全文获取类型
收费全文 | 1437篇 |
免费 | 92篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 17篇 |
综合类 | 4篇 |
化学工业 | 432篇 |
金属工艺 | 26篇 |
机械仪表 | 42篇 |
建筑科学 | 45篇 |
矿业工程 | 9篇 |
能源动力 | 39篇 |
轻工业 | 219篇 |
水利工程 | 15篇 |
石油天然气 | 8篇 |
无线电 | 68篇 |
一般工业技术 | 233篇 |
冶金工业 | 112篇 |
原子能技术 | 3篇 |
自动化技术 | 258篇 |
出版年
2024年 | 4篇 |
2023年 | 9篇 |
2022年 | 49篇 |
2021年 | 85篇 |
2020年 | 57篇 |
2019年 | 54篇 |
2018年 | 71篇 |
2017年 | 72篇 |
2016年 | 69篇 |
2015年 | 55篇 |
2014年 | 59篇 |
2013年 | 114篇 |
2012年 | 103篇 |
2011年 | 109篇 |
2010年 | 91篇 |
2009年 | 109篇 |
2008年 | 65篇 |
2007年 | 60篇 |
2006年 | 55篇 |
2005年 | 29篇 |
2004年 | 19篇 |
2003年 | 31篇 |
2002年 | 24篇 |
2001年 | 12篇 |
2000年 | 6篇 |
1999年 | 12篇 |
1998年 | 27篇 |
1997年 | 24篇 |
1996年 | 11篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
排序方式: 共有1530条查询结果,搜索用时 515 毫秒
81.
Dbora Drummond Hauss Monteiro Henrique Limboro Rodrigo Guimares Porto Allyson Nogueira Moreira Wagner Nunes Rodrigues Cludia Silami de Magalhes 《Microscopy research and technique》2020,83(6):597-603
The MeX? software is a useful tool for tridimensional data collection for surface evaluation and could be relevant to evaluate the same specimen in different phases of the study, assuming repeated measures of dental enamel roughness. The aim of this study was to evaluate the influence of sample metallization for dental enamel roughness analysis with 3D images reconstructed using MeX? software from Scanning Electron Microscopy (SEM) images. The influence of 74.98% (%mol/mol) argon?oxygen plasma for carbon layer removal on surface roughness of the metallized specimen was also evaluated. Dental enamel specimens were prepared for SEM analysis with and without carbon metallization using conventional or environmental modes. Argon?oxygen plasma for carbon layer removal was used and surface roughness was re‐evaluated. Roughness obtained by SEM and MeX? reconstructed images, with or without metallization, did not differ. No significant alteration on surface roughness after carbon layer removal using plasma was found. SEM baseline evaluation using conventional mode without sample preparation and in environmental mode were not comparable. Roughness of enamel 3D images reconstructed with MeX? software from SEM images, with or without metallization was similar. The 74.98% (%mol/mol) argon?oxygen plasma removed the carbon layer with no effect on enamel roughness. 相似文献
82.
Rodrigo F. P. Martins Arman Ahnood Nuno Correia Luís M. N. P. Pereira Raquel Barros Pedro M. C. B. Barquinha Ricardo Costa Isabel M. M. Ferreira Arokia Nathan Elvira E. M. C. Fortunato 《Advanced functional materials》2013,23(17):2153-2161
The ability to process and dimensionally scale field‐effect transistors with and on paper and to integrate them as a core component for low‐power‐consumption analog and digital circuits is demonstrated. Low‐temperature‐processed p‐ and n‐channel integrated oxide thin‐film transistors in the complementary metal oxide semiconductor (CMOS) inverter architecture are seamlessly layered on mechanically flexible, low‐cost, recyclable paper substrates. The possibility of building these circuits using low‐temperature processes opens the door to new applications ranging from smart labels and sensors on clothing and packaging to electronic displays printed on paper pages for use in newspapers, magazines, books, signs, and advertising billboards. Because the CMOS circuits reported constitute fundamental building blocks for analog and digital electronics, this development creates the potential to have flexible form factor computers seamlessly layered onto paper. The holistic approach of merging low‐power circuitry with a recyclable substrate is an important step towards greener electronics. 相似文献
83.
Limnological features of Funil Reservoir (R.J., Brazil) and indicator properties of rotifers and cladocerans of the zooplankton community 总被引:3,自引:0,他引:3
Christina W. C. Branco Maria-Isabel A. Rocha Gláucia F. S. Pinto Gisele A. Gômara Rodrigo De Filippo 《Lakes & Reservoirs: Research and Management》2002,7(2):87-92
Funil Reservoir receives inflow from a highly industrialized region and acts as a natural sink to pollutants. Among the consequences of the uncontrolled nutrient loading is the constant presence and periodic heavy blooms of Microcystis aeruginosa . This study verified limnological features and zooplankton assemblage of the Funil Reservoir focusing on the environmental-indicator properties of rotifers and cladocerans. The summer bloom of M. aeruginosa caused reductions in water transparency, nitrate and orthophosphate concentrations and raises in chlorophyll a , pH, dissolved oxygen and chemical oxygen demand values. All zooplankton species presented spatial and temporal variations with the exception of the copepods, which were present in all samples. According to canonical correspondence analysis, ammonium was the variable most related to zooplankton variability and different Rotifera and Cladocera assemblages indicated distinct environment conditions. Rotifer taxa associated with increases of water temperature and chlorophyll a concentration were found with high densities during M. aeruginosa blooms. Species of rotifer and cladocerans are suggested as indicators that can be used to identify different physical and chemical gradients or eutrophic increases in Funil Reservoir. 相似文献
84.
