全文获取类型
收费全文 | 783篇 |
免费 | 177篇 |
国内免费 | 83篇 |
专业分类
化学 | 314篇 |
晶体学 | 14篇 |
力学 | 7篇 |
综合类 | 5篇 |
数学 | 22篇 |
物理学 | 681篇 |
出版年
2024年 | 5篇 |
2023年 | 6篇 |
2022年 | 47篇 |
2021年 | 35篇 |
2020年 | 56篇 |
2019年 | 20篇 |
2018年 | 17篇 |
2017年 | 29篇 |
2016年 | 44篇 |
2015年 | 29篇 |
2014年 | 45篇 |
2013年 | 57篇 |
2012年 | 53篇 |
2011年 | 49篇 |
2010年 | 40篇 |
2009年 | 62篇 |
2008年 | 60篇 |
2007年 | 60篇 |
2006年 | 38篇 |
2005年 | 38篇 |
2004年 | 35篇 |
2003年 | 33篇 |
2002年 | 28篇 |
2001年 | 34篇 |
2000年 | 22篇 |
1999年 | 17篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有1043条查询结果,搜索用时 9 毫秒
61.
Yoshitane Imai Kakuhiro Kawaguchi Tomohiro Sato Michiya Fujiki Yoshio Matsubara 《Tetrahedron letters》2007,48(16):2927-2930
By using (1R,2R)-1,2-diphenylethylenediamine as a chiral molecule and 2-anthracenecarboxylic acid as a fluorescent molecule, we created a chiral supramolecular organic fluorophore having circularly polarized luminescence properties in the solid-state. 相似文献
62.
V. I. Baranovski E. N. Pisarevskaya O. V. Vinogradova O. V. Sverdlova I. A. Balova 《Russian Chemical Bulletin》2007,56(10):2014-2020
The results of experimental and theoretical investigation of the electronic absorption spectra of substituted phenyldiacethylenes
are presented. The bands in the experimental spectra were assigned in detail using quantum chemical calculations of the electronic
structures and spectra of the molecules. The influence of the interaction of the substituents on the spectral parameters of
the systems under study was analyzed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1947–1953, October, 2007. 相似文献
63.
Jian‐Gong Yang Kai Li Jian Wang Shanshan Sun Weijie Chi Chao Wang Xiaoyong Chang Chao Zou Wai‐Pong To Ming‐De Li Xiaogang Liu Wei Lu Hong‐Xing Zhang Chi‐Ming Che Yong Chen 《Angewandte Chemie (International ed. in English)》2020,59(17):6915-6922
Materials exhibiting excitation wavelength‐dependent photoluminescence (Ex‐De PL) in the visible region have potential applications in bioimaging, optoelectronics and anti‐counterfeiting. Two multifunctional, chiral [Au(NHC)2][Au(CN)2] (NHC=(4R,5R)/(4S,5S)‐1,3‐dimethyl‐4,5‐diphenyl‐4,5‐dihydro‐imidazolin‐2‐ylidene) complex double salts display Ex‐De circularly polarized luminescence (CPL) in doped polymer films and in ground powder. Emission maxima can be dynamically tuned from 440 to 530 nm by changing the excitation wavelength. The continuously tunable photoluminescence is proposed to originate from multiple emissive excited states as a result of the existence of varied AuI???AuI distances in ground state. The steric properties of the NHC ligand are crucial to the tuning of AuI???AuI distances. An anti‐counterfeiting application using these two salts is demonstrated. 相似文献
64.
Chihiro Maeda Keiji Nagahata Takuma Shirakawa Tadashi Ema 《Angewandte Chemie (International ed. in English)》2020,59(20):7813-7817
Helical carbazole‐based BODIPY analogues were readily synthesized via aza[7]helicenes. The structures of azahelicene‐incorporated BF2 dyes were elucidated by x‐ray diffraction analysis. DFT calculations revealed that the π‐conjugated system expanded from the helicene moiety to the BODIPY framework. The azahelicene‐fused boron complexes showed the Cotton effects and the circularly polarized luminescence (CPL) in the visible region. Furthermore, an axially chiral binaphthyl group was attached to the helically chiral dyes, which enhanced the chiroptical properties. 相似文献
65.
