全文获取类型
收费全文 | 620篇 |
免费 | 28篇 |
国内免费 | 3篇 |
专业分类
化学 | 531篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 18篇 |
物理学 | 95篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 22篇 |
2014年 | 19篇 |
2013年 | 17篇 |
2012年 | 38篇 |
2011年 | 48篇 |
2010年 | 14篇 |
2009年 | 27篇 |
2008年 | 47篇 |
2007年 | 38篇 |
2006年 | 46篇 |
2005年 | 39篇 |
2004年 | 39篇 |
2003年 | 29篇 |
2002年 | 26篇 |
2001年 | 19篇 |
2000年 | 6篇 |
1999年 | 12篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 12篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1985年 | 7篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1968年 | 3篇 |
1961年 | 1篇 |
排序方式: 共有651条查询结果,搜索用时 833 毫秒
41.
Yuta Tsunoda Katsunori Fukuta Taisuke Imamura Prof. Dr. Ryo Sekiya Dr. Taniyuki Furuyama Prof. Dr. Nagao Kobayashi Prof. Dr. Takeharu Haino 《Angewandte Chemie (International ed. in English)》2014,53(28):7243-7247
Encapsulation of chiral guests in the dissymmetric capsule 1?4 BF4 formed diastereomeric supramolecular complexes G ? 1?4 BF4 ( G : guest). When chiral guests 2 a – q were encapsulated within the dissymmetric space of the self‐assembled capsule 1?4 BF4, circular dichroism (CD) was observed at the absorption bands that are characteristic of the π–π* transition of the bipyridine moiety of the capsule, which suggests that the P and M helicities of the capsule are biased by the chiral guest complexation. The P helicity of diastereomeric complex (S)‐ 2 l ? 1?4 BF4 was determined to be predominant, based on CD exciton coupling theory and DFT calculations. The diastereoselectivity was highly influenced by the ester substituents, such that benzyl ester moieties were good for improving the diastereoselectivity. A diastereomeric excess of 98 % was achieved upon the complexation of 2 j . The relative enthalpic and entropic components for the distereoselectivity were obtained from a van’t Hoff plot. The enthalpic components were linearly correlated with the substituent Hammett parameters (σp+). The electron‐rich benzyl ester moieties generated donor–acceptor π–π stacking interactions with the bipyridine moiety, which resulted in a significant difference in energy between the predominant and subordinate diastereomeric complexes. 相似文献
42.
Satoshi Nagao Ayaka Suda Hisashi Kobayashi Naoki Shibata Yoshiki Higuchi Shun Hirota 《化学:亚洲杂志》2020,15(11):1743-1749
Domain swapping is an exception to Anfinsen's dogma, and more than one structure can be produced from the same amino acid sequence by domain swapping. We have previously shown that myoglobin (Mb) can form a domain‐swapped dimer in which the hinge region is converted to a helical structure. In this study, we showed that domain‐swapped dimerization of Mb was achieved by a single Ala mutation of Gly at position 80. Multiple Ala mutations at positions 81 and 82 in addition to position 80 facilitated dimerization of Mb by stabilization of the dimeric states. Domain swapping tendencies correlated well with the helical propensity of the mutated residue in a series of Mb mutants with amino acids introduced to the hinge region. These findings demonstrate that a single mutation in the hinge loop to modify helical propensity can control oligomer formation, providing new ideas to create high‐order protein oligomers using domain swapping. 相似文献
43.
Takahiro Gunji Yukinori Nagao Takahisa Misono Yoshimoto Abe 《Journal of polymer science. Part A, Polymer chemistry》1992,30(3):371-377
From polytitanosiloxanes (PTS), SiO2–TiO2 oxide fibers with fairly good tensile strength were prepared, and their mechanical and thermal properties were investigated. The precursor fibers PTS-0.5 and PTS-1.0 were obtained by dry spinning of a highly viscous PTS solution which were formed as the reaction mixture of silicic acid (SA) with bis(2,4-pentanedionato)titanium diisopropoxide (PTP) in the molar ratios (SA/PTP) of 0.5 and 1.0. The precursor fibers PTS-0.5 were too brittle to measure their tensile strength, whereas PTS-1.0 and the heat-treated fibers were found to have tensile strength of 130 (precursor), 540 (500°C), and 450 (900°C) MPa, respectively. Heat-treatment of the fibers PTS-1.0 at above 1000°C forms anatase and rutile of titanium dioxide. The crystallization is resulted from the unreacted PTP which is not incorporated into the polymer network. 相似文献
44.
