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61.
Marked through-thickness variations of preferred crystallographic orientations in aluminum-lithium (Al-Li) sheet alloys have
been observed and documented. These metallurgical features could have an effect on the way in which these materials distribute
strain during plastic deformation. From a theoretical or a practical point of view, it is important to investigate these texture
effects on plastic-deformation properties and particularly on forming limit strains. In this work, quantitative texture data,
which were determined by X-ray and neutron diffraction techniques, were used with a polycrystal model to predict the yield
locus of recrystallized and unrecrystallized AA8090 and AA2090 Al-Li sheets. The conventional AA2024 alloy in the annealed
condition was also investigated as a reference material. Subsequently, these yield loci were used to calculate forming limit
diagrams (FLDs) in the stretching range, using the Marciniak-Kuczynski (M-K) approach with strain rate potentials to describe
the constitutive properties of the sheets. A simple critical-thickness-strain criterion was used to predict the FLD in the
drawing range. The predicted FLDs were found to be in fair agreement with experimental curves obtained under punch-stretching
conditions. In general, experimental trends were accounted for by the results predicted using the average texture data. However,
the texture gradients do not completely explain the large scatter observed in the experimental forming limits and the high
average limit strain of the recrystallized AA8090. 相似文献
62.
An extension is developed for the asymptotic theory of electromagnetic diffraction by a discontinuity in curvature on a smooth convex perfectly-conducting surface. It covers the case where the rays incident on and diffracted from the discontinuity are nearly tangent to the surface or are creeping rays, so that surface diffraction is involved. This extension is restricted to those diffracted rays lying on the same side of the discontinuity as the incident ray; this includes backscatter but excludes forward scattering. 相似文献
63.
Rudolf J. Fritsch Frederic Martens Hans -Dieter Belitz 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1992,194(4):330-336
Summary Freel-glutamic acid (Glu), soluble nitrogen (N), and liberated amino groups (amino-N) were evaluated as indicators of proteolysis and maturation in a study of Cheddar cheese ripening. The analytical methods involved standardized extraction and fractionation procedures, enzymatic determination of Glu, the measurement of N by Kjeldahl and amino-N by a rapid spectrophotometric assay witho-phthaldialdehyde. Cheddar cheeses from two different production plants were stored at both 4° C and 10° C for nine months. All cheeses were periodically analyzed for Glu in an aqueous extract and for N and amino-N in citrate extracts soluble at pH 4.6 and in 12% trichloroacetic acid. All indices correlated well with each other and with the age of the cheese at a highly significant level. It was demonstrated that these parameters are well suited to determine the extent of proteolysis as an indication of the degree of maturity of ripening cheese, thus providing an objective measurement for age classification and raw material control. The convenient assays for Glu ando-phthaldialdehyde-reactive amino-N were proved suitable for routine applications, enabling a fast and sensitive check on the degree of proteolysis in cheese without sophisticated equipment.
Beurteilung des Reifungsverlaufes in Cheddarkäse durch chemische Indikatoren des Eiweißabbaus 1. Bestimmung von freier Glutaminsäure, löslichem Stickstoff und freigesetzten Aminogruppen
Zusammenfassung Freie Glutaminsäure (Glu), löslicher Stickstoff (N) und freigesetzte Aminogruppen (Amino-N) wurden als chemische Indikatoren des Eiweißabbaus und Reifegrades von Cheddarkäse in einer Reifungsstudie bewertet. Zwei verschiedene Cheddarkäse unterschiedlicher Herstellung wurden neun Monate bei 4 °C und 10 °C gelagert. Mit standardisierten Extraktionsund Fraktionierungsverfahren wurden alle Käseproben periodisch auf freie Glu im wasserlöslichen Extrakt mit einer enzymatischen Methode und auf N und Amino-N im pH 4,6- und 12% TCA-löslichem Extrakt mit der Kjeldahl-Methode bzw. mit einem schnellen photometrischen Ortho-Phthaldialdehyd(OPA)-Test analysiert. Alle Indikatoren zeigten eine hochsignifikante Korrelation sowohl zueinander als auch zum Käsealter. Es wurde gezeigt, daß diese Parameter zur Bestimmung des Eiweißabbaus als Maß für die Käsereifung gut geeignet sind. Sie ermöglichen damit objektive Meßverfahren für die Altersklassifizierung und Rohwarenkontrolle. Insbesondere die praktischen und bequemen Analysemethoden für Glu und OPA-Amino-N eignen sich für die Routineanwendung und ermöglichen eine schnelle und empfindliche Abschätzung des Proteolysegrades ohne hochentwikkelte komplizierte Apparaturen.相似文献
64.
