全文获取类型
收费全文 | 1128篇 |
免费 | 146篇 |
国内免费 | 24篇 |
专业分类
电工技术 | 9篇 |
综合类 | 25篇 |
化学工业 | 51篇 |
金属工艺 | 134篇 |
机械仪表 | 269篇 |
建筑科学 | 19篇 |
矿业工程 | 10篇 |
能源动力 | 112篇 |
轻工业 | 3篇 |
水利工程 | 1篇 |
武器工业 | 2篇 |
无线电 | 45篇 |
一般工业技术 | 385篇 |
冶金工业 | 19篇 |
原子能技术 | 2篇 |
自动化技术 | 212篇 |
出版年
2024年 | 1篇 |
2023年 | 17篇 |
2022年 | 51篇 |
2021年 | 65篇 |
2020年 | 81篇 |
2019年 | 68篇 |
2018年 | 60篇 |
2017年 | 68篇 |
2016年 | 65篇 |
2015年 | 98篇 |
2014年 | 96篇 |
2013年 | 122篇 |
2012年 | 119篇 |
2011年 | 100篇 |
2010年 | 62篇 |
2009年 | 39篇 |
2008年 | 12篇 |
2007年 | 21篇 |
2006年 | 13篇 |
2005年 | 24篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 24篇 |
2001年 | 18篇 |
2000年 | 12篇 |
1999年 | 11篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 2篇 |
排序方式: 共有1298条查询结果,搜索用时 15 毫秒
61.
《Journal of the European Ceramic Society》2022,42(1):296-305
Bubble formation and removal within the molten glass is an important issue in glass industry. Various sources of bubbles have been identified in glass manufacturing: decomposition of the glass components, air trapping, oxidation/reduction reactions, precipitation resulting from insufficient refining, etc. It has been demonstrated in a previous paper that the blistering phenomenon at the interface between a molten glass and a zirconia-based refractory can be ascribed to the oxygen semipermeability through the zirconia phase. The objective of this study is to clarify the role of temperature on the blistering process, and especially, below and above the phase transition temperature of zirconia (monoclinic/tetragonal transformation) and to evaluate the role of zirconia doping on the blistering level. The influence of the kinetics of the surface processes at the glass/refractory interface is emphasized. Quantitative measurement of the slight blistering ascribed to the so-called “redox shock” is also given. 相似文献
62.
《Journal of the European Ceramic Society》2022,42(1):30-42
The oxidation resistance of ultra-high-temperature ceramic material (HfB2-30 vol%SiC)-2 vol%rGO (rGO: reduced graphene oxide) under long-term exposure (2000s) to a supersonic air flow has been studied. The ceramics were obtained by reactive hot pressing of HfB2-(SiO2-C)-rGO composite powder at a temperature of 1800°C (pressure 30 MPa, holding time 15 min, Ar). The surface temperature of graphene-modified ceramics under the influence of heating by high-enthalpy air flow (heat flow q reached 779 W·cm–2) did not exceed 1700°C, which is 650–700°C less than for the HfB2-30 vol%SiC baseline ceramics. This may be related to an increase in the efficiency of heat transfer from the sample to the water-cooled module, due to the higher thermal conductivity of the rGO-containing material. Thereby, a decrease in the material degradation degree has been noted, i.e. decrease in the recession rate and decrease in the total thickness of the oxidised ceramic layer by tenth. The peculiarities of the oxidised surface and near-surface region microstructure upon aerodynamic heating of the graphene-modified ceramic material, have been shown. 相似文献
63.
Insight into t->m transition of MW treated 3Y-PSZ ceramics by grazing incidence X-ray diffraction
《Journal of the European Ceramic Society》2022,42(1):227-237
The influence of a microwave hybrid heat treatment (MHH) on the surface and in-depth mineralogical transformation of pre-sintered 3Y-PSZ was investigated. 3Y-PSZ samples were prepared by slip casting and sintered by conventional firing (1270 °C). Then, different MHH treatments from 5 to 15 min. at 1200 °C were applied to obtain a fully stabilized 3Y-TZP. The monoclinic fraction depth profiles in the first micrometres (up to 5) of thickness were investigated by means of the grazing incident X-ray diffraction technique (GIXRD). A good sintering degree with practically nil closed porosity and grain growth was achieved after MHH of 15 min. MHH increases the tetragonal phase content both in the surface and in-depth, reducing completely the monoclinic phase shell typically found after conventional sintering. A new parabolic model is proposed for the convoluted monoclinic fraction depth profile, which through the value of its horizontal asymptote allows the determination of the monoclinic shell thickness. 相似文献
64.
65.
