全文获取类型
收费全文 | 1651篇 |
免费 | 45篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 113篇 |
综合类 | 2篇 |
化学工业 | 544篇 |
金属工艺 | 59篇 |
机械仪表 | 58篇 |
建筑科学 | 49篇 |
矿业工程 | 1篇 |
能源动力 | 109篇 |
轻工业 | 119篇 |
水利工程 | 11篇 |
石油天然气 | 4篇 |
无线电 | 73篇 |
一般工业技术 | 303篇 |
冶金工业 | 41篇 |
原子能技术 | 45篇 |
自动化技术 | 178篇 |
出版年
2023年 | 7篇 |
2022年 | 33篇 |
2021年 | 44篇 |
2020年 | 22篇 |
2019年 | 23篇 |
2018年 | 35篇 |
2017年 | 22篇 |
2016年 | 29篇 |
2015年 | 16篇 |
2014年 | 32篇 |
2013年 | 85篇 |
2012年 | 63篇 |
2011年 | 121篇 |
2010年 | 69篇 |
2009年 | 78篇 |
2008年 | 86篇 |
2007年 | 66篇 |
2006年 | 61篇 |
2005年 | 65篇 |
2004年 | 54篇 |
2003年 | 54篇 |
2002年 | 45篇 |
2001年 | 36篇 |
2000年 | 27篇 |
1999年 | 32篇 |
1998年 | 46篇 |
1997年 | 43篇 |
1996年 | 25篇 |
1995年 | 25篇 |
1994年 | 43篇 |
1993年 | 26篇 |
1992年 | 22篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 19篇 |
1986年 | 26篇 |
1985年 | 21篇 |
1984年 | 14篇 |
1983年 | 20篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 16篇 |
1979年 | 19篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有1709条查询结果,搜索用时 15 毫秒
131.
The crystallization mechanism of high-cordierite (2MgO·2Al2O3·5SiO2) from a bulkglass containing B2O3 and P2O5 as nucleating agents was studied using X-ray diffraction, differential thermal analysis and a polarizing microscope. Thin glass specimens, with a mirror surface, were heated rapidly in an electric furnace in the temperature range 888 to 1363° C for a desired time and then rapidly quenched to room temperature. The normal rate of growth of precipitated cordierite crystals was measured and their morphological change was observed photographically. The growth rate increased with temperature, and the maximum rate occurred at about 1250° C. The crystal morphology was hexagonalprismatic, elongated along thec-axis. Faceted interface morphology was observed when the range of undercooling was from 7 to 174° C. Judging from the relationship between the reduced growth rate and the degree of undercooling, the crystallization mechanism in the range of lower undercooling was governed by a layer growth depending on the surface nucleation mechanism. In the range of higher undercooling, continuous growth was seen and at intermediate undercooling a transition range from a layer growth to a continuous growth was evident. 相似文献
132.
Hiroaki Yonemura Koichi Yuno Yuuichi Yamamoto Sunao Yamada Yoshihisa Fujiwara Yoshifumi Tanimoto 《Synthetic Metals》2009,159(9-10):955-960
Nanowires consisting of regioregular poly(3-hexylthiophene) (P3HT) as a conducting polymer were prepared using p-xylene. Magnetic processing of the nanowires was carried out using two superconducting magnets with horizontal (Bmax = 8 T) and vertical (Bmax = 10 T) directions. The formation of the nanowires was confirmed by atomic force microscopy (AFM) measurement. The results from the AFM images and the polarized absorption spectra on glass plates indicated that the nanowires partly oriented themselves with their long axes, which are parallel to the π–π stacking direction, being perpendicular to the magnetic field. The magnetic orientation is most likely ascribed to anisotropy in the magnetic susceptibilities of the ordered P3HT in the nanowires. 相似文献
133.
A facile approach to the fabrication of ultrathin polymer films on a flat or curved substrate is presented. Polymers with unsaturated pendant groups were spin-coated on a photoinitiator tethered surface, which was then photoirradiated and washed with a solvent. The obtained films were uniform, smooth (Ra < 0.2 nm) and exhibited robustness toward solvents. The thickness of the films was determined by the molecular weight of the coated polymer and was not dependent on the initial spin-coated thickness. A mechanism for the formation of the ultrathin film and application to optical lenses is presented. 相似文献
134.
