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81.
Dmitriy V. Steglenko Nikolay V. Tkachenko Alexander I. Boldyrev Ruslan M. Minyaev Vladimir I. Minkin 《Journal of computational chemistry》2020,41(15):1456-1463
The structure and properties of two-dimensional phosphoborane sheets were computationally investigated using Density Functional Theory calculations. The calculated phonon spectrum and band structure point to dynamic stability and allowed characterization of the predicted two-dimensional material as a direct-gap semiconductor with a band gap of ~1.5 eV. The calculation of the optical properties showed that the two-dimensional material has a relatively small absorptivity coefficient. The parameters of the mechanical properties characterize the two-dimensional phosphoborane as a relatively soft material, similar to the monolayer of MoS2. Assessment of thermal stability by the method of molecular dynamics indicates sufficient stability of the predicted material, which makes it possible to observe it experimentally. 相似文献
82.
It is shown that chromium(III) acetylacetonate meets the requirements of calibration reference materials: it is homogeneous,
soluble in water and organic solvents, and its solutions are stable. Chromium(III) acetylacetonate has been successfully used
as a calibration reference material in the analysis of chromium in iron-base alloys. The procedure involves chromium acetylacetonate
extraction using methyl isobutyl ketone followed by direct atomic absorption analysis of the organic extract. The detection
limit of the procedure is 10 ng g−1.
Correspondence: Konstantin Belikov, State Scientific Institution “Institute for Single Crystals” of the National Academy of
Sciences of Ukraine, Kharkov, Ukraine 相似文献
83.
Andrey B. Koldobskii Nikolay P. Tsvetkov Ekaterina V. Solodova Valery N. Kalinin 《Journal of fluorine chemistry》2010,131(8):852-9595
This paper describes a novel synthetic approach to 2-cyano-3-trifluoromethylthiophenes fused with cyclobutene rings with variable spiro conjunctions. The reaction of substituted 1-bromo-2-trifluoroacetylcyclobutenes with mercaptoacetonitrile results in the substitution of bromine with S-center to afford the corresponding nitriles in high yields, which form the target thiophenes by subsequent treatment of lithium 2,2,6,6-tetramethylpiperidide and acetic anhydride. 相似文献
84.
Igor V. Zatovsky Nataliya Yu. Strutynska Nikolay S. Slobodyanik Oleg V. Shishkin 《Journal of solid state chemistry》2011,184(3):705-711
The crystallization of complex phosphates from the melts of Cs2O-P2O5-CaO-MIII2O3 (MIII—Al, Fe, Cr) systems have been investigated at fixed value Cs/P molar ratios equal to 0.7, 1.0 and 1.3 and Са/Р=0.2 and Ca/МIII=1. The fields of crystallization of CsCaP3O9, β-Ca2P2O7, Cs2CaP2O7, Cs3CaFe(P2O7)2, Ca9MIII(PO4)7 (MIII—Fe, Cr), Cs0.63Ca9.63Fe0.37(PO4)7 and CsCa10(PO4)7 were determined. Obtained phosphates were investigated using powder X-ray diffraction and FTIR spectroscopy. Novel whitlockite-related phases CsCa10(PO4)7 and Cs0.63Ca9.63Fe0.37(PO4)7 have been characterized by single crystal X-ray diffraction: space group R3c, a=10.5536(5) and 10.5221(4) Å, с=37.2283(19) and 37.2405(17) Å, respectively. 相似文献
85.
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88.
