全文获取类型
收费全文 | 250篇 |
免费 | 10篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 6篇 |
化学工业 | 85篇 |
金属工艺 | 5篇 |
机械仪表 | 3篇 |
建筑科学 | 3篇 |
能源动力 | 18篇 |
轻工业 | 26篇 |
水利工程 | 2篇 |
无线电 | 15篇 |
一般工业技术 | 52篇 |
冶金工业 | 14篇 |
自动化技术 | 34篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 15篇 |
2020年 | 9篇 |
2019年 | 14篇 |
2018年 | 14篇 |
2017年 | 15篇 |
2016年 | 13篇 |
2015年 | 13篇 |
2014年 | 19篇 |
2013年 | 23篇 |
2012年 | 13篇 |
2011年 | 21篇 |
2010年 | 9篇 |
2009年 | 14篇 |
2008年 | 7篇 |
2007年 | 10篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2001年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有263条查询结果,搜索用时 15 毫秒
21.
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22.
Preeti Gangadharan Jaya N. Sahu Bhim C. Meikap 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(10):1282-1288
BACKGROUND: Ammonia is applied to increase the efficiency of an electrostatic precipitator for fly ash removal from a flue gas stream from a boiler using fossil fuel. In the present work, the hydrolysis of urea to generate ammonia for flue gas conditioning, with the help of aluminium oxide catalyst, has been studied. RESULTS: The effect of temperature, catalyst and initial concentration on the conversion was studied. Conversion was found to increase exponentially with temperature. Addition of catalyst resulted in an increase in conversion. Experiments were conducted with different doses of catalyst, and the optimum dosage of catalyst for a particular feed concentration was determined. A decrease in conversion was observed when the initial concentration of ammonia was increased. CONCLUSION: A study of reaction kinetics showed the effect of reaction time on conversion of urea to ammonia. The catalytic hydrolysis of urea, using aluminium oxide behaved as a first‐order reaction; the rate constant at different temperatures was found, and the activation energy determined. Copyright © 2011 Society of Chemical Industry 相似文献
23.
Proponents of free trade have often hailed international trade as an engine of economic growth. However, the foreign trade sector, like many other sectors in developing countries, frequently involves these countries walking a tightrope between their developmental objectives and environmental goals. In this regard, prioritizing for developing a ‘green’ yet internationally competitive export portfolio provides a quintessential win–win solution to the problem. This study factors in both environmental benignity (indicated by total CO2 emission intensity) as well as trade competitiveness (indicated by revealed comparative advantage index) in identifying the ‘ideal’ Indian export portfolio. The analysis calculates the level of direct and indirect emissions from the foreign trade sector (exports and imports) using the environmental input–output (EIO) matrix for 2003/04 for India that has been jointly developed by researchers from Keio University, Japan, and The Energy and Resources Institute (TERI), New Delhi. The derived basket is compared to the current portfolio to estimate the potential saving from compositional changes and to suggest directions for policymaking to emphasize or de-emphasize the export of certain categories of exports. 相似文献
24.
Particle size effect on the magnetic properties of NiO nanoparticles prepared by a precipitation method 总被引:1,自引:0,他引:1
K. Karthik G. Kalai SelvanM. Kanagaraj S. ArumugamN. Victor Jaya 《Journal of Alloys and Compounds》2011,509(1):181-184
Nickel oxide (NiO) nanoparticles of nominal size range 16 nm and 25 nm were obtained by controlling the calcination temperature. These particles were prepared by the precipitation method. Structural, optical and morphological characterizations were done by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy and scanning electron microscopy. Studies of magnetic measurements (up to 60 kOe) and temperature variations from 2 K to 300 K of the NiO nanoparticles were investigated. Particles of 16 nm exhibited a weak ferromagnetic component and hysteresis loop. There is a increase in coercivity Hc and the remanence Mr at 8 K accompanied by an exchange bias HE. HE monotonically tends to zero as the particles size varied from 16 nm to 25 nm. The hysteresis loop and the size dependent χ are interpreted with the uncompensated surface spins, whereas the transition at 30 K is suggested to be Néel temperature TN of the spins in the core of the 16 nm particles. In addition, the increasing temperature cannot showed an approach to saturation in the magnetization curve, it indicates the possibility of an asperomagnetism and/or spin glass behavior of the NiO nanoparticles. 相似文献
25.
