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排序方式: 共有176条查询结果,搜索用时 15 毫秒
41.
Dr. Paolo Zardi Dr. Thierry Roisnel Dr. Rafael Gramage-Doria 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(2):627-634
Inspired by enzymes such as cytochrome P-450, the study of the reactivity of metalloporphyrins continues to attract major interest in the field of homogeneous catalysis. However, little is known about benefitting from the substrate-recognition properties of porphyrins containing additional, catalytically relevant active sites. Herein, such an approach is introduced by using supramolecular ligands derived from metalloporphyrins customized with rigid, palladium-coordinating nitrile groups. According to different studies (NMR and UV/Vis spectroscopy, XRD, control experiments), the supramolecular ligands are able to accommodate pyridine derivatives as substrates inside the porphyrin pocket while the reactivity occurs at the peripheral side. By simply tuning a remote metal center, different binding events result in different catalyst reactivity, and this enzyme-like feature leads to high degrees of substrate selectivity in representative palladium-catalyzed Suzuki–Miyaura reactions. 相似文献
42.
Vita Surzhko Thierry Roisnel Barbara Le Grel Philippe Le Grel Claudia Lalli Gilles Argouarch 《Tetrahedron letters》2017,58(13):1343-1347
A set of picolinohydrazides was prepared by reaction between hydrazines and either 2-picolinic acid or ethyl pyridine-2-carboxylate, and characterized. These molecules were evaluated as ligands in the zinc-catalyzed hydrosilylation of ketones. Thus, several aromatic and aliphatic ketones were successfully reduced by diethoxymethylsilane as the hydride source in the presence of a catalytic system made of diethylzinc combined in situ to the picolinohydrazides described herein. 相似文献
43.
Lassen PR Guy L Karame I Roisnel T Vanthuyne N Roussel C Cao X Lombardi R Crassous J Freedman TB Nafie LA 《Inorganic chemistry》2006,45(25):10230-10239
The infrared and vibrational circular dichroism (VCD) spectra of six chiral oxorhenium(V) complexes, bearing a hydrotris(1-pyrazolyl)borate (Tp) ligand, have been investigated. These complexes are promising candidates for observation of parity violation (symmetry breaking due to the weak nuclear force). New chiral oxorhenium complexes have been synthesized, namely, [TpReO(eta2-O(CH3)CH2CH2O-O,O)] (4a and 4b) diastereomers and [TpReO(eta2-N(CH3)CH2CH2O-N,O)] (5) and [TpReO(eta2-N(tBu)CH2CH2O-N,O)] (6) enantiomers. All compounds could be obtained in enantiomerically pure form by using either column chromatography or HPLC over chiral columns. VCD spectroscopy of these compounds and of [TpReO(eta2-N(CH3)CH(CH3)CH(Ph)O-N,O)] (2) and [TpReO(eta2-N(CH2)3CHCO2-N,O)] (3) (with chiral bidentate ligands derived, respectively, from ephedrine and proline) were studied. This allowed the absolute configuration determination of all compounds together with their conformational analysis, by comparing calculated and experimental spectra. This is the first VCD study of rhenium complexes which further demonstrates the applicability of VCD spectroscopy in determining the chirality of inorganic complexes. 相似文献
44.
A series of tris(2-aminoethylamine) (tren) capped iron(II) porphyrins has been synthesized and characterized and their affinities for dioxygen and carbon monoxide measured. The X-ray structure of the basic scaffold with nickel inserted in the porphyrin is also reported. All the ligands differ by the nature of the group(s) attached to the secondary amine functions of the cap. These various substitutions were introduced to probe if a hydrogen bond with these secondary amine groups acting as the donor could rationalize the high affinity of these myoglobin models. This work clearly indicates that the cage structure of the tren predominates over all the other appended groups with the exception of p-nitrophenol. 相似文献
45.
Two novel ternary intermediate phases, namely URuSi3−x (x=0.11) and U3Ru2Si7 were found in the Si-rich part of the U-Ru-Si phase diagram. Single crystal X-ray diffraction measurements, carried out at room temperature, indicated that URuSi3−x crystallizes in its own tetragonal type structure (space group P4/nmm, no. 129; unit cell parameters: a=12.108(1) Å and c=9.810(1) Å), being a derivative of the BaNiSn3-type structure. U3Ru2Si7 adopts in turn a disordered orthorhombic La3Co2Sn7-type structure (space group Cmmm, no. 65; unit cell parameters: a=4.063(1) Å, b=24.972(2) Å and c=4.072(1) Å). As revealed by magnetization, electrical resistivity and specific heat measurements, both compounds order magnetically at low temperatures. Namely URuSi3−x is a ferromagnet with TC=45 K, and U3Ru2Si7 shows ferrimagnetic behavior below TC=29 K. 相似文献
46.
