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891.
Wietecha-Posłuszny R Garbacik A Woźniakiewicz M Kościelniak P 《Analytical and bioanalytical chemistry》2011,399(9):3233-3240
The objective of this research was to develop, optimize, and validate a modern, rapid method of preparation of human hair
samples, using microwave irradiation, for analysis of eight tricyclic antidepressants (TCADs): nordoxepin, nortriptyline,
imipramine, amitriptyline, doxepin, desipramine, clomipramine, and norclomipramine. It was based on simultaneous alkaline
hair microwave-assisted hydrolysis and microwave-assisted extraction (MAH–MAE). Extracts were analyzed by high-performance
liquid chromatography with diode-array detection (HPLC–DAD). A mixture of n-hexane and isoamyl alcohol (99:1, v/v) was used as extraction solvent and the process was performed at 60°C. Application of 1.0 mol L−1 NaOH and microwave irradiation for 40 min were found to be optimum for hair samples. Limits of detection ranged from 0.3
to 1.2 μg g−1 and LOQ from 0.9 to 4.0 μg g−1 for the different drugs. This enabled us to quantify them in hair samples within average therapeutic concentration ranges. 相似文献
892.
Kokot ZJ Matysiak J Urbaniak B Dereziński P 《Analytical and bioanalytical chemistry》2011,399(7):2487-2494
The aim of this study was to develop a new precise and accurate CZE-DAD method for honeybee venom analysis using cytochrome
c as an internal standard. The 64.5 cm total length, 56 cm effective length, 75 μm ID, and 360 μm OD uncoated fused-silica
capillary was used. The samples were injected into the capillary under a 50-mbar pressure for 7 s. There were 15 kV of electric
field across the capillary applied. The current intensity was 26 μA. The separation was carried out at 25 °C. The analysis
was run with the normal electrode polarity. The following steps and parameters were taken into account for the validation
of the developed method: selectivity, precision, accuracy, linearity, limit of detection and limit of quantitation. All steps
of the validation procedure proved that the developed analytical procedure was suitable for its intended purpose. Possibly
this was the first study in which several honeybee venom components were separated and five of them were identified by capillary
zone electrophoresis. In addition, the developed method was applied for quantitative analysis of 38 honeybee venom samples.
The content (relative to the dry venom mass) of analyzed peptides in honeybee venom samples collected in 2002–2007 was as
follows: apamine from 0.93% to 4.34% (mean, 2.85 ± 0.79%); mast cell degranulating peptide (MCDP) from 1.46% to 4.37% (mean,
2.82 ± 0.64%); phospholipase A2 from 7.41% to 20.25% (mean, 12.95 ± 3.09%); melittin from 25.40% to 60.27%, (mean, 45.91 ± 9.78%). The results were compared
with the experimental data obtained for the same venom samples analyzed earlier by the HPLC method. It was stated that HPCE
and HPLC data did not differ significantly and that the HPCE method was the alternative for the HPLC method. Moreover, using
the results obtained principal component analysis (PCA) was applied to clarify the general distribution patterns or similarities
of four major honeybee venom constituents collected from two different bee strains in various months and years. PCA has shown
that the strain of bee appears to be the only criteria for bee venom sample classification. Strong correlations between apamine,
MCDP, phospholipase A2, and melittin were confirmed. These correlations have to be taken into account in the honeybee venom standardization. The
developed method due to its simplicity can be easily automated and incorporated into routine operations both in the bee venom
identification, quality control, and standardization of the product. 相似文献
893.
Tecmer P Gomes AS Ekström U Visscher L 《Physical chemistry chemical physics : PCCP》2011,13(13):6249-6259
The performance of the time-dependent density functional theory (TDDFT) approach has been evaluated for the electronic spectrum of the UO(2)(2+), NUO(+) and NUN molecules. Different exchange-correlation functionals (LDA, PBE, BLYP, B3LYP, PBE0, M06, M06-L, M06-2X, CAM-B3LYP) and the SAOP model potential have been investigated, as has the relative importance of the adiabatic local density approximation (ALDA) to the exchange-correlation kernel. The vertical excitation energies have been compared with reference data obtained using accurate wave-function theory (WFT) methods. 相似文献
894.
Leopold Koczan Pawe? Zaprawa 《Applied mathematics and computation》2011,217(15):6644-6651
In the paper we consider the class Γ of analytic and univalent functions f in the unit disk Δ, normalized by f(0) = f′(0) − 1 = 0, having real coefficients and such that f(Δ) is convex in the direction of the real axis. We are especially interested in some subclasses of Γ. The most important of them is Γ(c) consisting of those functions which have the second coefficients of the Taylor expansion fixed and equal to c. We obtain the Koebe set for this class as well as for the classes Γ+(c) and Γ−(c) of functions which are in some sense convex in the direction of positive and negative axes respectively. 相似文献
895.
