全文获取类型
收费全文 | 21738篇 |
免费 | 1252篇 |
国内免费 | 762篇 |
专业分类
电工技术 | 248篇 |
技术理论 | 1篇 |
综合类 | 892篇 |
化学工业 | 5693篇 |
金属工艺 | 1381篇 |
机械仪表 | 481篇 |
建筑科学 | 693篇 |
矿业工程 | 418篇 |
能源动力 | 1088篇 |
轻工业 | 4267篇 |
水利工程 | 202篇 |
石油天然气 | 1021篇 |
武器工业 | 203篇 |
无线电 | 774篇 |
一般工业技术 | 3485篇 |
冶金工业 | 1046篇 |
原子能技术 | 207篇 |
自动化技术 | 1652篇 |
出版年
2024年 | 67篇 |
2023年 | 291篇 |
2022年 | 453篇 |
2021年 | 546篇 |
2020年 | 567篇 |
2019年 | 596篇 |
2018年 | 529篇 |
2017年 | 608篇 |
2016年 | 539篇 |
2015年 | 570篇 |
2014年 | 1073篇 |
2013年 | 1247篇 |
2012年 | 1263篇 |
2011年 | 1948篇 |
2010年 | 1350篇 |
2009年 | 1388篇 |
2008年 | 1202篇 |
2007年 | 1354篇 |
2006年 | 1158篇 |
2005年 | 1011篇 |
2004年 | 880篇 |
2003年 | 749篇 |
2002年 | 672篇 |
2001年 | 492篇 |
2000年 | 492篇 |
1999年 | 411篇 |
1998年 | 342篇 |
1997年 | 319篇 |
1996年 | 296篇 |
1995年 | 266篇 |
1994年 | 221篇 |
1993年 | 161篇 |
1992年 | 136篇 |
1991年 | 107篇 |
1990年 | 82篇 |
1989年 | 68篇 |
1988年 | 61篇 |
1987年 | 40篇 |
1986年 | 35篇 |
1985年 | 31篇 |
1984年 | 27篇 |
1983年 | 21篇 |
1982年 | 20篇 |
1981年 | 19篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1975年 | 3篇 |
1961年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Thin layers of ceria were deposited on the surface of mica platelets in solution. The reaction of such particles with hydrogen sulfide yields a red colored special effect pigment. The ceria layer reacts with H2S to produce a variety of sulfide and oxysulfide phases. The reaction path discovered in situ by time and temperature resolved X-ray diffraction is CeO2→CeS2→C-Ce2S3→Ce10S14O. The reaction itself is extremely variable depending on gas flow, heating rates and decomposition atmospheres. Effects on the thin film are recorded by scanning electron microscopy (SEM) and revealed a destruction of the layer once red Ce10S14O was formed. The product layer then reveals the typical nonwetting behaviour of a liquid on a surface. 相似文献
52.
K Madhusudan Reddy Sunkara V Manorama R.D.K Misra 《Materials Research Bulletin》2004,39(10):1491-1498
A comparative study of gas sensing behavior of nanocrystalline nickel ferrite synthesized by micro-emulsion and hydrothermal method to liquefied petroleum gas (LPG) is presented. Nanocrystalline nickel ferrite synthesized by hydrothermal method indicated higher electrical conductivity and gas sensitivity at low operating temperature compared to nanocrystalline nickel ferrite synthesized by reverse micelle technique. This difference in the gas sensing behavior can be attributed to the presence of more oxygen vacancies (i.e. non-stoichiometry) in the hydrothermally synthesized nickel ferrite. Incorporation of palladium had a catalytic effect and the operating temperature was significantly reduced in both the samples. The higher operating temperature of the reverse micelle nickel ferrite material makes the sensor response speed faster (∼10 s) compared to the hydrothermally synthesized material (∼1 min). 相似文献
53.
