全文获取类型
收费全文 | 856篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 492篇 |
晶体学 | 9篇 |
力学 | 28篇 |
数学 | 100篇 |
物理学 | 238篇 |
出版年
2023年 | 9篇 |
2022年 | 6篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2017年 | 6篇 |
2016年 | 18篇 |
2015年 | 13篇 |
2014年 | 10篇 |
2013年 | 38篇 |
2012年 | 44篇 |
2011年 | 47篇 |
2010年 | 25篇 |
2009年 | 15篇 |
2008年 | 34篇 |
2007年 | 31篇 |
2006年 | 33篇 |
2005年 | 41篇 |
2004年 | 23篇 |
2003年 | 24篇 |
2002年 | 22篇 |
2001年 | 13篇 |
2000年 | 37篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 15篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 21篇 |
1981年 | 14篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1974年 | 9篇 |
1973年 | 10篇 |
1972年 | 8篇 |
1966年 | 6篇 |
排序方式: 共有867条查询结果,搜索用时 15 毫秒
61.
Michael Campbell Yatao Yang Peter A. Wallace A. Sheila Holmes-Smith 《Optical Review》1997,4(1):A111-A113
This paper reports the development and characterisation of a multipoint quasi-distributed optical fiber sensor for pH measurement. The system is based on a 170 m length of 200 μm core diameter plastic cladding silica fiber where sections of cladding have been removed and replaced with dye immobilised sol-gel glass to form sensing points. Evanescent wave excitation of a dye, immobilised within 2 mm long sections of cladding, enables the pH value of any spillage material to be determined by optical time domain reflectometry along the length of the fiber. The results suggest a spatial resolution of better than 2.5 meters for this fiber system and indicate that this arrangement could form the basis of a practical sensor/actuator system for chemical spillage, provided that suitable dye/analyte combinations are available. 相似文献
62.
This paper describes a combined experimental and numerical study of scalar transport in spatially developing, two-stream,
turbulent mixing layers with velocity ratios of approximately 2:1. The experimental mixing layer was created by an S-shaped
splitter plate mounted in a wind tunnel, and the concentration field was realized by releasing incense smoke into the high-speed
side boundary layer above the splitter plate. Simultaneous measurements of the velocity and concentration fields were performed.
A 12-sensor hot-wire probe was used to measure the velocity field and its gradients, while the concentration field was recorded
with digital photographs of the laser-illuminated smoke. In parallel, a large-eddy simulation (LES) of the spatially developing
mixing layer was carried out. Auxiliary turbulent boundary layer LES were used to provide high quality inflow boundary conditions
for the velocity and concentration fields. By synchronizing the velocity and concentration measurements, concentration fluxes
were also determined. Octant analysis based on the sign combinations of the velocity and concentration fuctuations was performed
on the flux data to investigate the scalar transport processes. It was found that octants compatible with mean gradient transport
of the scalar contribute most to the scalar fluxes. Conditional planar averages of scalar and momentum fluxes were obtained
to determine their spatial distribution with respect to the organized roller and rib vortices of the mixing layer, and distinct
patterns were observed. The simulation provided additional insight about the flow and scalar flux distribution topology. This
topology was found to be partially compatible with simple models of roller and rib vortices that transport the scalar in a
mean gradient sense. 相似文献
63.
There have been rapid advances in the development of new materials for use in electrode–tissue interfacing. The development of conducting polymers, conducting hydrogels, carbon nanotubes, graphene and other conducting materials has provided a rich landscape for controlling charge transfer at the electrode–tissue interface and hence to monitor and manipulate cell behaviour. These materials have been used in tissue-engineered constructs to direct and control cell proliferation, growth and differentiation. However, their translation to clinical devices has been less successful. In this review, the use of electroanalytical techniques to develop an understanding of charge transfer at the electrode–tissue interface is discussed. In particular, the impact of solution and electrode conditions on charge injection capacity is demonstrated. The importance of standardised testing methods and the correlation of electrochemical and electrophysiological performance show the limitations of empirical studies and help define key electrode properties for clinical devices. The development of a sound theoretical basis for charge transfer at this increasingly important interface is being advocated to improve clinical outcomes and device lifetime and reduce power usage. 相似文献
64.
Phospholipid lung surfactant and nanoparticle surface toxicity: Lessons from diesel soots and silicate dusts 总被引:3,自引:0,他引:3
William E. Wallace Michael J. Keane David K. Murray William P. Chisholm Andrew D. Maynard Tong-man Ong 《Journal of nanoparticle research》2007,9(1):23-38
Because of their small size, the specific surface areas of nanoparticulate materials (NP), described as particles having at
least one dimension smaller than 100 nm, can be large compared with micrometer-sized respirable particles. This high specific
surface area or nanostructural surface properties may affect NP toxicity in comparison with micrometer-sized respirable particles
of the same overall composition. Respirable particles depositing on the deep lung surfaces of the respiratory bronchioles
or alveoli will contact pulmonary surfactants in the surface hypophase. Diesel exhaust ultrafine particles and respirable
silicate micrometer-sized insoluble particles can adsorb components of that surfactant onto the particle surfaces, conditioning
the particles surfaces and affecting their in vitro expression of cytotoxicity or genotoxicity. Those effects can be particle surface composition-specific. Effects of particle
surface conditioning by a primary component of phospholipid pulmonary surfactant, diacyl phosphatidyl choline, are reviewed
for in vitro expression of genotoxicity by diesel exhaust particles and of cytotoxicity by respirable quartz and aluminosilicate kaolin
clay particles. Those effects suggest methods and cautions for assaying and interpreting NP properties and biological activities. 相似文献
65.
66.
67.
Abouderbala LO Belcher WJ Boutelle MG Cragg PJ Dhaliwal J Fabre M Steed JW Turner DR Wallace KJ 《Chemical communications (Cambridge, England)》2002,(4):358-359
A series of podands based on three hydrogen bonding 'arms' have been prepared and their affinities for simple inorganic anions measured. 相似文献
68.
R. Wallace 《Chemical physics》1984,88(2):247-260
A general expression for the rovib kinetic energy operator in a system of orthogonal internal coordinates is derived for arbitrary amplitudes of motion. Plots of the molecular potential in such coordinates serve to determine coordinate subsets in which the potential approaches separability. A revision of previous theory for the three-body problem is presented. A rovib hamiltonian for non-branched four-atom molecules (such as C2H2) is derived. Certain features of application to polyatomic (five-atom) molecules are considered. 相似文献
69.
T. P. Wallace M. T. Volosin R. G. Delumyea A. D. Gingello 《Journal of Polymer Science.Polymer Physics》1972,10(2):193-200
Recent literature reports from three laboratories have treated the refraction correction for the Sofica and a noncommercial light scattering photometer. Our re-evaluation of the data contained in these reports, as well as our experiments, indicate that the usually cited n2 refraction correction has not been unquestionably established for these instruments. In some cases, imprecise experimental techniques have been used to support this particular form of the correction. In addition, we find the optical system of the Sofica instrument results in the detector seeing vertically past the horizontal edge of the illuminated volume in violation of a basic assumption in the deduction of the n2 correction. Our experiments, as well as our interpretation of recent literature data, support an exponent of less than 2.0 for the Sofica apparatus, which is consistent with an instrument whose detector views outside the illuminated volume. However, the experimental methods available to evaluate the exponent lack the desired precision. 相似文献
70.