A sensitive and selective analytical method for the quantification of pregabalin, sildenafil and the active desmethyl metabolite of sildenafil (UK-103320) has been developed. The method can simultaneously quantify the three analytes within the expected in vivo concentration ranges using 50 ??L of rat plasma. It utilises solid-phase extraction followed by high performance liquid chromatography coupled with tandem mass spectrometry. Quantitation in rat plasma demonstrated good accuracy and precision over the following dynamic ranges for each analyte: pregabalin (70?C10,000 ng mL?1), sildenafil (1?C2,000 ng mL?1) and UK-103320 (1?C2,000 ng mL?1). For each analyte, the following lower limits of quantitation were obtained: 70 ng mL?1 for pregabalin and 1 ng mL?1 for sildenafil and UK-103320, respectively. The method was successfully used to analyse plasma samples from rats when pregabalin and sildenafil were administered in combination. 相似文献
896.
Zarzycki PK Zarzycka MB Clifton VL Adamski J Głód BK 《Journal of chromatography. A》2011,1218(33):5694-5704
The goal of this paper is to demonstrate the separation and detection capability of eco-friendly micro-TLC technique for the classification of spirulina and selected herbs from pharmaceutical and food products. Target compounds were extracted using relatively low-parachor liquids. A number of the spirulina samples which originated from pharmaceutical formulations and food products, were isolated using a simple one step extraction with small volume of methanol, acetone or tetrahydrofuran. Herb samples rich in chlorophyll dyes were analyzed as reference materials. Quantitative data derived from micro-plates under visible light conditions and after iodine staining were explored using chemometrics tools including cluster analysis and principal components analysis. Using this method we could easily distinguish genuine spirulina and non-spirulina samples as well as fresh from expired commercial products and furthermore, we could identify some biodegradation peaks appearing on micro-TLC profiles. This methodology can be applied as a fast screening or fingerprinting tool for the classification of genuine spirulina and herb samples and in particular may be used commercially for the rapid quality control screening of products. Furthermore, this approach allows low-cost fractionation of target substances including cyanobacteria pigments in raw biological or environmental samples for preliminary chemotaxonomic investigations. Due to the low consumption of the mobile phase (usually less than 1 mL per run), this method can be considered as environmentally friendly analytical tool, which may be an alternative for fingerprinting protocols based on HPLC machines and simple separation systems involving planar micro-fluidic or micro-chip devices. 相似文献
897.
898.
Jaworska A Wietecha-Posłuszny R Woźniakiewicz M Kościelniak P Malek K 《The Analyst》2011,136(22):4704-4709
The potential use of surface Raman enhanced spectroscopy (SERS) for confirmatory identification and the semi-quantitative analysis of selected tricyclic antidepressants (TCAs) is examined utilizing a conventional silver colloid. Raman and SERS spectra of aqueous solutions of imipramine (Imi) and its metabolite, desipramine (Des), were recorded as the function of concentration using NIR excitation. A good linear correlation is observed for the dependence of the SERS signal at 684 cm(-1) (R(2) = 0.9997) on Imi concentration over the range of 0.75-7.5 μM. The limit of detection of imipramine in the silver colloidal solution is 0.98 μM. SERS spectra of Imi and Des were also recorded for blood plasma samples without prior purification as well as after the use of standard solid phase extraction. All spectra show the characteristic spectral profile of the molecules and moreover, stronger signal enhancement is observed for Imi in the "raw" samples as opposed to Imi extracted from a biological matrix. 相似文献
899.
Adam Bartoszek Rémi Langevin Paweł G. Walczak 《Bulletin of the Brazilian Mathematical Society》2011,42(2):301-320
Canal surfaces defined as envelopes of 1-parameter families of spheres, can be characterized by the vanishing of one of the conformal principal
curvatures. We distinguish special canals which are characterized by the fact that the non-vanishing conformal principal curvature is constant along the characteristic
circles and show that they are conformally equivalent to either surfaces of revolution, or to cones over plane curves, or
to cylinders over plane curves, so they are isothermic. 相似文献
900.
For a given pure state of a composite quantum system we analyze the product of its projections onto a set of locally orthogonal separable pure states. We derive a bound for this product analogous to the entropic uncertainty relations. For bipartite systems the bound is saturated for maximally entangled states and it allows us to construct a family of entanglement measures, we shall call collectibility. As these quantities are experimentally accessible, the approach advocated contributes to the task of experimental quantification of quantum entanglement, while for a three-qubit system it is capable to identify the genuine three-party entanglement. 相似文献