全文获取类型
收费全文 | 727篇 |
免费 | 27篇 |
专业分类
电工技术 | 31篇 |
综合类 | 3篇 |
化学工业 | 237篇 |
金属工艺 | 16篇 |
机械仪表 | 18篇 |
建筑科学 | 14篇 |
能源动力 | 21篇 |
轻工业 | 76篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 60篇 |
一般工业技术 | 125篇 |
冶金工业 | 54篇 |
原子能技术 | 22篇 |
自动化技术 | 75篇 |
出版年
2023年 | 12篇 |
2022年 | 25篇 |
2021年 | 28篇 |
2020年 | 12篇 |
2019年 | 19篇 |
2018年 | 22篇 |
2017年 | 14篇 |
2016年 | 19篇 |
2015年 | 11篇 |
2014年 | 28篇 |
2013年 | 46篇 |
2012年 | 36篇 |
2011年 | 61篇 |
2010年 | 37篇 |
2009年 | 24篇 |
2008年 | 25篇 |
2007年 | 33篇 |
2006年 | 17篇 |
2005年 | 11篇 |
2004年 | 17篇 |
2003年 | 22篇 |
2002年 | 15篇 |
2001年 | 21篇 |
2000年 | 13篇 |
1999年 | 14篇 |
1998年 | 27篇 |
1997年 | 13篇 |
1996年 | 19篇 |
1995年 | 14篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1972年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有754条查询结果,搜索用时 193 毫秒
101.
We recently reported the analysis of the frequency noise in the frequency modulation atomic force microscopy (FM-AFM) both in high-Q and low-Q environments [Rev. Sci. Instrum. 80, 043708 (2009)]. We showed in the paper that the oscillator noise, the frequency fluctuation of the oscillator, becomes prominent in the modulation frequency lower than f(0)∕2Q, where f(0) and Q are the resonance frequency and Q-factor. The magnitude of the oscillator noise is determined by the slope of the phase versus frequency curve of the cantilever at f(0). However, in actual FM-AFM in liquids, the phase versus frequency curve may not be always ideal because of the existence of various phase shifting elements (PSEs). For example, the spurious resonance peaks caused by the acoustic excitation and a band-pass filter in the self-oscillation loop increase the slope of the phase versus frequency curve. Due to those PSEs, the effective Q-factor is often increased from the intrinsic Q-factor of the cantilever. In this article, the frequency noise in the FM-AFM system with the PSEs in the self-oscillation loop is analyzed to show that the oscillator noise is reduced by the increase of the effective Q-factor. It is also shown that the oscillation frequency deviates from the resonance frequency due to the increase of the effective Q-factor, thereby causing the reduction in the frequency shift signal with the same factor. Therefore the increase of the effective Q-factor does not affect the signal-to-noise ratio in the frequency shift measurement, but it does affect the quantitativeness of the measured force in the FM-AFM. Furthermore, the reduction of the frequency noise and frequency shift by the increase of the effective Q-factor were confirmed by the experiments. 相似文献
102.
Yukiya Yamashita Kei Ishiguro Daisuke Nakai Masayoshi Fuji 《Advanced Powder Technology》2019,30(5):1051-1057
The effect of external additives on the synthesis of fumed TiO2 with a high rutile structure content was studied. The focus of this investigation was on the external additive species, agglomerates of the fumed TiO2 before and after the thermal treatment. The transformation ratio from the anatase to rutile structure of the thermally-treated fumed TiO2 was investigated as a function of the fumed TiO2 agglomerate before the thermal treatment. Small agglomerated powders resulted in a decrease of transformation temperature. Two novel results were obtained in this investigation. One was a new fumed TiO2 with a 100% rutile structure having an excellent dispersibility being successfully synthesized by the thermal treatment of AEROXIDE® TiO2 P 25 with a small portion of AEROSIL® R 972. The other was the remarkable acceleration of the transformation from the anatase to rutile structure and grain growth/sintering of the thermally-treated fumed TiO2 observed at a relatively low thermal treatment temperature by the oxidation reaction of calcium stearate as an external additive. 相似文献
103.
