全文获取类型
收费全文 | 572篇 |
免费 | 24篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 14篇 |
综合类 | 1篇 |
化学工业 | 134篇 |
金属工艺 | 9篇 |
机械仪表 | 14篇 |
建筑科学 | 6篇 |
能源动力 | 37篇 |
轻工业 | 55篇 |
无线电 | 50篇 |
一般工业技术 | 157篇 |
冶金工业 | 64篇 |
原子能技术 | 4篇 |
自动化技术 | 52篇 |
出版年
2023年 | 13篇 |
2022年 | 29篇 |
2021年 | 35篇 |
2020年 | 23篇 |
2019年 | 22篇 |
2018年 | 31篇 |
2017年 | 26篇 |
2016年 | 20篇 |
2015年 | 19篇 |
2014年 | 20篇 |
2013年 | 55篇 |
2012年 | 37篇 |
2011年 | 21篇 |
2010年 | 24篇 |
2009年 | 23篇 |
2008年 | 12篇 |
2007年 | 16篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 18篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有597条查询结果,搜索用时 15 毫秒
131.
Claudia Ott Felix Reiter Maximilian Baumgartner Markus Pielmeier Anna Vogel Patrick Walke Stefan Burger Michael Ehrenreich Gregor Kieslich Dominik Daisenberger Jeff Armstrong Ujwal Kumar Thakur Pawan Kumar Shunda Chen Davide Donadio Lisa S. Walter R. Thomas Weitz Karthik Shankar Tom Nilges 《Advanced functional materials》2019,29(18)
Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic‐scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer‐like atomic‐scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III‐V, or II‐VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core–shell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting. 相似文献
132.
Sandeep R. Saksham Sharma Mayank Thakur P. K. Bora 《Multimedia Tools and Applications》2016,75(13):7779-7797
The perceptual video hash function defines a feature vector that characterizes a video depending on its perceptual contents. This function must be robust to the content preserving manipulations and sensitive to the content changing manipulations. In the literature, the subspace projection techniques such as the reduced rank PARAllel FACtor analysis (PARAFAC), have been successfully applied to extract perceptual hash for the videos. We propose a robust perceptual video hash function based on Tucker decomposition, a multi-linear subspace projection method. We also propose a method to find the optimum number of components in the factor matrices of the Tucker decomposition. The Receiver Operating Characteristics (ROC) curves are used to evaluate the performance of the proposed algorithm compared to the other state-of-the-art projection techniques. The proposed algorithm shows superior performance for most of the image processing attacks. An application for indexing and retrieval of near-identical videos is developed using the proposed algorithm and the performance is evaluated using average recall/precision curves. The experimental results show that the proposed algorithm is suitable for indexing and retrieval of near-identical videos. 相似文献
133.
Photocatalysis: Evidence and Effect of Photogenerated Charge Transfer for Enhanced Photocatalysis in WO3/TiO2 Heterojunction Films: A Computational and Experimental Study (Adv. Funct. Mater. 18/2017)
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)
134.
135.
136.
Reaction of poly(ethylene terephthalate) waste (PETW) powder with ethylene glycol (EG) using 0.003 mol lead acetate as a catalyst was carried out in a batch reactor at 470 K under atmospheric pressure. Reactions were undertaken with various particle sizes ranging from 50 to 512.5 μm and reaction times ranging from 10 to 60 min at 10‐min intervals. A low molecular weight product of PETW was obtained using this reaction. Then hydrazine monohydrate, chlorobenzene, and cyclohexylamine (CHA) were introduced to convert the low molecular weight product of PETW into terephthalohydrazide (TPHD). To increase the PETW conversion rate, an external catalyst (lead acetate) was introduced during the reaction. The reaction product was deposited onto the surface of unreacted PETW that was removed from the surface by introducing dimethyl sulfoxide. To accelerate the reaction rate CHA was introduced during the second stage of reaction, which has industrial significance. Depolymerization of PETW was proportional to the reaction time and inversely proportional to the particle size of PETW. Analyses of value‐added products (TPHD and EG) as well as PETW were undertaken. A kinetic model was developed and experimental data were simulated consistent with the model. A thermodynamic study was undertaken because this is required during the transfer of laboratory data through the pilot plant for commercialization. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3437–3444, 2003 相似文献
137.
Praveen Singh Thakur Koji Sugano Toshiyuki Tsuchiya Osamu Tabata 《Microsystem Technologies》2014,20(3):403-411
The effect of in- and anti-phase mode decoupling on the frequency response of coupled in-plane resonators was examined, experimentally, to suppress the acceleration sensitivity (acceleration output) in tuning fork gyroscopes (TFGs). Finite element simulations, conducted in our recent works, show that the origin of acceleration sensitivity for the sensing resonators in TFGs lies in the transduction of linear (in-phase) acceleration to anti-phase resonant vibration of the sensing resonators in TFGs. We further revealed that the frequency decoupling of the in- and anti-phase vibration modes is effective in suppressing the transduction. To experimentally validate this, two types of coupled resonators (one coupled with a frame and the other with a spring) to represent the sensing resonators of TFGs were fabricated on silicon-on-insulator wafer. Different resonant frequencies were used to evaluate the frequency decoupling effect on the coupled resonators, i.e., the coupling from in-phase mode oscillation to the anti-phase mode vibration. The vibration amplitude of the anti-phase mode increased in the coupled resonators with small frequency decoupling (decoupling ratio, DR) value. Additionally, the two types of coupled resonators exhibit similar output after considering the effect of decoupling ratio, anti-phase frequency and different stiffness unbalances. Our results reveal that TFG can be designed with lower acceleration sensitivity by utilizing sense resonators with large decoupling ratio, higher anti-phase frequency, and possessing structures which are insensitive to fabrication imperfections. 相似文献
138.
