全文获取类型
收费全文 | 105篇 |
免费 | 8篇 |
专业分类
化学工业 | 36篇 |
金属工艺 | 4篇 |
建筑科学 | 2篇 |
能源动力 | 1篇 |
轻工业 | 5篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 11篇 |
一般工业技术 | 20篇 |
冶金工业 | 23篇 |
自动化技术 | 9篇 |
出版年
2024年 | 3篇 |
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 7篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 6篇 |
2012年 | 6篇 |
2011年 | 6篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 1篇 |
2002年 | 3篇 |
2000年 | 1篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1980年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有113条查询结果,搜索用时 140 毫秒
21.
22.
S.B. Alemán-Córdova L. Ceja-Cárdenas J.C. Méndez-García S. Díaz-de la Torre 《Ceramics International》2021,47(6):7966-7973
The simultaneous extrusion and sintering of ceramic materials using the spark plasma extrusion (SPE) technique is an alternative densification route for the powders examined in this study. SPE with Y2O3 and Al2O3 as the additives was employed for the concurrent densification and extrusion of pure α-Si3N4 commercial powder. Three compositions of α-Si3N4 powders, namely SN-4, SN-12, and SN-20, were studied to understand the effect of additives on the sinter-extrusion process. The number in the mixture name corresponded to the weight percentage of additives in the samples. A mechanical shaker was used to thoroughly mix the selected powder compositions in isopropanol for 24 h at 720 rpm. It was then dried in a furnace at 100 °C for 3 h. The sinter-extrusion treatment was conducted for a holding time of 5 min at a heating rate of 300 °C/min and a sintering temperature of 1500 °C with a pressure in the range of 12–63 MPa. The maximum degree of extrusion was attained when the total amount of additives was at 20 wt% (SN-20 series). As the total amount of additives increased, the capillary pressure gradients led to an inhomogeneous liquid distribution throughout the specimen, which in turn promoted further densification of the Si3N4 ceramics. Owing to the conical geometry of the graphite die used for the extrusion process in this study, the largest densification values observed in the extruded ceramics corresponded to the base and the middle sections of the SN-20 series (relative density ~92%). The latter could only take place once the α-to β-Si3N4 phase transformation occurred, leading to significant shrinkage of the material. 相似文献
23.
Variational inequality minimization (VIM) theory of statistical mechanics is used to derive analytic equations of state for nonpolar fluids. Pair- and tripletintermolecular potential energy functions are taken into account in the formulation of this equation of state. The VIM theory has made it possible to derive rather simple expressions for the thermodynamic properties of nonpolar fluids. Predictions of the thermodynamic properties of argon and methane in the liquid phase, in the vapor phase, and in the critical region by the VIM equation of state are shown to be in excellent agreement with the experimental data. 相似文献
24.
Ortiz E Alemón E Romero D Arriaga JL Olaya P Guzmán F Rios C 《The Science of the total environment》2002,287(3):241-248
The Mexico City Metropolitan Zone (ZMCM) population's exposure to benzene, toluene and xylene was measured at different microenvironments to establish basic indicators of the presence and effects of these characteristic volatile organic compounds (VOC). In particular, VOC personal exposures were measured in different microenvironments during a 5-day working week, with 12-h daily periods. We have found a good agreement of our results with the registered VOC levels of the Metropolitan Automated Monitor System (RAMA) for the corresponding period. From our results, we expect to generate useful information to evaluate the health effects of these VOCs on exposed people. 相似文献
25.
Iliyan Kolev Gergana Alexieva Vesselin Strashilov Ismail Ben Youssef Frederic Sarry Halima Alem 《应用聚合物科学杂志》2016,133(48)
The sensitivity of a thick layer (500 nm) of poly(urethaneimide) to toxic gases such as pyridine and hexamethyleneimine was studied by the quartz crystal microbalance method. The resonant frequency was registered by a spectrum analyzer. The successful overcoming of the unfavorable impact of the increased viscous damping, typical for the standard oscillator measurement method, allowed complete understanding of the behavior of a thick polymer layer toward highly pollutant gases. Quantitative information for polymer adsorption capacity and gas diffusivity was extracted. The comparison with our recent results for thinner layers revealed strong dependence on layer thickness for pyridine whereas the corresponding effect with hexamethyleneimine was found much less significant. Intermolecular interactions and the impact of the gas physical adsorption on the polymer matrix properties were shown as the driving parameters for the sensors response. The thickness dependence provides a tool for tuning the sensitivity of a potentially efficient poly(urethaneimide) sensor for pyridine. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44214. 相似文献
26.
