全文获取类型
收费全文 | 686篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
化学 | 398篇 |
晶体学 | 3篇 |
力学 | 17篇 |
数学 | 141篇 |
物理学 | 141篇 |
出版年
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 15篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 20篇 |
2015年 | 8篇 |
2014年 | 17篇 |
2013年 | 15篇 |
2012年 | 42篇 |
2011年 | 52篇 |
2010年 | 14篇 |
2009年 | 26篇 |
2008年 | 31篇 |
2007年 | 33篇 |
2006年 | 32篇 |
2005年 | 34篇 |
2004年 | 38篇 |
2003年 | 22篇 |
2002年 | 19篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 12篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 8篇 |
1973年 | 12篇 |
1971年 | 4篇 |
1969年 | 3篇 |
排序方式: 共有700条查询结果,搜索用时 0 毫秒
81.
Gino Bontempelli Salvatore Daniele Gilberto Schiavon Mario Fiorani 《Transition Metal Chemistry》1987,12(4):292-295
Summary Evidence for the ability of the electrogenerated cationic nickel(I) complex [Ni(PPh3)4]+ to promote the isomerization of allylbenzene is reported. However, the corresponding triethylphosphitenickel(I) complex displays no catalytic activity, apparently due to the poor leavinggroup character exhibited by the phosphite. The involvement of a -allylnickel hydride in the isomerization reaction is inferred from a comparison of the results obtained with those for the same reaction promoted by nickel hydride. 相似文献
82.
83.
84.
Single crystal structure studies at room temperature have been made for the first stage Mn Cl2 intercalated graphite. The nominal composition was C5·6 Mn Cl2·4, as deduced from chemical analyses and X-ray diffraction intensities. The data are in agreement with the island model, already proposed for Ni Cl2 intercalation. From the decrease in C-C bond length and comparison with As F5 compound, it is shown that the charge transfer is determined by chlorine in excess with respect to free metal halide. 相似文献
85.
86.
We show that the proton can be made absolutely stable, without introducing superheavy bosons, by imposing a global U(1) color symmetry on the Higgs couplings of the theory. Vector-like SU(5) and SU(6) models are discussed in detail. 相似文献
87.
Zayats M Katz E Baron R Willner I 《Journal of the American Chemical Society》2005,127(35):12400-12406
An electrically contacted glucose dehydrogenase (GDH) enzyme electrode is fabricated by the reconstitution of the apo-GDH on pyrroloquinoline quinone (PQQ)-functionalized Au nanoparticles (Au-NPs), 1.4 nm, associated with a Au electrode. The Au-NPs functionalized with a single amine group were attached to the Au surface by 1,4-benzenedithiol bridges, and PQQ was covalently linked to the Au-NPs. The apo-GDH was then reconstituted on the PQQ cofactor sites. The surface coverage of GDH corresponded to 1.4 x 10(-12) mol cm(-2). The reconstituted enzyme revealed direct electrical contact with the electrode surface, and the bioelectrocatalytic oxidation of glucose occurred with a turnover number of 11,800 s(-1). In contrast, a system that included the covalent attachment of GDH to the PQQ-Au-NPs monolayer in a random, nonaligned, configuration revealed lack of electrical communication between the enzyme and the electrode, albeit the enzyme existed in a bioactive structure. The bioelectrocatalytic function of the later system was, however, activated by the diffusional electron mediator 2,6-dichlorophenol-indophenol. The results imply that the alignment of GDH on a Au-NP through the reconstitution process leads to an electrically contacted enzyme-electrode, where the Au-NP acts as a charge-transfer mediator. 相似文献
88.
In solution, the self-exchange reactions for oxygen-centered pi-radicals, e.g., PhO. + PhOH <==>PhOH + PhO., are known to occur with low activation enthalpies (E(a) approximately equal to 2 kcal/mol). For the PhO./PhOH couple and, we conclude, for other O-centered pi-radicals, exchange occurs by proton-coupled electron transfer (PCET) with the proton transferred between oxygen electron pairs while the electron migrates between oxygen orbitals orthogonal to the -O- - -H- - -O- transition state plane (Mayer et al. J. Am. Chem. Soc. 2002, 123, 11142). Iminoxyls, R(2)C=NO., are sigma-radicals with substantial spin density on the nitrogen. The R(2)C=NO./R(2)C=NOH self-exchange has a significant E(a) (Mendenhall et al. J. Am. Chem. Soc. 1973, 95, 627). For this exchange, DFT calculations have revealed a counterintuitive cisoid transition state in which the seven atoms, >C=NO- - -H- - -ON=C<, lie in a plane (R = H, Me) or, for steric reasons, two planes twisted at 45.2 degrees (R = Me(3)C). The planar transition state has the two N-O dipoles close to each other and pointing in the same direction and an O- - -H- - -O angle of 165.4 degrees . A transoid transition state for R = H lies 3.4 kcal/mol higher in energy than the cisoid despite a more favorable arrangement of the dipoles and a near linear O- - -H- - -O. It is concluded that iminoxyl/oxime self-exchange reactions occur by a five-center, cyclic PCET mechanism with the proton being transferred between electron pairs on the oxygens and the electron migrating between in-plane orbitals on the two nitrogens (R(N-N) = 2.65 A). The calculated E(a) values (8.8-9.9 kcal/mol) are in satisfactory agreement with the limited experimental data. 相似文献
89.
90.
Ohne Zusammenfassung 相似文献