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31.
Label-free cell separation and sorting in microfluidic systems 总被引:2,自引:0,他引:2
Daniel R. Gossett Westbrook M. Weaver Albert J. Mach Soojung Claire Hur Henry Tat Kwong Tse Wonhee Lee Hamed Amini Dino Di Carlo 《Analytical and bioanalytical chemistry》2010,397(8):3249-3267
Cell separation and sorting are essential steps in cell biology research and in many diagnostic and therapeutic methods. Recently,
there has been interest in methods which avoid the use of biochemical labels; numerous intrinsic biomarkers have been explored
to identify cells including size, electrical polarizability, and hydrodynamic properties. This review highlights microfluidic
techniques used for label-free discrimination and fractionation of cell populations. Microfluidic systems have been adopted
to precisely handle single cells and interface with other tools for biochemical analysis. We analyzed many of these techniques,
detailing their mode of separation, while concentrating on recent developments and evaluating their prospects for application.
Furthermore, this was done from a perspective where inertial effects are considered important and general performance metrics
were proposed which would ease comparison of reported technologies. Lastly, we assess the current state of these technologies
and suggest directions which may make them more accessible. 相似文献
32.
C. Henkel H. Wallis N. Westbrook C.I. Westbrook A. Aspect K. Sengstock W. Ertmer 《Applied physics. B, Lasers and optics》1999,69(4):277-289
We review recent theoretical models and experiments dealing with the diffraction of neutral atoms by a reflection grating,
formed by a standing evanescent wave. We analyze diffraction mechanisms proposed for normal and grazing incidence, point out
their scopes and confront the theory with experiment.
Received: 12 June 1999 / Published online: 8 September 1999 相似文献
33.
Modeling and experimental investigation of methylcyclohexane ignition in a rapid compression machine 总被引:1,自引:0,他引:1
W.J. Pitz C.V. Naik C.K. Westbrook J.P. Orme 《Proceedings of the Combustion Institute》2007,31(1):267-275
A new chemical kinetic reaction mechanism has been developed for the oxidation of methylcyclohexane (MCH), combining a new low temperature mechanism with a recently developed high temperature mechanism. Predictions from this kinetic model are compared with new experimentally measured ignition delay times from a rapid compression machine. Computed results were found to be particularly sensitive to isomerization rates of methylcyclohexylperoxy radicals. Three different methods were used to estimate rate constants for these isomerization reactions. Rate constants based on comparable alkylperoxy radical isomerizations corrected for the differences in the structure of MCH and the respective alkane, predicted ignition delay times in very poor agreement with the experimental results. The most significant drawback was the complete absence of a region of negative temperature coefficient (NTC) in the model results using this method, although a prominent NTC region was observed experimentally. Alternative estimates of the isomerization reaction rate constants, based on the results from previous experimental studies of low temperature cyclohexane oxidation, provided much better agreement with the present experiments, including the pronounced NTC behavior. The most important feature of the resulting methylcyclohexylperoxy radical isomerization reaction analysis was found to be the relative rates of isomerizations that proceed through 5-, 6-, and 7-membered transition state ring structures and their different impacts on the chain branching behavior of the overall mechanism. Theoretical implications of these results are discussed, with particular attention paid to how intramolecular H atom transfer reactions are influenced by the differences between linear alkane and cycloalkane structures. 相似文献
34.
T.?SchummEmail author J.?Estève C.?Figl J.-B.?Trebbia C.?Aussibal H.?Nguyen D.?Mailly I.?Bouchoule C. I.?Westbrook A.?Aspect 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,32(2):171-180
We present a detailed model describing the effects of
wire corrugation on the trapping potential experienced by a cloud
of atoms above a current carrying micro wire. We calculate the
distortion of the current distribution due to corrugation and then
derive the corresponding roughness in the magnetic field above the
wire. Scaling laws are derived for the roughness as a function of
height above a ribbon shaped wire. We also present experimental
data on micro wire traps using cold atoms which complement some
previously published measurements [CITE] and which
demonstrate that wire corrugation can satisfactorily explain our
observations of atom cloud fragmentation above electroplated gold
wires. Finally, we present measurements of the corrugation of new
wires fabricated by electron beam lithography and evaporation of
gold. These wires appear to be substantially smoother than
electroplated wires. 相似文献
35.
