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排序方式: 共有193条查询结果,搜索用时 15 毫秒
1.
Permutation polynomials (PPs) are used for interleavers in turbo codes, cryptography or sequence generation. The paper presents an algorithm for determining the number of true different PPs of degrees up to five. It is based on the algorithm from Weng and Dong (IEEE Trans Inf Theory 54(9):4388–4390, 2008) and on the null polynomials modulo the interleaver length. 相似文献
2.
Diketopyrrolopyrrole Organic Thin‐Film Transistors: Impact of Alkyl Substituents and Tolerance of Ethylhexyl Stereoisomers 下载免费PDF全文
Matthias Stolte Sabin‐Lucian Suraru Patricia Diemer Tao He Christian Burschka Ute Zschieschang Hagen Klauk Frank Würthner 《Advanced functional materials》2016,26(41):7415-7422
Bis(thiophen‐2‐yl)‐diketopyrrolopyrrole (DPP) dyes bearing various alkyl substituents at the amide positions (n‐butyl, n‐pentyl, n‐hexyl, n‐heptyl, n‐octyl, 2‐ethylhexyl) and chlorine (Cl), bromine (Br), or cyano (CN) substituents at the thiophene positions have been synthesized and investigated with regard to their molecular and semiconducting properties. Intense absorption, strong fluorescence, and reversible oxidation and reduction processes are common to all of these dyes. Their characterization as organic semiconductors in vacuum‐processed thin‐film transistors reveals p‐channel operation with field‐effect mobilities ranging from 0.01 to 0.7 cm2 V?1 s?1. The highest mobility is found for the DPP dyes bearing the 2‐ethylhexyl substituents, which is surprising, considering that as a result of the chiral substituents, this material is a mixture of (R,R), (S,S), and (R,S) stereoisomers. The high carrier mobility in the films of the DPPs bearing stereoisomerically inhomogeneous ethylhexyl groups is rationalized here by single‐crystal X‐ray diffraction (XRD) analysis in combination with XRD and atomic force microscopy studies on thin films, which reveal the presence of slightly different 2D layer arrangements for the n‐alkyl and the 2‐ethylhexyl derivatives. For the cyano‐substituted DPPs possessing the lowest LUMO levels, ambipolar transport characteristics are observed. 相似文献
3.
Lucian M. Rusnac Octavian Floarea Radu V. Vladea 《Journal of the American Oil Chemists' Society》1992,69(4):384-386
Continuous hydrogenation of industrially refined soybean oil with Harshaw Ni catalyst was achieved in a slurry column equipped
with Sulzer SMV motionless mixers. The influence of the operating parameters (temperature, pressure, catalyst concentration
and gas velocity) was investigated. The presumption that, in this equipment, the liquid-solid mass transfer limits the rate
of the process is in good agreement with the experimental data. 相似文献
4.
Abstract Chlorine dioxide delignification (D0) modifies kraft residual lignin by oxidizing phenolic groups to both quinone and muconic acid structures. Alkaline extraction (E), in addition to removing solubilized lignin, converts quinone moieties to polyphenols. These polyphenols are easily oxidized by oxygen in an (EO) stage or by ClO2 in a D1 stage to hydroxyquinones (~1.8 mmol/g lignin). Pulps treated by D0E consume considerably more ClO2 in the D1 than D0(EO), and have lower bleachability, as was quantified by a simple bleaching model. Both D0E and D0(EO) pulps approach a common brightness ceiling (~83 ISO) when excess ClO2 is applied. Examination of the post‐D1 b* values indicates that D0E and D0(EO) also have similar asymptotic b* values (~6), indicating that both pulps have similar residual chromophores. Hydroxyquinone structures appear to be eliminated in the D1 stage for D0(EO) pulps, and at high ClO2 levels for D0E pulps. 相似文献
5.
Plant volatile organic compounds (VOCs) elicited in response to herbivory serve as cues for parasitic and predatory insects.
