全文获取类型
收费全文 | 412篇 |
免费 | 24篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 141篇 |
金属工艺 | 1篇 |
机械仪表 | 3篇 |
建筑科学 | 22篇 |
能源动力 | 21篇 |
轻工业 | 29篇 |
水利工程 | 3篇 |
无线电 | 27篇 |
一般工业技术 | 71篇 |
冶金工业 | 33篇 |
原子能技术 | 9篇 |
自动化技术 | 72篇 |
出版年
2023年 | 8篇 |
2022年 | 27篇 |
2021年 | 38篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 13篇 |
2017年 | 12篇 |
2016年 | 13篇 |
2015年 | 15篇 |
2014年 | 13篇 |
2013年 | 34篇 |
2012年 | 29篇 |
2011年 | 31篇 |
2010年 | 17篇 |
2009年 | 21篇 |
2008年 | 19篇 |
2007年 | 27篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 22篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1991年 | 3篇 |
1988年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有436条查询结果,搜索用时 0 毫秒
41.
Simoncelli and co-workers have proposed statistically-derived nonlinear divisive normalization models of the primary visual cortex (V1) that are consistent with the hypothesis that sensory systems are adapted to the signals to which they are exposed. In this paper, we present a more rigorous mathematical formulation and analysis of these statistically-derived models in terms of mutual information as a metric for statistical independence. We prove that the ad hoc choice of divisive normalization parameters proposed by Simoncelli and co-workers does not guarantee statistical independence between the output responses, but interestingly such choice does guarantee that each output response is statistically independent of almost all the linear inputs. This holds for the two different models of natural image statistics analysed theoretically, and is consistent with empirical results obtained on a set of natural images. 相似文献
42.
We compared the ability of auditory, visual, and audiovisual (bimodal) exogenous cues to capture visuo-spatial attention under conditions of no load versus high perceptual load. Participants had to discriminate the elevation (up vs. down) of visual targets preceded by either unimodal or bimodal cues under conditions of high perceptual load (in which they had to monitor a rapidly presented central stream of visual letters for occasionally presented target digits) or no perceptual load (in which the central stream was replaced by a fixation point). The results of 3 experiments showed that all 3 cues captured visuo-spatial attention in the no-load condition. By contrast, only the bimodal cues captured visuo-spatial attention in the high-load condition, indicating for the first time that multisensory integration can play a key role in disengaging spatial attention from a concurrent perceptually demanding stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
43.
Tatiana S. de Araujo Zélia S. Macedo Petrus A. S. C. de Oliveira Mário E. G. Valerio 《Journal of Materials Science》2007,42(7):2236-2243
Pure and Cr3+-doped hydroxyapatite (HAP) were prepared via chemical precipitation route. The XRD measurements revealed that the typical
HAP powder pattern was obtained. SEM analysis indicated that aggregates of nanoparticles were formed. EDX analysis indicates
that the [Ca]/[P] concentration ratio was higher than the expected values but can be explained by the presence of carbonate
groups as dopants. The optical absorption spectra of the doped samples presented absorption bands typical of Cr3+ occupying to different crystalline sites. From the position of the bands, it was possible to estimate the crystal field parameters
for both sites of Cr3+ in the HAP matrix. The emission spectra of the Cr-doped samples were also investigated and typical transitions of the dopant
ion, in trivalent state, were identified. The potential use of the Cr3+-HAP as fluorescent probes for medical applications was discussed. 相似文献
44.
Antonio Marigo Valerio Causin Carla Marega Paolo Ferrari 《Polymer International》2004,53(12):2001-2008
Wide‐angle X‐ray scattering and differential scanning calorimetry measurements have been conducted on seven random copolymers of propylene with ethylene in order to study the γ phase formation as a function of the comonomer content. The lamellar morphology of the samples was also investigated by small‐angle X‐ray scattering. The content of the γ phase was found to go through a maximum with crystallization temperature and to increase with comonomer concentration, up to a point (ethylene ≥6.5 wt%) where the latter parameter became less influential. The multiple melting endotherms behaviour of the samples was studied by DSC and temperature‐controlled diffractometric techniques. The attribution of the DSC peaks to the different isotactic polypropylene polymorphs that form in these conditions was confirmed. The results obtained permitted us to ascertain that, in the experimental conditions chosen, some further formation of crystallites takes place during the quenching to room temperature after the crystallization isotherm. In this phase, the chains organize themselves in stacks with thin lamellae, forming a distinct population with respect to those formed on isothermal crystallization. The melting of the thinner lamellae determines a convergence of the two populations into just one, still retaining an organization in stacks, that gradually disappears until complete melting of the material. Copyright © 2004 Society of Chemical Industry 相似文献
45.
