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91.
Koleva BB Kolev T 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(3):786-793
The linear-dichroic infrared (IR-LD) spectroscopy of oriented solid samples as suspension in nematic liquid crystal have been carried out for experimental IR-band assignment and structural information of 2-{5,5-dimethyl-3-[2-(2,4,6-trimethoxyphenyl)vinyl]cyclohex-2-enylidene} malononitrile polymorphs. The last data have been compared with known crystallographic ones, thus determining the validity of IR-LD spectral conclusions as well as its possibility to determination of Davydov's splitting effect and separation of pairs of maxima corresponding to non-equivalent molecules included in the unit cell of given compound. The experimental structural and spectroscopic data in our case are supported with theoretical DFT ones, obtaining both the electronic structure and vibrational frequencies in gas phase. 相似文献
92.
Koleva BB Stoyanov S Kolev T Petkov I Spiteller M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(3):847-853
Structural and spectroscopic elucidation of merocyanine dye, 2,5-[1-metyl-4-[2-(4-hydroxyphenyl)ethenyl)]piridinium]-hexane tetraphenylborate, is performed in gas and condense phase by means of solution and solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids in nematic liquid crystal suspension, UV-vis and fluorescence methods, HPLC MS/MS tandem and ESI mass spectrometry, (1)H, (13)C and (1)H-(1)H COSY NMR, TGV and DSC methods. Quantum chemical DFT calculations are performed for structural optimization and spectroscopic properties prediction. 相似文献
93.
In the present work, the Coats-Redfern method was used to determine the kinetic parameters and the possible reaction mechanism
of the thermal degradation of ultra-high molecular mass polyethene and its composites with fiber monocrystals in static air
at three different heating rates − 6, 10 and 16 K min−1. The analysis of the results obtained showed that the thermal degradation process of pure ultra-high molecular mass polyethene
corresponded to a diffusion controlled reaction (three-dimentional diffusion, mechanism D3), while its composites with fiber monocrystals degraded by two concurrent mechanisms (diffusion one D3 and A1,F1 mechanism). The fiber monocrystals used increased the thermal stability of the composite materials obtained. The values of
the activation energy, frequency factor, the changes of entropy, enthalpy and Gibbs energy for the active complex of the composites
were calculated. 相似文献
94.
Simic-Milosevic V Meyer J Morgenstern K 《Physical chemistry chemical physics : PCCP》2008,10(14):1916-1920
The constitutional isomerisation of single dichlorobenzene molecules adsorbed on the surfaces of Ag(111) and Cu(111) between their meta- and para-isomers is induced and investigated by means of a low temperature scanning tunneling microscope. On both substrates similar isomerisation thresholds are found indicating that the excitation mechanism of this reaction does not depend significantly on the underlying substrate. The isomerisation threshold voltage of (170 +/- 7) meV most likely corresponds to excitation of a C-C stretch mode whose gas-phase energies we calculated ab initio to lie at 174 and 172 meV for meta- and para-isomers respectively. Though the reaction is found to be localized on the submolecular scale, it depends heavily on the second substituent both in terms of excitation energy and reaction outcome. 相似文献
95.
The detailed structural characterization of complex polymer architectures, like copolymers and polymer mixtures, by mass spectrometry
presents a challenge. Even though soft ionization analyses revolutionized the characterization of large molecules and provided
a means for determining the polymer’s molecular weight distribution, polydispersity, and end groups, full microstructure elucidation
and monomer sequencing by soft ionization alone is not possible. The combination of high-resolution Fourier transform mass
spectrometry (FTMS) and tandem mass spectrometry (MSn) provides a powerful analytical tool for addressing these challenges. This tool was used in our work to separate and identify
the products of polymerization between 12-hydroxystearic acid (HSA) and stearic acid (SA), to provide precise information
about the exact location of caprolactones on the Tris(2-hydroxyethyl)isocyanurate (THEIC) molecule, and to sequence a glycidyl
methacrylate/methyl methacrylate (GMA/MMA) copolymer. The results highlight the value of ultrahigh resolution and tandem mass
spectrometry for fine structural characterization and sequencing of polymers. 相似文献
96.
