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991.
992.
Yoshiyuki Kaji Manfred Rödig Kenji Kikuchi 《International Journal of Pressure Vessels and Piping》1998,75(15):1065-1074
Creep crack growth tests were carried out under several temperature and stress conditions for Fe-based superalloy Alloy 800 and the Q* parameter was applied to an evaluation of the crack growth rate at elevated temperatures for DEN and CT specimens. Creep fracture times were evaluated with the parameter derived by integrating the creep crack growth rate formula expressed in terms of the Q* parameter for DEN, CT and smooth specimens of Alloy 800 under several temperature and stress conditions. It was found that the creep crack growth rate for CT specimens is represented as the different data bands by the Q* parameter for DEN specimens. However, it can be evaluated by parallel movement along the Q* axis in the Q* parameter-da/dt diagram for Alloy 800. The parameter {T(log10tf+20)×10−3} derived from the Q* parameter can compare and evaluate the difference in specimen shape and loading mechanism on creep fracture time using the identical parameter for Alloy 800. 相似文献
993.
Ian MacLaren Rowland M. Cannon Mehmet A. Gülgün Rayisa Voytovych § Nicoletta Popescu-Pogrion ¶ Christina Scheu Ulrike Täffner Manfred Rühle 《Journal of the American Ceramic Society》2003,86(4):650-59
Abnormal grain growth without strong anisotropy or faceting of the grains has been observed in high-purity yttria-doped alumina specimens, often starting at the surface and spreading right through the bulk at higher sintering temperatures. This appears to occur because of an interaction between Si contamination from sintering and the yttria doping; no such effect is seen for undoped samples. Similar microstructures were observed after deliberate Y/Si codoping. Analytical STEM showed that some grain boundaries bordering on large grains contained more Si than Y. HRTEM and diffuse dark-field imaging revealed thin (0.5–0.9 nm) disordered layers at some boundaries bordering large grains. It appears that Si impurities are accumulating at some boundaries and together with the Y inducing a grain boundary structural transformation that accounts for the dramatically increased mobility of these boundaries. 相似文献
994.
M Kaps J Hansen M Weiher K Tiffert I Kayser DW Droste 《Canadian Metallurgical Quarterly》1997,28(2):322-325
BACKGROUND AND PURPOSE: Microembolic signals (MES) are frequently observed by transcranial Doppler ultrasound after prosthetic heart valve implantation. Whether these MES are due to solid or gaseous particles is uncertain. We hypothesized that MES are gaseous and that if they are due to cavitation effects, their occurrence should respond to changes of dissolved oxygen concentration in the blood. METHODS: Transcranial monitoring of MES was performed in five patients with prosthetic aortic valves, who inspired 100% oxygen through a facial mask. In one patient 100% oxygen was administered under hyperbaric (2.5 kPa) conditions in a hyperbaric chamber. RESULTS: Inspiration of 100% oxygen reduced the total number of MES from 96/30 min to 2/30 min. Increasing the concentration of dissolved oxygen in the hyperbaric chamber led to an increase from 0.3 MES per minute (1.0 kPa) to 0.9 MES per minute (2.5 kPa). CONCLUSIONS: The dependence of occurrence of MES in patients with prosthetic cardiac valves on the oxygen partial pressure in blood provides strong evidence that these microemboli are gaseous. 相似文献
995.
Mikko Ritala Markku Leskel Lauri Niinist Thomas Prohaska Gernot Friedbacher Manfred Grasserbauer 《Thin solid films》1994,250(1-2):72-80
The structural development of HfO2 thin films grown from HfCl4 and water onto glass substrates by atomic layer epitaxy at 500 °C was studied with X-ray diffraction, atomic force microscopy and scanning electron microscopy. The films were found to contain two regions of different crystallinity: a thin amorphous starting layer and a subsequent preferentially oriented polycrystalline layer. The films were built up of densely packed grains. Substantial surface roughening occurred along with increasing film thickness. The films were chlorine free as analyzed by Rutherford backscattering spectrometry. 相似文献
996.
