全文获取类型
收费全文 | 677篇 |
免费 | 13篇 |
国内免费 | 29篇 |
专业分类
电工技术 | 5篇 |
综合类 | 23篇 |
化学工业 | 176篇 |
金属工艺 | 16篇 |
机械仪表 | 47篇 |
建筑科学 | 62篇 |
矿业工程 | 7篇 |
能源动力 | 25篇 |
轻工业 | 113篇 |
水利工程 | 5篇 |
石油天然气 | 21篇 |
武器工业 | 2篇 |
无线电 | 69篇 |
一般工业技术 | 86篇 |
冶金工业 | 32篇 |
原子能技术 | 16篇 |
自动化技术 | 14篇 |
出版年
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 9篇 |
2017年 | 17篇 |
2016年 | 16篇 |
2015年 | 26篇 |
2014年 | 29篇 |
2013年 | 47篇 |
2012年 | 48篇 |
2011年 | 71篇 |
2010年 | 44篇 |
2009年 | 39篇 |
2008年 | 34篇 |
2007年 | 39篇 |
2006年 | 36篇 |
2005年 | 38篇 |
2004年 | 18篇 |
2003年 | 24篇 |
2002年 | 22篇 |
2001年 | 19篇 |
2000年 | 12篇 |
1999年 | 12篇 |
1998年 | 13篇 |
1997年 | 10篇 |
1996年 | 11篇 |
1995年 | 12篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有719条查询结果,搜索用时 31 毫秒
11.
《Food Control》2015
This study evaluated the individual and combined efficacies of physical processing techniques such as heating, Dynashock multi-frequency ultrasound waves, ultraviolet-C (UV-C), and additives such as sodium benzoate, potassium sorbate, α- and β-Pinene for pasteurization of orange and apple juices against acid-adapted Escherichia coli O157:H7. In heated apple juice, log-linear inactivation of the test organism resulted in D values which were used to calculate for the recommended 5-log reduction process schedules (t5D) at 45, 50, 52, 55, and 60 °C equal to 481.5, 103.6, 45.0, 22.4, and 10.54 min, respectively. E. coli O157:H7 exhibited biphasic inactivation composed of a slow inactivation lag, followed by log-linear inactivation in ultrasound-treated juice. t5D schedules were similarly calculated at 54.7 and 77.5 min for orange and apple juice, respectively. Lethal rate analyses in the ultrasound-treated apple juice revealed that 85% of the reduction in E. coli population was due to the heat liberated by cavitation. Combined ultrasound and UV-C treatment resulted in greater inactivation rates in both juices, with greater efficacy in apple juice. Supplementation of all tested additives, whether singly or in combination, similarly resulted in significantly shorter t5D schedules in both juices. 相似文献
12.
The electronic structure of a semiconducting mixed-stack charge transfer (CT) complex composed of a 2,7-dialkyl[1]benzothieno[3,2-b][1] benzothiophene (diC8-BTBT) electron donor and a tetracyanoquinodimethane (TCNQ) electron acceptor, (diC8-BTBT)(TCNQ), was studied by ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy. Compared with its components, the frontier electronic states observed for the (diC8-BTBT)(TCNQ) complex showed a large stabilization that originates from the reconstruction of electronic states by intermolecular donor-acceptor CT interactions. We discuss how the frontier electronic states of the complex are formed from those of the individual component molecules, and clarify the origin of the air-stable n-type organic field-effect transistor characteristics that the material exhibits when it is used as a channel semiconductor. 相似文献
13.
An equation relating the measured irradiance and the output power of a fluorescent lamp was derived by Keitz. The equation forms the basis for a new protocol that has been proposed for quantifying the total flux from an ultraviolet lamp. There has been confusion in the literature regarding the spatial distribution of flux from lamp emitters, which has led to emission models that are similar to the Keitz model but are incorrect. The Keitz equation is derived here from first principles in an effort to eliminate the confusion and present a correct method of calculating total flux. 相似文献
14.
研究了猕猴桃果汁膜厚度、辐射距离、时间和温度4个因素对紫外线杀灭接种在猕猴桃清汁中的大肠杆菌的影响。并通过正交试验得出各因素的最佳组合。结果表明:处理时间和果汁厚度对紫外线的杀菌效果影响最为显著。当果汁厚度为0.5mm,辐射时间为5min,辐射距离为100mm,杀菌温度为30℃时,杀菌率可达99.97%。 相似文献
15.
《Food Control》2014
The purpose of this study was to investigate the effectiveness of ultraviolet-C (UV-C) light inactivation as affected by the location of pathogens on the surface and at stem scars of whole grape tomatoes. A mixed bacterial cocktail containing a three strain mixture of Escherichia coli O157:H7 (C9490, E02128 and F00475) and a three serotype mixture of Salmonella enterica (S. Montevideo G4639, S. Newport H1275, and S. Stanley H0558) were used. Tomatoes were spot inoculated using approximately 100 μL of inocula to achieve a population of about 107±1 CFU/tomato. Additionally, the effects of treatment on color, texture, lycopene content, and background microbial loads during post UV-C storage at 4 °C for 21 days were determined. Results showed that UV-C doses of 0.60–6.0 kJ/m2 resulted in 2.3–3.5 log CFU per fruit reduction of E. coli O157:H7 compared to 2.15–3.1 log CFU per fruit reduction for Salmonella on the surfaces. Under the same conditions, log reductions achieved at stem scar were 1.7–3.2 logs CFU for E. coli O157:H7 and 1.9–2.8 logs CFU for Salmonella. The treatment was effective in controlling native microbial loads during storage at 4 °C as the total aerobic mesophilic organisms (PCA) and anaerobic lactic acid bacteria (LAB) counts of treated tomatoes were significantly (p < 0.05) lower during storage compared to the control group and the yeast and mold populations were reduced significantly below the detection limit. Furthermore, the firmness of tomato and its color was not affected by the UV-C doses during storage. UV-C radiation could potentially be used for sanitizing fresh tomatoes and extending shelf-life. The results of this study indicate that the specific location of pathogens on the produce influences the effectiveness of UV-C treatment, which should be taken into consideration for the design of UV-C systems for produce sanitization. 相似文献
16.
