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排序方式: 共有228条查询结果,搜索用时 15 毫秒
1.
Sethuraman B.A. Rajan B.S. Shashidhar V. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(10):2596-2616
We present some general techniques for constructing full-rank, minimal-delay, rate at least one space-time block codes (STBCs) over a variety of signal sets for arbitrary number of transmit antennas using commutative division algebras (field extensions) as well as using noncommutative division algebras of the rational field /spl Qopf/ embedded in matrix rings. The first half of the paper deals with constructions using field extensions of /spl Qopf/. Working with cyclotomic field extensions, we construct several families of STBCs over a wide range of signal sets that are of full rank, minimal delay, and rate at least one appropriate for any number of transmit antennas. We study the coding gain and capacity of these codes. Using transcendental extensions we construct arbitrary rate codes that are full rank for arbitrary number of antennas. We also present a method of constructing STBCs using noncyclotomic field extensions. In the later half of the paper, we discuss two ways of embedding noncommutative division algebras into matrices: left regular representation, and representation over maximal cyclic subfields. The 4/spl times/4 real orthogonal design is obtained by the left regular representation of quaternions. Alamouti's (1998) code is just a special case of the construction using representation over maximal cyclic subfields and we observe certain algebraic uniqueness characteristics of it. Also, we discuss a general principle for constructing cyclic division algebras using the nth root of a transcendental element and study the capacity of the STBCs obtained from this construction. Another family of cyclic division algebras discovered by Brauer (1933) is discussed and several examples of STBCs derived from each of these constructions are presented. 相似文献
2.
Oxidation kinetics of copper in the temperature range of 973–1173 K atP
O
2=21.27 kPa exhibit enhancement and deceleration in the rates with changing polarity compared to normal oxidation under interrupted mode of directcurrent application. These conditions are achieved by connecting the oxidizing copper covered with an initially formed thin oxide film to the positive and negative terminal of a dc source, respectively. However, the influence of direction of the current is found to be opposite under uninterrupted mode of impressed current flow in the same temperature range. The effect of short-circuiting the metal to the outer oxide/air interface on the reaction kinetics is also reported. The rate of oxide-scale growth under normal condition, and two different modes of current applications as well as with shorting circuitry attachment conform to the parabolic growth law. The results pertaining to the two different modes of impressed current have been discussed considering both the phenomena of electrolysis of the oxide electrolyte and the polarization at the two phase boundaries. The enhancement and the reduction in rates under uninterrupted impressed current conditions are explained on the basis of increased and decreased average defect concentrations, respectively, within the oxide layer. The acceleration and deceleration in the rates under interrupted mode of current flow have been explained in the light of sustenance of a steeper and flatter electrochemical-potential gradient of defects, respectively, across the growing-oxide layer. The possible different responses of the metal/oxide and oxide/air interfaces to the impressed current brought into play by two different modes of current application, have enabled to display a better insight on the mechanistic aspects of scale growth under the influence of an externally applied current. 相似文献
3.
Craig A. Milroy Seonpil Jang Toshihiko Fujimori Ananth Dodabalapur Arumugam Manthiram 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(11)
Improved thin‐film microbatteries are needed to provide appropriate energy‐storage options to power the multitude of devices that will bring the proposed “Internet of Things” network to fruition (e.g., active radio‐frequency identification tags and microcontrollers for wearable and implantable devices). Although impressive efforts have been made to improve the energy density of 3D microbatteries, they have all used low energy‐density lithium‐ion chemistries, which present a fundamental barrier to miniaturization. In addition, they require complicated microfabrication processes that hinder cost‐competitiveness. Here, inkjet‐printed lithium–sulfur (Li–S) cathodes for integrated nanomanufacturing are reported. Single‐wall carbon nanotubes infused with electronically conductive straight‐chain sulfur (S@SWNT) are adopted as an integrated current‐collector/active‐material composite, and inkjet printing as a top‐down approach to achieve thin‐film shape control over printed electrode dimensions is used. The novel Li–S cathodes may be directly printed on traditional microelectronic semicoductor substrates (e.g., SiO2) or on flexible aluminum foil. Profilometry indicates that these microelectrodes are less than 10 µm thick, while cyclic voltammetry analyses show that the S@SWNT possesses pseudocapacitive characteristics and corroborates a previous study suggesting the S@SWNT discharge via a purely solid‐state mechanism. The printed electrodes produce ≈800 mAh g?1 S initially and ≈700 mAh g?1 after 100 charge/discharge cycles at C/2 rate. 相似文献
4.
