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21.
《Spectrochimica Acta Part B: Atomic Spectroscopy》1995,50(13):1717-1724
Magnesium content is an important diagnostic parameter in medicine. It is recognized that its determination in one compartment is not sufficient for reliable information about the magnesium status in the body. In addition to the common procedures of magnesium determination in blood by flame atomic absorption spectrometry, the procedure of electrothermal atomization has also been developed and applied to the analysis of blood fractions, mononuclear cells and isolated nuclei of liver cells.Electrothermal atomization is preferred in cases where the sample size is limited and the magnesium content low. The total errors are in the order of 3–4%. Various techniques of sample pretreatment have been tested and direct dilution with 0.05 mol l−1 nitric acid was optimal when the samples were not mineralized. The calibration graph based on standards containing albumin was found to give the best results, as the form of magnesium in the samples may influence the ashing and atomization processes. Good agreement was obtained for determination of magnesium in standard serum. The results are compared with those obtained by the standard flame atomization technique. 相似文献
22.
L.C. Alves M.G.S. Cavalcanti H.R.C. Araújo G.M. Silva D.L. Veras M.H.S. Paiva F.A. Brayner 《Micron (Oxford, England : 1993)》2009,40(5-6):659-664
Single dose of diethylcarbamazine (DEC) used in control programs is effective in breaking the transmission of filariasis. In order to investigate the effect of aggressive therapy on Wuchereria bancrofti (Wb) microfilariae, DEC was given to 29 patients who were positive for the circulating filarial antigen (CFA) assay but did not have clinical manifestations of filariasis, at 6 mg/kg/day for 12 days and again six months later using the same dosing regimen. For each patient, microfilarial density and serum CFA were followed up for two years. Ultrastructural analyses on Wb microfilariae obtained after repeated treatment with DEC were also performed. Microfilaremia and antigenemia decreased significantly after 12 months but returned to the initial levels after 24 months. This could indicate, as shown by other authors, that aggressive repeated therapy with DEC alone is ineffective in eradicating adult W. bancrofti, particularly in infected but asymptomatic individuals. The objective of the present study was to analyze the microfilaremic and antigenemic behavior and ultrastructural changes caused by different DEC concentrations in vitro in Wb microfilariae obtained from individuals who were sensitive and refractory to treatment. After in vitro treatment of the microfilariae using 5 and 10 μg/ml of DEC for 1 h, ultrastructural analysis revealed low levels of cell damage compared with embryos obtained from individuals from a different area who had never received DEC treatment before. The results obtained suggest that microfilariae from patients who receive repeated aggressive therapy are less sensitive to DEC in vitro. 相似文献
23.
《Nuclear Physics B》2001,609(3):499-517
We analyze the propagation of a scalar field in multidimensional theories which include kinetic corrections in the brane, as a prototype for gravitational interactions in a four-dimensional brane located in a (nearly) flat extra-dimensional bulk. We regularize the theory by introducing an infrared cutoff given by the size of the extra dimensions, R, and a physical ultraviolet cutoff of the order of the fundamental Planck scale in the higher-dimensional theory, M. We show that, having implemented cutoffs, the radius of the extra dimensions cannot be arbitrarily large for M≳1 TeV. Moreover, for finite radii, the gravitational effects localized on the brane can substantially alter the phenomenology of collider and/or table-top gravitational experiments. This phenomenology is dictated by the presence of a massless graviton, with standard couplings to the matter fields, and a massive graviton which couples to matter in a much stronger way. While graviton KK modes lighter than the massive graviton couple to matter in a standard way, the couplings to matter of the heavier KK modes are strongly suppressed. 相似文献
24.
The paper is connected with the determination of␣temperature field in a periodically layered half-space caused by a laser
heating. Two types of thermal loadings distributed on a boundary of the body is considered: uniform and normal (Gaussian).
The influence of geometrical and thermal parameters of the layered composite on the temperature field is analyzed.
Received on 27 November 1997 相似文献
25.
The crystal and molecular structure of 2-carboxy-2-methoxybiphenyl has been determined to R=0.035. Crystals are tetragonal, of space group I41cd, witha=b=15.181(2)c=19.874(2) Å. Mean esd values for bond lengths and bond angles are 0.005 Å and 0.3°, respectively. The angle between phenyl rings is 54.5(1)°. The C(1) (carboxy) and O (methoxy) distance is 3.02 Å. Dimers of the title compound are hydrogen bonded with O·O distances of 2.68 Å and 2.58 Å. Due to the symmetry of the space group, the hydrogen atoms are necessarily located in the center of the O·O distance. Parameters of repulsive deformations for bond angles have been defined. Due to overcrowding in the region ofo,o-substitution, significant deformations of exocyclic bond angles have been observed. The magnitudes of these deformations depend roughly on the spatial requirements of the sterically interacting substituents, expressed by Charton's [1] parameter. 相似文献
26.
