全文获取类型
收费全文 | 1192篇 |
免费 | 114篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 16篇 |
综合类 | 2篇 |
化学工业 | 362篇 |
金属工艺 | 21篇 |
机械仪表 | 24篇 |
建筑科学 | 30篇 |
能源动力 | 55篇 |
轻工业 | 175篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 107篇 |
一般工业技术 | 222篇 |
冶金工业 | 39篇 |
原子能技术 | 4篇 |
自动化技术 | 247篇 |
出版年
2024年 | 2篇 |
2023年 | 33篇 |
2022年 | 90篇 |
2021年 | 113篇 |
2020年 | 46篇 |
2019年 | 43篇 |
2018年 | 71篇 |
2017年 | 58篇 |
2016年 | 68篇 |
2015年 | 57篇 |
2014年 | 54篇 |
2013年 | 106篇 |
2012年 | 91篇 |
2011年 | 100篇 |
2010年 | 65篇 |
2009年 | 67篇 |
2008年 | 54篇 |
2007年 | 45篇 |
2006年 | 34篇 |
2005年 | 21篇 |
2004年 | 22篇 |
2003年 | 15篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1977年 | 2篇 |
1976年 | 3篇 |
排序方式: 共有1310条查询结果,搜索用时 31 毫秒
131.
Laura Esposito Andreana PiancastelliAnna Luisa Costa Marina SerantoniGuido Toci Matteo Vannini 《Optical Materials》2011,33(5):713-721
This article focuses on the importance of the ceramic production process for the final transparency and overall optical quality of materials to be used as laser hosts. YAG-based ceramics are prepared starting from commercial powders. The materials are prepared by reactive sintering in a clean atmosphere and under high vacuum. Nd or Yb are selected as active elements as the more appropriate for high energy and high peak power lasers. The powder type and treatment and the solvent removal technique are described in detail as well as the experimental conditions adopted during shaping. The influence of the pre-sintering and sintering cycles on the reaction among the involved oxides and on the microstructure after sintering is shown. The optical characterization is also reported. 相似文献
132.
Travaglia F Bordiga M Locatelli M Coïsson JD Arlorio M 《Journal of food science》2011,76(5):C742-C749
Abstract: The polymeric proanthocyanidins (PAs) composition of skins and seeds from different Vitis vinifera L. cv. was evaluated, sampling 37 cultivar, preserved in the grapevine collection of Grinzane Cavour (Piedmont, Italy). PAs were quantified using both spectrophotometric (n‐butanol and vanillin assay) and chromatographic (high‐performance liquid chromatography [HPLC]) methods, and the evaluation of their antioxidant activity was performed using the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) scavenging assay. Results of PAs quantification with the different methods were significantly correlated. A strong correlation pointed out between anthocyans and PAs content (particularly regarding HPLC method; r = 0.9359, P = 0), and the antioxidant activity was not dependent on the polymeric PAs content, but negatively correlated with the degree of polymerization (r =–0.6102, P = 1 × 10?4). The hierarchical clustering on principal components analysis allowed grouping the samples in 3 different clusters, observing a direct association between the cluster classification and the anthocyans/PAs content. 相似文献
133.
Dye sensitized photovoltaic cells: Attaching conjugated polymers to zwitterionic ruthenium dyes 总被引:1,自引:0,他引:1
The synthesis of a zwitterionic ruthenium dye that binds to anatase surfaces and has a built-in functionality that allows for the attachment of a conjugated polymer chain is presented. The system was found to adsorb on the surface of anatase anchored by the ruthenium dye. Two types of devices were prepared: standard photoelectrochemical (PEC) solar cells and polymer solar cells. The PEC solar cells employed a sandwich geometry between TiO2 nanoporous photoanodes and Pt counter electrodes using LiI/I2 in CH3CN as an electrolyte. The polymer solar cells employed planar anatase electrodes and the complex was adsorbed onto the surface before evaporation of gold electrodes. Alternative devices were obtained by spincoating of the polymer solution onto PEDOT:PSS covered indium-doped tin oxide substrates. PEC solar cells gave the best results and the main finding was that the polymer chain served as a light harvesting antenna for the ruthenium dye. 相似文献
134.
Virginie Duprez Matteo Biancardo Frederik C. Krebs 《Solar Energy Materials & Solar Cells》2007,91(4):230-237
A series of ruthenium complexes with and without TiO2 anchoring carboxylic acid groups have been synthesised and characterised using nuclear magnetic resonance (NMR), UV–vis and luminescence. These complexes were adsorbed on thin films of the wide band-gap semiconductor anatase and were tested as photosensitisers under standard conditions. I/V characteristics of such devices revealed superior performance of the non-symmetric complexes [4′-(4-bromophenyl)-[2,2′; 6′,2″] terpyridine]Ru(II) [4′-(4-bromophenyl)-[2,2′; 6′,2″] terpyridine-4,4″-dicarboxylic acid] and [2,2′; 6′,2″] terpyridine Ru(II) [2,2′; 6′,2″] terpyridine-4′-carboxylic acid with a maximum output power 0.016 mW cm−2 under illumination at 100 mW cm−2 AM1.5 and efficiencies 3 times higher than the symmetric complexes. 相似文献
135.
