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The effect of different donor nitrogen atoms on the strength and nature of intramolecular Se ??? N interactions is evaluated for organoselenium compounds having N,N‐dimethylaminomethyl (dime), oxazoline (oxa) and pyridyl (py) substituents. Quantum chemical calculations on three series of compounds [2‐(dime)C6H4SeX ( 1 a – g ), 2‐(oxa)C6H4SeX ( 2 a – g ), 2‐(py)C6H4SeX ( 3 a – g ); X=Cl, Br, OH, CN, SPh, SePh, CH3] at the B3LYP/6‐31G(d) level show that the stability of different conformers depends on the strength of intramolecular nonbonded Se ??? N interactions. Natural bond orbital (NBO), NBO deletion and atoms in molecules (AIM) analyses suggest that the nature of the Se ??? N interaction is predominantly covalent and involves nN→σ*Se? X orbital interaction. In the three series of compounds, the strength of the Se ??? N interaction decreases in the order 3 > 2 > 1 for a particular X, and it decreases in the order Cl>Br>OH>SPh≈CN≈SePh>CH3 for all the three series 1 – 3 . However, further analyses suggest that the differences in strength of Se ??? N interaction in 1 – 3 is predominantly determined by the distance between the Se and N atoms, which in turn is an outcome of specific structures of 1 , 2 and 3 , and the nature of the donor nitrogen atoms involved has very little effect on the strength of Se ??? N interaction. It is also observed that Se ??? N interaction becomes stronger in polar solvents such as CHCl3, as indicated by the shorter rSe ??? N and higher ESe ??? N values in CHCl3 compared to those observed in the gas phase. 相似文献
43.
Highly important trans-3,4-dihydro-2H-1,4-benzoxazine moieties were easily synthesized by domino aziridine ring opening with o-bromophenols and o-chlorophenols followed by the palladium catalyzed coupling-cyclization (intramolecular C(aryl)–N(amide) bond formation) with good to excellent yields. 相似文献
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Selective Endo and Exo Binding of Mono‐ and Ditopic Ligands to a Rhomboidal Diporphyrin Prism 下载免费PDF全文
Dr. Govindasamy Jayamurugan Derrick A. Roberts Dr. Tanya K. Ronson Prof. Jonathan R. Nitschke 《Angewandte Chemie (International ed. in English)》2015,54(26):7539-7543
Copper(I) can preferentially form heteroleptic complexes containing two phosphine and two nitrogen donors due to steric factors. This preference was employed to direct the self‐assembly of a porphyrin‐faced rhomboidal prism having two parallel tetrakis(4‐iminopyridyl)porphyrinatozinc(II) faces linked by eight 1,4‐bis(diphenylphosphino)benzene pillars. The coordination preferences of the CuI ions and geometries of the ligands come together to generate a slipped‐cofacial orientation of the porphyrinatozinc(II) faces. This orientation enables selective encapsulation of 3,3′‐bipyridine (bipy), which bridges the ZnII ions of the parallel porphyrins, whereas 4,4′‐bipy exhibits weaker external coordination to the porphyrin faces. Reaction with 2,2′‐bipy, by contrast, results in the displacement of the tetratopic porphyrin ligand and formation of [{(2,2′‐bipy)CuI}2(diphosphine)2]. The differing strengths of interactions of bipyridine isomers with the system allows for a hierarchy to be deciphered, whereby 4,4′‐bipy may be displaced by 3,3′‐bipy, which in turn is displaced by 2,2′‐bipy. 相似文献
