全文获取类型
收费全文 | 401篇 |
免费 | 30篇 |
国内免费 | 8篇 |
专业分类
化学 | 260篇 |
晶体学 | 3篇 |
力学 | 17篇 |
数学 | 56篇 |
物理学 | 103篇 |
出版年
2023年 | 2篇 |
2022年 | 13篇 |
2021年 | 17篇 |
2020年 | 22篇 |
2019年 | 28篇 |
2018年 | 36篇 |
2017年 | 16篇 |
2016年 | 27篇 |
2015年 | 17篇 |
2014年 | 35篇 |
2013年 | 59篇 |
2012年 | 30篇 |
2011年 | 14篇 |
2010年 | 15篇 |
2009年 | 15篇 |
2008年 | 12篇 |
2007年 | 19篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1997年 | 5篇 |
1988年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 3篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有439条查询结果,搜索用时 31 毫秒
21.
Different benzylic hydrocarbons are oxidized by tetrapyridinesilver(II) peroxydisulfate in refluxing acetonitrile to produce their corresponding carbonyl compounds in moderate to excellent yields. 相似文献
22.
23.
24.
Benzylic alcohols react efficiently with nitriles in the presence of silica gel supported ferric perchlorate to produce amides in high yields. 相似文献
25.
The synthesis of several novel three-dentate sulfonamide alcohol ligands is described, starting from camphorsulfonyl chloride. The influence of temperature and ligand structure on the asymmetric addition of dietylzinc to aromatic aldehydes has been studied. Enantioselectivities up to 76% have been obtained. 相似文献
26.
Mohammad Ali Zolfigol Peyman Salehi Arash Ghorbani-Choghamarani Maliheh Safaiee Mozhgan Shahamirian 《合成通讯》2013,43(11):1817-1823
Silica chromate easily converts 1,4‐dihydropyridines to their corresponding pyridines in the presence of NaHSO4 · H2O and wet SiO2 in dichloromethane at room temperature in good to excellent yields. 相似文献
27.
A three-component condensation reaction between 2-aminobenzophenone derivatives, formaldehyde or aromatic aldehydes, and ammonium acetate efficiently provides substituted quinazolines in a one-pot reaction in the presence of Brönsted acidic ionic liquid, 1-methylimidazolium triflouroacetate ([Hmim]TFA), in conjunction with aerobic oxidation. The ionic liquid was separated from the reaction mixture by simple extraction and was recycled three times without considerable loss in activity. 相似文献
28.
A new and efficient method to synthesize a 3,3,6,6,9‐aryl‐1,8‐dioxo‐octahydroxanthene derivative using diammonium hydrogen phosphate as catalyst was performed in water at room temperature in a short periods. 相似文献
29.
Saeed Balalaie Morteza Bararjanian Masoumeh Sheikh‐Ahmadi Shohreh Hekmat Peyman Salehi 《合成通讯》2013,43(7):1097-1108
Diammonium hydrogen phosphate was used as a mild, efficient, neutral, and cheap catalyst for the synthesis of various 4H‐benzo[b]pyran derivatives via a one‐pot, three‐component condensation of aromatic aldehydes, active methylene compounds, and dimedone in aqueous media. 相似文献
30.
Mahsa Taghavi Sirous Ebrahimi Jafarsadegh Moghaddas 《Journal of Dispersion Science and Technology》2014,35(8):1097-1105
The recently developed centrifugal impeller is examined to investigate the solid–liquid mixing in a mechanically agitated contactor. Using the sample withdrawal method, the effects of impeller geometrical parameters, impeller rotational speed (200–700 rpm), solid particle size (500–1100 µm), and solid loading (2–10 vol%) on the degree of homogeneity are studied. The axial and the radial solid concentration profiles and the minimum impeller speed for the complete homogenization are also determined. In comparison with a widely used propeller impeller, considerably higher homogeneity values in lower impeller speeds are obtained (90% homogeneity against 16% homogeneity at 200 rpm at the same conditions). Having also lower power consumption makes this a superior impeller in solid–liquid mixing processes especially in shear-sensitive systems. 相似文献