全文获取类型
收费全文 | 429篇 |
免费 | 33篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 104篇 |
金属工艺 | 13篇 |
机械仪表 | 9篇 |
建筑科学 | 16篇 |
能源动力 | 23篇 |
轻工业 | 66篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 14篇 |
一般工业技术 | 68篇 |
冶金工业 | 89篇 |
原子能技术 | 3篇 |
自动化技术 | 47篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 13篇 |
2020年 | 8篇 |
2019年 | 6篇 |
2018年 | 18篇 |
2017年 | 21篇 |
2016年 | 14篇 |
2015年 | 14篇 |
2014年 | 21篇 |
2013年 | 31篇 |
2012年 | 18篇 |
2011年 | 22篇 |
2010年 | 29篇 |
2009年 | 23篇 |
2008年 | 19篇 |
2007年 | 20篇 |
2006年 | 16篇 |
2005年 | 12篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 12篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1998年 | 24篇 |
1997年 | 23篇 |
1996年 | 18篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有464条查询结果,搜索用时 78 毫秒
41.
42.
Salvador?Jiménez-García Carlos?Santiago?López-Cajún Rosalba?Fuentes Victor?M.?Casta?oEmail author 《Materials Research Innovations》2003,7(4):199-204
Aluminium-based matrix composites were prepared by infiltration with an ammoniacal zirconium chelate within an Al matrix synthesized via Aluminium powder compactation. After infiltration, this chelate can be transformed in situ by sol-gel method that leads to tetragonal phases in zirconia, which in turn, transforms to monoclinic structure on heating. Based on Differential Thermal Analysis (DTA), Fourier Transformed Infrared (FTIR), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM), we confirm the reaction sequence to obtain the tetramer, the phase transformation sequence within the Al matrix, and the development of phases that leads to the synthesis of the Al-ZrO2 composite. 相似文献
43.
R. Gutiérrez Fuentes J. F. Sánchez Ramírez J. L. Jiménez Pérez J. A. Pescador Rojas E. Ramón-Gallegos A. Cruz-Orea 《International Journal of Thermophysics》2007,28(3):1048-1055
Nanoparticles appear to be ideally suited for applications in targeted thermal effects in medical therapies and photothermally
activated drug delivery; all depend critically on the thermal transport between the nanoparticles and the surrounding liquid.
In this work thermal lens spectroscopy (TLS) was used to determine the thermal diffusivity of protoporphyrin IX (PpIX) solutions
mixed with gold metallic nanoparticles. PpIX disodium salt (DS) was used in a HCl solution at 25%. Fluids containing gold
(Au) nanoparticles at different concentrations were prepared and added to the PpIX solutions. For each solution, UV–Vis spectroscopy
was used to obtain the optical absorption spectrum, and transmission electron microscopy (TEM) was used to obtain the gold
nanoparticle size. From the TLS signal intensity, it was possible to determine the characteristic time constant of the transient
thermal by fitting the theoretical expression to the experimental data. From this characteristic time, the thermal diffusivity
was obtained for each solution. The results show that the thermal diffusivity of PpIX mixed with gold nanoparticles increases
with an increase of the nanoparticle metallic concentration. 相似文献
44.
Amparo Martínez‐Fuentes Carlos Mesejo Carmina Reig Manuel Agustí 《Journal of the science of food and agriculture》2010,90(11):1936-1943
BACKGROUND: In Citrus the inhibitory effect of fruit on flower formation is the main cause of alternate bearing. Although there are some studies reporting the effect on flowering of the time of fruit removal in a well‐defined stage of fruit development, few have investigated the effect throughout the entire fruit growth stage from early fruitlet growth to fruit maturity. The objective of this study was to determine the phenological fruit developmental stage at which the fruit begins its inhibitory effect on flowering in sweet orange by manual removal of fruits, and the role of carbohydrates and nitrogen in the process. RESULTS: Fruit exerted its inhibitory effect from the time it was close to reaching its maximum weight, namely 90% of its final size (November) in the present experiments, to bud sprouting (April). The reduction in flowering paralleled the reduction in bud sprouting. This reduction was due to a decrease in the number of generative sprouted buds, whereas mixed‐typed shoots were largely independent of the time of fruit removal, and vegetative shoots increased in frequency. The number of leaves and/or flowers per sprouted shoot was not significantly modified by fruit load. CONCLUSION: In ‘Valencia’ sweet orange, fruit inhibits flowering from the time it completes its growth. Neither soluble sugar content nor starch accumulation in leaves due to fruit removal was related to flowering intensity, but some kind of imbalance in nitrogen metabolism was observed in trees tending to flower scarcely. Copyright © 2010 Society of Chemical Industry 相似文献
45.
