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1.
ME Hoatlin FE Ferro RW Geib MT Fox SL Kozak D Kabat 《Canadian Metallurgical Quarterly》1995,69(2):856-863
Although the Friend virus-encoded membrane glycoprotein (gp55) activates erythropoietin receptors (EpoR) to cause erythroblastosis only in certain inbred strains of mice but not in other species, mutant viruses can overcome aspects of mouse resistance. Thus, mice homozygous for the resistance allele of the Fv-2 gene are unaffected by gp55 but are susceptible to mutant glycoproteins that have partial deletions in their ecotropic domains. These and other results have suggested that proteins coded for by polymorphic Fv-2 alleles might directly or indirectly interact with EpoR and that changes in gp55 can overcome this defense. A new viral mutant with an exceptionally large deletion in its ecotropic domain is now also shown to overcome Fv-2rr resistance. In all cases, the glycoproteins that activate EpoR are processed to cell surfaces as disulfide-bonded dimers. To initiate analysis of nonmurine resistances, we expressed human EpoR and mouse EpoR in the interleukin 3-dependent mouse cell line BaF3 and compared the abilities of Friend virus-encoded glycoproteins to convert these cells to growth factor independence. Human EpoR was activated in these cells by erythropoietin but was resistant to gp55. However, human EpoR was efficiently activated in these cells by the same viral mutants that overcome Fv-2rr resistance in mice. By construction and analysis of human-mouse EpoR chimeras, we obtained evidence that the cytosolic domain of human EpoR contributes to its resistance to gp55 and that this resistance is mediated by accessory cellular factors. Aspects of host resistance in both murine and nonmurine species are targeted specifically against the ecotropic domain of gp55. 相似文献
2.
M. Bechelany A. Brioude P. Stadelmann G. Ferro D. Cornu P. Miele 《Advanced functional materials》2007,17(16):3251-3257
We present a simple process for the fabrication of very long SiC‐based coaxial nanocables (NCs). The versatility of this technique is confirmed by the ability to change the chemical composition of the NC outer layers from silica to carbon and boron nitride. The NCs consist of a SiC core approximately 30 nm in diameter with lengths up to several hundred of nanometers. The thickness of the coating is in the range 2–10 nm. The morphology and structural characterization of the NCs is investigated by scanning electron microscopy (SEM) and high‐resolution transmission electron microscopy (HRTEM), respectively, and their chemical composition is probed by electron energy loss spectroscopy (EELS). A vapor–solid growth mechanism is proposed to explain the growth of SiC‐based NCs of various chemical compositions, depending on the chemical nature of the vapor phase. Because of the large quantity of very long and interlaced NCs produced during the synthesis, the macroscopic aspect of the as‐grown material is like a self‐supported felt. 相似文献
3.
The adsorption of molecular and atomic hydrogen as well as other molecules in the atmosphere on vacancies in the (0 0 0 1) graphite surface are investigated using density functional theory. Atomic hydrogen adsorbs with energies ranging from 4.7 to 2.3 eV. The validity of the model is confirmed by the good agreement between calculated vibrational spectra and those of high-resolution electron energy loss spectroscopy. It is shown that molecular hydrogen dissociates with a barrier of 1.1 eV on this model system. Water and oxygen also dissociate with respective barriers of 1.6 and 0.2 eV. Carbon dioxide and nitrogen have no interaction with the defect whereas carbon monoxide is incorporated into the vacancy with an activation energy of 1.5 eV. A comparison is made with the reactivity of graphene edges, both zigzag and armchair. 相似文献
4.
5.
Black rice husk ash (BRHA) and white rice husk ash (WRHA) were incorporated into natural rubber (NR) using a laboratory‐size two‐roll mill. A conventional vulcanization system (CV) was chosen and cure studies were carried out on a TI‐100 Curometer. The torque curves were obtained at 150, 160, 170, and 180°C. The overall rate and the apparent activation energy for the vulcanization process were calculated for each compound assuming that vulcanization follows first‐order kinetics. For comparison purposes, two commercial fillers, precipitated silica (Zeosil‐175) and carbon black (N762), were also used. It was observed that addition of WRHA to NR compounds increased the cross‐linking rate and lowered the apparent activation energy more markedly than the other fillers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1194–1203, 2003 相似文献
6.
