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排序方式: 共有590条查询结果,搜索用时 15 毫秒
1.
Yi Jin Chieko Toeda Takeo Kawaguchi Toshinobu Seki Kazuhiko Juni 《Drug development and industrial pharmacy》1996,22(7):653-658
Permeation of zidovudine (3'-azido-3'-deoxythymidine, AZT) and probenecid from oily bases containing an alcohol through rat skin was examined. Isopropyl myristate (IPM), as an oily vehicle, showed a penetration enhancing effect for AZT and probenecid. Ethanol, n-propanol, and n-butanol were used as additives in IPM and were examined for their own permeation and the enhancing effect on the permeation of AZT and probenecid. The skin permeation of AZT and probenecid from IPM was enhanced by addition of the alcohol in IPM. The degree of the enhancement was decreased with increasing lipophilicity of the alcohol used. me permeation rate of the drug from those systems was shown to be governed by penetration-enhancing effects of the oily base and alcohol, and the penetration of the alcohol itself through the skin. 相似文献
2.
Recent advances in semiconductor photonic functional devices based on the nonlinearities of laser diodes (LDs) are reviewed. Because the current research is driven primarily by the needs of optical fiber communications systems, most devices are made of InGaAsP and operate at wavelengths of between 1.3 and 1.55 μm, the wavelength window in which optical fibers have their most favorable properties. Minimum loss is at 1.55 μm, and zero dispersion is at 1.3 μm. AlGaAs devices operating at around 0.85 μm have also been reported. Two types of optical bistability-absorptive and dispersive-are explained, and devices based on them are described. Switching characteristics of bistable devices are discussed. Tunable wavelength converters and filters are also examined. Applications to all-optical communication and to optical switching systems are considered. Directions for future development are indicated 相似文献
3.
Cis-1,4-polybutadiene (PB) in a 0.5% solution of a solvent mixture of dichloromethane and 1,2-dibromoethane or tetrahydrofuran was quantitatively brominated with elemental bromine at 0°C under careful exclusion of oxygen to head-to-head poly(vinyl bromide). Partially brominated PB has a structure of random or block sequences of butadiene units in the polymer depending on the bromination solvent but shows no stereospecificity in the CHBrCHBr-dyads. Partially brominated PB with block structure showed a microphase-separated morphology over a wide range of composition. Microphase separation is less pronounced for the more random structure of butadiene units. I.r and 13C n.m.r. spectroscopy of the partially brominated PB was used to follow the progress of the bromination. 相似文献
4.
The crystalline structures of inclusion complexes of γ-cyclodextrin (γ-CD) with poly(ethylene glycol), poly(ethylene adipate), poly(propylene glycol) and poly(isobutylene) were studied by electron microscopy, in combination with X-ray diffraction works and measurements of thermal properties by DSC and TGA. The crystalline structure of as-prepared complexes was tetragonal and its cell dimensions were a = b = 2.380 nm and c = 1.48 nm. When an as-prepared sample was dried in a vacuum at room temperature, the tetragonal modification was transformed into the monoclinic one with the projected cell dimensions of a = 1.75, b = 1.36 nm and γ = 110°. The transformation occurred by progressive ‘shifting’ of rows of polymer necklaces in the [110] direction along the (110) plane in an original tetragonal lamellar crystal. Complexes lost weight by 10-15% in the process of heating up to 140 °C. The tetragonal crystalline modification was transformed into the hexagonal one, and concurrently, the X-ray diffraction profiles of annealed complexes were broadened. When a sample was dried in a vacuum at room temperature or annealed at high temperatures, followed by exposure to water vapor, the original tetragonal crystalline structure was recovered, restoring the original degree of orientation of crystallites in the sample. When water molecules were removed, the lateral stacking order of γ-CD-polymer complexes was destroyed, but the basic necklace structure in which polymer chains threaded through the cavity of γ-CD rings' structure could be retained. 相似文献
5.
Annadanam V. Sesha Sainath Takashi Inoue Yoshiharu Hatakeyama Masahiro Shishido Kenzo Okamoto Seigou Kawaguchi Takashi Kuriyama Kiyohito Koyama 《大分子材料与工程》2004,289(3):264-268
Summary: Polyacrylonitrile (PAN) particles with micro‐size ranges (0.15–2 μm) were prepared by emulsion and dispersion polymerizationa and in supercritical carbon dioxide media. The PAN particles were blended with Nylon 6 (PA6) at 220 °C by using a miniature mixer; it was found that melt‐mixing was possible for PAN‐rich compositions as high as 70 wt.‐%. Blends were characterized by scanning electron microscopy, IR, viscosity measurements, differential scanning calorimetry, and dynamic mechanical thermal analysis (DMTA). The size and shape of original PAN particles were retained in PAN/PA6 blends. The useful range to blend PAN particles size was less than 1 μm in terms of shape retention of the PAN particles in blends. Blends with 40 wt.‐% PAN content were found to be melt‐processable. The elastic modulus was higher for PAN/PA6 blends than pure PA6.
