全文获取类型
收费全文 | 119篇 |
免费 | 12篇 |
专业分类
化学 | 115篇 |
晶体学 | 4篇 |
数学 | 5篇 |
物理学 | 7篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 3篇 |
2012年 | 8篇 |
2011年 | 10篇 |
2010年 | 4篇 |
2009年 | 5篇 |
2008年 | 2篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 12篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 18篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1987年 | 2篇 |
1899年 | 1篇 |
排序方式: 共有131条查询结果,搜索用时 46 毫秒
81.
Hctor Novoa de Armas Oswald M. Peeters Norbert M. Blaton Camiel J. De Ranter Jos A. Ruíz Garcia Mayra Reyes Moreno Yoanna M. Alvarez Ginarte 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):e582-e583
In the title compounds, C23H33NO3 and C21H30O3, respectively, the ester linkage in ring A is equatorial. In these steroids, the six‐membered rings A and B have chair conformations, but ring C can be better described as a half‐chair. The five‐membered ring D adopts a 14α‐envelop conformation. The A/B, B/C and C/D ring junctions are trans. 相似文献
82.
Hctor Novoa de Armas Hiram Prez Oswald M. Peeters Norbert M. Blaton Camiel J. De Ranter Jos Manuel Lpez 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):e98-e99
The title compound, (C6H5CH2)3PO, is an organic tertiary phosphine oxide. The molecule has threefold symmetry, with the P—O bond along the threefold axis. Main dimensions include P—O 1.488 (4), P—C 1.823 (3) Å and O—P—C 114.7 (1)°. The crystals were accidentally obtained when preparing complexes of nickel(II) with dibenzylphosphine. 相似文献
83.
In this work we report the synthesis of polycrystalline samples of Bi5FeTi3O15 and Bi3R2FeTi3O15 new compounds with R=Nd, Sm, Gd, Dy, Ho and Yb. The materials were synthesized by the standard solid state reaction recipe from high purity (99.99%) powders. The structural characteristics of materials were analyzed by X-ray diffraction experiments. Rietveld refinement by the GSAS code was performed, taking the input data from the ICSD 74037 database. Results reveal that materials crystallized in orthorhombic single-phase structures and space group Fmm2. Measurements of polarization as a function of applied electric field were carried out using a Radiant Technology polarimeter. We determine the occurrence of hysteretic behaviors, which are characteristic of ferroelectric materials. The main values of remnant and coercive applied fields were observed for substitutions with Yb and Nd, which have the main atomic radii. 相似文献
84.
Ruiz E Rodríguez H Coro J Niebla V Rodríguez A Martínez-Alvarez R de Armas HN Suárez M Martín N 《Ultrasonics sonochemistry》2012,19(2):221-226
A facile, efficient and environment-friendly protocol for the synthesis of 6-chloro-5-formyl-1,4-dihydropyridine derivatives has been developed by the convenient ultrasound-mediated reaction of 2(1H)pyridone derivatives with the Vilsmeier-Haack reagent. This method provides several advantages over current reaction methodologies including a simpler work-up procedure, shorter reaction times and higher yields. 相似文献
85.
Cover Picture: A New Conformation With an Extraordinarily Long, 3.04 Å Two‐Electron,Six‐Center Bond Observed for the π‐[TCNE]22− Dimer in [NMe4]2[TCNE]2 (TCNE=Tetracyanoethylene) (Chem. Eur. J. 38/2015) 下载免费PDF全文
86.
Crespo A Coelho A Diz PM Fernández F Novoa de Armas H Sotelo E 《Organic & biomolecular chemistry》2011,9(2):351-357
A convergent and versatile Vilsmeier-Haack-based carbo-annulation strategy that exhibits an unusually elevated bond-forming efficiency has been developed. By virtue of its innovative approach, structure economy and simple execution conditions the methodology reported here constitutes a very attractive protocol that enables the rapid assembly of structurally diverse quinazoline chemotypes. 相似文献
87.
Capel Ferrón C Ruiz Delgado MC Hernández V López Navarrete JT Vercelli B Zotti G Capdevila Cortada M Novoa JJ Niu W He M Hartl F 《Chemical communications (Cambridge, England)》2011,47(47):12622-12624
We have investigated the impact of the functionalization and the chemical nature of counterions on the π-dimer dications formation in two end-capped heptathienoacenes. Radical cations of an α-substituted heptathienoacene with triisopropylsilyl groups do not π-dimerize, while those of an α,β-substituted heptathienoacene with four n-decyl side chains show a high propensity toward π-dimerization, increased by PF(6)(-) counterions. 相似文献
88.
The Origin of the Room‐Temperature Stability of [TTF].+⋅⋅⋅[TTF].+ Long,Multicenter Bonds Found in Functionalized π‐[R‐TTF]22+ Dimers Included in the Cucurbit[8]uril Cavity 下载免费PDF全文
Marçal Capdevila‐Cortada Prof. Joel S. Miller Prof. Juan J. Novoa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7784-7795
A computational study is performed to identify the origin of the room‐temperature stability, in aqueous solution, of functionalized π‐[R‐TTF]22+ dimers (TTF=tetrathiafulvalene; R=(CH2OCH2)5CH2OH) included in the cavity of a cucurbit[8]uril (CB[8]) molecule. π‐[R‐TTF]22+ dimers in pure water are weakly stable, and are mostly dissociated at room temperature. Upon addition of CB[8] to an aqueous π‐[R‐TTF]22+ solution, a (π‐[R‐TTF]2?CB[8])2+ inclusion complex is formed. The same complex is obtained after the sequential inclusion of two [R‐TTF].+ monomers in the CB[8] molecule. Both processes are thermodynamically and kinetically allowed. π‐[R‐TTF]22+ dimers dissolved in pure water present a [TTF].+???[TTF].+ long, multicenter bond, similar to that already identified in π‐[TTF]22+ dimers dissolved in organic solvents. Upon their inclusion in CB[8], the strength and other features of the [TTF].+???[TTF].+ long, multicenter bond are preserved. The room temperature stability of the π‐[R‐TTF]22+ dimers included in CB[8] is shown to originate in the π‐[R‐TTF]22+???CB[8] interaction, the strength of which comes from a strongly attractive electrostatic component and a dispersion component. Such a dominant electrostatic term is caused by the strongly polarized charge distribution in CB[8], the geometrical complementarity of the π‐[R‐TTF]22+ and CB[8] geometries, and the amplifying effect of the 2+ charge in π‐[R‐TTF]22+. 相似文献
89.
On the Importance of Thermal Effects and Crystalline Disorder in the Magnetism of Benzotriazinyl‐Derived Organic Radicals 下载免费PDF全文
Maria Fumanal Dr. Sergi Vela Dr. Jordi Ribas‐Ariño Prof. Juan J. Novoa 《化学:亚洲杂志》2014,9(12):3612-3622
Recent experiments suggest that benzotriazinyl‐derived radicals are promising building blocks for the design of new functional materials. Herein, a detailed computational study of the main structural and magnetic features of two prototypes of this family of radicals is presented. By means of several computational techniques within the DFT framework, this work unveils the key importance of the thermal contraction of the crystal to quantitatively predict the magnetism of the studied compounds. In this sense, for the first time in the context of molecular magnetism, we propose to use variable‐cell geometry optimizations as an efficient alternative to obtain an estimation of low‐temperature crystal structures. The crucial role of crystalline disorder in defining the structure present at low temperature, and thus, the magnetic response, is revealed. Altogether, these are important elements for the rational design of future materials of this family of compounds. 相似文献
90.