全文获取类型
收费全文 | 1994篇 |
免费 | 95篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 25篇 |
综合类 | 2篇 |
化学工业 | 484篇 |
金属工艺 | 57篇 |
机械仪表 | 38篇 |
建筑科学 | 58篇 |
矿业工程 | 9篇 |
能源动力 | 59篇 |
轻工业 | 173篇 |
水利工程 | 12篇 |
石油天然气 | 2篇 |
无线电 | 138篇 |
一般工业技术 | 374篇 |
冶金工业 | 311篇 |
原子能技术 | 18篇 |
自动化技术 | 332篇 |
出版年
2023年 | 13篇 |
2022年 | 23篇 |
2021年 | 36篇 |
2020年 | 29篇 |
2019年 | 45篇 |
2018年 | 64篇 |
2017年 | 62篇 |
2016年 | 73篇 |
2015年 | 58篇 |
2014年 | 78篇 |
2013年 | 126篇 |
2012年 | 107篇 |
2011年 | 146篇 |
2010年 | 105篇 |
2009年 | 110篇 |
2008年 | 111篇 |
2007年 | 87篇 |
2006年 | 56篇 |
2005年 | 69篇 |
2004年 | 44篇 |
2003年 | 52篇 |
2002年 | 41篇 |
2001年 | 23篇 |
2000年 | 31篇 |
1999年 | 22篇 |
1998年 | 64篇 |
1997年 | 47篇 |
1996年 | 63篇 |
1995年 | 18篇 |
1994年 | 29篇 |
1993年 | 34篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 19篇 |
1981年 | 9篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1977年 | 18篇 |
1976年 | 25篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 8篇 |
排序方式: 共有2092条查询结果,搜索用时 609 毫秒
991.
Gabrielli C Perrot H Rose D Rubin A Toqué JP Pham MC Piro B 《The Review of scientific instruments》2007,78(7):074103
A better understanding of the mechanisms located at the solid/electrolyte interface is becoming essential to the development of new applications in the electrochemical fields. The fast quartz crystal microbalance is an attractive and powerful gravimetric sensor which can be used in the dynamic regime to determine a mass/potential transfer function. The principle is equivalent to classical electrochemical impedance measurements; the only difference is the determination of mass changes given by the quartz crystal microbalance rather than current changes following sine wave modulations of the applied potential. This function appears very well adapted to characterize ionic exchanges at the electrochemical interface. Frequency/voltage converters are the key devices in translating the microbalance frequency response in terms of a continuous voltage change. The latter allows the transfer function to be obtained via a frequency response analyzer. Different converters were tested in this work in order to improve the performances of the experimental setup. 相似文献
992.
M. A. Sumesh Beno Thomas T. V. Vijesh G. Mohan Rao M. Viswanathan S. P. Karanth 《Journal of Infrared, Millimeter and Terahertz Waves》2018,39(1):6-23
Optically immersed bolometer IR detectors were fabricated using electron beam evaporated vanadium oxide as the sensing material. Spin-coated polyimide was used as medium to optically immerse the sensing element to the flat surface of a hemispherical germanium lens. This optical immersion layer also serves as the thermal impedance control layer and decides the performance of the devices in terms of responsivity and noise parameters. The devices were packaged in suitable electro-optical packages and the detector parameters were studied in detail. Thermal time constant varies from 0.57 to 6.0 ms and responsivity from 75 to 757 V W?1 corresponding to polyimide thickness in the range 2 to 70 μm for a detector bias of 9 V in the wavelength region of 14–16 μm. Highest D* obtained was 1.2×108 cmHz1/2 W?1. Noise equivalent temperature difference (NETD) of 20 mK was achieved for devices with polyimide thickness more than 32 μm. The figure of merit, NETD × τ product which describes trade-off between thermal time constant and sensitivity is also extensively studied for devices having different thickness of thermal impedance layers. 相似文献
993.
This paper investigates how to best couple hand-annotated data with information extracted from an external lexical resource to improve part-of-speech tagging performance. Focusing mostly on French tagging, we introduce a maximum entropy Markov model-based tagging system that is enriched with information extracted from a morphological resource. This system gives a 97.75?% accuracy on the French Treebank, an error reduction of 25?% (38?% on unknown words) over the same tagger without lexical information. We perform a series of experiments that help understanding how this lexical information helps improving tagging accuracy. We also conduct experiments on datasets and lexicons of varying sizes in order to assess the best trade-off between annotating data versus developing a lexicon. We find that the use of a lexicon improves the quality of the tagger at any stage of development of either resource, and that for fixed performance levels the availability of the full lexicon consistently reduces the need for supervised data by at least one half. 相似文献
994.
995.
Evaluation of colouring ability of main European elderberry (Sambucus nigra L.) varieties as potential resources of natural food colourants
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lilla Szalóki‐Dorkó Mónika Stéger‐Máté László Abrankó 《International Journal of Food Science & Technology》2015,50(6):1317-1323
Profiling and quantitative analysis of anthocyanins in five elderberry (Sambucus nigra L.) varieties, namely ‘Haschberg’, ‘Samocco’, ‘Samyl’, ‘Samident’ and ‘Sampo’, were performed in six different maturity stages from two consecutive years (2012 and 2013) and from two growing areas in Hungary. Cyanidin‐3‐O‐sambubioside‐5‐O‐glucoside, cyanidin‐3‐O‐sambubioside and cyanidin‐3‐O‐glucoside were found and identified by HPLC‐Q/TOF‐MS as major anthocyanins and were quantified by HPLC‐UV/Vis. In optimum maturity stage, ‘Samocco’ showed the highest anthocyanin content with an average of 1237 mg per 100 g dry weight in both growing areas and vintages. The dominant anthocyanin component of Samocco variety was cyanidin‐3‐O‐sambubioside, which is according to literature more stable against technology processing than cyanidin‐3‐O‐glucoside found in the other four investigated elderberry varieties in the highest concentration. ‘Samocco’, if grown under the climatic conditions of the Carpathian basin, might be a promising alternative variety for growing as raw material for natural food colourant processing industry. 相似文献
996.