Radiation-vulcanization of natural rubber latex (NRL) with n-butyl acrylate gives a higher tensile strength for films obtained after casting. The ageing properties of radiation-vulcanized natural rubber in the presence of various antioxidants have been investigated. In order to find out suitable antioxidants for radiation-vulcanized natural rubber latex (RVNRL) films, extraction of the gel fraction was carried out in xylene with 1 wt.-% antioxidant and air bubbling. Antioxidants which give less reduction in gel fraction due to oxidative degradation during extraction are effective for ageing tests of RVNRL films. It was found that tris(nonylated phenyl) phosphite (Nonflex TNP) and 2,5-di-tert-amylhydroquinone (Antage DAH), among 12 different antioxidants tested, were the most effective antioxidants for RVNRL films. 相似文献
104.
The aim of the present study was to compare the effects of a low-fat diet enriched with oleic acid to those of a low-fat diet
enriched with linoleic acid on fasting lipids, postprandial lipemia, and oxidative susceptibility of low-density lipoprotein
(LDL) in patients with type 2 diabetes mellitus (DM). In a 3-wk randomized crossover study, eight patients with type 2 DM
were given an experimental low-fat diet enriched with either oleic acid or linoleic acid. The oleic-acid-enriched diet contained
5, 15, and 5% energy from saturated, monounsaturated, and polyunsaturated fatty acids, and the linoleic-acid-enriched diet
contained 5, 5, and 15% energy from saturated, monounsaturated, and polyunsaturated fatty acids, respectively. In addition
to evaluating the fasting lipids and oxidative susceptibility of LDL, we evaluated postprandial lipemia using an oral fat
load at the end of each 3-wk dietary phase. There were no significant differences in fasting lipid profile or lag time of
LDL oxidation between the two experimental dietary phases. The average and maximal increments of remnant-like particle (RLP)
cholesterol levels during oral fat load were significantly higher after the oleic-acid-enriched dietary phase than after the
linoleic-acid-enriched dietary phase. The area under the curve of RLP cholesterol was also significantly larger after the
oleicacid-enriched dietary phase than after the linoleic-acid-enriched dietary phase. These results suggest that the oleic-acidenriched
diet was associated with increased formation of postprandial chylomicron remnants compared with the linoleicacid-enriched
diet. 相似文献
105.
Wei Gao Shuichi Dejima Hiroaki Yanai Kei Katakura Satoshi Kiyono Yoshiyuki Tomita 《Precision Engineering》2004,28(3):71
This paper describes a surface motor-driven XY planar motion stage equipped with a newly developed XYθZ surface encoder for sub-micron positioning. The surface motor consists of four linear motors placed on the same surface, two pairs in the XY-axes. The magnetic array and the stator winding of the linear motor are mounted on the platen (the moving element) and the stage base, respectively. The platen can be moved in the X-direction by the X-linear motors, and in the Y-direction by the Y-linear motors. It can also be rotated about the Z-axis if the X- or Y-linear motors generate a moment about the Z-axis. The surface encoder consists of two two-dimensional angle sensors and an angle grid with two-dimensional sinusoidal waves on its surface. The angle grid is mounted on the platen of the stage which is levitated by air-bearings. The angle sensors and the air-bearing pads are fixed on the stage base so that the motion of the platen is not affected by the electronic cables and air hoses. The XY-positions and θZ rotation of the platen can be obtained from the angle sensor outputs with resolutions of approximately 20 nm and 0.2′′, respectively. The surface encoder is placed inside the stage so that the stage system is very compact in size. Experimental results indicate that precision positioning can be carried out independently in X, Y and θZ with resolutions of 200 nm and 1′′, respectively. 相似文献
106.
