全文获取类型
收费全文 | 934篇 |
免费 | 63篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 271篇 |
金属工艺 | 36篇 |
机械仪表 | 31篇 |
建筑科学 | 21篇 |
能源动力 | 64篇 |
轻工业 | 80篇 |
水利工程 | 9篇 |
石油天然气 | 7篇 |
无线电 | 120篇 |
一般工业技术 | 175篇 |
冶金工业 | 38篇 |
原子能技术 | 3篇 |
自动化技术 | 136篇 |
出版年
2024年 | 8篇 |
2023年 | 30篇 |
2022年 | 36篇 |
2021年 | 44篇 |
2020年 | 46篇 |
2019年 | 45篇 |
2018年 | 57篇 |
2017年 | 43篇 |
2016年 | 48篇 |
2015年 | 34篇 |
2014年 | 44篇 |
2013年 | 81篇 |
2012年 | 49篇 |
2011年 | 49篇 |
2010年 | 45篇 |
2009年 | 47篇 |
2008年 | 38篇 |
2007年 | 28篇 |
2006年 | 30篇 |
2005年 | 19篇 |
2004年 | 24篇 |
2003年 | 19篇 |
2002年 | 14篇 |
2001年 | 13篇 |
2000年 | 11篇 |
1999年 | 5篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1004条查询结果,搜索用时 609 毫秒
81.
The hot water process has recovered approximately 90% of the bitumen in oil sands, but the remaining 10% of bitumen and naphtha has been lost to the tailings pond. Recovery of bitumen and non-bituminous combustibles (NBC) from centrifuge, scroll and final tailings has been considered. The effects of four sequestering agents, and of chemical additives such as CaCl2 and FeCl3 on the flotation behavior of bitumen, NBC and minerals in these tailings have been investigated. A simple method of isolating NBC materials has been developed. The flotation of both bitumen and NBC was enhanced by phosphate treatment and depressed by EDTA. NBC was characterized by its physical properties, energy content, functionality and chemical analysis. A conceptual model explains the interactions between the bitumen, minerals and NBC fractions present in tailings slurries. 相似文献
82.
Shubham SINGHAL Ajay CHOURASIA Soraj Kumar PANIGRAHI Yogesh KAJALE 《Frontiers of Structural and Civil Engineering》2021,15(5):1128
This paper provides insight into the seismic behavior of a full-scale precast reinforced concrete wall under in-plane cyclic loading combined with out-of-plane loading replicated by sand backfill to simulate the actual condition of basement walls. The tested wall exhibited flexural cracks, owing to the high aspect ratio and considerable out-of-plane movement due to lateral pressure from the backfill. The wall performed satisfactorily by exhibiting competent seismic parameters and deformation characteristics governed by its ductile response in the nonlinear phase during the test with smaller residual drift. Numerical analysis was conducted to validate experimental findings, which complied with each other. The numerical model was used to conduct parametric studies to study the effect of backfill density and aspect ratio on seismic response of the proposed precast wall system. The in-plane capacity of walls reduced, while deformation characteristics were unaffected by the increase in backfill density. An increase in aspect ratio leads to a reduction in in-plane capacity and an increase in drift. Curves between the ratio of in-plane yield capacity and design shear load of walls are proposed for the backfill density, which may be adopted to determine the in-plane yield capacity of the basement walls based on their design shear. 相似文献
83.
84.
Jaya Sowjanya Siddireddy Ajay Kumar Vijay Jacqueline Tan Mark Willcox 《Contact lens & anterior eye》2018,41(2):144-153
Purpose
To investigate characteristics of the eyelid margins, meibomian glands and the tear film of contact lens wearers, and to determine whether these characteristics were related to symptoms of contact lens discomfort.Methods
A cross sectional study was performed on thirty existing daily wear soft contact lens wearers (6 male; 24 female) with median age of 23 years (range 18–41). Eyelid signs and tear film characteristics were evaluated during a single visit and subjects completed the contact lens and dry eye questionnaire (CLDEQ-8) to evaluate ocular discomfort.Results
Based on the CLDEQ-8 responses, subjects were classified as symptomatic (n?=?17) or asymptomatic (n?=?13). Grades of foam at meibomian gland orifices (3?±?1), expressibility (2?±?1) and quality of secretions (2?±?1), tear evaporation rate with (112?±?54?g/m2/h) or without (88?±?45?g/m2/h) contact lens wear, fluorescein tear breakup time (8?±?2 seconds) and tear lipid layer thickness (45?±?17?nm) were significantly associated with symptoms of discomfort in symptomatic lens wearers only (r2?>?0.45; p value?<?0.05). Upper lid-wiper epitheliopathy, meibomian gland acini reflectivity and tear meniscus height showed significant correlations with comfort scores in both symptomatic and asymptomatic contact lens wearers (p?<?0.05). A greater number of Demodex mites was also observed in the upper eyelid of symptomatic lens wearers (2?±?1) compared to asymptomatic lens wearers (0?±?0; p value?=?0.042).Conclusions
Morphological irregularities of the meibomian glands and alterations to tear film secretions that affect tear evaporative dynamics were associated with symptoms of discomfort amongst the symptomatic lens wearers. 相似文献85.
