全文获取类型
收费全文 | 5080篇 |
免费 | 102篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 220篇 |
综合类 | 5篇 |
化学工业 | 1235篇 |
金属工艺 | 119篇 |
机械仪表 | 114篇 |
建筑科学 | 93篇 |
能源动力 | 207篇 |
轻工业 | 316篇 |
水利工程 | 10篇 |
石油天然气 | 8篇 |
无线电 | 635篇 |
一般工业技术 | 907篇 |
冶金工业 | 965篇 |
原子能技术 | 92篇 |
自动化技术 | 263篇 |
出版年
2023年 | 23篇 |
2022年 | 30篇 |
2021年 | 56篇 |
2020年 | 21篇 |
2019年 | 42篇 |
2018年 | 50篇 |
2017年 | 49篇 |
2016年 | 68篇 |
2015年 | 55篇 |
2014年 | 100篇 |
2013年 | 180篇 |
2012年 | 143篇 |
2011年 | 225篇 |
2010年 | 174篇 |
2009年 | 193篇 |
2008年 | 214篇 |
2007年 | 159篇 |
2006年 | 152篇 |
2005年 | 121篇 |
2004年 | 128篇 |
2003年 | 146篇 |
2002年 | 144篇 |
2001年 | 132篇 |
2000年 | 96篇 |
1999年 | 166篇 |
1998年 | 410篇 |
1997年 | 252篇 |
1996年 | 209篇 |
1995年 | 138篇 |
1994年 | 139篇 |
1993年 | 111篇 |
1992年 | 81篇 |
1991年 | 79篇 |
1990年 | 81篇 |
1989年 | 74篇 |
1988年 | 71篇 |
1987年 | 49篇 |
1986年 | 62篇 |
1985年 | 44篇 |
1984年 | 54篇 |
1983年 | 43篇 |
1982年 | 35篇 |
1981年 | 40篇 |
1980年 | 49篇 |
1979年 | 56篇 |
1978年 | 34篇 |
1977年 | 45篇 |
1976年 | 54篇 |
1973年 | 22篇 |
1972年 | 22篇 |
排序方式: 共有5189条查询结果,搜索用时 0 毫秒
141.
142.
Ireneusz Buganski Kotoba Toyonaga Hiroyuki Takakura Tsunetomo Yamada Marc de Boissieu Olivier Perez 《Materials Science & Technology》2020,36(9):989-995
ABSTRACTWe report a successful growth of the ZnMgHf F-type icosahedral quasicrystal in the form of faceted single grains. By varying the heat treatment parameters we were able to obtain single crystals with a quality suitable for a single crystal X-ray diffraction which was conducted in a synchrotron facility. Ab initio structure solution by a charge flipping algorithm manifests the existence of two types of Bergman clusters. Clusters are differentiated by the preferential occupation of the high-symmetry positions by hafnium in a rhombic triacontahedron, being the outer shell of the atomic cluster.This paper is part of a Thematic Issue on The Crystallographic Aspects of Metallic Alloys. 相似文献
143.
144.
145.
146.
Effects of Gd Substitution on Sintering and Optical Properties of Highly Transparent (Y0.95−xGdxEu0.05)2O3 Ceramics
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bin Lu Ji‐Guang Li Hidehiko Tanaka Xudong Sun Yoshio Sakka 《Journal of the American Ceramic Society》2015,98(8):2480-2487
Highly transparent (Y0.95?xGdxEu0.05)2O3 (x = 0.15–0.55) ceramics have been fabricated by vacuum sintering at the relatively low temperature of 1700°C for 4 h with the in‐line transmittances of 73.6%–79.5% at the Eu3+ emission wavelength of 613 nm (~91.9%–99.3% of the theoretical transmittance of Y1.34Gd0.6Eu0.06O3 single crystal), whereas the x = 0.65 ceramic undergoes a phase transformation at 1650°C and has a transparency of 53.4% at the lower sintering temperature of 1625°C. The effects of Gd3+ substitution for Y3+ on the particle characteristics, sintering kinetics, and optical performances of the materials were systematically studied. The results show that (1) calcining the layered rare‐earth hydroxide precursors of the ternary Y–Gd–Eu system yielded rounded oxide particles with greatly reduced hard agglomeration and the particle/crystallite size slightly decreases along with increasing Gd3+ incorporation; (2) in the temperature range 1100°C–1480°C, the sintering kinetics of (Y0.95?xGdxEu0.05)2O3 is mainly controlled by grain‐boundary diffusion with similar activation energies of ~230 kJ/mol; (3) Gd3+ addition promotes grain growth and densification in the temperature range 1100°C–1400°C; (4) the bandgap energies of the (Y0.95?xGdxEu0.05)2O3 ceramics generally decrease with increasing x; however, they are much lower than those of the oxide powders; (5) both the oxide powders and the transparent ceramics exhibit the typical red emission of Eu3+ at ~613 nm (the 5D0→7F2 transition) under charge transfer (CT) excitation. Gd3+ incorporation enhances the photoluminescence and shortens the fluorescence lifetime of Eu3+. 相似文献
147.
