全文获取类型
收费全文 | 509篇 |
免费 | 26篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 8篇 |
综合类 | 1篇 |
化学工业 | 158篇 |
金属工艺 | 15篇 |
机械仪表 | 16篇 |
建筑科学 | 26篇 |
矿业工程 | 2篇 |
能源动力 | 36篇 |
轻工业 | 23篇 |
水利工程 | 18篇 |
石油天然气 | 9篇 |
无线电 | 30篇 |
一般工业技术 | 67篇 |
冶金工业 | 12篇 |
原子能技术 | 7篇 |
自动化技术 | 111篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 17篇 |
2021年 | 30篇 |
2020年 | 33篇 |
2019年 | 27篇 |
2018年 | 34篇 |
2017年 | 32篇 |
2016年 | 34篇 |
2015年 | 26篇 |
2014年 | 33篇 |
2013年 | 43篇 |
2012年 | 30篇 |
2011年 | 39篇 |
2010年 | 23篇 |
2009年 | 25篇 |
2008年 | 20篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有539条查询结果,搜索用时 15 毫秒
531.
Farhad Hassanzadeh Mikael Collan Mohammad Modarres 《The International Journal of Advanced Manufacturing Technology》2012,58(1-4):227-236
The aim of this paper is to develop a practical R&D portfolio selection model that addresses effective R&D project valuation issue, while it tackles R&D uncertainty in portfolio optimization. Fuzzy sets theory is employed to capture and model the inaccuracy in project information. To avoid the well-known complications of fuzzy real option valuation, the fuzzy pay-off method is used to more effectively value R&D projects. The resulting problem is formulated as a fuzzy zero–one integer programming model which is later transformed into a crisp mathematical formulation to solve the problem for various degrees of risk. A numerical example is used to illustrate the proposed approach. 相似文献
532.
Abstract: In the present study, fatty acids and essential oils of the flower of borage (Borago officinalis L.) were obtained by supercritical carbon dioxide fluid extraction under different conditions. The extracts obtained were compared to oils of borage flower oil isolated by hydrodistillation. The obtained oils were analyzed by gas chromatography mass spectrometry. The compounds were identified according to their retention indices and mass spectra. The experimental parameters of supercritical fluid extraction (SFE) were optimized using a central composite design after a full factorial experimental design. Extraction yields based on SFE varied in the range of 0.02% to 1.96% (w/w), and the oil yield based on the hydrodistillation was 0.05% (v/w). The optimum conditions of SFE were obtained at a pressure of 350 atm, a temperature of 65 °C, a methanol modifier volume of 100 μL, and static and dynamic extraction time of 10 min. Main components of the extracts under optimum SFE conditions were palmitic acid, linoleic acid, γ‐linolenic acid, and oleic acid. The results indicated that by using the suitable extraction conditions, SFE is more effective than the conventional hydrodistillation method in the extraction of fatty acids and the preservation of its quality. Practical Application: SFE is a good technique for the extraction of oils from plants. The extraction yields by SFE are more than the conventional method. SFE is used on a large scale for production of essential oils and pharmaceutical products from plants. 相似文献
533.
Jinhe Li Shiv O. Prasher Roberto S. Clemente William D. Reynolds Ward N. Smith Donald S. Gamble Edward Topp Cooper H. Langford Farhad Salehi 《Canadian Metallurgical Quarterly》1999,125(4):212-222
The sorption behavior of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), a commonly used herbicide for corn, on intact soil columns was studied by incorporating a new two-stage sorption mechanism into PESTFADE, a pesticide fate and transport model. This mechanism takes into account intraparticle diffusion of pesticide into the soil matrix (also sometimes known as bound residues), the sorption capacity of soil, and a variable pesticide distribution coefficient Kd. The modified model's performance was verified by comparing simulated values with those obtained from an intact column study in the laboratory. The two-stage mechanism was also compared and contrasted with the conventional adsorption approach based on a constant Kd. Simulations with the two-stage mechanism indicated a closer agreement with measured values (deviations in the range of 5–65%) than that of the conventional adsorption approach (deviations in the range of 10–700%). Furthermore, it was found that simulated values were particularly sensitive to soil tortuosity τ, soil bulk density ρ, soil moisture content θw, labile sorption capacity θc, and intraparticle diffusion parameters. 相似文献
534.
