全文获取类型
收费全文 | 3806篇 |
免费 | 229篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 60篇 |
综合类 | 67篇 |
化学工业 | 834篇 |
金属工艺 | 165篇 |
机械仪表 | 151篇 |
建筑科学 | 202篇 |
矿业工程 | 42篇 |
能源动力 | 250篇 |
轻工业 | 531篇 |
水利工程 | 22篇 |
石油天然气 | 38篇 |
武器工业 | 2篇 |
无线电 | 205篇 |
一般工业技术 | 574篇 |
冶金工业 | 349篇 |
原子能技术 | 48篇 |
自动化技术 | 530篇 |
出版年
2024年 | 20篇 |
2023年 | 44篇 |
2022年 | 76篇 |
2021年 | 108篇 |
2020年 | 137篇 |
2019年 | 119篇 |
2018年 | 165篇 |
2017年 | 146篇 |
2016年 | 175篇 |
2015年 | 102篇 |
2014年 | 170篇 |
2013年 | 391篇 |
2012年 | 202篇 |
2011年 | 208篇 |
2010年 | 174篇 |
2009年 | 221篇 |
2008年 | 174篇 |
2007年 | 162篇 |
2006年 | 127篇 |
2005年 | 80篇 |
2004年 | 95篇 |
2003年 | 115篇 |
2002年 | 163篇 |
2001年 | 126篇 |
2000年 | 66篇 |
1999年 | 55篇 |
1998年 | 131篇 |
1997年 | 69篇 |
1996年 | 52篇 |
1995年 | 28篇 |
1994年 | 28篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1965年 | 3篇 |
排序方式: 共有4070条查询结果,搜索用时 31 毫秒
941.
Combined Cu‐CeO2 /YSZ and Ni/YSZ dual layer anode structures for direct methane solid oxide fuel cells
下载免费PDF全文
![点击此处可从《国际能源研究杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this study, a conventional Ni/yttria‐stabilized zirconia (YSZ) anode and a new Cu‐CeO2‐YSZ anode structure were assembled in an attempt to combine the advantages of both structures for use in direct methane solid oxide fuel cells. For this purpose, only a limited region (≤20 μm) of NiO/YSZ was deposited at the boundary of the electrolyte to benefit from the superior catalytic activity of Ni in the cells, while the rest of the cell benefited from the Cu‐CeO2‐YSZ anode structure, which does not cause cracking reactions. First, the effects of different pore formers on the anode skeleton, as well as the interactions of the Ni‐Cu species in the anode skeleton, are discussed. Then, the NiO/YSZ‐interlayer‐containing button cells with different thicknesses (≤20) and different ratios of NiO (40 wt%, 50 wt%, and 60 wt%) were studied. After the examination of the cells, 2 model cells with outstanding performance and 2 additional internal reference cells, conventional Ni/YSZ and Cu‐CeO2‐YSZ, were scaled up, and performance analysis and long‐term stability studies were carried out. As a result, for solid oxide fuel cells with increased carbonization resistance (around 6% performance loss due to carbonization after 100‐hour stability testing) and 86.1% of the initial performance of the conventional Ni/YSZ anode structure, a 15‐μm‐thick 40 wt% NiO/60 wt% YSZ interlayer with a dual layer anode structure is proposed. 相似文献
942.
943.
Mehmet Kiliç Yaşar Karabul Zeynep Güven Özdemir Seda Erdönmez Ayşe Evrim Bulgurcuoğlu Serço Serkis Yeşilkaya Mustafa Okutan Orhan İçelli 《Bulletin of Materials Science》2018,41(2):52
The main aim of this study is to produce added polypyrrole (PPy) borax composites with high dielectric properties for technological applications. For this purpose, PPy–borax composites with different borax concentrations varying from 10 to 50 wt% have been prepared. To reveal their structural and morphological attributes, the composites have been characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. The real and imaginary parts of complex dielectric function, the imaginary component of complex electrical modulus and ac conductivity have been investigated at room temperature as a function of frequency in the range 100 Hz–15 MHz. It has been found that addition of borax increases the dielectric constant of pure PPy. In this respect, PPy–borax composites with the highest dielectric constant at low frequency may be utilized in charge storing devices. On the other hand, the dielectric loss is also very high in low-frequency region for the composites with high borax content. Exploiting this property, the material may also be used in decoupling capacitor applications. The relaxation mechanisms of the samples have also been determined as non-Debye type. The Nyquist curves of the samples have been analysed for calculating the grain and grain boundary resistance and capacitance values. In conclusion, borax has a promising potential to be used as a cheap and effective filler for improving the dielectric properties of PPy polymer. 相似文献
944.
