全文获取类型
收费全文 | 149篇 |
免费 | 4篇 |
专业分类
化学 | 105篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 31篇 |
物理学 | 14篇 |
出版年
2023年 | 1篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 13篇 |
2011年 | 11篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 4篇 |
2007年 | 9篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有153条查询结果,搜索用时 31 毫秒
61.
John Nicolson Low Antonio Quesada Luís M. N. B. F. Santos B. Schröder Ligia R. Gomes 《Journal of chemical crystallography》2009,39(10):747-752
Abstract The crystal structure of 2-thoiphenecarboxamide is described. The compound crystallizes in the orthorhombic Pna21 space group with unit cell parameters a = 10.044 (3) ?, b = 14.203 (4) ? and c = 15.941 (3) ?; V = 2,274.1 (10) ?3. The asymmetric unit contains four independent molecules which are linked by N–H···O hydrogen bonds. The asymmetric unit
at (x, y, z) is connected with another one, produced by the a-glide plane at 0.75 along the b-axis, that lies at (x + 0.5, −y + 1.5, z) by two N–H···O hydrogen bonds and by a C–H···O weak hydrogen bond to form a one-dimensional tube. Adjacent tubes are linked
by C–H···pi interactions to form a three-dimensional framework.
Graphical Abstract The crystal structure of 2-thiophenecarboxamide, contains four crystallographically independent molecular components in the
asymmetric unit linked by four N–H···O hydrogen bonds and a weak C–H···O hydrogen bond and form a one-dimensional tube.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
62.
Christopher Glidewell Debbie Cannon Antonio Quesada John N. Low Susan A. McWilliam Janet M. S. Skakle James L. Wardell 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):455-458
Molecules of 1,3‐diamino‐4‐nitrobenzene, C6H7N3O2, are linked by N—H?O hydrogen bonds [N?O 2.964 (2) and 3.021 (2) Å; N—H?O 155 and 149°] into (4,4) nets. In 3,5‐dinitroaniline, C6H5N3O4, where Z′ = 2, the molecules are linked by three N—H?O hydrogen bonds [N?O 3.344 (2)–3.433 (2) Å and N—H?O 150–167°] into deeply puckered nets, each of which is interwoven with its two immediate neighbours. 相似文献
63.
John N. Low Debbie Cannon Antonio Quesada Antonio Marchal Manuel Melguizo Manuel Nogueras Adolfo Snchez Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(5):604-607
In the title compound, 2C10H15N5O4·0.5H2O, there are two independent molecules of the pyrimidinylisoleucine in general positions and a water molecule lying on a twofold rotation axis. The bond lengths within the organic moieties demonstrate significant polarization of the electronic structure. Each of the organic molecules participates in 12 intermolecular hydrogen bonds, of O—H?O and N—H?O types, while the water molecule acts as a double donor and as a double acceptor of O—H?O hydrogen bonds. The organic components are linked by the hydrogen bonds into a single three‐dimensional framework, reinforced by the water molecules. 相似文献
64.
Antonio Quesada Antonio Marchal John N. Low Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(3):o102-o104
In the title compound, C14H23N6O2+·HSO4−·H2O, the pyrimidinium ring of the cation adopts a twist‐boat conformation, induced by steric clashes between adjacent ring substituents; the anions and the water molecules are linked by three O—H⃛O hydrogen bonds [H⃛O = 1.70–1.78 Å, O⃛O = 2.548 (2)–2.761 (2) Å and O—H⃛O = 161–168°] into chains of edge‐fused R(12) rings, which are linked into sheets by the cations, via three N—H⃛O hydrogen bonds [H⃛O = 1.96–2.17 Å, N⃛O = 2.820 (2)–2.935 (2) Å and N—H⃛O = 145–173°]. 相似文献
65.
The apparent difficulty that humans experience when asked to manage dynamic complexity might be related to their inability to discriminate among familiar classes of objects (i.e., flawed recognition). In this study we examined the change in individuals' recognition ability, as measured by the change in the similarity of decisions they made when confronted repeatedly with consistent dynamic situations of varying degrees of similarity. The study generated two primary findings. First, decisions became increasingly similar with task practice, a result that suggests gradually improving discrimination by the participants. Second, the similarity was determined by the interaction of many task features rather than individual task features. The general principles highlighted by this study are applicable to dynamic situations. For example, with practice, decision makers should be able to learn to identify the time at which to intervene to achieve the maximal effect during dynamic decision making. 相似文献
66.
Ernesto Quesada 《Tetrahedron》2006,62(28):6673-6680
Approaches to the preparation of C1-homologated dibromoalkenes and terminal alkynes from activated alcohols using one-pot tandem oxidation processes (TOPs) with manganese dioxide are outlined. The conversion of alcohols into dibromoalkenes is described using dibromomethyltriphenylphosphonium bromide and the formation of terminal alkynes was achieved via a sequential one-pot, two-step process utilising the Bestmann-Ohira reagent. 相似文献
67.
This review article highlights advances made in abiotic anion coordination chemistry from 2002 to 2004. The structure of this review is that similar to the previous reviews in this series that covered 1997–2001 [P.A. Gale, Coord. Chem. Rev. 199 (2000) 181; P.A. Gale, Coord. Chem. Rev. 213 (2001) 79; P.A. Gale, Coord. Chem. Rev. 240 (2003) 191]. The first section examines anion receptors that do not contain metal ions. This is followed by a review of metal containing anion receptors and finally the role of anions in directing the self-assembly of complex molecular architectures are presented in the final section. 相似文献
68.
M. Quesada J. Puig J.M. Delgado J.M. Peula J.A. Molina R. Hidalgo-Álvarez 《Colloids and surfaces. B, Biointerfaces》1997,8(6):80-309
Polymer colloids coated by antibodies are used in diagnostic tests for the detection of antigens in biological fluids. We present in this paper a simple kinetic model for the optical monitoring of the formation of specific complexes between antigen and antibody with amplification by latex beads. The antibodies are physical or chemically adsorbed onto sulphonate polystyrene or chloromethylstyrene particles respectively. This is a very simple model combining the La Mer idea of optimum surface coverage with Langmuir adsorption of antigen molecules. The kinetic model explains reasonably well the optical response of immunolatex prepared by both methods of immobilization of antibodies on polymer carriers. According to the results obtained with this model the percentage of active IgG on latex particles is extremely low, with a maximum of a 5%. 相似文献
69.
Christopher Glidewell John N. Low Antonio Quesada Manuel Nogueras Adolfo Snchez 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(7):o425-o427
In the title compound, C22H23N5O4, the molecules are linked into chains by a three‐centre N—H?(N,O) hydrogen bond, reinforced by a two‐centre C—H?O hydrogen bond, and the chains are further linked into sheets by a combination of C—H?O and C—H?π(arene) hydrogen bonds. 相似文献
70.
Antonio Quesada Maria A. Fontecha Maria V. Lpez John N. Low Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(8):o463-o466
The title compound (trivial name terbutylazine), C9H16ClN5, (I), crystallizes with Z′ = 4 in the space group Pca21, and equal numbers of molecules adopt two different conformations for the ethylamine groups. The four independent molecules form two approximately enantiomorphic pairs. Eight independent N—H...N hydrogen bonds link the molecules into two independent chains of R22(8) rings, in which the arrangement of the alkylamine substituents in the independent molecules precludes any further crystallographic symmetry. The significance of this study lies in its finding of two distinct molecular conformations within the structure and two distinct ways in which the molecules are organized into hydrogen‐bonded chains, and in its comparison of the hydrogen‐bonded structure of (I) with those of analogous 1,3,5‐triazines and pyrimidines. 相似文献