全文获取类型
收费全文 | 541篇 |
免费 | 40篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 11篇 |
综合类 | 2篇 |
化学工业 | 146篇 |
金属工艺 | 11篇 |
机械仪表 | 24篇 |
建筑科学 | 21篇 |
矿业工程 | 2篇 |
能源动力 | 34篇 |
轻工业 | 47篇 |
水利工程 | 18篇 |
石油天然气 | 27篇 |
无线电 | 48篇 |
一般工业技术 | 70篇 |
冶金工业 | 9篇 |
自动化技术 | 118篇 |
出版年
2024年 | 3篇 |
2023年 | 8篇 |
2022年 | 19篇 |
2021年 | 44篇 |
2020年 | 27篇 |
2019年 | 41篇 |
2018年 | 60篇 |
2017年 | 28篇 |
2016年 | 53篇 |
2015年 | 25篇 |
2014年 | 30篇 |
2013年 | 55篇 |
2012年 | 40篇 |
2011年 | 36篇 |
2010年 | 24篇 |
2009年 | 22篇 |
2008年 | 16篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 3篇 |
2000年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1986年 | 1篇 |
排序方式: 共有588条查询结果,搜索用时 15 毫秒
171.
Saeid Ebrahimi Hossein A. Dabbagh 《International Journal of Food Science & Technology》2019,54(9):2770-2779
L-Ascorbic acid (AA) is an essential component for organisms and is responsible for various functions in the human body. Its structure is in a way that suffering significant structural changes during storage. Herein, the stability of L-ascorbic acid aqueous solution at various thermal (25 and 90 °C ± 2) and atmospheric oxygen or argon was monitored by optical rotation changes as a function of time intervals. Under oxygen, specific optical rotation [α] of the solution was decreased from + 22.0 to + 2.0 after 32 days and under argon + 11.5 after 9 months at 25 °C. The loss of [α] increased at 90 °C under both oxygen and argon atmospheres. Subsequently, the obtained reaction mixtures were evaporated to dryness and analysed by FT-IR, 1H-NMR and GC-MS techniques. Results of these analyses indicate that AA was decomposed to a complex mixture of reaction products. 相似文献
172.
173.
174.
This paper presents a novel methodology to obtain the entire power consumption versus delay tradeoff curve for the critical paths of a combinational logic circuit in a very efficient way using the genetic algorithm (GA). In order to evaluate the proposed algorithm the most representative set of two-level and multi-level networks from the MCNC91 benchmark suite were processed. The required computational effort, measured in terms of CPU time, is several times better for the proposed GA optimization technique than liner programming (LP) technique. On the other hand, the optimal design points obtained by the GA and LP techniques are very close to each other to within 0.3%. 相似文献
175.
This study investigated experimentally the CHF phenomena of aqueous-based alumina nanofluids in single microchannels, and assessed the validity of a number of microchannel based CHF correlations using experimental nanofluids data. While usual approaches for CHF enhancement are through the modification of different tube surfaces or employing different inserts, this work showed that CHF in microchannels could be enhanced significantly by the inclusion of small concentrations of nanoparticles. The CHF value was found to increase with increase of mass flux, initial subcooling and alumina nanoparticle concentrations. The maximum subcooled CHF enhancement occurred at the lowest mass flux and highest alumina concentration within the experimental range. In addition, the Lee and Mudawar correlation was modified to predict the critical heat flux of water and nanofluids. The new model was examined by experimental data and 24% and 30% mean absolute error were observed for water and alumina nanofluid respectively. 相似文献
176.
