全文获取类型
收费全文 | 4144篇 |
免费 | 214篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 48篇 |
综合类 | 1篇 |
化学工业 | 1193篇 |
金属工艺 | 85篇 |
机械仪表 | 124篇 |
建筑科学 | 133篇 |
矿业工程 | 23篇 |
能源动力 | 129篇 |
轻工业 | 471篇 |
水利工程 | 24篇 |
石油天然气 | 20篇 |
武器工业 | 1篇 |
无线电 | 306篇 |
一般工业技术 | 704篇 |
冶金工业 | 384篇 |
原子能技术 | 43篇 |
自动化技术 | 682篇 |
出版年
2024年 | 10篇 |
2023年 | 47篇 |
2022年 | 161篇 |
2021年 | 190篇 |
2020年 | 130篇 |
2019年 | 119篇 |
2018年 | 170篇 |
2017年 | 154篇 |
2016年 | 157篇 |
2015年 | 142篇 |
2014年 | 188篇 |
2013年 | 305篇 |
2012年 | 231篇 |
2011年 | 272篇 |
2010年 | 200篇 |
2009年 | 190篇 |
2008年 | 188篇 |
2007年 | 147篇 |
2006年 | 128篇 |
2005年 | 127篇 |
2004年 | 87篇 |
2003年 | 72篇 |
2002年 | 72篇 |
2001年 | 57篇 |
2000年 | 36篇 |
1999年 | 55篇 |
1998年 | 97篇 |
1997年 | 70篇 |
1996年 | 51篇 |
1995年 | 56篇 |
1994年 | 51篇 |
1993年 | 39篇 |
1992年 | 19篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 28篇 |
1986年 | 21篇 |
1985年 | 22篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 21篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1976年 | 17篇 |
1975年 | 12篇 |
1973年 | 15篇 |
排序方式: 共有4371条查询结果,搜索用时 15 毫秒
51.
如果效率和成本目标能够实现,薄膜晶体硅太阳能电池有潜力替代目前在光伏市场上占主导地位的多晶硅太阳能电池。 相似文献
52.
This paper presents a multimodal biometrie verification system based on the following hand features: palmprint, four digitprints and four fingerprints. The features are obtained using the Karhunen-Loève transform based approach, and information fusion at the matching-score level was applied. We experimented with different resolutions of the regions of interest, different numbers of features and several normalization and fusion techniques at the matching-score level. To increase the reliability of the system to spoof attacks we included an aliveness-detection module based on thermal images of the hand dor sa. The verification performance when using a system configuration with optimum parameters, i.e., resolution, number of features, normalization and fusion technique, showed an equal error rate (EER) of 0.0020%, which makes the system appropriate for the implementation of high-security biometric systems. 相似文献
53.
Liu Shuai Bai Weiling Srivastava Gautam Machado J. A. Tenreiro 《Mobile Networks and Applications》2020,25(4):1537-1547
Mobile Networks and Applications - The increment of communication technologies and the development of signal processing require efficient identification techniques for communication... 相似文献
54.
Kamat NP Robbins GP Rawson JS Therien MJ Dmochowski IJ Hammer DA 《Advanced functional materials》2010,20(16):2588-2596
Polymersomes are vesicles whose membranes are comprised of self-assembled block co-polymers. We recently showed that co-encapsulating conjugated multi-porphyrin dyes in a polymersome membrane with ferritin protein in the aqueous lumen confers photo-lability to the polymersome. In the present study, we illustrate that the photo-lability can be extended to vesicles containing dextran, an inert and inexpensive polysaccharide, as the luminal solute. Here we explore how structural features of the polymersome/porphyrin/dextran composite affect its photo-response. Increasing dextran molecular weight, decreasing block copolymer molecular weight, and altering fluorophore-membrane interactions results in increasing the photo-responsiveness of the polymersomes. Amphiphilic interactions of the luminal encapsulant with the membrane coupled with localized heat production in the hydrophobic bilayer likely cause differential thermal expansion in the membrane and the subsequent membrane rupture. This study suggests a general approach to impart photo-responsiveness to any biomimetic vesicle system without chemical modification, as well as a simple, bio-inert method for constructing photo-sensitive carriers for controlled release of encapsulants. 相似文献
55.
