全文获取类型
收费全文 | 14649篇 |
免费 | 1198篇 |
国内免费 | 742篇 |
专业分类
电工技术 | 329篇 |
综合类 | 511篇 |
化学工业 | 3382篇 |
金属工艺 | 1704篇 |
机械仪表 | 441篇 |
建筑科学 | 33篇 |
矿业工程 | 39篇 |
能源动力 | 584篇 |
轻工业 | 604篇 |
水利工程 | 2篇 |
石油天然气 | 37篇 |
武器工业 | 30篇 |
无线电 | 2563篇 |
一般工业技术 | 5900篇 |
冶金工业 | 140篇 |
原子能技术 | 133篇 |
自动化技术 | 157篇 |
出版年
2024年 | 21篇 |
2023年 | 186篇 |
2022年 | 133篇 |
2021年 | 295篇 |
2020年 | 289篇 |
2019年 | 302篇 |
2018年 | 358篇 |
2017年 | 456篇 |
2016年 | 433篇 |
2015年 | 486篇 |
2014年 | 624篇 |
2013年 | 937篇 |
2012年 | 939篇 |
2011年 | 1388篇 |
2010年 | 1034篇 |
2009年 | 1044篇 |
2008年 | 957篇 |
2007年 | 1049篇 |
2006年 | 908篇 |
2005年 | 666篇 |
2004年 | 683篇 |
2003年 | 575篇 |
2002年 | 524篇 |
2001年 | 393篇 |
2000年 | 321篇 |
1999年 | 224篇 |
1998年 | 237篇 |
1997年 | 210篇 |
1996年 | 136篇 |
1995年 | 121篇 |
1994年 | 109篇 |
1993年 | 89篇 |
1992年 | 97篇 |
1991年 | 98篇 |
1990年 | 62篇 |
1989年 | 35篇 |
1988年 | 30篇 |
1987年 | 22篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 9篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Pauline Hibon Heinz von Seggern Hsin-Rong Tseng Christoph Leonhard Manuel Hamburger Gaëlle Béalle 《应用聚合物科学杂志》2020,137(29):48895
Interface control remains a top challenge of solution-processed organic light emitting diodes (OLED) stacks since the device performance heavily relies on it. Film stability of an inkjet deposited and crosslinked layer against subsequent exposure to a suitable inkjet printed solvent has been investigated. Impact of processing solvent (solvent used to prepare the polymer layer) on solution-cast thin film properties has already been shown for polymer films. To our knowledge, this study is the first one analyzing thin films stability against solvent exposure using technology relevant materials processed via inkjet printing (IJP). The outcome of this research showed that the stability of the crosslinked films is affected by the solvent used for ink formulation. These findings are of great interest for multilayered semiconductors devices, such as OLEDs, field-effect transistors and dye-sensitized solar cells. Differential scanning calorimetry (DSC) was used to quantify the efficiency of the polymer crosslinking reaction in pure powder and in thin films, as processed from different solvents. Crosslinking efficiency measured by DSC correlated well with the deformation induced by the solvent and observed on layer surfaces. The interaction in solution between polymer and solvent has also been evaluated to explain its impact on thin film stability against successive solvent printing. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48895. 相似文献
72.
《Ceramics International》2020,46(8):11978-11987
The columnar structure and its formation process have a significant effect on the electrical properties of Al-doped ZnO (AZO) thin film in-situ deposited at room temperature by magnetron sputtering method. The influences of RF power on the formation of the columnar structure and its regular pattern were systematically investigated. The RF power varied from 120 W to 240 W. The best quality AZO sample with the sheet resistance of 6.07 Ω/sq and average transmittance of 83.2% was obtained at 210 W (for 30 min). The analysis of crosses section images indicated that the columnar structure appeared earlier at higher RF power. The thickness at which the columnar structure began to appear didn't fluctuate at a fixed value. Furthermore, high RF power relatively contributed to reduce the thickness. The Drude's model was used for examining the correlation between optical and electrical behaviors, and the theoretical results of electrical properties were well matched with the experimental data. According to the XRD results and XPS analysis, the appearance of Al2O3 may exert a significant influence on the deterioration in electrical properties of the sample deposited at 240 W. 相似文献
73.