Sinan Faiad Dr. Quentin Laurent Dr. Alexander L. Prinzen Jathavan Asohan Dr. Daniel Saliba Dr. Violeta Toader Prof. Hanadi F. Sleiman 《Angewandte Chemie (International ed. in English)》2023,62(51):e202315768
Nucleic acid therapeutics (NATs), such as mRNA, small interfering RNA or antisense oligonucleotides are extremely efficient tools to modulate gene expression and tackle otherwise undruggable diseases. Spherical nucleic acids (SNAs) can efficiently deliver small NATs to cells while protecting their payload from nucleases, and have improved biodistribution and muted immune activation. Self-assembled SNAs have emerged as nanostructures made from a single DNA-polymer conjugate with similar favorable properties as well as small molecule encapsulation. However, because they maintain their structure by non-covalent interactions, they might suffer from disassembly in biologically relevant conditions, especially with regard to their interaction with serum proteins. Here, we report a systematic study of the factors that govern the fate of self-assembled SNAs. Varying the core chemistry and using stimuli-responsive disulfide crosslinking, we show that extracellular stability upon binding with serum proteins is important for recognition by membrane receptors, triggering cellular uptake. At the same time, intracellular dissociation is required for efficient therapeutic release. Disulfide-crosslinked SNAs combine these two properties and result in efficient and non-toxic unaided gene silencing therapeutics. We anticipate these investigations will help the translation of promising self-assembled structures towards in vivo gene silencing applications. 相似文献
97.
Ana‐Maria Acu Carmen Violeta Muraru Daniel Florin Sofonea Voichiţa Adriana Radu 《Mathematical Methods in the Applied Sciences》2016,39(18):5636-5650
In this paper, we will propose a Durrmeyer variant of q‐Bernstein–Schurer operators. A Bohman–Korovkin‐type approximation theorem of these operators is considered. The rate of convergence by using the first modulus of smoothness is computed. The statistical approximation of these operators is also studied. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
98.
Let E be a Banach space of functions on a locally compact Abeliangroup G satisfying certain conditions. It has been proved thatfor every bounded operator M on E commuting with translationsthere exists such that , where is a suitable subset of the group of the continuous morphismsfrom G into * and is a generalized Fourier transform of g defined on . 相似文献
99.
100.
Stepwise Strategy to Cyclometallated PtII Complexes with N‐Heterocyclic Carbene Ligands: A Luminescence Study on New β‐Diketonate Complexes
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Dr. Sara Fuertes Dr. Hector García Dr. Mariano Perálvarez Wim Hertog Dr. Josep Carreras Dr. Violeta Sicilia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1620-1631
The imidazolium salt 3‐methyl‐1‐(naphthalen‐2‐yl)‐1H‐imidazolium iodide ( 2 ) has been treated with silver(I) oxide and [{Pt(μ‐Cl)(η3‐2‐Me‐C3H4)}2] (η3‐2‐Me‐C3H4=η3‐2‐methylallyl) to give the intermediate N‐heterocyclic carbene complex [PtCl(η3‐2‐Me‐C3H4)(H$\widehat{CC}$ *‐κC*)] ( 3 ) (H$\widehat{CC}$ *‐κC*=3‐methyl‐1‐(naphthalen‐2‐yl)‐1H‐imidazol‐2‐ylidene). Compound 3 undergoes regiospecific cyclometallation at the naphthyl ring of the NHC ligand to give the five‐membered platinacycle compound [{Pt(μ‐Cl)($\widehat{CC}$ *)}2] ( 4 ). Chlorine abstraction from 4 with β‐diketonate Tl derivatives rendered the corresponding neutral compounds [Pt($\widehat{CC}$ *)(L‐O,O′)] {L=acac (HL=acetylacetone) 5 , phacac (HL=1,3‐diphenyl‐1,3‐propanedione) 6 , hfacac (HL=hexafluoroacetylacetone) 7 }. All of the compounds ( 3 – 7 ) were fully characterized by standard spectroscopic and analytical methods. X‐ray diffraction studies were performed on 5 – 7 , revealing short Pt?Pt and π–π interactions in the solid‐state structure. The influence of the R‐substituents of the β‐diketonate ligand on the photophysical properties and the use of the most efficient emitter, 5 , as phosphor converter has also been studied. 相似文献