全文获取类型
收费全文 | 536篇 |
免费 | 20篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 95篇 |
金属工艺 | 4篇 |
机械仪表 | 15篇 |
建筑科学 | 13篇 |
能源动力 | 8篇 |
轻工业 | 56篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 18篇 |
一般工业技术 | 46篇 |
冶金工业 | 248篇 |
原子能技术 | 4篇 |
自动化技术 | 42篇 |
出版年
2023年 | 4篇 |
2022年 | 15篇 |
2021年 | 16篇 |
2020年 | 13篇 |
2019年 | 7篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 7篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 25篇 |
2012年 | 17篇 |
2011年 | 28篇 |
2010年 | 18篇 |
2009年 | 9篇 |
2008年 | 15篇 |
2007年 | 11篇 |
2006年 | 16篇 |
2005年 | 9篇 |
2004年 | 14篇 |
2003年 | 8篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 11篇 |
1998年 | 76篇 |
1997年 | 47篇 |
1996年 | 20篇 |
1995年 | 21篇 |
1994年 | 15篇 |
1993年 | 11篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1977年 | 5篇 |
1976年 | 14篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有556条查询结果,搜索用时 15 毫秒
81.
Intra-abdominal cysts may rise from a variety of organs. However, foreign-body reaction and cyst formation should be considered in the differential diagnosis. In this report, we describe the finding of a preoperatively undetected gossypiboma. A gossypiboma is a mass within the body that is composed of a cotton matrix; in this case, an unmarked laparotomy sponge. The evaluation, findings, and prevention of gossypiboma are discussed. 相似文献
82.
The influence of retained austenite on the rotary bending fatigue endurance of carbonitrided specimens of two different steels is investigated. Results obtained in this work support the existence of a value of retained austenite for which the fatigue limit is maximum. A model for the influence of retained austenite, based on that generally accepted for superficial residual compressive stresses, is presented. According to this model, fatigue cracks could nucleate at different sites, surface or case bottom, in specimens with austenite contents at each side of the fatigue maximum, and this maximum should occur at lower values of retained austenite in notched specimens. 相似文献
83.
PJ Prado BJ Balcom SD Beyea RL Armstrong TW Bremner PE Grattan-Bellew 《Canadian Metallurgical Quarterly》1998,16(5-6):521-523
A total of 231 pigs were anesthetized and then scanned by DXA using a Lunar DPXL instrument. The weight of the pigs ranged from 5 to 97 kg (av. = 37.7 kg). Of the total, 98 pigs were scanned using the pediatric mode and 133 pigs were scanned using the adult mode. After scanning, the pigs were euthanized, the entire body homogenized by grinding, and analyzed chemically for fat, water, protein and total body mineral content. The mean value for the DXA total tissue mass (37.1 kg) was not significantly (P > 0.05, n = 231) different from the mean body weight. The mean DXA value for percent fat was 14.6 and was significantly less (P < 0.05) than the mean value (17.6%) measured by CHEM analysis. The greatest discrepancy occurred in pigs with < 15% body fat. From a prediction equation using the DXA R value [% fat = 493-349(DXA R value)], the DXA estimated percent fat was 18.0%, compared to 17.6% by CHEM analysis (P > 0.05). Using a prediction equation [g protein = -1.062 + 0.22(g DXA lean)], the DXA estimate for body protein content was 17.8%, compared to 17.1% (P < 0.05, n = 131) by CHEM analysis. The DXA estimate for body water content [g water = 508 + 0.74 (g DXA lean)] was 63.8%, compared to 62.6% (P < 0.05, n = 231) by CHEM analysis. The bone mineral content of 83 of the pigs measured by DXA was 2.40%, compared to 2.54% (P < 0.05, n = 83) estimated from CHEM analysis of total body ash [g bone mineral = g total body ash -0.0085(g DXA lean)]. 相似文献
84.
85.