Dawei Di Heli Xu Ivan Perez‐Wurfl Martin A. Green Gavin Conibeer 《Progress in Photovoltaics: Research and Applications》2013,21(4):569-577
An all‐Si tandem solar cell has the potential to achieve high conversion efficiency at low cost. However, the selection and synthesis of candidate material remain challenging. In this work, we show that the conventional ‘Si quantum dots (Si QDs) in SiO2 matrix’ approach can lead to the formation of over‐sized Si nanocrystals especially when doped with phosphorous, making the size‐dependent quantum confinement less effective. Also, our investigation has shown that the high resistivity of this material has become the performance bottleneck of the solar cell. To resolve these matters, we propose a new design based on Si QDs embedded in a SiO2/Si3N4 hybrid matrix. By replacing the SiO2 tunnel barriers by the Si3N4 layers, the new material manages to constrain the growth of doped Si QDs effectively and enhances the apparent band gap, as shown in X‐ray diffraction, Raman, photoluminescence and optical spectroscopic measurements. Besides, electrical characterisation on Si QD/c‐Si heterointerface test structures indicates the new material possesses improved vertical carrier transport properties. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
56.
Yeshu Tan Jianrui Feng Haobo Dong Longxiang Liu Siyu Zhao Feili Lai Tianxi Liu Ying Bai Ivan P. Parkin Guanjie He 《Advanced functional materials》2023,33(4):2209967
Platinum (Pt) is regarded as a promising electrocatalyst for hydrogen evolution reaction (HER). However, its application in an alkaline medium is limited by the activation energy of water dissociation, diffusion of H+, and desorption of H*. Moreover, the formation of effective structures with a low Pt usage amount is still a challenge. Herein, guided by the simulation discovery that the edge effect can boost local electric field (LEF) of the electrocatalysts for faster proton diffusion, platinum nanocrystals on the edge of transition metal phosphide nanosheets are fabricated. The unique heterostructure with ultralow Pt amount delivered an outstanding HER performance in an alkaline medium with a small overpotential of 44.5 mV and excellent stability for 80 h at the current density of −10 mA cm−2. The mass activity of as-prepared electrocatalyst is 2.77 A mg−1Pt, which is 15 times higher than that of commercial Pt/C electrocatalysts (0.18 A mg−1Pt). The density function theory calculation revealed the efficient water dissociation, fast adsorption, and desorption of protons with hybrid structure. The study provides an innovative strategy to design unique nanostructures for boosting HER performances via achieving both synergistic effects from hybrid components and enhanced LEF from the structural edge effect. 相似文献
57.
58.
Hannah C. Nerl Anuj Pokle Lewys Jones Knut Müller‐Caspary Karel H. W. van den Bos Clive Downing Eoin K. McCarthy Nicolas Gauquelin Quentin M. Ramasse Ivan Lobato Dermot Daly Juan Carlos Idrobo Sandra Van Aert Gustaaf Van Tendeloo Stefano Sanvito Jonathan N. Coleman Clotilde S. Cucinotta Valeria Nicolosi 《Advanced functional materials》2019,29(37)
The fabrication of 2D systems for electronic devices is not straightforward, with top‐down low‐yield methods often employed leading to irregular nanostructures and lower quality devices. Here, a simple and reproducible method to trigger self‐assembly of arrays of high aspect‐ratio chiral copper heterostructures templated by the structural anisotropy in black phosphorus (BP) nanosheets is presented. Using quantitative atomic resolution aberration‐corrected scanning transmission electron microscopy imaging, in situ heating transmission electron microscopy and electron energy‐loss spectroscopy arrays of heterostructures forming at speeds exceeding 100 nm s?1 and displaying long‐range order over micrometers are observed. The controlled instigation of the self‐assembly of the Cu heterostructures embedded in BP is achieved using conventional electron beam lithography combined with site specific placement of Cu nanoparticles. Density functional theory calculations are used to investigate the atomic structure and suggest a metallic nature of the Cu heterostructures grown in BP. The findings of this new hybrid material with unique dimensionality, chirality, and metallic nature and its triggered self‐assembly open new and exciting opportunities for next generation, self‐assembling devices. 相似文献
59.