This paper presents an analytical method to study the effect of inclusions in piezoelectric materials on the creep rate. The driven force for the creep rate of piezoelectric materials with inclusion is from diffusional mass transport along the inclusion interface. The results show that the creep rate of piezoelectric materials containing the rigid inclusion with the shape parameter m = 0.8 appears at the minimum, and the effect of inclusion volume fraction on the creep rate of piezoelectric materials with soft inclusion becomes the smaller and smaller, as the stiffness of soft inclusion decreases. Thus, the effect of inclusion on creep characteristics can be improved by controlling the material property, the sizes, shapes, and volume ratio of inclusions. 相似文献
74.
We investigate heterogeneous oxidation kinetics of monolayer‐thick, surface‐sorbed organics, namely di‐n‐octyl phthalate (DnOP) and palmitic acid (PA), with gas‐phase OH. The pseudo‐first order rate constants for organic loss at OH concentrations of 1.6 × 108 molecules/cm3 are: (2.3 ± 0.1) × 10?4 to (4.8 ± 0.8) × 10?4 s?1, and (1.3 ± 0.5) × 10?4 s?1 for DnOP and PA, respectively. Films developed in indoor office environments over a few weeks are also oxidized using the same OH concentration. Heterogeneous decay rate constants of mass signals from these films, attributed to phthalates (MW = 390.6) and to PA, are similar to those for the single‐component films, ie, (1.9 ± 0.4) × 10?4 to (3.4 ± 0.5) × 10?4 s?1, and (1.1 ± 0.4) × 10?4 s?1, respectively. These results suggest that the lifetimes for OH heterogeneous oxidation of monolayer‐thick indoor organic films will be on the timescale of weeks to months. To support this argument, we present the first analysis of the mass transfer processes that occur when short‐lived gas‐phase molecules, such as OH, are taken up by reactive indoor surfaces. Due to rapid chemical production, the diffusion limitation to mass transfer is less important for short‐lived molecules than for molecules with little chemical production, such as ozone. 相似文献
75.
Nicolle Dal’Acqua Ana Claudia Rangel Faria Mário César Vebber Hernane da Silva Barud Marcelo Giovanela Giovanna Machado Janaina da Silva Crespo 《International Journal of Hydrogen Energy》2018,43(33):15794-15806
The issues related to renewable energy sources is a matter of great worldwide appeal due to the increasing energy demand, instability in oil prices and environmental problems. In this context, the purpose of this study was to prepare self-assembled films of polyallylamine hydrochloride and poly (acrylic acid) supported onto bacterial cellulose membranes by a layer-by-layer approach with titanium dioxide (TiO2) nanoparticles and different concentrations of gold for application in hydrogen gas (H2) production by photocatalysis. The influence of the gold concentration and the presence and size of the gold nanoparticles (Au NPs), as well as the surface and thickness of the films on H2 production was investigated. The results showed that the film, prepared with a lower concentration of gold, presented the smallest Au NPs and, therefore, greater contact with the TiO2 nanoparticle surfaces, producing more H2. By analyzing the variation in all the experimental parameters used in the preparation of the films, it can be concluded that the best H2 production achieved was 29.12 μmol h?1 cm2. 相似文献
76.