The thick film of Zn-Sb-O was prepared by coating the paste of nanoparticles mixture (Sb2O3:ZnO=1:3) on the alumina substrate, followed by sintering at 500-900 °C for 2 h in air. The electrical resistance and gas-sensing properties to benzene, alcohol and acetone of Zn-Sb-O films were found to be dependent on the change of phase structure caused by sintering temperature. 相似文献
54.
Mubasher A. Bashir 《Polymer》2005,46(10):3223-3229
Gradient chromatography was applied in order to calculate the composition at elution for different methacrylates on normal phase columns. In addition the composition at elution was determined for polyethyleneoxide on a reverse phase column. It is shown that high molar mass polymers elute for a given homopolymer irrespective of their molar mass at the same eluent composition, which varies only slightly with gradient slope. In general the composition at elution in gradient chromatography is expected to be slightly lower than the true critical composition. For high molar mass polymers we found this composition to be close to the critical composition determined by isocratic experiments. The difference between the composition at elution and the true critical composition for a variety of polymethacrylates and for polyethyleneglycol was found to be only between 0.2 and 5%. Thus, after estimating the composition at elution, only a small number of additional isocratic experiments is needed to find the exact critical composition. 相似文献
55.
M. Guerioune Y. Amiour W. Bounour O. Guellati A. Benaldjia A. Amara N. E. Chakri M. Ali-Rachedi D. Vrel 《International Journal of Self-Propagating High-Temperature Synthesis》2008,17(1):41-48
Aiming at preparation of shape memory alloys (SMAs), we explored the SHS of Cu1 − x
Zn1 − y
Al1 − z
alloys (0.29 < x < 0.30, 0.74 < y < 0.75, and 0.83 < z < 0.96). The most pronounced shape memory effect was exhibited by the alloys of the following compositions (wt %): (1) Cu(70.6)Zn(25.4)Al(4.0),
(2) Cu(70.1)Zn(25.9)Al(4.0), and (3) Cu(69.9)Zn(26.1)Al(4.0). The effect of process parameters on the synthesis of CuZnAl
alloys was studied by XRD, optical microscopy, and scanning electron microscopy (SEM). The grain size of CuZnAl was found
to depend on the relative amount of the primary CuZn and AlZn phases. Changes in the transformation temperature and heat of
transformation are discussed in terms of ignition intensity and compaction. Mechanism of the process depends on the level
of the temperature attained relative to the melting point of components. At the melting point of AlZn, the process is controlled
by the solid-state diffusion of AlZn into a product layer. The ignition temperature for this system depends on the temperature
of the austenite-martensite transformation in CuZnAl alloys. The composition and structure of the products was found to markedly
depend on process parameters. The SHS technique has been successfully used to prepare a variety of SMAs.
相似文献
56.
57.
58.
Porous carbon nanofibers are synthesized by CVD method from acetylene with use of iron-containing catalysts. Activation of the nanofibers in melted potassium hydroxide results in increasing surface area from initial 300–400 m2 g−1 to 1700 m2 g−1. As follows from XRD data, activated nanofibers do not contain regular packages of graphene layers, but retain high electric conductivity. Deposition of copper improves electrochemical hydrogen storing characteristics of carbon nanofibers. Carbon nanomaterials obtained can be used as hydrogen storing materials in batteries instead of hydride forming metals. 相似文献
59.
60.
CHENG Xiang 《半导体光子学与技术》2004,(4)
Amorphous carbon (a-C) films and amorphous carbon films incorporating with the nitrogen (a-C∶N) were deposited on silicon substrates in a radio-frequency driven plasma enhanced chemical vapour deposition system, while the surface electrical properties of films were investigated by electrochemical capacitance-voltage measurements. It was examined the effect of the interface defects on the properties and deduced that the conducting type of a-C∶N films was n-type. Subsequently, a comparative studies of a-C and a-C∶N films were performed by photoluminescence spectra depending on the temperature. With the decrease of the temperature, the main band with peak energy of 2.48 eV in the a-C∶N films was more intense compared with the other three bands caused by amorphous C in the a-C films. 相似文献