全文获取类型
收费全文 | 619篇 |
免费 | 43篇 |
专业分类
电工技术 | 24篇 |
化学工业 | 71篇 |
金属工艺 | 17篇 |
机械仪表 | 22篇 |
建筑科学 | 27篇 |
能源动力 | 24篇 |
轻工业 | 20篇 |
水利工程 | 2篇 |
石油天然气 | 5篇 |
无线电 | 108篇 |
一般工业技术 | 166篇 |
冶金工业 | 94篇 |
原子能技术 | 3篇 |
自动化技术 | 79篇 |
出版年
2023年 | 5篇 |
2022年 | 2篇 |
2021年 | 14篇 |
2020年 | 12篇 |
2019年 | 21篇 |
2018年 | 28篇 |
2017年 | 13篇 |
2016年 | 17篇 |
2015年 | 15篇 |
2014年 | 9篇 |
2013年 | 25篇 |
2012年 | 26篇 |
2011年 | 32篇 |
2010年 | 34篇 |
2009年 | 24篇 |
2008年 | 24篇 |
2007年 | 29篇 |
2006年 | 27篇 |
2005年 | 21篇 |
2004年 | 25篇 |
2003年 | 19篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 18篇 |
1999年 | 19篇 |
1998年 | 31篇 |
1997年 | 24篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1981年 | 4篇 |
1976年 | 12篇 |
1970年 | 1篇 |
1968年 | 4篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1959年 | 3篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有662条查询结果,搜索用时 24 毫秒
651.
Michael T.M. Wang Kalaivarny Ganesalingam Chee Seang Loh Trisha Alberquerque Suhaila Al-Kanani Stuti L. Misra Jennifer P. Craig 《Contact lens & anterior eye》2017,40(1):53-58
Purpose
To assess the effects of two weeks of regular phospholipid liposomal spray application on lipid layer grade, tear film stability, subjective comfort, visual acuity, and lipid deposition in silicone hydrogel contact lens wearers.Methods
Thirty-one existing contact lens wearers were enrolled and fitted with two week planned replacement silicone hydrogel contact lenses (Acuvue® Oasys®) in a prospective, randomized, paired-eye, investigator-masked trial. A phospholipid liposomal spray (Tears Again®) was applied to one eye (randomized) four times daily for two weeks. LogMAR high contrast visual acuity (VA), low contrast glare acuity (LCGA), non-invasive tear film break-up time (NIBUT), and lipid layer grade (LLG) were measured at baseline and day 14, in both treated and control eyes. Subjective comfort relative to baseline, and spectrofluorophotometric assessment of contact lens surface lipid deposition were also assessed on day 14.Results
All measurements did not differ at baseline between treated and control eyes. Lipid layer thickness and tear film stability were increased on day 14 in treated eyes (all p < 0.05), but not in control eyes (all p > 0.05). A greater proportion of participants reported improved comfort in the treated eye relative to the control eye (p = 0.002). There were no significant differences in visual acuity or in contact lens surface lipid deposition, between treated and control eyes, on day 14 (all p > 0.05).Conclusion
The phospholipid liposomal spray increased tear film stability, lipid layer thickness and subjective comfort in silicone hydrogel contact lens wearers, without adversely affecting visual acuity or contact lens surface lipid deposition. 相似文献652.
ZhiBin Xie Anupam Midya Kian Ping Loh Stefan Adams Daniel John Blackwood John Wang Xuanjun Zhang Zhikuan Chen 《Progress in Photovoltaics: Research and Applications》2010,18(8):573-581
Two novel organic dyes have been synthesized using electron rich phenothiazine as electron donors and oligothiophene vinylene as conjugation spacers. The two dyes (2E)‐2‐cyano‐3‐(5‐(5‐((E)‐2‐(10‐(2‐ethylhexyl)‐10H‐phenothiazin‐7‐yl)vinyl)thiophen‐2‐yl)thiophen‐2‐yl)acrylic acid (PTZ‐1) and (2E)‐3‐(5‐(5‐(4,5‐bis((E)‐2‐(10‐(2‐ethylhexyl)‐10H‐phenothiazin‐3‐yl)vinyl)thiophen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)‐2‐cyanoacrylic acid (PTZ‐2) were fully characterized and employed in dye‐sensitized solar cells (DSCs) to explore the effect of disubstituted donors on photovoltaic (PV) performance. The solar cells sensitized by the PTZ1 dye have a high IPCE plateau of 80% and achieve a short‐circuit photocurrent density of 12.98 mA/cm2, an open‐circuit voltage of 0.713 V, and a fill factor (ff) of 66.6%, corresponding to a conversion efficiency of 6.17% under AM 1.5 100 mW/cm2 illumination. The different performance of the solar cells based on the two dyes can be understood from the studies of the electron kinetics by electrochemical impedance spectroscopy (EIS). These investigations reveal that disubstituted donors in the organic sensitizers of three or more conjugation units deteriorate the PV performance due to enhanced recombination. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
653.
