全文获取类型
收费全文 | 2710篇 |
免费 | 212篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 837篇 |
金属工艺 | 15篇 |
机械仪表 | 41篇 |
建筑科学 | 79篇 |
矿业工程 | 1篇 |
能源动力 | 67篇 |
轻工业 | 932篇 |
水利工程 | 17篇 |
石油天然气 | 18篇 |
无线电 | 122篇 |
一般工业技术 | 339篇 |
冶金工业 | 221篇 |
原子能技术 | 22篇 |
自动化技术 | 199篇 |
出版年
2024年 | 3篇 |
2023年 | 41篇 |
2022年 | 96篇 |
2021年 | 102篇 |
2020年 | 69篇 |
2019年 | 68篇 |
2018年 | 99篇 |
2017年 | 69篇 |
2016年 | 106篇 |
2015年 | 78篇 |
2014年 | 129篇 |
2013年 | 202篇 |
2012年 | 190篇 |
2011年 | 177篇 |
2010年 | 145篇 |
2009年 | 167篇 |
2008年 | 161篇 |
2007年 | 148篇 |
2006年 | 108篇 |
2005年 | 94篇 |
2004年 | 60篇 |
2003年 | 62篇 |
2002年 | 73篇 |
2001年 | 42篇 |
2000年 | 36篇 |
1999年 | 44篇 |
1998年 | 96篇 |
1997年 | 53篇 |
1996年 | 43篇 |
1995年 | 30篇 |
1994年 | 20篇 |
1993年 | 20篇 |
1992年 | 14篇 |
1991年 | 11篇 |
1990年 | 5篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1964年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有2923条查询结果,搜索用时 17 毫秒
101.
Mercedes Álvarez Isabel M. Moreno Silvia Pichardo Ana M. Cameán A. Gustavo González 《Food chemistry》2012
Fifty wines from the Denomination of origin (DO) of Condado de Huelva were analysed for mineral content by measuring 12 elements (Al, Ba, Ca, Cu, Fe, K, Mg, Mn, Na, P, Sr and Zn) using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Samples were previously digested by heating with H2O2/HNO3 mixture. The results obtained showed that metal data set were non-normally distributed and accordingly, non-parametric statistics were applied. The average levels (medians) of these elements found in the samples are as follows, in mg/L: 2.54 (Al); 0.06 (Ba); 82.58 (Ca); 0.21 (Cu); 3.53 (Fe); 865.34 (K); 68.87 (Mg); 0.71 (Mn); 32.77 (Na); 71.61 (P); 0.48 (Sr); 0.56 (Zn). The interrelation of metal couples was studied through the Spearman non-parametric sample correlation, being Fe/Al, P/Mg, and Zn/Ba the most important correlations established. As a result of this study, we can suggest that the contribution to the safety intake limits (per week) of the studied elements through the wine consumption is not significant. Actually, they range between 0.1% in Fe and 11.9% in Mg, for normal drinkers. 相似文献
102.
Pinela J Barros L Dueñas M Carvalho AM Santos-Buelga C Ferreira IC 《Food chemistry》2012,135(3):1028-1035
The antioxidant activity and phytochemical composition (ascorbic acid, free sugars and phenolic compounds) of decoctions and infusions of wild and commercial samples of Tuberaria lignosa (Sweet) Samp. Aerial parts were evaluated and compared. Among wild samples, the effects of the drying method (freeze or shade-drying) on those parameters were studied. Infusion of the freeze-dried wild sample gave the highest levels of sugars, while infusion of shade-dried wild sample and decoction of the freeze-dried sample presented higher ascorbic acid and phenolic compounds content (including ellagitannins and flavonoids) than the other samples. The last two samples also revealed higher antioxidant activity, in some cases even higher than Trolox. Decoctions gave lower amounts of disaccharides than infusions, which seemed to be hydrolysed, increasing the content of monosaccharides. Commercial samples showed the lowest content in phenolic compounds, mainly in ellagitannins and flavonoids, and also the lowest antioxidant activity. This work gives scientific evidence to the traditional medicinal uses of wild Tuberaria lignosa, highlighting the interest of its decoctions and infusions as a source of bioactive compounds and functional beverages. 相似文献
103.
Muniain-Mujika I Girones R Tofiño-Quesada G Calvo M Lucena F 《International journal of food microbiology》2002,77(1-2):125-133
The consumption of shellfish has been associated with viral infections even in cases where shellfish complied with the current regulation, which is based on bacterial analysis. In this study, depuration rates of potential indicators and human viruses have been analysed in order to study the use of complementary parameters for evaluating the microbiological quality of depurated shellfish. Depuration of naturally highly polluted mussels has been evaluated and analyses for Escherichia coli, Clostridium perfringens, somatic coliphages, F-RNA phages and bacteriophages infecting Bacteroides fragilis RYC2056 and HSP40, human adenovirus, enterovirus have been done. Seawater of the depuration tank was disinfected by UV irradiation, ozone and passed through a skimmer and a biological filter. The correct functioning of the depuration tank was monitored by the quantification of total organic carbon (TOC), NH4+ and total aerobic bacteria in the seawater. To study the relation between the bacteriophages and the human viruses analysed, a logistic regression model was applied. F-RNA phages are significantly related to human adenoviruses and enteroviruses. Thus, they can be used as a complementary parameter for evaluating the efficiency of the depuration treatment. Somatic coliphages are also significantly associated with enteroviruses. Bacteriophages infecting B. fragilis HSP40 were analysed by the double-agar-layer (DAL) method, which quantifies infectious viruses, and by nested PCR, which detects the presence of the genome of these phages. The highest sensitivity of the molecular techniques was demonstrated and the results obtained are an indicator of a close relation between positive results by PCR and the presence of infectious viral particles in shellfish. All shellfish samples were negative for human viruses by PCR after 5 days of depuration treatment and the results obtained applying a regression model also showed negative results or nearly for F-RNA phages and bacteriophages infecting B. fragilis RYC2056. Thus, in this specific depuration treatment, 5 days may be necessary to assess the sanitary quality of shellfish. 相似文献
104.
