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排序方式: 共有222条查询结果,搜索用时 187 毫秒
91.
Bartczak Piotr Fält Pauli Penttinen Niko Ylitepsa Pasi Laaksonen Lauri Lensu Lasse Hauta-Kasari Markku Uusitalo Hannu 《Optical Review》2017,24(2):105-116
Optical Review - Retinal photography is a standard method for recording retinal diseases for subsequent analysis and diagnosis. However, the currently used white light or red-free retinal imaging... 相似文献
92.
The relative thermodynamic stabilities of the geometrical isomers of a number of 1,2-dialkoxyethenes have been determined by chemical equilibration in the neat liquid and in 1,4-dioxane solution with mercuric acetate as catalyst. From the variation of the value of the equilibrium constant with temperature, the thermodynamic parameters G
, H
, and S
of theE Z isomerization were evaluated. In all cases theZ isomer proved to be thermodynamically the more stable species, its favor increasing with the bulkiness of the alkoxy groups. The thermodynamic data obtained for theEZ isomerization of 1,2-dimethoxyethene differ significantly from those reported in the literature. An attempt to correlate the experimental thermodynamic data with MM2 calculations for the title compounds as well as for 1,2-dimethoxypropenes is presented. 相似文献
93.
An automated turbidimetric method was developed for group level identification of penicillinase sensitive penicillins, tetracyclines and fluoroquinolones in kidney samples. A sample pretreatment procedure was elaborated for the extraction of incurred residues from kidney tissue in a translucent solution to enable the measurement of changes in optical density. The method was comprised of three pairs, one for each antibiotic group: a sensitive test bacterium strain and a resistant strain for the identification of fluoroquinolones and tetracyclines, and a sensitive strain with and without penicillinase for the identification of penicillinase sensitive penicillins. The algorithm employed compared the areas under the OD vs. time curves; threshold values and experimentally observed intra-test criteria were also included in the algorithm. Antibiotics were reliably identified to group level, and no false identifications were obtained with antibiotics belonging to groups not included in the reference panel. Incurred penicillin G, oxytetracycline and enrofloxacin-ciprofloxacin residues were identified at or below the MRL levels for kidney tissue. The graphically determined shortest possible identification times varied between 2 and 7 h. The method developed could furthermore easily be diversified to include other antibiotic groups by adding new "sensitive-resistant" bacterium and medium combinations. 相似文献
94.
We study adsorption at planar liquid-vapor interface of surface active binary mixtures and test three well-known models for the composition of surface phase. The models were originally presented by Guggenheim. These are compared to results for model fluids from density functional theory (DFT). The model of Laaksonen and Kulmala is in best agreement with DFT calculations. Surface mole fraction of the solute component from the Guggenheim model exceeds one for a mixture with high surface activity. The failure of the Guggenheim model is also evident in our calculations for water-methanol, water-ethanol, and water-n-propanol mixtures. 相似文献
95.
Liquid scintillation counting (LSC) and pulse shape analysis (PSA) was used in measuring radon and gross alpha- and beta-activities in groundwater. We used conventional LSC counters for the measurement of radon in water, but low-background LSC spectrometers for the gross activity measurements. The lower limit of detection (LLD) for radon in water is 0.6 Bq/l for a 60 min count with a conventional counter, but 0.1 or 0.2 Bq/l, with the two types of low-background LSC spectrometers equipped with a pulse shape analyser (PSA). The gross alpha and beta activity measurements are made using a simple sample preparation method, PSA of a low background LSC and spectrum analysis. The LLD recorded for gross alpha and beta with the two spectrometers are 0.02 and 0.03 Bq/l and 0.2 and 0.4 Bq/l, respectively, for a 180 minutes count and a 38 ml sample volume. The method also enable the calculation of the U and226Ra contents in water and indicates the presence of some other long-lived radionuclides (210Pb,228Ra or40K). The LLD for U recorded with both spectrometers is 0.02 Bq–1 and for226Ra 0.01 Bq·1–1. The LLDs attained by this LSC method are two orders of magnitude lower than the maximum permissible concentrations set for U and226Ra. 相似文献
96.
