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31.
Wang X Guo Y Shi Y Belik AA Tsujimoto Y Yi W Sun Y Shirako Y Arai M Akaogi M Matsushita Y Yamaura K 《Inorganic chemistry》2012,51(12):6868-6875
The postspinel mineral MgAl(2)O(4) exists only under the severe pressure conditions in the subducted oceanic lithosphere in the Earth's deep interior. Here we report that its analogous oxide CdRh(2)O(4) exhibits a structural transition to a quenchable postspinel phase under a high pressure of 6 GPa at 1400 °C, which is within the general pressure range of a conventional single-stage multianvil system. In addition, the complex magnetic contributions to the lattice and metal nonstoichiometry that often complicate investigations of other analogues of MgAl(2)O(4) are absent in CdRh(2)O(4). X-ray crystallography revealed that this postspinel phase has an orthorhombic CaFe(2)O(4) structure, thus making it a practical analogue for investigations into the geophysical role of postspinel MgAl(2)O(4). Replacement of Mg(2+) with Cd(2+) appears to be effective in lowering the pressure required for transition, as was suggested for CdGeO(3). In addition, Rh(3+) could also contribute to this reduction, as many analogous Rh oxides of aluminous and silicic minerals have been quenched from lower-pressure conditions. 相似文献
32.
Gerd-Volker Röschenthaler Valery P. Kukhar Irine B. Kulik Michael Yu. Belik Alexander E. Sorochinsky Eduard B. Rusanov Vadim A. Soloshonok 《Tetrahedron letters》2012,53(5):539-542
Addition of dialkyl phosphites to (S)-N-tert-butanesulfinyl imine derived from fluoral afforded, under mild conditions, the corresponding N-tert-butanesulfinyl α-aminophosphonates in moderate to high yields and diastereoselectivity. The major diastereomers of N-tert-butanesulfinyl α-aminophosphonates of (SS,S) configuration were isolated, and after partial or complete deprotection, converted into enantiomerically pure phosphonotrifluoroalanine and its dialkyl esters. 相似文献
33.
BiPd(2)O(4) and PbPd(2)O(4) were synthesized at high pressure of 6 GPa and 1500 K. Crystal structures of BiPd(2)O(4) and PbPd(2)O(4) were studied with synchrotron X-ray powder diffraction. BiPd(2)O(4) is isostructural with PbPt(2)O(4) and crystallizes in a triclinic system (space group P1, a = 5.73632(4) ?, b = 6.02532(5) ?, c = 6.41100(5) ?, α = 114.371(1)°, β = 95.910(1)°, and γ = 111.540(1)° at 293 K). PbPd(2)O(4) is isostructural with LaPd(2)O(4) and BaAu(2)O(4) and crystallizes in a tetragonal system (space group I4(1)/a, a = 5.76232(1) ?, and c = 9.98347(2) ? at 293 K). BiPd(2)O(4) shows ordering of Pd(2+) and Pd(4+) ions, and it is the third example of compounds with ordered arrangements of Pd(2+) and Pd(4+) in addition to Ba(2)Hg(3)Pd(7)O(14) and KPd(2)O(3). In PbPd(2)O(4), the following charge distribution is realized Pb(4+)Pd(2+)(2)O(4). PbPd(2)O(4) shows a structural phase transition from I4(1)/a to I2/a at about 240 K keeping basically the same structural arrangements (space group I2/a, a = 5.77326(1) ?, b = 9.95633(2) ?, c = 5.73264(1) ?, β = 90.2185(2)° at 112 K). BiPd(2)O(4) is nonmagnetic while PbPd(2)O(4) exhibits a significant temperature-dependent paramagnetic moment of 0.46μ(B)/f.u. between 2 and 350 K. PbPd(2)O(4) shows metallic conductivity, and BiPd(2)O(4) is a semiconductor between 2 and 400 K. 相似文献
34.
