全文获取类型
收费全文 | 1733篇 |
免费 | 28篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 109篇 |
化学工业 | 292篇 |
金属工艺 | 58篇 |
机械仪表 | 31篇 |
建筑科学 | 17篇 |
矿业工程 | 1篇 |
能源动力 | 60篇 |
轻工业 | 130篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 157篇 |
一般工业技术 | 268篇 |
冶金工业 | 516篇 |
原子能技术 | 35篇 |
自动化技术 | 86篇 |
出版年
2023年 | 7篇 |
2022年 | 21篇 |
2021年 | 33篇 |
2020年 | 8篇 |
2019年 | 18篇 |
2018年 | 24篇 |
2017年 | 17篇 |
2016年 | 27篇 |
2015年 | 16篇 |
2014年 | 28篇 |
2013年 | 75篇 |
2012年 | 41篇 |
2011年 | 72篇 |
2010年 | 35篇 |
2009年 | 52篇 |
2008年 | 60篇 |
2007年 | 40篇 |
2006年 | 41篇 |
2005年 | 49篇 |
2004年 | 41篇 |
2003年 | 50篇 |
2002年 | 36篇 |
2001年 | 48篇 |
2000年 | 39篇 |
1999年 | 55篇 |
1998年 | 179篇 |
1997年 | 125篇 |
1996年 | 87篇 |
1995年 | 47篇 |
1994年 | 64篇 |
1993年 | 51篇 |
1992年 | 26篇 |
1991年 | 16篇 |
1990年 | 13篇 |
1989年 | 20篇 |
1988年 | 11篇 |
1987年 | 18篇 |
1986年 | 17篇 |
1985年 | 29篇 |
1984年 | 9篇 |
1983年 | 16篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1978年 | 7篇 |
1977年 | 19篇 |
1976年 | 19篇 |
1975年 | 5篇 |
1973年 | 4篇 |
1968年 | 4篇 |
排序方式: 共有1763条查询结果,搜索用时 0 毫秒
61.
Effects of pressure and temperature on dyeing acrylic fibres with basic dyes in supercritical carbon dioxide 总被引:2,自引:0,他引:2
The dyeing of acrylic fibre with CI Basic Blue 47 has been investigated using an ammonium carboxylate perfluoropolyether as an auxiliary in order to perform the reverse micellar system in supercritical carbon dioxide media. The basic dye was satisfactorily solubilised in the interior of the reverse micelle in the system, and dyeability in the supercritical carbon dioxide media was excellent, even in the absence of a retardant and/or an acid. The optimum proton-rich condition for dyeing of acrylic fabric is performed in reverse micelle aggregates and the proton-rich water pool is suitable for dye uptake by the fibre even without the presence of additives. Changes in glass transition temperature of acrylic fibre in the carbon dioxide media also influence the dyeing behaviour of acrylic fabric. 相似文献
62.
63.
Plasma surface treatments have been used very often to enhance the surface properties of metallic materials. In this work, Ti6Al4V titanium alloy was treated by nitrogen plasma immersion ion implantation (NPIII) in order to obtain improvements in its surface properties, such as corrosion resistance evaluated here. The microstructure and corrosion behavior of the implanted and unimplanted samples were evaluated, using, XRD, GDOES and potentiodynamic polarization and impedance electrochemical spectroscopy tests in 0.6 M NaCl solution. It was verified that the NPIII created resistant layers to corrosive attacks. In corrosion tests by polarization, the implanted samples showed corrosion current density reduction of about 10 times compared to the Ti6Al4V alloy without treatment. Besides that, it was also observed a reduction of the passive current density of one order of the magnitude. In all the studied cases, the polarization curves were shifted to more positive values of potentials, indicating a lower tendency of these PIII treated surfaces to corrosion. The implantation process produced a thin TiN surface layer followed by Ti2N and then a layer with nitrogen in solid solution, all detected by GDOES combined with X-ray diffraction. These layers promoted an excellent polarization resistance of the Ti6Al4V surfaces on impedance spectroscopy tests also. This better performance in these tests can be correlated with the formation of continuous nitride layer, which could retard chloride ions ingress into the substrate. 相似文献
64.
Investigation of laser consolidation process for metal powder by two-color pyrometer and high-speed video camera 总被引:2,自引:0,他引:2
This paper deals with the measurement of surface temperature on metal powder during the laser consolidation process with two-color pyrometer. Additionally, the aspect of selective laser sintering (SLS) and selective laser melting (SLM) of metal powder is visualized with high speed video camera. As a result, the surface temperature during the laser irradiation was ranged 1520–1810 °C and the consolidation phenomena was classified according to the melting point of metal powder. The metal powder at the heating process cohered intermittently to the melt pool although the laser beam was continuously irradiated to the powder surface. 相似文献
65.