Research and Development of the Coprecipitation Process for Lanthanum Germanate Oxyapatite
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kiyoshi Kobayashi Shouta Kitajima Yukihito Igarashi Tohru Higuchi Yoshio Sakka 《Journal of the American Ceramic Society》2015,98(1):66-70
Although lanthanum germanate oxyapatite (La–Ge–O) has shown good potential for use as a solid electrolyte in energy storage applications, its synthesis has been challenging by either solid‐ or solution‐state methods. In this study, a new synthesis of La–Ge–O was developed through a coprecipitation technique, in which a highly concentrated homogeneous aqueous solution of La and Ge was prepared from aqueous ammonium germanate and lanthanum nitrate solutions with the addition of dilute nitric acid. Several precipitates were formed by pH manipulation, including an amorphous material obtained at pH > 3. Compared to the individual precipitation behaviors of the parent compounds, the amorphous precipitate was formed only from the aqueous two‐component mixture, and appeared to contain both metals. This material was transformed into crystalline mixtures upon heating at 1273 K. The crystalline phases were La2Ge3O9 and hexagonal‐type GeO2 when the precipitate was formed below pH 8, and the La–Ge–O and La2Ge2O7 phases when the precipitate was formed around pH 8. Product formation from the coprecipitate was discussed based on X‐ray diffraction and thermal analyses. The improved availability of La–Ge–O will allow more extensive investigations of its useful properties. 相似文献
148.
Pectin is one of the biopolymers in the cell walls of all plant tissues, but the pectin‐containing materials have been discarded as industrial waste in food‐processing factories. We prepared a water‐insoluble pectin‐inorganic composite material by mixing pectin and a silane coupling reagent, bis(3‐trimethoxysilylpropyl)amine. The mechanical strength of the pectin‐inorganic composite material was higher than that of the pectin material without the addition of an inorganic component. In addition, the thermal stability of the composite material increased with the addition of the inorganic component. Furthermore, when the pectin‐inorganic composite materials were incubated in an aqueous solution of Cu(II), Zn(II), or In(III), these composite materials effectively accumulated not only the heavy metal ions, but also rare‐earth metal ions. Additionally, based on the infrared (IR) measurements, the metal ion accumulative mechanism into the composite material is described. As a result, the IR spectra suggested an electrostatic interaction between the metal ion and carboxy group in the pectin. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42056. 相似文献
149.
Photodetectors: Ultrathin SnSe2 Flakes Grown by Chemical Vapor Deposition for High‐Performance Photodetectors (Adv. Mater. 48/2015)
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
150.
Hiroyuki Yamada Atsushi Tsurumaki‐Fukuchi Masaki Kobayashi Takuro Nagai Yoshikiyo Toyosaki Hiroshi Kumigashira Akihito Sawa 《Advanced functional materials》2015,25(18):2708-2714
Tunnel electroresistance in ferroelectric tunnel junctions (FTJs) has attracted considerable interest, because of a promising application to nonvolatile memories. Development of ferroelectric thin‐film devices requires atomic‐scale band‐structure engineering based on depolarization‐field effects at interfaces. By using FTJs consisting of ultrathin layers of the prototypical ferroelectric BaTiO3, it is demonstrated that the surface termination of the ferroelectric in contact with a simple‐metal electrode critically affects properties of electroresistance. BaTiO3 barrier‐layers with TiO2 or BaO terminations show opposing relationships between the polarization direction and the resistance state. The resistance‐switching ratio in the junctions can be remarkably enhanced up to 105% at room temperature, by artificially controlling the fraction of BaO termination. These results are explained in terms of the termination dependence of the depolarization field that is generated by a dead layer and imperfect charge screening. The findings on the mechanism of tunnel electroresistance should lead to performance improvements in the devices based on nanoscale ferroelectrics. 相似文献