全文获取类型
收费全文 | 251篇 |
免费 | 5篇 |
专业分类
化学 | 161篇 |
晶体学 | 3篇 |
力学 | 8篇 |
数学 | 11篇 |
物理学 | 73篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 10篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 13篇 |
2013年 | 25篇 |
2012年 | 20篇 |
2011年 | 18篇 |
2010年 | 10篇 |
2009年 | 15篇 |
2008年 | 7篇 |
2007年 | 11篇 |
2006年 | 10篇 |
2005年 | 13篇 |
2004年 | 10篇 |
2003年 | 2篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 1篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有256条查询结果,搜索用时 15 毫秒
251.
M. Satish Kumar Y. Hemanth Sriram M. Venkateswarlu M. Sai Sudhakar Purugula Venkanna 《合成通讯》2018,48(1):59-67
Silica-supported perchloric acid and bisulfate (SiO2/HClO4 and SiO2/KHSO4) have been developed as reusable green catalysts for nitration of aromatic compounds using NaNO2 in acetonitrile medium under conventional and solvent-free microwave conditions. The reaction times under microwave irradiation are significantly shorter than conventional method even though the yields obtained in microwave-assisted reactions are comparable with those obtained under reflux conditions. 相似文献
252.
A novel and practical procedure for the synthesis of small molecules possessing beta-hydroxy or N-tosylamino 1,2,3-triazole motif by azidation of epoxides or N-tosylaziridines with sodium azide followed by "click reaction" using eco-friendly PEG-400 as a reaction medium in the presence of 5 mol % of CuI is described. Enantiomerically pure epoxide and N-tosylaziridines were afforded in high yield with excellent ee values maintaining complete stereospecificity. 相似文献
253.
Free-space optics (FSO) is a safe, license-free, high speed and high-bandwidth cordless technique for broadcasting signals at the same speed as fiber optics. But the main drawback of FSO is the dissolution of the signals due to atmospheric turbulence and thus degrading the link performance. So, to enhance the bit error rate (BER) performance, spatial diversity is employed over the FSO links for single-input multiple-output FSO (SIMO-FSO) systems. In this paper, we analyze the BER performance of SIMO-FSO links with spatial diversity and multiple-input multiple-output FSO (MIMO-FSO) systems over gamma–gamma atmospheric turbulence fading channel with misalignment (pointing errors). The closed form expressions are derived for the same with various combining schemes in terms of the Meijer G function and also evaluate the results with 2D and 3D graphs. 相似文献
254.
Madabhushi Sridhar Beeram C. Ramanaiah Chinthala Narsaiah Bellam Mahesh Mudam Kumaraswamy Kishore K.R. Mallu Vishnu M. Ankathi Pamulaparty Shanthan Rao 《Tetrahedron letters》2009,50(27):3897-6782
ZnCl2-catalyzed one-pot multicomponent synthesis of 2-amino-3,5-dicarbonitrile-6-thio-pyridines under microwave heating and conventional heating is described. 相似文献
255.
A simple, high yielding synthesis of pyrimidines from ketones in the presence of HMDS and formamide is described. Under microwave irradiation, heteroaromatic, aryl, aliphatic, and cyclic ketones cyclized to give pyrimidines in good yields. 相似文献
256.
Sriram Balasubramanian 《Integral Equations and Operator Theory》2010,68(4):529-550
We prove a Carathéodory–Fejér type interpolation theorem for certain matrix convex sets in mathbbCd{mathbb{C}^d} using the Blecher–Ruan–Sinclair characterization of abstract operator algebras. Our results generalize the work of Dmitry S. Kalyuzhnyĭ-Verbovetzkiĭ for the d-dimensional non-commutative polydisc. 相似文献