Ross D. Rieke Deepak S. Thakur Brian D. Roberts Geoffrey T. White 《Journal of the American Oil Chemists' Society》1997,74(4):341-345
Fatty alcohols are produced by hydrogenating fatty methyl esters in slurry phase in the presence of copper chromite catalyst
at temperatures of 250–300°C and hydrogen pressures of 2000–3000 psi. The fatty methyl ester, catalyst, and hydrogen are fed
to the reactor cocurrently. The product slurry is passed through gas-liquid separators and then through a continuous filtration
system for removal of the catalyst. A portion of the used catalyst in crude alcohol is recycled to the hydrogenator. The overall
efficiency of the process depends upon the intrinsic activity, life, and filterability of the catalyst. The fatty alcohol
producer therefore requires a catalyst with high activity, long life, and good separation properties. The main goal of the
present laboratory investigation was to develop a superior copper chromite catalyst for the slurry-phase process. Two copper
chromite catalysts, prepared by different procedures, were tested for methyl ester hydrogenolysis activity, reusability, and
filtration characteristics. The reaction was carried out in a batch autoclave at 280°C and 2000–3000 psi hydrogen pressure.
The reaction rates were calculated by assuming a kinetic mechanism that was first-order in methyl ester concentration. The
catalyst with the narrower particle size distribution was 30% more active, filtered faster, and maintained activity for several
more uses than the catalyst with the broader particle size distribution. X-ray photoelectron spectroscopy data showed higher
surface copper concentrations for the former catalyst. 相似文献
139.
The major sterols of the seeds ofBenincasa cerifera, Cucumis sativus, Cucurbita maxima, C. pepo andTrichosanthes japonica and of the mature plant tissues (leaves and stems) ofCitrullus battich, Cucumis sativus andGynostemma pentaphyllum of the family Cucurbitaceae were 24-ethyl-Δ7-sterols which were accompanied by small amounts of saturated and Δ5-and Δ8-sterols. The 24-ethyl-Δ7,22,Δ7,25(27) and Δ7,22,25(27)-sterols constituted the predominant sterols for the seed materials, whereas the 24-ethyl-Δ7 and Δ7,22-sterols were the major ones for the mature plant tissues. The configurations of C-24 of the alkylsterols were examined by
high resolution1H NMR and13C NMR spectroscopy. Most of the 24-methyl- and 24-ethylsterols examined which lack a Δ25(27)-bond (i.e., 24-methyl-, 24-methyl-Δ22-, 24-ethyl- and 24-ethyl-Δ22 sterols) were shown to occur as the C-24 epimeric mixtures in which the 24α-epimers predominated in most cases. The 24-ethylsterols
which possess a Δ25(27) (i.e., 24-ethyl-Δ25(27)-and 24-ethyl-Δ7,22,25(27)-sterols) were, on the other hand, composed of only 24β-epimers. The Δ8-sterols identified and characterized were four 24-ethyl-sterols: 24α-and 24β-ethyl-5α-cholesta-8,22-dien-3β-ol, 24β-ethyl-5α-cholesta-8,25(27)-dien-3β-ol
and 24β-ethyl-5α-cholesta-8,22,25(27)-trien-3β-ol. This seems to be the first case of the detection of Δ8-sterols lacking a 4-methyl group in higher plants, and among the four Δ8-sterols the latter two are considered to be new sterols. The probable biogenetic role of the Δ8-sterols and the possible biosynthetic pathways leading to the 24α- and 24β-alkylsterols in Cucurbitaceae are discussed. 相似文献
140.
The course and kinetics of nonisothermal bulk polymerization of multifunctional acrylates were studied by dynamic differential scanning calorimetry (DSC). Measurements were carried out for four straight-chain monomers, diethylene glycol diacrylate (DEGDA), triethylene glycol diacrylate (TEGDA), tetraethylene glycol diacrylate (TTGDA), and poly(ethylene glycol)diacrylate (PEGDA) (mol. wt. 600), to study the effect of the backbone chain length, atmosphere, and type of initiator on the crosslinking kinetics. 4,4′-Azobis(4-cyanovaleric acid) (1.0%, w/w) was used as a free-radical initiator. From the dynamic scanning of polymerization of DEGDA at five heating rates (2–30°C/min), the average heat of polymerization (ΔHp) was found to be 524.2 J/g. An activation energy of 108.8 kJ/mol and preexponential factor 5.34 × 1012 s?1 were obtained from the Arrhenius plot, In dα/dt. The rate of polymerization was found manyfold greater at 20–60% conversion than at the initial stage (2–8% conversion). Polymerization was studied under both nitrogen and air atmosphere. The results corresponded well with the theory of oxygen inhibition. Different types of initiators, e.g., 4,4′-azobis(4-cyanovaleric acid) (ABCVA), 2,2′-azobisisobutyronitrile (AIBN), and benzoyl peroxide (BPO) were used for polymerization and ABCVA was found to be the most efficient among all. © 1995 John Wiley & Sons, Inc. 相似文献