Haruyuki Murakami Hiroshi Ueda Atsushi Ishiyama Norikiyo Koizumi Kiyoshi Okuno 《Electrical Engineering in Japan》2010,171(3):7-15
In the ITER Engineering Design Activity (EDA), four NB3Sn model coils were developed and successfully tested. However, it was revealed that the critical current of the conductor degraded with the increase of electromagnetic force. One of the explanations of this phenomenon is a strand bending caused by enormous electromagnetic force. The authors therefore developed a simulation code using the distributed circuit model to investigate dependency of the critical current performance on the periodic bending deformation. The simulation results were in good agreement with the experiments. The dependence of the critical current on the periodic transverse load, temperature, periodic load pitch, thickness of Ta barrier which prevents Cu stabilizer from being contaminated by Sn, twist pitch of the strand, and RRR of the bronze matrix was investigated using the developed code. The results showed that the critical current degraded less with decreasing the pitch of the transverse load and increasing the Ta barrier thickness. It suggests that the shorter cabling pitch and the larger bending stiffness prevent the critical current degradation. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 7–15, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20923 相似文献
66.
67.
Kikuo Matsui Hideki Shimada Takashi Sasaoka Hirofumi Furukawa Takeshi Ueda Atsuko Yabuki 《国际露天开采、回填与环境杂志》2013,27(3):185-204
Conventional highwall mining extracts coal with an auger machine or a continuous miner from exposed seams at the base of opencut or strip operations. However, under poor strata and high stress conditions, highwall mining cannot be conducted due to pillar and roof failures. In such cases, punch highwall mining is more effective than the conventional highwall mining. This paper describes conventional highwall mining and punch highwall mining systems and discusses the stability of the highwall due to punch highwall mining at opencut coal mines. 相似文献
68.
Single phase β-Zn4Sb3 was prepared by the application of a two-stage heat treatment, and impurity elements were doped. The undoped and doped samples
were prepared by direct melting followed by two-stage heat treatment at 450°C and 400°C after solidification of the samples
in sealed quartz ampoules. Impurity doping of the samples was performed by the addition of 1 at.% of Se, In, Pb, Te, or Bi.
The resulting samples were characterized by x-ray diffraction (XRD), differential thermal analysis (DTA), optical microscopy,
and electron probe microanalysis, and their Seebeck coefficients were determined at room temperature. The undoped samples
were determined by XRD and DTA to comprise single phase β-Zn4Sb3, while the doped samples were composed of multiple phases. From the measurements of the Seebeck coefficient, all samples
were found to be p-type and all were found to have almost the same values. These results indicate that β-Zn4Sb3 has limited solubility for these impurity elements. 相似文献
69.
Perovskite-type oxides, BaMoO3 and SrMoO3, were prepared by reduction of scheelite-type oxides, BaMoO4 and SrMoO4, in H2 flow at 873 K and characterized by XRD, TG, SEM, TPR, NH3-TPD, UV-vis DRS and BET measurement. The catalytic activity of these alkaline-earth molybdenum oxide catalysts was tested for oxidation of 2-propanol with gaseous oxygen under atmospheric pressure. Dehydration to propylene was mainly promoted over the scheelite-type with Mo6+, while oxidative dehydrogenation to acetone was mainly promoted over the perovskite-type with Mo4+, and selectivity to acetone was much higher over BaMoO3 than over SrMoO3. Both perovskite-type oxide catalysts underwent oxidation to some degree during the catalytic reaction, so that they also contained some Mo6+. We concluded that the high selectivity to acetone resulting from oxidative dehydrogenation during 2-propanol conversion is related to the constantly changing oxidation state of the catalyst, resulting in coexistence of Mo6+ octahedra and Mo4+ octahedra on the AMoO3 oxides. 相似文献
70.
Hidenori Hiramatsu Yoichi Kamihara Hiroshi Yanagi Kazushige Ueda Toshio Kamiya Masahiro Hirano Hideo Hosono 《Journal of the European Ceramic Society》2009,29(2):245-253
Optoelectronic properties and device applications of layered mixed-anion compounds such as oxychalcogenide LaCuOCh (Ch = chalcogen) and oxypnictide LaTMOPn (TM = 3d transition metal, Pn = pnicogen) are reviewed. Several distinctive functions have been found in these materials based on our original material exploration concept. Fabrication of high-quality epitaxial films of LaCuOCh leads to clarifying the excellent electrical and optical properties such as high hole mobility of 8 cm2/(V s) and heavy hole doping at >1021 cm?3 in LaCuOSe, and sharp and tunable-wavelength photoluminescence in the solid–solution systems in LaCuOCh. In addition, a room temperature operation of a light-emitting diode is demonstrated using LaCuOSe as a light-emitting layer. These results suggest that the layered oxychalcogenides have potential for light-emitting layers as well as transparent hole-injection layers in organic/inorganic light-emitting diodes. Furthermore, by extending the material system from the copper-based oxychalcogenides to isostructural compounds, transition metal-based oxypnictides LaTMOP (TM = Fe, Ni), we have found novel superconductors, LaFeOP and LaNiOP. 相似文献