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931.
Le Bizec B Gaudin I Monteau F Andre F Impens S De Wasch K De Brabander H 《Rapid communications in mass spectrometry : RCM》2000,14(12):1058-1065
For the first time in the field of steroid residues in humans, demonstration of 19-norandrosterone (19-NA: 3alpha-hydroxy-5alpha-estran-17-one) and 19-noretiocholanolone (19-NE: 3alpha-hydroxy-5beta-estran-17-one) excretion in urine subsequent to boar consumption is reported. Three male volunteers agreed to consume 310 g of tissues from the edible parts (meat, liver, heart and kidney) of a boar. The three individuals delivered urine samples before and during 24 h after meal intake. After deconjugation of phase II metabolites, purification and specific derivatisation of target metabolites, the urinary extracts were analysed by mass spectrometry. Identification was carried out using measurements obtained by gas chromatography/high resolution mass spectrometry (GC/HRMS) (R = 7000) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) (positive electrospray ionisation (ESI+)). Quantification was realised using a quadrupole mass filter. 19-NA and 19-NE concentrations in urine reached 3.1 to 7.5 microg/L nearby 10 hours after boar tissue consumption. Levels returned to endogenous values 24 hours after. These two steroids are usually exploited to confirm the exogenous administration of 19-nortestosterone (19-NT: 17beta-hydroxyestr-4-en-3-one), especially in the antidoping field. We have thus proved that eating tissues of non-castrated male pork (in which 17beta-nandrolone is present) might induce some false accusations of the abuse of nandrolone in antidoping. 相似文献
932.
A major concern raised about photostability studies of sunscreen products is that the photodegradation of sunscreens does not readily translate into changes in product performance. This study examines the correlation between photochemical degradation of sunscreen agents and changes in protection provided by sunscreen films. Films of a commercial sunscreen product containing avobenzone, oxybenzone and octinoxate were irradiated using a fluorescent UV-A phototherapy lamp with additional UV-B blocking filter. Periodically, during irradiation the transmittances of the films were measured and samples collected for chemical analysis of the sunscreen agents using high-performance liquid chromatography techniques. The results show that UV-induced changes in UV transmittance of sunscreen films correlate with changes in concentration of sunscreen agents. In a parallel experiment, we also irradiated a thin film of the same product in the cavity of an electron spin resonance (ESR) spectrometer. We report the concomitant photolysis of avobenzone and octinoxate that predominates over expected E/Z photoisomerization and that irradiation of a film of this product produced free radicals detected by ESR spectroscopy that persisted even after exposure had ended. 相似文献
933.
Humberto César Chaves Fernandes 《International Journal of Infrared and Millimeter Waves》1996,17(8):1419-1430
The theory and numerical results of the asymmetric single and coupled bilateral and unilateral finlines and arbitrary antipodal finline considering the attenuation of the substrate are presented. Results are given to the complex propagation constant. The full wave analysis of the Transverse Transmission Line — TTL method is used in the FTD. Applying the moment method the complex propagation constant, including the attenuation constant and the phase constant, are obtained. The effective dielectric constant, eff,, and the characteristic impedance are also calculated. The results are compared with the references, and news results are presented for these parameters. 相似文献
934.
The dependence of solution behavior to perturbations of the initial function (IF) in a class of nonlinear differential delay equations (DDEs) is investigated. The structure of basins of attraction of multistable limit cycles is investigated. These basins can possess complex structure at all scales measurable numerically although this is not necessarily the case. Sensitive dependence of the asymptotic solution to perturbations in the initial function is also observed experimentally using a task specific electronic analog computer designed to investigate the dynamics of an integrable first-order DDE. 相似文献
935.
J. D'Ans K. Wagenmann Richard Berg K. R. Andreß G. Rienäcker J. Heyrovskv G. Mann K. Wüst G. Hesse M. Haitinger A. Winkel H. Siebert A. A. Benedetti-Pichler H. Lieb F. Löwe W. Meidinger Verein Deutscher Ingenieure W. Matz E. Wicke Hermann Mayer 《Analytical and bioanalytical chemistry》1939,117(3-4):157-158
936.
L. Harivardhan Reddy Humberto Ferreira Catherine Dubernet Sinda Lepetre Mouelhi Didier Desmaële Bernard Rousseau Patrick Couvreur 《Journal of nanoparticle research》2008,10(5):887-891
Recently, we had discovered that the linkage of nucleoside analogues to squalene, a precursor in the sterol biosynthesis,
led to amphiphilic molecules, which self-organized in water as nanoassemblies of 100–300 nm in diameter, irrespective of the
nucleoside analogue used. Thus, it was observed that the 4-(N)-trisnorsqualenoylgemcitabine (SQdFdC), the squalenoyl prodrug of the anticancer nucleoside analogue gemcitabine, was impressively
more active than its parent compound gemcitabine, both in vitro and in vivo on experimental leukaemia. Since squalene, which
is a natural constituent of shark liver and olive oil, is known to be absorbed orally, we investigated in this short note
the absorption and tissue distribution of 3H-radiolabelled SQdFdC nanoassemblies comparatively to 3H-gemcitabine after oral administration to mice. Whereas gemcitabine was found to be rapidly absorbed (t
max = 1 h), this compound underwent a rapid clearance from the plasma. Conversely, the SQdFdC nanoassemblies displayed slower
absorption followed by the progressive tissue accumulation, and they exhibited a lower clearance rate. The accumulation of
the SQdFdC nanoassemblies in tissues such as pancreas, thymus, lung, liver and spleen (except at 1 h post-administration)
was similar to that of the gemcitabine, yet exhibited significantly greater penetration and retention into the stomach and
intestinal tissues comparatively to gemcitabine. Thus, the SQdFdC nanoassemblies could be of potential interest in the treatment
of gastrointestinal tumours by oral route. 相似文献
937.
938.
939.
Humberto Prado 《Semigroup Forum》2008,77(3):456-462
We study stability properties of certain evolution equations including the fractional Cauchy problem. Under some spectral
assumptions these equations are governed either by a resolvent or a regularized resolvent or a k-convoluted semigroup. We investigate the long time behavior for bounded solutions by a direct application of the ergodic
theorems for regularized resolvents of Lizama and Prado (J. Approx. Theory 122:42–61, 2003), Prado (Semigroup Forum 73:243–252, 2006). We apply our results to the qualitative study of the fractional diffusion-wave equation on L
p
(ℝ).
The author is partially supported under FONDECYT Grant no 1070127. 相似文献
940.
Ma. Eulalia Vanegas Raúl Quijada Daniel Serafini Griselda B. Galland Humberto Palza 《Journal of Polymer Science.Polymer Physics》2008,46(8):798-806
Syndiotactic polypropylenes and their copolymers with 1‐olefins were synthesized using two metallocene/MAO catalytic systems, and the effect of the different microstructures on nonisothermal crystallization and subsequent melting was studied. Using differential scanning calorimetry (DSC) it was observed that samples with lower content of defects showed crystallization on cooling from the melt, and a double melting peak in the subsequent heating scan, the latter associated with melt, recrystallization and remelt processes that it was confirmed by its nonreversing exothermic process found by means of temperature modulated DSC (MDSC). However, polymers with high amount of defects showed cold crystallization on heating followed by a melting process, that it was observed by MDSC. Wide angle X‐ray diffraction was used for characterizing the changes of crystalline forms in relationship with crystallization process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 798–806, 2008 相似文献