全文获取类型
收费全文 | 97篇 |
免费 | 13篇 |
专业分类
化学 | 71篇 |
力学 | 1篇 |
数学 | 2篇 |
物理学 | 36篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 3篇 |
2012年 | 6篇 |
2011年 | 5篇 |
2010年 | 11篇 |
2009年 | 5篇 |
2008年 | 3篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
排序方式: 共有110条查询结果,搜索用时 234 毫秒
41.
Jason T Miller John H Bartley Hereward JC Wimborne Aisha L Walker David C Hess William D Hill James E Carroll 《BMC neuroscience》2005,6(1):63
Background
Stromal cell-derived factor 1 (SDF-1 or CXCL12) is chemotaxic for CXCR4 expressing bone marrow-derived cells. It functions in brain embryonic development and in response to ischemic injury in helping guide neuroblast migration and vasculogenesis. In experimental adult stroke models SDF-1 is expressed perivascularly in the injured region up to 30 days after the injury, suggesting it could be a therapeutic target for tissue repair strategies. We hypothesized that SDF-1 would be expressed in similar temporal and spatial patterns following hypoxic-ischemic (HI) injury in neonatal brain. 相似文献42.
Phosphole-containing π-systems have emerged as building blocks with enormous potential as electronic materials because of the tunability of the phosphorus center. Among these, asymmetric P-bridged trans-stilbenes are still rare, and here an elegant and efficient synthesis toward such fluorescent molecular frameworks is described. Fine-tuning of the photophysical properties is attempted by enforcing the planarization of the phosphorus tripod and thus increasing the interaction between the phosphorus lone pair and the π-system. The electronic structure of the π-conjugated frameworks is analyzed with NMR, UV-vis and fluorescence spectroscopy, and time-dependent density functional theory (TD-DFT) calculations. 相似文献
43.
OK Yoon WG Hwang JC Choe MS Kim 《Rapid communications in mass spectrometry : RCM》1999,13(14):1515-1521
A technique to investigate photodissociation kinetics on a nanosecond time scale has been devised for molecular ions generated by multiphoton ionization (MPI) using mass-analyzed ion kinetic energy spectrometry. The branching ratio or rate constant has been determined for the photodissociation of the n-butylbenzene, bromobenzene, iodobenzene, and aniline molecular ions generated by MPI at 266 nm. The ion internal energies have been estimated by comparing the measured kinetic data with the previous energy dependence data. The analysis has shown that only those molecular ions generated by two-photon ionization contribute to the photodissociation signals. Around half of the available energy has been found to remain as molecular ion internal energy in the two-photon ionization process. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
44.
α-Haloketones and -dibromides are converted to the corresponding ketones and alkenes respectively with nickel boride generated from sodium borohydride and nickel chloride. 相似文献
45.
Casper D Becker-Szendy R Bratton CB Cady DR Claus R Dye ST Gajewski W Goldhaber M Haines TJ Halverson PG Jones TW Kielczewska D Kropp WR Learned JG LoSecco JM McGrew C Matsuno S Matthews J Mudan MS Price L Reines F Schultz J Sinclair D Sobel HW Stone JL Sulak LR Svoboda R Thornton G van der Velde JC 《Physical review letters》1991,66(20):2561-2564
46.
Jaap E. Borger Dr. Andreas W. Ehlers Dr. Martin Lutz Dr. J. Chris Slootweg Prof. Dr. Koop Lammertsma 《Angewandte Chemie (International ed. in English)》2016,55(2):613-617
The transient bicyclo[1.1.0]tetraphosphabutane anion, generated from white phosphorus (P4) and Mes*Li (Mes*=2,4,6‐tBu3C6H2), can be trapped by BPh3 in THF. This Lewis acid stabilized anion can be used as an [RP4]? transfer agent, reacting cleanly with neutral Lewis acids (B(C6F5)3, BH3, and W(CO)5) to afford unique singly and doubly coordinated butterfly anions, and with the trityl cation to form a neutral, nonsymmetrical, all‐carbon‐substituted P4 derivative. This reaction path enables a simple, stepwise functionalization of white phosphorus. 相似文献
47.
