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101.
Yurina Díaz Jairo Quiroga Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(3):o137-o140
The molecules of the title compound, C26H19Cl2N5, are conformationally chiral, with none of the aryl groups coplanar with the pyrazolo[3,4‐b]pyridine core of the molecule. A single unique N—H...N hydrogen bond links the molecules into two symmetry‐related sets of C(11) chains running parallel to the [011] and [01] directions, respectively, and these two sets of chains are linked into a continuous three‐dimensional framework structure by a single unique C—H...N hydrogen bond which forms a chain parallel to the [100] direction. 相似文献
102.
Lina M. Acosta Ali Bahsas Alirio Palma Justo Cobo Michael B. Hursthouse Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(3):o92-o96
4‐Hydroxy‐2‐vinyl‐2,3,4,5‐tetrahydro‐1‐benzazepine, C12H15NO, (I), and its 7‐fluoro and 7‐chloro analogues, namely 7‐fluoro‐4‐hydroxy‐2‐vinyl‐2,3,4,5‐tetrahydro‐1‐benzazepine, C12H14FNO, (II), and 7‐chloro‐4‐hydroxy‐2‐vinyl‐2,3,4,5‐tetrahydro‐1‐benzazepine, C12H14ClNO, (III), are isomorphous, but with variations in the unit‐cell dimensions which preclude in compound (III) one of the weaker intermolecular interactions found in compounds (I) and (II). Thus the compounds are not strictly isostructural in terms of the structurally significant intermolecular interactions, although the corresponding atomic coordinates are very similar. The azepine rings adopt chair conformations. The molecules are linked by a combination of N—H...O and O—H...N hydrogen bonds into chains of edge‐fused R33(10) rings, which in compounds (I) and (II) are further linked into sheets by a single C—H...π(arene) hydrogen bond. The significance of this study lies in its observation of isomorphism in compounds (I)–(III), and its observation of a sufficient variation in one of the cell dimensions effectively to alter the range of significant hydrogen bonds present in the crystal structures. 相似文献
103.
104.
Janet M. S. Skakle James L. Wardell John N. Low Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(6):742-746
N,N′‐Dithiodiphthalimide, C16H8N2O4S2, crystallizes from ethyl acetate with two independent molecules in the asymmetric unit, in which the N—S—S—N torsion angles are ?83.59 (19) and 92.9 (2)°. The molecules are linked by C—H?O hydrogen bonds and aromatic π–π‐stacking interactions into a three‐dimensional framework. When crystallized from either dichloromethane or ethanol, solvates are formed in which the molecules of the title compound lie across twofold rotation axes in space group C2/c, with N—S—S—N torsion angles of 93.54 (7) and 96.14 (11)°. There are no hydrogen bonds in these solvates, but the molecules are linked by aromatic π–π‐stacking interactions into chains, between which there are continuous channels. Disordered solvent molecules occupy these channels, which account for ca 20% of the unit‐cell volume. 相似文献
105.
Molecular geometries and heats of formation are calculated, using MINDO/3, for the following mass-spectral fragment pairs derived from formic acid: X(2A')(HCOOH)+; (HCOO)+ + Hxxx; (HCO)+ + OH; HCO + (OH)+; (CO)+ + H2O; (CO2)+ + H2. The activation energy for the reaction (HCOOH)+ → (HCOO)+ + Hxxx is 75 kJ mol?1. A correlation is made of the symmetry classes of the electronic states of (HCOOH)+, accessible by single electron excitation, and those of the mass-spectral fragments: it is shown that, despite their closely similar appearance potentials, the ions (HCOO)+ and (HCO)+ arise from different states of (HCOOH)+. The structure of (HCOOH)2+ is also reported. 相似文献
106.
The geometry of the ground states of the isomers and transition state for the systems HCN ? HNC and BCN ? BNC have been investigated using a wide variety of basis sets, both at the self-consistent-field (SCF ) level and including correlation at the second-, and third-order Møller–Plesset (MP 2 and MP 3) levels. The barrier to isomerization and the isomerization energy were shown to be strongly dependent on the basis set and method, particularly for the BCN system. 相似文献
107.
MNDO calculations have been carried out on a number of conjugated bicyclic and tricyclic hydrocarbons. For reference purposes some acenes and monocyclic non-benzenoid hydrocarbons are also mentioned. While the influence of 2 or 6 π-electron systems in stabilising, and of 4 π-electron systems in destabilising, structures is readily evident, it is clear that arrays of 10 or more π-electrons have markedly less effect, and the balance between fixation of bonds and delocalisation in many compounds possessing such systems is subtle. 相似文献
108.
John N. Low Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(4):o209-o211
The title compound (C6H7NO3S) exists as a zwitterion (4‐ammoniobenzenesulfonate), +H3NC6H4SO3?, and these units are linked into a three‐dimensional framework by two distinct two‐centre N—H?O hydrogen bonds [H?O 1.84 and 1.87 Å; N?O 2.767 (2) and 2.746 (2) Å; N—H?O 166 and 172°] and a planar three‐centre N—H?(O)2 hydrogen bond [H?O 2.03 and 2.37 Å; N?O 2.816 (2) and 2.877 (2) Å; N—H?O 162 and 111°; O?H?O 86°]. 相似文献
109.
Christopher Glidewell John N. Low Janet M. S. Skakle James L. Wardell 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(4):o201-o203
Molecules of the title compound, [(4‐nitrophenyl)sulfanyl]acetic acid, C8H7NO4S, are linked by paired O—H?O hydrogen bonds [H?O 1.81 Å, O?O 2.6456 (15) Å and O—H?O 178°] into centrosymmetric dimers containing an R(8) motif. A single C—H?O hydrogen bond having a nitro O atom as acceptor [H?O 2.47 Å, 3.3018 (19) Å and C—H?O 147°] links the dimers into a molecular ladder, and neighbouring ladders are weakly linked into sheets by aromatic π–π‐stacking interactions. 相似文献
110.
Jos M. de la Torre Manuel Nogueras Justo Cobo John N. Low Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(11):o638-o640
The title compound [systematic name: 6‐amino‐5‐formyl‐1,3‐dimethylpyrimidine‐2,4(1H,3H)‐dione monohydrate], C7H9N3O3·H2O, has been reexamined at 120 K. The improved precision of the intramolecular dimensions provides evidence for a polarized molecular–electronic structure, and the molecular components are linked by one N—H...O and two O—H...O hydrogen bonds into two interwoven three‐dimensional frameworks, which are weakly linked by the longer component of a three‐centre N—H...(O)2 hydrogen bond. 相似文献