全文获取类型
收费全文 | 295篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 238篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 29篇 |
物理学 | 27篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 10篇 |
2013年 | 23篇 |
2012年 | 16篇 |
2011年 | 14篇 |
2010年 | 12篇 |
2009年 | 16篇 |
2008年 | 6篇 |
2007年 | 9篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 15篇 |
2003年 | 14篇 |
2002年 | 15篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 10篇 |
1992年 | 1篇 |
1991年 | 5篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有299条查询结果,搜索用时 151 毫秒
61.
Giuliana Biagi Irene Giorgi Oreste Livi Valerio Scartoni Silvia Velo Antonio Lucacchini Generoso Senatore Pier Luigi Barili 《Journal of heterocyclic chemistry》1995,32(1):169-176
Several new 1,2,3-triazolo[4,5-b][1,4]diazepines were prepared starting from 1-benzyl-1 and 1-phenethyl-4,5-diamino-1,2,3-triazole 2 (Scheme 1), by condensation reactions with β-diketones (Scheme 2), β-ketoesters (Scheme 3), and diethyl malonates (Scheme 4). In the first case we obtained compounds 3 and 4 with basic properties, while the ester function condensations gave cyclic amide derivatives 7, 8, 10, 12 and 13 with acid properties. Some N-methyl derivatives 11, 14 and 15 were obtained from the cyclic amide compounds. Most of compounds were tested for their ability to displace [3H]flunitrazepam from bovine brain membranes but no compound showed benzodiazepine receptor binding affinity. 相似文献
62.
Giuliana Biagi Irene Giorgi Oreste Livi Antonio Nardi Valerio Scartoni 《Journal of heterocyclic chemistry》2002,39(6):1293-1298
Four new triazolylbenzimidazolthione derivatives (2a‐d), analogous to triazolylbenzimidazolone derivatives previously tested as activators of the BKCa potassium channels, were prepared and assayed without success. Some derivatives of a new tricyclic nitrogen heterocycle, 1,2,3‐triazolo[1,5‐a][1,3,5]benzo‐triazepine, bearing a carboxamido group in the 3 position, other substituents in the 8 position and a carbonyl (5a‐d) or thione (6a‐c) or methylthio (7a‐c) function in the 5 position were synthesised. The nucleophilic displacement of the methylthio substituent with morpholine or cyclopentylamine provided the 5‐amino‐substituted tricyclic derivatives 8a‐d. Starting from the l‐(2‐nitrophenyl)‐4‐cyano‐5‐amino‐1,2,3‐triazole (9), the 3‐cyano‐triazolobenzotriazepin‐5‐one derivative 12 was also obtained. The majority of the new compounds were tested towards the BKCa potassium channels, the benzodiazepine and adenosine A1 and A2a receptors, but no remarkable activity was detected. 相似文献
63.
Söldner FX McCormick K Eckhartt D Kornherr M Leuterer F Bartiromo R Becker G Bosch HS Brocken H Derfler H Eberhagen A Fussmann G Gehre O Gernhardt J Gierke Gv Giuliana A Glock E Gruber O Haas G Hesse M Hofmann J Izvozchikov A Janeschitz G Karger F Keilhacker M Klüber O Lackner K Lenoci M Lisitano G Mast F Mayer HM Meisel D Mertens V Müller ER Münich M Murmann H Niedermeyer H Pietrzyk A Poschenrieder W Rapp H Riedler H Röhr H Ryter F Schmitter KH Schneider F Setzensack C Siller G Smeulders P 《Physical review letters》1986,57(9):1137-1140
64.
György Bor Urs K. Dietler Pier Liugi Stanghellini Giuliana Gervasio Rosanna Rossetti Gino Sbrignadello Giovanni A. Battiston 《Journal of organometallic chemistry》1981,213(1):277-292
Co6C(CO)12S2 (I) has been isolated in crystalline form from the mixture of more than a dozen of carbonyl products formed when Co2(CO)8 reacts at room temperature with CS2. Crystals of I are monoclinic with space group Cc, and lattice constants a 16.250(5), b 9.413(4), c 16.036(5) Å, β 116.77(4)°. Structure refinement gave R 0.034 for 1974 reflections. The CCo6S2 core of the molecule possesses idealized D3h geometry. It is composed of a Co6 trigonal prism, enclosing a C atom in the centre, and the triangular faces are capped symmetrically by the two S atoms. The core contains two sorts od CoCo distances: short one (2.432 Å) along the triangular edges, and long ones (2.669 Å) along the lateral edges. The average CoC distance is 1.94 Å, and the average CoS distance 2.192 Å.13CO-enriched samples were prepared photochemically and their IR spectra used in the assignment of the CO stretching frequencies. The CO stretching force constant was calculated to be 1670(2) Nm-1.By the use of 13CS2, I has also been obtained in a selectively carbido-13C-labelled form. The vibrational frequencies of the carbide atom were observed, and that at 819 cm-1 (13C: 790 cm-1) assigned to the species , and that at 548 cm-1 (13C: 535.5 cm-1) to species E′. For the Co-C(carbide) force constant a value of 155 Nm-1 was calculated. The cobalt—sulphur stretching frequencies were found at 309 cm-1 () and 239 cm-1 (E′). The CoS stretching force constant, 78 Nm-1, is considerably lower than that obtained for SCo3-(CO)9, viz. 112 Nm-1. 相似文献
65.
