全文获取类型
收费全文 | 1040篇 |
免费 | 53篇 |
国内免费 | 6篇 |
专业分类
化学 | 908篇 |
晶体学 | 3篇 |
力学 | 22篇 |
数学 | 27篇 |
物理学 | 139篇 |
出版年
2023年 | 13篇 |
2022年 | 5篇 |
2021年 | 15篇 |
2020年 | 29篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 8篇 |
2016年 | 24篇 |
2015年 | 19篇 |
2014年 | 28篇 |
2013年 | 30篇 |
2012年 | 47篇 |
2011年 | 67篇 |
2010年 | 26篇 |
2009年 | 33篇 |
2008年 | 48篇 |
2007年 | 49篇 |
2006年 | 62篇 |
2005年 | 66篇 |
2004年 | 49篇 |
2003年 | 30篇 |
2002年 | 49篇 |
2001年 | 44篇 |
2000年 | 29篇 |
1999年 | 19篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1992年 | 18篇 |
1991年 | 13篇 |
1990年 | 17篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1979年 | 15篇 |
1977年 | 8篇 |
1976年 | 12篇 |
1975年 | 6篇 |
1974年 | 15篇 |
1973年 | 9篇 |
1972年 | 5篇 |
1971年 | 5篇 |
1967年 | 7篇 |
排序方式: 共有1099条查询结果,搜索用时 671 毫秒
61.
Selective Generation of Formamides through Photocatalytic CO2 Reduction Catalyzed by Ruthenium Carbonyl Compounds
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Katsuaki Kobayashi Dr. Takashi Kikuchi Prof. Susumu Kitagawa Prof. Koji Tanaka 《Angewandte Chemie (International ed. in English)》2014,53(44):11813-11817
The selective formation of dialkyl formamides through photochemical CO2 reduction was developed as a means of utilizing CO2 as a C1 building block. Photochemical CO2 reduction catalyzed by a [Ru(bpy)2(CO)2]2+ (bpy: 2,2′‐bipyridyl)/[Ru(bpy)3]2+/Me2NH/Me2NH2+ system in CH3CN selectively produced dimethylformamide. In this process a ruthenium carbamoyl complex ([Ru(bpy)2(CO)(CONMe2)]+) formed by the nucleophilic attack of Me2NH on [Ru(bpy)2(CO)2]2+ worked as the precursor to DMF. Thus Me2NH acted as both the sacrificial electron donor and the substrate, while Me2NH2+ functioned as the proton source. Similar photochemical CO2 reductions using R2NH and R2NH2+ (R=Et, nPr, or nBu) also afforded the corresponding dialkyl formamides (R2NCHO) together with HCOOH as a by‐product. The main product from the CO2 reduction transitioned from R2NCHO to HCOOH with increases in the alkyl chain length of the R2NH. The selectivity between R2NCHO and HCOOH was found to depend on the rate of [Ru(bpy)2(CO)(CONR2)]+ formation. 相似文献
62.
Dr. Ming-Shui Yao Prof. Jia-Jia Zheng Ai-Qian Wu Prof. Gang Xu Sanjog S. Nagarkar Gen Zhang Masahiko Tsujimoto Prof. Shigeyoshi Sakaki Prof. Satoshi Horike Prof. Kenichi Otake Prof. Susumu Kitagawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(1):178-182
Single-ligand-based electronically conductive porous coordination polymers/metal–organic frameworks (EC-PCPs/MOFs) fail to meet the requirements of numerous electronic applications owing to their limited tunability in terms of both conductivity and topology. In this study, a new 2D π-conjugated EC-MOF containing copper units with mixed trigonal ligands was developed: Cu3(HHTP)(THQ) (HHTP=2,3,6,7,10,11-hexahydrotriphenylene, THQ=tetrahydroxy-1,4-quinone). The modulated conductivity (σ≈2.53×10−5 S cm−1 with an activation energy of 0.30 eV) and high porosity (ca. 441.2 m2 g−1) of the Cu3(HHTP)(THQ) semiconductive nanowires provided an appropriate resistance baseline and highly accessible areas for the development of an excellent chemiresistive gas sensor. 相似文献
63.
