全文获取类型
收费全文 | 408篇 |
免费 | 22篇 |
专业分类
化学 | 370篇 |
晶体学 | 4篇 |
力学 | 2篇 |
数学 | 5篇 |
物理学 | 49篇 |
出版年
2023年 | 5篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 13篇 |
2013年 | 20篇 |
2012年 | 31篇 |
2011年 | 24篇 |
2010年 | 12篇 |
2009年 | 10篇 |
2008年 | 34篇 |
2007年 | 14篇 |
2006年 | 41篇 |
2005年 | 37篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 20篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有430条查询结果,搜索用时 140 毫秒
71.
Otsuki J Imai A Sato K Li DM Hosoda M Owa M Akasaka T Yoshikawa I Araki K Suenobu T Fukuzumi S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(9):2709-2718
A star-shaped Ru/Os tetranuclear complex, in which a central Os unit is linked to three peripheral Ru units by 4,4'-azobis(2,2'-bipyridine) (azobpy) bridging ligands, was prepared to examine the unique photodynamics regulated by its redox state. The Ru/Os tetranuclear complex exhibits Ru-based luminescence at 77 K, whereas the three-electron reduction (one for each azobpy) of the Ru/Os complex results in luminescence from the Os unit. The photoexcited state of the Ru/Os complex rapidly decays into low energy metal-to-ligand charge-transfer states, in which the excited electron is localized in the azobpy ligand in the form of azobpy(.-). Upon the one-electron reduction of the azobpy ligands, the above-mentioned low-energy states become unavailable to the photoexcited complex. As a result, an energy transfer from the Ru-based excited state to the Os-based excited state becomes possible. Ultrafast transient absorption measurements revealed that the energy transfer process consists of two steps; intramolecular electron transfer from the terminal bipyridine ligand (bpy(.-)) to form azobpy(2-) followed by a metal-to-metal electron transfer. Thus, the Ru/Os tetranuclear complex collects light energy into the central Os unit depending on the redox state of the bridging ligands, qualifying as a switchable antenna. 相似文献
72.
Watanabe K Makino R Takahashi H Iguchi K Ohrui H Akasaka K 《Chemical & pharmaceutical bulletin》2008,56(6):861-863
A new unsaturated fatty acid with unique vicinal dimethyl branches was isolated from the Okinawan soft coral of the genus Sinularia. The structure of the compound was determined based on the results of spectroscopic analysis and chemical conversion. The absolute configuration was deduced by applying the Ohrui-Akasaka method. 相似文献
73.
Arashiba K Iizuka H Matsukawa S Kuwata S Tanabe Y Iwasaki M Ishii Y 《Inorganic chemistry》2008,47(10):4264-4274
The reaction of the group 9 bis(hydrosulfido) complexes [Cp*M(SH)2(PMe3)] (M=Rh, Ir; Cp*=eta(5)-C 5Me5) with the group 6 nitrosyl complexes [Cp*M'Cl2(NO)] (M'=Mo, W) in the presence of NEt3 affords a series of bis(sulfido)-bridged early-late heterobimetallic (ELHB) complexes [Cp*M(PMe3)(mu-S)2M'(NO)Cp*] (2a, M=Rh, M'=Mo; 2b, M=Rh, M'=W; 3a, M=Ir, M'=Mo; 3b, M=Ir, M'=W). Similar reactions of the group 10 bis(hydrosulfido) complexes [M(SH)2(dppe)] (M=Pd, Pt; dppe=Ph 2P(CH2) 2PPh2), [Pt(SH)2(dppp)] (dppp=Ph2P(CH2) 3PPh2), and [M(SH)2(dpmb)] (dpmb=o-C6H4(CH2PPh2)2) give the group 10-group 6 ELHB complexes [(dppe)M(mu-S)2M'(NO)Cp*] (M=Pd, Pt; M'=Mo, W), [(dppp)Pt(mu-S)2M'(NO)Cp*] (6a, M'=Mo; 6b, M'=W), and [(dpmb)M(mu-S)2M'(NO)Cp*] (M=Pd, Pt; M'=Mo, W), respectively. Cyclic voltammetric measurements reveal that these ELHB complexes undergo reversible one-electron oxidation at the group 6 metal center, which is consistent with isolation of the single-electron oxidation products [Cp*M(PMe3)(mu-S)2M'(NO)Cp*][PF6] (M=Rh, Ir; M'=Mo, W). Upon treatment of 2b and 3b with ROTf (R=Me, Et; OTf=OSO 2CF 3), the O atom of the terminal nitrosyl ligand is readily alkylated to form the alkoxyimido complexes such as [Cp*Rh(PMe3)(mu-S)2W(NOMe)Cp*][OTf]. In contrast, methylation of the Rh-, Ir-, and Pt-Mo complexes 2a, 3a, and 6a results in S-methylation, giving the methanethiolato complexes [Cp*M(PMe3)(mu-SMe)(mu-S)Mo(NO)Cp*][BPh 4] (M=Rh, Ir) and [(dppp)Pt(mu-SMe)(mu-S)Mo(NO)Cp*][OTf], respectively. The Pt-W complex 6b undergoes either S- or O-methylation to form a mixture of [(dppp)Pt(mu-SMe)(mu-S)W(NO)Cp*][OTf] and [(dppp)Pt(mu-S) 2W(NOMe)Cp*][OTf]. These observations indicate that O-alkylation and one-electron oxidation of the dinuclear nitrosyl complexes are facilitated by a common effect, i.e., donation of electrons from the group 9 or 10 metal center, where the group 9 metals behave as the more effective electron donor. 相似文献
74.
