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61.
The complete structure of the 1:1 adduct between guanosine and glycidaldehyde has been unequivocally determined by high-field NMR data and by synthesis of related model compounds. 相似文献
62.
Nanofluids are a new class of heat transfer fluids developed by suspending nanosized solid particles in liquids. Larger thermal
conductivity of solid particles compared to the base fluid such as water, ethylene glycol, engine oil etc. significantly enhances
their thermal properties. Several phenomenological models have been proposed to explain the anomalous heat transfer enhancement
in nanofluids. This paper presents a systematic literature survey to exploit the characteristics of nanofluids, viz., thermal
conductivity, specific heat and other thermal properties. An empirical correlation for the thermal conductivity of Al2O3 + water and Cu + water nanofluids, considering the effects of temperature, volume fraction and size of the nanoparticle is
developed and presented. A correlation for the evaluation of Nusselt number is also developed and presented and compared in
graphical form. This enhanced thermophysical and heat transfer characteristics make fluids embedded with nanomaterials as
excellent candidates for future applications.
相似文献
63.
In vitro produced bovine embryos were frozen by pellet freezing or vitrification method. In the pellet freezing method, the embryos were cooled on the dry ice and then frozen as pellets. At warming, the pellets were immersed directly into 0.5 M sucrose. The survival rates of blastocysts frozen by the pellet freezing method were higher (P<0.01) in 40% ethylene glycol (EG) than those in the lower concentrations (20 and 30% EG). Higher survival rates of blastocysts frozen by the pellet freezing method were obtained but the development rates did not differ, as compared with those by the vitrification method. There were no significant differences between the pellet freezing and vitrification method in the frequencies of post-thaw survival of hatched blastocysts. These results demonstrate that the pellet freezing method using dry ice can be used successfully for the cryopreservation of blastocysts. 相似文献
64.
Timothy M. Crowder Vasu Sethuraman Thomas B. Fields Anthony J. Hickey 《Particle & Particle Systems Characterization》1999,16(4):191-196
Previous studies of the flow of granular materials in a rotating drum have described the observed time sequences of angle of repose or time to avalanche. The time between avalanches approach has been incorporated into a commercially available powder flow analysis tool. In the present study, the time to avalanche analysis was complemented with a Fourier Transform power spectrum and phase space analysis of the angle of repose time series and avalanche size variability determination. The avalanche size variability approach was found to most readily differentiate between the flow properties of powders across material types. A model was constructed to provide an explanation for the utility of this method. 相似文献
65.
The use of driver inserts to reduce non-ideal pressure variations behind reflected shock waves 总被引:1,自引:1,他引:0
Zekai Hong Genny A. Pang Subith S. Vasu David F. Davidson Ronald K. Hanson 《Shock Waves》2009,19(2):113-123
Non-ideal shock tube facility effects, such as incident shock wave attenuation, can cause variations in the pressure histories
seen in reflected shock wave experiments. These variations can be reduced, and in some cases eliminated, by the use of driver
inserts. Driver inserts, when designed properly, act as sources of expansion waves which can counteract or compensate for
gradual increases in reflected shock pressure profiles. An algorithm for the design of these inserts is provided, and example
pressure measurements are presented that demonstrate the success of this approach. When these driver inserts are employed,
near- ideal, constant-volume performance in reflected shock wave experiments can be achieved, even at long test times. This
near-ideal behavior simplifies the interpretation of shock tube chemical kinetics experiments, particularly in experiments
which are highly sensitive to temperature and pressure changes, such as measurements of ignition delay time of exothermic
reactions. 相似文献
66.
Polarization effects on population transfer by stimulated Raman transition using overlapping time dependent pump and Stokes
laser pulses from the ground X
1Σ
g
/+
(v
g=0, J
g=1) level of H2 to the final X
1Σ
g
/+
(v
f=1, J
f=1) level via the intermediate B
1Σ
u
/+
(v
i=14, J
i=0,2), C
1Π
u
/+
(v
i=3, J
i=2) and C
1Π
u
/−
(v
i=3, J
i=1) levels have been theoretically investigated by applying the density matrix formalism. We have studied in detail the dependence
of the population transfer on time delay between two pulses for the cases of on-resonance excitations considering linear parallel
and same-sense circular polarizations of the fields. The pump and Stokes fields are taken as having Gaussian pulse shapes
with peak intensities I
P
/0
(I
S
/0
)=2 × 106 and 1 × 107 W/cm2. Density matrix equations have been solved for each value of the magnetic quantum number M
g(0, ±1) of the initial ground level taking into account the M
g dependence of the Rabi frequencies. M
g — averaged population transfer to the final level has also been calculated. For resonance excitations to the B(14, 0) or C(3, 1) levels, appreciable population transfer is achieved for intuitive pulse order for some particular values of M
g and M
i (magnetic quantum number of the resonant intermediate level) depending on the nature of polarizations. The calculated values
of M
g — averaged population transfer for the two cases of polarizations show that for on-resonance excitation to the B(14, 0) or the C(3, 1) level, linear parallel polarization of the laser fields yield more transfer efficiency whereas for resonance excitation
to the B(14, 2) level, larger population transfer results from the same-sense circular polarizations. For resonance excitation to
the C(3, 2) level, M
g — averaged population is found to be almost polarization independent. The calculations for the six-level H2 system reveal some interesting features of polarization effects on the population transfer efficiency. 相似文献
67.
Dale C. Swenson Vasu Nair Sanjib Bera 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):e600-e601
We have synthesized a dideoxydidehydronucleoside derivative, 2(S)‐acetoxymethyl‐4‐[4‐amino‐2‐oxopyrimidin‐1(2H)‐yl]‐2,5‐dihydrofuran, C11H13N3O4, which is an analogue of the potently anti‐HIV active compound, dideoxy‐didehydrocytidine (d4C). The target compound crystallizes with two molecules in the asymmetric unit that differ primarily in the orientation of the C6′‐acetyl group. One molecule has an extended conformation and the orientation of the acetyl group in the second molecule gives an unusual hooked‐shaped conformation. The two conformers form A–B dimers via N—H?N hydrogen bonds. The dimers link via N—H?O hydrogen bonds to form chains parallel to the b cell axis. 相似文献
68.
69.
N. Hyvönen A. K. Nandakumaran H. M. Varma R. M. Vasu 《Mathematical Methods in the Applied Sciences》2013,36(11):1447-1458
We propose a novel numerical method based on a generalized eigenvalue decomposition for solving the diffusion equation governing the correlation diffusion of photons in turbid media. Medical imaging modalities such as diffuse correlation tomography and ultrasound‐modulated optical tomography have the (elliptic) diffusion equation parameterized by a time variable as the forward model. Hitherto, for the computation of the correlation function, the diffusion equation is solved repeatedly over the time parameter. We show that the use of a certain time‐independent generalized eigenfunction basis results in the decoupling of the spatial and time dependence of the correlation function, thus allowing greater computational efficiency in arriving at the forward solution. Besides presenting the mathematical analysis of the generalized eigenvalue problem on the basis of spectral theory, we put forth the numerical results that compare the proposed numerical method with the standard technique for solving the diffusion equation. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
70.
In this paper, we establish several inequalities for some differantiable mappings that are connected with the Riemann-Liouville fractional integrals. The analysis used in the proofs is fairly elementar... 相似文献