Understanding the Structural Evolution and Redox Mechanism of a NaFeO2–NaCoO2 Solid Solution for Sodium‐Ion Batteries
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kei Kubota Takuya Asari Hiroaki Yoshida Hiromasa Shiiba Masanobu Nakayama Shinichi Komaba 《Advanced functional materials》2016,26(33):6047-6059
Na‐ion batteries have become promising candidates for large‐scale energy‐storage systems because of the abundant Na resources and they have attracted considerable academic interest because of their unique behavior, such as their electrochemical activity for the Fe3+/Fe4+ redox couple. The high‐rate performance derived from the low Lewis‐acidity of the Na+ ions is another advantage of Na‐ion batteries and has been demonstrated in NaFe1/2Co1/2O2 solutions. Here, a solid solution of NaFeO2‐NaCoO2 is synthesized and the mechanisms behind their excellent electrochemical performance are studied in comparison to those of their respective end‐members. The combined analysis of operando X‐ray diffraction, ex situ X‐ray absorption spectroscopy, and density functional theory (DFT) calculations for Na1– x Fe1/2Co1/2O2 reveals that the O3‐type phase transforms into a P3‐type phase coupled with Na+/vacancy ordering, which has not been observed in O3‐type NaFeO2. The substitution of Co for Fe stabilizes the P3‐type phase formed by sodium extraction and could suppress the irreversible structural change that is usually observed in O3‐type NaFeO2, resulting in a better cycle retention and higher rate performance. Although no ordering of the transition metal ions is seen in the neutron diffraction experiments, as supported by Monte‐Carlo simulations, the formation of a superlattice originating from the Na+/vacancy ordering is found by synchrotron X‐ray diffraction for Na0.5Fe1/2Co1/2O2, which may involve a potential step in the charge/discharge profiles. 相似文献
107.
We have mechanically fabricated Au, Ag, and Cu nanocontacts in solution under electrochemical potential control. At the hydrogen evolution potential, fractional conductance peaks appeared near 0.5 G(0) (G(0) = 2e(2)/h) in the conductance histogram of Au and Cu. This fractional conductance peak was not observed in the conductance histogram of Ag. In the case of Au nanocontacts in 50?mM H(2)SO(4) solution, a 0.1 G(0) peak appeared in the conductance histogram, as well as the 0.5 G(0) peak. The origin of the fractional conductance peak and its metal dependence are discussed based on previously reported values of metal-hydrogen binding energy, which was estimated by the exchange current density for the hydrogen evolution reaction. 相似文献
108.
Alumina nanotubes were fabricated by a template method. Tris-(8-hydroxyquinoline) gallium (GaQ3) organic nanowires were used as a soft template for coating with alumina using an atomic layer deposition technique. The deposition was conducted at 25 degrees C by using trimethylaluminum and distilled water as the precursors of Al2O3. Amorphous alumina nanotubes were obtained after removing the GaQ3 by dissolving in toluene or by heat treatment at 350 degrees C. The amorphous nanotubes could be crystallized by heating at 900 degrees C for 1 h in vacuum. 相似文献
109.
Ferritin nanoparticles ornamented with a Ti-binding peptide are versatile nanoscaled building blocks. Their specific binding ability is strong enough to position them on nanopatterned Ti regions on a Pt substrate. Furthermore, the peptides mineralization activity enables the formation of titania on the outer side of the particle, and the particle's inner nanospaces can serve as a carrier for inorganic nanodots. Making use of all these properties, here we show controlled in aqua fabrication of three-dimensional nanoscale structures. The X-Y positioning obeyed the specific binding of the peptide, while fabrication in the Z-dimension entailed stepwise formation of titania and ferritin layers by alternately applying the binding and mineralization abilities of the Ti-binding peptide. This method paves the way for in aqua fabrication of nanodevices having complicated structures and functions. 相似文献
110.
Joshi RK Yoshimura M Matsuura Y Ueda K Tanaka K 《Journal of nanoscience and nanotechnology》2007,7(12):4272-4277
Pd nanoparticles of well-defined shapes with face centered cubic structure were grown electrochemically on silicon substrates with high degree of reproducibility. As direct application of these electrochemically grown Pd nanostructures they have been used as catalyst for the growth of multi wall carbon nanotube (MWCNT). It is observed that the MWCNTs are filled with a Pd based material during growth by microwave plasma enhanced chemical vapor deposition (MPECVD) technique. High-resolution transmission electron microscopy, used to study the material inside MWCNT suggests the formation of PdH0.649 or Pd2Si during the growth of carbon nanotube. Raman spectroscopy has been used to study the structure of the MPECVD grown carbon nanotubes. 相似文献