Laura Hanske Gunnar Loh Silke Sczesny Michael Blaut Annett Braune 《Molecular nutrition & food research》2010,54(10):1405-1413
The impact of human intestinal bacteria on the bioavailability of the prenylflavonoid xanthohumol (XN) was studied by comparing germ‐free (GF) and human microbiota‐associated (HMA) rats. After XN application, XN, XN conjugates, and isoxanthohumol (IX) conjugates occurred in blood samples of GF and HMA rats, whereas IX was detected only in the blood of HMA rats. Overall excretion of XN and its metabolites within 48 h was only 4.6% of the ingested dose in GF rats and 4.2% in HMA rats, feces being the major route of excretion. While both GF and HMA rats excreted XN, IX, and their conjugates with urine and feces, 8‐prenylnaringenin and its corresponding conjugates were exclusively observed in the feces of HMA rats. The microbial formation of 8‐prenylnaringenin was confirmed by incubation of XN and IX with human fecal slurries. The amount of conjugates excreted in urine and feces was lower in HMA rats compared to GF rats indicating their hydrolysis by human intestinal microbiota. Thus, the impact of bacteria on the XN metabolism in the gut may affect the in vivo effects of ingested XN. 相似文献
654.
Siti Salwa Hashim Mahendra Rao Somalu Kee Shyuan Loh Shaomin Liu Wei Zhou Jaka Sunarso 《International Journal of Hydrogen Energy》2018,43(32):15281-15305
Hydrogen is considered a fuel of the future due to its diversified supply and zero greenhouse gas emission. The application of advanced membrane technology for hydrogen separation within the larger hydrogen production process context can substitute the use of more expensive and energy intensive cryogenic distillation and pressure swing adsorption technologies. This review overviews the basic aspects and progresses in perovskite-based proton conducting hydrogen separation membranes. Different configurations such as symmetric, asymmetric, hollow fiber, and surface modified perovskite membranes with various compositions are discussed and summarized. The challenges and future directions of such membranes are also elaborated. 相似文献
655.
Effects of pre-treatments and interlayers on the nucleation and growth of diamond coatings on titanium substrates 总被引:1,自引:0,他引:1
During diamond deposition on titanium substrates, two processes exist: (1) diffusion of hydrogen into a titanium substrate and the formation of hydride thereby degrading the mechanical properties of the substrate; and (2) competition among the rapid diffusion of carbon atoms into substrates, the formation of carbide and the nucleation of diamond crystals (thereby affecting the nucleation and growth rate of the diamond coating). To increase the diamond nucleation rate and prevent the rapid diffusion of hydrogen and carbon into the substrate, different surface treatments and interlayers were studied in this paper. Results showed that polishing with diamond pastes and ultrasonic pre-treatment in diamond suspensions will significantly increase the nuclei density of diamond crystals. However, the diffusion of hydrogen into the substrate could not be prevented. Pre-etching of the titanium substrate using hydrogen plasma for a short time significantly increased the nuclei density of diamond crystals. Results showed that on a TiN interlayer, there was no significant improvement in diamond nucleation and growth, and the deposited diamond coatings showed poor adhesion. New diamond crystals were formed on the DLC interlayer in which DLC acted as the precursor for diamond nucleation. However, the so-formed diamond coating showed spallation. The plasma nitrided layer could prevent the rapid diffusion of hydrogen and carbon into the titanium substrate, but results showed a relatively low nucleation density of diamond crystals and poor adhesion. A graded interlayer combining plasma nitriding followed by plasma carbonitriding was effective in preventing the rapid diffusion of hydrogen and carbon into the substrate and improving the nucleation rate and adhesion of diamond coating. 相似文献
656.
G. P. Lucas J. Cory R. C. Waterfall W. W. Loh F. J. Dickin 《Flow Measurement and Instrumentation》1999,10(4):408-258
This paper describes a dual-plane Electrical Resistance Tomography (ERT) system for measuring the local solids volume fraction distribution and the local solids axial velocity distribution in solids–liquid flows. The paper also describes a local, intrusive conductivity probe system for providing reference measurements of the distributions obtained using the dual-plane ERT system. Experiments were performed using both the ERT system and the local probe system in vertically upward and inclined solids–water flows. Good agreement between the two techniques was observed. The local solids volume fraction distribution and the local solids axial velocity distribution obtained using the ERT system enable good estimates to be made of the mean solids volume fraction, the mean solids velocity and the solids volumetric flow rate. 相似文献
657.