首先从碳基固体润滑薄膜的应用需求与成本效益出发,探讨了研究碳基固体润滑薄膜的迫切要求和重要意义,然后对类金刚石(DLC)薄膜、类富勒烯(FLC)薄膜及石墨烯薄膜三类最常用的碳基固体润滑薄膜的研究现状进行了较详细的介绍。其中,重点介绍了DLC薄膜的三种减摩抗磨机理,探讨了掺杂元素改性对DLC薄膜硬度、摩擦系数和磨损率等多个方面的影响,并指出外部因素(基体材料、过渡层和应用环境等)对DLC薄膜性能的重要作用。探讨了掺氢、掺氟和掺氮对FLC薄膜构性转变和摩擦学性能的影响。总体来说,氟掺杂导致FLC结构变化,并显著改变薄膜硬度;掺氮会诱导类富勒烯微结构的增加;掺氢FLC薄膜热处理后可达到超润滑状态。总结了石墨烯薄膜制备工艺的发展、石墨烯基复合薄膜的摩擦学性能和石墨烯薄膜在不同基体材料的应用。最后,指出了碳基润滑薄膜领域亟待解决的关键难题,并对未来的研究方向做出了预测。 相似文献
77.
Dongsheng Song Heng-Jui Liu András Kovács Rafal E. Dunin-Borkowski Ying-Hao Chu Jing Zhu 《Journal of the American Ceramic Society》2020,103(4):2828-2834
Oxygen octahedral tilting has been recognized to strongly interact with spin, charge, orbital, and lattice degrees of freedom in perovskite oxides. Here, we observe a strain-driven stripe-like morphology of two supertetragonal (monoclinic Cc and Cm ) phases in the strained BiFeO3/LaAlO3 thin films. The two supertetragonal phases have a similar giant axial ratio but differences in oxygen pyramid tilting mode. Especially, the competition between polar instability and oxygen pyramid tilting is identified using atomically resolved scanning transmission electron microscopy, leading to the polarization rotation across the phase boundary. In addition, microtwins are observed in the Cc phase. Our findings provide new insights of the coupling between ferroelectric polarization and oxygen pyramid tilting in oxide thin films and will help to design novel phase morphology with desirable ferroelectric polarization and properties for new applications in perovskite oxides. 相似文献
78.
79.
In the present study, a renewable resource-based plasticizer was synthesized by the lipase-catalyzed esterification reaction of furfuryl alcohol (FA) and castor oil fatty acid (COFA). The resultant ester (FA-COFA ester) was used as secondary plasticizers to the polyvinyl chloride (PVC) films. The PVC films were formulated using the combination of a conventional plasticizer di-butyl phthalate (DBP) and FA-COFA ester as a secondary plasticizer at different concentrations. Films were characterized by X-ray diffraction analysis, scanning electron microscopy, thermal analysis, mechanical performance, and migration stability. A biodegradability study of the PVC films showed increased degradability with increasing concentration of the FA-COFA ester in the PVC film. The study showed that ester of FA and COFA could be a substitute of DBP by as much as 80% of the total plasticizer with improved elongation and tensile properties, and such a kind of sustainable resource-based PVC blend films could be used as a good packaging material with biodegradable property. 相似文献
80.
A series of 16-layer polypropylene/flame retardant (PP/FR) film/foam composite structures were produced by microlayer coextrusion. A highly branched PP was used in the foam layers to increase strain hardening and cell stability, while the PP used in the film layers was a high shear viscosity grade to confine bubble growth. In addition to improved tensile properties, the PP/FR composite film/foams exhibited five times the compression modulus of PP/FR composite foams at each FR loading level. The thermal stabilities of the composites were investigated, exhibiting three step decompositions. The FR particles were effective in decreasing flammability by forming intumescent char. The PP/FR-film/foam-20 showed self-extinguishing behavior in a modified vertical burn test, while the PP/FR-foam-20 sample continued to burn. Cone calorimetry demonstrated that PP/FR film/foams had lower heat release than PP/FR foams due to the unique alternating film/foam structure of PP/FR film/foams. Scanning electron microscopy imaging of the residual chars from fire testing that the PP/FR composite film/foams showed a more continuous protective char surface when compared with PP/FR composite foams at each FR concentration. The combined data indicate that the formation of a surface film on top of a foam ensures a robust intumescent fire protective barrier for partly foamed materials and shows a new way toward lightweight materials with improved fire safety performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48552. 相似文献