A cyclic voltammetric study of the behaviour of Br– and Br–
3 at Pt electrodes, in the potential range between hydrogen and oxygen evolution, is described. Different experiments were carried out, in the presence of Br– and Br–
3, in which the ratio between the species has been kept constant and equal to 1. The halide concentration was varied between 4 × 10–6 and 1 × 10–3 and mol dm–3, at constant ionic strength, in 1 M HclO4 as well as in 1 M NaClO4 adjusted to a pH of 2. Underpotential deposition of Br is observed at potentials as low as –0.125 V vs SCE. The adsorption parameters of Br species were determined from the adsorption/desorption peak pair in the hydrogen adsorption/desorption region, and from the oxide reduction peak data. In the absence of oxygen adsorption, a relatively high coverage of the electrode surface is attained. A Langmuir-type adsorption is observed under the different experimental conditions. 相似文献
7.
Key experiments were carried out on the three Al–R–Mg (R=Gd,Dy,Ho) systems and the results obtained used for the thermodynamic optimisation reported in a separate paper in this issue [Caccasmani G, De Negri S, Saccone A, Ferro R. Intermetallics this issue.]. The samples were characterized by differential thermal analysis (DTA), X-ray powder diffraction (XRD), light optical microscopy (LOM), scanning electron microscopy (SEM) and quantitative electron probe microanalysis (EPMA). The isothermal sections at 400 °C are all characterized by extended homogeneity regions at a constant rare earth content. The extension of the (Mg,Al)R solid solution, cP2-CsCl type, varies with the R atomic number. Ternary compounds (τ) of Al2(R,Mg) stoichiometry (hexagonal Laves phases with MgNi2-type structure) have been found to exist at 400 °C in all the systems. Their temperatures of formation were detected by DTA measurements. 相似文献
8.
H. Flandorfer A. Kostikas P. Rogl C. Godart M. Giovannini A. Saccone R. Ferro 《Journal of Alloys and Compounds》1996,240(1-2):116-123
The structural and magnetic properties of a series of novel compounds in the ternary Ce---Mg---Y system have been studied by X-ray diffraction. SQUID magnetometry and XAS spectroscopy. The crystal structures of the compounds Ce0.34Y0.67Mg2 and Ce0.49Y0.51Mg4.7 have been refined by the Rietveld technique. Magnetic data are consistent with a tripositive ground state 2F5/2 for the cerium atom. The XAS measurements confirm this result. Crystal field effects are apparent in the magnetic data at temperatures below about 50 K in the compounds with higher Ce concentration. 相似文献
9.
M. Palumbo G. Borzone S. Delsante N. Parodi G. Cacciamani R. Ferro L. Battezzati M. Baricco 《Intermetallics》2004,12(12):442-1372
An optimised set of thermodynamic parameters for the Ce–Ni system has been obtained using the CALPHAD approach. A thorough thermodynamic analysis of the system has been carried out using different calorimetric techniques and the data have been used in the assessment. The free energy of the liquid phase has been described as a function of temperature and composition using a Redlich–Kister polynomial. Solid compounds have been considered as stoichiometric with the exception of the Laves phases. The phase diagram and thermodynamic quantities calculated from assessed parameters agree well with experimental data. 相似文献
10.
Pedro Furtado 《Service Oriented Computing and Applications》2009,3(3):159-169
Typical request processing systems, such as web servers and database servers, try to accommodate all requests as fast as possible,
which can be described as a Best-Effort approach. However, different application items may have different quality-of-service
(QoS) requirements, and this can be viewed as an orthogonal concern to the basic system functionality. In this paper we propose
the QoS-Broker, a middleware for delivering QoS over servers and applications. We show its architecture to support contracts
over varied targets including queries, transactions, services or sessions, also allowing expressions on variables to be specified
in those targets. We also discuss how the QoS-Broker implements basic strategies for QoS over workloads. Our experimental
results illustrate the middleware by applying priority and weighted- fair-queuing based differentiation over clients and over
transactions, and also admission control, using a benchmark as a case-study. 相似文献