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31.
P. J. Ruback 《Communications in Mathematical Physics》1986,107(1):93-102
A scheme is proposed and justified for examining the motion of the five dimensional Kaluza-Klein monopoles at low energy. The classical and quantum scattering is discussed and it is shown that for all separations and at small velocities the monopoles do not interact with one another. 相似文献
32.
33.
E. Garde S. Mici K. Knudsen H. R. Angelo H. C. Wulf 《Photochemistry and photobiology》1994,60(5):475-480
Abstract It is well established that in healthy humans oral intake of 5-or 8-methoxypsoralen (5-and 8-MOP) is followed by a significant increase in plasma melatonin concentrations. The effect of psoralen on rat melatonin has been studied in vitro and in vivo and a stimulation of release or secretion from the pineal gland has been suggested. In this study we examined the time-related changes in plasma concentrations of 8-MOP, melatonin and 6-sulfatoxymelatonin in 15 patients admitted for routine psoralen plus UVA therapy. On the first day of treatment blood samples were collected before, and 30, 60 , 66 and 90 rnin after intake of 8-MOP (0.6 mg/kg). Although the rate of 8-MOP absorption vaned greatly, a significant increase ( P = 0.0002) in melatonin levels was found 60 min after 8-MOP intake. During UVA exposure a strongly correlated decrease in mean melatonin and mean 8-MOP concentrations was found, indicating an effect of UVA radiation, either direct or 8-MOP mediated, on circulating melatonin levels. Plasma 6-sulfatoxymelatonin concentrations decreased significantly between all time points, suggesting inhibition of melatonin metabolism. 相似文献
34.
The primary charge separation in photosystem (PS) I was measured on stacked pea thylakoids using the light-gradient photovoltage technique. Upon 532 nm excitation with picosecond flashes, a trapping time of 80 ± 10 ps for PS I was found, which is in close agreement with literature data. In the wavelength range between 700 nm and 717 nm the trapping time was essentially the same although there was an indication for a slight decrease. To further analyze the data we performed a spectral decomposition of PS I with Chi a and b solvent spectra. This procedure yielded bands at around 682 nm, 690 nm, 705 nm and 715 nm. According to this decomposition, a selective excitation of long-wavelength antenna pigments at wavelengths Λ > 710 nm is possible, because the direct excitation of the main 682 nm band is small compared to the excitation of the two most red-shifted bands. The invariability of the trapping time of the excitation wavelength suggests thermal equilibration of the excitation energy among all antenna pigments according to their excited state energy levels and their abundance. Hence, we conclude that trapping in PS I is essentially rate-limited by the primary charge separation much as it is the case in PS II. Then, according to our spectral decomposition in a time constant of2–3 ps is predicted for the primary charge separation in PS I. 相似文献
35.
We study the structure and dynamics of hydrogen-bonded complexes of H2O/D2O and dimethyl sulfoxide (DMSO) by infrared spectroscopy, NMR spectroscopy and ab initio calculations. We find that single water molecules occur in two configurations. For one half of the water monomers both OH/OD groups form strong hydrogen bonds to DMSO molecules, whereas for the other half only one of the two OH/OD groups is hydrogen-bonded to a solvent molecule. The H-bond strength between water and DMSO is in the order of that in bulk water. NMR deuteron relaxation rates and calculated deuteron quadrupole coupling constants yield rotational correlation times of water. The molecular reorientation of water monomers in DMSO is two-and-a-half times slower than in bulk water. This result can be explained by local structure behavior. 相似文献
36.
37.
Distinctive Molecular Abnormalities in Benign and Malignant Skin Lesions: Studies by Raman Spectroscopy 总被引:6,自引:0,他引:6
Monika Gniadecka Hans C. Wulf Ole F. Nielsen Daniel H. Christensen Jana Hercogova 《Photochemistry and photobiology》1997,66(4):418-423
Abstract— Near-infrared Fourier transform Raman spectroscopy is an analytical, nondestructive technique that provides information about the molecular structure of the investigated sample. The molecular structure of proteins and lipids differs between neoplastic and normal tissues and therefore Raman spectroscopy has been considered promising for the diagnosis of cancer. We aimed to compare the molecular structure of normal skin, benign and malignant skin lesions by the near-infrared Fourier transform Raman spectroscopy. Biopsies were obtained from the following skin lesions: skin tag, dermatofibroma, seborrhoeic keratosis, actinic keratosis, keratoacan-thoma, basal cell carcinoma, squamous cell carcinoma, nevus intradermal, nevus compositus, dysplastic nevus and lentigo maligna. Control skin was harvested from the vicinity of these lesions. In the Raman spectra, the secondary structure of the proteins was reflected by the amide vibrations of peptide bonds. The principal lipid vibrations were twisting and wagging (CH2 ) and CH stretching vibrations. Histologically distinguishable lesions showed specific combinations of band changes indicating alterations in the protein conformation and in the molecular structure of the lipids. Histogenetically related lesions (actinic keratosis and sqamous cell carcinoma) produced similar but not identical patterns of spectral changes. Because the examined skin lesions produced reproducible and unique spectra, we suggest that Raman spectroscopy will be useful for diagnosis of skin lesions. 相似文献
38.
