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1.
A simple template‐free high‐temperature evaporation method was developed for the growth of crystalline Si microtubes for the first time. As‐grown Si microtubes were characterized using X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and room‐temperature photoluminescence. The lengths of the Si tubes can reach several hundreds of micrometers; some of them have lengths on the order of millimeters. Each tube has a uniform outer diameter along its entire length, and the typical outer diameter is ≈ 2–3 μm. Most of the tubes have a wall thickness of ≈ 400–500 nm, though a considerable number of them exhibit a very thin wall thickness of ≈ 50 nm. Room‐temperature photoluminescence measurement shows the as‐synthesized Si microtubes have two strong emission peaks centered at ≈ 589 nm and ≈ 617 nm and a weak emission peak centered at ≈ 455 nm. A possible mechanism for the formation of these Si tubes is proposed. We believe that the present discovery of the crystalline Si microtubes will promote further experimental studies on their physical properties and smart applications. 相似文献
2.
D. Golberg P.S. Dorozhkin Y. Bando M. Mitome C.C. Tang 《Diamond and Related Materials》2005,14(11-12):1857
Various multi-walled nanotubes in the B–C–N system are thoroughly investigated using a JEOL-3100FEF high-resolution field emission transmission electron microscope operating at 300 kV and equipped with an in-column built Omega filter. Spatially-resolved B, C and N elemental maps of the nanotubes are constructed. It is realized that a wide variety of tubular arrays composed of B, C and N atoms may exist in the system. Sandwich-like BN-rich and C-rich alternating tubular shells, graphitic C layers inside and outside of pure BN shells induced either by surface contamination, or electron beam irradiation, separation of C-rich and BN-rich tubes and/or BN particles within tubular bunches may take place. One should carefully take these effects into account while analyzing nanotube physical properties, e.g., electrical or optical, rather than simply rely on electron energy loss spectra typically collected from B, C and N containing nanostructures as a whole. Striking dependence of an individual nanotube electrical conductivity on tubular shell chemistry is demonstrated using I–V curve recording in an atomic force microscope. 相似文献
3.
Preparation of polyimide-epoxy composites 总被引:2,自引:0,他引:2
Kevin Gaw Mitsutoshi Kikei Masa-aki Kakimoto Yoshio Imai 《Reactive and Functional Polymers》1996,30(1-3):85-91
The formation of a three dimensional network of crosslinked epoxy leads all unmodified epoxies to have inherent brittleness and relatively low degradation temperatures. Polyimides, on the other hand, are widely used for applications that require high degrees of flexibility and thermal resistance. Here, we have focused on the preparation of epoxy systems cured with polyamic acids instead of traditional amino-group-containing hardening agents. The cure behavior and potential reaction mechanisms of EPON 828 resin and polyamic acid mixtures were evaluated by DSC and TGA. Thermal analysis showed a complex reaction sequence taking place in the mixture and also determined the extent of reaction of the polyamic acid with itself and the competitive reaction of the polyamic acid with the epoxy. The compositions of the mixtures were varied to see the dependence of the cure behavior on component concentrations. Solutions of the two components did not phase separate and also phase separation was not apparent either optically or microscopically in the cured samples. This phase behavior was attributed to a unique in situ reaction. A novel solvent system for the polyamic acid precursor was also used. 相似文献
4.
Yoshio Yamashita Hideyuki Jinbo Ryuji Kawazu Takateru Asano Hiroshi Umehara 《Polymer Engineering and Science》1991,31(12):855-859
LMR-UV (“low molecular weight resist for uv lithography”), a naphthoquinone-diazide sulfonic acid ester of a novolak resin, is a negative working resist. The mechanism of insolubilization of LMR-UV is based on the facts that the naphthoquinone-diazide moiety is decomposed to indenecarboxylic acid (polar compound) by photolysis upon UV irradiation and that the irradiated resist film insolubilizes in a non-polar developer. LMR-UV reliably forms 0.6 μm lines and spaces over a reflective substrate with steps by using a g-line stepper having a 0.35 NA lens. 0.6 μm-wide aluminum patterns over topography are obtained by use of g-line exposure and reactive ion etching. By use of an i-line aligner (NA = 0.42), LMR-UV resolves 0.25 μm space patterns with overhang profiles. The profiles are due to the large absorption coefficient of 3.8 μm?1. 0.3 μm wide aluminum patterns are formed by i-line exposure and lift-off metallization. 相似文献
5.
