全文获取类型
收费全文 | 218339篇 |
免费 | 4821篇 |
国内免费 | 1424篇 |
专业分类
化学 | 121114篇 |
晶体学 | 2729篇 |
力学 | 8684篇 |
综合类 | 49篇 |
数学 | 26621篇 |
物理学 | 65387篇 |
出版年
2021年 | 1568篇 |
2020年 | 1975篇 |
2019年 | 1897篇 |
2018年 | 2216篇 |
2017年 | 2146篇 |
2016年 | 4131篇 |
2015年 | 3446篇 |
2014年 | 4048篇 |
2013年 | 10873篇 |
2012年 | 9294篇 |
2011年 | 10821篇 |
2010年 | 6826篇 |
2009年 | 6757篇 |
2008年 | 9730篇 |
2007年 | 9482篇 |
2006年 | 9020篇 |
2005年 | 8577篇 |
2004年 | 7626篇 |
2003年 | 6475篇 |
2002年 | 6246篇 |
2001年 | 6938篇 |
2000年 | 5509篇 |
1999年 | 4190篇 |
1998年 | 3196篇 |
1997年 | 3126篇 |
1996年 | 3225篇 |
1995年 | 2744篇 |
1994年 | 2721篇 |
1993年 | 2539篇 |
1992年 | 2869篇 |
1991年 | 2744篇 |
1990年 | 2491篇 |
1989年 | 2421篇 |
1988年 | 2420篇 |
1987年 | 2313篇 |
1986年 | 2209篇 |
1985年 | 3198篇 |
1984年 | 3148篇 |
1983年 | 2530篇 |
1982年 | 2711篇 |
1981年 | 2607篇 |
1980年 | 2504篇 |
1979年 | 2440篇 |
1978年 | 2504篇 |
1977年 | 2447篇 |
1976年 | 2404篇 |
1975年 | 2344篇 |
1974年 | 2265篇 |
1973年 | 2361篇 |
1972年 | 1339篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Immobilized Catalysts for Iridium‐Catalyzed Allylic Amination: Rate Enhancement by Immobilization 下载免费PDF全文
Dr. Chandi C. Malakar Prof. Dr. Günter Helmchen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7127-7134
The first immobilized catalyst for Ir‐catalyzed asymmetric allylic aminations is described. The catalyst is a cationic (π‐allyl)Ir complex bound by cation exchange to an anionic silica gel support. Preparation of the catalyst is facile, and the supported catalyst displayed considerably enhanced activity compared with the parent homogeneous catalyst. Up to 43 consecutive amination runs were possible in recycling experiments. 相似文献
92.
Synthesis,Electronic Properties and WOLED Devices of Planar Phosphorus‐Containing Polycyclic Aromatic Hydrocarbons 下载免费PDF全文
Dr. François Riobé Rózsa Szűcs Dr. Pierre‐Antoine Bouit Dr. Denis Tondelier Bernard Geffroy Fátima Aparicio Julia Buendía Prof. Luis Sánchez Prof. Régis Réau Prof. László Nyulászi Prof. Muriel Hissler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6547-6556
We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P‐containing PAHs exhibit properties expected for an emitter in white organic light‐emitting diodes (WOLEDs). 相似文献
93.
94.
Susana Estopiñá-Durán Liam J. Donnelly Euan B. Mclean Bryony M. Hockin Prof. Alexandra M. Z. Slawin Dr. James E. Taylor 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(15):3950-3956
A combination of pentafluorophenylboronic acid and oxalic acid catalyses the dehydrative substitution of benzylic alcohols with a second alcohol to form new C−O bonds. This method has been applied to the intermolecular substitution of benzylic alcohols to form symmetrical ethers, intramolecular cyclisations of diols to form aryl-substituted tetrahydrofuran and tetrahydropyran derivatives, and intermolecular crossed-etherification reactions between two different alcohols. Mechanistic control experiments have identified a potential catalytic intermediate formed between the aryl boronic acid and oxalic acid. 相似文献
95.
96.
97.
L. Resse L.G.S. Oliveira C.I.L. de Araujo A.R. Pereira R.L. Silva 《Physics letters. A》2019,383(14):1655-1659
In this work, we have used the MuMax3 software to simulate devices consisting of a ferromagnetic thin film placed over a heavy metal thin film. The devices are two interconnected partial-disks where a Néel domain wall is formed in the disks junction. In our simulations we investigate devices with disk radius nm and different distance d between the disks centers (from nm to nm). By applying strong sinusoidal external magnetic fields, we find a mechanism able to create, annihilate and even manipulate a skyrmion in each side of the device. This mechanism is discussed in terms of interactions between skyrmion and domain wall. The Néel domain wall formed in the center of the device interacts with the Néel skyrmion, leading to a process of transporting a skyrmion from one disk to the other periodically. Our results have relevance for potential applications in spintronics such as logical devices. 相似文献
98.
99.
100.
Ortiz Adolfo Yang Jianhua Coccolo Mattia Seoane Jesús M. Sanjuán Miguel A. F. 《Nonlinear dynamics》2020,102(4):2323-2337
Nonlinear Dynamics - The main purpose of this paper is to study both the underdamped and the overdamped dynamics of the nonlinear Helmholtz oscillator with a fractional-order damping. For that... 相似文献