全文获取类型
收费全文 | 506篇 |
免费 | 30篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 105篇 |
金属工艺 | 38篇 |
机械仪表 | 17篇 |
建筑科学 | 6篇 |
矿业工程 | 4篇 |
能源动力 | 26篇 |
轻工业 | 12篇 |
石油天然气 | 3篇 |
无线电 | 55篇 |
一般工业技术 | 141篇 |
冶金工业 | 27篇 |
自动化技术 | 93篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 13篇 |
2021年 | 29篇 |
2020年 | 21篇 |
2019年 | 18篇 |
2018年 | 26篇 |
2017年 | 22篇 |
2016年 | 24篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 40篇 |
2012年 | 37篇 |
2011年 | 42篇 |
2010年 | 21篇 |
2009年 | 31篇 |
2008年 | 33篇 |
2007年 | 19篇 |
2006年 | 20篇 |
2005年 | 17篇 |
2004年 | 12篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有536条查询结果,搜索用时 343 毫秒
61.
Molecular dynamics simulations of thin films and bulk melts of model self-associating polymers have been performed in order to gain understanding of the influence of free surfaces on the morphology of these polymers. The self-associating polymers were represented by a simple bead-necklace model with attractive groups (stickers) at the chain ends (end-functionalized polymer) and in the chain interior (interior-functionalized polymer). The functionalized groups were found to form clusters in the melt whose size is representative of that found experimentally in many ionomer melts. While the size distribution and shape of the clusters in the thin films were found to be relatively unperturbed compared to their corresponding bulk melts, the morphology of the self-associating melts was found to be significantly perturbed by the free surfaces. Specifically, a strong depletion of stickers near the interface and the emergence of clearly defined layers of stickers parallel to the surface was observed. Increased bridging of clusters by the functionalized polymers was also observed near the free surface. We conclude that these effects can be associated with a high free energy for stickers in the low-density interfacial regime: stickers prefer to be in the higher-density interior of the film where relatively unperturbed sticker clusters can form. 相似文献
62.
In this paper, a fault direction estimation algorithm is proposed for a double-circuit line with thyristor controlled series capacitor (TCSC) using principal component analysis (PCA)-based technique. In case of PCA, an orthogonal transformation is used to convert correlated variables into linearly uncorrelated variables called principal components. Fault in such a compensated line leads to voltage inversion, current inversion, and subsynchronous resonance situations, which affect the performance of the conventional direction estimation process. Transients associated with metal oxide varistor (MOV) operation and control action associated with TCSC, further modulate equivalent impedance of TCSC and MOV combination. In the proposed approach, PCA of angles between positive and negative sequence components of voltage current has been carried out to extract the pattern and to declare the fault direction accurately. The double-circuit line with TCSC is simulated using PSCAD/EMTDC software. The performance of the proposed technique is tested for numerous test cases, and it was found to be accurate. 相似文献
63.
The present study aims at studying ageing characteristics of conventional bitumen, polymer modified bitumen (PMB) and warm mix asphalt (WMA) by using FTIR. Results of obtained FTIR spectrum were quantified by calculating different indices and finally based on these indices ageing index of the binders for short- and long-term ageing were calculated. Results showed ageing increased amount of complex and high molecular weight components of the binders. PMB was found to have greater ageing resistance than conventional asphalt binders. In case of WMA, results found to be inconclusive, requiring further investigation. 相似文献
64.
Joseph A. Santa Maria Benjamin F. Schultz J. B. Ferguson Nikhil Gupta Pradeep K. Rohatgi 《Journal of Materials Science》2014,49(3):1267-1278
Metal matrix syntactic foams are promising materials for energy absorption; however, few studies have examined the effects of hollow sphere dimensions and foam microstructure on the quasi-static and high strain rate properties of the resulting foam. Aluminum alloy A380 syntactic foams containing Al2O3 hollow spheres sorted by size and size range were synthesized by a sub-atmospheric pressure infiltration technique. The resulting samples were tested in compression at strain rates ranging from 10?3 s?1 using a conventional load frame to 1720 s?1 using a Split Hopkinson Pressure-bar test apparatus. It is shown that the quasi-static compressive stress–strain curves exhibit distinct deformation events corresponding to initial failure of the foam at the critical resolved shear stress and subsequent failures and densification events until the foam is deformed to full density. The peak strength, plateau strength, and toughness of the foam increases with increasing hollow sphere wall thickness to diameter (t/D) ratio. Since t/D was found to increase with decreasing hollow sphere diameter, the foams produced with smaller spheres showed improved performance. The compressive properties did not show measurable strain rate dependence. 相似文献
65.
66.
67.
68.
Cl‐Doped ZnO Nanowire Arrays on 3D Graphene Foam with Highly Efficient Field Emission and Photocatalytic Properties 下载免费PDF全文
Dali Shao Jian Gao Guoqing Xin Yiping Wang Lu Li Jian Shi Jie Lian Nikhil Koratkar Shayla Sawyer 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(36):4785-4792
An environmentally friendly, low‐cost, and large‐scale method is developed for fabrication of Cl‐doped ZnO nanowire arrays (NWAs) on 3D graphene foam (Cl‐ZnO NWAs/GF), and investigates its applications as a highly efficient field emitter and photocatalyst. The introduction of Cl‐dopant in ZnO increases free electrons in the conduction band of ZnO and also leads to the rough surface of ZnO NWAs, which greatly improves the field emission properties of the Cl‐ZnO NWAs/GF. The Cl‐ZnO NWAs/GF demonstrates a low turn‐on field (≈1.6 V μm−1), a high field enhancement factor (≈12844), and excellent field emission stability. Also, the Cl‐ZnO NWAs/GF shows high photocatalytic efficiency under UV irradiation, enabling photodegradation of organic dyes such as RhB within ≈75 min, with excellent recyclability. The excellent photocatalytic performance of the Cl‐ZnO NWAs/GF originates from the highly efficient charge separation efficiency at the heterointerface of Cl‐ZnO and GF, as well as improved electron transport efficiency due to the doping of Cl. These results open up new possibilities of using Cl‐ZnO and graphene‐based hybrid nanostructures for various functional devices. 相似文献
69.
70.