Ji Z Li Y Pritchett TM Makarov NS Haley JE Li Z Drobizhev M Rebane A Sun W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(8):2479-2491
The synthesis, one-photon photophysics and two-photon absorption (2PA) of three dipolar D-π-A 4-[9,9-di(2-ethylhexyl)-7-diphenylaminofluoren-2-yl]-2,2':6',2'-terpyridine and their platinum chloride complexes with different linkers between the donor and acceptor are reported. All ligands exhibit (1)π,π* transition in the UV and (1)π,π*/(1)ICT (intramolecular charge transfer) transition in the visible regions, while the complexes display a lower-energy (1)π,π*/(1)CT (charge transfer) transition in the visible region in addition to the high-energy (1)π,π* transitions. All ligands and the complexes are emissive at room temperature and 77 K, with the emitting excited state assigned as the mixed (1)π,π* and (1)CT states at RT. Transient absorption from the ligands and the complexes were observed. 2PA was investigated for all ligands and complexes. The two-photon absorption cross-sections (σ(2)) of the complexes (600-2000 GM) measured by Z-scan experiment are much larger than those of their corresponding ligands measured by the two-photon induced fluorescence method. The ligand and the complex with the ethynylene linker show much stronger 2PA than those with the vinylene linker. 相似文献
89.
Rebane A Drobizhev M Makarov NS Beuerman E Haley JE Krein DM Burke AR Flikkema JL Cooper TM 《The journal of physical chemistry. A》2011,115(17):4255-4262
We investigate two-photon absorption (2PA) in a series of fluorenyl-based 9,9-diethyl-2-ethynyl-7-((4-R-phenyl)ethynyl)-9,9a-dihydro-4aH-fluorene chromophores with R being various electron donating (ED) and electron withdrawing (EW) groups. We use wavelength-tunable femtosecond laser pulses to measure the 2PA cross sections in the lowest dipole-allowed transition and show that the substituents with stronger ED or EW character enhance the peak 2PA cross section (up to σ(2) ~ 60-80 GM) while the neutral substituents lead to smaller cross sections, σ(2) < 10 GM. We apply two-level approximation to establish a quantitative relation between the 2PA in the pure electronic transition (0-0) and the corresponding change of the permanent electric dipole moment upon the excitation (Δμ). This relation is elucidated by comparing Δμ values obtained from the 2PA measurements with quantum-chemical calculations and with measurements of solvatochromic shifts in a series of solvents. We show that the calculated Δμ correlate well with the values obtained from the 2PA spectroscopy. The Δμ values obtained from the solvatochromic shifts agree well with the above two methods for the chromophores with neutral or weak EW or ED substituents. On the other hand, stronger EW or ED end groups give much larger Stokes shifts, which lead to an overestimation of the Δμ values. We tentatively attribute this effect to the excitation-induced electronic density change occurring predominantly at the substituent side of the molecule, which causes the effective point dipole associated with the Δμ to interact more strongly with the surrounding solvent. 相似文献
90.
Nikolay E. Nifant'ev Yury E. Tsvetkov Alexander S. Shashkov Leonid O. Kononov Vladimir M. Menshov Alexander B. Tuzikov 《Journal of carbohydrate chemistry》2013,32(8):939-953
ABSTRACT Synthesis of two isomeric tetrasaccharides, namely Neu5Acα(2→3)Galβ(1→3)[Fucα(1→4)GlcNAcβ (sLea) and Neu5Acα(2→3)Galβ(1→4)[Fucα(1→3)]GlcNAcβ (sLex) as 3-aminopropyl glycosides is described. Preparation of these compounds was performed by sialylation of selectively protected trisaccharides Lea and Lex which contain three unsubstituted OH groups at positions 2, 3 and 4 of Gal residue. Glycosylation of Lex trisaccharide with ethylthio sialoside under promotion by NIS and TfOH in acetonitrile was effective and regio- and stereoselective to give sLex derivative in 81% yield. In contrast, sialylation of the Lca acceptor was accompanied by a variety of undesirable by-processes, namely. N-thioethylation of the GlcNAc residue, β-sialylation, and lactonisation. In order to improve the yield of sLca tetrasaccharide the glycosylation of Lea acceptor by sialyl donors of ethyl and phenyl thioglycoside (promoted by NIS-TfOH or NBS-Bu4NBr), xanthate (promotion by NIS-TfOH mixture or MeOTf) and phosphite (promoted by TMSOTf) types was also studied. Among the reactions investigated the glycosylation by phenyl thioglycoside sialoside promoted by NIS-TfOH gives the best yield (39%) of sLea tetrasaccharide product. 相似文献