A pure culture of Microcystis aeruginosa or Anabaena variabilis, the representatives of water blooming algae, was exposed to low-pressure (LP) or medium-pressure (MP) UV lamps. Irradiated pure culture suspension was subsequently incubated for 7d under white light fluorescent lamps. During incubation, profiles of the number of cells, DNA damage and photosynthetic activity were determined. When UV fluence was 600mJ/cm(2), M. aeruginosa cell numbers decreased throughout the 7-d incubation period, to produce 1.5log reduction (LP) or 1.2log reduction (MP) compared with control. The amount of DNA damage was 2.02x10(-4) ESS/base (LP) and 3.42x10(-4) ESS/base (MP) just after UV irradiation, which became 0.05x10(-4) ESS/base and 0.23x10(-4) ESS/base, respectively, after 3d incubation. However, cell number kept decreasing, even after DNA repair. Photosynthetic activity decreased by 1.5log within 1d (LP) or 3d (MP). Thus, reduction in photosynthetic activity could contribute to the reduction in M. aeruginosa cell numbers. A. variabilis cell numbers reduced by 2.3log (LP) or 2.2log (MP) during the 7-d incubation period; however, after DNA damage repair, cell number began to increase. The amount of DNA damage was 6.07x10(-4) ESS/base (LP) and 4.48x10(-4) ESS/base (MP) just after UV irradiation, which became 0.23x10(-4) ESS/base and 0.40x10(-4) ESS/base, respectively, after 3d incubation. No reduction was observed in photosynthetic activity/cell. Therefore, DNA damage is the main contributor of the reduction in cell number of A. variabilis. 相似文献
135.
Shimizu M Miyashita K Kitagaki H Ito K Shimoi H 《Journal of Bioscience and Bioengineering》2005,100(6):678-680
Sake yeasts are used for sake brewing and have a crucial role in the quality of sake, since they produce not only ethanol but also various compounds that provide sake flavors. Therefore, the appropriate selection and monitoring of a strain used in sake mash is important. However, the identification of specific sake yeast strains has been difficult, because sake yeasts have similar characteristics in taxonomic and physiological analyses. We found amplified fragment length polymorphisms (AFLPs) in the PCR products of the AWA1 gene of sake yeast strains. The AWA1 gene encodes a cell wall protein that is responsible for foam formation in sake mash. This polymorphism of the AWA1 gene can be used for the identification of sake yeast strains. 相似文献
136.
Atsushi Takada Yu-Ichi Komizo Hidenori Terasaki Tomoyuki Yokota Kenji Oi Koichi Yasuda 《Welding International》2013,27(4):254-261
Inclusions contributing to acicular ferrite nucleation were investigated from a crystallographic point of view in low carbon low alloy steelweld metals. The samples from electro slag welding (ESW) and submerged arc welding (SAW) deposits with various cooling rates were prepared in this study. In those samples, intragranular acicular ferrite formation was observed from inclusions. The inclusions contributing to acicular ferrite formation were of multi-phase type consisting of amorphous phase, spinel type and MnS. They were surrounded by a Ti-enriched layer. It was confirmed by selected area diffraction patterns and energy-dispersive X-ray spectrometer analyses that the Ti-enriched layer was TiO. The acicular ferrite had a Baker–Nutting orientation relationship with the TiO layer on the inclusion surface. The misfit was 3.0% at the interface between the acicular ferrite and TiO. Therefore, it is considered that TiO on the inclusion surface contributes to the heterogeneous nucleation of acicular ferrite by small lattice misfit. However, themorphologies of ferrite growth which nucleated from inclusions were different in both samples. Whereas the growth of ferrites nucleated from TiO was enough in ESW, the size of nucleated ferrite in SAW was a few hundred millimetres in size. In the early stage of nucleation from TiO, ferrite had small deviation from Kurdjumov–Sachs orientation relationship (K–S relationship) in both ESW and SAW. However, there was a difference in the growth stage of ferrite. The ferrite orientations were gradually changed to fit to the K–S relationship in ESW. On the other hand, the nucleated ferrite in SAW stopped growing and the newly nucleated ferrite which had K–S relationship prior to austenite was formed adjacently because of large super cooling due to small heat input. 相似文献
137.
