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排序方式: 共有78条查询结果,搜索用时 46 毫秒
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Lifetime of levels up to 22+, have been measured in 78Kr and an oblate shape is assigned to the ground state using the CSM and the configuration dependent shell correction calculations.
Calculations further show that 78Kr is highly γ-soft nucleus. The experimental Q
t values coupled with theoretical calculations indicate an oblate shape for 78Kr at low spins and triaxial shape at higher spins 相似文献
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Stable isotope methods are potentially quite useful for validating natural or enhanced mineral degradation of contaminants. For this reason, a continuous flow gas chromatograph (GC), isotope ratio mass spectrometer (IRMS) has been coupled with a quadrupole mass selective detector (MSD) to allow simultaneous mass spectral and stable carbon isotope ratio data to be obtained from a single chromatographic analysis. This allows the target contaminant and any extra-cellular degradation intermediates to be both qualified and quantified. Previously acceptable limits of precision (0.3 parts per mil) are undesirable given the small fractionation observed during aerobic degradation. To further understand the fate of organic contaminants and to gain information about the metabolic degradative pathway employed by a microorganism, routine isotopic analyses on a range of analytes have been performed. Quantities of sample producing mass-44 ion beam signal (I(44)) of 2 x 10(-10) to 1 x 10(-8) A were analysed. When the IRMS was tuned for high sensitivity, ion source nonlinearities were overcome by peak height correction from an algorithm that was produced using known isotopic standards of varying concentrations. This led to sample accuracy of <0.01 per thousand and sample precision of 0.1 per thousand. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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KM Clauwaert Van Bocxlaer JF HJ Major JA Claereboudt WE Lambert Van den Eeckhout EM Van Peteghem CH De Leenheer AP 《Rapid communications in mass spectrometry : RCM》1999,13(14):1540-1545
This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
28.
Lifetimes of high spin states up to {
}=22+ in the yrast positive parity bands have been measured to investigate the shape evolution with increasing spin in 72, 74Se. The Q
t values derived from these measurements indicate that prolate shape stabilizes for 72Se, while a triaxial shape develops for 74Se at higher spins. Comparison of the observed trend in Q
t with spin for 72, 74Se with that of the corresponding kryptones isotones emphasizes the stability provided by N=38 prolate shell gap even at high rotational frequency. 相似文献
29.
Tumour‐Targeted Drug Delivery with Mannose‐Functionalized Nanoparticles Self‐Assembled from Amphiphilic β‐Cyclodextrins
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Zhou Ye Dr. Quan Zhang Shengtao Wang Priya Bharate Silvia Varela‐Aramburu Prof. Mengji Lu Prof. Peter H. Seeberger Prof. Jian Yin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(43):15216-15221
Multivalent mannose‐functionalized nanoparticles self‐assembled from amphiphilic β‐cyclodextrins (β‐CDs) facilitate the targeted delivery of anticancer drugs to specific cancer cells. Doxorubicin (DOX)‐loaded nanoparticles equipped with multivalent mannose target units were efficiently taken up via receptor‐mediated endocytosis by MDA‐MB‐231 breast cancer cells that overexpress the mannose receptor. Upon entering the cell, the intracellular pH causes the release of DOX, which triggers apoptosis. Targeting by multivalent mannose significantly improved the capability of DOX‐loaded nanoparticles to inhibit the growth of MDA‐MB‐231 cancer cells with minimal side effects in vivo. This targeted and controlled drug delivery system holds promise as a nanotherapeutic for cancer treatment. 相似文献
30.
M. Quilichini J.M. Perez-Mato I. Aramburu O. Hernandez 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(4):431-438
Three-axes elastic neutron scattering measurements demonstrate that the five-fold modulated phase (phase 1/5) of BCCD exhibits
under electric field a phase transition without change of superlattice periodicity. Through the monitoring of high-order satellite
diffraction peaks as a function of electric field and temperature, the competition between this phase and neighboring polar
phases with other periods has been characterized. At a threshold electric field of about 20 kV/cm, a rather abrupt redistribution
of the satellite intensities of phase 1/5 is observed, without change of the corresponding primary modulation wave vector
( ⅕). A quantitative analysis of these intensity variations confirms the earlier conjecture based on dielectric experiments that
the modulation essentially changes from a non-polar sequence 5up5down ( <5>) of polarized z-perpendicular layers of basic semicells, to a polar sequence 6up4down ( <64>). The transition is caused by the flip of the average polarization of one of the interface layers, and can then be described as a bounded discrete motion of the
wall separating positive and negative microdomains within the five-fold unit cell. This type of polarization-flip phase transition
had been detected and characterized in one-dimensional theoretical models as generalized Frenkel-Kontorova models or spin
chains with elastic couplings, but had not been anticipated in theoretical analyses of BCCD, for which other phenomenological
or microscopic models (as the ANNNI model) have been considered adequate. Only recently and in view of the experimental results
reported here, we demonstrated, using a general phenomenological displacive model, the possibility of this type of transition
in systems as BCCD [Phys. Rev. B 62, 11418 (2000)]. Phase diagrams with spin-flip phase transitions yield very peculiar phase diagrams with a checkerboard topological
structure and self-similar features. In particular, they may present special critical points as the so-called upsilon points [J. Statistical Phys. 62, 45 (1991)]. BCCD may be then the first experimental system where they could be observed.
Received 20 September 2001 相似文献