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991.
992.
Effects of Refractive Index and Viscosity on Fluorescence and Anisotropy Decays of Enhanced Cyan and Yellow Fluorescent Proteins 总被引:1,自引:1,他引:0
The fluorescence lifetime strongly depends on the immediate environment of the fluorophore. Time-resolved fluorescence measurements of the enhanced forms of ECFP and EYFP in water–glycerol mixtures were performed to quantify the effects of the refractive index and viscosity on the fluorescence lifetimes of these proteins. The experimental data show for ECFP and EYFP two fluorescence lifetime components: one short lifetime of about 1 ns and a longer lifetime of about 3.7 ns of ECFP and for EYFP 3.4. The fluorescence of ECFP is very heterogeneous, which can be explained by the presence of two populations: a conformation (67% present) where the fluorophore is less quenched than in the other conformation (33% present). The fluorescence decay of EYFP is much more homogeneous and the amplitude of the short fluorescence lifetime is about 5%. The fluorescence anisotropy decays show that the rotational correlation time of both proteins scales with increasing viscosity of the solvent similarly as shown earlier for GFP. The rotational correlation times are identical for ECFP and EYFP, which can be expected since both proteins have the same shape and size. The only difference observed is the slightly lower initial anisotropy for ECFP as compared to the one of EYFP. 相似文献
993.
994.
Different from organic fluorescence dyes, fluorescent lanthanide complexes have the fluorescence properties of long fluorescence lifetime, large Stokes shift and sharp emission profile, which makes them favorable be used as the fluorescent labeling reagents for microsecond time-resolved fluorescence bioassay. Lanthanide complex-based fluorescence labels have been successfully used for highly sensitive time-resolved fluorescence immunoassay, DNA hybridization assay, cell activity assay, and bioimaging microscopy assay. Since the technique allows easy distinction of the specific fluorescence signal of the long-lived label from short-lived background noises associated with biological samples, scattering lights (Tyndall, Rayleigh and Raman scatterings) and the optical components (cuvettes, filters and lenses), the sensitivity of fluorescence bioassay has been remarkably improved. This paper summarized the recent developments of lanthanide complex-based fluorescence labels and their applications in time-resolved fluorescence bioassays mainly based on the authors’ researches and relative publications. 相似文献
995.
We present applications of polar plots for analyzing fluorescence lifetime data acquired in the frequency domain. This graphical,
analytical method is especially useful for rapid FLIM measurements. The usual method for sorting out and determining the underlying
lifetime components from a complex fluorescence signal is to carry out the measurement at multiple frequencies. When it is
not possible to measure at more than one frequency, such as rapid lifetime imaging, specific features of the polar plot analysis
yield valuable information, and provide a diagnostic visualization of the participating fluorescent species underlying a complex
lifetime distributions. Data are presented where this polar plot presentation is useful to derive valuable, unique information
about the underlying component distributions. We also discuss artifacts of photolysis and how this method can also be applied
to samples where each fluorescence species shows a continuous distribution of lifetimes. Polar plots of frequency-domain data
are commonly used for analysis of dielectric relaxation experiments (Cole–Cole plots), which have proved to be exceptionally
useful in that field for decades. We compare this analytical tool that is well developed and extensively used in dielectric
relaxation and chemical kinetics to fluorescence measurements. 相似文献
996.
Five two-photon excitable dipyrrylmetheneboron difluoride labels (dipyrrylmethene-BF2 labels) with fluorescence emission maximum between 530 and 590 nm, and a frequently used rhodamine label, TAMRA, were conjugated to aminomodified oligonucleotides. The performance of the labeled oligonucleotides was studied in a separation-free nucleic acid hybridization assay using ArcDia™ TPX bioaffinity assay technology. The results show that oligonucleotide conjugates of dipyrrylmethene-BF2 labels provide higher two-photon excited fluorescence yield and better assay sensitivity than corresponding TAMRA conjugate. The effect of conjugation on photophysical properties of the labels and performance of the labeled oligonucleotides in separation-free hybridization assay is discussed. 相似文献
997.