Calix[4]arene-plumbylene complexes Pb[Calixt-Bu(O)2(OR)2], where R=benzyl, 9-fluorenyl, SitBuMe2, and SiiPr3, have been synthesized by the reaction of Lappert's plumbylene Pb[N(SiMe3)2]2 with the corresponding 1,3-diethers of calix[4]arene. The products have been fully characterized by 1H, 13C{1H}, and 207Pb NMR spectroscopy, elemental analysis, and X-ray diffraction analysis. The products adopt two different forms depending on the R groups: the alkyl derivatives were obtained as exo-isomers in which the lead atom resides outside the cavity of the calix[4]arene, while the silyl derivatives were isolated as endo-isomers where the lead atom is situated inside the cavity. X-ray diffraction studies revealed that the lead(II) atoms in the exo- and endo-isomers are coordinated by the ethereal oxygen atoms (OR) and the aromatic rings (ArOR), respectively, which are maintained in solution as evidenced by 207Pb NMR studies. 相似文献
75.
Isolation and Crystallographic Characterization of the Labile Isomer of Y@C82 Cocrystallized with Ni(OEP): Unprecedented Dimerization of Pristine Metallofullerenes
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)
Lipiao Bao Changwang Pan Prof. Zdenek Slanina Prof. Filip Uhlik Prof. Takeshi Akasaka Prof. Xing Lu 《Angewandte Chemie (International ed. in English)》2016,55(32):9234-9238
Although the major isomers of M@C82 (namely M@C2v(9)‐C82, where M is a trivalent rare‐earth metal) have been intensively investigated, the lability of the minor isomers has meant that they have been little studied. Herein, the first isolation and crystallographic characterization of the minor Y@C82 isomer, unambiguously assigned as Y@Cs(6)‐C82 by cocrystallization with Ni(octaethylporphyrin), is reported. Unexpectedly, a regioselective dimerization is observed in the crystalline state of Y@Cs(6)‐C82. In sharp contrast, no dimerization occurs for the major isomer Y@C2v(9)‐C82 under the same conditions, indicating a cage‐symmetry‐induced dimerization process. Further experimental and theoretical results disclose that the regioselective dimer formation is a consequence of the localization of high spin density on a special cage‐carbon atom of Y@Cs(6)‐C82 which is caused by the steady displacement of the Y atom inside the Cs(6)‐C82 cage. 相似文献
76.
77.
Shigeru Nagase Kaoru Kobayashi Takeshi Akasaka 《Journal of computational chemistry》1998,19(2):232-239
The structural determination of endohedral metallofullerenes has attracted special attention in disclosing the formation mechanism and developing new routes to bulk production. Recent advances in the theoretical and experimental studies are summarized with representative mono- and dimetallofullerenes such as M@C82 (M=Ca, Sc, Y, and La), Sc2@C84, and La2@C80. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 232–239, 1998 相似文献
78.
79.
80.
Eight normal fatty acids and 24 cyclamenaldehydes were analyzed based on the molecular orbital theory using Computer-Aided Chemistry Programs (CAChe Programs) with PM3 parameters. We found reactive sites with high values of electrophilic frontier densities (EFDs) at appointed positions in both molecules. EFD is a theoretical index that predicts reactive sites acting as electron donors. A change in the values of EFDs in normal fatty acids would account for the selectivity in the response of a single olfactory receptor cell to the fatty acids. Changes in the values of EFDs at appointed positions of cyclamenaldehydes also correlated with their odor characteristics and intensities. This fact indicates that cyclamenaldehydes have common reactive sites that play a critical role in interactions with a receptor. Changes in their reactivities alter the odor characteristics and intensities of the molecules judged by perfumers, indicating that human discrimination of cyclamenaldehyde odor is determined at the stage of interaction between cyclamenaldehydes and an odor receptor. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 79: 101–108, 2000 相似文献