全文获取类型
收费全文 | 907篇 |
免费 | 106篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 286篇 |
金属工艺 | 17篇 |
机械仪表 | 20篇 |
建筑科学 | 40篇 |
能源动力 | 20篇 |
轻工业 | 196篇 |
水利工程 | 7篇 |
石油天然气 | 2篇 |
武器工业 | 3篇 |
无线电 | 52篇 |
一般工业技术 | 170篇 |
冶金工业 | 65篇 |
自动化技术 | 135篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 7篇 |
2021年 | 19篇 |
2020年 | 21篇 |
2019年 | 31篇 |
2018年 | 48篇 |
2017年 | 30篇 |
2016年 | 50篇 |
2015年 | 45篇 |
2014年 | 40篇 |
2013年 | 100篇 |
2012年 | 75篇 |
2011年 | 48篇 |
2010年 | 57篇 |
2009年 | 54篇 |
2008年 | 46篇 |
2007年 | 46篇 |
2006年 | 37篇 |
2005年 | 19篇 |
2004年 | 20篇 |
2003年 | 13篇 |
2002年 | 14篇 |
2001年 | 16篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 25篇 |
1997年 | 13篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1913年 | 1篇 |
排序方式: 共有1018条查询结果,搜索用时 15 毫秒
91.
Ofelia G. Meza‐Márquez Tzayhrí Gallardo‐Velázquez Guillermo Osorio‐Revilla Lidia Dorantes‐Álvarez 《International Journal of Food Science & Technology》2012,47(11):2342-2351
Mid‐infrared spectroscopy (FT‐Mid IR) coupled with multivariate analysis was used to predict clenbuterol in beef meat, liver and kidney. A SIMCA model was also developed to discriminate between pure (beef meat, liver and kidney) and spiked with clenbuterol samples (beef meat‐clenbuterol, liver‐clenbuterol and kidney‐clenbuterol). The best models to predict clenbuterol concentrations were obtained using the partial least squares algorithm (PLS) with a R2 > 0.9 and SEC and standard error of prediction <0.296 and 0.324, respectively. The SIMCA model used to discriminate pure and spiked with clenbuterol samples showed 100% correct classification rate. Methods detection limit was 2 μg kg?1. FT‐Mid IR coupled with chemometrics could be a simple and rapid screening tool for monitoring clenbuterol in beef meat, liver and kidney implicated in food poisoning. This method could be use for screening purposes. 相似文献
92.
Catalytic wet oxidation has proved to be effective at eliminating hazardous organic compounds, such as phenol, from waste waters. However, the lack of active long-life oxidation catalysts which can perform in aqueous phase is its main drawback. This study explores the ability of bimetallic supported catalysts to oxidize aqueous phenol solutions using air as oxidant. Combinations of 2% of CoO, Fe2O3, MnO or ZnO with 10% CuO were supported on gamma-alumina by pore filling, calcined and later tested. The oxidation was carried out in a packed bed reactor operating in trickle flow regime at 140 degrees C and 900 kPa of oxygen partial pressure. Lifetime tests were conducted for 8 days. The pH of the feed solution was also varied. The results show that all the catalysts tested undergo severe deactivation during the first 2 days of operation. Later, the catalysts present steady activity until the end of the test. The highest residual phenol conversion was obtained for the ZnO-CuO, which was significantly higher than that obtained with the 10% CuO catalyst used as reference. The catalyst deactivation is related to the dissolution of the metal oxides from the catalyst surface due to the acidic reaction conditions. Generally, the performance of the catalysts was better when the pH of the feed solution was increased. 相似文献
93.
The acid-catalyzed decomposition of unusually stable 1-(2,1-benzisothiazol-3-yl)-3-phenyltriazenes in either aqueous perchloric acid or an aqueous mixture of perchloric and acetic acid was studied under pseudo-first order reaction conditions at 25 °C. Different products were obtained according to substitution on nitrogen N-3. For a triazene carrying hydrogen, the corresponding 3-amino-2,1-benzisothiazole and benzenediazonium salts were formed whereas in the case of substitution by an alkyl group (methyl and n-butyl) the 2,1-benzisothiazole-3-diazonium salt and N-alkylaniline were obtained. The observed rate constant (kobs) of the acid-catalyzed decomposition increased, initially, nonlinearly with increasing concentration of acid. Subsequently, kobs decreased slightly and at high acid concentration, increased steeply once again. An A-SE2 mechanism in which protonation of the triazene nitrogen proceeds simultaneously with cleavage of the N–N bond is proposed. Tautomerism of 1-(2,1-benzisothiazol-3-yl)-3-phenyltriazene was investigated using 1H NMR spectroscopy. 相似文献
94.
