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991.
Silas Arandas Monteiro e Silva Michele Fernanda Costa Valarini Marlus Chorilli Stig E. Friberg 《Journal of Dispersion Science and Technology》2014,35(8):1191-1199
Formulations with lyotropic liquid crystals were prepared from a Brazilian nut vegetable oil, guarana extract and combination of sorbitan monooleate (Span 80) and sorbitan monolaurate ethoxylate EO 20 (Tween 20) in the ratio 1:3 (surfactant component) and their physical–chemical aspects and rheological properties were determined. Compositions with liquid crystals were found in the pseudoternary diagram in a surfactant range of 70–90% and polarized light microscopy, small-angle x-ray scattering (SAXS) showed them to be lamellar. The preparations were furthermore characterized rheologically by shear stress shear rate sweeps finding plastic and pseudoplastic behavior without thixotropy. Electric conductivity and pH measurements demonstrated a potential for future application as dermatological delivery system of the active compounds in the Bertholletia excelsa and Paullinia cupana. 相似文献
992.
Electrochemical Oxidation of Donepezil and Its Voltammetric Determination at Gold Electrode 下载免费PDF全文
Aleksandar R. Mladenović Dušan Ž. Mijin Saša Ž. Drmanić Vlatka E. Vajs Vladislava M. Jovanović Slobodan D. Petrović Milka L. Avramov Ivić 《Electroanalysis》2014,26(5):893-897
The oxidative ability of donepezil, a frequently prescribed drug for the treatment of Alzheimer’s disease is reported for the first time at a gold electrode. It was oxidized by cyclic voltammetry and determined by square wave voltammetry in phosphate buffer electrolyte. Electrochemical degradation of donepezil was carried out by long term potential cycling. The identification and characterization of the major product, isolated by preparative high performance liquid chromatography, was performed by high resolution mass spectrometry and 1D and 2D nuclear magnetic resonance spectroscopy. Donepezil hydroxy derivative was identified as the major electrochemical oxidation product from donepezil. 相似文献
993.
Popović DM Zmirić A Zarić SD Knapp EW 《Journal of the American Chemical Society》2002,124(14):3775-3782
Charge separation and radical transfer in DNA photolyase from Escherichia coli is investigated by computing electrostatic free energies from a solution of the Poisson-Boltzmann equation. For the initial charge separation 450 meV are available. According to recent experiments [Aubert et al. Nature 2000, 405, 586-590] the flavin receives an electron from the proximal tryptophan W382, which consequently forms a cationic radical WH(*)(+)382. The radical state is subsequently transferred along the triad W382-W359-W306 of conserved tryptophans. The radical transfer to the intermediate tryptophan W359 is nearly isoenergetic (58 meV uphill); the radical transfer from the intermediate W359 to the distal W306 is 200 meV downhill in energy, funneling and stabilizing the radical state at W306. The resulting cationic radical WH(*)(+)306 is further stabilized by deprotonation, yielding the neutral radical W(*)306, which is 214 meV below WH(*)(+)306. The time scale of the charge recombination process yielding back the resting enzyme with FADH(*) is governed by reprotonation of W306, with a calculated lifetime of 1.2 ms that correlates well with the measured lifetime of 17 ms. In photolyase from Anacystis nidulans the radical state is partially transferred to a tyrosine [Aubert et al. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 5423-5427]. In photolyase from Escherichia coli, there is a tyrosine (Y464) close to the distal tryptophan W306 that could play this role. We show that this tyrosine cannot be involved in radical transfer, because the electron transfer from tyrosine to W306 is much too endergonic (750 meV) and a direct hydrogen transfer is likely too slow. Coupling of specific charge states of the tryptophan triad with protonation patterns of titratable residues of photolyase is small. 相似文献
994.
Rimantė Zinkutė Ričardas Taraškevičius Tomas Želvys 《Central European Journal of Chemistry》2011,9(2):337-347
The relationship between real total contents of the major elements Na, Mg, Al, Si, P, S, K, Ca, Ti, Fe and the trace elements
Ag, As, B, Ba, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se, Sn, V, U, Zn in topsoil from the central part of Vilnius is analysed. The
amounts of most elements were determined by energy-dispersive X-ray fluorescence, while amounts of Ag, B, Co were measured
by optical atomic emission spectrophotometry. Two factors were distinguished according to major elements: anthropogenic (A)
including Ca, Mg, Fe, P, S and clayey (C) including K, Al, Ti. Boron, Mn, Cr and U are significantly correlated with members
of both factors, Sb with none of them and other trace elements either with all (Cu, Zn, Pb, Se, Ba, Ni, Co) or with separate
(V, Ag, Sn, Mo, As) members of the A-factor. Only B, Mn, Cr, U (partly their additive index Z1) are influenced by the C-factor,
while twelve other trace elements (also their additive index Z2) are influenced by the A-factor. The additive index Z of all
17 elements is also affected by the A-factor. Four groups of sites have been distinguished according to normal or higher contents
of both factors. The majority of trace element anomalies are related to the sites affected by the A-factor. 相似文献
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