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141.
142.
Effect of weld metal mis-match on toughness requirements: Some simple analytical considerations using the Engineering Treatment Model (ETM) 总被引:2,自引:0,他引:2
Karl-Heinz Schwalbe 《International Journal of Fracture》1992,56(3):257-277
The recently introduced Engineering Treatment Model (ETM) relates the crack tip opening displacement (CTOD) to the applied load or strain for work hardening materials. The formalisms of ETM were applied to a transverse welded wide plate with a crack in the weld metal. Both the base material and the weld metal were regarded as power law hardening materials. It can be shown that differences in the plastic properties of the weld metal and base material, respectively, significantly affect the CTOD. Quantitative relations are given for the CTOD of a crack in the weld metal normalised by the CTOD a crack in the base material would exhibit. An important result is that the characterisation of a non-matching weld metal by the matching factor M only is not sufficient since work hardening plays an important role.From this, requirements for minimum weld metal toughness can be established in order to make the toughness performance of the weldment no worse than that of the base material. 相似文献
143.
Karl-Heinz Engel Martina Bohnen Roland Tressl 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1989,188(2):144-147
Summary The lipase-catalysed esterification of racemic heptan-2-ol in organic solvent has been investigated. Porcine pancreas lipase, suspended in heptane, preferentially catalyses the synthesis of (R)-2heptyl butyrate starting from (R,S)-heptan-2-ol and butyric acid. The distribution of the reaction products and the stereochemical course of the esterification have been investigated by means of capillary gas chromatographic methods.
Lipase-katalysierte Veresterung von Heptan-2-ol durch Trennung der Enantiomere in organischem Lösungsmittel
Zusammenfassung Die Lipase-katalysierte Veresterung von racemischen Heptan-2-ol in organischem Lögsmittel wurde untersucht. Ausgehend von Buttersäure und (R,S)-Heptan-2-ol katalysiert in Heptan suspendierte Schweinepankreas-Lipase bevorzugt die Bildung von (R)-Buttersäure-2-heptylester. Die quantitative Verteilung der Produkte und der stereochemische Verlauf der Reaktion wurde mittels capillargaschromatographischer Methoden untersucht.相似文献
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Karl-Heinz Moos 《大分子材料与工程》1983,111(1):165-177
The influence of the variation of the molecular weight, of the mold temperature and of the temperature of the melt during injection molding as well as of the addition of nucleating agents on the morphology and the mechanical properties of injection molded PA 66 samples was studied. The orientation of the needle-shaped phthalocyanine particles, acting as nucleating agents, which took place preferably in the shear zone, gave rise to the formation of row nucleated spherulites. The mechanical properties remained unchanged although the degree of the crystal orientation increased. The addition of a specific nucleating agent for polyamides resulted in a decrease of the elongation to break by 80% and in an increase of the yield strength by 15%. This behaviour can be attributed to the formation of small spherulites having a diameter of about 3?4 μm as compared to the original sample which is characterized by diameters of spherulites of about 30 μm. The observation that the addition of nucleating agents to PA 66 does not lead to a distinct shift in the temperature of the crystallization exotherm in the DSC-experiment indicates that this method is not beyond doubt in determining the nucleating capacity of a nucleating agent with respect to induced changes in the morphology and the mechanical properties. 相似文献
147.
Joachim Müller Sven Simon Uwe Motschmann Josef Schüle Karl-Heinz Glassmeier Gavin J. Pringle 《Computer Physics Communications》2011,182(4):946-966
The interaction between magnetized space plasmas and obstacles like comets, asteroids or planets is determined by a variety of physical processes that occur simultaneously on significantly different length and time scales. Frequently the dynamics of individual ions play a key role for the shape of the interaction region: strong velocity shear between light and heavy plasma constituents, non-Maxwellian particle distributions due to pick up and asymmetries in the magnetic field topology are crucial in determining this type of interaction. Covering these processes is beyond the scope of any Magnetohydrodynamic (MHD) model. In order to account for these effects we have developed a new adaptive hybrid code A.I.K.E.F. (Adaptive Ion-Kinetic Electron-Fluid). The code operates on Cartesian meshes that can adapt to the physical structures in both, space and time. To the authors' knowledge, there is no other adaptive hybrid simulation code in space plasma physics to the present day. Adaptivity is implemented by means of Hybrid-Block-AMR, that is individual octs are refined rather than entire blocks, where an oct is one eighth of a block. In order to account for a reasonable number of particles in each cell, particles are refined via splitting and merging. Both procedures conserve mass, momentum and kinetic energy. The code is implemented in C++ and efficiently parallelized for distributed systems by means of the Message Passing Interface (MPI). In order to demonstrate the validity of our newly developed code we have applied it to a series of fundamental test scenarios. On the one hand we demonstrate that the dispersion relation as well as the propagation characteristics of MHD and whistler mode waves are quantitatively reproduced by our simulation code. Wave propagation remains unaffected when traveling through regions that include different refinement levels. On the other hand we verify that the results obtained on high resolution uniform meshes are identical to the results from adaptive simulations that use coarse base meshes but include various levels of refinement. A remarkable speedup could be observed: the adaptive simulations required 71 times less CPU-hours than the uniform mesh simulations. Finally, we present a first series of global, three-dimensional simulations for the interaction of Mercury with the solar wind and a real time study of Titan's plasma interaction during a magnetosheath excursion. 相似文献
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149.
Phase relations and lattice constants in the MgO–Al2 O3 –Ga2 O3 system at 1550°C have been determined experimentally. In a large part of this system, only a nonstoichiometric spinel is stable. Compositions as extreme as 12.5 mol% MgO–20.5 mol% Ga2 O3 –67 mol% Al2 O3 for a homogeneous spinel are possible. In the bordering phase diagrams of MgO–Al2 O3 and MgO–Ga2 O3 , the composition of the spinel is as high as 63 mol% Al2 O3 or Ga2 O3 , respectively. The contributions of all simple ionic exchange reactions on the lattice constant of the spinel have been deduced from X-ray diffractometry data. 相似文献
150.
Karl-Heinz Ernst 《Israel journal of chemistry》2017,57(1-2):24-30
In a paper addressing the problem that the majority of chiral compounds crystallize as racemates instead of conglomerates, Jack Dunitz coined the expression “Wallach's Rule”. The paper gives credit to Wallach's publication in Liebigs Annalen der Chemie in 1895, in which, among other work, a comparison of crystal density of racemates and their homochiral analogues was reported. Of the nine compounds investigated, eight showed higher densities for the racemates. Although Wallach was the only author of the Annalen paper, it was not Otto Wallach, but Theodore Liebisch, Wallach's colleague from the mineralogy institute in Göttingen at that time, who performed the experiments and reported these results. Short overviews about the CVs of the contemporaries Wallach and Liebisch, as well as Liebisch's postdoc Sommerfeld, are presented. It is discussed whether Wallach or Liebisch had the idea to study crystal densities and which one of the two scientists should be properly credited with proposing “Wallach′s Rule”. 相似文献