Guillaume Duflos François Leduc Assi N'Guessan Frederic Krzewinski Ossarath Kol Pierre Malle 《Journal of the science of food and agriculture》2010,90(15):2568-2575
BACKGROUND: The freshness of whiting was studied at five stages of ice storage by comparing the analysis of volatile compounds obtained through solid phase microextraction/gas chromatography/mass spectrometry (SPME/GC/MS) with two sensory methods. RESULTS: Of the volatile compounds identified, 38 were analysed using a statistical multivariate approach and classified according to their role in the estimation of freshness during storage as markers of freshness or spoilage. Regarding the evolution of the presence or absence of individual compounds, three categories were defined. For example, the volatile compounds propanal, hexanal, 1‐penten‐3‐ol, pentanal, 2,3‐pentanedione, 1‐penten‐3‐one, heptanal, (E)‐2‐pentenal, 2,3‐octanedione, (Z)‐2‐penten‐1‐ol, 1‐pentanol, butanal, octanal, 3,5,5‐trimethyl‐2‐hexene, 1‐hexanol and 4,4‐dimethyl‐1,3‐dioxane appeared highly relevant, because they are found throughout storage and can be divided into several categories that are directly related to the quality of fish. CONCLUSION: SPME/GC/MS combined with a statistical multivariate approach may be a useful method to identify volatile compounds and characterise fish freshness during storage. Copyright © 2010 Society of Chemical Industry 相似文献
65.
We present a new method to improve the accuracy of force application and hardness measurements in hard surfaces by using low-force (<50 μN) nanoindentation technique with a cube-corner diamond tip mounted on an atomic force microscopy (AFM) sapphire cantilever. A force calibration procedure based on the force-matching method, which explicitly includes the tip geometry and the tip-substrate deformation during calibration, is proposed. A computer algorithm to automate this calibration procedure is also made available. The proposed methodology is verified experimentally by conducting AFM nanoindentations on fused quartz, Si(1 0 0) and a 100-nm-thick film of gold deposited on Si(1 0 0). Comparison of experimental results with finite element simulations and literature data yields excellent agreement. In particular, hardness measurements using AFM nanoindentation in fused quartz show a systematic error less than 2% when applying the force-matching method, as opposed to 37% with the standard protocol. Furthermore, the residual impressions left in the different substrates are examined in detail using non-contact AFM imaging with the same diamond probe. The uncertainty of method to measure the projected area of contact at maximum force due to elastic recovery effects is also discussed. 相似文献
66.
Sabina Kokoszka Frederic Debeaufort Alicia Hambleton Andrzej Lenart Andree Voilley 《Innovative Food Science and Emerging Technologies》2010,11(3):503-510
This study was conducted to determine the effect of both soy protein and glycerol contents on physico-chemical properties of soy protein isolate-based edible (SPI) films. The aim of this study was to better understand the influence of SPI and GLY contents on the behavior of the physico-chemical properties of soy protein isolate-based films. Films were casted from heated (70 °C for 20 min) alkaline (pH 10) aqueous solutions of SPI at 6, 7, 8, and 9 (w/w %), glycerol (50%, w/w, of SPI) and SPI at 7 (w/w %), glycerol (40, 60, 70 %, w/w of SPI). Water vapor permeability (WVP), was measured at 25 °C and for four different relative humidities (30–100%, 30–84%, 30–75%, 30–53%). Surface properties and differential scanning calorimetry were also measured. Varying the proportion of SPI and GLY had an effect on water vapor permeability, wetting and thermal properties of SPI films. A synergistic effect of glycerol and protein was observed on the water vapor permeability. Glycerol and RH gradient strongly enhance the moisture absorption rates and permeability of SPI based films. SPI content weakly increases the WVP and does not modify the surface properties. The temperature of denaturation of soy protein decreases glycerol content except for the higher concentration whereas it increases with protein ratio.Industrial relevanceThis topic of research aims to control mass transfers within composite foods or betweenfoods and surrounding media (for instance the headspace in packagings). The targeted applications from this work deals with the food product coating or the coating of paper-based packaging for limiting both the loss of water and flavors by cheese based products. This will allow to maintain the weight of the cheese during “ripening” and commercialization, and also to prevent (off-) flavour dissemination from very odorant cheese as produced in France and Poland. 相似文献
67.