Quantifying the urbanization level is an essential yet challenging task in urban studies because of the high complexity of this phenomenon. The urbanization degree has been estimated using a variety of social, economic, and spatial measures. Among the spatial characteristics, the Shannon entropy of the landscape pattern has recently been intensively explored as one of the most effective urbanization indexes. Here, we introduce a new measure of the spatial entropy of land that characterizes its parcel mosaic, the structure resulting from the division of land into cadastral parcels. We calculate the entropies of the parcel areas’ distribution function in different portions of the urban systems. We have established that the Shannon and Renyi entropies and are most effective at differentiating the degree of a spatial organization of the land. Our studies are based on 30 urban systems located in the USA, Australia, and Poland, and three desert areas from Australia. In all the cities, the entropies behave the same as functions of the distance from the center. They attain the lowest values in the city core and reach substantially higher values in suburban areas. Thus, the parcel mosaic entropies provide a spatial characterization of land to measure its urbanization level effectively. 相似文献
27.
We presented a theoretical study of electronic band structure of three compounds ZnAl2Te4, ZnGa2Te4 and ZnIn2Te4 using pseudo potential method within density functional theory. Calculated band structures show that all band gaps are direct with at Γ with values of 1.639eV for ZnAl2Te4, 1.026eV for ZnGa2Te4and 0.836eV ZnIn2Te4. The linear properties based on dielectric function and non-linear optical properties based on second harmonic generation (SHG) were computed. The origin of four critical points (peaks) determined from the second derivative of the imaginary part of the dielectric function is elucidated. The use of individual k-points and individual combination of valence and conduction bands dependent matrix of the dielectric function and the nonlinear optical susceptibility allowed to a precise determination of inter band optical transitions. Indeed, inter-band analysis shows the high intensity of non-linear effect compared to linear effect. Moreover, non-linear inter-band optical transitions involve lower valence bands and higher conduction bands. 相似文献
28.
This paper presents an automatic scoring method for p53 immunostained tissue images of oral cancer that consist of tissue image segmentation, splitting of clustered nuclei, feature extraction and classification. The tissue images are segmented using entropy thresholding technique in which the optimum threshold value to each color component is obtained by maximizing the global entropy of its gray-level co-occurrence matrix and clustered cells are separated by selectively applying marker-controlled watershed transform. Cell nuclei feature is extracted by maximal separation technique (MS) based on blue component of tissue image and subsequently, each cell is classified into one of four categories using multi-level thresholding. Finally, IHC score of tissue images have been determined using Allred method. A statistical analysis is performed between immuno-score of manual and automatic method, and compared with the scores that have obtained using other MS techniques. According to the performance evaluation, IHC score based on blue component that has high correlation coefficients (CC) of 0.95, low mean difference (MD) of 0.15, and a very close range of 95% confidence interval with manual scores. Therefore, automatic scoring method presented in this paper has high potential to help the pathologist in IHC scoring of tissue images. 相似文献
29.
Białecka-Florjańczyk E 《The journal of physical chemistry. B》2006,110(6):2582-2592
The phase behavior of some rodlike block molecules has been reviewed with reference to the polarity of constituent segments. It was found that the ability of the mesophase formation is connected with differences in polar character between the flexible chains and rigid cores. Thus the polar poly(oxyethylene) group connected with the polar rigid core reduces mesophase stability but is advantageous when put together with some apolar building blocks. An attempt at quantitative estimation of the incompatibilities of different parts of molecules by means of Hansen solubility parameters delta and Flory interaction parameters chi has also been made. On the basis of chi parameters the Gibbs free energies of mixing of these segments were calculated. The changes of Gibbs free energy reflecting the compatibility of segments and their tendency to the phase separation and the volume fraction of mesogenic rigid core reflecting their ability to arrangement in one direction appear to be crucial in terms of type of the mesophase formation. 相似文献
30.
B. Pniewska T. Stankiewicz P. Sałański J. Jurczak 《Journal of chemical crystallography》1995,25(2):69-73
4,7,13,16-tetraoxa-1,10-diaza-5,6-benzocyclooctadeca-11,18-dione, C16H22N2O6·H2O, (3) was synthesized under thermal conditions, starting from ,-diamine (1) and ,-diester (2). The hydrate of compound (3) was investigated in the solid state by X-ray structural analysis. Crystal data: monoclinic system, space group P21/c,a=12.342(4) Å,b=15.978(7) Å,c=8.960(3) Å, =96.72(3)°,Z=4. The structure was solved by direct methods and refined to finalR=0.056,R
w=0.069 for 1962 observed reflections. The structure exhibits internal hydrogen bonds between the etheral O(16) atom and the neighboring amide group. The water molecule connects diamide molecules by one strong hydrogen bond with carbonyl oxygen, and four weak hydrogen bonds with the amide groups and etheral oxygen atoms. 相似文献