This paper deals with the environmental bill of material and technology routing: evaluating components and process impacts
on the environmental strategy map through an integrated LCA approach. It introduces these two new elements in the definition
of new approaches to complement environmental and financial considerations into a single sustainability indicator. The basic
idea presented is that each component of a specific product has a certain environmental burden and consequently contributes
to the environmental footprints. Those contributions are identified as environmental performance points (EPP). When an item
is routed through different technology processes to build the final product, it keeps contributing to the overall environmental
burden. These contributions are again identified as EPP. The sum of all EPPs, categorized by footprints, provides the basis
for creation of the characteristic environmental performance strategy map, previously developed by the authors of this paper.
This new approach allows wide flexibility: the impact of changing a component, material or a production process will be reflected
immediately on the map. 相似文献
95.
96.
Petr Ptáček Tomáš Opravil František Šoukal Jaromír Wasserbauer Jiří Másilko Jan Baráček 《Journal of the European Ceramic Society》2013,33(13-14):2793-2799
The structural order of kaolinite is an important factor that shows a substantial effect on the processes which take place during the thermal treatment of kaolin. The influence of structural order on the dehydroxylation process was investigated by simultaneous thermogravimetry and differential thermal analysis (TG-DTA). The thermal analysis was performed on the samples with gradually decreasing structural order prepared by milling procedure. The apparent activation energy of dehydroxylation process decreases with decreasing structural order according to the exponential function. The extrapolation of experimental data leads to the estimation of apparent activation energy of 76.6 kJ mol?1 and of frequency factor of 0.12 × 104 s?1 related to completely disordered form of kaolinite, while the ordered form shows the apparent activation energy of 216.17 kJ mol?1 and the frequency factor of 9.26 × 104 s?1. The relationships between features such as the infrared pattern of treated material, the degree of structural order and the apparent activation energy were established. 相似文献
97.
The significance of reliability, availability and maintainability (RAM) in recent years increased due to rising energy cost and the competitive market. These issues have a considerable effect on the energy generation and potential saving as well. RAM can be assessed by implementing effective software tools generating adequate models. They also provide results visualization via a tabular and/or graphical representation. Various software tools have been selected, tested and a brief overview drawn. It has been a wide selection; however, most of the information available has been driven by marketing and sales features. This work focuses on the main features of several promising complex reliability packages and its target is a balanced assessment of their main features. 相似文献
98.
Talita A. Comunian Ednelí S. Monterrey‐Quintero Marcelo Thomazini Julio C. C. Balieiro Pierpaolo Piccone Paola Pittia Carmen S. Favaro‐Trindade 《International Journal of Food Science & Technology》2011,46(6):1259-1265
The aim of this research was to study spray drying as potential action to protect chlorophyllide from environmental conditions for shelf‐life extension and characterisation of the powders. Six formulations were prepared with 7.5 and 10 g of carrier agents [gum Arabic (GA), maltodextrin (MA) and soybean protein isolate (SPI)]/100 mL of chlorophyllide solutions. The powders were evaluated for morphological characteristics (SEM), particle size, water activity, moisture, density, hygroscopicity, cold water solubility, sorption isotherms, colour and stability, during 90 days. All the powders were highly soluble, with solubility values around 97%. A significant lower hygroscopicity was observed for GA powders, whilst the lower Xm values obtained by GAB equation fitting of the sorption isotherms was observed for the 7.5 g MA/100 mL samples. All formulations, but the 1 (7.5 g SPI/100 mL of chlorophyllide), provided excellent stability to the chlorophyllide during 90 days of storage even at room temperature. 相似文献
99.
100.
Agustín Gualco Hernán G. Svoboda Estela S. Surian Luis A. de Vedia 《Welding International》2013,27(4):258-265
The effect of different post-weld heat treatments on the microstructure and wear resistance of martensitic deposits were studied. The deposit was welded using a metal-cored tubular wire, in the flat welding position, on a 375 × 75 × 19 mm SAE 1010 plate, using 98% Ar–2% CO2 shielding gas mixture and with an average heat input of 2.8 kJ/mm. The samples were heat treated at temperatures between 500 and 680°C for 2 h. Chemical composition, Vicker's microhardness and wear properties with AMSLER tests in a sliding condition were determined. In the as welded condition, the microstructure was principally composed of martensite and retained austenite. Significant variations in wear resistance and hardness were measured for different tempering temperatures. For the different heat-treated conditions, it was observed that the decomposition of retained austenite to martensite and carbide precipitation was associated with the tempering of martensite. A secondary hardness effect was detected with maximum hardness of 710 HV for 550°C heat treatment temperature. The best performance in wear test was obtained for this condition. Wear rates for the different conditions were obtained and mathematical expressions were developed. For each case, wear mechanisms were analyzed. 相似文献