全文获取类型
收费全文 | 6540篇 |
免费 | 527篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 121篇 |
综合类 | 3篇 |
化学工业 | 1667篇 |
金属工艺 | 176篇 |
机械仪表 | 225篇 |
建筑科学 | 177篇 |
矿业工程 | 17篇 |
能源动力 | 286篇 |
轻工业 | 1332篇 |
水利工程 | 64篇 |
石油天然气 | 44篇 |
无线电 | 398篇 |
一般工业技术 | 1096篇 |
冶金工业 | 665篇 |
原子能技术 | 49篇 |
自动化技术 | 758篇 |
出版年
2024年 | 23篇 |
2023年 | 71篇 |
2022年 | 171篇 |
2021年 | 354篇 |
2020年 | 229篇 |
2019年 | 288篇 |
2018年 | 304篇 |
2017年 | 334篇 |
2016年 | 281篇 |
2015年 | 207篇 |
2014年 | 283篇 |
2013年 | 527篇 |
2012年 | 411篇 |
2011年 | 448篇 |
2010年 | 315篇 |
2009年 | 353篇 |
2008年 | 310篇 |
2007年 | 263篇 |
2006年 | 220篇 |
2005年 | 140篇 |
2004年 | 140篇 |
2003年 | 139篇 |
2002年 | 117篇 |
2001年 | 79篇 |
2000年 | 83篇 |
1999年 | 86篇 |
1998年 | 195篇 |
1997年 | 149篇 |
1996年 | 120篇 |
1995年 | 69篇 |
1994年 | 57篇 |
1993年 | 53篇 |
1992年 | 27篇 |
1991年 | 17篇 |
1990年 | 29篇 |
1989年 | 17篇 |
1988年 | 26篇 |
1987年 | 12篇 |
1986年 | 14篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 20篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有7078条查询结果,搜索用时 421 毫秒
991.
992.
Effects of gastrointestinal digestion models in vitro on phenolic compounds and antioxidant activity of juçara (Euterpe edulis) 下载免费PDF全文
Siluana Katia Tischer Seraglio Luciano Valdemiro Gonzaga Mayara Schulz Luciano Vitali Gustavo Amadeu Micke Ana Carolina Oliveira Costa Roseane Fett Graciele Da Silva Campelo Borges 《International Journal of Food Science & Technology》2018,53(8):1824-1831
This study evaluated the effects of different gastrointestinal digestion models in vitro on the bioaccessibility of phenolics and antioxidant activity in juçara frozen pulp. In the sequence, method 3 was applied to juçara fruit in three different stages of maturation (vitrin – reddish fruits, mature – purple fruits, tuíra – deep purple fruits). In the method applied, the final pH adopted was 5.0, in order to avoid interference in the assay used to determine the antioxidant activity, and BHT was used to prevent excessive oxidation in the system. In this method, higher values for antioxidant activity were obtained (3574.95–3719.10 μmol L?1 Trolox 100 g?1 pulp) compared with the other two methods tested (1969.14–3034.74 μmol L?1 Trolox 100 g?1 pulp). In relation to juçara fruit, the mature stage was found to be ideal for processing, showing generally higher values of the bioaccessibility for phenolics and antioxidant activity compared to other maturation stages. 相似文献
993.
Matheus Henrique Jantsch Viviane Martins Bernardes Juliana Sorraila Oliveira Daniela Ferreira Passos Guilherme Lopes Dornelles Alessandra Guedes Manzoni Fernanda Licker Cabral Jean Lucas Gutknecht da Silva Maria Rosa Chitolina Schetinger Daniela Bitencourt Rosa Leal 《Journal of Food Biochemistry》2021,45(4):e13636
994.
Leonardo Sales Araujo Alessandra Vieira Guimarães Maísa Conceição Siqueira Matheus Campolina Mendes Loic Mallet Dilson Silva dos Santos Luiz Henrique de Almeida 《International Journal of Hydrogen Energy》2021,46(29):16164-16178
The nickel-base superalloy 718 is a precipitation hardened alloy widely used in the nuclear fuel assembly of pressurized water reactors (PWR). However, the alloy can experience failure due to hydrogen embrittlement (HE). The processing route can influence the microstructure of the material and, therefore, the HE degree. In particular, the size and distribution of the (Nb,Ti)C particles can be affected by the processing. In this regard, the objective of this work was to analyze the influence of cold and hot deformation processing routes on the development of the microstructure, and the consequences on mechanical properties and hydrogen embrittlement. Tensile samples were hydrogenated through gaseous charging and compared to non-hydrogenated samples. Characterization was performed via scanning and transmission electron microscopies, as well as electron backscattered diffraction. The processing was effective to promote significant variations in average grain size and length fraction of special Σ3n boundaries, as well as reduction of average (Nb,Ti)C particle size, being these changes more intense for the cold-rolled route. For the mechanical properties, on one side, the cold-rolled route presented the highest increase in ductility for non-hydrogenated samples, while, on the other side, had the highest degree of embrittlement under hydrogen. This dual behavior was attributed to the interaction of hydrogen with the (Nb,Ti)C particles and stringers and its ensuing influence on the fracture processes. 相似文献
995.