Wolf R Ehlers AW Khusniyarov MM Hartl F de Bruin B Long GJ Grandjean F Schappacher FM Pöttgen R Slootweg JC Lutz M Spek AL Lammertsma K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(48):14322-14334
The preparation and comprehensive characterization of a series of homoleptic sandwich complexes containing diphosphacyclobutadiene ligands are reported. Compounds [K([18]crown-6)(thf)(2)][Fe(η(4)-P(2)C(2)tBu(2))(2)] (K1), [K([18]crown-6)(thf)(2)][Co(η(4)-P(2)C(2)tBu(2))(2)] (K2), and [K([18]crown-6)(thf)(2)][Co(η(4)-P(2)C(2)Ad(2))(2)] (K3, Ad = adamantyl) were obtained from reactions of [K([18]crown-6)(thf)(2)][M(η(4)-C(14)H(10))(2)] (M = Fe, Co) with tBuC[triple bond]P (1, 2), or with AdC[triple bond]P (3). Neutral sandwiches [M(η(4)-P(2)C(2)tBu(2))(2)] (4: M = Fe 5: M = Co) were obtained by oxidizing 1 and 2 with [Cp(2)Fe]PF(6). Cyclic voltammetry and spectro-electrochemistry indicate that the two [M(η(4)-P(2)C(2)tBu(2))(2)](-)/[M(η(4)-P(2)C(2)tBu(2))(2)] moieties can be reversibly interconverted by one electron oxidation and reduction, respectively. Complexes 1-5 were characterized by multinuclear NMR, EPR (1 and 5), UV/Vis, and M?ssbauer spectroscopies (1 and 4), mass spectrometry (4 and 5), and microanalysis (1-3). The molecular structures of 1-5 were determined by using X-ray crystallography. Essentially D(2d)-symmetric structures were found for all five complexes, which show the two 1,3-diphosphacyclobutadiene rings in a staggered orientation. Density functional theory calculations revealed the importance of covalent metal-ligand π bonding in 1-5. Possible oxidation state assignments for the metal ions are discussed. 相似文献
48.
Halil Aktaş Dr. J. Chris Slootweg Dr. Koop Lammertsma Prof. Dr. 《Angewandte Chemie (International ed. in English)》2010,49(12):2102-2113
Syntheses, properties, and reactivities of nucleophilic phosphinidene complexes [LnM?P? R] are reviewed. Emphasis is placed on the electronic tuning of this emerging class of phosphorus reagents, using different ancillary ligands and coordinatively unsaturated transition‐metal moieties. The difference in applicability of the established stable 18‐electron and transient 16‐electron phosphinidenes is addressed. 相似文献
49.
Flip Holtrop Dr. Andrew R. Jupp Bastiaan J. Kooij Nicolaas P. van Leest Prof. Dr. Bas de Bruin Prof. Dr. J. Chris Slootweg 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22394-22400
Frustrated Lewis pairs (FLPs) are well known for their ability to activate small molecules. Recent reports of radical formation within such systems indicate single-electron transfer (SET) could play an important role in their chemistry. Herein, we investigate radical formation upon reacting FLP systems with dihydrogen, triphenyltin hydride, or tetrachloro-1,4-benzoquinone (TCQ) both experimentally and computationally to determine the nature of the single-electron transfer (SET) events; that is, being direct SET to B(C6F5)3 or not. The reactions of H2 and Ph3SnH with archetypal P/B FLP systems do not proceed via a radical mechanism. In contrast, reaction with TCQ proceeds via SET, which is only feasible by Lewis acid coordination to the substrate. Furthermore, SET from the Lewis base to the Lewis acid–substrate adduct may be prevalent in other reported examples of radical FLP chemistry, which provides important design principles for radical main-group chemistry. 相似文献
50.
G. Bas de Jong Nuria Ortega Dr. Martin Lutz Prof. Dr. Koop Lammertsma Prof. Dr. J. Chris Slootweg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(68):15944-15952
In this paper, we highlight the synthesis of a variety of primary phosphine-boranes (RPH2⋅BH3) from the corresponding dichlorophosphines, simply by using Li[BH4] as reductant and provider of the BH3 protecting group. The method offers facile access not only to alkyl- and arylphosphine-boranes, but also to aminophosphine-boranes (R2NPH2⋅BH3) that are convenient building blocks but without the protecting BH3 moiety thermally labile and notoriously difficult to handle. The borane-protected primary phosphines can be doubly deprotonated using n-butyllithium to provide soluble phosphanediides Li2[RP⋅BH3] of which the phenyl-derivative Li2[PhP⋅BH3] was structurally characterized in the solid state. 相似文献