全文获取类型
收费全文 | 118篇 |
免费 | 11篇 |
国内免费 | 36篇 |
专业分类
化学 | 163篇 |
物理学 | 2篇 |
出版年
2024年 | 1篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 9篇 |
2019年 | 3篇 |
2018年 | 10篇 |
2017年 | 4篇 |
2016年 | 11篇 |
2015年 | 10篇 |
2014年 | 10篇 |
2013年 | 9篇 |
2012年 | 21篇 |
2011年 | 6篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 3篇 |
2007年 | 5篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 11篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有165条查询结果,搜索用时 15 毫秒
61.
The conversion of ethene and propene has been studied in the process of adsorption on Pt foil and in adsorbed state. Mainly
C−C bond cleavage and limited C−C bond formation was observed in 323–523 K temperature interval. 相似文献
62.
Makoto MurataTakayoshi Hara Kohsuke MoriMasahiko Ooe Tomoo MizugakiKohki Ebitani Kiyotomi Kaneda 《Tetrahedron letters》2003,44(27):4981-4984
Hydroxyapatite-bound Pd catalyst was found to be highly effective for the deprotection of N-benzyloxycarbonyl group from amino acids in the presence of molecular hydrogen. The catalyst was also applicable to the hydrogenolysis of a sterically encumbered core-Z-protected poly(amido amine) dendrimer, affording the dendritic amino compound in 99% yield. 相似文献
63.
The hydrogenolysis of the Ar-Cl bond in chlorinated benzoic acids, anilines, and nitrogen-containing heterocycles by the action of NaH2PO2 in the presence of catalytic amounts of PdCl2 and NaOH in an aqueous medium was studied. Under these conditions aryl chlorides were quantitatively converted into the corresponding arenes. Chloropyridines, such as 2-chloropyridine and 3, 5-dichloropicolinic acid, did not undergo hydrogenolysis even in the presence of an equivalent amount of NaI. A distinctortho effect was observed forortho-substituted substrates.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 607–609, March, 1993. 相似文献
64.
65.
Ustynyuk L. Yu. Ustynyuk Yu. A. Laikov D. N. Lunin V. V. 《Russian Chemical Bulletin》2001,50(11):2050-2053
Model reactions of silica-supported zirconium hydrides (Si—O—)3ZrH and (Si—O—)2ZrH2 with methane, resulting in cleavage of a C—H bond in the methane molecule and the formation of (Si—O—)3ZrCH3 and (Si—O—)2Zr(H)CH3 as products were studied using the DFT approach with the PBE density functional. The processes proceed as bimolecular reactions without preliminary formation of agostic complexes. According to calculations, zirconium dihydrides (Si—O—)2ZrH2 are more reactive toward the methane C—H bonds than zirconium monohydrides (Si—O—)3ZrH. The calculated activation energies of the reactions with participation of zirconium dihydrides (Si—O—)2ZrH2 are in better agreement with the known experimental data for the Yermakov—Basset catalytic system. 相似文献
66.
67.
Protection Group Effects During α,γ‐Diol Lignin Stabilization Promote High‐Selectivity Monomer Production
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Wu Lan Masoud Talebi Amiri Christopher M. Hunston Prof. Jeremy S. Luterbacher 《Angewandte Chemie (International ed. in English)》2018,57(5):1356-1360
Protection groups were introduced during biomass pretreatment to stabilize lignin's α,γ‐diol group during its extraction and prevent its condensation. Acetaldehyde and propionaldehyde stabilized the α,γ‐diol without any aromatic ring alkylation, which significantly increased final product selectivity. The subsequent hydrogenolysis catalyzed by Pd/C generated lignin monomers at near‐theoretical yields based on Klason lignin (48 % from birch, 20 % from spruce, 70 % from high‐syringyl transgenic poplar), and with high selectivity to a single 4‐n‐propanolsyringol product (80 %) in the case of the poplar. Unlike direct hydrogenation of native wood, hydrogenolysis of protected lignin with Ni/C also led to high selectivity to this single product (78 %), paving the way to high‐selectivity lignin upgrading with base metal catalysts. The use of extracted lignin facilitated valorization of polysaccharides, leading to high yields of all three major biomass polymers to a single major product. 相似文献
68.
A novel tripod boron dipyrromethene (BODIPY) dye bearing N-hydroxysuccinimide ester was synthesized through its carboxylic acid precursor, and the functionality was confirmed by its amidation reaction with a primary amine. It is the first time that a reactive functional group was introduced onto a tripod BODIPY structure. All the new structures had been characterized by NMR, HRMS, and IR spectra. The introduction of an electron-donative diethylamine proved to be a key factor for the successful hydrogenolysis of the corresponding tris-substituted 1,3,5-triazine structure. 相似文献
69.
Prof. Dr. Holger Braunschweig Dr. Frank Guethlein Lisa Mailänder Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(44):14831-14835
A new synthetic approach to hydroboranes catechol‐, pinacol‐, and neopentylglycolborane has been developed. Starting from diboranes(4) B2cat2, B2pin2, or B2neop2, the respective boranes were obtained by heterogeneously catalyzed cleavage of the B? B bond in the respective diboranes with hydrogen. Group 10 metals were found to be effective catalysts for this reaction. 相似文献
70.
《Analytical letters》2012,45(7):353-372
Abstract The design of an improved open microcombustion tube and experimental conditions for the rapid, accurate and precise determination of sulfur and chlorine by microcoulometry are described. The design and operating conditions for a catalytic hydrogenolysis tube and scrubber tube for acid removal are also presented for the determination of nitrogen. Examples of the application of the above methods for these elements in petroleum and petrochemicals are presented. 相似文献