Alessandro Bongini Giuliana Cardillo Mario Orena Gianni Porzi Sergio Sandri 《Tetrahedron letters》1979,20(27):2545-2548
N-iodosuccinimide (NIS) induces cyclization of substituted 2-allyl-phenols to 3-iodochromanes which may be dehydrohalogenated to the corresponding chrom-3-enes. 相似文献
66.
Fulvia Felluga Giuliana Pitacco Cristina Visintin Ennio Valentin 《Helvetica chimica acta》1997,80(5):1457-1472
The stereochemistry of 1,3-dipolar cycloaddition of azomethine ylides derived from aromatic aldehydes and i-proline alkyl esters with several nitroolefins was investigated. Cyclic and acyclic nitroolefins add to the anti form of the ylide in a highly diastereoselective but poorly regioselective manner to give pyrrolizidine derivatives. In a few cases, the stereochemical results strongly support a stepwise mechanism. 相似文献
67.
Giuliana Biagi Irene Giorgi Oreste Livi Federica Pacchini Valerio Scartoni Oreste Leroy Salerni 《Journal of heterocyclic chemistry》2004,41(4):575-580
A suitably substituted pyrimidine 1 was converted to a number of title compounds. Nucleophilic substitu tion involving the chlorine atoms in 1 by treatment with phenylmethanethiol yielded 2 or 3 , depending on the reaction temperature. Treatment of 3 with an amine afforded 6‐phenylmethanesulfanyl‐N4‐substituted‐2‐phenyl‐pyrimidine‐4,5‐diamines 4–7 . These pyrimidines were converted into 2‐phenylpurines 8–11 and 2‐phenyl‐8‐azapurines 12–14 , by treatment with triethyl orthoformate in the presence of hydrochloric acid (or acetic anhydride), or with potassium nitrite and acetic acid respectively. The thioether function on C(6) was then converted into a sulfonyl group by oxidation with m‐chloroperoxybenzoic acid affording purines 15–18 and their 8‐azaanalogs 19–21 ; these compounds, as crude products, were treated with an amine to yield the corresponding adenines 22–25 or 8‐azaadenines 26–31. All reactions were performed under conditions com patible with the possible use of a thiomethyl resin in place of phenylmethanethiol to bind the pyrimidine ring of 1 to a solid phase. 相似文献
68.
An expeditious synthesis of three polyoxygenated flavones: mosloflavone, negletein and baicalein, starting from crysin, an easily available flavone, by a bromination/methoxylation procedure is reported. The convergent synthesis exploits a base induced Wesley-Moser type rearrangement. 相似文献
69.
Giuliana Righi Simona Ciambrone Alessandra Pompili Francesco Caruso 《Tetrahedron letters》2007,48(43):7713-7716
A novel and efficient one-pot stereoselective transformation of N-(t-butoxycarbonyl)-2,3-aziridino alcohols into 4-substituted and 4,5-disubstituted oxazolidin-2-ones has been developed; these functionalized products are amenable to other elaborations, some of which are described. 相似文献
70.
Giuliana Cardillo Arianna Gennari Luca Gentilucci Elisa Mosconi Alessandra Tolomelli Stefano Troisi 《Tetrahedron: Asymmetry》2010,21(1):96-102
The reactivity of both the ester and amine functions present in β-amino esters was tested in order to obtain the synthesis of enantiopure αvβ3 and α5β1 integrin ligands. CaLB successfully catalyzed both the enantioselective transesterification and the N-acylation of racemic β-amino esters, allowing the isolation of intermediates for the preparation of Arg-Gly-Asp (RGD) mimetic compounds. In particular, a CaLB-catalyzed amidation reaction with unprotected p-aminobenzylamine reduced the number of synthetic steps, thus avoiding protection and deprotection of the intermediate compounds. Following this procedure, RGD mimetics were isolated with high yields and enantiomeric purities. 相似文献