全文获取类型
收费全文 | 319篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 89篇 |
金属工艺 | 6篇 |
机械仪表 | 15篇 |
建筑科学 | 15篇 |
能源动力 | 8篇 |
轻工业 | 102篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 5篇 |
一般工业技术 | 44篇 |
冶金工业 | 20篇 |
原子能技术 | 1篇 |
自动化技术 | 33篇 |
出版年
2024年 | 3篇 |
2023年 | 4篇 |
2022年 | 18篇 |
2021年 | 15篇 |
2020年 | 5篇 |
2019年 | 12篇 |
2018年 | 18篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 11篇 |
2014年 | 10篇 |
2013年 | 28篇 |
2012年 | 18篇 |
2011年 | 26篇 |
2010年 | 13篇 |
2009年 | 20篇 |
2008年 | 15篇 |
2007年 | 19篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 7篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有343条查询结果,搜索用时 15 毫秒
101.
Ricardo Sercheli Rogério Matheus Vargas Ulf Schuchardt 《Journal of the American Oil Chemists' Society》1999,76(10):1207-1210
Transesterification of soybean oil with methanol has been carried out in the presence of heterogenized alkylguanidines as
catalysts. The alkylguanidines were anchored to modified polystyrene or siliceous MCM-41, encapsulated in the supercages of
zeolite Y, or entrapped in SiO2 sol-gel matrices. The catalytic activity of these catalysts was compared with that of their homogeneous counterparts, showing
that the yields of methyl esters obtained in the homogeneous phase can be obtained with the guanidines anchored to the supports
after longer reaction times. The catalysts prepared by immobilization of alkylguanidines in microporous systems showed diffusion
restrictions for the vegetable oil as well as the low stability of the inorganic framework. 相似文献
102.
The aim of this study was to compare the main antioxidant compounds content and the antioxidant activity of white grapefruit and his new hybrid (Jaffa Sweeties). Total phenols were measured colorimetrically using the Folin-Ciocalteu reagent, phenolic acids—by HPLC, anthocyanins and flavonoids—spectrophotometrically. The antioxidant activity of these fruits was determined by total antioxidant activity (TAA) and nitric oxide (NO) methods. Trans-hydroxycinnamic acids (caffeic, p-coumaric, ferulic, and sinapic) were more abundant in white grapefruit than in his hybrid. However, on a fresh weight basis, grapefruit's hybrid has a higher total phenol content as well as a higher antioxidant capacity in comparison with white grapefruit. A linear relationship existed between TAA and anthocyanins (R2=0.8068), TAA and flavonoids (R2=0.9320) and TAA and total phenols (R2=0.9446). Our findings indicate the following: (1) Both studied fruits contain a high concentration of natural antioxidants that have not only a high antioxidant activity, but also a good antioxidant quality. (2) The total phenol content and the antioxidant potential are significantly higher in the grapefruit hybrids than in white grapefruits. 相似文献
103.
Luciani Gaspar De Toledo Matheus Aparecido Dos Santos Ramos Larissa Spósito Elza Maria Castilho Fernando Rogério Pavan érica De Oliveira Lopes Guilherme Juli?o Zocolo Francisca Aliny Nunes Silva Tigressa Helena Soares André Gonzaga dos Santos Taís Maria Bauab Margarete Teresa Gottardo De Almeida 《International journal of molecular sciences》2016,17(8)
Background: The incidence of fungal infections, especially those caused by Candida yeasts, has increased over the last two decades. However, the indicated therapy for fungal control has limitations. Hence, medicinal plants have emerged as an alternative in the search for new antifungal agents as they present compounds, such as essential oils, with important biological effects. Published data demonstrate important pharmacological properties of the essential oil of Cymbopogon nardus (L.) Rendle; these include anti-tumor, anti-nociceptive, and antibacterial activities, and so an investigation of this compound against pathogenic fungi is interesting. Objective: The aim of this study was to evaluate the chemical composition and biological potential of essential oil (EO) obtained from the leaves of C. nardus focusing on its antifungal profile against Candida species. Methods: The EO was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS). Testing of the antifungal potential against standard and clinical strains was performed by determining the minimal inhibitory concentration (MIC), time-kill, inhibition of Candida albicans hyphae growth, and inhibition of mature biofilms. Additionally, the cytotoxicity was investigated by the IC50 against HepG-2 (hepatic) and MRC-5 (fibroblast) cell lines. Results: According to the chemical analysis, the main compounds of the EO were the oxygen-containing monoterpenes: citronellal, geranial, geraniol, citronellol, and neral. The results showed important antifungal potential for all strains tested with MIC values ranging from 250 to 1000 μg/mL, except for two clinical isolates of C. tropicalis (MIC > 1000 μg/mL). The time-kill assay showed that the EO inhibited the growth of the yeast and inhibited hyphal formation of C. albicans strains at concentrations ranging from 15.8 to 1000 μg/mL. Inhibition of mature biofilms of strains of C. albicans, C. krusei and C. parapsilosis occurred at a concentration of 10× MIC. The values of the IC50 for the EO were 96.6 μg/mL (HepG-2) and 33.1 μg/mL (MRC-5). Conclusion: As a major virulence mechanism is attributed to these types of infections, the EO is a promising compound to inhibit Candida species, especially considering its action against biofilm. 相似文献
104.