47.
Mahé N Guillou O Daiguebonne C Gérault Y Caneschi A Sangregorio C Chane-Ching JY Car PE Roisnel T 《Inorganic chemistry》2005,44(22):7743-7750
The synthesis of hexanuclear lanthanide hydroxo complexes by controlled hydrolysis led to polymorphic compounds. The hexanuclear entities crystallize in four different ways that depend on the extent of their hydration. The four structures can be described as hexanuclear lanthanide entities with formula [Ln(6)(mu(6)-O)(mu(3)-OH)(8)(NO(3))(6)(H(2)O)(12)](2+). Two additional NO(3)(-) ions intercalate between the hexanuclear entities in order to ensure the electroneutrality of the crystal structure. Some crystallization water molecules fill the intermolecular space. The three first families of compounds (1-3) exhibit crystal structures that have previously been reported. The fourth family of compounds (4) is described here for the first time. Its chemical formula is [Ln(6)(mu(6)-O)(mu(3)-OH)(8)(NO(3))(6)(H(2)O)(12)](NO(3))(2).2H(2)O (Ln = Gd, Er, and Y). In this paper, the chemical and thermal stabilities of the hexanuclear lanthanide compounds are reported together with the magnetic properties of the Gd(III)-containing species. To use these entities as precursors for new materials, the substitution of the nitrato groups by chloride ions has been studied. Two byproduct compounds have so been obtained: The first (compound 5) is a nitrato/chloride hexanuclear compound of chemical formula [Er(6)(mu(6)-O)(mu(3)-OH)(8)(NO(3))(6)(H(2)O)(12)](NO(3))Cl.2H(2)O. The second one (compound 6) is a polymeric compound in which the hexanuclear entities are linked by an unexpected and original N(2)O(4) bridge. Its chemical formula is [Er(6)(mu(6)-O)(mu(3)-OH)(8)(NO(3))(4)(H(2)O)(11)(OH)(ONONO(2))]Cl(3).2H(2)O. Its crystal structure can be described as the juxtaposition of chainlike molecular motifs. To the best of our knowledge, this is the first example of a coordination polymer synthesized from an isolated polylanthanide hydroxo complex. 相似文献
48.
Bellara Nedjar Maamar Hamdi Jacques Pri Valentin Hrault 《Journal of heterocyclic chemistry》1978,15(7):1153-1158
The multistep catalytic reduction of 6-methyl-4-hydroxy-2-pyrone allows isolation of two intermediate compounds: the biologically active parasorbic acid ( 5 ) and the 6-methyl-5,6-dihydro-4-hydroxy-2-pyrone ( 2 ). The desmotropic keto-enol equilibrium lies on the enol side, with the 4rhydroxy structure. Primary arylamines readily react with 2 , leading to corresponding 2-pyridones 8 ; with methylamine, the aliphatic intermediate 7 resulting from ring attack at the 2 position can be isolated. Also further functionnalization of both dihydropyrone and 2-pyridone is possible by selective bromination at position 3. 相似文献
49.
Assia Djeghri Fadila Balegroune Achoura Guehria-Laidoudi Thierry Roisnel 《Journal of chemical crystallography》2007,37(2):97-101
The title compound [Cu2(OOC-(CH2)6-COO)2] was synthesized and its crystal structure has been determined by single crystal X-ray diffraction methods. The complex crystallizes
in the triclinic space group P-1 with a=5.1077(5) ?, b=8.362(2) ?, c=11.378(2) ?, α=93.773(6)°, β=97.587(9)°, γ=90.493(’9)°
and D
cal=1.629 mg/m3 for Z=1.
The structure is polymeric and consists of discrete anhydrous centrosymmetric binuclear units [Cu2(OOC-(CH2)6-COO)2]. The two copper(II) centres bridged by the suberate groups in a syn-syn conformation, are in pentacoordinated distorted
square-pyramidal coordination environment, with an intramolecular Cu–Cu distance of 2.5793(10) ?. Each binuclear unit, related
to the next through μoxo bridges with a Cuμoxo–Cuμoxo separation of 3.2326(10)?, defines infinite chains of one-edge sharing CuO5 square pyramid. 相似文献
50.
Crystals of aza-beta3-peptides have been obtained. This gives the first opportunity for hydrazino peptides, in the sense of oligomers built exclusively with alpha-hydrazinoacetic units, to be observed in the solid state. The structures make it clear that the H-bond network developed by aza-beta3-peptides differs radically from those of the corresponding beta3-peptides but strongly resembles that of the alpha-aminoxy peptides. Our study contributes to the current interest in hydrazino peptides as an extension of the beta-peptide concept. 相似文献