Knowledge about quantitative relationships between the extent of herbivore-induced damage and the quantities of VOCs released
is scarce. We studied the kinetics of VOC-emissions from foliage of the deciduous tree Alnus glutinosa induced by feeding activity of larvae of the geometrid moth Cabera pusaria. Quantitative relationships between the intensity of stress and strength of plant response were determined. Intensity of biotic
stress was characterized by herbivore numbers (0–8 larvae) and by the amount of leaf area eaten. The strength of plant response
was characterized by monitoring (i) changes in photosynthesis, (ii) leaf ultrastructure, and (iii) plant volatiles. Net assimilation
rate displayed compensatory responses in herbivore-damaged leaves compared with control leaves. This compensatory response
was associated with an overall increase in chloroplast size. Feeding-induced emissions of products of the lipoxygenase pathway
(LOX products; (E)-2-hexenal, (Z)-3-hexenol, 1-hexanol, and (Z)-3-hexenyl acetate) peaked at day 1 after larval feeding started, followed by an increase of emissions of ubiquitous monoterpenes
peaking on days 2 and 3. The emission of the monoterpene (E)-β-ocimene and of the nerolidol-derived homoterpene 4,8-dimethyl-nona-1,3,7-triene (DMNT) peaked on day 3. Furthermore, the
emission kinetics of the sesquiterpene (E,E)-α-farnesene tended to be biphasic with peaks on days 2 and 4 after start of larval feeding. Emission rates of the induced
LOX products, of (E)-β-ocimene and (E,E)-α-farnesene were positively correlated with the number of larvae feeding. In contrast, the emission of DMNT was independent
of the number of feeders. These data show quantitative relationships between the strength of herbivory and the emissions of
LOX products and most of the terpenoids elicited in response to feeding. Thus, herbivory-elicited LOX products and terpenoid
emissions may convey both quantitative and qualitative signals to antagonists of the herbivores. In contrast, our data suggest
that the feeding-induced homoterpene DMNT conveys the information “presence of herbivores” rather than information about the
quantities of herbivores to predators and parasitoids. 相似文献
6.
Gerlinde Rusu Nicolas Joly Geza Bandur Ionel Manoviciu Patrick Martin Lucian Rusnac 《Journal of Polymer Research》2011,18(6):2495-2504
New inulin-based materials were obtained by graft-copolymerization of inulin (poly-β(1 → 2)-fructoside) with 2-ethyl-hexyl acrylate. Inulin mixed esters were first synthesized by acylation using methacryloyl and palmitoyl chlorides. Further, these esters were copolymerized with 2-ethyl-hexyl acrylate in order to obtain bio-based crosslinked materials that could be used as commodity plastics and that would have biodegradable properties. The obtained products were characterized using FT-IR and 1H NMR spectroscopies, thermogravimetry; differential scanning calorimetry, and activation energy for the degradation processes (using Kissinger method) was calculated. These biomaterials were also subjected to density measurement, tensile and torsion tests to evaluate their mechanical properties. 相似文献
7.
Florin Mingireanu Lucian P. Georgescu Gabriel Murariu Ionut Mocanu Marius Stoia-Djeska Nicolae Jula 《Surface Engineering and Applied Electrochemistry》2014,50(3):267-274
This paper presents an innovative method to increase the regression speed of a solid fuel grain by using oxidizer doping. The results obtained on a propulsion application showing the performance parameters as an output of a numerical model are provided. Two models are given that predict the regression speed increase for embedding wires and for oxidizer doping with a factor of ~2 to 3. Also, it is shown that this increase of the regression speed by using a low oxidizer doping percentage, which is based on the assumption that at a higher doping rate the combustion instabilities, can lead to detonations. Next, a thermochemical model for the combustion within the oxidizer doping model is afforded. For this model, the burn is assumed to take place around the surface of each of the oxidizer particles, being composed of two different burning processes: one is the burning on the surface of the solid fuel grain and the other is the burning between the solid fuel and the solid oxidizer. For a non-doped fuel grain, the burning takes place only on the surface of the fuel grain. Finally, a potential application of such propulsion units to small satellite launchers is presented, and a case study of such a vehicle intended to place a 50 kg payload on a low earth orbit (300 to 500 km altitude) is described. The modelling proposed is based on the assumption that the use of solid methane makes this launcher environmentally friendly. 相似文献
8.