Clemente-Juan JM Coronado E Gaita-Ariño A Giménez-Saiz C Güdel HU Sieber A Bircher R Mutka H 《Inorganic chemistry》2005,44(10):3389-3395
The magnetic exchange interactions in a C0(3)(11) moiety encapsulated in Na(17) [(NaOH(2))Co(3)(H(2)O)(P(2)W(15)O(56))(2)] (NaCo(3)) were studied by a combination of magnetic measurements (magnetic susceptibility and low-temperature magnetization), with a detailed Inelastic Neutron Scattering (INS) investigation. The novel structure of the salt was determined by X-ray crystallography. The ferromagnetic Co(3)O(14) triangular cluster core consists of three octahedrally oxo-coordinated Co(II) ions sharing edges. According to the single-ion anisotropy and spin-orbit coupling usually assumed for octahedral Co(II) ions, the appropiate exchange Hamiltonian to describe the ground-state properties of the isosceles triangular Co(3) spin cluster is anisotropic and is expressed as H = - 2sigma(alpha)(=)(x,y,z)(J(alpha)(12)S(1alpha)S(2alpha) + J(alpha)(23)S(2alpha)S(3alpha) + J(alpha)(13)S(1alpha)S(3alpha)), where J(alpha) are the components of the exchange interactions between the Co(II) ions. To reproduce the INS data, nonparallel anisotropic exchange tensors needed to be introduced, which were directly connected to the molecular symmetry of the complex. The following range of parameters (value +/- 0.5 cm(-1)) was found to reproduce all experimental information while taking magnetostructural relations into account: J(x)(12) = J(y)(13) = 8.6 cm(-1); J(y)(12) = J(x)(13) = 1.4 cm(-1); J(z)(12) = J(z)(13) = 10.0 cm(-1); J(x)(23) = J(y)(23) = 6.5 cm(-1) and = 3.4 cm(-1). 相似文献
97.
Välimaa L Ylikotila J Kojola H Soukka T Takalo H Pettersson K 《Analytical and bioanalytical chemistry》2008,391(6):2135-2144
Direct measurement of time-resolved fluorescence from a washed surface of an immunoassay well constitutes an advantage compared
with label development options involving signal generation in solution. Epi-fluorometric detection collects the signal from
only a small part of the microtiter well’s bottom surface and it is inadequate for the optimal assay sensitivity when using
binding surfaces introduced by large coating volume. This study reports on the use of streptavidin-coated spots intended to
condense the binding of the labeled antibodies to coincide with the excitation beam. The spots were generated in special microtiter
wells containing 2.5-mm, 3.5-mm, and 4.5-mm diameter indentations by adsorption from liquid droplets containing either native
(SAv) or modified high-capacity (GA-SAv) streptavidin. The SAv-coated and GA-SAv-coated spots exhibited maximum Eu–biotin
binding densities of 0.080 and 0.47 pmol/mm2, respectively. A sandwich-type immunoassay of thyroid-stimulating hormone (TSH) provided a fivefold to sixfold increase in
the signal-to-background ratios of the spot assay and an equivalent improvement in the detection limit (DL < 0.01 mU/L) compared
with a reference assay.
Figure The condensation of the binding area into a spot (right) results in a denser collection of the labeled antibodies and more favorable signal-to-background ratios compared with a
regular approach using a large binding area (left) 相似文献
98.
99.
100.
Joakim Riikonen Jarno Salonen Vesa-Pekka Lehto 《Journal of Thermal Analysis and Calorimetry》2011,105(3):811-821
Thermoporometry is a relatively new method of characterising porous properties of nanostructured materials based on observation
of solid–liquid phase transitions of materials confined in pores. It provides several advantages over the conventional characterisation
methods, mercury porosimetry and gas sorption. The advantages include possibility of using short measurement times, non-toxic
chemicals and wet samples. In addition, complicated sample preparation and specialised instruments are not required. Therefore,
it has a great potential of becoming a widely utilised characterisation method, although its potential has not yet been widely
realised. In recent years, there has been a significant increase in research activities regarding the method. In the first
part of the review, we introduce thermoporometry and review related results of the confinement effects on materials and their
solid–liquid phase transition. 相似文献