Julio Alberto Solís‐Fuentes María del RosarioHernndez‐Medel María del CarmenDurn‐de‐Bazúa 《European Journal of Lipid Science and Technology》2005,107(6):395-401
In this paper, some important properties, from the application point of view, of mango (Mangifera indica) almond fat var. Manila (MAF) were analyzed by differential scanning calorimetry and X‐ray diffraction techniques. The thermal profile, the solid fat content (SFC) and the predominant polymorphism of MAF samples, previously characterized chemically, were studied. The results showed that this fat, from one of the main residues of mango industrialization, had a relatively simple fusion/crystallization behavior. Stabilized samples showed a simple SFC profile with one marked slope between 35 and 40 °C. Different thermal histories demonstrated the existence of at least four polymorphs. The non‐stabilized samples corresponded predominantly to the formation of the crystalline &α form. The stabilized samples, tested under several time and temperature conditions, allowed the formation of two other polymorphs, which are both unstable forms and were formed during &α to β polymorphic transition. The X‐ray diffraction information confirmed the presence of the less and more stable MAF polymorphs, allowing us to conclude that MAF is a β‐stable fat, just as is cocoa butter. 相似文献
46.
M Giovannini JF Seitz P Thomas JM Hannoun-Levy H Perrier M Resbeut JR Delpero P Fuentes 《Canadian Metallurgical Quarterly》1997,29(1):4-9
The current classification of cutaneous melanoma was developed in 1972 and revised in 1982. Since that time new concepts and terminology have evolved that require consideration of a further revision. This paper reviews some of the concepts that will form part of that process. Regional meetings of interested parties have been held to review the classification and there will be an open meeting on the topic at the 1997, 4th World Conference on Melanoma in Sydney, Australia. A questionnaire is included that will allow the interested reader to provide comments on the topic. 相似文献
47.
48.
Recent evidence has shown that inhibition of return, IOR, is impaired in patients with parietal damage with or without clinical signs of neglect (Bartolomeo, Sieroff, Decaix, & Chokron, 2001; Vivas, Humphreys, & Fuentes, 2003, respectively). In addition to environment-based IOR, Tipper et al. (1991) showed that IOR could be also associated with dynamic, object-based representations. In our study, we examined four patients with unilateral lesions to the parietal lobe, and a group of healthy controls, in an IOR procedure with moving objects where a pre-cued object could move, clockwise or counterclockwise, 90° in polar coordinates. The group of control participants showed a small but significant object-based IOR effect. In contrast, the patients showed an object-based IOR effect when the objects moved from the contralesional field toward the ipsilesional field, whereas there was no IOR effect when they moved from the ipsilesional to the contralesional field. These findings are discussed in terms of the role of the parietal cortex in implementing attentional biases in both environment-based (Vivas et al., 2003) and object-based frames of reference. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
49.
The desiccating effects of two different types of diatomaceous earths (DEs), of freshwater and marine origin, applied by two different methods, were compared on four species of insects, Cryptolestes ferrugineus, Rhyzopertha dominica, Sitophilus oryzae and Sitophilus granarius. The purpose was to investigate the performance of DEs, including their abrasive and absorptive effects through the accumulation of silica dusts on the insect cuticle, resulting in death of the insects by desiccation. The data obtained showed that similar insects treated with the same type of diatom, but applied either by spraying or dusting, did not have the same initial mortality rate.
After examining and comparing the data obtained, it appeared that weight loss at death of insects subjected to the action of sprayed DEs was slightly less than for insects subjected to dust application, while mortality was slightly more rapid during the observation period. The extra weight of dusted insects was ascribed to greater adherence of dust particles to the treated insects. 相似文献
50.
José Luis García-Gutiérrez Gustavo A. Fuentes Maria Eugenia Hernández-Terán Ponciano García Florentino Murrieta-Guevara Federico Jiménez-Cruz 《Applied Catalysis A: General》2008,334(1-2):366-373
This work presents the results obtained in the development of Mo/γ-Al2O3 catalysts and their evaluation in the oxidative desulfurization (OD) process of diesel fuel using hydrogen peroxide as the oxidizing reagent. The catalysts were prepared by equilibrium adsorption using several molybdenum precursors and aluminas with different acidity values. They were characterized by Raman spectroscopy. The effect of the reaction time, reaction temperature, nature of solvent, concentration of solvent and hydrogen peroxide, content of molybdenum and phosphate in the catalysts were investigated. The results showed that the activity for sulfur elimination depends mainly on the presence of hepta- and octamolybdates species on the catalyst support and the use of a polar aprotic solvent. Likewise, the presence of phosphate markedly increases the sulfur elimination. In this way, it is possible to reduce sulfur level in diesel fuel from about 320 to less than 10 ppmw at 333 K and atmospheric pressure. Additionally, on the basis of the results obtained a mechanistic proposal for this reaction is described, as an oxidation mechanism by nucleophilic attack of the sulfur atom on peroxo species of hepta- and octamolybdates, but a mechanism involving the singlet oxygen presence can be discarded. 相似文献