全文获取类型
收费全文 | 305篇 |
免费 | 6篇 |
专业分类
化学 | 268篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 9篇 |
物理学 | 31篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 14篇 |
2012年 | 14篇 |
2011年 | 26篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 15篇 |
2007年 | 26篇 |
2006年 | 30篇 |
2005年 | 30篇 |
2004年 | 22篇 |
2003年 | 20篇 |
2002年 | 7篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有311条查询结果,搜索用时 0 毫秒
301.
Finefield JM Greshock TJ Sherman DH Tsukamoto S Williams RM 《Tetrahedron letters》2011,52(16):1987-1989
Notoamide E, a short-lived secondary metabolite, has been proposed as a biosynthetic intermediate to several advanced metabolites isolated from Aspergillus versicolor. In order to verify the role of this indole alkaloid along the biosynthetic pathway, synthetic doubly 13C-labeled notoamide E was fed to Aspergillus versicolor. Analysis of the metabolites showed significant incorporation of notoamide E into the natural products notoamides C and D. 相似文献
302.
Yumiko NagasawaHikaru Kato Henki Rotinsulu Remy E.P. MangindaanNicole J. de Voogd Sachiko Tsukamoto 《Tetrahedron letters》2011,52(41):5342-5344
Spironaamidine (1), a unique spiroquinone-containing alkaloid, was isolated from the marine sponge, Leucetta microraphis, along with two known imidazole alkaloids, naamidine H (2) and (9E)-clathridine 9-N-(2-sulfoethyl)imine (3). Spironaamidine (1) showed antimicrobial activity against Bacillus cereus. 相似文献
303.
Yumiko MatsutaTakayuki Kobari Sachiko KurashimaYuhsuke Kumakura Masashi ShinadaKazuhiro Higuchi Tomomi Kawasaki 《Tetrahedron letters》2011,52(46):6199-6202
An efficient approach to spirocyclic oxindole architecture with vicinal quaternary carbon centers is described. The reaction of 2-allyloxyindolin-3-ones with cyanomethylphosphonate at low reaction temperature proceeds smoothly with consecutive olefination, isomerization, deacylation, and anion-accelerated Claisen rearrangement to give the 3,3-disubstituted oxindoles with vicinal quaternary all-carbon centers in high yield and diastereoselectivity. The oxindoles are readily converted into more synthetically advanced spiro-products. 相似文献
304.
Ippei Kagiyama Dr. Hikaru Kato Dr. Tatsuo Nehira Prof. Jens C. Frisvad Prof. David H. Sherman Prof. Robert M. Williams Prof. Sachiko Tsukamoto 《Angewandte Chemie (International ed. in English)》2016,55(3):1128-1132
Seven new prenylated indole alkaloids, taichunamides A–G, were isolated from the fungus Aspergillus taichungensis (IBT 19404). Taichunamides A and B contained an azetidine and 4‐pyridone units, respectively, and are likely biosynthesized from notoamide S via (+)‐6‐epi‐stephacidin A. Taichunamides C and D contain endoperoxide and methylsulfonyl units, respectively. This fungus produced indole alkaloids containing an anti‐bicyclo[2.2.2]diazaoctane core, whereas A. protuberus and A. amoenus produced congeners with a syn‐bicyclo[2.2.2]diazaoctane core. Plausible biosynthetic pathways to access these cores within the three species likely arise from an intramolecular hetero Diels–Alder reaction. 相似文献
305.
A new colorimetric test (methyl red-DIC test) for monitoring the presence of hydroxyl groups on resins for use in solid-phase synthesis was developed. The resin became orange-red when the carboxyl group of methyl red formed ester linkages with the resin’s hydroxyl groups. This new test can be used not only for qualitative analysis but also quantitative analysis by using pictures of the relationship between color depth and hydroxy loading rates. 相似文献
306.
