全文获取类型
收费全文 | 2410篇 |
免费 | 85篇 |
国内免费 | 9篇 |
专业分类
化学 | 1517篇 |
晶体学 | 5篇 |
力学 | 40篇 |
数学 | 405篇 |
物理学 | 537篇 |
出版年
2023年 | 17篇 |
2021年 | 64篇 |
2020年 | 62篇 |
2019年 | 73篇 |
2018年 | 70篇 |
2017年 | 39篇 |
2016年 | 90篇 |
2015年 | 58篇 |
2014年 | 91篇 |
2013年 | 121篇 |
2012年 | 151篇 |
2011年 | 163篇 |
2010年 | 97篇 |
2009年 | 105篇 |
2008年 | 112篇 |
2007年 | 103篇 |
2006年 | 96篇 |
2005年 | 95篇 |
2004年 | 64篇 |
2003年 | 59篇 |
2002年 | 51篇 |
2001年 | 18篇 |
2000年 | 15篇 |
1999年 | 21篇 |
1998年 | 14篇 |
1997年 | 15篇 |
1995年 | 19篇 |
1994年 | 9篇 |
1993年 | 12篇 |
1992年 | 17篇 |
1991年 | 18篇 |
1989年 | 14篇 |
1984年 | 15篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1979年 | 21篇 |
1978年 | 13篇 |
1977年 | 16篇 |
1976年 | 21篇 |
1975年 | 20篇 |
1974年 | 10篇 |
1957年 | 13篇 |
1956年 | 17篇 |
1955年 | 11篇 |
1954年 | 14篇 |
1934年 | 9篇 |
1929年 | 9篇 |
1927年 | 11篇 |
1924年 | 9篇 |
1907年 | 11篇 |
排序方式: 共有2504条查询结果,搜索用时 16 毫秒
1.
Rodolfo Sánchez Angela Braeuning-Demian Jan Glorius Siegbert Hagmann Pierre-Michel Hillenbrand Anton Kalinin Thomas Köhler Yuri A. Litvinov Nikolaos Petridis Shahab Sanjari Uwe Spillmann Thomas Stöhlker 《X射线光谱测定》2020,49(1):33-36
The atomic physics collaboration SPARC is a part of the APPA pillar at the future Facility for Antiproton and Ion Research. It aims at atomic-physics research across virtually the full range of atomic matter. An emphasis of this contribution are the atomic physics experiments addressing the collision dynamics in strong electro-magnetic fields as well as the fundamental interactions between electrons and heavy nuclei at the HESR. Here we give a short overview about the central instruments for SPARC experiments at this storage ring. 相似文献
2.
3.
4.
Galia Pozina Elizaveta I. Girshova Konstantin M. Morozov Konstantin A. Ivanov Anton Yu. Egorov Mikhail A. Kaliteevski 《Annalen der Physik》2019,531(6)
Enhancement of spontaneous emission in a resonant Bragg quantum well (QW) structure with 60 periods of triple InAs monolayers embedded in a GaAs matrix is studied experimentally and theoretically. From measurements of the time‐resolved photoluminescence, besides the QW exciton at 1.47 eV, a specific super‐radiant (SR) emission demonstrating nonlinear properties is found. The SR mode shows a near‐quadratic dependence of intensity on excitation power, while its energy position follows the Bragg condition. It is revealed that the SR mode shows a peculiar non‐monotonic dependence of intensity on direction, with a maximum observed at approximately 40°. The enhancement in the SR emission at a specific direction is correlated well with suggested theoretical consideration of the modal Purcell factor for periodic quantum well structures. 相似文献
5.
6.
Edward A. Karakhanov Anton L. Maximov Anna V. Zolotukhina Nadezhda Yatmanova Edward Rosenberg 《应用有机金属化学》2015,29(11):777-784
A series of Pd–Ag mixed‐metal nanocatalysts were prepared by reduction of Pd–Ag salts in the presence of poly(propylene imine) dendrimers, which were covalently bound to the surface of a silica polyamine composite, BP‐1 (polyallylamine covalently bound to a silanized amorphous silica gel). Three different Pd‐to‐Ag ratios were evaluated (50:50, catalyst 1 ; 40:60, catalyst 2 ; 60:40, catalyst 3 ) with the goal of determining how the amount of Ag effects selectivity, rate and conversion in the selective reduction of alkynes, such as phenylacetylene and 1‐ or 4‐octyne, to the corresponding alkenes. Conditions for the catalysis are reported where there is improved selectivity without a serious reduction in rate when compared with the analogous Pd‐only catalysts. Catalyst 2 worked best for phenylacetylene and catalyst 3 worked best for the octynes. The catalysts could be reused seven times without loss of activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
8.
Anton M. Zeitlin 《Letters in Mathematical Physics》2015,105(2):149-167
9.
Prof. Dr. Antonín Klásek Assoc. Prof. Dr. Stanislav Kafka Dr. Ondřej Rudolf Prof. Dr. Antonín Lyčka Dr. Michal Rouchal Lukáš Bednář 《ChemistryOpen》2021,10(6):645-652
3-Chloroquinoline-2,4-diones react with cyanide ions in dimethyl formamide to give 3-cyanoquinoline-2,4-diones in small yields due to the strong hindrance of the substituent at the C-3 atom. Good yields can be achieved if the substituent at this position is the methyl group. In the methanol solution, the reaction proceeds by an addition mechanism to form 2-oxo-1a,2,3,7b-tetrahydrooxireno[2,3-c]quinoline-7b-carbonitriles, from which 4-hydroxy-3-methoxy-2-oxo-1,2,3,4-tetrahydroquinoline-4-carbonitriles are subsequently formed by opening of the epoxide ring with methanol. Some minor products of these reactions have also been isolated. The 1H, 13C and 15N NMR spectra of the prepared compounds were measured, and all resonances were assigned using appropriate two-dimensional spectra. 相似文献
10.
Jin Tanaka Yu Shibata Anton Joseph Juntaro Nogami Jyunichi Terasawa Ryo Yoshimura Prof. Dr. Ken Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(26):5774-5779
It has been established that a newly developed cyclopentadienyl rhodium(III) [CpARhIII] complex, bearing an acidic secondary amide moiety on the Cp ring, is able to catalyze the ortho-bromination of O-phenyl carbamates with N-bromosuccinimide (NBS) at room temperature. The presence of the acidic secondary amide moiety on the CpA ligand accelerates the bromination by the hydrogen bond between the acidic NH group of the CpA ligand and the carbonyl group of NBS. 相似文献