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61.
Kazuyuki Kohama Kazuhiro Ito Susumu Tsukimoto Kenichi Mori Kazuyoshi Maekawa Masanori Murakami 《Journal of Electronic Materials》2008,37(8):1148-1157
In our previous studies, thin Ti-rich diffusion barrier layers were found to be formed at the interface between Cu(Ti) films
and SiO2/Si substrates after annealing at elevated temperatures. This technique was called self-formation of the diffusion barrier,
and is attractive for fabrication of ultralarge-scale integrated (ULSI) interconnects. In the present study, we investigated
the applicability of this technique to Cu(Ti) alloy films which were deposited on low dielectric constant (low-k) materials (SiO
x
C
y
), SiCO, and SiCN dielectric layers, which are potential dielectric layers for future ULSI Si devices. The microstructures
were analyzed by transmission electron microscopy (TEM) and secondary-ion mass spectrometry (SIMS), and correlated with the
electrical properties of the Cu(Ti) films. It was concluded that the Ti-rich interface layers were formed in all the Cu(Ti)/dielectric-layer
samples. The primary factor to control the composition of the self-formed Ti-rich interface layers was the C concentration
in the dielectric layers rather than the enthalpy of formation of the Ti compounds (TiC, TiSi, and TiN). Crystalline TiC was
formed on the dielectric layers with a C concentration higher than 17 at.%. 相似文献
62.
Kazuhiro Ito Toshitake Onishi Hidehisa Takeda Kazuyuki Kohama Susumu Tsukimoto Mitsuru Konno Yuya Suzuki Masanori Murakami 《Journal of Electronic Materials》2008,37(11):1674-1680
The fabrication procedure for silicon carbide power metal oxide semiconductor field-effect transistors can be improved through
simultaneous formation (i.e., using the same contact materials and a one-step annealing process) of ohmic contacts on both
the n-source and p-well regions. We have succeeded in the simultaneous formation of Ni/Al ohmic contacts to n- and p-type SiC after annealing at 1000°C for 5 min in an ultrahigh vacuum. Ohmic contacts to n-type SiC were found when the Al-layer thickness was less than about 6 nm, while ohmic contacts to p-type SiC were observed for an Al-layer thickness greater than about 5 nm. Only the contacts with an Al-layer thickness in
the range of 5 nm to 6 nm exhibited ohmic behavior to both n- and p-type SiC, with a specific contact resistance of 1.8 × 10−4 Ω cm2 and 1.2 × 10−2 Ω cm2 for n- and p-type SiC, respectively. An about 100-nm-thick contact layer was uniformly formed on the SiC substrate, and polycrystalline
δ-Ni2Si(Al) grains were formed at the contact/SiC interface. In the samples that exhibited ohmic behavior to both n- and p-type SiC, the distribution of the Al/Ni ratios in the δ-Ni2Si(Al) grains was larger than that observed for any of the samples that showed ohmic behavior to either n- or p-type SiC. Furthermore, the grain size of the δ-Ni2Si(Al) grains in the samples showing ohmic behavior to both n- and p-type SiC was smaller than the grains in any of the samples that showed ohmic behavior to either n- or p-type SiC. Thus, the large distribution in the Al/Ni ratios and a fine microstructure were found to be characteristic of the
ohmic contacts to both n- and p-type SiC. Grains with a low Al concentration correspond to ohmic contacts to n-type SiC, while grains with a high Al concentration correspond to ohmic contacts to p-type SiC. 相似文献
63.
Davi Munhoz Benati Kazuhiro Ito Kazuyuki Kohama Hajime Yamamoto Eugenio José Zoqui 《Metallurgical and Materials Transactions B》2017,48(5):2293-2303
The development of high-quality semisolid raw materials requires an understanding of the phase transformations that occur as the material is heated up to the semisolid state, i.e., its melting behavior. The microstructure of the material plays a very important role during semisolid processing as it determines the flow behavior of the material when it is formed, making a thorough understanding of the microstructural evolution essential. In this study, the phase transformations and microstructural evolution in Fe2.5C1.5Si gray cast iron specially designed for thixoforming processes as it was heated to the semisolid state were observed using in situ high-temperature confocal laser scanning microscopy. At room temperature, the alloy has a matrix of pearlite and ferrite with fine interdendritic type D flake graphite. During heating, the main transformations observed were graphite precipitation inside the grains and at the austenite grain boundaries; graphite flakes and graphite precipitates growing and becoming coarser with the increasing temperature; and the beginning of melting at around 1413 K to 1423 K (1140 °C to 1150 °C). Melting begins with the eutectic phase (i.e., the carbon-rich phase) and continues with the primary phase (primary austenite), which is consumed as the temperature increases. Melting of the eutectic phase composed by coarsened interdendritic graphite flakes produced a semi-continuous liquid network homogeneously surrounding and wetting the dendrites of the solid phase, causing grains to detach from each other and producing the intended solid globules immersed in liquid. 相似文献
64.