Daniela Nunes Rogério Colaço António Pereira Gonçalves Patrícia Almeida Carvalho 《Materials Characterization》2009,60(12):1607-1612
Magnetic domain configurations in YFe11Ti aggregates have been investigated by magnetic force microscopy. Single domain behaviour, stripe/maze domains, wavy domain structures and reverse spike domains have been observed. Domain wall energy of 6 mJ/m2 has been estimated based on the scale of the micromagnetic configurations. 相似文献
105.
106.
Zofia Kalicka 《国际钢铁研究》1991,62(4):157-163
The growth model for nuclei of oxide inclusions growing during the process of steel deoxidation is proposed. The evolution of the inclusion composition has been analysed by solving the continuity equation for the probability-density function f(x,t) (where x is the oxide mole fraction). The calculations were carried out for model parameters and for steel deoxidation by aluminium or silicon-manganese. The result obtained cannot be verified due to the lack of any functional dependence relating chemical composition to inclusion radius. 相似文献
107.
Rogério Pinto Ribeiro José Eduardo Rodrigues 《Bulletin of Engineering Geology and the Environment》2004,63(1):41-50
In this paper the drainage network is considered as a geo-indicator of the environmental changes that haven taken place over a period of 23 years in three hydrographic microbasins in the São Paulo State (Brazil). The verification of the natural conditions of the physical environment was based on terrain evaluation for homogeneity of landforms and the materials associated with them. In order to identify the alterations, a temporal analysis of the drainage network morphometric variables and land use was made. The morphometric analysis indicates a decrease in the number of first-order channels and in the total length of all channels, with a consequential modification of the drainage and hydrographic densities. The losses and gains of the first-order channels were influenced by the slope, type of bedrock and presence of unconsolidated material. The catalyst for these changes was mainly the inadequate control of urban expansion and the intensive agricultural activities.Résumé Dans cet article le réseau de drainage est considéré comme un géo-indicateur de changements environnementaux qui se sont réalisés durant 23 années dans trois micro-bassins hydrographiques de létat de Sao Paulo (Brésil). Les caractéristiques du milieu physique ont été obtenues à partir dune étude des différentes unités géomorphologiques et des formations géologiques corrélatives. Afin de mettre en évidence les modifications du milieu, une analyse temporelle de loccupation des sols et des paramètres morphométriques du réseau de drainage a été réalisée. Lanalyse morphométrique indique une diminution du nombre de sections de premier ordre et de la longueur totale du réseau de drainage. Il en résulte une modification de la densité de drainage des bassins. Les diminutions ou augmentations de sections de premier ordre ont été influencées par la pente, le type de substratum et la présence de matériaux meubles. Une expansion urbaine mal contrôlée et le développement dune agriculture intensive sont les causes de ces modifications. 相似文献
108.
109.
The aim of the work was to evaluate the amino acid composition of fresh spinach and spinach products prepared for consumption. The investigation included fresh and cooked spinach and two kinds of frozen product: one obtained using the traditional method (blanching-freezing-refrigerated storage) and then cooked; and the other, of the ready-to-eat type, obtained using the modified method (cooking-freezing-refrigerated storage) and then prepared for consumption in a microwave oven. In 100 g of edible parts of the as-eaten products, the content of amino acids exceeded that in the raw material from which they were obtained, except for sulphur amino acids and tyrosine. In the as-eaten products, the content of amino acids in protein calculated in 16 g N was similar to that in the raw material, except for lower tyrosine and higher arginine content in the traditional frozen product prepared for consumption. Cystine with methionine was the amino acid limiting the quality of protein in the investigated samples, except for the traditional frozen product prepared for consumption, where the Chemical Score (CS) index was 100. 相似文献
110.
Giovanni Venâncio Rogério C. Turchetti Edson T. Camargo Elias P. Duarte Jr 《International Journal of Network Management》2021,31(3):e2124
Software-defined networks (SDN) usually rely on a centralized controller, which has limited availability and scalability by definition. Although a solution is to employ a distributed control plane, the main issue with this approach is how to maintain the consistency among multiple controllers. Consistency should be achieved with as low impact on network performance as possible and should be transparent for controllers, without requiring any change of the SDN protocols. In this work, we propose VNF-Consensus, a virtual network function that implements Paxos to ensure strong consistency among controllers of a distributed control plane. In our solution, controllers can perform their control plane activities without having to execute the expensive tasks required to keep consistency. Experimental results are presented showing the cost and benefits of the proposed solution, in particular in terms of low controller overhead. 相似文献