全文获取类型
收费全文 | 732篇 |
免费 | 34篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 14篇 |
综合类 | 1篇 |
化学工业 | 177篇 |
金属工艺 | 14篇 |
机械仪表 | 17篇 |
建筑科学 | 21篇 |
矿业工程 | 2篇 |
能源动力 | 96篇 |
轻工业 | 51篇 |
水利工程 | 4篇 |
石油天然气 | 6篇 |
无线电 | 96篇 |
一般工业技术 | 124篇 |
冶金工业 | 46篇 |
原子能技术 | 7篇 |
自动化技术 | 92篇 |
出版年
2024年 | 1篇 |
2023年 | 25篇 |
2022年 | 45篇 |
2021年 | 64篇 |
2020年 | 34篇 |
2019年 | 51篇 |
2018年 | 35篇 |
2017年 | 20篇 |
2016年 | 34篇 |
2015年 | 25篇 |
2014年 | 35篇 |
2013年 | 61篇 |
2012年 | 49篇 |
2011年 | 40篇 |
2010年 | 33篇 |
2009年 | 26篇 |
2008年 | 20篇 |
2007年 | 19篇 |
2006年 | 12篇 |
2005年 | 15篇 |
2004年 | 17篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有768条查询结果,搜索用时 15 毫秒
721.
This study was designed to explore the effects or roles of usability factors (i.e., perceived ease of use, perceived usefulness, and satisfaction) and external support (i.e., teacher and peer support) on undergraduates’ use outcomes of Moodle in a blended learning environment. The research hypotheses derived from relevant constructs taken from the technology acceptance model, information systems continuance model, and the theory of reasoned action. The study’s dependent variable is use outcomes, which was conceptualized with factors such as academic performance, perceived learning assistance, and perceived impacts on learning. We conducted a cross-sectional survey and collected data from 126 undergraduate students attending a university in the Maritime region of Canada. The partial least squares technique was used to test the hypothesized relationships in the proposed research model. We found that usability factors have positive effects on students’ use outcomes; contrarily to predictions teacher and peer support did not. The findings of the study offer useful insights that can help HE administrators gain an understanding of antecedent factors likely to enhance students’ use outcomes of Moodle. 相似文献
722.
Murat Cenk Farhad Haghighi Zadeh M. Anwar Hasan 《Journal of Signal Processing Systems》2018,90(3):285-294
In this paper, we first present an enhancement of the well-known Karatsuba 2-way and 3-way algorithms for characteristic three fields, denoted by \(\mathbb {F}_{3^{n}}\) where n≥1. We then derive a 3-way polynomial multiplication algorithm with five 1/3 sized multiplications that use interpolation in \(\mathbb {F}_{9}\). Following the computation of the arithmetic and delay complexity of the proposed algorithm, we provide the results of our hardware implementation of polynomial multiplications over \(\mathbb {F}_{3}\) and \(\mathbb {F}_{9}\). The final proposal is a new 3-way polynomial multiplication algorithm over \(\mathbb {F}_{3}\) that uses three polynomial multiplications of 1/3 of the original size over \(\mathbb {F}_{3}\) and one polynomial multiplication of 1/3 of the original size over \(\mathbb {F}_{9}\). We show that this algorithm represents about 15% reduction of the complexity over previous algorithms for the polynomial multiplications whose sizes are of practical interest. 相似文献
723.
In this work, the fabrication conditions of anodic aluminum oxide (AAO) templates with different pore size diameters were achieved using oxalic, tartaric, and phosphoric acidic electrolytes. Silver (Ag) nanostructures (NSs) were embedded in AAO template by simple hydrothermal and photoreduction methods. Moreover, titanium dioxide (TiO2) NSs (nanowires) was deposited into these porous templates by sol-gel method. FESEM results suggested that Ag nanofishstars, nanonecklaces (NNs), and TiO2 nanowires (NWs) like structures were grown in AAO pores with high-order and -aspect ratios. An anti-adhesive method was used to estimate the nano-size effect of the structures for enhancing antibacterial mechanism against Pseudomonas aeruginosa Gram-negative bacterium, and Staphylococcus aureus Gram-positive bacterium. In this study, the inhibition percentages of the Ag NNs/AAO membrane were 86.4, and 77.4%, respectively whereas that of the Ag film on glass substrate were 65, and 53.9%. Moreover, the inhibition percentages of the TiO2 NWs/AAO membrane were 85.9, and 70.1%, on the other hand, the TiO2 film on glass substrate were 60.3, and 45.2%. Results proved that the high porosity of the AAO template improved the contact-killing and release-killing actions of nanoparticles against biofilms. 相似文献
724.