《Carbon》2014
Future composite applications will require dimensional control of graphene microsheets (GMs) to optimize structure and performance. However, realizing this goal in a high yield, cost-effective manner is presently a major challenge. We here demonstrate a simple approach to prepare single-layer GMs with a yield of >90% by one-step hydrothermal treatment of graphene oxide sheets. The addition of poly(vinyl pyrrolidone) is critical for producing single-layer GMs with specific sheet sizes and does not significantly affect the hydrothermal cutting of GMs. Using hydrothermal treatment under different conditions, the lateral dimensions of the single-layer GMs can be tuned to yield specific surface areas over a range of ∼3.5 orders of magnitude, from 30 to 9 × 10−3 μm2. 相似文献
66.
Flow passing a vehicle may lead to the increase of the cabin interior noise level through a variety of mechanisms. These mechanisms include vibrations caused by aerodynamic excitations and reradiation from the glass panels, exterior noise trans-mitted and leaked through door seals including gaps and glass edge, and transmission of airborne noise generated by the interaction of flow with body panels. It is of vital importance to predict both the flow fields and the acoustic sources around the ve-hicle to accurately assess the impact of wind induced noise inside the cabin. In the present study, an unstructured segregated finite volume model was used to calculate the flow fields in which a hexahedron grid is used to simplify the vehicle geometry.A large eddy simulation coupled with a wall function model was applied to predict the exterior transient flow fields. The mean flow quantities were thus calculated along the symmetry plane and the vehicle’s side windows. A coupled FEM/BEM method was used to compute the vehicle’s interior noise level. The total contribution of the interior noise level due to the body panels of the vehicle was subsequently analyzed. 相似文献
67.
《Carbon》2014
The mechanical properties of graphene may be strongly affected by defects. In our work, the effects of the orientation and tilting angles of Stone–Thrower–Wales (STW, 5-7-7-5) defects on the mechanical properties of graphene have been investigated based on molecular dynamics simulations. When there is one centred STW defect including STW-1 defect and STW-2 defect, our study reveals that the orientation with respect to the chirality governs the mechanical properties of graphene. For STW-1 defective graphene, the strength of the armchair direction is much lower than that of zigzag direction. While the circumstance for STW-2 defective graphene is opposite, the strength of the armchair direction is much higher than the strength of the zigzag direction. Furthermore, when there is more than one STW defect, the mechanical properties of graphene depends on the tilting angle of STW defects. The breaking strength of graphene decreases with the increasing tilting angle. Our present work could provide significant insights into the effect of STW defects on the mechanical properties of graphene. 相似文献
68.
As an alternative method of empirical mode decomposition (EMD), the empirical Wavelet transform (EWT) method was proposed to realize the signal decomposition by constructing an adaptive filter bank. Though the EWT method has been demonstrated its effectiveness in some applications, it becomes invalid in analyzing some noisy and non-stationary signals due to its improper segmentation in the frequency domain. In this paper, an enhanced empirical wavelet transform method is proposed. This method takes advantage of the waveform in the frequency domain of a signal to eliminate drawbacks of the EWT method in the spectrum segmentation. It modifies the segmentation algorithm by adopting the envelope approach based on the order statistics filter (OSF) and applying criteria to pick out useful peaks. With these measures, the proposed method obtains a perfect segmentation in decomposing noisy and non-stationary signals. Furthermore, simulated and experimental signals are used to verify the effectiveness of the proposed method. 相似文献
69.
A. Ajdari P. Canavan H. Nayeb-Hashemi G. Warner 《Materials Science and Engineering: A》2009,499(1-2):434-439
Functionally graded cellular structures such as bio-inspired functionally graded materials for manufacturing implants or bone replacement, are a class of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. A gradual increase in cell size distribution, can impart many improved properties which may not be achieved by having a uniform cellular structure.The material properties of functionally graded cellular structures as a function of density gradient have not been previously addressed within the literature. In this study, the finite element method is used to investigate the compressive uniaxial and biaxial behavior of functionally graded Voronoi structures. Furthermore, the effect of missing cell walls on its overall mechanical (elastic, plastic, and creep) properties is investigated.The finite element analysis showed that the overall effective elastic modulus and yield strength of structures increased by increasing the density gradient. However, the overall elastic modulus of functionally graded structures was more sensitive to density gradient than the overall yield strength. The study also showed that the functionally graded structures with different density gradient had similar sensitivity to random missing cell walls. Creep analysis suggested that the structures with higher density gradient had lower steady-state creep rate compared to that of structures with lower density gradient. 相似文献
70.
This study presents a new type of cellular material that is simpler to make than conventional honeycombs and foams, while possessing many of the exceptional mechanical properties that make foams and honeycombs valuable as low density structural materials. The stochastic honeycombs had relative densities ranging from 7% to 13% with compressive strengths between 1 and 3 MPa, and compressive stiffnesses between 60 and 130 MPa. These values are comparable to those seen for commercial polypropylene honeycombs and significantly higher than those of commercial polypropylene foams. Rigid sandwich panels could be fabricated by reinforcing the stochastic honeycomb cores with external polypropylene face sheets. The panels could be assembled without adhesives, creating a rigid sandwich made entirely of a single material. 相似文献