A method of evaluating a degree of molecular symmetry is suggested. The symmetry criteria calculated by this technique are useful for predicting phase transition temperatures in mesogen compounds. Methods of evaluating chirality avoiding molecular representation as a set of simplices are proposed. The efficiency of these methods is verified on model structures belonging to different symmetry groups. The new approach may be used to analyze stereochemical relationships between atoms in a molecule. 相似文献
35.
36.
A. Yu. Belik V. I. Kukushkin A. Yu. Rybkin N. S. Goryachev P. A. Mikhailov V. S. Romanova O. A. Kraevaya P. A. Troshin A. I. Kotelnikov 《Doklady Physical Chemistry》2018,481(1):95-99
Free fluorescence spectra in solution and surface-enhanced Raman scattering (SERS) and surface enhanced fluorescence (SEF) spectra of chlorin e6 and water-soluble covalent fullerene–chlorin dyads have been studied. It has been demonstrated that chlorin e6 and covalent fullerene–chlorin dyads have similar characteristic SERS spectra. The fullerene–chlorin dyads show a pronounced SEF signal, while native chlorin e6 has no fluorescence on surface, which is consistent with the theory predicting an inverse dependence of the SEF intensity on the free fluorescence quantum yield. The concentration dependence of the SEF intensity is linear for the dyads in the range 0.1–2.0 μmol/L. These effects allow one to determine, with high sensitivity, the content of fullerene–chlorin dyads with a low quantum yield of free fluorescence in solutions, which opens wide opportunities for study of biological properties of fullerene–chlorin dyads and their applications in medicine. 相似文献
37.
Alexei A. Belik Artem P. Malakho Bogdan I. Lazoryak 《Journal of solid state chemistry》2006,179(1):161-168
Solid solutions of Sr9+xCo1.5−x(PO4)7 were found in the compositional range of 0.05?x?0.30. The structure of Sr9.2Co1.3(PO4)7 (x=0.2) was determined from single crystal X-ray diffraction (space group (No. 166); Z=3; and ; ; ; ) and refined to R1=0.0343 and wR2=0.0633 for 586 reflections with I>2σ(I). Sr9.2Co1.3(PO4)7 is structurally related to β-Ca3(PO4)2 and Sr3(PO4)2 and has disordered arrangements of some Sr2+, Co2+, and PO43− ions. Sr2+ ions at a 9e site are statistically disordered among four positions near the center of symmetry. Co2+ and Sr2+ ions are split along the c-axis to occupy a 6c site that is 75% vacant. The P1O4 tetrahedra are orientationally disordered. Sr2+ ions at an 8-fold coordinated 18h site, Co2+ ions at an octahedral 3a site, and the P2O4 tetrahedra are ordered in the structure of Sr9.2Co1.3(PO4)7. Features of Raman spectra are discussed in relation to the crystallographic structure of Sr9.2Co1.3(PO4)7 and in comparison with Raman spectra of β-Ca3(PO4)2-type and Sr3(PO4)2-type compounds. Sr9.2Co1.3(PO4)7 is paramagnetic between 2 and 300 K with an effective magnetic moment of 4.98μB per Co2+ ion. 相似文献
38.
39.
Sorochinsky A Voloshin N Markovsky A Belik M Yasuda N Uekusa H Ono T Berbasov DO Soloshonok VA 《The Journal of organic chemistry》2003,68(19):7448-7454
The enantiopure Davis' N-sulfinylimines were found to be efficient as chiral imine equivalents in the high-temperature Reformatsky-type additions with BrZnCF(2)COOEt affording an efficient approach to the enantiomerically pure alpha,alpha-difluoro-beta-amino acids. High chemical and stereochemical yields (drs > 9:1, and as high as 99:1) render this method immediately useful for preparing the target amino acids. 相似文献
40.
A new model based on certain physical concepts of interatomic interactions is proposed for simulating the volume characteristics
of molecules that allow reliable estimations of the densities of substances and solutions. The model is used to calculate
the solution densities for six substances within wide concentration ranges.
Chelyabinsk State University. Translated fromZhurmal Strukturnoi Khimii, Vol. 36, No. 5, pp. 823–827, September–October, 1995.
Translated by I. Izvekova 相似文献