Mohammad Anwar Hosen Abbas KhosraviSaeid Nahavandi Douglas Creighton 《Chemical Engineering Research and Design》2014
In this paper, prediction interval (PI)-based modelling techniques are introduced and applied to capture the nonlinear dynamics of a polystyrene batch reactor system. Traditional NN models are developed using experimental datasets with and without disturbances. Simulation results indicate that traditional NNs cannot properly handle disturbances in reactor data and demonstrate a poor forecasting performance, with an average MAPE of 22% in the presence of disturbances. The lower upper bound estimation (LUBE) method is applied for the construction of PIs to quantify uncertainties associated with forecasts. The simulated annealing optimization technique is employed to adjust NN parameters for minimization of an innovative PI-based cost function. The simulation results reveal that the LUBE method generates quality PIs without requiring prohibitive computations. As both calibration and sharpness of PIs are practically and theoretically satisfactory, the constructed PIs can be used as part of the decision-making and control process of polymerization reactors. 相似文献
725.
Chemical composition and antioxidant activity of seeds of different cultivars of mungbean 总被引:1,自引:0,他引:1
ABSTRACT: Seeds of 4 cultivars (M-1, M-6, NM-92, and NM-98) of mungbean [ Vigna radiata (L.) Wilczek] were investigated for proximate composition, antioxidant potential, fatty acids, tocopherols, and minerals profiles. Hexane-extracted seed oil content of the investigated cultivars of mungbeans ranged from 1.20% to 1.56%. Mungbean seeds were found to be a rich source of protein (20.97% to 31.32%). The contents of Fe, Cu, Mg, Na, K, Ca, and Zn were found to be 105.8 to 190.9, 4.8 to 6.3, 48.6 to 51.7, 382.6 to 562.7, 11.6 to 18.8, 359.2 to 482.9, and 24.9 to 47.2 mg/kg, respectively. The mungbean seeds contained linoleic acid in the highest amount, 340.5 to 465.7 mg/100 g of dry seed, followed by palmitic, oleic, linolenic, stearic, and arachidic acids: 278.1 to 401.2, 212.6 to 293.5, 188.7 to 236.8, 135.5 to 168.4, and 22.8 to 24.5 mg/100 g of dry seed, respectively. The seeds were found to be a rich source of tocopherols (α, γ, δ) ranged from 1.1 to 10.1, 60.7 to 80.9, and 4.6 to 11.2 mg/kg, respectively. Methanolic extracts of the seeds of the mungbean cultivars exhibited a good antioxidant activity as determined in terms of measurement of total phenolic contents (TPC) (0.62 to 1.08 g/100 g of dry matter), percent inhibition of peroxidation (49.8% to 89.2%), reducing power (1.19% to 1.45%), and bleaching β-carotene. The results of the present analytical study revealed these 4 mungbean cultivars to be a potential source of essential fatty acids, antioxidants, minerals and protein, all of which are linked with positive health benefits. 相似文献
726.
The construction of PVC matrix-type β-blockers (sotalol, carvedilol, and betaxolol) ion selective electrodes and their use for direct potentiometry of their respective species are described. The proposed sensors are based on the complex ion associates of β-blockers with tungstophosphate (TP) and Ammonium Reineckate (Rein) ionophoris in poly vinyl chloride membrane (PVC) with Dioctylphthalate (DOP) plasticizer. The four electrodes (Beta-TP), (Sota-TP), (Carve-TP), and (Cave-Rein) show stable potential response with near Nernstian slope of 50.8, 33.7, 32.35, and 33 mv per decade, range of concentration 10-2-10-7 M β-blockers. Selectivity coefficients data obtained for 11 different organic and inorganic ions are presented. The electrodes have fast response time (30 and 40 s) and were used over wide range of pH 4.5-8.5. Validation of the method according to the quality assurance standers shows suitability of proposed sensors for use in the quality control assessment of these drugs. The results obtained for the determination of β-blockers with the proposed electrodes show average recoveries of 100.78% and a mean standard deviation of ±1.2. The nominal are obtained. The data agree well with those obtained by standard methods. 相似文献
727.