Sumetsky M Dulashko Y Fleming JW Kortan A Reyes PI Westbrook PS 《Optics letters》2004,29(12):1315-1317
The most accurate approaches to fabrication of diffraction gratings are known to be the lithographic and holographic methods. The lithographic methods allow fabrication of arbitrarily chirped gratings whose performance, however, is degraded by stitching errors. The holographic methods are free from stitching errors; however, they are limited in the achievable spatial variations of their grating periods. We suggest a method of diffraction grating modification by nonuniform heating and stretching that is much more flexible than the holographic approach and does not suffer from the problem of stitching error. We demonstrate our approach for quartz phase masks that have a characteristic grating period of 1 microm and a length of several centimeters. Our approach allows the grating periods of the phase masks to vary in a range from a few picometers to a few nanometers and a spatial resolution of a few millimeters. It is shown that the grating period can be modified with a negligible effect on the profile of the gratings. 相似文献
36.
We measured the polarization dependence of light scattered from a tilted fiber grating and found disagreement with previous volume-current perturbation analysis. However, by including the longitudinal E field of the guided wave we were able to obtain good agreement, demonstrating that, although it is small, this component cannot be neglected when scattering of weakly guided waves is considered. A first-order approximation formula for the polarization dependence was also obtained and is shown to be accurate within most of the resonance band of scattering. 相似文献
37.
We demonstrate a fourth-order polarimeter that employs two-photon detection to measure the fourth-order polarization coherency matrix (FOCM) of an optical signal. We measure the FOCM of picosecond pulses subjected to polarization mode dispersion (PMD). The fourth-order polarimeter distinguishes different PMD states even when the state of polarization, including the degree of polarization, is constant. 相似文献
38.
Seidelin S Gomes JV Hoppeler R Sirjean O Boiron D Aspect A Westbrook CI 《Physical review letters》2004,93(9):090409
We report an experiment measuring simultaneously the temperature and the flux of ions produced by a cloud of triplet metastable helium atoms at the Bose-Einstein critical temperature. The onset of condensation is revealed by a sharp increase of the ion flux during evaporative cooling. Combining our measurements with previous measurements of ionization in a pure Bose-Einstein condensate, we extract an improved value of the scattering length a=11.3(+2.5)(-1.0) nm. The analysis includes corrections that take into account the effect of atomic interactions on the critical temperature, and thus an independent measurement of the scattering length would allow a new test of these calculations. 相似文献
39.
Oh K Westbrook PS Atkins RM Reyes P Windeler RS Reed WA Stockert TE Brownlow D Digiovanni D 《Optics letters》2002,27(7):488-490
A silica optical fiber doped with Sb is fabricated with a refractive-index profile that is comparable with standard single-mode fiber. In D(2)-loaded samples, we observe UV photosensitivity with an initial refractive-index-modulation growth rate six times higher than that of the equivalent Ge-doped standard fibers. Enhanced temperature stability of the Bragg grating strength up to 200 degrees C is also observed. Grating growth kinetics in the Sb-doped fiber is compared with those of other Ge-doped photosensitive fibers. 相似文献
40.
Sirjean O Seidelin S Gomes JV Boiron D Westbrook CI Aspect A Shlyapnikov GV 《Physical review letters》2002,89(22):220406
We have studied ionizing collisions in a BEC of metastable He. Measurements of the ion production rate combined with measurements of the density and number of atoms for the same sample allow us to estimate both the two- and three-body contributions to this rate. A comparison with the decay of the atom number indicates that ionizing collisions are largely or wholly responsible for the loss. Quantum depletion makes a substantial correction to the three-body rate constant. 相似文献