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991.
《无机化学与普通化学杂志》2018,644(16):893-900
Sr8MgCe(PO4)7:Eu2+,Mn2+ phosphor with whitlockite‐type structure was prepared by a combustion‐assisted solid‐state reaction. The crystal structure and luminescence properties were investigated. Under UV radiation, Sr8MgCe(PO4)7 host exhibits a violet‐blue emission band from Ce3+ ions. When Eu2+/Mn2+ are doped into the host, the samples excited with 270 nm UV radiation present multicolor emissions due to the energy transfer (ET) from Ce3+ to Eu2+/Mn2+. The emitting color of Sr8MgCe(PO4)7:Eu2+ can be tuned from violet‐blue to yellow‐green, whereas Sr8MgCe(PO4)7:Mn2+ can emit red light. Under excitation with long wavelength at 360 nm, Sr8MgCe(PO4)7:Eu2+ phosphor shows a broadband emission from 390 to 700 nm, which is attributed to the 4f65d1→4f7 transition of Eu2+ without the contribution from Ce3+ emission. Tunable full‐color emitting light can be achieved in the Eu2+ and Mn2+‐codoped Sr8MgCe(PO4)7 phosphor by ETEu–Mn through control of the levels of doped Eu2+ and Mn2+ ions. These results suggest that Sr8MgCe(PO4)7:Eu2+,Mn2+ phosphor has potential applications in NUV chip pumped white LEDs. 相似文献
992.
本文报道了系列二肽链键联的卟啉-蒽醌及其金属配合物的微波合成,化合物的结构分别经UV-Vis,IR,1H NMR及元素分析确证。探讨了化合物分子内电子转移性质(IETP),并讨论了结构对IETP的影响。 相似文献
993.
WANG Ming LI Ying XIE ZhiYuan & WANG LiXiang State Key Laboratory of Polymer Physics Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun China 《中国科学B辑(英文版)》2011,(4)
A series of conjugated copolymers of 9,9-dioctylfluorene and symmetrical pyrazine unit (BY) were synthesized by Suzuki copolymerization and were used as novel light-emitting materials in PLEDs.Efficient energy transfer was observed in both thin film and solution.Compared with the lowest occupied molecular orbital (LUMO) energy level of the polyfluorenes homopolymer (PFO),the lower LUMO energy levels of copolymers indicated that the introduction of the BY unit would be benefit to electron injection.The turn-... 相似文献
994.
995.
996.
The epitope mapping of nucleotides bound to three chromatography supports is accomplished using saturation transfer difference (STD)-NMR spectroscopy. This experiment involves subtracting a spectrum in which the support was selectively saturated from one recorded without support saturation. In the difference spectrum only the signals of the ligands that bind to the support and received saturation transfer remain. The nucleotide protons in closer contact with the support have more intense signals due to a more efficient transfer of saturation. We investigate the effects on the binding to the nucleotides by the introduction of a spacer arm between l-histidine and Sepharose. Our NMR experiments evidence a clear contribution of the spacer to the interaction with all the nucleotides, increasing the mobility of the amino acid and giving different STD responses. This enhanced mobility originates the reinforcement of the interactions with the sugar moiety and phosphate group of 5'-CMP and 5'-TMP or the base of 5'-GMP and 5'-UMP. Hence, with this study we show that by using STD NMR technique on chromatographic systems it is possible to provide a fast, robust and efficient way of screening the atoms involved in the binding to the supports. 相似文献
997.
Edible films were prepared from methyl cellulose with various concentrations of poly(ethylene glycol) 400 (PEG400) used as a plasticizer. Water vapour and 1-octen-3-ol (an aroma compound) were selected as hydrophilic and hydrophobic volatile penetrants respectively. Their solubility and permeability through methyl cellulose-based edible films were studied using gas chromatography methods. Whatever penetrant was used, the flux increased with the PEG400 content. Transfer behaviour, i.e., the order of increased magnitude of the transfer rate, strongly depends on the nature of the volatile compound. However, water sorption only depends on the PEG400 content whereas the aroma compound sorption is affected by both the water and the PEG400 concentrations. Relationships between solubility and permeability can be partially explained by the plasticization phenomenon. 相似文献
998.
The regio- and stereoselectivity of the reactions of carbanions, generated from alkanals, carboxylates of the type XYCHCOOEt (X = EtOOC, CN, Ac; Y = H, Br), or derivatives of 3-methyl-4-phosphono-2-butenoic acid using PTC techniques, with aldehydes of various types (alkanals, ,-enals, cross-conjugated enedials, benzaldehydes,etc.) are reviewed. The factors affecting the outcome of these reactions are discussed. The carbanion analogs, triphenylphosphorus ylides, are shown to attack selectively at one of the aldehyde groups of aromatic dialdehydes. The regularities found for the title reactions were used in the syntheses of some biologically active isoprenoids.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1867–1885, October, 1995. 相似文献
999.
G. Köhler H. Martinek W. Parasuk K. Rechthaler P. Wolschann 《Monatshefte für Chemie / Chemical Monthly》1995,126(3):299-301
Summary Piperidinomethyl-2-naphthol forms inclusion complexes with -cyclodextrin with an equilibrium constant of 265M
–1 in aqueous solution. The proton transfer equilibrium between the neutral and the zwitterionic form is strongly influenced by the association.
Der Einfluß der Komplexierung mit -Cyclodextrin auf das Protontransfer-Gleichgewicht in Piperidino-2-naphthol (Kurze Mitt.)
Zusammenfassung Piperidinomethyl-2-naphthol bildet Einschlußkomplexe mit -Cyclodextrin mit einer Gleichgewichtskonstante von 265M –1. Das Protontransfer-Gleichgewicht zwischen neutraler Form und zwitterionischer Struktur wird durch diese Assoziation stark beeinflußt.相似文献
1000.
A. Zielenkiewicz K. Busserolles G. Roux-Desgranges A. H. Roux J-P. E. Grolier W. Zielenkiewicz 《Journal of solution chemistry》1995,24(7):623-632
Densities and specific heat capacities of ternary aqueous systems containing dipeptides (glycyl-glycine or L--alanyl-L--alanine) and nucleic acid bases (cytosine or thymine) or their alkyl derivatives (1,3-diethylthymine or caffeine) were determined at 25°C by flow calorimetry and flow densimetry. The partial molar volumes and heat capacities of transfer at infinite dilution of the different nucleic acid bases from water to water+dipeptide solutions were obtained therefrom. Except for the case of the transfer of cytosine to aqueous glycyl-glycine solutions where a small positive dependence of the transfer quantities was observed with the dipeptide concentration, the values of the heat capacities of transfer were in general low, positive or negative, depending on the compensation of hydrophobic-hydrophilic interactions between the dipeptide and the base. The volumes of transfer of most of the bases are very small, within the limit of the experimental error. 相似文献