全文获取类型
收费全文 | 2065篇 |
免费 | 343篇 |
国内免费 | 270篇 |
专业分类
化学 | 1512篇 |
晶体学 | 34篇 |
力学 | 128篇 |
综合类 | 34篇 |
数学 | 185篇 |
物理学 | 785篇 |
出版年
2024年 | 6篇 |
2023年 | 41篇 |
2022年 | 73篇 |
2021年 | 66篇 |
2020年 | 103篇 |
2019年 | 77篇 |
2018年 | 73篇 |
2017年 | 47篇 |
2016年 | 95篇 |
2015年 | 75篇 |
2014年 | 91篇 |
2013年 | 129篇 |
2012年 | 189篇 |
2011年 | 167篇 |
2010年 | 119篇 |
2009年 | 107篇 |
2008年 | 125篇 |
2007年 | 115篇 |
2006年 | 93篇 |
2005年 | 108篇 |
2004年 | 75篇 |
2003年 | 48篇 |
2002年 | 63篇 |
2001年 | 33篇 |
2000年 | 34篇 |
1999年 | 49篇 |
1998年 | 48篇 |
1997年 | 45篇 |
1996年 | 57篇 |
1995年 | 42篇 |
1994年 | 51篇 |
1993年 | 53篇 |
1992年 | 31篇 |
1991年 | 31篇 |
1990年 | 30篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 14篇 |
1986年 | 20篇 |
1985年 | 13篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有2678条查询结果,搜索用时 31 毫秒
181.
182.
Pu Zhang Rongqiang Zhuang Zhide Guo Prof. Xinhui Su Prof. Xiaoyuan Chen Prof. Xianzhong Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16783-16786
A convenient and quantitative radioiodination method by copper‐mediated cross‐coupling of aryl boronic acids was developed. The mild labeling conditions, ready availability of the boronic acid substrate, simple operation, broad functional group tolerance and excellent radiochemical yield (RCY) make this a practical strategy for radioiodine labeling without further purification. 相似文献
183.
Spectral feature with sub-natural linewidth due to quantum interference in a four-level system 下载免费PDF全文
This paper studies the narrow spectral feature appearing in a four-level system coupled by two strong coherent fields and probed by a weak laser field. The linewidth is examined as a function of the Rabi frequencies of coupling fields, and the result is explained by using the dressed-state formalism. 相似文献
184.
185.
186.
J. Q.?ShenEmail author S.?He F.?Zhuang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,33(1):35-38
The molecular Aharonov-Carmi (A-C) effect is considered for
C60 molecules. It is shown that the valence electrons in
rapidly rotating C60 molecules acquire an A-C phase shift,
which is proportional to the molecular angular velocity flux
enclosed by the valence-electron matter wave on the C60 molecular shell. The energy shift of the valence electrons due to both the molecular rapid rotation and the molecular A-C phase
shift is calculated. 相似文献
187.
Bis-sulfonamides are demonstrated to be promising candidates for the efficient activation of carbonyl compounds through hydrogen bonding. Exemplified by three carbonyl addition reactions: Mukaiyama-aldol, hetero Diels-Alder and Friedel-Crafts reactions we show that bis-triflamides or bis-nonaflamides of commercially available chiral diamines act as chiral Br?nsted-acid catalysts, leading to the optically active products in moderate to excellent yields and with enantioselectivities up to 73% ee. 相似文献
188.
[reaction: see text] Hydrozirconation of terminal alkynes, followed by AgClO4-catalyzed in situ addition of the resultant alkenylzirconocenes to 1,2-anhydrosugars (glycal epoxides) leads to alpha-C-glycosides in moderate to high yields. 相似文献
189.
We report the observation of hybrid optoelectronic bistability in a fiber Bragg grating (FBG) by use of an electro-optically tuned cw fiber laser in which another wavelength-matched FBG is employed to constitute a tunable resonant cavity. The potential application of such a device as a fiber-optic sensor is also discussed. 相似文献
190.
A novel approach to the synthesis of 6-amino-7-hydroxy-flavone 总被引:1,自引:0,他引:1
A novel approach to the synthesis of 6-amino-7-hydroxyflavone (1) is described. Reaction in acetone of 2',4'-dihydroxy-5'-nitroacetophenone and benzoyl chloride in the presence of potassium carbonate affords 3-benzoyl-7-hydroxy-6-nitroflavone, which is cleaved in 5% ethanolic potassium hydroxide to give 1-(2,4-dihydroxy-5-nitrophenyl)-3- phenyl-1,3-propanedione. The 1,3-diketone thus formed is then transformed into 7-hydroxy- 6-nitroflavone, followed by reduction to afford the title compound. 相似文献