Seyyed Abbas Mousavi Morteza Gholizadeh Saeid Sedghi Mahdi Pourafshari-Chenar Molood Barmala Ahmad Soltani 《Chemical Engineering Research and Design》2010
In this study, the effect of film preparation conditions on the gas permeation properties of polyethylene (PE) and ethylene vinyl acetate (EVA) films (containing 18 and 28 wt% vinyl acetate) was investigated. Film blowing and phase inversion methods were applied in the production of PE and EVA films, respectively. The permeation of pure oxygen and carbon dioxide gases was measured at room temperature. The results indicated that with the increase of PE film thickness, permeability and solubility of O2 and CO2 in these films decreased; but the diffusivities of gases through PE films increased. In addition, in the case of EVA copolymers, by increasing the content of vinyl acetate, the permeability of CO2 increased. The rate of increase in CO2 permeability was different for samples having different preparation conditions. For example, the samples prepared using chloroform as the solvent instead of THF, showed lower CO2 permeability. Also, the morphological studying of film structure indicated that the higher CO2 permeability for the samples made from THF solvent is due to the existing of higher porosity in the under layer polymer area. Also scanning electron microscopy (SEM) micrographs showed that with the usage of phase inversion method, there will be a thin dense layer near to the glass substrate. 相似文献
177.
Saeid Baroutian Abdul Aziz Abdul Raman Nik Meriam Nik Sulaiman 《Fuel Processing Technology》2010,91(11):1378-8929
In this study, potassium hydroxide catalyst supported on palm shell activated carbon was developed for transesterification of palm oil. The Central Composite Design (CCD) of the Response Surface Methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst loading and methanol to oil molar ratio on the production of biodiesel using activated carbon supported catalyst. The highest yield was obtained at 64.1 °C reaction temperature, 30.3 wt.% catalyst loading and 24:1 methanol to oil molar ratio. The physical and chemical properties of the produced biodiesel met the standard specifications. This study proves that activated carbon supported potassium hydroxide is an effective catalyst for transesterification of palm oil. 相似文献
178.
Saeid Sabouri‐Ghomi Mehdi H. K. Kharrazi Salah‐E‐Deen Mam‐Azizi Ramin Asad Sajadi 《The Structural Design of Tall and Special Buildings》2008,17(4):823-837
To improve buckling stability and to prevent early elastic buckling of infill plates, vertical and horizontal plate stiffeners are designed for steel plate shear wall (SPSW) systems. Furthermore, effective design of stiffeners for SPSW systems results in improved structural behavior, such as increase of stiffness, capacity and energy absorption. In this paper, the effect of stiffeners is studied on SPSW structural behavior and consequently a rational method is proposed to determine the minimum required moment of inertia for stiffeners resulting in local buckling mode of the infill plate. The proposed requirement is then compared to results obtained from tests previously conducted, as well as those gained from finite element (FE) analyses performed for this study. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
179.
Afshin Tatar Saeid Nasery Meysam Bahadori Mohammad Bahadori Ali Barati-Harooni 《Petroleum Science and Technology》2016,34(10):951-960
Natural gas commonly contains water as a contaminant that can condense to water or form gas hydrates, which causes a range of problems during gas production, transportation, and processing. Therefore, the removal of gas moisture is of great importance. A common and popular method for removing water contamination from natural gas is using solid dehydrators. Calcium chloride is a nonregenerative desiccant to dehydrate natural gas. With continual water adsorption, CaCl2 changes to consecutively higher states of hydration, finally producing a CaCl2 brine solution. This method does not require heating or moving parts. In addition, it does not react with H2S or CO2. These features make this method a popular one for drying natural gas. Nevertheless, precise and simple methods are needed to predict the water content of natural gas dried by calcium chloride dehydrator units. In this study, an intelligent method, called the radial basis function neural network, was incorporated to predict the gas moisture dehydrated by calcium chloride in dehydration units. Modeling was performed under different conditions of a fresh recharge and before recharging. The overall correlation factor of 0.9999 for both the fresh charge and before charging conditions showed that the outputs of the proposed models were in agreement with the experimental data. In addition, the developed models were compared with the previously proposed intelligent models and classic correlations. The comparison showed that the developed model is superior to the previously proposed models and correlations regarding the accuracy of prediction. 相似文献
180.