86.
Laminar flow and heal transfer in annular passages with axially nonuniform inner tubes are obtained numerically. A characteristic feature of these passages is that the flow separates in the streamwise direction. An axisymmetric coordinate system with an algebraic transformation in the radial direction kas been used. Fully elliptic vorticity-slream function and energy equations in the transformed coordinates are solved using an iterative alternate direction implicit (ADI) method. In an annulus with a smooth blockage, the flow separates immediately downstream of the blockage at Reynolds numbers greater than 100. The main features of the flow are established at a Reynolds number of 1000. The pressure drop is drastic near the maximum constriction. The heat flux is also high in the constricted region. A sharp increase in the heat transfer occurs where the fluid reattaches itself to the wall. The increase in the total pressure drop is about an order of magnitude greater than that in the average Nusselt number. 相似文献
87.
Pankaj Chowdhury Hassan Gomaa Ajay K. Ray 《International Journal of Hydrogen Energy》2011,36(21):13442-13451
A factorial design at two levels and four factors has been carried out in order to investigate the potential for hydrogen generation using Eosin Y-sensitized TiO2/Pt catalyst under visible solar light in presence of triethanolamine (TEOA) as electron donor. The solution pH was found to be a significant parameter, and was maintained at pH 7.0 throughout the investigation. Visible light irradiation time (I-time) showed highest positive effect on hydrogen generation followed by initial Eosin Y concentration (for dye-sensitization) and the TEOA concentration while Pt content (wt %) in TiO2 showed negative effect toward hydrogen generation. Experimental data were analyzed using both “Pareto analysis” as well as conventional regression analysis techniques. A regression function is proposed that satisfactorily predicts hydrogen generation. 相似文献
88.
Aqueous sodium and potassium carbonates have been photoreduced in the presence of Toluidine Blue solution (which is also the photocatalyst). The photocatalytic formation of formic acid and formaldehyde was measured spectrophotometrically using Nash reagent. The effect of variation of various parameters like pH, amount of photocatalyst (Toluidine Blue concentration), concentration of Na2CO3 and K2CO3, light intensity, etc., on the yield of photoproducts was also investigated. A tentative mechanism for this reduction has been proposed. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
89.
The coalescence-redispersion (CRD) model is examined in the fast chemistry limit for the single bimolecular reaction A+B M R and the series parallel reactions A+B M R;B+R M S occurring in a plug flow reactor with unmixed feed streams. For the single bimolecular reaction it is shown that in this limit the CRD model is asymptotically equivalent to the 3E fast closure as t M 0. For the series parallel reactions the CRD model predictions tend to be bracketed by the 3E slow and fast closure formulations. Representative results are presented for the variance decay of the individual reactants, and it is seen that even in the fast reaction limit where mixing is controlling, the shape of the feed stream PDFs has negligible influence on the progress of the reaction. 相似文献
90.
Jordan M. Anderson Jigna Patel Ajay S. Karakoti Nathan Greeneltch Diego J. Díaz Sudipta Seal 《Electrochimica acta》2011,56(5):2541
Nanocrystalline Pt/CeO2 composite electrodes were fabricated to study the electrochemical oxidation of methanol and ethanol. The performance of the electrodes was tested as the ceria solutions aged over time. It was observed that the performance oscillated with time, suggesting that the catalytic behavior towards alcohol oxidation was greatly dependent on the aging of the particles. These results point to a great dependence of the catalytic effect on the redox state of the ceria particles. 相似文献