全文获取类型
收费全文 | 1397篇 |
免费 | 63篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 93篇 |
综合类 | 2篇 |
化学工业 | 397篇 |
金属工艺 | 30篇 |
机械仪表 | 41篇 |
建筑科学 | 33篇 |
能源动力 | 48篇 |
轻工业 | 103篇 |
水利工程 | 2篇 |
无线电 | 90篇 |
一般工业技术 | 287篇 |
冶金工业 | 127篇 |
原子能技术 | 90篇 |
自动化技术 | 120篇 |
出版年
2023年 | 8篇 |
2022年 | 29篇 |
2021年 | 38篇 |
2020年 | 24篇 |
2019年 | 30篇 |
2018年 | 25篇 |
2017年 | 38篇 |
2016年 | 38篇 |
2015年 | 40篇 |
2014年 | 34篇 |
2013年 | 86篇 |
2012年 | 55篇 |
2011年 | 87篇 |
2010年 | 66篇 |
2009年 | 67篇 |
2008年 | 77篇 |
2007年 | 73篇 |
2006年 | 52篇 |
2005年 | 44篇 |
2004年 | 54篇 |
2003年 | 37篇 |
2002年 | 44篇 |
2001年 | 29篇 |
2000年 | 27篇 |
1999年 | 25篇 |
1998年 | 63篇 |
1997年 | 41篇 |
1996年 | 29篇 |
1995年 | 33篇 |
1994年 | 14篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 4篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1973年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有1463条查询结果,搜索用时 15 毫秒
51.
d -Glucaric acid (GA) is the one of aldaric acids and is an important bio-based building block for polymers. In this study, poly(m-xylylene-acetyl glucaramide) and poly(p-xylylene-acetyl glucaramide) were synthesized from GA acetate and two kind of aromatic diamines by solution polymerization. The chemical structures of the polyamides were analyzed by nuclear magnetic resonance spectroscopy. The weight-average molecular weights ranged from 3.3 × 103 to 1.15 × 104 with a polydispersity of 1.6–1.9, depending on monomer ratio or monomer concentration in solution. The 10% decomposition temperature of the polymers was about 210 °C. Differential scanning calorimetry revealed that the polyamides exhibited no peaks attributed to crystallization or melting point, which indicated that the polyamides were amorphous. No crystalline pattern was observed in the X-ray diffractograms, supporting this result. Polarized optical microscopy observation revealed that the polyamides exhibited melting-like behavior at above 150 °C, which was attributed to glass-transition behavior. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47255. 相似文献
52.
Yutaka Kawahara Atsushi Nakayama Masatoshi Shioya Masaki Tsuji Hideki Yamane Tadahisa Iwata 《Journal of Materials Science》2012,47(4):1887-1892
Structure of poly(dioxanone) (PPDX) fibers produced through a two-step melt-spinning process with an additional short-period
annealing above the melting temperature of PPDX was investigated and the effect of annealing on the degradation behavior was
discussed. The morphological study carried out by etching the fibers using a phosphate or permanganate solution suggested
that the fibers take a skin–core structure, and both the skin layer and the core region consist of a bundle of microfibrils.
The micro-beam X-ray diffraction analysis revealed that the short-period annealing in the production process only slightly
promotes the crystallization in the skin layer but contributes to increasing the packing of amorphous chains near the skin,
which seems to be the controlling factor of the hydrolytic degradation behavior of the fibers. 相似文献
53.
54.
Masao Shibuya Motoshi Kato Masaki Ozawa P. H. Fang Eiji Ōsawa 《Fullerenes, Nanotubes and Carbon Nanostructures》2013,21(2):181-193
Abstract It was confirmed that soot produced by free burning of small hydrocarbons like benzene and cyclohexane generally contains less than 0.1 ppm of C60. Small, but measurable amounts of C60 were found in two samples of charcoal, providing the first indication of fullerene formation in the solid state. 相似文献
55.
56.
57.
58.
Operation Assist by Vibration Suppression Control Using Impulse‐Shaped Signals for Power Assist Conveyance System
下载免费PDF全文
![点击此处可从《Electrical Engineering in Japan》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yuichi Yamamoto Masaki Uchida Yoshifumi Morita Susumu Hara 《Electrical Engineering in Japan》2014,186(2):31-39
This paper presents an assist control method for a flexible parts conveyance task using a power assist conveyance system. The assist control method should be designed so as not only to suppress vibration but also to reduce the degradation of operating feel. For this purpose, multiple impulse‐shaped signals are used as feedforward signals in order to reduce the vibration of flexible parts during conveyance. In addition, the adjustment time is introduced to adjust the input timing of the impulse‐shaped signal and to suppress vibration. In order to improve the degradation of operating feel, the smaller amplitudes of the three impulse‐shaped signals are used and input repeatedly. The effectiveness of the proposed system was verified experimentally. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(2): 31–39, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22476 相似文献
59.
Effects of Atmospheric Composition on the Molecular Structure of Synthesized Silicon Oxycarbides
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)
Masaki Narisawa Fuji Funabiki Akihiro Iwase Fumihiro Wakai Hideo Hosono 《Journal of the American Ceramic Society》2015,98(10):3373-3380
The dependence of silicon oxycarbides' chemical composition and molecular structure on their reaction conditions was tested by varying the atmosphere under which pyrolysis was performed. To obtain the silicon oxycarbides, densely cross‐linked silicone resin particles with an averaged diameter of 2 μm were pyrolyzed in various atmospheres of H2, Ar, and CO2, in the temperature range 700°C–1100°C. The residual mass of resin after pyrolysis was almost constant at 700°C, although their apparent colors varied distinctly. The sample obtained from the H2 atmosphere was white, whereas that obtained from the CO2 atmosphere was dark brown. Fourier‐transform infrared (FT‐IR) spectra of the residues suggested that the Si–O–Si network evolution was accelerated in the CO2 atmosphere. Beyond 800°C, the chemical compositions of the compounds obtained from a H2 atmosphere increasingly approached near‐stoichiometric SiO2–xSiC composition with increasing the pyrolysis temperature. Compounds from a CO2 atmosphere approached a composition of SiO2–xC with no free SiC as the pyrolysis temperature increased. In the products from an Ar atmosphere, SiO2–xSiC–yC compositions were typically obtained. The observed effects of the pyrolysis atmosphere on the resulting chemical compositions were analyzed in terms of thermodynamic calculations. Electron spin resonance (ESR) spectra revealed broad and intense signals from products obtained from either Ar or CO2. Estimating from the signal intensity, the residual spin concentrations were in the range 1018–1019 g?1. Meanwhile, the spectra from the samples obtained in H2 showed weak and sharp signals with estimated spin concentrations ranging from 1016–1017 g?1. This signal attenuation may have been due to the hydrogen capping of dangling bond formed during pyrolysis. 相似文献
60.
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