全文获取类型
收费全文 | 331篇 |
免费 | 20篇 |
国内免费 | 2篇 |
专业分类
化学 | 236篇 |
晶体学 | 2篇 |
力学 | 20篇 |
数学 | 24篇 |
物理学 | 71篇 |
出版年
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 20篇 |
2019年 | 12篇 |
2018年 | 17篇 |
2017年 | 13篇 |
2016年 | 18篇 |
2015年 | 17篇 |
2014年 | 27篇 |
2013年 | 45篇 |
2012年 | 16篇 |
2011年 | 24篇 |
2010年 | 22篇 |
2009年 | 22篇 |
2008年 | 14篇 |
2007年 | 12篇 |
2006年 | 12篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1984年 | 1篇 |
1978年 | 1篇 |
1975年 | 3篇 |
排序方式: 共有353条查询结果,搜索用时 31 毫秒
1.
2.
Caesium carbonate supported on hydroxyapatite‐encapsulated Ni0.5Zn0.5Fe2O4 nanocrystallites as a novel magnetically basic catalyst for the one‐pot synthesis of pyrazolo[1,2‐b]phthalazine‐5,10‐diones 下载免费PDF全文
Behrooz Maleki Samaneh Barat Nam Chalaki Samaneh Sedigh Ashrafi Esmail Rezaee Seresht Farid Moeinpour Amir Khojastehnezhad Reza Tayebee 《应用有机金属化学》2015,29(5):290-295
A novel nanomagnetic basic catalyst of caesium carbonate supported on hydroxyapatite‐coated Ni0.5Zn0.5Fe2O4 magnetic nanoparticles (Ni0.5Zn0.5Fe2O4@HAP‐Cs2CO3) was prepared. This new catalyst was fully characterized using Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, X‐ray diffraction and vibrating sample magnetometry techniques, and then the catalytic activity of this catalyst was investigated in the synthesis of 1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐dione derivatives. Also, Ni0.5Zn0.5Fe2O4@HAP‐Cs2CO3 could be reused at least five times without significant loss of activity and could be recovered easily by applying an external magnet. Thus, the developed nanomagnetic catalyst is potentially useful for the green and economic production of organic compounds. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
3.
Echabaane M. Hfaiedh S. Smiri B. Saidi F. Dridi C. 《Journal of Solid State Electrochemistry》2021,25(6):1797-1806
Journal of Solid State Electrochemistry - The fast and sensitive detection of copper ions would be essential for water monitoring. Herein, we report a novel development of an impedimetric sensor... 相似文献
4.
5.
Treatment of aliphatic and aromatic aldehydes with chiral amines and trimethylsilyl cyanide in the absence or in the presence
of Lewis acids (including lithium perchlorate) under solvent-free conditions afforded the corresponding α-aminonitriles in
good yields and with a diastereoselectivity of 68 to 86%.
Published in Russian in Zhurnal Organicheskoi Khimii, 2006, Vol. 42, No. 1, pp. 56–59.
The text was submitted by the authors in English. 相似文献
6.
Iodine, was found to be a practical and novel catalyst for the reaction of aminal and trimethylsilyl cyanide under mild and neutral reaction condition to afford the corresponding α-aminonitriles in high yields and short reaction times. Trimethylsilyl iodide derived in situ from elemental iodine and trimethylsillyl cyanide catalyzed this conversion. 相似文献
7.
A highly regioselective ring opening of epoxides and aziridines can be carried out efficiently with acetic anhydride to form the acetates of the corresponding 1,2-diols and 2-amino-alcohols, respectively, using ammonium-12-molybdophosphate (AMP) as a heterogeneous catalyst, at room temperature, in the absence of solvent. 相似文献
8.
An efficient method for the enantioselective 1,4-conjugate addition of amines to α,β-unsaturated esters containing an inexpensive chiral auxiliary, such as (S)-2-methyl-1-butanol and fenchyl alcohol, in solvent-free conditions mediated by solid lithium perchlorate is reported. Over 12 examples of the products are generated in excellent yields, accompanied by moderate enantioselectivity. The concentrated solution of LiClO4 in a diethyl ether system works well for the enantioselective 1,4-addition of organolithium compounds to α,β-unsaturated amides without any side reactions. 相似文献
9.
Benarafa L Rghioui L Nejjar R Saidi Idrissi M Knidiri M Lorriaux A Wallart F 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(3):419-430
The monoclinic phosphates with K3Ln(PO4)2 (Ln=rare earth) formula were synthesized. Their infrared and Raman spectra have been reported and analysed. The results of a force field calculation for K3Nd(PO4)2 are presented. 相似文献
10.
An apparatus for thermal analysis operating up to 500°C temperature and up to 2 GPa, pressure using a conventional piston-cylinder device, is described.A few results concerning solid phases of the quaternary systems SiO2-Al2O3-M2O-H2O (M=Li, Na, K) studied under 2.108 Pa pressure, are discussed.
Zusammenfassung Es wird eine Apparatur für die Thermoanalyse bis 500°C und bis zum Druck von 2 GPa beschrieben. Dabei wird ein herkömmliches Kolben-Zylinder-Gerät verwendet. Einige Ergebnisse bezüglich der Festphasen des quaternären Systemes SiO2-Al2O3-M2O-H2O (M=Li, Na, K) bei einem Druck von 2·108 Pa wurden beschrieben.相似文献