Ashok Kumar Singh N. Chaurasia Shahla Rahmani Jaya Srivastava Bharat Singh 《Catalysis Letters》2004,94(3-4):135-141
The NO/H2 reaction has been studied over a Ni loaded carbon film catalysts using in situ FTIR spectroscopy at the temperature range 25–350°C. On these catalysts, the differences in activity and selectivity were found depending on the nature of the surface functional groups. These differences were correlated with transient infrared spectral features which appeared during the reaction. It has been proved experimentally that the chemical character of the support is of vital importance during the process. The rise in NO conversion and N2 selectivity was observed when the surface of the catalysts was changed by the NH3 chemisorption. Amide and/or imide species formed due to the reduction of ammonium salts of carboxylic acids can play a significant role as active centers during the NO reduction. 相似文献
26.
Stability of a fracture toughness testing geometry is important to determine the crack trajectory and R-curve behavior of the specimen. Few configurations provide for inherent geometric stability, especially when the specimen being tested is brittle. We propose a new geometrical construction called the single edge notched clamped bend specimen (SENCB), a modified form of three point bending, yielding stable cracking under load control. It is shown to be particularly suitable for small-scale structures which cannot be made free-standing, (e.g., thin films, coatings). The SENCB is elastically clamped at the two ends to its parent material. A notch is inserted at the bottom center and loaded in bending, to fracture. Numerical simulations are carried out through extended finite element method to derive the geometrical factor f(a/W) and \(\hbox {K}_{\mathrm{I}}\) for different beam dimensions. Experimental corroborations of the FEM results are carried out on both micro-scale and macro-scale brittle specimens. A plot of \(\hbox {K}_{\mathrm{I}}\) vs a/W, is shown to rise initially and fall off, beyond a critical a/W ratio. The difference between conventional SENB and SENCB is highlighted in terms of \(\hbox {K}_{\mathrm{I}}\) and FEM simulated stress contours across the beam cross-section. The \(\hbox {K}_{\mathrm{IC}}\) ’s of bulk NiAl and Si determined experimentally are shown to match closely with literature values. Crack stability and R-curve effect is demonstrated in a PtNiAl bond coat sample and compared with predicted crack trajectories from the simulations. The stability of SENCB is shown for a critical range of a/W ratios, proving that it can be used to get controlled crack growth even in brittle samples under load control. 相似文献
27.
28.
Acquired immune deficiency syndrome (AIDS) has become a topic of increasing public concern. Several conditions have been described in patients who are afraid that they have acquired AIDS, including depression, somatization disorders, hypochondriasis, adjustment disorders and various psychoses. This paper presents a case study of a young man with persistent fear of having AIDS. In spite of negative HIV test results, the patient still insisted that he suffered from AIDS. The psychiatric diagnosis was major depressive disorder with delusion of having AIDS. The patient was treated with fluoxetine 40 mg qd and sulpiride 400 mg qn. After two weeks on medication, his fear of AIDS subsided and he improved remarkably. The most important intervention in patients with delusion of having AIDS is to identify and treat the underlying psychopathology. The following case is representative of our experience. 相似文献
29.
M. Lakshmi Kantam V. Swarna Jaya M. Jaya Lakshmi B. Ramachandra Reddy B.M. Choudary S.K. Bhargava 《Catalysis communications》2007,8(12):1963-1968
Alumina supported copper (Cu–Al2O3) nanoparticles were prepared and applied for the aziridination of olefins employing [N-(p-tolylsulfonyl)imino]phenyliodinane (PhI = NTs) as nitrene source to afford the corresponding 3-membered cyclic compounds in moderate to excellent yields. Cyclopropanation of several olefins was also carried out by using Cu–Al2O3 nanoparticles and ethyl diazoacetate as a carbene source. The catalyst was recovered by simple centrifugation and reused for four cycles. 相似文献
30.
Sayanti Bhattacharya Jaya P. Kamat Sandip K. Bandyopadhyay Subrata Chattopadhyay 《Food chemistry》2009
The protective activities of Emblica officinalis, Terminalia bellerica and Terminalia chebula ethanol extracts against photosensitization-induced oxidation of rat liver mitochondrial lipid were assessed. All the extracts could effectively prevent lipid peroxidation, as assessed by measuring thiobarbituric acid-reactive substrates, lipid hydroperoxide, conjugated diene and 4-hydroxynonenal. The E. officinalis extract was the most potent, revealing its superior ability to scavenge 1O2. The extracts also afforded excellent protection against iron-mediated lipid peroxidation that might also be useful in reducing photo-induced iron toxicity. The activities of the extracts were primarily due to their constituent phenolics. 相似文献