全文获取类型
收费全文 | 255篇 |
免费 | 12篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 2篇 |
综合类 | 1篇 |
化学工业 | 58篇 |
金属工艺 | 8篇 |
机械仪表 | 39篇 |
建筑科学 | 6篇 |
能源动力 | 10篇 |
轻工业 | 19篇 |
水利工程 | 5篇 |
无线电 | 7篇 |
一般工业技术 | 96篇 |
冶金工业 | 12篇 |
原子能技术 | 2篇 |
自动化技术 | 12篇 |
出版年
2023年 | 3篇 |
2022年 | 13篇 |
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 9篇 |
2017年 | 8篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 8篇 |
2013年 | 9篇 |
2012年 | 21篇 |
2011年 | 12篇 |
2010年 | 11篇 |
2009年 | 8篇 |
2008年 | 13篇 |
2007年 | 11篇 |
2006年 | 11篇 |
2004年 | 1篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有277条查询结果,搜索用时 484 毫秒
11.
Investigation of the Transition State in the Wear of Polyphenylene Sulfide Sliding Against Steel 总被引:2,自引:0,他引:2
The effect of sliding variables, including counterface roughness, sliding speed, and contact pressure, on the run-in state of wear and friction was studied. Sliding was performed in the pin-on-disk configuration with a polyphenylene sulfide (PPS) pin resting on the flat steel counterface. Some experiments were also run to study the effect of air cooling and heating. Optical microscopy and scanning electron microscopy were used to study the shape and size of the wear debris, worn pin surface, and the transfer film formed on steel counterfaces. It was found that friction and wear in the run-in state were significantly affected by the sliding variables studied and their influence was closely related to the development of a transfer film during the run-in state. If the transfer film developed during initial sliding, the coefficient of friction increased and wear rate decreased. The wear rate in the run-in state increased with the increase in initial counterface roughness and there was an optimal counterface roughness of 0.06 m Ra for minimum steady state wear rate. A higher applied load led to a higher wear rate in the run-in state but that was not the case with steady state wear rate. 相似文献
12.
13.
14.
Tuning of Cloud Point by the Nature of Surfactant Headgroup: Influence of Counterion and Additives 下载免费PDF全文
Sanjay Kumar Yadav Ran Bahadur Yadav Sanjeev Kumar 《Journal of surfactants and detergents》2016,19(5):1063-1069
Work was performed to distinguish the role of sulfonate (–SO3 ?) and sulfate (–OSO3 ?) with respect to the micellization and clouding phenomenon in ionic surfactant solutions. The clouding phenomenon is a recent addition to the conventional one observed with nonionic surfactants. Three ionic surfactants [sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and sodium dodecylsulfonate (SDSo)] are chosen and the effects of added tetra-n-pentylammonium bromide (TPeAB) and benzyl tributylammonium bromide (BTAC) have been studied on micellization and clouding behaviors in aqueous solution. Based on critical micelle concentration (CMC) and cloud point (CP) measurements, the following order has been observed: SDBS < SDS < SDSo. Though both SDBS and SDSo contain sulfonate groups, they are found at the two ends of the ordering. Therefore, the role of the phenyl ring is also having importance in clouding phenomena. For a typical surfactant, TPeAB was found to be more effective than BTAC. Based on the CP studies, two compositions of SDSo + TPeAB/BTAC were chosen and the effects of different additives (carbohydrate, amino acid, and l-ascorbic acid) on the CP were investigated. Additive may either decrease or increase CP, depending on the structure of the counterion or additive. The present work shows a few novelties: (1) headgroup/counterion dependence of CP and (2) hydrophobicity of counterion/surfactant has an important bearing on the phenomenon. The data can be utilised in improving cloud point extraction methodologies (CPEMs). 相似文献
15.
Keyur Patel Bhavesh Bharatiya Yogesh Kadam Pratap Bahadur 《Journal of surfactants and detergents》2010,13(1):89-95
Aqueous solution properties of polyethylene oxide–block-polypropylene oxide–block-polyethylene oxide TBP [(PEO)103(PPO)39(PEO)103] were studied in the presence of sodium salts with different anions (NaI, NaBr, NaCl, NaF, Na2SO4, Na3PO4) to investigate unimer-to-micelle transition [critical micelle concentration (CMC), critical micellization temperature (CMT)],
micelle size and the phase separation (cloud point). This TBP, due to its very hydrophilic (80% PEO) nature does not form
micelles at ambient temperatures. Micellization can be induced much below its CMT in water on addition of sodium salts having
different anions. Analytical methods viz. fluorescence, FTIR and dynamic light scattering (DLS) were used to monitor the salt-induced
micellization. The hydration of respective anion and resultant contribution to its salting-out effect was found to be the
governing factor in promoting micellization. The presence of salt decreases the CMC, CMT and phase separation temperature.