996.
Pâmela Maria Moreira Fonseca Paulo Luiz De Sá Júnior Walter Miyakawa Álvaro José Damião L.H. Moreira da Silva Melo Renato Amaro Zângaro 《臭氧:科学与工程》2019,41(3):242-249
Ozonated water has been demonstrated to induce significant results in terms of the elimination of microorganisms. The present study assessed the damage to Streptococcus mutans after exposure to ozonated water; the ozone generator was adjusted to provide an outlet concentration of 60 mg/L, the samples were submitted to different ozonation times 1, 2, 4, 6, and 10 mi. Scanning electron microscopy and atomic force images were obtained to identify damage to the bacteria, followed by reactive oxygen species (ROS) evaluation and microbial viability. The results showed a significant reduction in viability and the images evidenced the generation of gaps on the microbial wall and surface layer alterations. Ozone can induce significant damage to S. mutans, thus suggesting that the use of ozonated water to prevent carious lesion formation is extremely promising. 相似文献
997.
Francisco Regis Machado Nascimento Aldemar Martínez González Electo Eduardo Silva Lora Albert Ratner Jose Carlos Escobar Palacio Rafaela Reinaldo 《International Journal of Hydrogen Energy》2021,46(36):18740-18766
Thermochemical conversion by gasification process is one of the most relevant technologies for energy recovery from solid fuel, with an energy conversion efficiency better than other alternatives like combustion and pyrolysis. Nevertheless, the most common technology used in the last decades for thermochemical conversion of solid fuel through gasification process, such as coal, agriculture residues or biomass residues are the fluidized bed or bubbling fluidized bed system. For these gasification technologies, an inert bed material is fed into reactor to improve the homogenization of the particles mixture and increase the heat transfer between solid fuel particles and the bed material. The fluidized bed reactors usually operate at isothermal bed temperatures in the range of 700–1000 °C, providing a suitable contact between solid and gas phases. In this way, chemical reactions with high conversion yield, as well as an intense circulation and mixing of the solid particles are encouraged. Moreover, a high gasification temperature favours carbon conversion efficiency, increasing the syngas production and energy performance of the gasifier. However, the risk of eutectic mixtures formation and its subsequent melting process are increased, and hence the probability of bed agglomeration and the system collapse could be increased, mainly when alkali and alkaline earth metals-rich biomasses are considered. Generally, bed agglomeration occurs when biomass-derived ash reacts with bed material, and the lower melting temperature of ash components promotes the formation of highly viscous layers, which encourages the progressive agglomerates creation, and consequently, the bed collapse and system de-fluidization. Taking into account the relevance of this topic to ensure the normal gasification process operating, this paper provides several aspects about bed agglomeration, mostly for biomass gasification systems. In this way, chemistry and mechanism of bed agglomeration, as well as, some methods for in-situ detection and prediction of the bed agglomeration phenomenon are reviewed and discussed. 相似文献
998.
Erivan de Souza Oliveira Mighay Lovera Valessa Rios Pires Francisco Rogênio da Silva Mendes Nadya Virginia Lima Peixoto Maia João Pedro Viana Rodrigues Maria do Socorro Rocha Bastos Huai N. Cheng Atanu Biswas Renato de Azevedo Moreira Ana Cristina de Oliveira Monteiro Moreira 《Journal of Food Processing and Preservation》2022,46(3):e16408
999.
Nicolle Dal’Acqua Ana Claudia Rangel Faria Mário César Vebber Hernane da Silva Barud Marcelo Giovanela Giovanna Machado Janaina da Silva Crespo 《International Journal of Hydrogen Energy》2018,43(33):15794-15806
The issues related to renewable energy sources is a matter of great worldwide appeal due to the increasing energy demand, instability in oil prices and environmental problems. In this context, the purpose of this study was to prepare self-assembled films of polyallylamine hydrochloride and poly (acrylic acid) supported onto bacterial cellulose membranes by a layer-by-layer approach with titanium dioxide (TiO2) nanoparticles and different concentrations of gold for application in hydrogen gas (H2) production by photocatalysis. The influence of the gold concentration and the presence and size of the gold nanoparticles (Au NPs), as well as the surface and thickness of the films on H2 production was investigated. The results showed that the film, prepared with a lower concentration of gold, presented the smallest Au NPs and, therefore, greater contact with the TiO2 nanoparticle surfaces, producing more H2. By analyzing the variation in all the experimental parameters used in the preparation of the films, it can be concluded that the best H2 production achieved was 29.12 μmol h?1 cm2. 相似文献
1000.