In this note we give an overview of the first- and second-order collaboration network reflected by Eugene Garfield’s publications in scientific journals. Although he had only a quite limited number of co-authors and co-publications, his co-authors’ own collaboration networks generate a large world-wide and multidisciplinary coverage. The classical model of co-authorship network is the Erd?s network with the Erd?s Number indicating the shortest co-authorship path through which an author is connected with Paul Erd?s. The two networks, generated by Erd?s and Garfield, respectively, show completely different patterns and characteristics but illustrate the ways how ideas of great scholars and pioneers disseminate and influence the respective scientific communities. 相似文献
945.
946.
947.
Marco Castriota Enzo Cazzanelli Daniela Pacilè Luigi Papagno Çağlar O. Girit Jannik C. Meyer Alex Zettl Marco Giarola Gino Mariotto 《Diamond and Related Materials》2010,19(5-6):608-613
A micro-Raman investigation was carried out on several flakes of monolayer (1 L) graphene obtained by the micro-mechanical exfoliation technique and, then, put on a c-Si wafer coated by a SiO2 thin film. Some of the 1 L zones show a remarkable dispersion of the 2D-overtone wavenumber as a function of the position within the graphene sheet, and, in some case, a significant broadening of the E2g phonon (G band) is associated to this wavenumber shift of 2D-band. Such effects were studied, in particular, for a 1 L zone characterized by a rather strong lattice disorder, as revealed by the strong D/G band intensity ratio, and for other zones quite ordered, showing a vanishing intensity of the D band. Moreover, by moving along different directions within 1 L graphene sheets, different trends for 2D wavenumber and E2g phonon bandwidth vs. position were observed. All these reported behaviours are explained in terms of different distributions of intrinsic uniaxial strain occurring within the 1 L graphene sheets. 相似文献
948.
949.
The aim of this study is to evaluate the effect of different cavity disinfectants on shear bond strength. In this study, 60 caries-free human molar teeth were used. Smooth dentin surfaces were revealed by cutting occlusal enamel and a standard smear layer was obtained by using 600-grid sandpaper. Specimens were randomly assigned to four groups according to the disinfectant used: Group 1: Control (no disinfectant); Group 2: Ozone; Group 3: Chlorhexidine, Group 4: Boric acid. Specimens were bonded using S3 Plus Bond and the composite buildups were created by using composite resin according to the manufacturer’s instructions. After specimens were kept for 24 h, at 37 °C in distilled water, the shear bond strength test was measured with a universal test machine. The highest bond strength values were observed in the control group. The bond strength was significantly lower in the chlorhexidine, and boric acid-treated groups than it was in the control group (respectively, p = 0.046 and p = 0.028); however, no significant difference in the bond strength was observed between the ozone group and the control group (p = 0.444). The ozone group was detected as having the best shear bond strength values in groups which were applied to cavity disinfectants. 相似文献
950.
İbrahim Uslu Arda Aytimur Mustafa Kemal Öztürk Serhat Koçyiğit 《Ceramics International》2012,38(6):4943-4951
In this study, a new method to synthesize neodymium doped ceria ceramic nanopowders by the electrospinning of the hybrid polymers solution of their composite precursor was put forward. Calcined and sintered nanopowders were characterized by FT-IR, XRD, BET, SEM, and AFM techniques. According to the XRD analysis, the obtained powders are single phase and independent of the dopant concentration in the range investigated. The crystallite sizes were calculated using Scherrer equation. Moreover, lattice parameters, dislocation densities and microstrain values were calculated. BET results show that the increase of the neodymium doped content decrease the surface area of the composite powders, confirming the highly ordered micro and mesostructure. SEM and AFM results show that the samples have spherical grains. According to the surface roughness measurements, the increase in the amount of neodymium and the decrease in the amount of cerium decreased the surface roughness. 相似文献