全文获取类型
收费全文 | 615篇 |
免费 | 42篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 189篇 |
金属工艺 | 15篇 |
机械仪表 | 16篇 |
建筑科学 | 30篇 |
能源动力 | 18篇 |
轻工业 | 60篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 72篇 |
一般工业技术 | 106篇 |
冶金工业 | 10篇 |
原子能技术 | 9篇 |
自动化技术 | 119篇 |
出版年
2024年 | 1篇 |
2023年 | 15篇 |
2022年 | 47篇 |
2021年 | 43篇 |
2020年 | 23篇 |
2019年 | 20篇 |
2018年 | 27篇 |
2017年 | 25篇 |
2016年 | 31篇 |
2015年 | 25篇 |
2014年 | 29篇 |
2013年 | 53篇 |
2012年 | 37篇 |
2011年 | 52篇 |
2010年 | 32篇 |
2009年 | 39篇 |
2008年 | 31篇 |
2007年 | 31篇 |
2006年 | 22篇 |
2005年 | 19篇 |
2004年 | 17篇 |
2003年 | 16篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有659条查询结果,搜索用时 31 毫秒
101.
Occurrence of variable levels of health‐promoting fruit compounds in horn‐shaped Italian sweet pepper varieties assessed by a comprehensive approach 下载免费PDF全文
102.
Gianluca Pietra Tiziana Bonifacino Davide Talamonti Giambattista Bonanno Alessandro Sale Lucia Galli Laura Baroncelli 《International journal of molecular sciences》2021,22(17)
Retinitis pigmentosa (RP) is a family of inherited disorders caused by the progressive degeneration of retinal photoreceptors. There is no cure for RP, but recent research advances have provided promising results from many clinical trials. All these therapeutic strategies are focused on preserving existing photoreceptors or substituting light-responsive elements. Vision recovery, however, strongly relies on the anatomical and functional integrity of the visual system beyond photoreceptors. Although the retinal structure and optic pathway are substantially preserved at least in early stages of RP, studies describing the visual cortex status are missing. Using a well-established mouse model of RP, we analyzed the response of visual cortical circuits to the progressive degeneration of photoreceptors. We demonstrated that the visual cortex goes through a transient and previously undescribed alteration in the local excitation/inhibition balance, with a net shift towards increased intracortical inhibition leading to improved filtering and decoding of corrupted visual inputs. These results suggest a compensatory action of the visual cortex that increases the range of residual visual sensitivity in RP. 相似文献
103.
104.
Gianluca Tozzi Qing-Hang Zhang Colin Lupton Jie Tong Teodolito Guillen Arne Ohrndorf Hans-Jurgen Christ 《Journal of materials science. Materials in medicine》2013,24(11):2509-2518
An open-cell metallic foam was employed as an analogue material for human trabecular bone to interface with polymethyl methacrylate (PMMA) bone cement to produce composite foam–cement interface specimens. The stress-displacement curves of the specimens were obtained experimentally under tension, shear, mixed tension and shear (mixed-mode), and step-wise compression loadings. In addition, under step-wise compression, an image-guided failure assessment (IGFA) was used to monitor the evolution of micro-damage of the interface. Microcomputed tomography (µCT) images were used to build a subject-specific model, which was then used to perform finite element (FE) analysis under tension, shear and compression. For tension–shear loading conditions, the strengths of the interface specimens were found to increase with the increase of the loading angle reaching the maximum under shear loading condition, and the results compare reasonably well with those from bone–cement interface. Under compression, however, the mechanical strength measured from the foam–cement interface is much lower than that from bone–cement interface. Furthermore, load transfer between the foam and the cement appears to be poor under both tension and compression, hence the use of the foam should be discouraged as a bone analogue material for cement fixation studies in joint replacements. 相似文献
105.
Maria Losurdo Pio Capezzuto Giovanni Bruno Francesco Babudri Antonio Cardone Gianluca M. Farinola Francesco Naso Michael Büchel 《Polymer》2008,49(19):4133-4140
This study is an investigation on the interplay between supramolecular organization and optical properties of thin films of conjugated polymers with fluorinated vinylene units such as poly[2-(2-ethylhexyloxy)-5-methoxy]-1,4-phenylenedifluorovinylene (MEH-PPDFV) and poly(2-methoxy-5-propyloxysulfonatephenylenedifluorovinylene) (MPS-PPDFV), which are both PPV polymers with fluorinated double bonds with alkoxy chains in the 2 and 5 positions. MEH-PPDFV is the fluorinated version of the widely investigated MEH-PPV, and MPS-PPDFV is characterized by the presence of ionic alkoxy side chains. This interplay is elucidated exploiting atomic force microscopy, spectroscopic ellipsometry and photoluminescence to obtain complementary information. It is demonstrated that the presence of F-atoms in the vinylene units of the MEH-PPDFV yields a blue optical band gap with the maximum of the fundamental HOMO-LUMO transition and of the room temperature photoluminescence at 3.74 eV (331 nm) and at 2.71 eV (458 nm), respectively. The blue-absorption and emission in the thin films are ascribed to the fact that fluorine atoms on the vinylene units prevent π-stacking of polymeric chains. Furthermore, the dependence of morphology, anisotropy in optical properties and photoluminescence properties of films on deposition methodology is also discussed. MEH-PPDFV also emits homogeneous blue-greenish electroluminescence at 2.46 eV (504 nm). 相似文献
106.