Sudhir Kumar Keshri Atsuro Takai Tomoya Ishizuka Takahiko Kojima Masayuki Takeuchi 《Angewandte Chemie (International ed. in English)》2020,59(13):5254-5258
The design and synthesis of an enantiomeric pair of 1,8‐diethynylanthracene‐bridged naphthalenediimide (NDI)‐based cyclophanes ( Cyclo‐NDI s) are reported. Each enantiomer of Cyclo‐NDI exhibits a circularly polarized luminescence signal with a relatively large luminescence dissymmetry factor (glum=±8×10?3). We have further investigated the modulation of through‐space electronic communication between co‐facially oriented NDIs in a discrete Cyclo‐NDI with changes in the temperature. Tuning of the electronic communication results from the conformational transformation of monomer‐ versus dimer‐like features of Cyclo‐NDI , as confirmed by UV/Vis, fluorescence, circular dichroic, and NMR spectroscopic analysis. The temperature‐dependent optical response in the Cyclo‐NDI through the conformational transformation could be utilized as a highly sensitive and reversible optical thermometer in a wide temperature range (100 to ?80 °C). 相似文献
66.
67.
Suzuka Kinoshita Ryota Yamano Dr. Yu Shibata Yusuke Tanaka Kyoichi Hanada Dr. Takashi Matsumoto Prof. Dr. Kazunori Miyamoto Dr. Atsuya Muranaka Prof. Dr. Masanobu Uchiyama Prof. Dr. Ken Tanaka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):11113-11120
An S-shaped double helicene-like molecule (>99 % ee), possessing stable helical chirality, has been synthesized by the rhodium(I)/difluorphos complex-catalyzed highly diastereo- and enantioselective intramolecular double [2+2+2] cycloaddition of a 2-naphthol- and benzene-linked hexayne. The collision between two terminal naphthalene rings destabilizes the helical chirality of the S-shaped double helicene-like molecule, but the introduction of two additional fused benzene rings significantly increases the configurational stability. Thus, no epimerization and racemization were observed even at 100 °C. The enantiopure S-shaped double helicene-like molecule forms a trimer through the multiple C−H⋅⋅⋅π and C−H⋅⋅⋅O interactions in the solid-state. The trimers stack to form columnar packing structures, in which neighboring stacks have opposite dipole directions. The accumulation of helical structures in the same direction in the S-shaped double helicene-like molecule enhanced the chiroptical properties. 相似文献
68.
基于晶态纳米纤维素禁带效应的圆偏振荧光能力,分别采用混合悬浮液法及多层膜叠加法拓宽了晶态纳米纤维素膜的禁带,使其禁带覆盖可见光范围,通过掺杂多色荧光体,该膜可以将自发辐射转换为高强度、右旋、多色的圆偏振荧光信号. 相似文献
69.
70.
Kyoichi Hanada Juntaro Nogami Prof. Dr. Kazunori Miyamoto Norihiko Hayase Dr. Yuki Nagashima Yusuke Tanaka Dr. Atsuya Muranaka Prof. Dr. Masanobu Uchiyama Prof. Dr. Ken Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9313-9319
The enantioselective synthesis of aza[6] and [7]helicene-like molecules have been achieved by the cationic rhodium(I)/axially chiral biaryl bisphosphine complex-catalyzed intramolecular [2+2+2] cycloaddition of cyanodiynes. This protocol was successfully applied to the diastereo- and enantioselective synthesis of an S-shaped double aza[6]helicene-like molecule with a high ee value of 89 %. Although no epimerization and racemization were observed in the double carbo[6]helicene-like molecule at 80 °C, epimerization and racemization of the double aza[6]helicene-like molecule proceeded at 80 °C. This double aza[6]helicene-like molecule showed good fluorescent quantum yields and chiroptical responses under both neutral and acidic conditions. 相似文献