全文获取类型
收费全文 | 249779篇 |
免费 | 2804篇 |
国内免费 | 867篇 |
专业分类
化学 | 124657篇 |
晶体学 | 3725篇 |
力学 | 10945篇 |
综合类 | 17篇 |
数学 | 34698篇 |
物理学 | 79408篇 |
出版年
2021年 | 1879篇 |
2020年 | 2125篇 |
2019年 | 2315篇 |
2018年 | 4245篇 |
2017年 | 4357篇 |
2016年 | 5231篇 |
2015年 | 3406篇 |
2014年 | 4677篇 |
2013年 | 11033篇 |
2012年 | 11316篇 |
2011年 | 12105篇 |
2010年 | 8292篇 |
2009年 | 7876篇 |
2008年 | 9534篇 |
2007年 | 9726篇 |
2006年 | 9260篇 |
2005年 | 11996篇 |
2004年 | 10907篇 |
2003年 | 8454篇 |
2002年 | 6499篇 |
2001年 | 7056篇 |
2000年 | 5391篇 |
1999年 | 4205篇 |
1998年 | 3335篇 |
1997年 | 3294篇 |
1996年 | 3098篇 |
1995年 | 2829篇 |
1994年 | 2712篇 |
1993年 | 2528篇 |
1992年 | 3004篇 |
1991年 | 2954篇 |
1990年 | 2863篇 |
1989年 | 2625篇 |
1988年 | 2660篇 |
1987年 | 2622篇 |
1986年 | 2439篇 |
1985年 | 3178篇 |
1984年 | 3417篇 |
1983年 | 2766篇 |
1982年 | 2932篇 |
1981年 | 2913篇 |
1980年 | 2775篇 |
1979年 | 2848篇 |
1978年 | 2934篇 |
1977年 | 2932篇 |
1976年 | 3038篇 |
1975年 | 2792篇 |
1974年 | 2736篇 |
1973年 | 2886篇 |
1972年 | 1832篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
101.
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
102.
103.
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
104.
Prof. Piotr Bałczewski Dr. Emilia Kowalska Dr. Ewa Różycka-Sokołowska Dr. Joanna Skalik Dr. Krzysztof Owsianik Dr. Marek Koprowski Dr. Bernard Marciniak Dr. Dariusz Guziejewski Prof. Witold Ciesielski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(62):14148-14161
The highly substituted mono-aryl/alkylthio-(hetero)acenes prepared in this study have been found to be thermally more stable (Tdecomp.=331–354 °C) than the known di-aryl/alkylthio-substituted acenes by an average of 25 °C. They are also much more photostable at 254 and 365 nm (in both argon and air) than the parent anthracene and other reported anthracenes. The most photostable aryl/alkylthio-anthracenes at 254 nm were found to be 60–70 (in air) and 130 (in argon) times more stable in solution than the unsubstituted anthracene, and much more stable than known EDG/EWG-substituted anthracenes (EDG=electron-donating group, EWG=electron-withdrawing group) with an extended aromatic core. Furthermore, the acenes showed significantly higher photostability at 365 nm in both air and argon. The anthracenes were obtained by the novel thio-Friedel–Crafts/Bradsher cyclization reaction of hitherto unknown [o-(1,3-dithian-2-yl)aryl](aryl)methyl thioethers. The developed approach provides a general access to mono-aryl/alkylthio-substituted (hetero)acene frameworks containing at least three fused (hetero)aromatic rings. The characteristic feature of this approach, which leads to highly substituted acenes, is that the substituents, unlike in other methods, may be introduced at an early stage of the synthesis. DFT and TD-DFT calculations confirmed the stabilizing role of the aryl/alkylthio substituent in the mono-aryl/alkylthio-substituted anthracenes, which are the most stable anthracenes prepared to date. Their high photostability is mainly due to the quenching of singlet oxygen by the acene and the quenching of the acene S1 state by molecular oxygen. 相似文献
105.
106.
107.
108.
109.
Tereshchenko E. D. Cherniakov S. M. Yurik R. Yu. Rietveld M. T. Häggström I. 《Radiophysics and Quantum Electronics》2020,62(10):667-676
Radiophysics and Quantum Electronics - We present the results of comparing the total electron content measurements based on GLONASS satellite signals and the EISCAT UHF incoherent scatter radar... 相似文献
110.
Brandão Pedro Francisco Ramos Rui Miguel Rodrigues José António 《Analytical and bioanalytical chemistry》2018,410(26):6873-6880
Analytical and Bioanalytical Chemistry - Formaldehyde is often applied in the industrial production of different products, such as textiles, insulation materials, or cosmetics, due to its... 相似文献