Validation and application of an LC-MS/MS method for the simultaneous quantification of 13 pharmaceuticals in seawater 总被引:2,自引:0,他引:2
Klaas Wille Herlinde Noppe Karolien Verheyden Julie Vanden Bussche Eric De Wulf Peter Van Caeter Colin R. Janssen Hubert F. De Brabander Lynn Vanhaecke 《Analytical and bioanalytical chemistry》2010,397(5):1797-1808
Knowledge of the presence of micropollutants such as pharmaceuticals, in coastal areas, is very limited; therefore, the main
objective of this study was to optimize and validate a new analytical method for the quantitative analysis of 13 multiclass
pharmaceuticals in seawater. Target compounds included antibiotics, non-steroidal anti-inflammatory drugs, β-blockers, lipid
regulators and one psychiatric drug. A combination of solid-phase extraction and liquid chromatography coupled with multiple
mass spectrometry enabled their detection at the low nanogram per litre level. The limits of quantification varied between
1 and 50 ng L-1, for most components the linearities were more than 0.99 and the recoveries obtained in seawater (95–108%) were satisfactory.
This method was applied to seawater and estuarine water samples collected in the Belgian coastal zone, to assess the prevalence
of common pharmaceuticals in this marine environment. Seven pharmaceuticals, including compounds of which the presence in
marine environments had not been reported earlier, were detected, with salicylic acid and carbamazepine being the most abundant,
in concentrations up to 855 ng L-1. 相似文献
39.
Krivovichev SV Siidra OI Nazarchuk EV Burns PC Depmeier W 《Inorganic chemistry》2006,45(10):3846-3848
Dark-green platy crystals of the new compound Pb31O22Br10Cl8 (1) have been obtained by rapid quenching of a lead oxide halide melt. The structure of 1 (triclinic, P1, a = 12.1192(7) angstroms, b = 16.2489(10) angstroms, c = 18.3007(11) angstroms, alpha = 93.104(2) degrees, beta = 95.809(2) degrees, gamma = 111.252(1) degrees, V = 3325.4(3) angstroms3, Z = 2) can be viewed as incorporation of [PbX6]4- halide units (X = Br, Cl) into the defect PbO matrix. The latter represents a two-dimensional [O22Pb30]16+ cationic layer of OPb4 tetrahedra that can be derived from the [OPb] tetrahedral layer observed in tetragonal PbO. The layer consists of 22 symmetrically inequivalent OPb4 tetrahedra and represents the topologically most complicated arrangement of tetrahedra known to date. 相似文献
40.
The PUR-fiber-spray molding technology is a manufacturing process which produces polyurethane-based (PUR) composites by spraying the matrix together with reinforcing fibers in a tool form or on a substrate. Thereby chopped fibers are laterally (sidewise) injected in the polyurethane-air spray cone for wetting before the entire composite is spread on the substrate, where it starts curing. To investigate and compute the fiber orientation and density distribution in the final composites manufactured by this process, a new approach simplifying the multiply coupled interaction of the three phases is presented in this paper. Hereby it is presumed that the final position and orientation of a fiber on a substrate results from its dynamics and coupled interactions with air, PUR-droplets and other fibers within the spray cone. Thus, a model of the process is built, that computes the transient behavior of the air-liquid droplets mixture by the CFD code ANSYS Fluent and its influence on the dynamics of the fibers by an extra code called FIDYST. For this multiphase problem two approaches are presented for the droplet-fiber coupling using a concept called “homogenization” of the liquid phase (droplets in the continuous phase). (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献