全文获取类型
收费全文 | 2582篇 |
免费 | 87篇 |
国内免费 | 362篇 |
专业分类
化学 | 2576篇 |
晶体学 | 20篇 |
力学 | 4篇 |
综合类 | 13篇 |
数学 | 106篇 |
物理学 | 312篇 |
出版年
2024年 | 1篇 |
2023年 | 77篇 |
2022年 | 55篇 |
2021年 | 72篇 |
2020年 | 102篇 |
2019年 | 84篇 |
2018年 | 94篇 |
2017年 | 135篇 |
2016年 | 135篇 |
2015年 | 82篇 |
2014年 | 151篇 |
2013年 | 463篇 |
2012年 | 253篇 |
2011年 | 155篇 |
2010年 | 130篇 |
2009年 | 137篇 |
2008年 | 141篇 |
2007年 | 150篇 |
2006年 | 141篇 |
2005年 | 124篇 |
2004年 | 128篇 |
2003年 | 79篇 |
2002年 | 18篇 |
2001年 | 11篇 |
2000年 | 5篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有3031条查询结果,搜索用时 15 毫秒
911.
o-Carboxyhomomaleanilic acids (5) and o-carboxyhomophthalanilic acids (6) on treatment with sodium acetate-acetic anhydride furnished pyridobenzoxazinones (8) and isoquinolinobenzoxazinones (9) respectively in quantitative yields. Conversion of o-formylhomophthalanilic acid (7) to isocoumarinoquinoline (11) via 2-axo-3(o-carboxyphenyl)quinoline (10) is also described. 相似文献
912.
Majid M. Heravi Mansoureh Daraie Farahnaz K. Behbahani Reihaneh Malakooti 《合成通讯》2013,43(8):1180-1186
Aromatic aldehydes were reacted in a one-pot reaction with enolizable ketones, acetonitrile, and acetyl chloride in the presence of Mn(bpdo)2Cl2/MCM-41 under reflux condition or at 80 °C to afford the corresponding β-acetamido ketones in good yields. 相似文献
913.
An improved enantioselective synthesis of protected (3S,4S)-4-amino-3,5-dihydroxypentanoic acid (ADPA) from L-serine has been developed. Enantioselectivity is improved by replacing the methyl ester with the tert-butyl ester and using neutral magnesium salt of esters to give β-keto ester. 相似文献
914.
Initial formation of tetrahydrocarboline 3 from tryptophan methyl ester 1 and aldehyde 2 by Pictet–Spengler reaction, followed by treatment with trichlorocyanuric acid, provides a facile and efficient route for a one-pot synthesis of β-carbolines with excellent yields. 相似文献
915.
Usama Karama 《合成通讯》2013,43(23):3447-3451
(Carboethoxymethylene)triphenylphosphorane 1 can undergo the tandem reaction of iodination–oxidation–Wittig reaction with alcohol in the presence of N-iodosuccinimide (NIS) and manganese dioxide. The reaction constitutes a stereoselective one-pot procedure for the preparation of Z-configured α-iodo-α,β-unsaturated esters in good to excellent yield. 相似文献
916.
A new procedure for stereoselective synthesis of trisubstituted alkenes by an one-pot, three-component reaction of N-tosylated imines with α,β-acetylenic ketones and organozinc species CF3COOZnEt was described. This reaction system provides β-branched Morita–Baylis–Hillman adducts with excellent yields in absence of any catalyst. 相似文献
917.
Hantzsch 1,4-dihydropyridines undergo smooth aromatization oxidized by o-iodoxybenzoic acid (IBX) in water/acetone in the presence of β-cyclodextrin (β-CD) to afford the corresponding pyridine derivatives in excellent yields. The IBX and β-CD can be recycled and reused. 相似文献
918.
(Z)-α-Arylthio-α,β-unsaturated ketones can be stereoselectively synthesized in one pot under mild conditions, in good yields, by the palladium-catalyzed hydrostannylation of acetylenic sulfides with tributyltin hydride, followed by Stille coupling with acyl chlorides. 相似文献
919.
Aza-Michael adducts are obtained in very good yields by the conjugate addition of aliphatic amines to α,β-unsaturated compounds using molecular iodine as catalyst in dichloromethane at room temperature. Aromatic amines were found to be reactive under reflux in toluene. 相似文献
920.
Shi-Jie Zhang 《合成通讯》2013,43(20):3093-3100
Synthesis of (E)-β,γ-unsaturated acids from aldehydes with malonic acid has been explored under solvent-free conditions. The modified Knoevenagel condensation reaction with N-methyl morpholine (NMM) as catalyst exhibits highly β,γ-regioselectivity and exclusively E-stereoselectivity. A mechanism accounting for both regio- and stereoselectivity has been proposed and preliminarily studied. 相似文献