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排序方式: 共有139条查询结果,搜索用时 15 毫秒
1.
Copper was alloyed with small amounts of Al (0.2, 0.5, 1.0 and 2.0 mass%) to improve the oxidation resistance. Copper (6 N) and the Cu-Al alloys were oxidized at 773-1173 K in 0.1 MPa oxygen atmosphere after hydrogen annealing at 873 K. Continuous very thin Al2O3 layers were formed on the surface of all Cu-Al dilute alloys during the hydrogen annealing. Oxidation resistance of Cu-Al alloys was improved especially for Cu-2.0Al at 773-973 K, while it decreases on increasing the oxidation temperature. Cu-Al alloys followed the parabolic rate law at 1173 K, but most of other cases do not at and below 1073 K. Oxidation resistance for Cu-Al alloys was found relevant to the maintenance of the thin Al2O3 layer at the Cu2O/Cu-Al alloy interface. 相似文献
2.
Chun Li Naoe Isshiki Hiromu Saito Kazufumi Kohno Akinori Toyota 《Polymer Bulletin》2009,63(6):779-788
We investigated the formation of inclusion complexes (ICs) between cyclodextrins (CDs) with different cavity size and polyolefin
(PO) with different side chains by using Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXD)
and differential scanning calorimetry. The analysis of FTIR spectra revealed that the resultants were complexes of CD and
PO, and the analysis of WAXD revealed that the molecules of CD had a channel structure due to the formation of ICs. We found
that IC could not be obtained when the cavity size of CD was small for PO molecules to thread and it was too large for cross-sectional
area of PO molecules. Thus, it was found that PO1 with few side chains could form IC with α-CD, and PO2 with ethyl side chain
could form IC with β-CD and γ-CD, while the PO3 with 2-methyl-propyl side chain could form IC with γ-CD. These results suggest
that the cross-sectional areas of polymer and the cavity size of CDs play critical roles in the formation of ICs. It is only
possible to form ICs when the polymer chains can tread into cavities of CDs, and the space between the polymer and CD is suitable
to provide enough intermolecular interaction to keep the structure of IC stable. 相似文献
3.
4.
The evaporation, carburization and diffusion behavior of Nb-coated Mo and of Nb-coated Ti were investigated in order to estimate the surface characteristics of the coated systems. Nb layers were formed on Mo by both chemical and physical vapor deposition and on Ti by just physical vapor deposition. From the diffusion behavior, interdiffusion coefficients were obtained at 1860°C, 1980°C and 2080°C for the chemically vapor-deposited Nb/Mo system. From evaporation experiments it was found that simultaneous evaporation of Nb and Mo occured at about 2300°C for thick films of Nb on Mo. For thin films of Nb on Mo, the evaporation of both Nb and Mo was confirmed at 1900°C by ion microprobe analysis of the condensate. For Nb/Ti, rapid diffusion of Nb into Ti and evaporation of Ti similar to the case of Nb-Ti alloys were observed. From the carburization study, it was found that an Nb coating appreciably retards the carburization of Ti and Mo. 相似文献
5.
The γ‐cyclodextrin (γ‐CD) inclusion complexes (ICs) with four kinds of polyolefin (PO) as guest molecules were prepared. The crystallization behavior of isotactic polypropylene (iPP) blended with the γ‐CD and γ‐CD–PO ICs was investigated by differential scanning calorimetry, polarized optical microscopy, and light scattering. The iPP blended with the ICs was found to exhibit higher crystallization temperature (TC), smaller spherulites, and faster crystallization rate than those of neat iPP, indicating that the ICs play a role of nucleating agent on the crystallization of iPP and induce accelerated crystallization. The IC with PO having higher TC as guest molecules showed higher nucleation effect than the IC with PO having lower TC as guest molecules. The results suggest that the nucleation effect of these ICs was affected by the kinds of the guest molecules. The higher TC guest molecules could result in higher nucleation effect. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
6.
Jean Dijon Adeline Fournier Pierre David Szkutnik Hanako Okuno Celine Jayet Murielle Fayolle 《Diamond and Related Materials》2010,19(5-6):382-388
A CVD process with a high density of CNTs has been developed on doped silicon material thanks to plasma pre-treatment of the catalyst. With this process small diameter double and triple wall CNTs with an average diameter of 3.8 nm have been grown. The density of the best materials on blanket substrate is larger than 1012 cm? 2. These materials have been successfully integrated in via holes with a diameter ranging between 1 µm and 0.3 µm with an equivalent density. In 140 nm hole diameter large 70 nm bundle formations have been observed. In these bundles a density of CNT walls close to 1013 cm? 2 has been estimated. 相似文献
7.