González-Mozuelos P Yeom MS Olvera de la Cruz M 《The European physical journal. E, Soft matter》2005,16(2):167-178
We study small rod-like molecular electrolytes solutions with
their corresponding atomic counterions. The asymptotic length
scales (decay length and wavelength) of the structural
correlations are analyzed using the formalism of the dressed
interaction site theory (DIST). The correlation functions are
determined using the reference interaction site model equation
complemented with a mixed approach in which the hypernetted-chain
closure is used for the repulsive interactions, and the mean
spherical approximation is used for the attractive interactions.
The results from this scheme are in good agreement with the Monte
Carlo computer simulations reported here. The asymptotic
properties of the correlation functions of this molecular system
are compared against those corresponding to two related simple
(atomic) electrolyte models. The main conclusion is that the
molecular structure of the ions lowers by two orders of magnitude
the concentration at which the transition from monotonic to
oscillatory decay occurs. 相似文献
998.
Zhao J Tian S Wang Q Liu X Jiang S Ji X An L Jiang B 《The European physical journal. E, Soft matter》2005,16(1):49-56
The surface topography of thin diblock copolymer films is studied by atomic
force microscopy (AFM). With AFM an island-to-ribbon transition is observed
for symmetric polystyrene-b-poly (4-vinylpyridine) (PS-b-P4VP) on mica with
increasing solution concentration. Our study also demonstrates how the
formation of the pattern strongly depends on the copolymer composition based
on the volume fraction. The substrate and solvent used both have great
effects on the morphology of the thin films. Only by using highly polar
substrate (mica), can we gain regular pattern. The reason why the regular
islands cannot be obtained with symmetric PS-b-P4VP on graphite is also
explained. On mica using nonselective and selective solvents, a rather
regular pattern can be obtained. The difference is only in the solution
concentration for forming regular patterns. 相似文献
999.
Experiments by Gittings, Bandyopadhyay and Durian (Europhys. Lett. 65, 414 (2004)) demonstrate that light possesses a higher probability to propagate in the liquid phase of a foam due to total
reflection. The authors term this observation photon channelling which we investigate in this article theoretically. We first
derive a central relation in the work of Gitting et al. without any free parameters. It links the photon's path-length fraction f in the liquid phase to the liquid fraction ɛ. We then construct two-dimensional Voronoi foams, replace the cell edges by
channels to represent the liquid films and simulate photon paths according to the laws of ray optics using transmission and
reflection coefficients from Fresnel's formulas. In an exact honeycomb foam, the photons show superdiffusive behavior. It
becomes diffusive as soon as disorder is introduced into the foams. The dependence of the diffusion constant on channel width
and refractive index is explained by a one-dimensional random-walk model. It contains a photon channelling state that is crucial
for the understanding of the numerical results. At the end, we shortly comment on the observation that photon channelling
only occurs in a finite range of ɛ. 相似文献
1000.
Costa AC Composto RJ Vlcek P Geoghegan M 《The European physical journal. E, Soft matter》2005,18(2):159-166
Using neutron reflectometry, the adsorption of diblock copolymers from a neutral polystyrene (PS) matrix is studied as a function
of substrate type and non-adsorbing block degree of polymerization. The block copolymer is poly(deutero styrene)-block-poly(methyl methacrylate) and the substrates are silicon oxide, SiOx, and SiOx functionalized with (3-aminopropyl)triethoxysilane (APTES). We have determined the equilibrium volume fraction-depth profiles
for such films, and compared them with volume fraction profiles generated by self-consistent mean-field (SCMF) theory and
find good agreement between the experimental and theoretical data. SCMF calculations show that the segmental interaction energy
between PS matrix chains and APTES is two orders of magnitude stronger than that between PS and SiOx. 相似文献