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Anhydrous orthoborates RM3(BO3)4, where R = Y, La–Lu, M = Al, Ga, Cr, Fe, with huntite structure type are considered as multifunctional laser materials. The crystal structure of these borates is either rhombohedral with space group R32 (D37) (Z = 3) or monoclinic with space group C2/c (C2h6) (Z = 4) depending on the growth conditions. Both modifications have very close polytypic structures, and it is difficult to identify them by powder diffraction data. In this context, double borates of rare-earth cations and Cr3+ have been grown from high-temperature solutions and are characterized by Raman and infrared spectroscopy in a crystalline state in combination with factor group analysis of vibrational modes. The assignment for the stretching and bending vibrations of BO33− groups and external modes has been made. Some external modes have been identified by study of mass effect (Al–Cr, La–Ho). Comparison of the Raman spectra of these borates shows redistribution of band intensities of two spectral modifications, related to different symmetry groups. As predicted by factor group analysis, the number of IR-active vibrational modes of stretching and bending vibrations of BO33− units significantly increases in infrared spectra of monoclinic borates in comparison with rhombohedral ones. The dependence of the realized borate space group on the crystal growth conditions and the sort of rare-earth atom was revealed. Both GdCr3(BO3)4 and EuCr3(BO3)4 borates crystallize in space group R32 irrespective of growth conditions. The borates with the large rare-earth elements La–Nd always form the monoclinic structures, irrespective of crystallization temperature. The borates SmCr3(BO3)4, TbCr3(BO3)4 and DyCr3(BO3)4 have been obtained in two modifications in dependence of crystalline borate substance/solvent ratio and related temperature of crystallization. 相似文献
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Dr. Anna Pakhomova Birgit Fuchs Prof. Dr. Leonid S. Dubrovinsky Prof. Dr. Natalia Dubrovinskaia Prof. Dr. Hubert Huppertz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(19):6007-6014
Based on the results from previous high-pressure experiments on the gadolinite-type mineral datolite, CaBSiO4(OH), the behavior of the isostructural borates β-HfB2O5 and β-ZrB2O5 have been studied by synchrotron-based in situ high-pressure single-crystal X-ray diffraction experiments. On compression to 120 GPa, both borate layer-structures are preserved. Additionally, at ≈114 GPa, the formation of a second phase can be observed in both compounds. The new high-pressure modification γ-ZrB2O5 features a rearrangement of the corner-sharing BO4 tetrahedra, while still maintaining the four- and eight-membered rings. The new phase γ-HfB2O5 contains ten-membered rings including the rare structural motif of edge-sharing BO4 tetrahedra with exceptionally short B−O and B⋅⋅⋅B distances. For both structures, unusually high coordination numbers are found for the transition metal cations, with ninefold coordinated Hf4+, and tenfold coordinated Zr4+, respectively. These findings remarkably show the potential of cold compression as a low-energy pathway to discover metastable structures that exhibit new coordinations and structural motifs. 相似文献
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HP‐CsB5O8: Synthesis and Characterization of an Outstanding Borate Exhibiting the Simultaneous Linkage of All Structural Units of Borates 下载免费PDF全文
Gerhard Sohr Daniel M. Többens Prof. Dr. Jörn Schmedt auf der Günne Prof. Dr. Hubert Huppertz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):17059-17067
The new cesium pentaborate HP‐CsB5O8 is synthesized under high‐pressure/high‐temperature conditions of 6 GPa and 900 °C in a Walker‐type multianvil apparatus. The compound crystallizes in the orthorhombic space group Pnma (Z=4) with the parameters a=789.7(1), b=961.2(1), c=836.3(1) pm, V=0.6348(1) nm3, R1=0.0359 and wR2=0.0440 (all data). The new structure type of HP‐CsB5O8 exhibits the simultaneous linkage of trigonal BO3 groups, corner‐sharing BO4 tetrahedra, and edge‐sharing BO4 tetrahedra including the presence of threefold‐coordinated oxygen atoms. With respect to the rich structural chemistry of borates, HP‐CsB5O8 is the second structure type possessing this outstanding combination of the main structural units of borates in one compound. The structure consists of corrugated chains of corner‐ and edge‐sharing BO4 tetrahedra interconnected through BO3 groups forming octagonal channels. Inside these channels, cesium is 13+3‐fold coordinated by oxygen atoms. 11B MQMAS NMR spectra are analyzed to estimate the isotropic chemical shift values and quadrupolar parameters. IR and Raman spectra are obtained and compared to the calculated vibrational frequencies at the Γ‐point. The high‐temperature behavior is examined by means of temperature‐programmed powder diffraction. 相似文献
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Dr. Qi Wei Jia‐Jia Wang Dr. Chao He Prof. Dr. Jian‐Wen Cheng Prof. Dr. Guo‐Yu Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10759-10762
A new borate LiBa3(OH)[B9O16][B(OH)4], which combines the uniform porosity of open‐frameworks with the extraordinary NLO properties of borates, has been obtained under hydrothermal conditions by using mixed lithium and barium ions as templates. The framework displays an acs‐type net with large 21‐ring channels. The second harmonic generation (SHG) measurement shows that it is a type I phase‐matchable material with a strong SHG signal intensity about 3.1 times that of KDP (KH2PO4). UV/Vis–NIR diffuse reflectance analysis indicates that the compound has a wide transparency range with the short‐wavelength absorption edge below 200 nm. These characteristics reveal that the compound is a promising deep‐UV nonlinear optical material. 相似文献
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Jian Zhou Dr. Wei‐Hui Fang Cheng Rong Dr. Guo‐Yu Yang Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(16):4852-4863
A series of open‐framework aluminoborates (ABOs) [M(dien)2][AlB6O11(OH)] (M=Co ( I a ), Ni ( I b ), Cd ( I c ), Zn ( I d ); dien=diethylenetriamine) and [M(en)3][AlB7O12(OH)2] ? (H2O)0.25 (M=Co ( II a ), Ni ( II b ); en=ethylenediamine) have been made under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, UV/Vis and fluorescence spectroscopy, powder X‐ray diffraction, single‐crystal X‐ray diffraction, and nonlinear optical determination. These compounds were classified as two structural types: Type I ( I a – d ) contains AlO4 tetrahedra and B6O11(OH) clusters, which link to form a new 3D framework with 7‐/9‐ring helical channels and large 13‐ring channels; whereas type II ( II a , b ) is composed of AlO4 tetrahedra, chainlike B4O6(OH)2 tetramer, and crablike B6O12 clusters, which interconnect to form other new 3D frameworks with 8‐ring helical channels, rare 16‐ring double‐helical channels, and larger odd 15‐ring channels. These compounds represent the first examples of 3D ABOs templated by transition‐metal complexes (TMCs). I c , d present good second harmonic generation (SHG) properties. UV/Vis spectral investigation indicates that I a – d and II a , b are wide‐band‐gap semiconductors. 相似文献