Silvia Cammarano Valerio Roberto Maria Lo Verso Chiara Aghemo 《Building Research & Information》2015,43(2):222-237
Results are presented from a parametric study that assessed the amount of daylight in rooms with different architectural features: the orientation, window size and visible glazing transmittance, room depth, external obstruction angle and site. Annual lighting simulations were run in order to understand how the daylight availability within a space changes as a function of the architectural features. A sub-dataset of the full result database is examined in detail for north- and south-facing rooms in Turin, north-west Italy, with a visible glazing transmittance of 70%. Each feature is analysed for its influence on the daylighting conditions. A simple graphical tool is presented to promote an easier reading of the results. This was developed to provide a synthesis of information to the design team. It shows the influence of preliminary design solutions on the amount of indoor daylight. This allows a design team to assess indoor daylighting from the earliest design phases onwards and to determine which combinations of architectural features are able to provide high, acceptable or low daylight levels within a room. 相似文献
46.
47.
A single-step method to coat and bifunctionalize water-reduced gold nanoparticles (NPs) with two distinct reactive groups is reported. The coating is based on a peptide that bonds to the NPs surface by its N-cysteine amino acid, terminates with a C-terminal lysine, and stabilizes the colloids, thanks to the surface organization provided by the rest of the non-polar chain. The process yields stable, non-cytotoxic NPs presenting reactive amine and carboxylic groups on the surface; these allow rapid, selective and modular conjugation of virtually any chosen biomolecule or fluorophore. Functionalized and conjugated nanostructures are analyzed by electrophoresis, SEM, SERS; their biocompatibility and delivery capability are tested by cellular-uptake experiments. 相似文献
48.
Tulyaganov DU Agathopoulos S Valerio P Balamurugan A Saranti A Karakassides MA Ferreira JM 《Journal of materials science. Materials in medicine》2011,22(2):217-227
New compositions of bioactive glasses are proposed in the CaO–MgO–SiO2–Na2O–P2O5–CaF2 system. Mineralization tests with immersion of the investigated glasses in simulated body fluid (SBF) at 37°C showed that
the glasses favour the surface formation of hydroxyapatite (HA) from the early stages of the experiments. In the case of daily
renewable SBF, monetite (CaHPO4) formation competed with the formation of HA. The influence of structural features of the glasses on their mineralization
(bioactivity) performance is discussed. Preliminary in vitro experiments with osteoblasts’ cell-cultures showed that the glasses
are biocompatible and there is no evidence of toxicity. Sintering and devitrification studies of glass powder compacts were
also performed. Glass-ceramics with attractive properties were obtained after heat treatment of the glasses at relatively
low temperatures (up to 850°C). 相似文献
49.
Gualberto Antonio Zumbardo-Bacelis Linnette Aracely Meza-Villegas Cesar Antonio Pérez-Aranda Rossana Vargas-Coronado Omar Castillo-Cruz Vanessa Montaño-Machado Diego Mantovani Juan Valerio Cauich-Rodríguez 《应用聚合物科学杂志》2021,138(42):51247
Polymer blends based on Tecoflex™ and an experimental aliphatic polyurethane (HMDI-PCL-arginine stands for 4,4 (metylene-biscyclohexyl) isocyanate - poly (ε caprolactone) diol, SPUUR stands for segmented poly(urea)urethanes using amino acid of L-Arginine as chain extender) were obtained by solvent casting, and further studied by fourier transform infrared (FTIR) and Raman spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis, and X-ray diffraction (XRD). Their biological performances were assessed in terms of hemocompatibility and Human umbilical vein endothelial cell (HUVEC) cytotoxicity. Tensile properties of dumbbell specimens were compared to longitudinal and circumferential tensile properties of tubular vascular graft. FTIR showed that as the SPUUR content increased in the blend, absorptions at 2860 cm−1 increased, carbonyl absorptions at 1724 cm−1 broaden and the small peak at 2796 cm−1, typical of Tecoflex™ disappeared. Raman spectroscopy showed that the low intensity carbonyl absorption at 1724 cm−1 also increased with SPUUR content. DSC allowed detection of PCL soft segment melting (Tm = 50°C) in agreement with X-ray reflections at 21.3° and 23.6°, assigned to SPUUR. However, no improvements in thermal stability were detected by TGA by blending. The addition of SPUUR to Tecoflex™ improved hemocompatibility and HUVEC cytotoxicity. The vascular grafts performance showed that 40% SPUUR blends exhibited the highest force in the longitudinal test whereas 50% SPUUR blends showed the highest circumferential force. Pressure burst strength was higher than 1000 mmHg for all blends. Overall, these blends can be used for high caliber vascular grafts. 相似文献
50.
Frontoni Emanuele Mancini Adriano Zingaretti Primo Contigiani Marco Bello Luigi Di Placidi Valerio 《Microsystem Technologies》2018,24(3):1369-1377
Microsystem Technologies - The shelf out-of-stock (SOOS) problem is relevant for retailers and producers since the absence of products on the shelf can lead to a significant reduction of... 相似文献