Juliana Cristina Castro Giseli Cristina Pante Bruno Martins Centenaro Rafaela Takako Ribeiro De Almeida Eduardo Jorge Pilau Benedito Prado Dias Filho 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2020,37(9):1531-1541
ABSTRACT There is an increasing demand for fungi control in grains, especially toxigenic. Also, there is growing concern on the use of synthetic fungicides; thus alternatives are needed. The aim of this study was to evaluate the antifungal and antimycotoxigenic action of essential oils (EOs) from Zingiber officinale, Cinnamomum zeylanicum and Cymbopogon martinii against Fusarium verticillioides, a spoilage and toxigenic fungus. Essential oils were first chemically characterised by gas chromatography coupled to mass spectrometry, and their antioxidant potential was measured by the DPPH, ABTS and FRAP methods. Minimum inhibitory concentration (MIC) and disc diffusion were used to assess antifungal activity. Scanning electron microscopy was used to evaluate morphological changes in the fungus. Antimycotoxigenic activity of the EOs against the production of fumonisin B1 and B2 by F. verticillioides was evaluated using ultra-high-performance liquid chromatography system. Z. officinale, C. zeylanicum and C. martinii EOs were predominantly composed by zingiberene and geranial; eugenol; and geraniol, respectively. All the EOs had high antioxidant power, especially that from C. zeylanicum. The MICs were 250, 500 and 2,000 µg mL?1 for C. zeylanicum, C. martinii and Z. officinale EOs, respectively. Mycelial reduction of F. verticillioides was observed when EOs were used, and the lowest activity was detected in the Z. officinale EO. Overall, the tested EOs promoted structural damage to the fungal cell wall, decreased conidia size and mycelial reduction. Antimycotoxigenic evaluation of the EOs evidenced a significant reduction (p < .05) in the production of fumonisins B1 and B2 with all the EOs evaluated in the study. These results suggest that especially C. zeylanicum and C. martinii EOs are highly useful for controlling F. verticillioides and fumonisins production. 相似文献
86.
J. Del Prado X. Song D. Hu Xinhua Wu 《Journal of Materials Engineering and Performance》2005,14(6):728-734
Optical microscopy, analytical transmission microscopy and scanning electron microscopy, and hardness tests have been carried
out on quenched samples of Ti-15wt.%V-3wt.%Cr-3wt.%Al-3wt.%Sn containing different levels of oxygen and carbon that were aged
at temperatures between 400 and 600 °C. The increase of oxygen content and the addition of carbon (C) increase the kinetics
and the magnitude of age hardening. The addition of C greatly reduces the coarse grain boundary precipitation of α. Room temperature
deformation has been shown to override compositional differences, and all deformed alloys age harden similarly. The role of
oxygen and carbon additions and deformation on aging kinetics are discussed in terms of the factors, such as ω, dislocations,
and grain boundary oxygen content that influence α precipitation.
This paper was presented at the Beta Titanium Alloys of the 00’s Symposium sponsored by the Titanium Committee of TMS, held
during the 2005 TMS Annual Meeting & Exhibition, February 13–16, 2005 in San Francisco, CA. 相似文献
87.
Benedicto HG Bombonato PP Macchiarelli G Stifano G Prado IM 《Microscopy research and technique》2011,74(11):1018-1023
The heart is composed by a specialized muscle, whose form and function are essentials for an adequate work and shows an amount of connective tissue which support and provide insertion for this muscle, whose collagen fibers are responsible for determination of tissue feature. Our objective was to identify the structural arrangement of the heart collagen fibers in dogs. The hearts of the dogs were submitted to the process of the controlled digestion with NaOH solution and observed by scanning electron microscope. Our results showed that the collagen fibers of the endomysial wall have structural arrangement composed by an irregular network with one layer in normal dogs but in diabetic dogs the network acquires a greater amount of the fibers and layers, looking like a "rug" of fibers modifying the relationships of the stress/strain of the tissue. Ahead of the observed results we are able to conclude that exist increase in the amount and thickness of cardiac collagen fibers, beyond the increase of layers and architectural disarrangement in the endomysial wall in the diabetic dogs. 相似文献
88.
