全文获取类型
收费全文 | 4944篇 |
免费 | 147篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 236篇 |
综合类 | 13篇 |
化学工业 | 1261篇 |
金属工艺 | 136篇 |
机械仪表 | 102篇 |
建筑科学 | 102篇 |
矿业工程 | 2篇 |
能源动力 | 207篇 |
轻工业 | 391篇 |
水利工程 | 7篇 |
石油天然气 | 4篇 |
无线电 | 480篇 |
一般工业技术 | 749篇 |
冶金工业 | 905篇 |
原子能技术 | 96篇 |
自动化技术 | 410篇 |
出版年
2023年 | 34篇 |
2022年 | 54篇 |
2021年 | 130篇 |
2020年 | 50篇 |
2019年 | 44篇 |
2018年 | 75篇 |
2017年 | 72篇 |
2016年 | 95篇 |
2015年 | 67篇 |
2014年 | 135篇 |
2013年 | 261篇 |
2012年 | 196篇 |
2011年 | 249篇 |
2010年 | 191篇 |
2009年 | 233篇 |
2008年 | 225篇 |
2007年 | 195篇 |
2006年 | 153篇 |
2005年 | 182篇 |
2004年 | 139篇 |
2003年 | 156篇 |
2002年 | 124篇 |
2001年 | 97篇 |
2000年 | 99篇 |
1999年 | 113篇 |
1998年 | 387篇 |
1997年 | 226篇 |
1996年 | 159篇 |
1995年 | 115篇 |
1994年 | 107篇 |
1993年 | 100篇 |
1992年 | 41篇 |
1991年 | 43篇 |
1990年 | 35篇 |
1989年 | 57篇 |
1988年 | 36篇 |
1987年 | 26篇 |
1986年 | 37篇 |
1985年 | 28篇 |
1984年 | 35篇 |
1983年 | 28篇 |
1982年 | 24篇 |
1981年 | 31篇 |
1980年 | 24篇 |
1979年 | 25篇 |
1978年 | 26篇 |
1977年 | 33篇 |
1976年 | 47篇 |
1974年 | 14篇 |
1973年 | 13篇 |
排序方式: 共有5101条查询结果,搜索用时 312 毫秒
91.
Electrocodeposition of Sm and Co on a Cu substrate was investigated in a molten LiCl-KCl-SmCl3 (0.5 mol.%)-CoCl2 (0.1 mol.%) system at 723 K. Phase of the deposited Sm-Co alloys could be controlled by electrolysis potential. SmCo3 was formed on a Cu substrate by potentiostatic electrolysis in the potential range of 0.20-0.90 V (vs. Li+/Li). Sm2Co17 was obtained in the potential range of 0.90-1.50 V. 相似文献
92.
Koichiro Fukuda Iwao Maki Suketoshi Ito 《Journal of the American Ceramic Society》1997,80(6):1595-1598
Crystals of β-Ca2 SiO4 (space group P 121 / n 1) were examined by high-temperature powder X-ray diffractometry to determine the change in unit-cell dimensions with temperature up to 645°C. The temperature dependence of the principal expansion coefficients (αi ) found from the matrix algebra analysis was as follows: α1 = 20.492 × 10−6 + 16.490 × 10−9 ( T - 25)°C−1 , α2 = 7.494 × 10−6 + 5.168 × 10−9 ( T - 25)°C−1 , α3 =−0.842 × 10−6 − 1.497 × 10−9 ( T - 25)°C−1 . The expansion coefficient α1 , nearly along [302] was approximately 3 times α2 along the b -axis. Very small contraction (α3 ) occurred nearly along [ 01]. The volume changes upon martensitic transformations of β↔αL ' were very small, and the strain accommodation would be almost complete. This is consistent with the thermoelasticity. 相似文献
93.
Monooctadecyl maleate, as a polymerizable surfactant, was synthesized by the mono-esterification of maleic anhydride and octadecanol,
and was utilized to surface-modify nano-Fe3O4 particles. A polymerizable magnetic fluid was obtained by directly dispersing modified nano-Fe3O4 particles into styrene monomer, and the polystyrene/nano-Fe3O4 composite was prepared through free radical polymerization of polymerizable magnetic fluid. The structure and dispersion
status in different dispersion phases of modified nano-Fe3O4 particles were studied by Fourier transform infrared (FTIR) spectrometry, X-ray diffraction (XRD) and transmission electron
microscopy (TEM), respectively. The experimental results show that the nano-Fe3O4 particles modified by monooctadecyl maleate with the size of about 7–10 nm can be uniformly dispersed into styrene and fixed
in the composite during the procedure of polymerization. Thermogravimetric analysis (TGA) and vibrating sample magnetometry
(VSM) indicate that the thermal stability of polystyrene/nano-Fe3O4 composite is improved compared to that of pure polystyrene, and the composite is a sort of superparamagnetic materials. 相似文献
94.
Atsushi Tanaka 《Carbon》2004,42(3):591-597
The present study confirmed that highly crystalline nanofibers with controlled structure may be prepared over Fe and Fe-Ni alloy catalysts. The degree of graphitization of various carbon nanofibers (CNFs) was analyzed by using C(0 0 2) peaks from the XRD profiles. The C(0 0 2) peaks of CNFs over Fe catalyst shifted to higher angle and became narrower as the preparation temperature increased from 560 to 620 °C. Tubular CNFs prepared at temperature higher than 630 °C showed lower 2θ angles compared to those of platelet fibers. CNFs prepared over Fe-Ni catalysts tended to resemble those prepared over Fe catalysts. The degree of graphitization of platelet CNFs resembled natural graphite, while d0 0 2 of the tubular CNFs showed values below the 3.39 Å reported as a theoretical minimum for a cylindrical alignment. Lc0 0 2 of platelet and tubular CNFs increased by heat treatment at 2000 and 2800 °C though d0 0 2 changed little. A transverse section of platelet and tubular CNFs had a hexagonal shape, not a round shape. The hexagonal column allows AB stacking of hexagonal planes that can give perfect hexagonal alignment. 相似文献
95.
