全文获取类型
收费全文 | 256043篇 |
免费 | 4737篇 |
国内免费 | 1355篇 |
专业分类
化学 | 135394篇 |
晶体学 | 3484篇 |
力学 | 10408篇 |
综合类 | 55篇 |
数学 | 32069篇 |
物理学 | 80725篇 |
出版年
2021年 | 2400篇 |
2020年 | 2783篇 |
2019年 | 2932篇 |
2018年 | 3853篇 |
2017年 | 3652篇 |
2016年 | 5801篇 |
2015年 | 3992篇 |
2014年 | 5394篇 |
2013年 | 12642篇 |
2012年 | 10744篇 |
2011年 | 12119篇 |
2010年 | 8263篇 |
2009年 | 7894篇 |
2008年 | 10753篇 |
2007年 | 10700篇 |
2006年 | 10028篇 |
2005年 | 9203篇 |
2004年 | 8340篇 |
2003年 | 7170篇 |
2002年 | 6885篇 |
2001年 | 7442篇 |
2000年 | 6000篇 |
1999年 | 4583篇 |
1998年 | 3673篇 |
1997年 | 3576篇 |
1996年 | 3445篇 |
1995年 | 3147篇 |
1994年 | 3049篇 |
1993年 | 2851篇 |
1992年 | 3229篇 |
1991年 | 3117篇 |
1990年 | 3065篇 |
1989年 | 2767篇 |
1988年 | 2831篇 |
1987年 | 2789篇 |
1986年 | 2611篇 |
1985年 | 3403篇 |
1984年 | 3621篇 |
1983年 | 2944篇 |
1982年 | 3078篇 |
1981年 | 3041篇 |
1980年 | 2849篇 |
1979年 | 2956篇 |
1978年 | 3050篇 |
1977年 | 3058篇 |
1976年 | 3126篇 |
1975年 | 2878篇 |
1974年 | 2866篇 |
1973年 | 2999篇 |
1972年 | 1887篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
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
132.
133.
Sh. M. Khaliullin V. D. Zhuravlev V. G. Bamburov L. V. Ermakova 《Physics of Atomic Nuclei》2015,78(12):1382-1388
Submicron CaZrO3 powder is obtained in combustion reactions (solution combustion synthesis—SCS) with glycine. It is found that SCS reduces the sintering temperature of CaZrO3 powders. The dielectric properties of calcium zirconate ceramics are studied by the electrochemical impedance method. It is shown that a ceramics of powders obtained by the SCS method has high dielectric characteristics. 相似文献
134.
Ling-Yang Hsu Qiumin Liang Zhiheng Wang Hsin-Hung Kuo Wun-Shan Tai Shi-Jian Su Xiuwen Zhou Yi Yuan Yun Chi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(67):15375-15386
Iridium complexes bearing chelating cyclometalates are popular choices as dopant emitters in the fabrication of organic light-emitting diodes (OLEDs). In this contribution, we report a series of blue-emitting, bis-tridentate IrIII complexes bearing chelates with two fused five-six-membered metallacycles, which are in sharp contrast to the traditional designs of tridentate chelates that form the alternative, fused five-five metallacycles. Five IrIII complexes, Px-21 – 23 , Cz-4 , and Cz-5 , have been synthesized that contain a coordinated dicarbene pincer chelate incorporating a methylene spacer and a dianionic chromophoric chelate possessing either a phenoxy or carbazolyl appendage to tune the coordination arrangement. All these tridentate chelates afford peripheral ligand–metal–ligand bite angles of 166–170°, which are larger than the typical bite angle of 153–155° observed for their five-five-coordinated tridentate counterparts, thereby leading to reduced geometrical distortion in the octahedral frameworks. Photophysical measurements and TD-DFT studies verified the inherent transition characteristics that give rise to high emission efficiency, and photodegradation experiments confirmed the improved stability in comparison with the benchmark fac-[Ir(ppy)3] in degassed toluene at room temperature. Phosphorescent OLED devices were also fabricated, among which the carbazolyl-functionalized emitter Cz-5 exhibited the best performance among all the studied bis-tridentate phosphors, showing a maximum external quantum efficiency (EQEmax) of 18.7 % and CIEx,y coordinates of (0.145, 0.218), with a slightly reduced EQE of 13.7 % at 100 cd m−2 due to efficiency roll-off. 相似文献
135.
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
136.
137.
138.
139.
140.
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