Collective Synthesis and Biological Evaluation of Tryptophan‐Based Dimeric Diketopiperazine Alkaloids 下载免费PDF全文
Shinji Tadano Yukihiro Sugimachi Prof. Dr. Michinori Sumimoto Prof. Dr. Sachiko Tsukamoto Prof. Dr. Hayato Ishikawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1277-1291
A concise two one‐pot synthesis of WIN 64821, eurocristatine, 15,15′‐bis‐epi‐eurocristatine, ditryptophenaline, ditryptoleucine A, WIN 64745, cristatumin C, asperdimin, naseseazine A, and naseseazine B is detailed, based on a unique bioinspired dimerization reaction of tryptophan derivatives in aqueous acidic solution and a one‐pot procedure for the construction of diketopiperazine rings. Total yields of these alkaloid syntheses were from 10 up to 27 %. In addition, 1′‐(2‐phenylethylene)‐ditryptophenaline was synthesized by using three one‐pot operations. The studies detailed herein provided synthesized natural products for inhibitory activities of ubiquitin‐specific protease 7 (USP7) and foam cell formation in macrophages. The newly listed biological evaluation for tryptophan‐based dimeric diketopiperazine alkaloids discovered 15,15′‐bis‐epi‐eurocristatine, 1′‐(2‐phenylethylene)‐ditryptophenaline, and WIN 64745 as new drug candidates. 相似文献
307.
Isao Yamaguchi Hideo Higashi Sachiko Shigesue Saki Shingai Moriyuki Sato 《Tetrahedron letters》2007,48(44):7778-7781
The pyridinium salts having reactive amine and/or pyridyl groups were obtained by the reaction using Zincke salts. Optical properties and anion exchange behavior of the obtained pyridinium salts were investigated. 相似文献
308.
309.
Murata K Toba T Nakanishi K Takahashi B Yamamura T Miyake S Annoura H 《The Journal of organic chemistry》2005,70(6):2398-2401
[reaction: see text] A practical and efficient total synthesis of (2S,3S,4R)-1-O-(alpha-d-galactosyl)-2-tetracosanoylamino-1,3,4-nonanetriol, OCH 1b, a potential therapeutic candidate for Th1-mediated autoimmune diseases, is described. The synthesis incorporates direct alkylation onto epoxide 5 and stereospecific halide ion catalyzed alpha-glycosidation reaction. A key intermediate 10 was obtained in only eight steps and 37% overall yield from commercially available d-arabitol 2, and the total synthesis of 1b was accomplished in 12 steps and 19% overall yield. This method will enable the synthesis of a variety of phytosphingolipids, especially that with the shorter sphingosine side chain than 1a, in a highly stereoselective manner. 相似文献
310.
Sachiko Kaihara Masatoshi Narikawa Keiji Fujimoto 《Colloid and polymer science》2012,290(13):1317-1325
Thermosensitive nanoparticles were prepared by mimicking protein folding where polymer aggregates were formed by precipitation of thermosensitive polymer chains followed by disulfide formation of their thiol groups. N-Isopropylacrylamide (NIPAM) and methacryloxy succinimide (SuMA) were co-polymerized and then cysteamine was allowed to react with succinimide moieties of the polymer to render thiol moieties. A polymer aqueous solution precipitated to form nano-sized aggregates by increasing temperature above its lower critical solution temperature (LCST), and their sizes were monodispersed and tunable by the polymer concentration. The aggregates were cross-linked to produce nanoparticles by oxidation of thiol groups in a manner similar to formation of a disulfide bond of protein. As a result, the cross-linked nanoparticles exhibited swelling by decreasing temperature below the LCST of the copolymer. Fluorescein and bovine serum albumin (BSA) were chosen as a small and a large substance, respectively, and were encapsulated into the swollen nanoparticles at 25?°C. Fluorescein was rapidly released from both swollen and shrunken nanoparticles. Although BSA exhibited little release at any temperatures, it was released from nanoparticles by adding the reducing agent to dissociate the disulfide cross-linking and incubating below the LCST. 相似文献