Ming‐Shui Yao Jia‐Jia Zheng Ai‐Qian Wu Gang Xu Sanjog S. Nagarkar Gen Zhang Masahiko Tsujimoto Shigeyoshi Sakaki Satoshi Horike Kenichi Otake Susumu Kitagawa 《Angewandte Chemie (International ed. in English)》2020,59(1):172-176
Single‐ligand‐based electronically conductive porous coordination polymers/metal–organic frameworks (EC‐PCPs/MOFs) fail to meet the requirements of numerous electronic applications owing to their limited tunability in terms of both conductivity and topology. In this study, a new 2D π‐conjugated EC‐MOF containing copper units with mixed trigonal ligands was developed: Cu3(HHTP)(THQ) (HHTP=2,3,6,7,10,11‐hexahydrotriphenylene, THQ=tetrahydroxy‐1,4‐quinone). The modulated conductivity (σ≈2.53×10?5 S cm?1 with an activation energy of 0.30 eV) and high porosity (ca. 441.2 m2 g?1) of the Cu3(HHTP)(THQ) semiconductive nanowires provided an appropriate resistance baseline and highly accessible areas for the development of an excellent chemiresistive gas sensor. 相似文献
64.
65.
Akihiro Kitashoji Kosei Kitagawa Dr. Akimasa Fujihara Prof. Dr. Tomoyuki Yatsuhashi 《Chemphyschem》2020,21(9):847-852
A multiply charged molecule expands the range of a mass window and is utilized as a precursor to provide rich sequence coverage; however, reflectron time-of-flight mass spectrometer has not been well applied to the product ion analysis of multiply charged precursor ions. Here, we demonstrate that the range of the mass-to-charge ratio of measurable product ions is limited in the cases of multiply charged precursor ions. We choose C6F6 as a model molecule to investigate the reactions of multiply charged molecular cations formed in intense femtosecond laser fields. Measurements of the time-of-flight spectrum of C6F6 by changing the potential applied to the reflectron, combined with simulation of the ion trajectory, can identify the species detected behind the reflectron as the neutral species and/or ions formed by the collisional charge transfer. Moreover, the metastable ion dissociations of doubly and triply charged C6F6 are identified. The detection of product ions in this manner can diminish interference by the precursor ion. Moreover, it does not need precursor ion separation before product ion analysis. These advantages would expand the capability of mass spectrometry to obtain information about metastable ion dissociation of multiply charged species. 相似文献
66.
Ryosuke Matsui Erina Niijima Tomomi Imai Hiroyuki Kobayashi Akiko Hori Azusa Sato Yuko Nakamura Osamu Kitagawa 《Molecules (Basel, Switzerland)》2022,27(7)
The halogen bond has been widely used as an important supramolecular tool in various research areas. However, there are relatively few studies on halogen bonding related to molecular chirality. 3-(2-Halophenyl)quinazoline-4-thione derivatives have stable atropisomeric structures due to the rotational restriction around an N-C single bond. In X-ray single crystal structures of the racemic and optically pure N-C axially chiral quinazoline-4-thiones, we found that different types of intermolecular halogen bonds (C=S⋯X) are formed. That is, in the racemic crystals, the intermolecular halogen bond between the ortho-halogen atom and sulfur atom was found to be oriented in a periplanar conformation toward the thiocarbonyl plane, leading to a syndiotactic zig-zag array. On the other hand, the halogen bond in the enantiomerically pure crystals was oriented orthogonally toward the thiocarbonyl plane, resulting in the formation of a homochiral dimer. These results indicate that the corresponding racemic and optically pure forms in chiral molecules are expected to display different halogen bonding properties, respectively, and should be separately studied as different chemical entities. 相似文献
67.