6.
Kiichi Oda Hirohide Yata Tetsuo Yoshio Kazuo O-Oka Kohei Oda 《Journal of Materials Science》1986,21(2):637-642
Ta100-x
B
x
alloy films were prepared by r.f.-sputtering in the chemical composition range 45 x 77. Ta100-x
B
x
(45 x 58) films consist of the amorphous phase, while the TaB2 crystal phase was observed in Ta100-x
B
x
(66 x 77) films. A remarkable preferred orientation with the (001) plane of TaB2 parallel to the film surface was observed in Ta34B66. The d.c. electrical conductivity of Ta100-x
B
x
(45 x 77) films decreases with increasing boron content in the range 6.7 × 103 to 1.3 × 103–1 cm–1. The micro-Vickers hardness of Ta100-x
B
x
(45 x 77) films was in the range 2200 to 2600 kg mm–2. 相似文献
7.
Co-N films in the wide compositional range can be prepared by reactive sputtering. Co-N sputtered films consist of one or two phases, such as CoN, Co2N, Co3N, Co4N and -Co. Co4N phase with a cubic unit cell is observed, and its lattice constant isa = 0.3586 nm. The preferred orientation is observed on the Co-N films, CoN (200) plane, Co4N (1 1 1) plane and -Co (002) plane parallel to the film surface, respectively. Saturation magnetization s of Co-N sputtered film decreases from 160 to 1.7 e.m.u. g–1 with increasing content of N from 0 to 21.7 at%, and coercive forceI
H
c is the range of 43 to 5000e at room temperature. 相似文献
8.
Shinnosuke Miyauchi Yasuo Hattori Toshiyuki Takamatsu Yoshio Sorimachi 《应用聚合物科学杂志》1992,44(3):377-381
A method to generate a porous region near the surface of a polymer is suggested. In this method the region near the surface is swollen by immersing the polymer for a short time in a solvent. Subsequently, the polymer is introduced in a nonsolvent (for the polymer) that is, however, miscible with the solvent. The formation of the porous region is a result of (1) the swelling accompanied by the disentanglement of the surface molecular chains, and the dissolution of some of them during the immersion in the solvent, and (2) the rapid extraction of the solvent from the swollen region by the nonsolvent. The porous surface provides a matrix into which a second incompatible monomer can be polymerized so that the two otherwise incompatible polymers can adhere to one another. 相似文献
9.
Shigeki Habaue Momoko AsaiMasatake Morita Yoshio OkamotoHiroshi Uyama Shiro Kobayashi 《Polymer》2003,44(18):5195-5200
α-Methylenemacrolides having various groups, such as aromatic, ether, and amine, were enzymatically, anionically, and radically polymerized. The polymerization with the lipase catalyst successfully afforded polymers only through the ring-opening process, whereas the vinyl polymerizations selectively proceeded by using anionic and radical initiators. The polyesters obtained by the enzymatic polymerization have a polymerizable methacrylic methylene group in the main-chain, in addition to the aromatic and polar groups, and were further radically polymerized to quantitatively produce a cross-linked polymer gel. 相似文献
10.
Single-walled carbon nanotube networks grown on SiO2 pillars were studied by means of scanning photoemission microscopy. The individual nanotubes or nanotube bundles growing from the pillar tops were observed in C 1s images. Band bending near catalytic Fe/nanotube contacts in an end-bonded configuration was studied by measuring C 1s spectra along the tube axes. Within our experimental resolution, no band bending was observed. This implies that the depletion width is less than the spatial resolution of the scanning photoemission microscope (90 nm) or that the amount of the band bending is less than 0.1 eV. 相似文献