Valerio Di Lecce Michele Esposto Matteo Bonaiuti Fausto Fantini Gaudenzio Meneghesso Enrico Zanoni Alessandro Chini 《Journal of Electronic Materials》2011,40(4):362-368
The effects of direct-current (DC) stress on GaN high-electron-mobility transistors (HEMTs) are investigated by means of numerical
simulations, by which the creation of an acceptor trap in the AlGaN barrier layer was correlated to the observed experimental
degradation. An increase in the trap concentration induces a worsening of the saturated current I
DSS, transconductance g
m, and output conductance g
O. An increase in the length of the trapping region induces a degradation of I
DSS and g
m, but can reduce g
O. Analysis of scattering parameters in the saturation region shows that the cutoff frequency f
T matches the trend of g
m. 相似文献
136.
Bertanza G Pedrazzani R Dal Grande M Papa M Zambarda V Montani C Steimberg N Mazzoleni G Di Lorenzo D 《Water research》2011,45(8):2473-2484
A major source of the wide presence of EDCs (Endocrine Disrupting Compounds) in water bodies is represented by direct/indirect discharge of sewage. Recent scientific literature reports data about their trace concentration in water, sediments and aquatic organisms, as well as removal efficiencies of different wastewater treatment schemes. Despite the availability of a huge amount of data, some doubts still persist due to the difficulty in evaluating synergistic effects of trace pollutants in complex matrices. In this paper, an integrated assessment procedure was used, based on chemical and biological analyses, in order to compare the performance of two full scale biological wastewater treatment plants (either equipped with conventional settling tanks or with an ultrafiltration membrane unit) and tertiary ozonation (pilot scale).Nonylphenol and bisphenol A were chosen as model EDCs, together with the parent compounds mono- and di-ethoxylated nonylphenol (quantified by means of GC-MS). Water estrogenic activity was evaluated by applying the human breast cancer MCF-7 based reporter gene assay. Process parameters (e.g., sludge age, temperature) and conventional pollutants (e.g., COD, suspended solids) were also measured during monitoring campaigns.Conventional activated sludge achieved satisfactory removal of both analytes and estrogenicity. A further reduction of biological activity was exerted by MBR (Membrane Biological Reactor) as well as ozonation; the latter contributed also to decrease EDC concentrations. 相似文献
137.
Giovanni Zemella Davide De March Matteo Borrotti Irene Poli 《Energy and Buildings》2011,43(12):3297-3302
Buildings are required to be more and more energy efficient, in order to comply with restrictive requirements of building regulations and energy certifications. Optimisation algorithms have shown to be effective in identifying good solutions for the design of efficient building services. In this article Evolutionary Neural Network Design (ENN-Design) has been adopted to drive the design of a typical façade module for an office building. This application is significant, since façades play a major role in the definition of the energy performance of buildings. Both single-objective and multi-objective optimisations have been carried out. The aim of the article is to introduce an innovative approach for improving the performance of building envelopes by means of a reasonable amount of calculation time. 相似文献
138.
Hierarchically Structured Magnetic Nanoconstructs with Enhanced Relaxivity and Cooperative Tumor Accumulation 下载免费PDF全文
Ayrat Gizzatov Jaehong Key Santosh Aryal Jeyarama Ananta Antonio Cervadoro Anna Lisa Palange Matteo Fasano Cinzia Stigliano Meng Zhong Daniele Di Mascolo Adem Guven Eliodoro Chiavazzo Pietro Asinari Xuewu Liu Mauro Ferrari Lon J. Wilson Paolo Decuzzi 《Advanced functional materials》2014,24(29):4584-4594
Iron oxide nanoparticles are formidable multifunctional systems capable of contrast enhancement in magnetic resonance imaging, guidance under remote fields, heat generation, and biodegradation. Yet, this potential is underutilized in that each function manifests at different nanoparticle sizes. Here, sub‐micrometer discoidal magnetic nanoconstructs are realized by confining 5 nm ultra‐small super‐paramagnetic iron oxide nanoparticles (USPIOs) within two different mesoporous structures, made out of silicon and polymers. These nanoconstructs exhibit transversal relaxivities up to ≈10 times (r 2 ≈ 835 mm ?1 s?1) higher than conventional USPIOs and, under external magnetic fields, collectively cooperate to amplify tumor accumulation. The boost in r 2 relaxivity arises from the formation of mesoscopic USPIO clusters within the porous matrix, inducing a local reduction in water molecule mobility as demonstrated via molecular dynamics simulations. The cooperative accumulation under static magnetic field derives from the large amount of iron that can be loaded per nanoconstuct (up to ≈65 fg) and the consequential generation of significant inter‐particle magnetic dipole interactions. In tumor bearing mice, the silicon‐based nanoconstructs provide MRI contrast enhancement at much smaller doses of iron (≈0.5 mg of Fe kg?1 animal) as compared to current practice. 相似文献
139.
140.
We present an original detailed theoretical modeling of guided-wave noncollinear acoustooptic (AO) interaction produced by a multifrequency surface acoustic wave (SAW) in planar guided-wave structures. The modeling of the multifrequency AO interaction is based on a modified version of the coupled-mode theory. The first- and third-order diffraction efficiency and optimum dynamic range of the Bragg cell have been calculated as a function of acoustic power, acoustic radiofrequency, and optical waveguide parameters in Y-cut Ti:LiNbO3 planar waveguides. Polynomial approximations, describing the first and third order diffraction efficiency versus normalized acoustic power in the cases of two- and three-frequency interactions, are derived and presented for the first time for arbitrarily large RF signals 相似文献