Satomura T Kawakami R Sakuraba H Ohshima T 《Journal of Bioscience and Bioengineering》2008,106(1):16-21
Dye-linked D-lactate dehydrogenase activity was found in the crude extract of a continental thermoacidophilic crenarchaeota, Sulfolobus tokodaii strain 7, and was purified 375-fold through four sequential chromatography steps. With a molecular mass of about 93 kDa, this enzyme was a homodimer comprised of identical subunits with molecular masses of about 48 kDa. The enzyme retained its full activity after incubation at 80 degrees C for 10 min and after incubation at pHs ranging from 6.5 to 10.0 for 30 min at 50 degrees C. The preferred substrate for this enzyme was D-lactate, with 2,6-dichloroindophenol serving as the electron acceptor. Using high-performance liquid chromatography (HPLC), the enzyme's prosthetic group was determined to be flavin adenine dinucleotide (FAD). Its N-terminal amino acid sequence was MLEGIEYSQGEEREDFVGFKIKPKI. Using that sequence and previously reported genome information, the gene encoding the enzyme (ST0649) was identified. It was subsequently cloned and expressed in Escherichia coli and found to encode a polypeptide of 440 amino acids with a calculated molecular weight of 49,715. The amino acid sequence of this dye-linked D-lactate dehydrogenase showed higher homology (39% identity) with that of a glycolate oxidase subunit homologue from Archaeoglobus fulgidus, but less similarity (32% identity) to D-lactate dehydrogenase from A. fulgidus. Taken together, our findings indicate that the dye-linked D-lactate dehydrogenase from S. tokodaii is a novel type of FAD containing D-lactate dehydrogenase. 相似文献
65.
66.
Takenori Nitta Takayuki Usui Hiroaki Iino Akira Ohno Jun‐ichi Hanna 《Electrical Engineering in Japan》2021,214(1):10-17
We have designed and synthesized a new liquid crystalline phenylbenzothienobenzothiphene derivative, Ph‐BTBT‐4S‐3, in order to investigate the carrier transport properties in highly ordered smectic liquid crystal phase at a wide temperature range lower than room temperature enough to analyze them. Ph‐BTBT‐4S‐3 exhibits smectic E (SmE) phase, which is the one of highly ordered smectic liquid crystal phases, at the wide temperature range from 200°C to under ?130°C. Thanks to its wide temperature range of SmE phase, we could reveal the carrier transport properties in the low temperature range, which were well explained on the basis of Gaussian disorder model having a Gaussian width, σ, of 87 meV, which was larger than those of typical nonpolar liquid crystals of 40?60 meV and was attributed to additional dipole of a thioether group in the side chain. 相似文献
67.
For 8 carboxy and hydroxy functional acrylic copolymers crosslinked with melamine resin, glass transition temperature (Tg), molecular weight of chain segments between crosslinked point (Mc), and polymer-solvent interaction parameters (χg ) were determined by dynamic mechanical measurements and swelling measurements. Tg increases and Mc decreases with the increase of hydroxyl value and the molecular weight of acrylic copolymers. Tg decreases and Mc increases with the increase of alkyl chain length of acrylate in acrylic copolymers. The film hardness, Tg and polarity of methyl methacrylate (MMA) containing acrylic-melamine-cured films are higher than those of styrene-containing acrylic-melamine-cured films, but both films are almost the same in the degree of crosslinking (maximum loss tangent, tan δmax, and Mc). Tg increases and Mc decreases with the increase of melamine resin content for acrylic-melamine coatings. The cured film consists of the acrylic-melamine segments and the melamine-melamine segments at crosslinking points. The carboxy group enhances the crosslinking reactions at low temperatures. All films crosslinked have single glass transition temperatures and broad damping peaks, which show good compatibility. The values of χg of acrylic copolymer-melamine films in polar and nonpolar solvents depend on the polarity of acrylic composition and the degree of crosslinking. χg values of carboxy functional acrylic-melamine film in any solvents are smaller than that of carboxy and hydroxy functional acrylic-melamine film. χg values of MMA-containing acrylic-melamine film in polar solvents are smaller than those of styrene-containing acrylic-melamine film, but χg values of MMA-containing acrylic-melamine film in nonpolar solvents are larger than those of styrene-containing acrylic-melamine film. χg values of acrylic-melamine film in polar and nonpolar solvents increase with the increase of alkyl chain length of acrylate. The χg values of acrylic-melamine coatings in toluene are less than 0.3 and smaller than those of alkyd coatings. 相似文献
68.
69.
Alerting drivers for self-regulation of attention might decrease crash risks attributable to absent-minded driving. However, no reliable method exists for monitoring driver attention. Therefore, we examined attentional effects on gaze preference for salient loci (GPS) in traffic scenes. In an active viewing (AV) condition requiring endogenous attention for traffic scene comprehension, participants identified appropriate speeds for driving in presented traffic scene images. In a passive viewing (PV) condition requiring no endogenous attention, participants passively viewed traffic scene images. GPS was quantified by the mean saliency value averaged across fixation locations. Results show that GPS was less during AV than during PV. Additionally, gaze dwell time on signboards was shorter for AV than for PV. These results suggest that, in the absence of endogenous attention for traffic scene comprehension, gaze tends to concentrate on irrelevant salient loci in a traffic environment. Therefore, increased GPS can indicate absent-minded driving. PRACTITIONER SUMMARY: The present study demonstrated that, without endogenous attention for traffic scene comprehension, gaze tends to concentrate on irrelevant salient loci in a traffic environment. This result suggests that increased gaze preference for salient loci indicates absent-minded driving, which is otherwise difficult to detect. 相似文献
70.