全文获取类型
收费全文 | 326篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
化学 | 269篇 |
数学 | 15篇 |
物理学 | 51篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 10篇 |
2014年 | 6篇 |
2013年 | 17篇 |
2012年 | 22篇 |
2011年 | 17篇 |
2010年 | 17篇 |
2009年 | 9篇 |
2008年 | 23篇 |
2007年 | 22篇 |
2006年 | 22篇 |
2005年 | 15篇 |
2004年 | 12篇 |
2003年 | 17篇 |
2002年 | 10篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有335条查询结果,搜索用时 31 毫秒
41.
K. Tshoo Y. Satou H. Bhang S. Choi T. Nakamura S. Deguchi Y. Kawada Y. Kondo N. Kobayashi Y. Nakayama K. N. Tanaka N. Tanaka N. Aoi M. Ishihara T. Motobayashi H. Otsu H. Sakurai S. Takeuchi Y. Togano K. Yoneda Z. H. Li F. Delaunay J. Gibelin F. M. Marques N. A. Orr T. Honda M. Matsushita T. Kobayashi Y. Miyashita T. Sumikama K. Yoshinaga S. Shimoura D. Sohler T. Zheng Z.X. Cao 《Few-Body Systems》2013,54(1-4):459-463
The unbound excited states of the most neutron-rich dripline oxygen isotope, 24O, have been investigated by using the 24O(p,p′)24O* reaction at the beam energy of 62 MeV/nucleon in inverse kinematics. The first and second unbound excited states of 24O have been observed at ${E_{\rm x}= 4.63_{-0.14}^{+0.30}}$ MeV and ${E_{\rm x}= 5.13_{-0.24}^{+0.19}}$ MeV (preliminary) along with the evidence for another higher lying state at around 7.3 MeV. The quadrupole deformation parameter ${\beta_{2^+}}$ was deduced to be ${0.15_{-0.03}^{+0.08}}$ (preliminary) for the first time. The systematics of the ${\beta_{2^+}}$ and the ${E_{\rm x}(2_1^+)}$ in the Z = 8 isotopes shows the N = 16 spherical shell closure in 24O. 相似文献
42.
43.
Yukako Yoshinaga Dr. Takeshi Yamamoto Prof. Dr. Michinori Suginome 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(18):7318-7322
Enantiospecific intramolecular Suzuki–Miyaura-type coupling with α-(2-halobenzoylamino)benzylboronic esters to give 3-substituted isoindolinones is achieved by using copper catalysts with 2,2′-bipyridine-based achiral ligands. Enantioenriched α-aminobenzylboron reactants bearing a hydrogen atom at the boron-bound stereogenic carbons undergo stereoinvertive coupling in the presence of a 6-phenyl-2,2′-bipyridine ligand with high enantiospecificity. α-Aminobenzylboronates bearing fully substituted boron-bound stereogenic centers also gave the 3,3-disubstituted isoindolinones with stereospecific stereochemical inversion in the presence of simple 2,2′-bipyridine as a ligand. 相似文献
44.
Polysubstituted pyridine derivatives were synthesized by the reaction of ketene dithioacetal, 3,3-bis(methylsulfanyl)methylenemalononitrile 1b, with a variety of active methylene compounds in the presence of either sodium hydroxide or potassium hydroxide as a base in DMSO. This reaction was carried out under economical one-pot reaction conditions (cheap catalyst and solvent) and solved the problem of the odor of methanethiol, commonly derived from reactions of ketene dithioacetals. This is a significant enhancement of GSC (green and sustainable chemistry) in the field of ketene dithioacetal chemistry. 相似文献
45.
Tormena CF Santos FP Neto AC Rittner R Yoshinaga F Temistocles JC 《The journal of physical chemistry. A》2007,111(2):295-298
Conformational preferences and electronic interactions of trans-2-fluorocyclopentanol (1), trans-2-chlorocyclopentanol (2), and trans-2-bromocyclopentanol (3) were analyzed using experimental and theoretical (3)J(HH) coupling constants, theoretical calculations, and natural bond orbital (NBO) analysis. The conformational equilibria of compounds 1-3 can be represented by their diaxial and diequatorial conformers as supported by theoretical calculations. From (3)J(HH) coupling constant values, it can be found that the diequatorial conformer is present in the equilibrium as 55% for compound 1 and as 60% for compounds 2 and 3. This behavior is in agreement with orbital interaction analyses obtained from NBO. 相似文献
46.