Swillens A De Santis G Degroote J Lovstakken L Vierendeels J Segers P 《IEEE transactions on medical imaging》2012,31(1):131-139
We used a multiphysics model to assess the accuracy of carotid strain estimates derived from a 1-D ultrasonic wall tracking algorithm. The presented tool integrates fluid-structure interaction (FSI) simulations with an ultrasound simulator (Field II), which allows comparison of the ultrasound (US) images with a ground truth. Field II represents tissue as random points on which US waves reflect and whose position can be updated based on the flow field and vessel wall deformation from FSI. We simulated the RF-signal of a patient-specific carotid bifurcation, including the blood pool as well as the vessel wall and surrounding tissue. Distension estimates were obtained from a wall tracking algorithm using tracking points at various depths within the wall, and further processed to assess radial and circumferential strain. The simulated data demonstrated that circumferential strain can be estimated with reasonable accuracy (especially for the common carotid artery and at the lumen-intima and media-adventitia interface), but the technique does not allow to reliably assess intra-arterial radial strain. These findings were supported by in vivo data of 10 healthy adults, showing similar circumferential and radial strain profiles throughout the arterial wall. We concluded that these deviations are present due to the complex 3-D vessel wall deformation, the presence of specular reflections and, to a lesser extent, the spatially varying beam profile, with the error depending on the phase in the cardiac cycle and the scanning location. 相似文献
107.
Fluoropolymers are characterized by high chemical inertness and, when in solid state, by superficial dipoles due to the C–F bond where the charge density is strongly displaced. These two characteristics are exploited here for fine control of charge balance in organic light-emitting devices and for preventing electrochemical interaction between heterogeneous layers. The insertion of a thin layer of polytetrafluoroethylene, PTFE, at the interface between poly(ethylene dioxythiophene):poly(styrene sulfonic acid), PEDOT:PSS, and an electroluminescent polymer leads to improved device efficiency and longevity. The presence of the superficial dipole increases the effective work function of the anode and improves the charge balance which enhances the external quantum efficiency, EQE, of the devices by up to a factor of two without significant effects on the luminance levels. The insertion of the PTFE layer reduces the photoluminescence quenching at the PEDOT:PSS/polymer interface, however we show that the EQE enhancement is mainly due to a better confinement of minority carrier electrons in the active layer. The lifetime of the devices shows a remarkable increase correlated with the insertion of the PTFE layer. Such improvements are ascribed to the reduced electrochemical interaction between the electroluminescent polymer and PEDOT:PSS due to the chemically inert nature of PTFE. The PTFE acts as a chemical zipper of two heterogeneous media with the added functionality of control over the charge balance. 相似文献
108.
Gianluca Galimberti Stefania Pagliara Stefano Ponzoni Stefano Dal Conte Federico Cilento Gabriele Ferrini Stephan Hofmann Muhammad Arshad Cinzia Cepek Fulvio Parmigiani 《Carbon》2011,49(15):5246-5252
Using time-resolved reflectivity measurements on unaligned and aligned bundled single-wall carbon nanotubes with a pump energy of 1.55 eV, quasi-resonant with the second Van Hove singularity of semiconducting tubes, a positive sign of the transient reflectivity is detected in unaligned nanotubes. In contrast a negative sign is detected in aligned nanotubes. This discovery addresses a long-standing question showing that in unaligned nanotubes the stronger intertube interactions favor the formation of short-lived free charge carriers in semiconducting tubes. A detailed analysis of the transient reflectivity spectral response shows that the free carriers in the photo-excited state of semiconducting tubes move towards metallic tubes in about 400 fs. 相似文献
109.
110.
Sergio Callegari Fabio Pareschi Gianluca Setti Mani Soma 《International Journal of Circuit Theory and Applications》2013,41(12):1290-1317
Resonate and Fire (R+F) models were introduced to account for many phenomena occurring in biological neurons showing sub‐threshold oscillations of the membrane potential. In information technology, they are at the basis of Chaotic Spiking Oscillators (CSOs), exploitable in Pulse Coupled Neural Networks (PCNNs). This paper illustrates how the R + F paradigm can also be used for the testing of analog signal processing structures (and specifically filters), extending the Oscillation Based Test (OBT) framework. The rich dynamics of the R + F model is used to encode the block under test features and faults into pulse trains directly processable at the digital level. Means to achieve a precise characterization of firing times are provided and used for parametric testing. Considerations about the trade‐off between testing times and accuracy are provided together with a practical example and simulation data. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献