Döne Demirgöz Rodrigo Navarro Mónica Pérez Helmut Reinecke Alberto Gallardo 《应用聚合物科学杂志》2010,115(2):896-900
2‐Hydroxyethylmethacrylate (HEMA) and acrylamide (AA) have been copolymerized via free radical mechanism, in the presence of 5 mol % of four different crosslinker systems, the symmetric ethylenglycoldimethacrylate (EGDMA), bisacrylamide (BIS), a mixture of EGDMA and BIS, and the asymmetric acrylamideethylenmethacrylate (METAA). The polymerizations have been monitored with a rheometer, exhibiting the gel obtained with the asymmetric METAA, an elastic modulus that is dramatically increased compared with those of the gels prepared with the other three crosslinker systems. A kinetic analysis using the terminal model has been used to build probabilistic surfaces that give information about how the crosslinker is incorporated into the network. This analysis shows a high dissimilarity between the reactions using the asymmetric and the mixture of symmetric crosslinkers, what has been correlated to the difference in modulus. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
85.
Nelly Abigail Rodríguez Efrain Almanza María de Jesús Pérez Carlos Rodrigo Mu?iz Scott Packer Russell Steel 《Frontiers of Materials Science in China》2010,4(4):415-419
This study evaluates the degree of sensitization (DOS) of 304 stainless steel joined by friction stir welding (FSW). Single-loop
electrochemical potentiokinetic reactivation tests were performed using a 0.5 mol/L H2SO4 + 0.01 mol/L KSCN solution. Sensitization was promoted by exposition of the stainless steel at temperatures between 400°C
and 850°C. The microstructure was characterized using optical microscopy to identify the weld zone and the base metal. The
samples treated at 550°C showed the most severe intergranular corrosion. The DOS was lower in the weld zone than in the base
metal after heat treatments. This reduction in the DOS for the weld zone indicates that FSW is a beneficial process in joining
stainless steel. 相似文献
86.
Rubn Crdenes Rodrigo de Luis-García Meritxell Bach-Cuadra 《Computer methods and programs in biomedicine》2009,96(2):108-124
Evaluation of segmentation methods is a crucial aspect in image processing, especially in the medical imaging field, where small differences between segmented regions in the anatomy can be of paramount importance. Usually, segmentation evaluation is based on a measure that depends on the number of segmented voxels inside and outside of some reference regions that are called gold standards. Although some other measures have been also used, in this work we propose a set of new similarity measures, based on different features, such as the location and intensity values of the misclassified voxels, and the connectivity and the boundaries of the segmented data. Using the multidimensional information provided by these measures, we propose a new evaluation method whose results are visualized applying a Principal Component Analysis of the data, obtaining a simplified graphical method to compare different segmentation results. We have carried out an intensive study using several classic segmentation methods applied to a set of MRI simulated data of the brain with several noise and RF inhomogeneity levels, and also to real data, showing that the new measures proposed here and the results that we have obtained from the multidimensional evaluation, improve the robustness of the evaluation and provides better understanding about the difference between segmentation methods. 相似文献
87.
Andréia F. Zanette Rodrigo A. Barella Sibele B.C. Pergher Helen Treichel Débora Oliveira Marcio A. Mazutti Edson A. Silva J. Vladimir Oliveira 《Renewable Energy》2011,36(2):726-731
This work investigates the production of fatty acid methyl esters (FAME) from Jatropha curcas oil using a variety of heterogeneous catalysts: resins, zeolites, clays, hydrotalcites, aluminas and niobium oxide. For this purpose, a catalyst screening was first conducted in a batch reactor at the following operating conditions: oil to methanol molar ratio of 1:9, 6 h of reaction, 5 wt% catalyst, at 333 and 393 K. From the screening step, KSF clay and Amberlyst 15 catalysts were selected to carry out a 23 full factorial central composite rotatable design so as to elucidate the effects of process variables on FAME yield. The optimum reaction conditions for both catalysts were found to be oil to methanol molar ratio of 1:12, 5 wt% of catalyst, 433 K and 6 h of reaction with a FAME yield of about 70 wt%. A kinetic study was then experimentally performed and a semi-empirical model was built to represent the experimental data. Finally, catalyst re-utilization in five successive batch experiments was evaluated at the optimized conditions. 相似文献
88.
89.
Thales Leandro Coutinho de Oliveira Rodrigo de Araújo Soares Roberta Hilsdorf Piccoli 《Meat science》2013
The antimicrobial effect of oregano (Origanum vulgare L.) and lemongrass (Cymbopogon citratus (DC.) Stapf.) essential oils (EOs) against Salmonella enterica serotype Enteritidis in in vitro experiments, and inoculated in ground bovine meat during refrigerated storage (4 ± 2 °C) for 6 days was evaluated. The Weibull model was tested to fit survival/inactivation bacterial curves (estimating of p and δ parameters). The minimum inhibitory concentration (MIC) value for both EOs on S. Enteritidis was 3.90 μl/ml. The EO concentrations applied in the ground beef were 3.90, 7.80 and 15.60 μl/g, based on MIC levels and possible activity reduction by food constituents. Both evaluated EOs in all tested levels, showed antimicrobial effects, with microbial populations reducing (p ≤ 0.05) along time storage. Evaluating fit-quality parameters (RSS and RSE) Weibull models are able to describe the inactivation curves of EOs against S. Enteritidis. The application of EOs in processed meats can be used to control pathogens during refrigerated shelf-life. 相似文献
90.