全文获取类型
收费全文 | 45106篇 |
免费 | 883篇 |
国内免费 | 873篇 |
专业分类
电工技术 | 912篇 |
综合类 | 215篇 |
化学工业 | 7013篇 |
金属工艺 | 3181篇 |
机械仪表 | 1510篇 |
建筑科学 | 1005篇 |
矿业工程 | 245篇 |
能源动力 | 1523篇 |
轻工业 | 2424篇 |
水利工程 | 392篇 |
石油天然气 | 1448篇 |
武器工业 | 7篇 |
无线电 | 4404篇 |
一般工业技术 | 11146篇 |
冶金工业 | 7443篇 |
原子能技术 | 822篇 |
自动化技术 | 3172篇 |
出版年
2021年 | 419篇 |
2020年 | 335篇 |
2019年 | 417篇 |
2018年 | 732篇 |
2017年 | 726篇 |
2016年 | 842篇 |
2015年 | 649篇 |
2014年 | 948篇 |
2013年 | 2582篇 |
2012年 | 1580篇 |
2011年 | 2083篇 |
2010年 | 1675篇 |
2009年 | 1936篇 |
2008年 | 1811篇 |
2007年 | 1914篇 |
2006年 | 1571篇 |
2005年 | 1345篇 |
2004年 | 1275篇 |
2003年 | 1187篇 |
2002年 | 1199篇 |
2001年 | 1226篇 |
2000年 | 1035篇 |
1999年 | 1075篇 |
1998年 | 2184篇 |
1997年 | 1726篇 |
1996年 | 1488篇 |
1995年 | 1029篇 |
1994年 | 788篇 |
1993年 | 798篇 |
1992年 | 620篇 |
1991年 | 605篇 |
1990年 | 536篇 |
1989年 | 497篇 |
1988年 | 382篇 |
1987年 | 408篇 |
1986年 | 373篇 |
1985年 | 384篇 |
1984年 | 314篇 |
1983年 | 312篇 |
1982年 | 310篇 |
1981年 | 304篇 |
1980年 | 354篇 |
1979年 | 348篇 |
1978年 | 296篇 |
1977年 | 418篇 |
1976年 | 641篇 |
1975年 | 313篇 |
1974年 | 295篇 |
1973年 | 312篇 |
1972年 | 273篇 |
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
971.
Predominantly single phase Fe base alloy films were prepared by a DC sputtering method. The compositions of the alloy films, as determined by Auger electron spectroscopy (AES) were Fe-7 at% Cr and Fe-18 at% Cr, Fe-11 at% W and Fe-19 at% W, Fe-9, −13 and −27 at% Ta. The pitting potential of the sputtered alloys determined in chloride solutions was found to be strongly dependent on the nature and the concentration of the alloying element. The pitting potential of sputtered Fe-18 at% Cr and Fe-27 at% Ta alloy films were approximately 0.9 V higher than that of bulk Fe and 0.6 V higher than that of Fe-19 at% W alloy film. A very good correlation was found between the pitting potential of Fe alloy films and the solubility of an alloying element oxide in acidic solutions with a pH corresponding to that within the stable pits of pure Fe (pH = 2). The pitting potential of the Fe alloy was found to increase with a decrease in the solubility of the alloying element oxide in acidic solutions. The pitting potentials of the sputtered Fe-7 at% Cr and Fe-18 at% Cr alloy films were were significantly higher than those of the bulk materials with the same composition. The higher pitting potentials of these alloy films are tentatively attributed to the presence of very fine particles of the oxide phase that are homogeneously distributed in the sputtered alloys. 相似文献
972.
S. Q. Fan G. J. Yang C. J. Li G. J. Liu C. X. Li L. Z. Zhang 《Journal of Thermal Spray Technology》2006,15(4):513-517
Control of the microstructure of TiO2 coatings through preparation methods significantly influences the coating performance. In this study, a vacuum cold-spray
process, as a new coating technology, is used to deposit nanocrystalline TiO2 coatings on conducting glass and stainless steel substrates. TiO2 deposits were formed using two types of nanocrystalline TiO2 powders with mean particle diameters of 200 and 25 nm. Coating microstructures were characterized by scanning electron microscopy
and x-ray diffraction analysis. Results demonstrate that a thick nanocrystalline TiO2 coating can be deposited by the vacuum cold-spray process. The coating was found to consist of particles stacked as agglomerates
that build up to several hundred nanometers. The coating also presents a mesoporous microstructure that could be effective
in such applications as photocatalytic degradation and dye-sensitized solar cells.
This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials
Park, OH, 2006. 相似文献
973.
974.
