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121.
122.
An efficient microwave assisted extraction of phenolic compounds and antioxidant potential of Ginkgo biloba 总被引:1,自引:0,他引:1
Flavonoid glycosides are a significant group of compounds found in Ginkgo biloba leaves, but the long extraction procedures in existing methods are a challenging problem. In this work, a microwave-assisted extraction (MAE) method has been developed for extracting bioactive compounds from G. biloba. Several variables were optimized, such as extracting solvent, microwave power, and extraction time that can potentially affect the extraction yield. The total phenolic content, antioxidant activity (using DPPH, ABTS and FRAP assays) and flavonoid glycosides of different extracts using RP-HPLC were assessed. The antioxidant capacity was found to be highest with MAE using 60% aq. ethanol as extracting solvent and microwave power of 120W for 20 min. 相似文献
123.
In this paper we report the modified solid state synthesis of Ce3+ activated Sr6B5AlO15, Ca6B5AlO15 Ba6B5AlO15 and mixed host aluminoborate phosphors. The prepared phosphors were characterized by photoluminescence technique. The PL excitation spectra showed the excitation peaks ranging from 300 to 400 nm and emission spectra are observed in UV-blue region of spectrum and it varied for different hosts. This kind of emission is due to 4f65d → 4f7 transition of Ce3+ ion. Further PLE and PL emission spectra for various compositions Ca5Sr1B5AlO15, Ca4Sr2B5AlO15, Ca3Sr3B5AlO15, Ca2Sr4B5AlO15, CaSr5B5AlO15 are also taken which shows Ce3+ emission at 428 nm, 425 nm, 432 nm, 427 nm, 438 nm respectively. The calculated 2FJ (J = 7/2, 5/2) energy gap of Ce3+ in all hosts have been calculated and obtained values for Sr6B5AlO15, Ba6B5AlO15 phosphors are 1888 cm−1 and 1330 cm−1 respectively. PL emission spectra of mixed host aluminoborates have shown slight variations in positions of emission peaks. 相似文献
124.
Ren C Zhang L Freitas MA Ghoshal K Parthun MR Jacob ST 《Journal of the American Society for Mass Spectrometry》2005,16(10):1641-1653
The acetylated isoforms of histone H4 from mouse lymphosarcoma cells treated with HDAC inhibitors trichostatin A (TSA) and depsipeptide (DDP) were separated by acetic acid urea-polyacrylamide gel electrophoresis (AU-PAGE), in-gel digested, and analyzed by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and liquid chromatography tandem mass spectrometry (LC-MS/MS). The acetylation pattern of histone H4 in mouse lymphosarcoma cells induced by TSA was established in which acetylation initially occurred at K16 followed by K12 and then K8 and/or K5. An identical order of acetylation was found for cells treated with DDP. 相似文献
125.
Summary An attempt is made to study the thermoelectric power of the carriers in quantum well of A
3
II
B
2
V
semiconductors, taking Cd3As2 quantum well as an example. It is found, on the basis of newly derived 2DE−k
s
dispersion relation by including various types of anisotropies in the energy spectrum that the thermoelectric power decreases
with increasing electron concentration and decreasing film thickness respectively. In addition, the corresponding well-known
results for bulk specimens of isotropic parabolic energy bands are also obtained from the expressions derived. 相似文献
126.
A vibrational and rotational analysis is presented for the D′ → A′ transition (2800–2950 Å) of Br2. The analysis includes 11 rotationally analyzed bands for 79Br2 and 3 for 81Br2, plus bandheads for 70 additional v′-v″ bands of 79Br2, 81Br2, and 79Br81Br. The latter include some violet-degraded and spikelike features at the long-wavelength end of the spectrum, which are interpreted and assigned with the aid of band profile simulations. The assigned features are fitted directly to 14 vibrational and rotational expansion parameters for the two electronic states, from which the following spectroscopic constants are obtained: ΔTe = 35706 cm?1, ω′e = 150.86 cm?1, ω″e = 165.2 cm?1, B′e = 0.042515 cm?1, B″e = 0.05944 cm?1, , . The spectroscopic parameters are used to calculate RKR potentials and Franck-Condon factors for the transition. 相似文献
127.
We show that matter effects change the numu-->nutau oscillation probability by as much as 70% for certain ranges of energies and path lengths. Consequently, the numu-->nutau survival probability also undergoes large changes. A proper understanding of numu survival rates must consider matter effects in Pmutau as well as Pmue. We comment on (a) how these matter effects may be observed and the sign of Delta31 determined in atmospheric neutrino measurements and at neutrino factories, and (b) how they lead to heightened sensitivity for small theta13. 相似文献
128.
We study bicomponents in networks, sets of nodes such that each pair in the set is connected by at least two independent paths, so that the failure of no single node in the network can cause them to become disconnected. We show that standard network models predict there to be essentially no small bicomponents in most networks, but there may be a giant bicomponent, whose presence coincides with the presence of the ordinary giant component, and we find that real networks seem by and large to follow this pattern, although there are some interesting exceptions. We also study the size of the giant bicomponent as nodes in the network fail and find in some cases that our networks are quite robust to failure, with large bicomponents persisting until almost all vertices have been removed. 相似文献
129.
Peerannawar Swarada Sood Abha Brown Alicia Schäfer Christian Alonzo Judith Sutton Steven Christianson Matthew Stocking Raven Naclerio Nicole Török Béla Landge Shainaz M. 《Structural chemistry》2019,30(5):1941-1956
Structural Chemistry - The effect of solvents has been found as a crucial factor in determining the regioselectivity of the hydroxyalkylation of indole with trifluoroacetaldehyde hemiacetals. The... 相似文献
130.
A weak emission spectrum of I2 near 2770 Å is reanalyzed and found to to minate on the A(1u3Π) state. The assigned bands span v″ levels 5–19 and v′ levels 0–8. The new assignment is corroborated by isotope shifts, band profile simulations, and Franck-Condon calculations. The excited state is an ion-pair state, probably the 1g state which tends toward . In combination with other results for the A state, the analysis yields the following spectroscopic constants: T″e = 10 907 cm?1, ″e = 1640 cm?1, ω″e = 95 cm?1, ; T′e = 47 559.1 cm?1, ω′e = 106.60 cm?1, . 相似文献