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21.
Jamal T. Manassah Mustafa A. Mustafa Robert R. Alfano Ping P. Po 《Physics letters. A》1985,113(5):242-247
The problem of the propagation of an intense ultrashort pulse in a cubic (χ3) nonlinear medium is generalized to include coupling between the primary and second harmonics signals. It is shown that the presence of a strong primary signal induces the superbroadening of the spectrum of a weak second harmonic signal and the deformation of its pulse shape. 相似文献
22.
Time-resolved experiments have revealed that, in contrast to the predictions of conventional diffusion theory, photons select certain curvilinear paths to travel between a source and a detector. Concepts of the average photon paths and Fermat paths are introduced on the basis of the non-Euclidean diffusion equation (NED) to explain experimental results. Comparison of the theory and the experiment demonstrates the potential of the NED to describe nondiffusive features of photon migration in the multiple-scattering regime. 相似文献
23.
A novel grating-generated scan correlation interferometry approach using a heterodyne technique for real-time signal processing is demonstrated. The characterization of reflections from a sample and detection of a femtosecond four-pulse train are presented as applications of the method. 相似文献
24.
Kilohertz Cr:forsterite regenerative amplifier 总被引:1,自引:0,他引:1
We report on a tunable regenerative amplifier that is operational in the near-infrared spectral region from 1230 to 1280 nm based on the vibronic laser material Cr:forsterite. Utilizing the technique of chirped-pulse amplification, we generated pulses as short as 150 fs at 1255 nm at a repetition rate of 1 kHz. Pulse amplification of more than 5 x 10(5) times was observed, with recorded output pulse energies of 34 muJ . Implementation of a second-harmonic generator yielded 110-fs-duration pulses of 7-muJ energy at 625 nm. 相似文献
25.
A novel method of coherence microscopy with a grating-generated delay line is demonstrated to produce depth-lateral images without axial or lateral scanning. A new image-reconstruction approach based on random phase modulation of the reference beam is realized. The depth-lateral reflections of test objects are digitally reconstructed with a simple algorithm. 相似文献
26.
Angelo J. Alfano 《国际化学动力学杂志》1996,28(7):481-487
The gas-phase pyrolysis of 3-t-butoxyquadricyclane [1] was investigated over the temperature range 511–542 K at one atm in helium. The initial pyrolysis step is the isomerization of 3-t-butoxyquadricyclane to 7-t-butoxynorbornadiene (Ea = 38.49 ± 0.85 kcal/mole, log A = 15.44 ± 0.35). 7-t-butoxynorbornadiene exhibits a single unimolecular reaction pathway which produces a mixture of t-butoxycycloheptatrienes (Ea = 38.44 ± 0.63 kcal/mole, log A = 15.05 ± 0.26). This two-step mechanism affords fewer reactions than unsubstituted quadricyclane in the gas phase and could be useful for its reduced sooting potential. © 1996 John Wiley & Sons, Inc. 相似文献
27.
Renata Monteiro-Maia Maria B Ortigão-de-Sampaio Rosa T Pinho Luiz RR Castello-Branco 《Journal of immune based therapies and vaccines》2006,4(1):1-6
We hypothesize that the energy strategy of a cell is a key factor for determining how, or if, the immune system interacts
with that cell. Cells have a limited number of metabolic states, in part, depending on the type of fuels the cell consumes.
Cellular fuels include glucose (carbohydrates), lipids (fats), and proteins. We propose that the cell's ability to switch
to, and efficiently use, fat for fuel confers immune privilege. Additionally, because uncoupling proteins are involved in
the fat burning process and reportedly in protection from free radicals, we hypothesize that uncoupling proteins play an important
role in immune privilege. Thus, changes in metabolism (caused by oxidative stresses, fuel availability, age, hormones, radiation,
or drugs) will dictate and initiate changes in immune recognition and in the nature of the immune response. This has profound
implications for controlling the symptoms of autoimmune diseases, for preventing graft rejection, and for targeting tumor
cells for destruction. 相似文献
28.
High-average-power kilohertz-repetition-rate sub-100-fs Ti:sapphire amplifier system 总被引:1,自引:0,他引:1
We report on a femtosecond Ti:sapphire laser amplifier system that generates pulse energies >5 mJ at a 1-kHz repetition rate. The system consists of regenerative and multipass amplifiers and uses the technique of chirped-pulse amplification. When the system was seeded with 70-fs pulses at 800 nm from a self-mode-locked Ti:sapphire oscillator, amplified pulses of 94-fs duration at a repetition rate of 1 kHz and an average output power of 5.4 W were produced. The amplified pulse-repetition rate is variable from 250 Hz to 3 kHz. Pulse energies of >7.5 mJ were obtained at 500 and 250 Hz. 相似文献
29.
30.
Malignant, fibroadenoma, normal and adipose breast tissues were studied using diffuse reflectance spectroscopy. The absorption spectra of the breast tissues were extracted from the diffuse reflectance spectra using the Kubelka-Munk function (K-M function). The spectral features of the K-M function were identified and compared with those of the absorption spectra. The spectral features of the K-M function were assigned to DNA, protein, beta-carotene and hemoglobin (oxygenated and deoxygenated) molecules in the breast tissue. The amplitudes of the K-M function averaged from 275 to 285 nm and from 255 to 265 nm and were found to be different for malignant, fibroadenoma and normal tissues. These differences were attributed to changes in proteins and DNA. A set of critical parameters was determined for separating malignant tissues from fibroadenoma and normal tissues. This approach should hold for other tissue types such as cervix, uterus and colon. 相似文献