Solution Processing Route to Multifunctional Titania Thin Films: Highly Conductive and Photcatalytically Active Nb:TiO2 下载免费PDF全文
Davinder S. Bhachu Sanjayan Sathasivam Gopinathan Sankar David O. Scanlon Giannantonio Cibin Claire J. Carmalt Ivan P. Parkin Graeme W. Watson Salem M. Bawaked Abdullah Y. Obaid Shaeel Al‐Thabaiti Sulaiman N. Basahel 《Advanced functional materials》2014,24(32):5075-5085
This paper reports the synthesis of highly conductive niobium doped titanium dioxide (Nb:TiO2) films from the decomposition of Ti(OEt)4 with dopant quantities of Nb(OEt)5 by aerosol‐assisted chemical vapor deposition (AACVD). Doping Nb into the Ti sites results in n‐type conductivity, as determined by Hall effect measurements. The doped films display significantly improved electrical properties compared to pristine TiO2 films. For 5 at.% Nb in the films, the charge carrier concentration was 2 × 1021 cm?3 with a mobility of 2 cm2 V–1 s–1 . The corresponding sheet resistance is as low as 6.5 Ω sq–1 making the films suitable candidates for transparent conducting oxide (TCO) materials. This is, to the best of our knowledge, the lowest reported sheet resistance for Nb:TiO2 films synthesized by vapour deposition. The doped films are also blue in colour, with the intensity dependent on the Nb concentration in the films. A combination of synchrotron, laboratory and theoretical techniques confirmed niobium doping into the anatase TiO2 lattice. Computational methods also confirmed experimental results of both delocalized (Ti4+) and localized polaronic states (Ti3+) states. Additionally, the doped films also functioned as photocatalysts. Thus, Nb:TiO2 combines four functional properties (photocatalysis, electrical conductivity, optical transparency and blue colouration) within the same layer, making it a promising alternative to conventional TCO materials. 相似文献
60.
Petr Kovaricek Peter Nadazdy Eva Pluharova Alica Brunova Riyas Subair Karol Vegso Valentino Libero Pio Guerra Oleksandr Volochanskyi Martin Kalbac Alexander Krasnansky Pallavi Pandit Stephan Volker Roth Alexander Hinderhofer Eva Majkova Matej Jergel Jianjun Tian Frank Schreiber Peter Siffalovic 《Advanced functional materials》2021,31(13):2009007
2D hybrid organic–inorganic perovskites are valued in optoelectronic applications for their tunable bandgap and excellent moisture and irradiation stability. These properties stem from both the chemical composition and crystallinity of the layer formed. Defects in the lattice, impurities, and crystal grain boundaries generally introduce trap states and surface energy pinning, limiting the ultimate performance of the perovskite; hence, an in-depth understanding of the crystallization process is indispensable. Here, a kinetic and thermodynamic study of 2D perovskite layer crystallization on transparent conductive substrates are provided—fluorine-doped tin oxide and graphene. Due to markedly different surface structure and chemistry, the two substrates interact differently with the perovskite layer. A time-resolved grazing-incidence wide-angle X-ray scattering (GIWAXS) is used to monitor the crystallization on the two substrates. Molecular dynamics simulations are employed to explain the experimental data and to rationalize the perovskite layer formation. The findings assist substrate selection based on the required film morphology, revealing the structural dynamics during the crystallization process, thus helping to tackle the technological challenges of structure formation of 2D perovskites for optoelectronic devices. 相似文献