Often associated with acts of vandalism, graffiti can also be identified with the so‐called street art movement. Moreover, in the historical context of visual arts from the 20th and 21st century, graffiti spray paints feature among the materials employed in the work of representative artists such as Lucio Fontana, Richard Hamilton, Yves Klein, or David Alfaro Siqueiros. In this study, a large number of artist spray paints were analyzed by means of X‐Ray Fluorescence (XRF), Fourier Transform Infrared Spectroscopy (FTIR), spectrophotometry, and Hyperspectral Imaging (HSI). The aim of the study was to provide a chemical characterization of the main organic and inorganic components present within the spray paint formulations by means of a complementary non‐destructive approach. Titanium white, zinc white, bismuth vanadate yellow, ultramarine, strontium sulfide, iron, and copper oxides, along a series of pigments of the azo, phthalocyanine, and quinacridone classes could be identified. High amounts of barium sulfate as well as calcium‐based extenders were also detected. FTIR analysis provided important information regarding the binder composition, mainly modified alkyd resins being identified. Additional information related to the existing chromophores as well as specific binder‐pigments interactions could also be highlighted within the HSI data sets. Overall results provide new insights on the complex chemistry of this new range of materials, which could help future investigations carried on street art graffiti, contemporary murals, or mixed‐media artworks. 相似文献
9.
Lucian M. Sprague John H. Arnold 《Journal of the American Oil Chemists' Society》1972,49(8):345A-350A
Estimates of the potential yield from the marine environment have varied between 20–1000 million metric tons because they
were based on poor and incomplete data and differing approaches to trophic level evaluation. The data is improving slightly
and the estimates are beginning to agree within half an order of magnitude. We believe that the yield of marine fisheries
could ultimately be expanded to ca. 400 million metric tons, by utilizing presently known but underutilized resources, by
opening new fisheries in areas like the Indian Ocean and Antarctic and by improving systems of regulating the catch and fishing
effort. In order to meet the maximum potential of the marine environment we will have to harvest at a lower trophic level
in the food chain because most fish in higher trophic levels are being harvested at their maximum sustainable yield. This
increasing harvest of smaller fish, plus the increasing demand for fishmeal for animal feed will cause an increasing proportion
of the fish harvested to be used for reduction to fishmeal and oil.
One of 11 papers presented in the symposium “World Supply of Edible Oils and Proteins,” Atlantic City, October 1971. 相似文献
10.
Preserving mapping consistency under schema changes 总被引:1,自引:0,他引:1
Yannis?VelegrakisEmail author Renée?J.?Miller Lucian?Popa 《The VLDB Journal The International Journal on Very Large Data Bases》2004,13(3):274-293
In dynamic environments like the Web, data sources may change not only their data but also their schemas, their semantics, and their query capabilities. When a mapping is left inconsistent by a schema change, it has to be detected and updated. We present a novel framework and a tool (ToMAS) for automatically adapting (rewriting) mappings as schemas evolve. Our approach considers not only local changes to a schema but also changes that may affect and transform many components of a schema. Our algorithm detects mappings affected by structural or constraint changes and generates all the rewritings that are consistent with the semantics of the changed schemas. Our approach explicitly models mapping choices made by a user and maintains these choices, whenever possible, as the schemas and mappings evolve. When there is more than one candidate rewriting, the algorithm may rank them based on how close they are to the semantics of the existing mappings.Received: 13 January 2004, Accepted: 26 March 2004, Published online: 12 August 2004Edited by: M. Carey 相似文献