Upper room (UR)-ultraviolet germicidal (UVGI) systems, one of several disinfection applications of UV, target airborne infectious diseases in rooms of buildings such as healthcare facilities. Previous studies have introduced many experiments showing the germicidal effect of UR-UVGI systems. In this study, a novel numerical method of estimating the germicidal effect of UR-UVGI systems for air exhaled by ward patients was introduced. The method adopts and modifies the concept of ventilation efficiency because the germicidal effect depends upon how the air containing airborne infectious particles flows and stays within UV-radiated area. A case study based on a four-patient ward showed that UV doses were correlated with the age of the air exhaled by a source patient, as expected. Moreover, the UV doses were considerably affected by the position of the UR-UVGI system. Inactivation rates of the influenza virus estimated using the UV doses, were in the range of 48–74%, and those of Mycobacterium tuberculosis were 68–90% in the breathing area of a neighboring patient. The results indicate not directly the decreased concentration of airborne infectious particles, but the possibility of inactivation caused by the UR-UVGI system, which is useful for system optimization. 相似文献
17.
O. StenzelD. Gäbler S. Wilbrandt N. KaiserH. Steffen A. Ohl 《Optical Materials》2011,33(11):1681-1687
We present extended experimental material about optical and mechanical properties as well as the water content of aluminium oxide films, deposited by plasma ion assisted electron beam evaporation. A clear correlation between these experimental data is established and understood as being affected by the different degree of the porosity of the films. When adding fluorine as a reactive gas during deposition, aluminium oxifluoride layers can be obtained that appear nearly free of water, and combine UV-transparency with higher UV refractive indices than porous aluminium oxide layers. 相似文献
18.
A series of ozone/UV treatment under injection of ozone with different ozone-gas bubble sizes was performed at pH 1.7 and 7.4. The increase in the bubble size and the decrease in pH enhanced the ozone utilization efficiency. The enhancement of ozone utilization efficiency was caused by the shift of the production pathway of hydroxyl radical (OH) from the OH production via O3 – to the UV photolysis of H2O2. The lower pH caused this shift through the chemical equilibrium of H2O2 and HO2 –, and the large bubbles caused this shift through the augmentation of H2O2 transport from the bubble surface to the bulk solution. 相似文献
19.
Ultraviolet and violet upconversion luminescence in Ho-doped Y2O3 ceramic induced by 532-nm CW laser
Feng QinYangdong Zheng Ying YuZhemin Cheng Pouran Sadat TayebiWenwu Cao Zhiguo Zhang 《Journal of Alloys and Compounds》2011,509(4):1115-1118
Ultraviolet and violet upconversion luminescence spectra of holmium-doped Y2O3 were produced under the excitation of a compact continues-wave 532 nm solid-state laser. Emissions around 306, 362, 412, 390 and 428 nm can be assigned to the transitions of 3D3 → 5IJ (J = 8, 7, 6), 5G4 → 5I8 and 5G5 → 5I8, respectively. Power dependence and upconversion dynamics analysis demonstrated that both the energy transfer upconversion (ETU) and the excited state absorption (ESA) processes were involved in the population of 3D3 state via the coupled intermediate states 5S2/5F4. Fluorescence spectra in the visible and infrared ranges showed that 5G4 and 5G5 states were populated by the ESA process from 5I6 and 5I7 states, respectively, while the 5I6 and 5I7 states were radiatively populated from the excited 5S2/5F4 states. Upconversion mechanisms have been evaluated based on a rate equation model. 相似文献
20.
《Organic Electronics》2014,15(9):1942-1950
Electron transporting layers (ETLs) in inverted polymer solar cells (I-PSCs) were fabricated by spin coating a colloidal dispersion of ZnO nanoparticles (NPs), and the effects of ultraviolet–ozone (UVO) treatment on the ZnO NP ETLs were investigated. The brief UVO treatment (<5 min) could considerably improve the performance of the resulting I-PSCs (∼30% increase in power conversion efficiency); whereas, excessive UVO treatment (>10 min) caused significant degradation. The characterization of the ZnO ETLs as a function of the UVO treatment duration revealed that brief treatment can remove the residual organic stabilizer molecules on the surface of the ZnO films by UV induced decomposition mechanism. However, excessive treatment can generate additional defects on/within the ZnO films, which can induce charge recombination. This effect was further confirmed by the thermal treatment of the ZnO ETLs at a high temperature (280 °C) at which the organic surfactants could be removed. Flexible I-PSCs were also fabricated using indium doped tin oxide coated plastic substrates and the usefulness of the room temperature UVO treatment was further confirmed in view of its potential applicability in flexible devices. 相似文献