5.
Ananth Ranganathan 《Autonomous Robots》2012,32(4):351-368
A shared vocabulary between humans and robots for describing spatial concepts is essential for effective human robot interaction.
Towards this goal, we present a novel technique for place categorization from visual cues called PLISS (Place Labeling through
Image Sequence Segmentation). PLISS is different from existing place categorization systems in two major ways—it inherently
works on video and image streams rather than single images, and it can detect “unknown” place labels, i.e. place categories
that it does not know about. PLISS uses changepoint detection to temporally segment image sequences which are subsequently
labeled. Changepoint detection and labeling are performed inside a systematic probabilistic framework. Unknown place labels
are detected by using a probabilistic classifier and keeping track of its label uncertainty. We present experiments and comparisons
on the large and extensive VPC dataset. We also demonstrate results using models learned from images downloaded from Google’s
image search. 相似文献
6.
Praveen Siluvai Antony Rajiv Ananth Sohony Rajesh B. Biniwale 《International Journal of Hydrogen Energy》2014
A mathematical model has been developed to study the impact of nozzle-catalyst distance and bulk gas temperature on the conversion and hydrogen evolution rate in a spray pulse reactor. The effects of reactor configuration and operating parameters on conversion and evolution rate were predicted with more than 90% accuracy. Reactor optimization and sensitivity analysis were carried out and an optimal design of nozzle-catalyst distance 5 cm and bulk gas temperature of 50 °C were proposed. The optimized design was predicted to increase the conversion from approximately 32–74%. The model could be in general used for designing any endothermic heterogeneous catalytic reaction in a spray pulse reactor. 相似文献
7.
8.
Sethuraman Latha Vijayakumar Ganesh Ananthan Shreyas Paranthaman M. Parans Keller Jonathan King Ryan 《Forschung im Ingenieurwesen》2021,85(2):287-311
Forschung im Ingenieurwesen - Direct-drive wind turbine generators are increasing in popularity, thanks to recent project developments—especially offshore, where reliability and efficiency... 相似文献
9.
Kola Srinivas G. Sivakumar Ch. Ramesh Kumar M. Ananth Reddy K. Bhanuprakash V. Jayathirtha Rao Chih-Wei Chen Ying-Chan Hsu Jiann T. Lin 《Synthetic Metals》2011,161(15-16):1671-1681
We have synthesized and characterized donor–π–spacer–acceptor type molecules in which 1,3,4-oxadiazoles are π-spacers, triphenylamines are the donors and cyanoacetic acid are the acceptors for use as sensitizers in dye-sensitized solar cells (DSSCs). Detailed absorption, emission, electrochemical, photoelectrochemical and computational studies have been carried out on five novel derivatives. The dyes have an absorption range of 377–388 nm, and an emission in the range of 494–540 nm. There is a large charge transfer from the donor side to the acceptor side on excitation. The propeller shape of the triphenylamine and the bulky substituents on it help in reducing the dye-aggregation on TiO2 surface. The dyes exhibited good overall conversion efficiency (2.79–3.21%). Plane wave calculations indicate that the dye has a reasonably strong binding to the TiO2 surface and the generated DOS picture shows an overlap of the molecular orbitals of the dye and the TiO2 bands. We conclude that the dyes have a promising role as sensitizers in DSSC. 相似文献
10.