全文获取类型
收费全文 | 39504篇 |
免费 | 1839篇 |
国内免费 | 4083篇 |
专业分类
化学 | 23171篇 |
晶体学 | 1162篇 |
力学 | 661篇 |
综合类 | 258篇 |
数学 | 13770篇 |
物理学 | 6404篇 |
出版年
2024年 | 25篇 |
2023年 | 256篇 |
2022年 | 974篇 |
2021年 | 873篇 |
2020年 | 681篇 |
2019年 | 915篇 |
2018年 | 831篇 |
2017年 | 845篇 |
2016年 | 884篇 |
2015年 | 830篇 |
2014年 | 1362篇 |
2013年 | 2632篇 |
2012年 | 1797篇 |
2011年 | 2528篇 |
2010年 | 2351篇 |
2009年 | 2770篇 |
2008年 | 2781篇 |
2007年 | 2824篇 |
2006年 | 2485篇 |
2005年 | 2080篇 |
2004年 | 1973篇 |
2003年 | 1658篇 |
2002年 | 1412篇 |
2001年 | 1016篇 |
2000年 | 1013篇 |
1999年 | 831篇 |
1998年 | 778篇 |
1997年 | 663篇 |
1996年 | 685篇 |
1995年 | 635篇 |
1994年 | 606篇 |
1993年 | 554篇 |
1992年 | 487篇 |
1991年 | 337篇 |
1990年 | 229篇 |
1989年 | 260篇 |
1988年 | 210篇 |
1987年 | 173篇 |
1986年 | 149篇 |
1985年 | 192篇 |
1984年 | 161篇 |
1983年 | 74篇 |
1982年 | 112篇 |
1981年 | 118篇 |
1980年 | 86篇 |
1979年 | 56篇 |
1978年 | 56篇 |
1977年 | 61篇 |
1976年 | 40篇 |
1974年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
71.
M. M. Kabachnic E. V. Zobnina V. Yu. Pavlov I. O. Konstantinov G. V. Ponomarev I. P. Beletskaya 《Russian Chemical Bulletin》2005,54(1):262-265
A preparative procedure is proposed for the synthesis of α-aminophosphonates of natural porphyrins by the microwave-assisted Kabachnik—Fields reaction.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 256–259, January, 2005. 相似文献
72.
JIANG Qi-Jun 《结构化学》2005,24(10):1140-1144
1 INTRODUCTION The electron-transfer reaction of C60 derivatives, especially light-induced electron-transfer reaction, has been an active research field for a long time. Many researches are focused on the long-live charge- separated state caused by electron-transfer[1]. And several electron-transfers between electron donor and C60 or intramolecular electron-transfer have been confirmed. As an example, TTF-C60 is proved to be a short-live charge-separated compound[2].Due to the excelle… 相似文献
73.
István Szatmári 《Tetrahedron letters》2006,47(23):3881-3883
As a new extension of the Mannich reaction of naphthols, 1-(hydroxynaphthyl)-substituted 1,2,3,4-tetrahydroisoquinolines were synthesized by the nucleophilic addition of 1- or 2-naphthol to 3,4-dihydroisoquinolines under solvent-free conditions, using microwave irradiation. The additions to 3-methyl-6,7-dimethoxy-3,4-dihydroisoquinoline proved to be a highly diastereoselective processes, resulting in the cis isomers as the main or the only products. 相似文献
74.
M. Z. Krimer F. Z. Makaev Yu. B. Kal'yan V. P. Tashchi Yu. G. Putsykin 《Russian Chemical Bulletin》1993,42(12):1995-2000
O-Methyloximes and nitrones of a series of substituted 4-[2-hydroxy-2-(1H-1,2,4-triazol-1-ylmethyl)cyclohexylidenemethyl]benzaldehydes have been synthesized, and their fungicidal activity has been assayed. All of them exhibit low fungicidal activity in thein vitro assays and high activity in thein vivo assays; theO-methyl oximes are more active than the corresponding nitrones.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2082–2087, December, 1993. 相似文献
75.
N. E. Golantsov A. V. Karchava M. A. Yurovskaya 《Chemistry of Heterocyclic Compounds》2006,42(8):1021-1024
Methods of obtaining ketones and enamino esters have been developed on the basis of reactions of 1-(1-phenylethyl)indole-2-carbonitrile
with organomagnesium and organozinc compounds. Removal of a benzyl group from the indole nitrogen atom by the Grignard reagent
has been discovered.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1179–1183, August, 2006. 相似文献
76.
α-Halogeno ethers, sulfides, and amines are reactive compounds which can be used for the formation of new C? C bonds, either as nucleophilic or as electrophilic reagents, or by α-elimination. The use of these compounds in the synthesis of many classes of organic compounds is reviewed. 相似文献
77.
J. P. Dassaud B. Gallot A. Guyot R. Spitz J. P. Beautemps C. Williams C. Bourgaux A. Eisenberg 《先进技术聚合物》1994,5(2):79-89
Polypropylene ionomers have been prepared by sulfonation of copolymers of propene and 7 methyl, 1-6 octadiene, followed by neutralization to cesium salts. Both WAXS and SAXS were used to study the morphology of the samples, while their thermal properties were studied by DSC and their mechanical properties by DMTA. The sulfonation process is shown to cause a further drop in crystallinity in addition to the effect of comonomer incorporation. Ion clustering is observed when the extent of sulfonation is high enough, the limit being dependent on the copolymer composition. The ion pairs which are not incorporated into the cluster cause a small-angle upturn in the WAXS pattern. The mechanical properties are strongly affected by the drop in crystallinity, but may be partly recovered due to ion clustering. No disruption of the ion clusters is observed before thermal decomposition of the polymer. 相似文献
78.
维生素B12缺乏致神经损害临床分析 总被引:2,自引:0,他引:2
维生素B12缺乏多继发于胃肠道外科手术后、贫血及其它内科疾病,其引起的神经系统损害临床表现多样,主要为周围神经损害及亚急性联合变性。测定维生素B1:值、查肌电图等可明确诊断。补充维生素B12治疗有效。 相似文献
79.
80.
S. G. Zlotin M. V. Sharashkina Yu. A. Strelenko O. A. Luk'yanov M. O. Dekaprilevich Yu. T. Struchkav 《Russian Chemical Bulletin》1994,43(7):1220-1226
Methods for the synthesis of polyfunctionalN-phosphoryl- andN-phosphonoyldiazeneN-oxides containing hydroxyl, acetoxyl, and nitrate groups, and dibromoallyl and dibromopropyl fragments have been developed. The molecular structure ofN-(2,2-dimethyl-5-nitro-1,3-dioxan-5-yl)-N-[methoxy(phenyl)phosphoryl)diazeneN-oxide was established by X-ray structural analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1284–1289, July, 1994. 相似文献