全文获取类型
收费全文 | 560篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
化学 | 405篇 |
晶体学 | 6篇 |
力学 | 9篇 |
数学 | 22篇 |
物理学 | 142篇 |
出版年
2020年 | 5篇 |
2019年 | 11篇 |
2016年 | 17篇 |
2015年 | 12篇 |
2014年 | 12篇 |
2013年 | 19篇 |
2012年 | 19篇 |
2011年 | 26篇 |
2010年 | 11篇 |
2009年 | 8篇 |
2008年 | 20篇 |
2007年 | 17篇 |
2006年 | 20篇 |
2005年 | 29篇 |
2004年 | 11篇 |
2003年 | 23篇 |
2002年 | 12篇 |
2001年 | 20篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1990年 | 7篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1980年 | 5篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1971年 | 4篇 |
1964年 | 6篇 |
1963年 | 7篇 |
1962年 | 4篇 |
1960年 | 4篇 |
1956年 | 4篇 |
1955年 | 4篇 |
1954年 | 8篇 |
1941年 | 6篇 |
1939年 | 6篇 |
1938年 | 4篇 |
1937年 | 11篇 |
1936年 | 3篇 |
1935年 | 6篇 |
1932年 | 3篇 |
1928年 | 4篇 |
排序方式: 共有584条查询结果,搜索用时 0 毫秒
1.
Poly(ortho‐phenylene ethynylene)s (PoPEs) have been synthesized via an in situ activation/coupling AB′ polycondensation protocol. The resulting polymers have been characterized by several analytical methods and are shown to have no structural defects. Although the Sonogashira–Hagihara polycondensation reaction is less efficient than for the preparation of the corresponding meta‐ and para‐linked polymers, presumably because of steric hindrance caused by the ortho substituents, the process can be accelerated by the use of microwave irradiation. Optical spectroscopy indicates solvent‐dependent conformational changes between extended transoid and helical cisoid conformations, providing the first experimental evidence for solvophobically driven folding of the PoPE backbone. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1619–1627, 2006 相似文献
2.
3.
Dirk Lützenkirchen‐Hecht Kay Rohrmann Thomas Stöcker Wolfgang Thiel 《Surface and interface analysis : SIA》2007,39(11):845-851
Different ink‐jet printed paper materials were investigated using X‐ray photoelectron spectroscopy (XPS) yielding the elemental composition of the near‐surface region of the papers. We found significant differences with respect to the detected elements and their atomic concentrations in the different inks studied here. Two different groups of inks could be identified by means of a lower ratio of the O and C atomic concentrations and lower concentrations in specific trace elements like Mg, Na and Si. High‐resolution spectra of C 1s and O 1s core levels allowed a detailed determination of the chemical state of the respective elements. On the basis of a detailed deconvolution of these XPS signals, significant differences between all the investigated ink‐jet printed papers were found, thereby allowing their discrimination. The applicability of the measurements and, more generally, the XPS technique for forensic investigations of paper are discussed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
4.
Formation and Crystal Structure of an Oxygen Bridged Titanium Amino Bisphenoxide Di‐(μ‐oxo)‐titan‐bis[aminobisphenoxide] ( 3 ) was obtained by reaction of (i‐Prop)2TiL* ( 2 ) {L* = O‐4, 6‐(t‐Bu)2C6H2‐2‐CH2‐[1, 4‐N2C5H10]‐2'‐CH2‐4', 6'‐(t‐Bu)2C6H2O] with water in a molar ratio 1:1 in diethylether. Both i‐Propyl moieties are substituted yielding the dimeric oxygen bridged amino bisphenoxide complex. The six coordinate Ti atoms are a result of Ti—N and Ti—O interactions of the corresponding atoms of the amino bisphenoxide ligand and the bridging O atoms. The central planar Ti2O2 ring may be considered as the general structural feature of the title compound: Space group P1¯, Z = 1, lattice dimensions at —60°C: a = 11.6899(4), b = 11.7873(4), c = 12.6462(4) Å, α = 98.070(1), β = 99.660(1), γ = 95.343(1)°, R1 = 0.0469, wR2 = 0.1049, GooF = 0.939. 相似文献
5.
VladimirA. Azov Franois Diederich Yoriko Lill Bert Hecht 《Helvetica chimica acta》2003,86(6):2149-2155
We report the synthesis of modified Cram‐type cavitands bearing one or two fluorescent labels for single‐molecule spectroscopic studies of vase? kite conformational switching (Scheme 3). Syntheses were performed by stepwise bridging of the four couples of neighboring H‐bonded OH groups of resorcin[4]arene bowls (Schemes 2 and 3). The new substitution patterns enable the construction of a large variety of future functional architectures. 1H‐NMR Investigations showed that the new partially and differentially bridged cavitands feature temperature‐ and pH‐triggered vase? kite conformational isomerism similar to symmetrical cavitands with four identical quinoxaline bridges (Table). It was discovered that vase? kite switching of cavitands is strongly solvent‐dependent. 相似文献
6.
Porphyrin and pyrene photoactive cores have been encapsulated within an isolating polymeric shell using an efficient and general strategy based on the use of dendritic initiators for the ring-opening polymerization of epsilon-caprolactone to yield functional core star polymers. The isolation of the core functionalities has been studied using fluorescence quenching and fluorescence resonance energy transfer (FRET) techniques as well as solvatochromic probes. With increasing chain length as well as solvent polarity, enhanced site isolation of the core has been observed. These findings have been correlated to actual molecular dimensions independently measured by pulsed field gradient spin-echo (PGSE) NMR. The developed synthetic methodology offers a rapid route to efficient encapsulation of functional moieties and therefore has potential for the design of new materials. 相似文献
7.
Mulligan A Lane I Rousseau GB Hecht L Johnston SM Lennon D Kadodwala M 《Chemical communications (Cambridge, England)》2004,(21):2492-2493
Using a novel non-linear optical technique enantiomeric excess within a translationally disordered overlayer on a metal surface has been monitored for the first time. 相似文献
8.
9.
10.