Farhad Ahadi Koloo Armin Badakhshan Hossein Fallahnejad Mehdi Ebadi Jamkhaneh Masoud Ahmadi 《钢结构国际杂志》2018,18(1):163-177
Concrete-filled steel tube (CFT) columns are used in the primary lateral resistance systems. The objective of this research is to analyse the behavior of the steel beam to CFT column connections. A three-dimensional numerical model for simulating the behavior of CFT connections was developed with the aid of the general purpose nonlinear finite element analysis package ABAQUS. In this paper, 90 CFT connection specimens include simple and moment connections that were tested under reversed cyclic loading. Shear capacity of joint, moment-drift response, energy absorption, and displacement ductility were studied in those models. The results have indicated that, the hysteresis curve of CFT columns was plump; no pinch phenomenon can be found; the damage and degradation degree of the strength and stiffness of specimens is lower; and high energy dissipation capacity can be achieved. Improvement in the behavior of CFT connection depends on the beam characteristics and column features. 相似文献
535.
Silicon - In this article the preparation of Fe3O4@MCM-41@NH-SO3H, a new sulfonated magnetic mesoporous nanocomposite, is reported. The introduced catalyst is structurally based on MCM-41 as the... 相似文献
536.
Vaferi Kourosh Vajdi Mohammad Nekahi Sanam Nekahi Sahar Sadegh Moghanlou Farhad Azizi Shahla Shahedi Asl Mehdi 《Microsystem Technologies》2023,29(1):141-156
Microsystem Technologies - The problem of generating a high amount of heat in microelectronic equipment should be minimized properly. Allowing systems to run for long periods of time in high... 相似文献
537.
Tabrizi Arvin Taghizadeh Aghajani Hossein Laleh Farhad Farhang 《Protection of Metals and Physical Chemistry of Surfaces》2022,58(2):365-373
Protection of Metals and Physical Chemistry of Surfaces - In this study, a thin chromium layer was applied on pure titanium substrate in a Sargent bath including 250 g/L chromic acid and 2.5 g/L... 相似文献
538.
Studying the Role of Gelation Agents in Gelcasting Non-porous Si3N4 Bodies by Pressureless Sintering
Sharifi Omid Alizadeh Siavash M. Golmohammad Mohammad Golestanifard Farhad 《SILICON》2022,14(16):10447-10457
Silicon - The monomer content in the gelcasting process affects the kinetics of cross-linking reactions which determines the quality of the gel network structure and the final properties of the... 相似文献
539.
Aliakbar Ahmadi Mojgan Ayoubi-Chianeh Mohamad Z. Kassaee Farhad Bayat 《加拿大化工杂志》2023,101(7):4200-4216
The aim of this research is a comparison of the efficiency of six commercially available cyclodextrins (CDs) to improve the solubility and oral bioavailability of atorvastatin calcium (ATV-Ca) and rosuvastatin calcium (ROV-Ca) drugs in aqueous media. Inclusion complexes of both drugs with non-toxic α-CD, β-CD, γ-CD, HP-β-CD, M-β-CD, and maltodextrin were prepared in a 1:1 stoichiometry via the kneading method. To reach the best CD, various experimental and computational analyses were performed including phase solubility, dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), atomic force microscopy (AFM), hydrogen-1 nuclear magnetic resonance (1HNMR), carbon-13 nuclear magnetic resonance (13CNMR), and molecular docking calculations. The M-β-CD turned out to be the best substrate for the micro-encapsulation of both drugs. Also, ATV showed a higher tendency than ROV to form inclusion complexes with CDs. Molecular docking studies showed that HP–β–CD and M-β-CD are the most suitable substrates for the formation of inclusion complexes, respectively. Our research showed that the β-CD is not necessarily the most efficient substrate for increasing solubility based on previous reports in the literature; meanwhile, the other employed substrates in this study can show acceptable performances in this regard. According to our results, M-β-CD is the best substrate for the micro-encapsulation of both drugs, which increases their solubility in water. 相似文献