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Kapp N Kreyling W Schulz H Im Hof V Gehr P Semmler M Geiser M 《Microscopy research and technique》2004,63(5):298-305
Epidemiologic studies have associated cardiovascular morbidity and mortality with ambient particulate air pollution. Particles smaller than 100 nm in diameter (ultrafine particles) are present in the urban atmosphere in very high numbers yet at very low mass concentration. Organs beyond the lungs are considered as targets for inhaled ultrafine particles, whereby the route of particle translocation deeper into the lungs is unclear. Five rats were exposed to aerosols of ultrafine titanium dioxide particles of a count median diameter of 22 nm (geometric standard deviation, GSD 1.7) for 1 hour. The lungs were fixed by intravascular perfusion of fixatives immediately thereafter. TiO(2) particles in probes of the aerosol as well as in systematic tissue samples were analyzed with a LEO 912 transmission electron microscope equipped with an energy filter for elemental microanalysis. The characteristic energy loss spectra were obtained by fast spectrum acquisition. Aerosol particles as well as those in the lung tissue were unambiguously identified by electron energy loss spectroscopy. Particles were mainly found as small clusters with a rounded shape. Seven percent of the particles in the lung tissue had a needle-like shape. The size distribution of the cluster profiles in the tissue had a count median diameter of 29 nm (GSD 1.7), which indicates no severe clustering or reshaping of the originally inhaled particles. Electron energy loss spectroscopy and related analytical methods were found to be suitable to identify and localize ultrafine titanium dioxide particles within chemically fixed and resin-embedded lung tissue. 相似文献
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O. Univ. Prof. Dipl.-Ing. Dr. Wolfhard Wegscheider 《BHM Berg- und Hüttenm?nnische Monatshefte》2012,157(6-7):230-235
The development of analytical chemistry in the past decades has provided the raw materials industry with a wealth of new methods and procedures for the characterization of raw, intermediate and final products. The greatest advances were made in trace and micro analytical methods. These are now routinely available at reasonable cost and turnaround times. Equally significant for the industry is the development of process analytical methods for bulk properties that provide crucial information for successful automation of complex processes. 相似文献
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Molecular-dynamics simulations on ion-beam deposition of boron nitride are presented. A realistic Tersoff-like potential energy functional for boron nitride, which was specially fitted to ab initio-data, has been used. The impact of energetic boron and nitrogen atoms on a c-BN target is simulated with energies ranging from 10 to 600 eV. The structural analysis of the grown films shows that a loose, dominantly sp2-bonded structure arises at high ion flux. In no case the formation of a sp3-bonded phase is observed, but the obtained films partially reveal textured basal planes as found in experiment. Two different growth regimes are identified for ion energies above and below 100 eV. 相似文献
6.
Weber Nathan; Brewer Neil; Wells Gary L.; Semmler Carolyn; Keast Amber 《Canadian Metallurgical Quarterly》2004,10(3):139
Data are reported from 3,213 research eyewitnesses confirming that accurate eyewitness identifications from lineups are made faster than are inaccurate identifications. However, consistent with predictions from the recognition and search literatures, the authors did not find support for the "10-12-s rule" in which lineup identifications faster than 10-12 s maximally discriminate between accurate and inaccurate identifications (D. Dunning & S. Perretta, 2002). Instead, the time frame that proved most discriminating was highly variable across experiments, ranging from 5 s to 29 s, and the maximally discriminating time was often unimpressive in its ability to sort accurate from inaccurate identifications. The authors suggest several factors that are likely to moderate the 10-12-s rule. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
Marita Wittkowski Werner Baltes Wolfhard Krönert und Rudolf Weber 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1983,177(6):447-453
Zusammenfassung Es wird eine Phasenumkehr-HPLC-Methode beschrieben, die es gestattet, dieAlternaria-Toxine Alternariol (AOH), Alternariolmonomethylether (AME), Altenuen (ALT) und Altertoxin I (ATX-I) in Obst- und Gemüseerzeugnissen mit guter Empfindlichkeit zu bestimmen. Die Ergebnisse werden dünnschichtchromatographisch abgesichert. Sie wurde an ca. 50 Handelsprodukten Bowie an ca. 20 verschimmelten Früchten erprobt. Keines der Handelsprodukte war mit den o. g. Mykotoxinen kontaminiert, während zwei der verschimmelten Proben (Äpfel) 160 ppb AOH, bzw. 250 ppb AME enthielten.