Increased emissions of nitric oxide and nitrous oxide following tillage of a perennial pasture 总被引:3,自引:0,他引:3
M. Pinto P. Merino A. del Prado J.M. Estavillo S. Yamulki G. Gebauer S. Piertzak J. Lauf O. Oenema 《Nutrient Cycling in Agroecosystems》2004,70(1):13-22
About 40% of the agricultural land in the European Union (EU) is grassland used for animal production. When grassland is tilled, organically bound carbon and nitrogen are released, providing substrates for nitrifying and denitrifying microorganisms. The aim of this study was to examine the immediate effects of tillage of a perennial grassland carried out on different dates, on the emissions of nitric oxide (NO) and nitrous oxide (N2O), monitored intensively over a 5-day period, in a humid, dairy farming area of northern Spain. Soil was tilled 12 days and 2 days prior to fertiliser application. Tillage, time of tillage, and N fertiliser application affected NO and N2O emissions. Tillage 12 days before the start of the flux measurements resulted in higher emissions than tillage one day before, the difference being related to differences in soil mineral N and water-filled pore space (WFPS). Emissions of NO peaked at a WFPS of 50–60%, while N2O fluxes peaked at 70–90% WFPS. Loss of N was greater as N2O than as NO. The total loss of N as N2O plus NO ranged from 0.027 kg N ha–1 in unfertilised plots to 0.56 kg N ha–1 in the tilled and N fertilised plot. Thereafter emissions decreased rapidly to low values. The results of this study indicate that tillage of perennial grassland may release large amounts of NO and N2O, the amounts also depending on moisture conditions and addition of N fertiliser. We suggest that in order to reduce such emissions, application of N fertiliser should not immediately follow tillage of perennial grassland, as there is an extra supply of N from mineralisation of organic matter at this time. 相似文献
89.
Adsorption of adenine on Au(1 1 1) and Au(1 0 0) electrodes is studied by cyclic voltammetry, impedance and chronoamperometric measurements in 0.1 M and 0.01 M KClO4 and in 0.5 M NaF solutions. The experiments performed with flame-annealed electrodes at different contact potentials, scan potential limits and scan rates, suggest different adsorption behaviour on the unreconstructed and reconstructed surface domains. This is confirmed by comparing the results obtained with electrochemically annealed unreconstructed and with flame-annealed reconstructed surfaces. In both cases the initial electrode surface state is characterised by the Epzc values. The adsorption on reconstructed surfaces takes place at more positive potentials than on the unreconstructed surfaces and induces the lifting of the reconstruction.The thermodynamic analysis is performed on the chronoamperometric data for adenine desorption on well characterised unreconstructed Au(1 1 1) surfaces. To this end a new methodology of the chronoamperometric experiments is introduced. Quantitative thermodynamic adsorption parameters such as surface tension, Gibbs surface excess, Gibbs energy of adsorption, potential versus Gibbs excess slope and electrosorption valency are determined. Weak chemisorption of adenine is inferred with a molecular orientation independent on the coverage and on the electrode potential. It is proposed that adsorbed adenine molecules adopt a tilted orientation at the surface to facilitate the coordination to the gold atoms. 相似文献
90.
The aim of this study was to evaluate the effects of the 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), and MTAD solutions on the surface of gutta‐percha and Resilon cones by using atomic force microscopy (AFM). Accessory cones were washed and dried. The cones were randomly divided into six groups: gutta‐percha immersed in NaOCl, CHX, and MTAD, and Resilon immersed in NaOCl, CHX, and MTAD. AFM images of the same area were made in different periods of time. JPK? Image Processing Software was used to evaluate the images. The parameters used to evaluate the changes were RMS and line profiles. No statistically significant change was observed in the RMS values. The line profiles detected changes only for gutta‐percha surfaces after immersion in NaOCl and MTAD solutions. In conclusion, 5.25% NaOCl and MTAD are associated with local changes in surface roughness of gutta‐percha cones. No change was observed when 2% CHX was used. The use of all tested solutions did not produce any changes on Resilon surface. Microsc. Res. Tech. 75:791–795, 2012. © 2012 Wiley Periodicals, Inc. 相似文献