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Bis(N‐(pyrrol‐2‐ylmethyl)‐N‐butyldithiocarbamato‐S,S′)copper(II) ( 1 ), bis(N‐(pyrrol‐2‐ylmethyl)‐N‐(2‐phenylethyl)dithiocarbamato‐S,S′)copper(II) ( 2 ), bis(N‐methylferrocenyl‐N‐(2‐phenylethyl)dithiocarbamato‐S,S′)copper(II) ( 3 ) and bis(N‐furfuryl‐N‐methylferrocenyldithiocarbamato‐S,S′)copper(II) ( 4 ) were prepared and characterized using elemental analysis and infrared and UV–visible spectroscopies. X‐ray diffraction (XRD) studies on 3 show that each copper centre adopts the square planar geometry by the coordination of four sulfur atoms of the metalloligand N‐methylferrocenyl‐N‐(2‐phenylethyl)dithiocarbamate. The Cu? S distances are symmetrical and are in the range 2.293–2.305 Å. The supramolecular architecture in complex 3 is sustained in the solid state by C? H???π, C? H???S, Fe???Fe and H???H interactions. Density functional theory calculations were carried out for 3 . Anion (F?, Cl?, Br? and I?) binding studies with complex 1 were performed using cyclic voltammetry. Copper sulfide, copper–iron sulfide‐ 1 and copper–iron sulfide‐ 2 nanoparticles were prepared from complexes 2 , 3 and 4 , respectively, and they were characterized using powder XRD, transmission electron microscopy (TEM) and energy‐dispersive X‐ray, UV–visible, photoluminescence and infrared spectroscopies. TEM images of copper–iron sulfide‐ 1 and copper–iron sulfide‐ 2 reveal that the particles are spherical and oval shaped, respectively. Photocatalytic activities of as‐prepared nanoparticles were studied by decolourization of methylene blue and rhodamine‐B under UV light. It was found that copper–iron sulfide degrades methylene blue and rhodamine‐B much better than does copper sulfide. 相似文献
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Arockiam Anthonysamy Sengottuvelan Balasubramanian Govindasamy Usha Devadasan Velmurugan 《Transition Metal Chemistry》2008,33(6):681-690
The free Schiff bases H2MABCE, H2MABCP, and H2MABCT and their complexes [Ni(MABCE)], [Ni(MABCP)], [Ni(MABCT)], [Cu(MABCE)], [Cu(MABCP)], and [Cu(MABCT)] have been synthesized and characterized by spectroscopic, cyclic voltammetric, and thermal studies. The geometry around nickel is square planar with N2O2 donor atoms. Cyclic voltammetric studies of the Ni(II) complexes show one-electron quasi-reversible waves corresponding to Ni(II)/Ni(I) and Ni(II)/Ni(III) processes. The Cu(II) complexes exhibit an irreversible well defined one electron transfer reduction peak in the range of ?0.34 to ?1.08 V. The electronic spectra of the complexes suggest a four-coordinate geometry. The crystal structure of the ligand H2MABCT and the complex [Ni(MABCP)] have also been reported. The mean Ni–N and Ni–O bond distances are Ni–N = 1.849(4) and Ni–O = 1.837(4) Å. 相似文献
50.
A revised mechanism that accounts for the glutathione peroxidase (GPx)-like catalytic activity of the organoselenium compound ebselen is described. It is shown that the reaction of ebselen with H(2)O(2) yields seleninic acid as the only oxidized product. The X-ray crystal structure of the seleninic acid shows that the selenium atom is involved in a noncovalent interaction with the carbonyl oxygen atom. In the presence of excess thiol, the Se--N bond in ebselen is readily cleaved by the thiol to produce the corresponding selenenyl sulfide. The selenenyl sulfide thus produced undergoes a disproportionation in the presence of H(2)O(2) to produce the diselenide, which upon reaction with H(2)O(2), produces a mixture of selenenic and seleninic acids. The addition of thiol to the mixture containing selenenic and seleninic acids leads to the formation of the selenenyl sulfide. When the concentration of the thiol is relatively low in the reaction mixture, the selenenic acid undergoes a rapid cyclization to produce ebselen. The seleninic acid, on the other hand, reacts with the diselenide to produce ebselen as the final product. DFT calculations show that the cyclization of selenenic acids to the corresponding selenenyl amides is more favored than that of sulfenic acids to the corresponding sulfenyl amides. This indicates that the regeneration of ebselen under a variety of conditions protects the selenium moiety from irreversible inactivation, which may be responsible for the biological activities of ebselen. 相似文献