This communication reports into the effects of flow, fluid composition and the effectiveness of imidazoline inhibitors on the evolution and distribution of corrosion products on 1018 C-steel exposed to CO2 corrosion. Focused ion beam technique was used to measure the thickness of the corrosion product layer (CPL), in contrast to the conventional techniques used to observe the cross-section of specimens. Morphological analysis using scanning electron microscopy revealed topographical variations on the surface with the change in the multiphase environment. The CPL was found to be more porous in nature with the presence of oil in the multiphase environment. Electrochemical impedance spectroscopy was also used in the present study to measure the corrosion rates and was subsequently correlated to the CPL evolution for 1018 C-steel in multiphase environment. 相似文献
975.
M.A. Dar S.G. Ansari Z.A. Ansari Hironobu Umemoto Young-Soon Kim Hyung-Kee Seo Gil-Sung Kim Eun-Kyung Suh Hyung-Shik Shin 《International Journal of Refractory Metals and Hard Materials》2006,24(6):418-426
Diamond thin films have been deposited using hot filament chemical vapour deposition technique on manually scratched p-Si(1 0 0) substrate, with and without magnesium interlayer. In spite of magnesium melting point being lower (Tm = 649 °C) than the growth temperature of the substrate (Ts 750 °C) used in these experiments, it was found that high quality diamond films could be grown on Mg covered substrate. A liquid substrate is probably generated during the diamond film growth. Raman spectroscopy analysis exhibited only the triply degenerate, zone centre optical phonon peak at 1333 cm−1 indicating that nearly stress free crystallites were present. Broadening of the Raman peak (11.76 cm−1) indicates that some small crystallites also are present. Scanning electron and atomic force microscopy accompanied by X-ray diffraction analysis where used to compare the details of diamond film growth directly on scratched Si(1 0 0) and Mg interlayered scratched Si(1 0 0) substrates. 相似文献
976.
Application of electromagnetic-assisted stamping (EMAS) technique in incremental sheet metal forming 总被引:1,自引:0,他引:1
C.N. Okoye J.H. Jiang Z.D. Hu 《International Journal of Machine Tools and Manufacture》2006,46(11):1248-1252
The application of high velocity electromagnetic-assisted stamping (EMAS) technique in incremental sheet metal forming has been proposed. EMAS whose principle is based on Lorenz force is a hybrid forming process that uses both quasi-static conventional stamping technique and electromagnetic forming actuators built into sharp corners and other difficult-to-form contours to form metals. The recent push to use more artificial intelligent (AI) aluminum alloys in automobile and aircraft industries as a result of increasing demand for fuel efficient cars and aircrafts, large size vehicle panels, improved formability limit of materials and weight reduction have placed EMAS as one of the best high velocity forming technique.It is believed that the end result of this vision will lead to more cost effective land and aerospace vehicles. 相似文献
977.
Z. Serhal P. Berot J. Morvan M. Rezrazi J. Pagetti 《Surface & coatings technology》2002,150(2-3):290-296
Energy dispersive spectrometry (EDS) and infrared reflection absorption spectroscopy (IRRAS) have been previously used for the qualitative and quantitative analysis of PTFE in gold–PTFE composite coatings. The inclusion rate of PTFE particles in the composite coating is determined close to the surface by these two methods and particularly within a thickness of 0.5 μm by EDS. Differential scanning calorimetry (DSC) is investigated for a direct determination of the inclusion rate of PTFE, independently of the depth in the coating. The gold matrix allows us to release from metal oxidation and, associated with PTFE (chemically inert), to isolate easily the composite coating by dissolution of the metal support. Correlation is made between the DSC and EDS methods previously proposed as detection tools. 相似文献
978.
979.
Z. Huda 《Journal of Materials Engineering and Performance》1995,4(1):48-53
Recent advancements in turbine-blade materials engineering are reviewed in light of general superalloy research and the author’s
work on a new powder metallurgy IN-792 creep-limited alloy for application in blades of gas-turbine engines. The developed
set of principles presented in this paper incorporates all the factors that must be taken into consideration in selecting
and designing an alloy for turbine blades. 相似文献
980.
Banding formation and eutectic lamellar growth in a directionally solidified Ni50Al20Fe30 alloy were investigated. It was found that the banding area consists of two layers. The first layer is a γ layer, while the
subsequent one is a γ layer. The composition of various phases around the banding area changes with the solidification process.
The banding is formed by two steps process and caused by factors such as the fractions during the sample growth process. It
was found that the band was found at relatively low growth rate. Therefore. this study indicates that increasing the growth
rate is an effective method to eliminate the band formation. Eutectic lamellae nucleate and grow again after the banding formation.
During the initial transition lamellar growth, the relationship between the square lamellar spacing, γ2, and the distance from, the banding, d, can be described by the following equation: γ2 = K [1-exp(A.d)] where K and A are constant. 相似文献