Determination of alternaria toxins in fruit and vegetable products
Summary A reverse phase HPLC method for the determination of theAlternaria mycotoxins alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT) and altertoxin I (ATX-I) in fruit and vegetable products is described. The procedure has good sensitivity. The results are corroborated by TLC. About 50 commercial products and about 20 mouldy fruits were analysed. None of the commercial products was contaminated with the toxins whereas two of the mouldy samples (apples) contained 160 ppb AOH respectively 250 ppb AME.相似文献
8.
Adrian Keller Stefan Facsko Wolfhard Möller 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(4):656-659
The evolution of nanoscale ripple patterns during sub-keV ion sputtering of thermally grown, fused and single crystalline SiO2 surfaces has been investigated by means of atomic force microscopy. For all three materials, different dependencies of the ripple wavelength and the surface roughness on the ion fluence have been found. Within the Bradley-Harper model of pattern formation, the observed differences are consistent with different amounts of surface and near-surface mass transport by ion-enhanced viscous flow which might result from different surface energies of the SiO2 specimens. 相似文献
9.
Alexander Semmler Susanna Moskau Andreas Grigull Susan Farmand Thomas Klockgether Yvo Smulders Henk Blom Bernd Zur Birgit Stoffel-Wagner Michael Linnebank 《Nutrition journal》2010,9(1):1-4
Background
Several studies demonstrated an association of homocysteine plasma levels and the plasma lipoprotein profile. This cross-sectional pilot study aimed at analyzing whether blood levels of the two important cofactors of homocysteine metabolism, folate and vitamin B12, coincide with the lipoprotein profile.Methods
In a retrospective single center approach, we analyzed the laboratory database (2003-2006) of the University Hospital Bonn, Germany, including 1743 individuals, in whom vitamin B12, folate and at least one lipoprotein parameter had been determined by linear multilogistic regression.Results
Higher folate serum levels were associated with lower serum levels of low density lipoprotein cholesterol (LDL-C; Beta = -0.164; p < 0.001), higher levels of high density lipoprotein cholesterol (HDL-C; Beta = 0.094; p = 0.021 for trend) and a lower LDL-C-C/HDL-C-ratio (Beta = -0.210; p < 0.001). Using ANOVA, we additionally compared the individuals of the highest with those of the lowest quartile of folate. Individuals of the highest folate quartile had higher levels of HDL-C (1.42 ± 0.44 mmol/l vs. 1.26 ± 0.47 mmol/l; p = 0.005), lower levels of LDL-C (3.21 ± 1.04 mmol/l vs. 3.67 ± 1.10 mmol/l; p = 0.001) and a lower LDL-C/HDL-C- ratio (2.47 ± 1.18 vs. 3.77 ± 5.29; p = 0.002). Vitamin B12 was not associated with the lipoprotein profile.Conclusion
In our study sample, high folate levels were associated with a favorable lipoprotein profile. A reconfirmation of these results in a different study population with a well defined status of health, diet and medication is warranted. 相似文献10.
Ulrich Semmler Michael Bräunig Welf-Guntram Drossel Gerhard Schmidt Volker Wittstock 《Production Engineering》2014,8(4):543-550
Challenges for machining include greater and greater material removal rates coupled with an increase in the use of difficult to machine materials, as well as environmental-friendly dry or minimum quantity lubrication machining, small manufacturing batches and frequently changed manufacturing orders. These trends are accompanied by high temperatures in the machining process and large, variable heat flows causing thermo-elastic displacements of the tool, the workpiece and the clamping devices. Although the displacements are small, in the range of a few micrometers, they have assumed more and more importance because of growing requirements for manufacturing accuracy. Thermo-elastic displacements of the tool due to heat flow during machining are investigated and analysed in this paper. Temperatures and displacements are measured on a test bed equipped with measuring instruments. The identification of the thermal boundary and contact conditions is supported by finite element models. Knowledge of the heat flows resulting from the machining process is a prerequisite for control of and compensation for displacements. Since these heat flows either cannot be measured or can only be measured with enormous effort, heat flows are determined by means of numerical simulation of the machining process itself. This strategy has been previously used as a systematic approach for turning in orthogonal cutting conditions. However, further investigations are needed for oblique turning conditions, milling and drilling operations. 相似文献