The salts affect the aggregation process in agreement with an order mentioned in Hofmeister series. 相似文献
16.
Bioactivity and magnetic properties were investigated in glass and glass ceramics based on the SiO2–Na2O–Fe2O3–CaO–P2O5–B2O3 system to find their suitability as thermoseed for hyperthermia treatment of cancer. The effect of change in compositions on bioactivity was examined in simulated body fluids. The glass ceramic samples exhibit Na3CaSi3O8 and Na3-XFeXPO4 phases. After dipping the glass ceramic samples in simulated body fluids silica hydrogel first forms, followed by an amorphous calcium phosphate layer. Magnetic and microwave resonance experiments further demonstrate the potential of these glass ceramics for possible use in hyperthermia. 相似文献
17.
S. Bahadur 《Polymer Engineering and Science》1973,13(4):266-272
A number of thermoplastic polymers were tested in tension to investigate their strain hardening behavior. A strain hardening equation has been proposed in terms of the true stress, true strain and two constants σo and m. The three material constants, viz. σo m and the true fracture strain, are shown to be adequate to describe completely the material's nonlinear viscoelastic or the so-called “plastic” behavior. The true stress-strain data for the polymers rolled to varying amounts of cold-work fits the strain hardening plot of the unrolled material. The same strain hardening equation, therefore, applies to rolled materials as well. The procedure for predicting the tensile strength of rolled materials is given. 相似文献
18.
Niru Kumari Vaibhav Bahadur Marc Hodes Todd Salamon Paul Kolodner Alan Lyons Suresh V Garimella 《International Journal of Heat and Mass Transfer》2010,53(15-16):3346-3356
Enhancement of forced convective heat transport through the use of evaporating mist flow is investigated analytically and by numerical simulation. A two-phase mist, consisting of finely dispersed water droplets in an airstream, is introduced at the inlet of a longitudinally-finned heat sink. The latent heat absorbed by the evaporating droplets significantly reduces the sensible heating of the air inside the heat sink which translates into higher heat-dissipation capacities. The flow and heat transfer characteristics of mist flows are studied through a detailed numerical analysis of the mass, momentum and energy transport equations for the mist droplets and the airstream, which are treated as two separate phases. The coupling between the two phases is modeled through interaction terms in the transport equations. The effects of inlet mist droplet size and concentration on the thermal performance of the heat sink are analyzed parametrically. The results provide insight into the complex transport processes associated with mist flows. The simulations indicate that significantly higher heat transfer coefficients are obtained with mist flows as compared to air flows, highlighting the potential for the use of mist flows for enhanced thermal management applications. 相似文献
19.
D. Bahadur D. Chakravorty D. Chattopadhyaya S. Datta S. K. Khan S. Mitra S. Ram D. Roy K. Sengupta 《Journal of Materials Science》1986,21(8):2793-2797
The effect of bismuth, silver oxide and palladium on the crystallization of yttrium iron garnet in Na2O-SiO2-Y2O3-Fe2O3 glass-ceramics has been investigated by X-ray diffraction thermal analysis, magnetic measurements and optical microscopy. It is found that the magnetic properties of these glass-ceramics can be altered significantly by a change in the nucleating agents and the heat treatment schedule. This behaviour is explained on the basis of the microstructure and the volume fraction of the different magnetic phases crystallized within the glasses. 相似文献
20.
The transfer of material in sliding between polyethylene films and polytetrafluoroethylene, polyvinyl chloride, polypropylene and polymethyl methacrylate discs and between Mylar films and polyethylene and polyvinyl chloride discs was investigated. Infrared spectroscopy and differential thermal analysis were used to detect the direction of material transfer. The transfer process was studied as a function of sliding time, speed and load. It was found that the transfer occurs under all conditions of rubbing and invariably occurs from a material of low cohesive energy density to one of higher cohesive energy density. The thickness of the layer of material transferred has been estimated as a function of the above sliding variables by quantitative infrared spectroscopy. It is found that the layer thickness increases with sliding speed and time but decreases with load. The effect of this material transfer on the coefficient of friction has also been studied for one combination. 相似文献