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1.
A simple and sensitive kinetic method was developed for the determination of ritodrine hydrochloride in pharmaceutical preparations. The method is based upon a kinetic investigation of the oxidation reaction of the drug with alkaline potassium permenganate at room temperature for a fixed 12.5 min; the absorbance of the colored permenganate ion was measured at 609 nm. The absorbance concentration plots were rectilinear over the range of 1.6–11.2 μg mL?1 (r = 0.9992) with a minimum detectability of 0.096 μgmL?1 (2.88 × 10?7 M). The different experimental parameters affecting the development and stability of color were carefully studied and optimized. The determination of ritodrine hydrochloride by the fixed concentration and rate constant methods is also feasible with the calibration equations obtained, but the fixed time method has been found to be more applicable. The proposed method was applied successfully to the determination of ritodrine hydrochloride in tablets and ampoules with average recoveries of 100.37 ± 0.93% and 100.42 ± 0.87%, respectively. The results obtained were in good agreement with those obtained using a reference method for comparison. A proposal of the reaction pathway is also presented. 相似文献
2.
Single molecule fluorescence resonance energy transfer has been extensively used to measure distance changes and kinetics in various biomolecular systems. However, due to complications involving multiple de-excitation pathways of the dyes, the absolute inter-dye distance information has seldom been recovered. To circumvent this we directly probe the relative variations in the quantum yield of individual fluorophores. B-DNA was used as a scaffold to position the donor (Cy3 or TMR) at precise distances from the acceptor (Cy5) within the Forster radius. We found that the variation in the Cy3 quantum yield is approximately 5 times larger than that of TMR. By taking into account the molecule-to-molecule variability in the acceptor/donor quantum yield ratio, the apparent fluorescence resonance energy transfer efficiencies were scaled to yield the theoretical values. We obtained very good agreement with a physical model that predicts distances along B-DNA. 相似文献
3.
Thiation of [1,2,4]triazino[3,2-b]quinazoline-3,10-dione 1 proceeds selectively to give the 3-thioxo-analog 3 . The latter was converted to the corresponding 3-methylthio derivative 4 which was reacted with aniline and hydrazine to give the corresponding anilino- and hydrazino derivatives 5 and 7 . Compound 7 was converted to the hydrazones 8a,b and into the novel heterocyclic ring systems [1,2,4]triazolo[4′,3′:4,5][1,2,4]triazino-[3,2-b]quinazolin-7-ones 9, 10a,b and tetrazolo[1′,5′:4,5][1,2,4]triazino[3,2-b]quinazolin-7-one 11 . 相似文献
4.
5.
A series of PVA/PVP/clay nanocomposite were prepared by gamma irradiation with different clay contents of (0.15, 0.3, 1, 1.5, 3 and 5 wt%). The gelation content and swelling behavior were investigated. The morphology and structure of PVA/PVP/clay nanocomposite and dispersion of the clay nanoparticles in the polymeric matrix were examined by infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The introduction of clay into polymeric matrix was investigated by X-ray diffraction pattern (XRD) and Transmission electron microscope (TEM). It is observed that, the increase of the clay content causes a decrease in the swelling percent. The thermal stability studies confirmed that the introduction of clay lead to an increase in the thermal stability. The TEM results showed that the clay nanoparticles are interchelated or exfoliated in the polymeric matrix. Some desirable characteristics such as relatively good swelling and excellent barrier capability against microbe penetration suggested that PVA/PVP/clay nanocomposite can be a good candidate as a wound dressing. 相似文献
6.
The energy eigenvalues of coupled oscillators in two dimensions with quartic and sextic couplings have been calculated to a high accuracy. For this purpose, unbounded domain of the wave function has been truncated and various combination of trigonometric functions are employed as the basis sets in a Rayleigh-Ritz variational method. The method is applicable to the multiwell oscillators as well. © 1996 John Wiley & Sons, Inc. 相似文献
7.
M. A. Eid A. A. Fakhry A. A. Mahdy K. A. Eid J. A. C. Broekaert 《Fresenius' Journal of Analytical Chemistry》1995,351(2-3):190-196
Results are presented of ICP-AES determinations of 13 rare earth elements (REE), Sc and Y in 47 core samples of 10 bore holes in the phosphate deposit of the Abu-Tartur area, Western Desert, Egypt. The complete dissolution of the samples was achieved by digestion with HF/HNO3/HCl in a closed PTFE decomposition vessel. Such analytical lines were selected that showed no spectral interferences from the major constituents of the phosphate samples or from other REE in the samples. The precision for the determination of the individual elements for the whole procedure ranges from 0.8% to 4.0%. Also, smooth normalized chondrite and shale patterns were obtained. The results revealed that the total REE content in the investigated samples was between 0.8 and 2 mg/g, which is remarkably high when compared with many phosphate deposits in other parts of the world. The results also showed that the concentrations of individual REE as well as their total concentrations in the samples follow their P2O5 content, indicating that the REE may be accumulated within the phosphate fraction of the phosphate bearing sediments.Presented at the Rare Earth Minerals Conference, London (UK), April 1 and 2 (1993) 相似文献
8.
The spectral distributions of the visible absorption and fluorescence emission under electron beam excitation of Eu3+-doped (Y2O3) and (YVO4) powders have been detected and analyzed. (Y2O3: Eu3+) has a cubicC crystal structure with a unit cell dimension a=10·61 Å. Its observed transitions from7
F
0 to many upper states have been recognized; the observed number of Stark components is in agreement with that based on theC
2 site symmetry of the Eu3+ ion in Y2O3. Eu3+-doped yttrium vanadate has a typical zircon tetragonal crystal structure with unit cell dimensions ofc=6·29 Å anda=7·11 Å. The observed transitions in (Eu3+: YVO4) have been identified and assigned in accordance with theD
2d site symmetry of the Eu3+ ion in this lattice.The authors would like to express their deep gratitude to Professor G. F. J.Garlick, University of Hull, England, for offering experimental facilities in his Physics Department. 相似文献
9.
The consecutive stepwise formation constants of 1:1 and 1:2 chelate species formed by the interaction of DC-2-CPHD and DC-3-CPHD anions with tripositive lanthanon and divalent copper, nickel, cobalt, zinc, manganese, and cadmium cations were determined potentiometrically at ionic strengh of 0.1 (KNO3) and 30°C. The results indicate that two different coordination modes, one tridentate (DC-2-CPHD), and one bidentate (DC-3-CPHD), are in evidence. 相似文献
10.
N. M. Stewart E. Eid M. S. S. El-Daghmah J. K. Jabber 《Zeitschrift für Physik A Hadrons and Nuclei》1990,335(1):13-23
The energy level schemes of152Gd and152Sm have been established on the basis of singlesγ-spectra, andγ- γ coincidence measurements. Ge(Li) detectors were used to study the gamma spectra produced in the EC/β+ and β? decays of152Eu to152Sm and152Gd, respectively. Thirteen new transitions are reported and data from eleven coincidence gates enabled five new levels to be suggested. Relative intensities and logf t values were calculated and spin/parities deduced. Comparisons are made with new predictions of the Interacting Boson Model. 相似文献