728.
Magnetohydrodynamic flow and heat transfer in an ionic viscous fluid in a porous medium induced by a stretching spinning disc and modulated by electroosmosis under an axial magnetic field and radial electrical field is presented in this study. The effects of convective wall boundary conditions, Joule heating and viscous dissipation are incorporated. The governing partial differential conservation equations are transformed into a system of self-similar coupled, nonlinear ordinary differential equations with associated boundary conditions. The Matlab bvp4c solver featuring a shooting technique and the fourth-order Runge–Kutta–Fehlberg method are used to numerically solve the governing dimensionless boundary value problem. Multivariate analysis is also performed to examine the thermal characteristics. An increase in rotation parameter induces a reduction in the radial velocity, whereas it elevates the tangential velocity. Greater electrical field parameter strongly damps the radial velocity whereas it slightly decreases the tangential velocity. Increasing magnetic parameter also damps both the radial and tangential velocities. An increment in electroosmotic parameter substantially decelerates the radial flow but has a weak effect on the tangential velocity field. Increasing permeability parameter (inversely proportional to permeability) markedly damps both radial and tangential velocities. The pressure gradient is initially enhanced near the disk surface but reduced further from the disk surface with increasing magnetic parameter and electrical field parameter, whereas the opposite effect is produced with increasing Joule dissipation. Increasing magnetic and rotational parameters generate a strong heating effect and boost temperature and thermal boundary layer thickness. Nusselt number is boosted with increasing Brinkman number (viscous heating effect) and Reynolds number. The simulations are relevant to electromagnetic coating flows, bioreactors and electrochemical sensing technologies in medicine. 相似文献
729.
Preparation and characterizations of polyaniline (PANI)/ZnO nanocomposites film using solution casting method 总被引:1,自引:0,他引:1
Faheem AhmedShalendra Kumar Nishat ArshiM.S. Anwar Lee Su-YeonGyung-Suk Kil Dae-Won ParkBon Heun Koo Chan Gyu Lee 《Thin solid films》2011,519(23):8375-8378
Polyaniline (PANI)-ZnO nanoparticles composites film has been successfully fabricated by solution casting technique on glass substrate in which ZnO nanopowder was prepared via auto combustion method and used as inorganic materials. The as-grown nanocomposites film has been characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Transmission electron microscopy (TEM) and Atomic Force Microscopy (AFM) for their structural and morphological characterizations. X-ray diffraction studies of as-grown film showed the reflection of ZnO nanoparticles along with a broad peak of PANI. The AFM study of the film shows the incorporation of ZnO nanoparticles into the polymer matrix which was further supported by roughness measurement. TEM images showed that the size of ZnO nanoparticles in the nanocomposites increase from ~ 35 nm to ~ 45 nm, indicating the interaction of nanoparticles with PANI molecular chains. FTIR spectra showed a band at 501 cm−1 due to ZnO nanoparticles while the hydrogen bonding between the amine group of PANI and ZnO nanoparticles had been confirmed from the presence of the absorption band at 1148 cm−1. 相似文献
730.
M.S. Anwar Shalendra Kumar Faheem Ahmed Nishat Arshi Gyung-Suk Kil Dae-Won Park Jiho Chang Bon Heun Koo 《Materials Letters》2011,65(19-20):3098-3101
Bundle of CeO2 nanowires have been successfully synthesized by a simple hydrothermal process using Ce(NO3)3·6H2O as cerium source and NaH2PO4·2H2O as mineralizer, into which no surfactant or template was introduced. The synthesized nanowires were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy and magnetization measurements. The XRD results indicated that CeO2 nanowires have fluorite structure. Magnetization measurements indicate that CeO2 nanowires exhibit room temperature ferromagnetism with remanent magnetization (Mr) and coercivity (HC) of about 7.44 × 10? 4 (emu/g) and 27.19 Oe, respectively, which may results due to the presence of defects in the CeO2 nanowires. 相似文献