The identification of key factors for construction project success enables appropriate allocation of limited resources. Most of the related past work only identified critical success factors for construction projects in general. The present study seeks to distinguish these factors according to the project objectives of budget, schedule, and quality. The analytic hierarchy process is adopted to determine the relative importance of success-related factors. A hierarchical model for construction project success is presented. Sixty-seven success-related factors are considered. These factors are grouped under four main project aspects, namely, project characteristics, contractual arrangements, project participants, and interactive processes in the hierarchical model for project success. A questionnaire was developed to facilitate systematic data collection in this study. Experts with an overall average of 20 years of experience in the construction industry were invited to participate in the survey. Critical success factors addressing budget performance, schedule performance, quality performance, and overall project success are identified. Some pertinent findings of the study are discussed. Comparisons with findings of previous studies using neural network approach are also presented. 相似文献
658.
Yongqing Fu Bibo Yan Nee Lam Loh Chang Q. Sun Peter Hing 《Journal of Materials Science》1999,34(10):2269-2283
The nucleation and growth of diamond coatings on pure Ti substrate were investigated using microwave plasma assisted chemical vapor deposition (MW-PACVD) method. The effects of hydrogen plasma, plasma power, gas pressure and gas ratio of CH4 and H2 on the microstructure and mechanical properties of the deposited diamond coatings were evaluated. Results indicated that the nucleation and growth of diamond crystals on Ti substrate could be separated into different stages: (1) surface etching by hydrogen plasma and the formation of hydride; (2) competition between the formation of carbide, diffusion of carbon atoms and diamond nucleation; (3) growth of diamond crystals and coatings on TiC layer. During the deposition of diamond coatings, hydrogen diffused into Ti substrate forming titanium hydride and led to a profound microstructure change and a severe loss in impact strength. Results also showed that pre-etching of titanium substrate with hydrogen plasma for a short time significantly increased the nuclei density of diamond crystals. Plasma power had a significant effect on the surface morphology and the mechanical properties of the deposited diamond coatings. The effects of gas pressure and gas ratio of CH4 and H2 on the nucleation, growth and properties of diamond coatings were also studied. A higher ratio of CH4 during deposition increased the nuclei density of diamond crystals but resulted in a poor and cauliflower coating morphology. A lower ratio of CH4 in the gas mixture produced a high quality diamond crystals, however, the nuclei density and the growth rate decreased dramatically. 相似文献
659.
Rahoma S. Mohamed Watson Loh Antonio C. S. Ramos Claudio C. Delgado Valdeci R. Almeida 《Petroleum Science and Technology》1999,17(7):877-896
A fundamental understanding of the aggregation and precipitation of asphaltenes in petroleum crudes is important for the development of preventive and curative measures for the potential problem of asphaltene deposition occurring during production, transport and refining operations. The question of reversibility of asphaltene precipitation, yet a controversial issue, is crucial for a clear and unequivocal understanding of the precipitation phenomenon, development of mathematical models that describe the behavior of asphaltenes in petroleum fluids, and the design of inhibitors. In this work, the behavior of precipitated asphaltenes in Brazilian crude tank oil samples following flocculant removal and gradual addition of fresh oil was investigated. The results obtained revealed a re-dissolution of precipitated asphaltene particles following flocculant removal and oil addition. On the inhibition of asphaltene precipitation, the capacity of a number of surfactants and block copolymers to inhibit asphaltene precipitation and deposition was also examined. Ethoxylated Nonylphenols and Hexadecyl Trimethyl Ammonium Bromide displayed highest capacity in the inhibition of asphaltene deposition. 相似文献
660.
Said Quqa Luca Landi Kenneth J. Loh 《Computer-Aided Civil and Infrastructure Engineering》2023,38(17):2426-2442
Sensing skins and electrical impedance tomography constitute a convenient and inexpensive alternative to dense sensor networks for distributed sensing in civil structures. However, their performance can deteriorate with the aging of the sensing film. Guaranteeing high identification performance after minor lesions is crucial to improving their ability to identify structural damage. In this paper, electrical resistance tomography is used to identify the crack locations in nanocomposite paint sprayed onto structural components. The main novelty consists of using crack annotations collected during visual inspections to improve the crack identification performance of deep neural networks trained using simulated datasets through transfer learning. Transfer component analysis is employed for simulation-to-real information transfer and applied at a population level, extracting low-dimensional domain-invariant features shared by simulated models and structures with similar geometry. The results show that the proposed method outperforms traditional approaches for crack localization in complex damage patterns. 相似文献