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241.
242.
Noemi Monni Jos J. Baldoví Víctor García-Lpez Mariangela Oggianu Enzo Cadoni Francesco Quochi Miguel Clemente-Len Maria Laura Mercuri Eugenio Coronado 《Chemical science》2022,13(25):7419
By combining 3,6-N-ditriazolyl-2,5-dihydroxy-1,4-benzoquinone (H2trz2An) with NIR-emitting ErIII ions, two different 3D neutral polymorphic frameworks (1a and 1b), differing in the number of uncoordinated water molecules, formulated as [Er2(trz2An)3(H2O)4]n·xH2O (x = 10, a; x = 7, b), have been obtained. The structure of 1a shows layers with (6,3) topology forming six-membered rings with distorted hexagonal cavities along the bc plane. These 2D layers are interconnected through the N4 atoms of the two pendant arms of the trz2An linkers, leading to a 3D framework, where neighboring layers are eclipsed along the a axis, with hexagonal channels filled with water molecules. In 1b, layers with (6,3) topology in the [101] plane are present, each ErIII ion being connected to three other ErIII ions through bis-bidentate trz2An linkers, forming rectangular six-membered cavities. 1a and 1b are multifunctional materials showing coexistence of NIR emission and field-induced slow relaxation of the magnetization. Remarkably, 1a is a flexible MOF, showing a reversible structural phase transition involving shrinkage/expansion from a distorted hexagonal 2D framework to a distorted 3,6-brickwall rectangular 3D structure in [Er2(trz2An)3(H2O)2]n·2H2O (1a_des). This transition is triggered by a dehydration/hydration process under mild conditions (vacuum/heating to 360 K). The partially dehydrated compound shows a sizeable change in the emission properties and an improvement of the magnetic blocking temperature with respect to the hydrated compound, mainly related to the loss of one water coordination molecule. Theoretical calculations support the experimental findings, indicating that the slight improvement observed in the magnetic properties has its origin in the change of the ligand field around the ErIII ion due to the loss of a water molecule.Tuning of luminescent and SIM properties is herein reported, in a novel flexible 3D anilato-based ErIII-MOF, displaying reversible shrinkage/expansion from a distorted hexagonal to a 3,6-brickwall rectangular structure. 相似文献
243.
Rubn Alvarez‐Rodríguez Francisco Javier Arias Mercedes Santos Ana María Testera Jos Carlos Rodríguez‐Cabello 《Macromolecular rapid communications》2010,31(6):568-573
Here, we describe a procedure to manufacture smart hybrid probes that exhibit tunable optical properties as a function of multiple environmental variations. Initially, we achieved a one‐pot synthesis of gold‐PREP (photo‐responsive elastin‐like polymer) conjugate Gold‐AzoGlu15 via reduction of auric acid in the presence of PREP AzoGlu15 . Outstandingly, Gold‐AzoGlu15 exhibited pH and temperature sensitiveness. However, Gold‐AzoGlu15 was not UV‐vis sensitive. We noticed that photo‐isomerisation of azobenzene moieties in Gold‐AzoGlu15 could not be detected by UV‐vis spectroscopy. In a subsequent step, we explored the use of cyclodextrins and the formation of alkanethiol mixed‐monolayers over mother Gold‐AzoGlu15 by thiol‐place exchange reactions in order to decouple photo‐isomerisation of azobenzene from the bulk phase absorption. In this sense we achieved the synthesis of β‐cyclodextrin capped Gold‐CD‐AzoGlu15 . Notable was that cis‐trans photo‐conversion of azobenzene groups in Gold‐CD‐AzoGlu15 could be successfully detected. Finally, we present the optical properties exhibited by multi‐sensitive probe Gold‐CD‐AzoGlu15 as a function of pH, temperature and UV‐vis irradiation. We think that gold‐PREP hybrids could be of great interest in the design of multi‐functional chromophore‐metal nanocomposites that operate in aqueous media for the development of multi‐stimuli sensitive detectors for biosensing applications.