6.
Carbon materials are often used as catalyst supports, and for catalysts in electrodes of a polymer electrolyte fuel cell, carbon black has been used. Recently, it was found, however, that activated carbon could replace carbon black and besides, significantly improve the activity of the electrode catalyst layer for oxygen reduction. In the present study, to optimize the pore structure of activated carbon for further activity improvement, the influence of the pore structure on the activity was investigated using activated carbon of various specific surface areas and mean pore diameters. A catalyst layer was formed from activated carbon loaded with platinum and a polymer electrolyte. The activity of the layer was measured in an oxygen-saturated perchloric acid solution, supporting the layer on a rotating glassy carbon disk electrode. We found that increases in the specific surface area and mean pore diameter increased the activity and that the latter was more effective than the former mainly due to the enhanced mass-transfer in the pores; the catalyst layer formed from activated carbon with the largest mean pore diameter was the most active. Unless pores excessively develop and lose connections between particles, a large pore diameter is therefore desired for the fuel cell electrodes. 相似文献
7.
A data-driven design method for a cascade control system is proposed. The cascade control system consists of inner and outer loops, where the control interval of the outer loop is an integer multiple of the inner loop; hence, the system is a dual-rate system. In the proposed method, controllers in the inner and outer loops are designed based on one-shot data. In such a dual-rate cascade system, since the controllers are designed using different data-rate signals, the lifting technique is applied to align the dual-rate data. To show its effectiveness, the proposed method is compared with a conventional single-rate cascade control method, and numerical simulations and experiments are presented to examine servo and regulation performance. 相似文献
8.
9.
In order to non-destructively evaluate changes in toughness of cast duplex stainless steel, which is frequently used in main coolant pipes of PWR type nuclear power plants, due to thermal aging, we tried to apply thermoelectric power (TEP) measurement. because TEP is sensitive to microstructural material changes, and to clarify the mechanism behind TEP changes due to thermal aging. As a result, TEP of cast duplex stainless steel increased with aging time, and good correlations were found between TEP and toughness. Concerning the mechanism, TEP of high and low Cr content alloys was higher than that of intermediate Cr content alloys. Because high and low Cr areas are created in the ferrite phase due to thermal aging. TEP of the entire material increased. Furthermore, when each Cr fluctuating area acted in parallel, the increase in TEP became larger. According to the Mott-Jones theory, TEP is largely related to the electron density of states at the Fermi level. The electron density of states of Fe–Cr–Ni alloys in the valence band was measured with X-ray photoelectron spectroscopy (XPS). As a result, there was a high correlation between the TEP calculated from the XPS spectrum and the measured TEP. Therefore, we showed experimentally that the electron density of states changed due to variations in Cr concentration, which also affect TEP. 相似文献
10.
Tatsunari Ohkubo Takaaki Shiina Kayoko Kawaguchi Daisuke Sasaki Rena Inamasu Yue Yang Zhuoqi Li Keizaburo Taninaka Masaki Sakaguchi Shoko Fujimura Hiroshi Sekiguchi Masahiro Kuramochi Tatsuya Arai Sakae Tsuda Yuji C. Sasaki Kazuhiro Mio 《International journal of molecular sciences》2022,23(23)
Membrane proteins play important roles in biological functions, with accompanying allosteric structure changes. Understanding intramolecular dynamics helps elucidate catalytic mechanisms and develop new drugs. In contrast to the various technologies for structural analysis, methods for analyzing intramolecular dynamics are limited. Single-molecule measurements using optical microscopy have been widely used for kinetic analysis. Recently, improvements in detectors and image analysis technology have made it possible to use single-molecule determination methods using X-rays and electron beams, such as diffracted X-ray tracking (DXT), X-ray free electron laser (XFEL) imaging, and cryo-electron microscopy (cryo-EM). High-speed atomic force microscopy (HS-AFM) is a scanning probe microscope that can capture the structural dynamics of biomolecules in real time at the single-molecule level. Time-resolved techniques also facilitate an understanding of real-time intramolecular processes during chemical reactions. In this review, recent advances in membrane protein dynamics visualization techniques were presented. 相似文献