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81.
Kamyabi Mohammad Ali Hashemi Heris Mir Karim Jadali Salma 《Journal of Solid State Electrochemistry》2021,25(4):1283-1292
Journal of Solid State Electrochemistry - In this work, a polymer composite based on poly 4-aminothiophenol (p-ATP) is prepared via a facile electrochemical route and is used as an appropriate... 相似文献
82.
Dr. Baptiste Joalland Nuwandi M. Ariyasingha Hassan R. Younes Shiraz Nantogma Dr. Oleg G. Salnikov Dr. Nikita V. Chukanov Dr. Kirill V. Kovtunov Prof. Igor V. Koptyug Prof. Juri G. Gelovani Prof. Eduard Y. Chekmenev 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2774-2781
Many MRI contrast agents formed with the parahydrogen-induced polarization (PHIP) technique exhibit biocompatible profiles. In the context of respiratory imaging with inhalable molecular contrast agents, the development of nonflammable contrast agents would nonetheless be highly beneficial for the biomedical translation of this sensitive, high-throughput and affordable hyperpolarization technique. To this end, we assess the hydrogenation kinetics, the polarization levels and the lifetimes of PHIP hyperpolarized products (acids, ethers and esters) at various degrees of fluorine substitution. The results highlight important trends as a function of molecular structure that are instrumental for the design of new, safe contrast agents for in vivo imaging applications of the PHIP technique, with an emphasis on the highly volatile group of ethers used as inhalable anesthetics. 相似文献
83.
Two fluorescent heteroditopic ligands (2a and 2b) for zinc ion were synthesized and studied. The efficiencies of two photophysical processes, intramolecular charge transfer (ICT) and photoinduced electron transfer (PET), determine the magnitudes of emission bathochromic shift and enhancement, respectively, when a heteroditopic ligand forms mono- or dizinc complexes. The electron-rich 2b is characterized by a high degree of ICT in the excited state with little propensity for PET, which is manifested in a large bathochromic shift of emission upon Zn(2+) coordination without enhancement in fluorescence quantum yield. The electron-poor 2a displays the opposite photophysical consequence where Zn(2+) binding results in greatly enhanced emission without significant spectral shift. The electronic structural effects on the relative efficiencies of ICT and PET in 2a and 2b as well as the impact of Zn(2+)-coordination are probed using experimental and computational approaches. This study reveals that the delicate balance between various photophysical pathways (e.g. ICT and PET) engineered in a heteroditopic ligand is sensitively dependent on the electronic structure of the ligand, i.e. whether the fluorophore is electron-rich or poor, whether it possesses a donor-acceptor type of structure, and where the metal binding occurs. 相似文献
84.
The adsorption of zwitterionic (E) 4-methoxy-4′-(3-n-sulfonatopropyl)stilbazolium (MSPS) molecules on the stepped vicinal Au(23 23 21) surface was studied by scanning tunneling microscopy (STM) at low temperature as a function of the molecular coverage. At the sub-half monolayer, a supramolecular network based on MSPS is preferentially adsorbed onto face-centered cubic stacking regions. At the monolayer, a complete periodic supramolecular film is obtained. 相似文献
85.
The Claisen-Schmidt condensation of 1-(triphenylmethyl)-2-imidazolecarboxaldehyde with acetophenones yielded 1-aryl-3-[1-(triphenylmethyl)-2-imidazolyl]propen-1-ones 7 . Selective catalytic hydrogenation over platinum of 7 furnished 1-aryl-3-(2-imidazolyl)-1-propanones 8 . An alternate synthesis of 8 started with sodium borohydride reduction of 7 to give allylic alcohols, 1-aryl-3-[1-(triphenylmethyl)-2-imidazolyl]-2-propen-1-ols 10 , which were rearranged by hot aqueous sodium to 8 . Acid hydrolysis of 8 provided the title compounds and triphenylmethanol. 相似文献
86.
Jang-Woo Kim Salma M. Abdelaal Ludwig Bauer Norman E. Heimer 《Journal of heterocyclic chemistry》1995,32(2):611-620
Lithiation of 1-(dimethylsulfamoyl)imidazole by n-butyllithium, followed by substitution with dimethylformamide provided 1-(dimethylsulfamoyl)-2-imidazolecarboxaldehyde in 19% yield. When 1-(dimethylsulfamoyl)-2-(tert-butyldimethylsilyl)imidazole was lithiated by sec-butyllithium, followed by methyl formate, there was obtained 1-(dimethylsulfamoyl)-2-(tert-butyldimethylsilyl)-5-imidazolecarbox-aldehyde (57%). Removal of the silyl group by acetic acid yielded 1-(dimethylsulfamoyl)-5-imidazolecarbxaldehyde ( 11 , 96%) as a gum. Isomerization of 11 took place slowly at room temperature (10 days), or faster in tetrahydrofuran solution containing triethylamine (2 hours) to form crystalline 1-(dimethylsul-famoyl)-4-imidazolecarboxaldehyde (12) in 68% yield. Proton and carbon-13 nmr spectra were analyzed to determine the structure of the isomers. However, only X-ray crystallography established the structure of 1-(dimethylsulfamoyl)-4-imidazolecarboxaldehyde, unequivocally. A mechanism for the isomerization of 11 to 12 is proposed. 相似文献
87.