Masanori Hirano Keisuke Ota Takaharu Ito 《Journal of the American Ceramic Society》2005,88(12):3303-3310
Anatase-type TiO2 powder containing sulfur with absorption in the visible region was directly formed as particles with crystallite in the range 15–88 nm by thermal hydrolysis of titanium(III) sulfate (Ti2 (SO4 )3 ) solution at 100°–240°C. Because of the presence of ammonium peroxodisulfate ((NH4 )2 S2 O8 ), the yield of anatase-type TiO2 from Ti2 (SO4 )3 solution was accelerated, and anatase with fine crystallite was formed. Anatase-type TiO2 doped with ZrO2 up to 9.8 mol% was directly precipitated as nanometer-sized particles from the acidic precursor solutions of Ti2 (SO4 )3 and zirconium sulfate in the presence and the absence of (NH4 )2 S2 O8 by simultaneous hydrolysis under hydrothermal conditions at 200°C. By doping ZrO2 into TiO2 and with increasing ZrO2 content, the crystallite size of anatase was decreased, and the anatase-to-rutile phase transformation was retarded as much as 200°C. The anatase-type structure of ZrO2 -doped TiO2 was maintained after heating at 1000°C for 1 h. The favorable effect of doping ZrO2 to anatase-type TiO2 on the photocatalytic activity was observed. 相似文献
96.
97.
Hydrogen entry and permeation into iron were measured by an electrochemical method during atmospheric corrosion reaction. The hydrogen permeation was enhanced on passive films because the hydrogen adsorption increased by the hydrogen evolution mechanism which is different from that on a bear iron surface. The permeation rate during a wet and dry corrosion cycle showed a maximum in the drying process depending upon the surface pH and the corrosion potential. The pollutant such as Na2SO3 which decreases the pH and the corrosion potential causes an increase in the permeation rate. The mechanism of the change in the permeation rate during the wet and dry cycles is explained by the polarization diagram of the electrode covered by thin water layer. 相似文献
98.
S. Nakashima Y. Ikeda S. Hirose H. Nakamura T. Ito 《Journal of Materials Engineering and Performance》1992,1(2):211-218
Kawasaki Steel Corporation and Kawatetsu Mining Co., Ltd. have developed a new refining process to extract iron oxide from
iron ore to meet the increase in demand for iron oxide for high- grade hard ferrites. This article discusses the quality of
iron oxides and the characteristics of the hard ferrite magnets produced from them. 相似文献
99.
Thin DLC films coated on polymer surfaces are attracting considerable attention due to their wide applications and their interesting surface properties. When DLC films were coated on polymers, the resulting DLC-polymer composites are highly functionalized materials, some of which presenting dramatically improved gas barrier properties.In this paper, we will introduce several commonly used polymers including polyethylene terephthalate (PET), polyethylene (PE) and polypropylene (PP) for semi-crystalline polymers, and polymethyl methacyrlate (PMMA) for an amorphous polymer. The polymers were coated with thin DLC films and the gas barrier properties of the resulting DLC-polymer composites were investigated. Some of the DLC-polymer composites dramatically improved their gas barrier properties while they presented horizontal crack lines and vertical micro-buckling lines on the DLC surface when stretched to a certain strain. The gas barrier properties of the DLC-polymer composites with fractured DLC surface were also studied. It was found that the gas barrier property of the polymer substrates with lower residual strains was less damaged, when the substrates were mechanically deformed, than that of the polymer substrates with higher residual strains. When the number of the cracks increases, the strain imposed on each crack decreases, since the overall deformation is almost equally distributed to each crack while the crack spacing of each crack becomes shorter. Thus, it was found that the degradation of the gas barrier property after mechanical deformation is dependent on the residual strain of the polymers and the number of cracks on DLC films. 相似文献
100.
General interest for robotic technology has been increased by the public and the media after Fukushima Daiichi Nuclear Power Plant (hereafter referred to as 1F) disaster. Especially, robots which can work under the very severe condition where personnel cannot access have demands for development. As to respond to such high demands, NEDO established ‘Disaster response unmanned systems development project’ in 2012.[1] This project is specialized in the development of various remote-controlled equipment, such as remote-controlled platform truck and remote control human interface under ‘Mobile Robot Development’. Remote-controlled platform truck is designed to safely and surely deliver robots and supplies, instead of using stairs and elevator, etc. in and out of building where it is too critical for personnel to work under. Remote control human interface for robots is designed to standardize the command and operation screen for operator, based on opinions from project members, and manned facility construction.[2] In this article, mechanical structure and development tasks for remote-controlled platform truck, and commonalization approach for operation and camera display of various remote-controlled equipment and robot for remote control human interface are stated. Background: due to hydrogen explosion triggered by The Great East Japan Earthquake on 11 March 2011, a reactor building at Fukushima Daiichi Nuclear Power Plant was severely damaged. It is required to reduce high radiation dose in the atmosphere of the reactor building to perform restoration. To pursue decontamination of the reactor building, equipment to lift and carry decontamination devices to upper floor are required. 相似文献