997.
Christoph Leyens Klaus Fritscher Manfred Peters Wolfgang A. Kaysser 《Oxidation of Metals》1995,43(3-4):329-352
A novel, low-expansion experimental Ni–Cr–Al–Ti–Si bond-coating alloy was investigated in the as-cast state concerning its phase stability, oxidation resistance in air, and interdiffusion with single-crystal IN-100 at 900, 1000, and 1100°C. Isothermal oxidative thermogravimetry was employed up to 500 hr. Interdiffusion was compared to a commercial Ni–Co–Cr–Al–Y alloy on IN-100. Oxidized Ni–Cr–Al–Ti–Si specimens and diffusion couples were characterized by metallography, SEM, EDX, XRD, and XRF. The Ni–Cr–Al–Ti–Si alloy provides good oxidation resistance in air at least up to 1000°C. The alloy is an alumina former. Due to its coarse microstructure, other oxides (e.g., rutile) may form and considerably dominate the oxidation behavior. The kinetics of oxidation were correlated with temperature, formation of phases, and morphology of oxides. Interdiffusion fluxes between Ni–Cr–Al–Ti–Si and IN-100 were mainly directed to the superalloy. They were faster than in Ni–Co–Cr–Al–Y/IN-100 diffusion couples. 相似文献
998.
Zusammenfassung In dieser Arbeit wird die Verwendung der diskreten Simulation zur Bestimmung von Kapazitäten und maximalen Produktionsmengen einer neu errichtenden Fertigungsanlage beschrieben. Aufgrund fehlender Erfahrungswerte ist es dabei notwendig, die Kapazität jeder einzelnen Maschine im Produktionsprozeß bzw. jeder Produktionsstufe zu bestimmen. Davon ausgehend wird die maximale Produktionsmenge der gesamten Fertigungsanlage ermittelt. Die Analyse des Fertigungssystems zeigt, daß die Lage der Engpässe sehr stark vom tatsächlichen Produktionsprogramm abhängig ist. Aus diesem Grund wird das maximale Kapazitätsangebot der einzelnen Produktionsstufen getrennt bestimmt und als Restriktionen bei der Einlastung der einzelnen Aufträge verwendet. Ein heuristisches Verfahren zum Festlegen des Produktionsprogramms unter Beachtung aller durch verschiedene Simulationsläufe ermittelten Restriktionen bildet den Abschluß der Arbeit. 相似文献
999.
Prof. Dr.-Ing Manfred Weck Dipl. Math. Margot Ruschitzka 《Forschung im Ingenieurwesen》1992,58(6):146-151
Zusammenfassung Der Einsatz von Finite-Elemente-Optimierungsprogrammen für die konstruktive Auslegung von Bauteilen ist mit gro?em Rechenaufwand
und Speicherplatzbedarf verbunden. Die Dekompositionsstrategie stellt ein effizientes Verfahren dar, das zu einer drastischen
Reduzierung der Rechenzeiten bei der L?sung von Problemen der Gewichtsminimierung führt. Darüber hinaus verringert sich der
immens hohe Bedarf an Plattenplatz und nicht zuletzt wird ein schnelleres Konvergenzverhalten bei der Optimierung erreicht.
Die in diesem Beitrag vorgestellten Arbeiten sind Gegenstand des von der Deutschen Forschungsgemeinschaft (DFG) gef?rderten
Forschungsprojektes “Entwicklung von Dekompositionsstrategien für die Strukturoptimierung unter Einsatz von Parallelrechnern? 相似文献
1000.
The resonant modes of a circular cylindrical cavity resonator containing a coaxial circular ferrite rod are investigated. The ferrite sample is partially magnetized by means of a constant external magnetic field applied along its axis. A computer program for deriving the resoant frequencies of this system as a function of the externally applied magnetic field and of the sample radius has been developed. Results for the special cases of the tm010 and tm110 modes are presented. The possible application of such a cavity resonator for the remote sensing of magnetic fields is discussed. 相似文献