Formation of metallic Ni nanoparticles on titania surfaces by chemical vapor reductive deposition method 总被引:1,自引:0,他引:1
Yoshinaga M Takahashi H Yamamoto K Muramatsu A Morikawa T 《Journal of colloid and interface science》2007,309(1):149-154
Metallic Ni nanoparticles were successfully prepared on the surface of titania thin film substrate by a novel method, named as chemical vapor reductive deposition (CVRD) method. The growth of the nanoparticles was based on the specific adsorption and heterogeneous nucleation on the surface of substrate, not via vapor-phase formation and subsequent sedimentation. The nanoparticle size was found to be well controllable between 10 and 30 nm by the preparation time and vapor pressure of metal complex precursor. ESCA and electron diffraction results clearly demonstrated Ni nanoparticles as metallic. Titania thin film with metallic Ni nanoparticles on its surface showed high efficiency in their photocatalysis of hydrogen evolution from decomposition of ethanol. 相似文献
47.
Angelo Sassaroli Fabrizio Martelli Yukari Tanikawa Kenji Tanaka Ryuichiro Araki Yoichi Onodera Yukio Yamada 《Optical Review》2000,7(5):420-425
The in vivo optical properties of a piglet brain were measured using a time-resolved system at three different wavelengths (759, 794, 824 nm). To separate the contribution of different head layers to the detected signals, the measurements were acquired from the surfaces of skin, skull, dura mater and brain. The source detector distance was chosen to assure a mean penetration depth within each layer. Measurements were analyzed and compared with the results of other in vivo measurements reported in literature. 相似文献
48.
Polymer modification of colloidal particles by spontaneous polymerization of surface active monomers 总被引:1,自引:0,他引:1
Adsorption and spontaneous polymerization of head- or tail-type surface active monomers having long methylene chains on colloidal
silica and δ-alumina were investigated. Both head-type and tail-type ammonium monomers on silica in chloroform or tetrahydrofuran
had the maximum adsorption on the respective adsorption isotherm. Above the monomer concentration giving the maximum adsorption,
it was observed that the monomer formed micelles or clusters in bulk solution with removal of adsorbed water molecules from
the silica surface. At the monomer concentration giving the maximum adsorption, heating the silica suspension containing the
monomer at 40°C or 60°C in tetrahydrofuran or chloroform solution resulted in spontaneous polymerization. The composite particles
formed by polymerization were observed to have many spots consisting of polymer on the surface. Therefore, it is suggested
that the monomers are concentrated by micelle-like aggregation on the silica surface and consecutively spontaneous polymerization
takes place. Adsorption of an anion-type monomer having a carboxyl group on δ-alumina, which exhibited a positive ζ potential
in neutral aqueous solution, was higher than that on colloidal silica, but did not spontaneously polymerize on alumina.
Received: 13 June 1998 Accepted in revised form: 19 August 1998 相似文献
49.
Yoshio Fuchita Kazuhiko Yoshinaga Tomoko Hanaki Hiroyuki Kawano Junko Kinoshita-Nagaoka 《Journal of organometallic chemistry》1999,580(2):2258
Cyclopalladation of mono-, di- and tribenzylamine has been investigated by reacting the corresponding amines with an equimolar amount of palladium(II) acetate (reaction i), or by heating the corresponding bis-amine complexes [Pd(O2CMe)2{(PhCH2)nNH3−n}2] (n=1, 2) (reaction ii). By the reaction i, all the three amines undergo cyclopalladation. However, in the case of the reaction ii, only the dibenzylamine complex [Pd(O2CMe)2{(PhCH2)2NH}2] has been converted into a cyclopalladated complex. The reactivity of the three benzylamines towards cyclopalladation has been discussed in terms of the co-ordinating ability influenced by the bulkiness around the nitrogen atom. Temperature-dependent 1H-NMR spectra are observed for mononuclear cyclopalladated complexes [Pd(O2CMe){C6H4CH2N(CH2Ph)2–C1, N}L] (L=PPh3, AsPh3) and are attributed to the dissociation of the nitrogen atom in the cyclopalladated chelate ring. A heteroleptic bis-cyclopalladated complex [Pd[C6H4CH2N(CH2Ph)2–C1, N](C6H4CH2NMe2–C1, N)] has also been prepared. X-ray crystallographic studies on [{Pd(O2CMe)[C6H4CH2N(CH2Ph)2–C1, N]}2] and [Pd[C6H4CH2N(CH2Ph)2–C1, N](C6H4CH2NMe2–C1, N)] have been reported. 相似文献
50.
WANG Qiu-Quan Masayuki Yoshinaga Sohei Ikeda. Kin-ichi Tsunoda Hideo Akaiwa 《高等学校化学学报》1999,20(Z1):291
Hard and Soft Acids and Bases Principle (HSAB Principle) of Pearson, Jensen, Davies and Hartley, which consider a metal ion as a Lewis acid and a monodentate ligand as a Lewis base, had been used to evaluate the interaction between a central metal ion and the donor atom of a ligand. 相似文献