Ana Isabel Rodríguez-Bernaldo De Quirós Julia López-Hernández María José González-Castro Carlos De la Cruz-García Jesús Simal-Lozano 《European Food Research and Technology》2000,210(3):226-230
The effects of four culinary treatments (steaming and boiling in a covered pot, a pressure cooker or a microwave oven) on
the volatile component profile of green beans were evaluated. Volatile compounds in raw and cooked beans were analysed by
means of dynamic headspace sampling onto an adsorbent, followed by microwave desorption into a gas chromatograph equipped
with a mass spectrometric detector. Twenty-seven compounds were identified, including alcohols, aldehydes, ketones, esters,
terpenes, sulphur compounds and alkenes. All of the thermal treatments caused important changes in the volatile compound profile
in particular an increase in carbonyl compounds and a decrease in alcohol compounds, most notably in the case of the covered
pot. It is concluded that the change in aroma during the cooking of green beans depends on compounds from lipid oxidation
as well as compounds from other types of reactions, for instance the Strecker degradation.
Received: 8 March 1999 / Revised version: 23 April 1999 相似文献
105.
Isabel Odriozola‐Serrano Robert Soliva‐Fortuny Olga Martín‐Belloso 《Journal of the science of food and agriculture》2008,88(15):2606-2614
BACKGROUND: The feasibility of using modified atmosphere packaging (5 kPa O2 + 5 kPa CO2) to maintain the antioxidant properties of fresh‐cut tomatoes during shelf‐life was assessed through storage at different temperatures (5, 10, 15 and 20 °C). Health‐related compounds, antioxidant capacity, microbiological counts, physicochemical parameters and in‐package atmosphere of tomato slices were determined. RESULTS: Initial lycopene, vitamin C and phenolic contents and physicochemical parameters of tomato slices were well maintained for 14 days at 5 °C. Lycopene and total phenolic contents were enhanced over time in tomato slices stored at 15 and 20 °C. However, this increase in antioxidant compounds of fresh‐cut tomatoes during storage may be associated with excessive amounts of CO2 (R2 = 0.5679–0.7328) in the packages due to microbial growth. Although keeping tomato slices at temperatures above 10 °C increased their antioxidant content, the shelf‐life of the product was reduced by up 4 days. CONCLUSIONS: A storage temperature of 5 °C is appropriate for maintaining the microbiological shelf‐life of fresh‐cut tomatoes for up to 14 days and also allows the antioxidant properties of tomato slices to be retained over this period, thus reducing wounding stress and deteriorative changes. Copyright © 2008 Society of Chemical Industry 相似文献
106.
107.
Octávio P. Dias Isabel C. Teixeira J. Paulo Teixeira 《Journal of Electronic Testing》1999,14(1-2):149-158
The purpose of this paper is to present a novel methodology for assessing the quality of architecture solutions of hw/sw systems, with particular emphasis on testability. Criteria and metrics for quality assessment are proposed and used to assist the design team in selecting a best-fitted architecture that satisfies not only functional requirements, but also test requirements. The methodology makes use of object-oriented modeling techniques. Near-optimum clustering of methods and attributes into objects is carried out, in such a way that objects with moderate complexity, low coupling and high functional autonomy, result. The main features of the methodology are ascertained through a case study. 相似文献
108.
Rodrigo F. P. Martins Arman Ahnood Nuno Correia Luís M. N. P. Pereira Raquel Barros Pedro M. C. B. Barquinha Ricardo Costa Isabel M. M. Ferreira Arokia Nathan Elvira E. M. C. Fortunato 《Advanced functional materials》2013,23(17):2153-2161
The ability to process and dimensionally scale field‐effect transistors with and on paper and to integrate them as a core component for low‐power‐consumption analog and digital circuits is demonstrated. Low‐temperature‐processed p‐ and n‐channel integrated oxide thin‐film transistors in the complementary metal oxide semiconductor (CMOS) inverter architecture are seamlessly layered on mechanically flexible, low‐cost, recyclable paper substrates. The possibility of building these circuits using low‐temperature processes opens the door to new applications ranging from smart labels and sensors on clothing and packaging to electronic displays printed on paper pages for use in newspapers, magazines, books, signs, and advertising billboards. Because the CMOS circuits reported constitute fundamental building blocks for analog and digital electronics, this development creates the potential to have flexible form factor computers seamlessly layered onto paper. The holistic approach of merging low‐power circuitry with a recyclable substrate is an important step towards greener electronics. 相似文献
109.
Lamb loins were subjected to sous-vide cooking at different combinations of temperature (60, 70, and 80 °C) and time (6, 12, and 24 h). Different physicochemical, histological and structural parameters were studied. Increasing cooking temperatures led to higher weight losses and lower moisture contents, whereas the effect of cooking time on these variables was limited. Samples cooked at 60 °C showed the highest lightness and redness, while increasing cooking temperature and cooking time produced higher yellowness values. Most textural variables in a texture profile analysis showed a marked interaction between cooking temperature and time. Samples cooked for 24 h showed significantly lower values for most of the studied textural parameters for all the temperatures considered. Connective tissue granulation at 60 °C and gelation at 70 °C were observed in the SEM micrographs. The sous-vide cooking of lamb loins dramatically reduced microbial population even with the less intense heat treatment studied (60 °C–6 h). 相似文献
110.