Development of the Drosophila central nervous system begins with the delamination of neural and glial precursors, called neuroblasts, from the neuroectoderm. An early and important step in the generation of neural diversity is the specification of individual neuroblasts according to their position. In this study, we describe the genetic analysis of the msh gene which is likely to play a role in this process. The msh/Msx genes are one of the most highly conserved families of homeobox genes. During vertebrate spinal cord development, Msx genes (Msx1-3) are regionally expressed in the dorsal portion of the developing neuroectoderm. Similarly in Drosophila, msh is expressed in two longitudinal bands that correspond to the dorsal half of the neuroectoderm, and subsequently in many dorsal neuroblasts and their progeny. We showed that Drosophila msh loss-of-function mutations led to cell fate alterations of neuroblasts formed in the dorsal aspect of the neuroectoderm, including a possible dorsal-to-ventral fate switch. Conversely, ectopic expression of msh in the entire neuroectoderm severely disrupted the proper development of the midline and ventral neuroblasts. The results provide the first in vivo evidence for the role of the msh/Msx genes in neural development, and support the notion that they may perform phylogenetically conserved functions in the dorsoventral patterning of the neuroectoderm. 相似文献
8.
Secondary ion mass spectrometry (SIMS) and glow discharge mass spectrometry (GDMS) were used to determine the impurity concentrations
of hydrogen, carbon, nitrogen, and oxygen elements in Cu films, and the results of SIMS and GDMS were carefully interpreted.
The Cu films were deposited on Si (100) substrates at substrate bias voltages ranging from 0 V to −150 V using a non-mass
separated ion beam deposition method. From the results of SIMS using a Cs− ion beam, as a whole, many high intensity peaks were observed in the Cu films deposited without substrate bias voltage. From
the quantitative GDMS results, these peaks were determined to be signals detected as a cluster state such as CxHx, OxHx, CxOxHx. Therefore, using a combination of these dominant impurities, all the unknown peaks observed in the SIMS results could be
interpreted. Moreover, it was found that the dominant impurities having a great influence on the film purity were hydrogen,
carbon, nitrogen, and oxygen. 相似文献
9.
N Isshiki 《Canadian Metallurgical Quarterly》1998,108(12):1761-1766
OBJECTIVE: A number of modifications in laryngoplastic phonosurgery have recently been proposed. This report is intended to clarify the concept on which the surgery should be based, vocal mechanics, for further rational development of the surgery. STUDY DESIGN: The results of various previous surgeries were compared. In an attempt to elucidate what makes the difference in the results, simulation of voice production was conducted with the use of excised larynges. METHODS: Excised larynges were mounted on a tube so as to be blown from below. Experimental variables in the model included the glottal area initially set, stiffness of the vocal folds, and subglottal pressure. The conditions under which the voice became hoarse were examined. RESULTS: The voice became hoarse under the following major conditions: 1) the initial glottal area exceeded a certain value, 2) stiffness was too high, and 3) the glottis was too tightly closed. Clinical representation for each condition was made, particularly for excessively tight glottal closure such as in spasmodic dysphonia. A new type of surgical treatment for spasmodic dysphonia, lateralization thyroplasty, was briefly reported, which restored the voice to normal without recurrence for 1 year at the time of this writing. CONCLUSIONS: A potential new type of laryngoplastic phonosurgery should be conformed to the mechanics of voice production. In treating dysphonia, it is often necessary to switch from etiologic or radical treatment, if infertile, to symptomatic treatment instead, at the level of mechanics. 相似文献
10.
Monolithic integration of InGaAsP/InP distributed feedback laser and electroabsorption modulator by vapor phase epitaxy 总被引:2,自引:0,他引:2
Suzuki M. Noda Y. Tanaka H. Akiba S. Kushiro Y. Isshiki H. 《Lightwave Technology, Journal of》1987,5(9):1277-1285
Monolithic integration of a 1.55-μm InGaAsP/InP distributed feedback (DFB) laser and an electroabsorption (EA) modulator was studied. The difference between the lasing photon energy and the bandgap energy of the modulator waveguide was designed to be 30-40 meV, taking into account the linewidth-enhancement factor and the zero-bias absorption loss. The integrated devices were grown by three-step vapor phase epitaxy (VPE). The CW threshold current at 20°C of the DFB laser part with a buried heterostructure was 30-60 mA and the breakdown voltage of the modulator part with a strip-loaded stripe geometry was 20-40 V, and these values indicated satisfactory crystal quality in the VPE epitaxial layers. The operating voltage of the modulator to give on:off ratios of 10:1 and 100:1 was 1.5- 4 V and 2.5-6.5 V, respectively, depending on the length in the range200-500 mu m. A 3-dB bandwidth of about 2.5 GHz and a linewidth-enhancement factor of about 1.6 were obtained for the integrated modulator. 相似文献