Tsuneo Imamoto Masatoshi Matsuo Taro Nonomura Kuniyuki Kishikawa Masao Yanagawa 《Heteroatom Chemistry》1993,4(5):475-486
Cyclohexyl(o-methoxyphenyl)menthyloxyphosphineborane and t-butyl(o-methoxyphenyl)menthyloxyphosphine-borane were prepared from dichlorocyclohexylphosphine and t-butyldichlorophosphine by successive treatments with (−)-menthol, o-methoxyphenylmagnesium bromide, and borane-THF complex. The separated pure diastereomers of each of the compounds underwent reaction with lithium naphthalenide to afford optically pure cyclohexyl(o-methoxyphenyl)phosphine-borane and t-butyl(o-methoxyphenyl)phosphine-borane, respectively. These secondary phosphine-boranes reacted readily with various electrophiles in the presence of bases with virtually net retention of configuration. A new chiral phosphine ligand, (S,S)-1,2-bis[cyclohexyl(o-methoxyphenyl)phosphino]ethane was synthesized via the optically pure phosphine-boranes. 相似文献
68.
Shusuke Yamanaka Keita Kanda Toru Saito Yasutaka Kitagawa Takashi Kawakami Masahiro Ehara Mitsutaka Okumura Haruki Nakamura Kizashi Yamaguchi 《Chemical physics letters》2012
We assessed the applicability and basis set dependency of the B3LYP functional to investigate magnetic interactions of Mn complexes. For the purpose, we constructed a test set consisting of 16 Mn complexes with various oxidation states and structural motifs.The B3LYP results correctly reproduced magnetism and magneto–redox correlation of the standard μ-oxo motifs with superexchange paths, while it does not work for weak magnetic complexes. We also showed that a modest basis set yields results similar to those of triple-zeta plus diffuse-and-polarization functions. This basis set is expected to be a standard basis set for investigating magnetism of manganese complexes. 相似文献
69.
Functional porous coordination polymers 总被引:18,自引:0,他引:18
The chemistry of the coordination polymers has in recent years advanced extensively, affording various architectures, which are constructed from a variety of molecular building blocks with different interactions between them. The next challenge is the chemical and physical functionalization of these architectures, through the porous properties of the frameworks. This review concentrates on three aspects of coordination polymers: 1). the use of crystal engineering to construct porous frameworks from connectors and linkers ("nanospace engineering"), 2). characterizing and cataloging the porous properties by functions for storage, exchange, separation, etc., and 3). the next generation of porous functions based on dynamic crystal transformations caused by guest molecules or physical stimuli. Our aim is to present the state of the art chemistry and physics of and in the micropores of porous coordination polymers. 相似文献
70.
Kawahara M Kabir MK Yamada K Adachi K Kumagai H Narumi Y Kindo K Kitagawa S Kawata S 《Inorganic chemistry》2004,43(1):92-100
Two new copper(II) compounds of chloranilate and 2,2':6',2' '-terpyridine have been synthesized, and the structures have been solved by the single-crystal X-ray diffraction method. The crystal structure of [[Cu(2)(CA)(terpy)(2)][Cu(CA)(2)]](n)(1), where H(2)CA = chloranilic acid and terpy = 2,2':6',2' '-terpyridine, consists of two modules, the dimer unit [Cu(2)(CA)(terpy)(2)](2+) and the anionic mononuclear unit [Cu(CA)(2)](2)(-), forming an alternated chain. The chain is stabilized by semicoordinating and additional but efficient secondary bonding interactions. The crystal structure of [[Cu(2)(CA)(terpy)(2)(dmso)(2)][Cu(CA)(2)(dmso)(2)](EtOH)](n)(2), where dmso = dimethyl sulfoxide, consists of solvent molecules and two discrete modules, the dimer unit [Cu(2)(CA)(terpy)(2)(dmso)(2)](2+) and the anionic mononuclear unit [Cu(CA)(2)(dmso)(2)](2)(-). The dimer units form a layer by secondary bonding interactions, and the monomer units and ethanol molecules are introduced between the layers. The magnetic properties of 1 and 2 have been investigated in the temperature range 2.0-300 K. A weak ferromagnetic interaction was observed in 1, J(a) = 2.36 cm(-)(1) and zJ(b) = -0.68 cm(-)(1) while no exchange coupling was observed in 2. 相似文献