首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   160篇
  免费   0篇
化学   116篇
晶体学   43篇
物理学   1篇
  2023年   1篇
  2022年   1篇
  2013年   3篇
  2012年   3篇
  2011年   3篇
  2010年   2篇
  2009年   6篇
  2008年   5篇
  2007年   5篇
  2006年   12篇
  2005年   8篇
  2004年   9篇
  2003年   2篇
  2002年   3篇
  2001年   2篇
  2000年   1篇
  1999年   7篇
  1998年   3篇
  1995年   5篇
  1994年   2篇
  1993年   3篇
  1992年   7篇
  1991年   2篇
  1990年   10篇
  1989年   8篇
  1988年   6篇
  1987年   6篇
  1986年   5篇
  1985年   3篇
  1984年   14篇
  1983年   7篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
排序方式: 共有160条查询结果,搜索用时 818 毫秒
81.
The crystal structures of (μ-4,4-bipyridine)-di(nitrato-1-[(2-hydroxyethylimino)methyl]naphthalen-2-olocopper (I) and catena-di(μ-4,4’-bipyridine)di(μ-4,4’-bipyridine)-di(nitrato-2-[2-(hydroxyethylimino) methyl]phenolocopper)diaquacopper(II) nitrate (II) were determined. In the crystal of I, each of the two copper atoms coordinates a singly deprotonated tridentate azomethine molecule, a nitrate ion, and bipyridine, which functions as a bridge between the central atoms. The copper coordination polyhedron is a slightly distorted tetragonal pyramid with the base formed by the imine and bipyridine nitrogen atoms and the phenol and alcohol oxygen atoms. The axial site in the pyramid is occupied by the oxygen atom of the monodentate nitrate groups. In the trinuclear structure II with C2 crystal chemical symmetry, the terminal coordination unit is composed through copper coordination of monodeprotonated 2-[2-(hydroxyethylimino)methyl]phenol, bipyridine, and the nitrate anion. In the crystal, the trinuclear molecules form infinite ribbons along the z axis in which the pyridine molecules perform the bridging function. The central copper atom has an octahedral configuration formed by the nitrogen atoms of four 4,4’-bipyridine molecules and oxygen of two water molecules.  相似文献   
82.
Mixed crystals of ammonium dihydrogen phosphate and potassium dihydrogen phosphate K1‐x(NH4)x H2PO4 were grown from aqueous solutions with x = 0.06, 0.09, 0.15, 0.32, 0.42, 0.51, 0.63, 0.70, 0.76, 0.78, 0.84, 0.88, 0.89 and 0.91. The crystal composition that differs from solution was estimated by X‐ray method. Morphology of the crystals changes from tetragonal prism to needles when the incorporation of either of the two components into the other; which also affects the growth rate along the prominent growth directions significantly. Growth along the [001] decreases initially with composition and reached the maximum when x = 0.5; whereas growth along the [100] always showed a decreasing trend with composition and attained a minimum value when x = 0.5. Crystal length along the [001] and [100] and aspect ratio are also compositional dependent. Unit cell parameters determined by X‐ray powder and single crystal analyses revealed that the ‘a ’ parameter shows only a small and linear variation but the ‘c ’ parameter changes significantly with ADP incorporation because of the difference in the effective ionic radius of K+ and NH4+ ions and also the possibility of NH4+ ion to form two different kinds of hydrogen bonds in the system. The existence of a pseudo‐cubic cell at the mixing composition x = 0.78 was also revealed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
83.
84.
85.
Catalytic one-pot reactions of aromatic iodides with alkyl halides, phenylacetylene or diphenylacetylene, potassium acetate or carbonate, norbornene and palladium acetate in DMF or DMA are reported. A high selectivity towards dialkylsubstituted diarylacetylenes and diarylalkylidenehexahydromethanofluorenes, respectively, has been reached.  相似文献   
86.
87.
88.
89.
The crystal structures of chloro-(2-formylpyridinethiosemicarbazono)copper dimethyl sulfoxide solvate (I), bromo-(2-formylpyridinethiosemicarbazono)copper (II), and (2-formylpyridinethiosemicarbazono)copper(II) nitrate dimethyl sulfoxide solvate (III) are determined using X-ray diffraction. In the crystals, complexes I and II form centrosymmetric dimers in which the thiosemicarbazone sulfur atom serves as a bridge and occupies the fifth coordination site of the copper atom of the neighboring complex related to the initial complex through the center of symmetry. In both cases, the coordination polyhedron of the complexing ion is a distorted tetragonal bipyramid. Complex III in the crystal structure forms polymer chains in which the copper atom of one complex forms the coordination bond with the thicarbamide nitrogen atom of the neighboring complex. In this structure, the coordination polyhedron of the central atom is an elongated tetragonal bipyramid. It is established that complexes I–III at a concentration of 10?5 mol/l selectively inhibit the growth of 60 to 90 percent of the cancer tumor cells of the human myeloid leukemia (HL-60).  相似文献   
90.
Mol­ecules of the title compounds, C15H14N2O4S·H2O and C15H13BrN2O4S·H2O, adopt an E configuration about the azomethine C=N double bond. In both mol­ecules, the two benzene rings and the azomethine group are practically coplanar, as a result of intra­molecular hydrogen bonds involving the hydroxy O atom and azomethine N atom. The angular disposition of the bonds about the S atom deviates significantly from that of a regular tetra­hedron. In the crystal structures, both compounds form two‐dimensional layers parallel to the (100) plane.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号