Hubert Alem Peggy Rigou Rémi Schneider Hernán Ojeda Laurent Torregrosa 《Journal of the science of food and agriculture》2019,99(3):975-985
Aroma compounds are secondary metabolites that play a key role in grape quality for enological purposes. Terpenes, C13-norisoprenoids, phenols, and non-terpenic alcohols are the most important aroma compounds in grapes and they can be found as free volatiles or glycoconjugated (bound) molecules. The non-volatile glycosylated group is the largest, and it is present in all varieties of Vitis vinifera (L.), the most widely used species for wine production. These aroma precursors represent the reserve of aroma molecules that can be released during winemaking. Their relative and absolute concentrations at fruit ripening determine the organoleptic value of the final product. A large range of biotic and abiotic factors can influence their biosynthesis in several ways. Agronomic practices such as irrigation, training systems, leaf removal, and bunch thinning can have an effect at plant level. The spraying of stimulatory compounds on fruit at different developmental stages has also been shown to modify metabolic pathways at fruit level with some impact on the aroma composition of the grapevine fruit. Viticulturists could act to promote aroma precursors to improve the aromatic profile of grapes and the wine ultimately produced. However, agronomic practices do not always have uniform results. The metabolic and physiological changes resulting from agronomic practices are unknown because there has not been sufficient research to date. This review presents the state of the art regarding the influences of vineyard agronomic management on the biosynthesis of grape aroma compounds. Although literature regarding the topic is abundant there are still many unknown biological mechanisms involved and/or that have been insufficiently studied. The aim of this work is therefore to find the gaps in scientific literature so that future investigations can focus on them. © 2018 Society of Chemical Industry 相似文献
27.
28.
Ramírez E Valencia ME Moya Camarena SY Alemán-Mateo H Méndez RO 《Archivos latinoamericanos de nutrición》2010,60(3):240-246
The objective of this study was to validate the estimation of body fat (%BF) by DXA (Dual-Energy X-Ray AbsorciomDPX-MD) against the four compartment model (4C) of body composition in 32 Mexican pubertal girls and boys (aged 9-14 y; F=16). The mean of the difference between DXA and 4C model was -3.5 %BF (p=0.171). The limits of agreement (95% = 2 SD) were +5% to -12%BF. The precision of estimated limits of y the confidence intervals were -1.9% to -5.1%BF (P = 0.050). The concordance correlation coefficient was p = 0.85. The test of accuracy for coincidence of slop intercepts between DXA and the 4C model showed no coincidence (p < 0.05). The precision by R2 explained 83% of the variance (SEE, 4.1%). The individual accuracy assess by the total error was 5.6%. The group mean accuracy by two way analysis of variance of body fat did not show interaction between method (DXA-4C model) and separate analysis of gender and overweight. However, there was an effect of method (p = 0.043) in the presence of overweight (p < 0.001). In conclusion, the estimation of percent of body fat by DXA was not precise and accurate in a group of Mexican children. However, results do not limit the utility of DXA for the measurements of body composition and its relation with health outcomes, especially in follow up studies. 相似文献
29.
Ramírez Pereda A Pacheco BI Astiazarán-García H Esparza-Romero J Alemán-Mateo H 《Archivos latinoamericanos de nutrición》2006,56(2):135-140
Vitamin B12 and folate deficiencies are the main nutritional determinants of hyperhomocysteinemia, which is an independent risk factor for cardiovascular diseases. There is scarce information about nutritional status on vitamin B12 and serum levels of folate in Mexican older people. The objective was to evaluate the nutritional status of vitamin B12 and folic acid concentration in non-institutionalized, urban elderly men and women subjects. One hundred volunteers over 60 years were included in this cross-sectional study. Serum levels of vitamin B12 and folate were measured. In addition some biochemical and anthropometric indicators were also evaluated. Considering serum values of vitamin, 30% had vitamin B12 deficiency, 52% normal status and 18% with high levels. None subjects had folic acid deficiency, by the contrary, a high proportion (62%) showed elevated levels in serum. There was an effect of sex on vitamin B12 status. Elderly men showed significantly lower levels of vitamin B12, and it was according with significant higher prevalence of vitamin B12 deficiency in this group as compared with the women group. The high proportion of vitamin B12 deficiency found in this study underline a possible public health problem and guarantee further survey-studies about vitamin B12 status and to explore causes and consequences of the deficiency. Finally, due the sample size and the design of the study, the results must be seen with caution and not try to generalize. 相似文献
30.
Sustainable Solid‐State Supercapacitors Made of 3D‐Poly(3,4‐ethylenedioxythiophene) and κ‐Carrageenan Biohydrogel 下载免费PDF全文
Georgina Fabregat L'udmila Hodásová Luis J. del Valle Francesc Estrany Carlos Alemán 《Advanced Engineering Materials》2018,20(7)