric system. Six independent variables such as content of zinc oxide, stearic acid, N-isopropyl-N′-phenyl-p-phenylenediamine, N-cyclohexyl-2-benzothiazole sulfenamide (CBS), sulfur, and even OPA filler were carried out to screen their significant effect on the curing characteristics of NBR compound. The scorch time, optimal cure time, minimum torque, and maximum torque were selected as a response. Results showed that the scorch time and the optimal cure time were significantly affected by CBS, whereas the minimum torque and maximum torque were significantly affected by OPA and sulfur, respectively, within the studied range. Among the chemical components under study, zinc oxide and stearic acid had the least effect on the curing properties of NBR compound. Analysis of variances for all factorial models demonstrated that the model was significant with P value <0.05 while the regularity (R 2) of all models was greater than 0.9. Lastly, the optimal chemical concentrations were predicted to acquire the optimal condition of the curing system for filled-NBR compound. 相似文献
29.
Carbon dioxide (CO2) is one of the commonly emitted gaseous by-products in industrial processes. While CO2 gas is the main cause to greenhouse effect, various CO2 capture technologies have been proposed and implemented to sequester the CO2 before the waste gases being released into the atmosphere. One of the mature technologies for CO2 absorption is by using amine-based solvents. In this regard, different single amine solvents or blended amine solvents have been proven for their capability to remove CO2. However, the dissolution and reaction of CO2 gas with the amine solvents turn the solution corrosive. Such phenomenon is undesired as it posts corrosion problem to the absorption column, which normally built of carbon steel material. Henceforth, understanding the behaviour of different amine-based solvents in absorbing CO2 and its subsequent impact on carbon steel corrosion is very significant. In this review article, we will outline some of the more commonly used solvents and their respective advantages and disadvantages, motivating further investigation into the corrosion tendency. Meanwhile, existing gaps in this research area are discussed for future investigation. 相似文献
30.
By developing and applying certain results on boundary crossing probabilities of generalized likelihood ratio statistics in multiparameter exponential families, we show that Lai's (1988a) modification of Schwarz's (1962) sequential likelihood ratio tests of one-sided hypotheses in the one-parameter case can be extended to general hypotheses in the multiparameter case. Such tests are shown to be asymptotically optimal, from both frequentist and Bayesian points of view, and numerical results are also given to demonstrate their performance. 相似文献