A new class of tungstate fluorophosphate glasses was identified in the NaPO3-BaF2-WO3 ternary system. The variation of several physical properties was determined with respect to chemical composition. Characteristic temperatures, density and refractive index increase as tungsten oxide content increases. The optical transmission range and specially the energy bandgap depend of the WO3 amount. No crystallization could be observed for the most WO3 concentrated vitreous samples (?20% molar). Color and optical properties of the glasses depend of the melting time because of the presence of reduced tungsten species like W5+ and W4+. In addition, photodarkening is observed in tungsten rich glass samples under UV laser illumination and this phenomenon can be reversible by heat treatment near the glass transition temperature. 相似文献
88.
Younes Makoudi Eric Duverger Dr. Madjid Arab Dr. Frédéric Chérioux Dr. Franscisco Ample Dr. Gwénaël Rapenne Dr. Xavier Bouju Dr. Frank Palmino Dr. 《Chemphyschem》2008,9(10):1437-1441
This work describes an innovative concept for the development of organized molecular systems based on the template effect of the pre‐structured semi‐conductive SmSi(111) interface. This substrate is selected because Sm deposition in the submonolayer range leads to a 8×2‐reconstruction, which is a well‐defined one‐dimensional semi‐metallic structure. Adsorption of aromatic molecules [1,4‐di‐(9‐ethynyltriptycenyl)‐benzene] on SmSi(111)‐ 8×2 and Si(111)‐7×7 interfaces is investigated by scanning tunneling microscopy (STM) at room temperature. Density functional theory (DFT) and semi‐empirical (ASED+) calculations define the nature of the molecular adsorption sites of the target molecule on SmSi as well as their self‐alignment on this interface. Experimental data and theoretical results are in good agreement. 相似文献
89.
José Maurício A. Caiut Lucas A. Rocha Fernando A. Sigoli Younes Messaddeq Jeannette Dexpert-Ghys Sidney J.L. Ribeiro 《Journal of Non》2008,354(42-44):4795-4799
Boehmite–GPTS (GPTS-glycidoxypropyltrimethoxysilane) hybrids (BGS) have been prepared by the sol–gel methodology. Spectroscopic properties and structural features have been evaluated from the initial sols to xerogels as a function of composition. Eu3+-containing BGS samples were also prepared, and the Eu3+ 5D0 state emission quantum efficiency was observed to depend on the boehmite–siloxane interactions. Boehmite–siloxane heterocondensation was inferred from vibrational spectroscopy and 13C, 29Si, and 27Al nuclear magnetic resonance results. Unreacted epoxi groups could be identified in the final material being an important characteristic for the future applications. Good optical quality and mechanical properties lead to the preparation of thin films deposited on glass substrates by dip and spin-coating. Refractive index could be tuned by the relative boehmite and GPTS content. Waveguide properties have also been studied by m-lines spectroscopy and guided modes together with attenuation measurements suggest potential application of the prepared films in integrated optics. 相似文献
90.
Dias Filho FA Carlos LD Messadeq Y Ribeiro SJ 《Langmuir : the ACS journal of surfaces and colloids》2005,21(5):1776-1783
The interaction between metaphosphate chains and the metal ions Ca2+ and Eu3+ has been studied in water by Eu3+ luminescence, infrared absorption, and 31P NMR spectroscopy. Two main families of sites could be identified for the metal ions in the aqueous polyphosphate colloidal systems: (1) cagelike sites provided by the polyphosphate chain and (2) a family which arises following saturation of cagelike sites. Occupation of this second family leads to supramolecular interactions between polyphosphate chains and the consequent destabilization of the colloidal system. In the polyphosphate-Ca2+ system, this destabilization appears as a coacervation process. Equilibrium existing between colloidal species as a function of the compositions could be reasoned based on the spectroscopic measurements. The determination of coordination numbers and the correlation of the results with the observation of coacervates show that Eu3+ luminescence properties can be used to probe in a unique way the coacervation process. 相似文献