Yuzuru Uchida Katsumi Onoue Nobuaki Tada Fumio Nagao Hideaki Kozawa Shigeru Oae 《Heteroatom Chemistry》1990,1(4):295-306
Phosphine oxides bearing two or three 2-pyridyl groups react with organometallic reagents affording 2,2′-bipyridyl, 2-substituted pyridines and pyridine in good yields. Phosphonium salts and phosphine oxides, bearing at least two 2-pyridyl or substituted 2-pyridyl groups also give the corresponding 2,2′-bipyridyls and pyridines upon treatment with acid or neutral solvents such as water and alcohols in substantial yields. The 2,2′-bipyridyls are considered to be formed by ligand coupling within the pentacoordinated phosphorus intermediate formed incipiently during the reaction. 相似文献
45.
Atsuya Muranaka Yoshiaki Asano Akihiko Tsuda Atsuhiro Osuka Nagao Kobayashi 《Chemphyschem》2006,7(6):1235-1240
The electronic excited states of a meso-meso beta-beta doubly linked bis-porphyrin are comprehensively investigated by measuring its circular dichroism (CD) and magnetic circular dichroism (MCD) spectra. The observed spectroscopic properties are rationalized by DFT calculations. The frontier molecular orbitals (MOs) are constructed by the linear combinations of the constituent monomers' four MOs. Comparison of a theoretical CD spectrum based on time-dependent DFT (TDDFT) with the experimental spectra resulted in the assignment of the helical conformation of the dimer. This assignment is contrary to the previous assignment based on the point-dipole approximation (exciton coupling theory). 相似文献
46.
This paper describes the dynamics of a water-in-oil microemulsion from the dilute to the dense droplet region. Using the relative intermediate form factor method for neutron spin echo data analyses [M. Nagao, H. Seto, Phys. Rev. E 78 (2008) 011507], the shape and structure fluctuations of a droplet microemulsion are successfully decoupled. In the previous paper, we used the first cumulant analysis of the shape fluctuation model, while the full fitting form of the same model is applied in this paper. The final results of the fittings using the first cumulant approximation and the full form of the model are almost identical, and therefore, the validity of the method is strengthened. The estimated bending modulus of the surfactant membrane, κ, is basically the same, within the experimental errors, in the previous and present results. The κ is not affected much by an increase of the droplet concentration. A clear dynamic slowing down of the water droplets is highlighted at the length scale corresponding to the inter-droplet distance from the structure fluctuation analysis. 相似文献
47.
Front Cover: Construction of a Triangle‐Shaped Trimer and a Tetrahedron Using an α‐Helix‐Inserted Circular Permutant of Cytochrome c555 (Chem. Asian J. 10/2018)
下载免费PDF全文
![点击此处可从《化学:亚洲杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
48.
A method which preferentially produces adjacently di-aromatic ring-substituted tetraazaporphyrins (TAPs) has been developed, and their electrochemical and spectroscopic properties have been studied and compared with those of the corresponding series of mono-aromatic ring-fused TAPs. Mono-aromatic ring-fused TAPs show a split Q-band, and the splitting energy increases with increasing size of the aromatic ring. In addition, for the split Q-bands, the relative intensity of the band at longer wavelength decreases with increasing molecular size of the fused aromatics, compared with the shorter wavelength band. In the di-aromatic ring-fused TAPs, this kind of splitting is not seen, and only a shift of the band is observed. The intensity and band position of the split or unsplit Q-bands are quantitatively evaluated by simultaneous band deconvolution analysis, using both electronic absorption and magnetic circular dichroism spectra. The preparation of these TAP compounds has made it possible to adjust the Q-band position in a stepwise manner between ca. 600 and 750 nm. The first reduction and oxidation potentials of the TAP ring shift negatively with increasing number and size of the fused aromatics. The extent of the shift is found to be very small for the LUMOs but significant for the HOMOs. These spectroscopic and electrochemical properties are almost perfectly reproduced by molecular orbital calculations within the framework of the Pariser-Parr-Pople approximation. In particular, a small variation of the LUMO level and large destabilization of the HOMO level on ring expansion are rationalized from the extent of stretch of molecular orbitals: i.e., since the LUMOs are localized in the central TAP moiety irrespective of the molecular size, while the HOMOs have appreciable coefficients even over the fused aromatics, the HOMO level destabilizes while the LUMO level remains constant with increasing molecular size. In one CoTAP derivative, Co(III/II) and the first ligand oxidation couples occur experimentally at the same potential. 相似文献
49.
Fujikawa Y Akiyama K Nagao T Sakurai T Lagally MG Hashimoto T Morikawa Y Terakura K 《Physical review letters》2002,88(17):176101
The structure of Ge(105)-(1 x 2) grown on Si(105) is examined by scanning tunneling microscopy (STM) and first-principles calculations. The morphology evolution with an increasing amount of Ge deposited documents the existence of a tensile surface strain in Si(105) and its relaxation with increasing coverage of Ge. A detailed analysis of high-resolution STM images and first-principles calculations produce a new stable model for the Ge(105)-(1 x 2) structure formed on the Si(105) surface that includes the existence of surface strain. It corrects the model developed from early observations of the facets of "hut" clusters grown on Si(001). 相似文献
50.