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1.
We report on the optimization of high-intensity absorption imaging for small Bose–Einstein condensates. The imaging calibration exploits the linear scaling of the quantum projection noise with the mean number of atoms for a coherent spin state. After optimization for atomic clouds containing up to 300 atoms, we find an atom number resolution of $\varDelta_{\rm det}= 3.7$ atoms, mainly limited by photon shot noise and radiation pressure.  相似文献   
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Linear parameter varying (LPV) control is a model-based control technique that takes into account time-varying parameters of the plant. In the case of rotating systems supported by lubricated bearings, the dynamic characteristics of the bearings change in time as a function of the rotating speed. Hence, LPV control can tackle the problem of run-up and run-down operational conditions when dynamic characteristics of the rotating system change significantly in time due to the bearings and high vibration levels occur. In this work, the LPV control design for a flexible shaft supported by plain journal bearings is presented. The model used in the LPV control design is updated from unbalance response experimental results and dynamic coefficients for the entire range of rotating speeds are obtained by numerical optimization. Experimental implementation of the designed LPV control resulted in strong reduction of vibration amplitudes when crossing the critical speed, without affecting system behavior in sub- or super-critical speeds.  相似文献   
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The decay of140Pr was investigated by means of a Ge(Li) spectrometer. Excited states of140Ce at 1,596.2, 1,903.1, 2,348.9, 2,522.5, 3,016.8 and 3,119.6 keV are fed in the beta decay of140Pr. Spin and parity assignments for all observed levels have been made from electron capture and positon disintegration considerations and gamma branches. The experimental level scheme of140Ce is compared with the results of shell model calculations forN=82 nuclei.  相似文献   
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The beta decay of143Sm was reinvestigated with the aid of a Ge(Li) detector. Levels of143Pm at 271.8, 1,056.5, 1,173.4, 1,342.1, 1,403.2, 1,514.9, 1,752.8, 1,816.3, 1,853.6, (2,000), 2,009.0, 2,080.5, 2,344, 2,443, 2,463, 2,906 and (3,054) keV were established. Logft values for all observed beta transitions have been calculated. Spin and parity assignments have been made from electron capture and positon disintegration considerations and gamma branches. The experimental level scheme of143Pm is compared with the results of 1 and 3 q.p. calculations forN=82 nuclei.  相似文献   
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The magnetic susceptibility, using dc and electron spin resonance (ESR) methods, the specific heat, and the infrared properties of the one-dimensional molecular semiconductors lithium phthalocyanine (LiPc) and the iodinated compound LiPcI have been investigated for temperatures K. LiPc has a half-filled conduction band and is expected to be an organic metal. However, due to the strong Coulomb repulsion the system is a one-dimensional Mott-Hubbard insulator with a Hubbard gap of 0.75 eV as inferred from optical measurements. The localized electrons along the molecular stacks behave like a S = 1/2 antiferromagnetic spin chain. The spin susceptibility, as determined by ESR experiments, and the magnetic contribution to the heat capacity show a Bonner-Fisher type of behavior with an exchange constant K. LiPcI is an intrinsic narrow-gap semiconductor with an optical gap of 0.43 eV. In ESR experiments it is silent, indicating that all the unpaired electrons have been removed from the macrocycle via doping with iodine. Received: 16 June 1998 / Accepted: 14 July 1998  相似文献   
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We present susceptibility, microwave resistivity, NMR and heat-capacity results for Li1-xZnx(V1-yTiy)2O4 with 0 ? x ? 0.3 and 0 ? y ? 0.3. For all doping levels the susceptibility curves can be fitted with a Curie-Weiss law. The paramagnetic Curie-Weiss temperatures remain negative with an average value close to that of the pure compound Θ≈ - 36 K. Spin-glass anomalies are observed in the susceptibility, heat-capacity and NMR measurements for both type of dopants. From the temperature dependence of the spin-lattice relaxation rate we found critical-dynamic behavior in the Zn doped compounds at the freezing temperatures. For the Ti-doped samples two successive freezing transitions into disordered low-temperature states can be detected. The temperature dependence of the heat capacity for Zn-doped compounds does not resemble that of canonical spin glasses and only a small fraction of the total vanadium entropy is frozen at the spin-glass transitions. For pure LiV2O4 the spin-glass transition is completely suppressed. The temperature dependence of the heat capacity for LiV2O4 can be described using a nuclear Schottky contribution and the non-Fermi liquid model, appropriate for a system close to a spin-glass quantum critical point. Finally an ( x / y , T )-phase diagram for the low-doping regime is presented. Received 16 March 2001 and Received in final form 30 October 2001  相似文献   
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The 102Mo activity was obtained by photofission of natural U and thermal-neutron induced fission of 235U, with subsequent chemical separation of the molybdenum fraction. In addition, nuclei with mass 102 were separated from fission products of 235U(nth, f) using the mass separator LOHENGRIN. A decay scheme and absolute γ-intensities are deduced from measured γ-ray, X-ray and γ-coincidence spectra. Logftvalues are calculated. Shell-model calculations for a (πlg92)3(νlg72)3 multiplet have been carried out using effective nucleon-nucleon interactions. The γ-decay between low-lying, low-spin members of this multiplet was studied in detail and compared with the experimental data.  相似文献   
10.
We report on the experimental demonstration of the internal bosonic Josephson effect in a rubidium spinor Bose-Einstein condensate. The measurement of the full time dynamics in phase space allows the characterization of the theoretically predicted π-phase modes and quantitatively confirms analytical predictions, revealing a classical bifurcation. Our results suggest that this system is a model system which can be tuned from classical to the quantum regime and thus is an important step towards the experimental investigation of entanglement generation close to critical points.  相似文献   
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