Jan Hostaša Jiří Matějíček Benoît Nait‐Ali David S. Smith Willi Pabst Laura Esposito 《Journal of the American Ceramic Society》2014,97(8):2602-2606
This work presents the thermal properties of ytterbium‐doped yttrium aluminium garnet (Yb:YAG) transparent ceramics at elevated temperatures in dependence on the dopant concentration and on temperature. Transparent polycrystalline Yb:YAG ceramics were prepared by solid‐state reaction of oxide powders sintered under high vacuum. The dopant amount varied from 0 to 20 at.% of Yb. Thermal diffusivity of the sintered samples was measured by the laser and xenon flash methods at temperatures ranging from room temperature to 900°C. Both the thermal diffusivity and thermal conductivity values decreased with increasing dopant content, and until 500°C a decrease was observed also with increasing temperature. When available, the measured values were compared to data published in literature, and were found to be in good agreement. Based on the measured values, empirical relations in the form of shifted power laws are proposed for the temperature dependence of thermal diffusivity. 相似文献
997.
J. Wolf P. Longère J. M. Cadou J. P. Crété 《International Journal of Mechanics and Materials in Design》2018,14(2):177-193
The present work aims at numerically predicting the current residual strength of large engineering structures made of ductile metals against accidental failure. With this aim in view, the challenge consists in reproducing within a unified finite element-based methodology the successive steps of micro-voiding-induced damage, strain localization and crack propagation, if any. A key ingredient for a predictive ductile fracture model is the proper numerical treatment of the critical transition phase of damage-induced strain localization inside a narrow band. For this purpose, the strong discontinuity cohesive model and the eXtended Finite Element Method are combined. A propagation algorithm is proposed and studied in the context of ductile materials. Physics-motivated criteria to pass from the phase of more or less diffuse damage to strain localization and from strain localization to crack propoagation are proposed. Finally, a 2D numerical example is shown to study the performance of the failure analysis model when implemented into an engineering finite element computation code, namely Abaqus. 相似文献
998.
Zakaria Aketouane Mustapha Malha Denis Bruneau Abdellah Bah Benoît Michel Mohamed Asbik Omar Ansari 《Building Simulation》2018,11(6):1109-1122
The building sector in Morocco represents 25% of the country’s total energy consumption. The poor thermal performance of the building envelopes is one of the principal reasons for this consumption rate. In this study, the efficiency of integrating Phase Change Materials (PCM) into hollow bricks used in three typical housing types in the six climate zones in Morocco is investigated. The numerical model is based on the heat transfer equation and the apparent heat capacity formulation to model the phase change. A heat flux analysis is performed at the internal surface of the wall, giving a good understanding of the thermal behavior of hollow bricks with PCMs compared with hollow bricks with air. The results show that the heat flux density at the internal face of the wall is constant when the PCM is partially solid/liquid, and follows the outdoor conditions when the PCM is fully solid or fully liquid. Irrespective of the climate zone, the PCM with a 32 °C median melting temperature reduces the heat flux peak value in the hotel housing while the PCM with a 37 °C median melting temperature is better for the individual and collective housing. On the other hand, the PCM with a 27 °C median melting temperature is able to save up to 25% and 40% of energy consumption in the Saharan climate and oceanic climate, respectively. 相似文献
999.
Li-Juan Yuan Peng-Jie Zhang Fei Zuo Rui-Xin Luo Zhao-Liang Guo Kevin Plucknett Bei-Bei Jiang Guang-Lin Nie Fan Meng Víctor Valcárcel-Juárez Alexandre Maître Hua-Tay Lin 《Journal of the European Ceramic Society》2021,41(1):706-718
The densification behavior, microstructural development, toughening and strengthening mechanisms of Al2O3 whisker-reinforced 3Y-TZP and 12Ce-TZP composites were systematically and comparatively investigated with varying whisker lengths. Compared with 3Y-TZP/Aw composites, the presence of a Ce-Al-Si-O amorphous phase, caused by the addition of Al2O3 whiskers, promoted the densification and grain growth of 12Ce-TZP/Aw composites. Crack deflection and bridging are proposed as the primary toughening mechanisms for 3Y-TZP/Aw composites, while the t-m martensitic transformation would dominate the toughening and strengthening processes of 12Ce-TZP/Aw composites. Changes in Al2O3 whisker length would vary the distributions of internal stress and amorphous phase within the ceria-stabilized ZrO2 matrix, and hence affect the toughening and strengthening results. It indicates that effective toughening and strengthening of the Al2O3 whisker-reinforced TZP composites can be achieved by taking advantage of collaborative engineering control on the reinforcement morphology and the interface chemistry/structure. 相似文献
1000.