Koichi Kobayashi Jun-ichi Imura Kunihiko Hiraishi 《Discrete Event Dynamic Systems》2011,21(4):519-545
This paper discusses the state feedback stabilization problem of a deterministic finite automaton (DFA), and its application
to stabilizing model predictive control (MPC) of hybrid systems. In the modeling of a DFA, a linear state equation representation
recently proposed by the authors is used. First, this representation is briefly explained. Next, after the notion of equilibrium
points and stabilizability of the DFA are defined, a necessary and sufficient condition for the DFA to be stabilizable is
derived. Then a characterization of all stabilizing state feedback controllers is presented. Third, a simple example is given
to show how to follow the proposed procedure. Finally, control Lyapunov functions for hybrid systems are introduced based
on the above results, and the MPC law is proposed. The effectiveness of this method is shown by a numerical example. 相似文献
138.
Transmission experiments for a local area network (LAN) using blue‐light‐emitting diodes (LEDs) with InGaN/GaN multiple quantum well (MQW) and plastic optical fibers (POFs) have been conducted. Audio analog signals have been transmitted up to 1800 kHz, which corresponds to an optical 1.5 dB bandwidth of LED response. The response speed of these diodes has been investigated by varying the operating conditions: dc bias, pulse amplitude, and pulse shape. The LED rise time is reduced from 0.26 μs to 0.19 μs by changing the electrical pulse amplitude from 0.5 V to 1.2 V, whereas the fall time (0.20 μs) does not change. On the other hand, the fall time is reduced from 0.20 μs to 0.14 μs by adding negative pulses after the applied positive pulses. It is shown that the direct‐modulation speed of these diodes is limited by the time constant associated with device capacitance. Electroluminescence and photocurrent spectra of the LEDs were also investigated; blueshifts were observed for both peaks in the spectra. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 47–51, 2001 相似文献
139.
Zirconium and hafnium oxide interface with silicon: Computational study of stress and strain effects
Computations of the periodic double-interface MO2/Si (M = Zr and Hf) systems using density functional theory (DFT) demonstrate that very thin epitaxial MO2 layers at silicon (1 0 0) surface adopt anatase-like structure with six-coordinate M atoms, while tetragonal-like MO2 structure with seven-coordinated M atoms has a lower stability (metastable). This results from a closer match between Si(1 0 0) surface unit cell and anatase-like ZrO2 and HfO2 leading to the overall stress reduction if MO2 adopts the anatase-like structure on silicon. In agreement with the previous study of Gavartin et al. [Gavartin, Fonseca, Bersuker, Shluger, Microelectron. Eng. 80 (2005) 412–415] formation of oxygen vacancy at the interface is demonstrated to be lower than in bulk film. This result appears to be independent from the film or interface structure but originates from the energy balance between M–O, M–M, Si–O and M–Si bonds, as revealed by a simple molecular model. 相似文献
140.
Naoki Yashiro Tomohiro Usui Koichi Kikuta 《Journal of the European Ceramic Society》2010,30(10):2093-2098
The application of an inkjet printing process for fabricating solid oxide fuel cell (SOFC) cathodes was investigated. Stably-dispersed LSCF–GDC inks were prepared by ball milling, and the composition was easily controlled by the preparation process. Fabrication of an LSCF–GDC layer was successfully carried out by depositing dots and the thickness was easily controlled by repeating printing process. A planar SOFC single cell with a double-layered cathode (comprised of a paste painted cathode layer and an inkjet printed interlayer) achieved a maximum power density of 0.71 W/cm2 at 600 °C. This is the preliminary work for fabricating the cathode layer of a SOFC single cell via inkjet printing. 相似文献