Porous poly(ethylene glycol) diacrylate (PEGDA) monoliths have been prepared by UV‐initiated polymerization of PEGDA oligomer (Mn = 700 g/mol). In the mean time, the addition of hydrophobic poly(propylene oxide) (PPO, Mn = 725 g/mol) as porogen into an ethanol solution of PEGDA oligomer to form a homogenous mixture, causes a phase separation between PPO and PEGDA following removal of ethanol by UV heating. Porous PEGDA monolith was prepared by immediate heating at 300°C to remove PPO molecules from the as‐synthesized PEGDA/PPO hybrid. The micrometer pores of the PEGDA monolith have relatively concentrated pore size distribution according to the mercury intrusion porosimetry results and field emission scanning electron microscopy (FE‐SEM). 相似文献
68.
Frederic Buck Irina Kistner Christoph Rösler Andreas Schulz Matthias Walker Günter E. M. Tovar Thomas Schiestel 《化学,工程师,技术》2019,91(8):1117-1122
For the first time the combination of a separation process with a plasma process was successfully tested. In this case, a mixed‐conducting perovskite membrane separates the oxygen. At 1 kW a permeation of 2.24 mL min?1cm?2 could be achieved. Corresponding perovskite membranes have been manufactured as hollow fibers with a very good CO2 stability. The hollow fibers showed a constant permeation over more than 200 h. Furthermore, a spinning process with a sulphur‐free polymer binder has been established. 相似文献
69.
Liquid chromatography/quadrupole ion trap/time-of-flight determination of the efficacy of drug test kits for rapid screening of food 总被引:1,自引:0,他引:1
The goal of this study was to evaluate the plausibility and accuracy of commercially available on-site immunoassay urinalysis kits for the screening of compounds of interest within food matrices. In conjunction with this study, a sensitive, robust, and reproducible analytical method, utilizing solid-phase extraction liquid chromatography/quadrupole ion trap/time-of-flight mass spectrometry for confirmation analysis, was developed. The food matrices analyzed were tomato juice, apple juice, milk, beer, white wine, ground beef, powdered milk, and all-purpose flour. Compounds fortified into the food matrices included heroin, phencyclidine, cocaine, benzoylecgonine, methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine, imipramine, doxepin, nitrazepam, diazepam, oxazepam, temazepam, alprazolam, flunitrazepam, clonazepam, and lorazepam. Standard curves were prepared for each matrix from 10 to 500 ng/ml for each analyzed compound. All liquid chromatography/tandem mass spectrometry samples were fortified with 20 microl of deuterated internal standard at 90 ng/ml. Quality control standards were prepared at 20 and 400 ng/ml, and > 90% were within 2 SD of the mean for each analyte. The test kits were found to produce up to 85% of the expected results based on concentration levels of adulterants (i-Screen in milk). This study shows that lateral-flow immunoassay test kits are plausible as a rapid, accurate, and reliable screening method in the event of adulteration of the food supply. 相似文献
70.
Erick B. F. Galante Nathalie Mai Melissa K. Ladyman Philip P. Gill Frederic Coulon 《Journal of Energetic Materials》2021,39(1):85-99
ABSTRACT Energetic materials are often disposed by open-burning or open-detonation as it is a cost-effective and efficient means of destroying explosive material, and often minimizes the need to transport hazardous explosives to treatment facilities. This practice is often scrutinized for the negative environmental impact of the odorous and unsightly toxic gaseous emissions as well as the resulting deposition residues, which often contain unburned energetic materials. With the increasing use of Insensitive High Explosive compositions in munitions, it is essential that the potential environmental impact of their disposal is assessed before their extensive use to prevent the kind of contamination incidents experienced with legacy explosives. Therefore, the aim of this work was to develop a controlled laboratory experiment to identify the gaseous emissions and the energetic material residues that are generated through the combustion of the IHE components 3-nitro-1,2,4-triazol-5-one (NTO), 2,4-dinitroanisole (DNAN), and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX). A sealed vial containing small (mg) quantities of energetic material was heated until the energetic material combusted. Gas chromatography/mass spectrometry (GCMS) was used to calculate the oxygen consumption and to identify the gases that were generated. The solid residues were analyzed by high-performance liquid chromatography (HPLC) to quantify unburned energetic material. Results showed that DNAN was the most resistant to burning, thus leaving significant quantities of unreacted starting material in the vial. An interesting observation for the IHE formulation was that DNAN also inhibited the combustion of NTO and RDX. The gases emitted during the open burning of IHE components and mixtures included CO, CO2, and N2O as expected, but the proportions differed when the components and mixture were compared, reflecting the influence of DNAN on the burning behavior. From our data, we concluded that open-burning DNAN-based formulations is an environmentally unfavorable waste-management practice for the disposal of IHEs mainly due to generation of solid residues as well as unburnt DNAN. 相似文献