全文获取类型
收费全文 | 995篇 |
免费 | 26篇 |
国内免费 | 8篇 |
专业分类
化学 | 693篇 |
晶体学 | 6篇 |
力学 | 9篇 |
数学 | 39篇 |
物理学 | 282篇 |
出版年
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 10篇 |
2017年 | 4篇 |
2016年 | 18篇 |
2015年 | 15篇 |
2014年 | 20篇 |
2013年 | 48篇 |
2012年 | 45篇 |
2011年 | 74篇 |
2010年 | 24篇 |
2009年 | 34篇 |
2008年 | 70篇 |
2007年 | 71篇 |
2006年 | 75篇 |
2005年 | 72篇 |
2004年 | 50篇 |
2003年 | 37篇 |
2002年 | 47篇 |
2001年 | 23篇 |
2000年 | 21篇 |
1999年 | 8篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 18篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 11篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1968年 | 4篇 |
1964年 | 3篇 |
排序方式: 共有1029条查询结果,搜索用时 15 毫秒
991.
An effective procedure for decontamination of beta-lactam antibiotic residues or contaminants in the pharmaceutical manufacturing environment was investigated. Decontamination with solutions of hydrochloric acid, sodium hydroxide, hydrogen peroxide and hydroxylamine as agents for degradation was assessed. According to the results, the beta-lactam antibiotics were significantly degraded with sodium hydroxide and hydroxylamine. From the structural analysis of the degradation products of a cephem antibiotic, cefpodoxime proxetil, it was found that hydroxylamine degraded the beta-lactam structure under mild conditions, while sodium hydroxide did not. Therefore, hydroxylamine was considered an appropriate decontamination agent for beta-lactam antibiotics. 相似文献
992.
Toshiharu Kawasaki 《Czechoslovak Mathematical Journal》2009,59(2):381-399
In this paper we define the derivative and the Denjoy integral of mappings from a vector lattice to a complete vector lattice
and show the fundamental theorem of calculus.
相似文献
993.
Yasuna Kawasaki Keita Deguchi Satoshi Demura Tohru Watanabe Hiroyuki Okazaki Toshinori Ozaki Takahide Yamaguchi Hiroyuki Takeya Yoshihiko Takano 《Solid State Communications》2012,152(13):1135-1138
Phase diagrams of as-grown and O2-annealed FeTe1?xSex determined from magnetic susceptibility measurement were obtained. For as-grown samples, the antiferromagnetic order was fully suppressed in the range region x≥0.15, and weak superconductivity appeared when x≥0.1. Beginning at x=0.5, weak superconductivity was found to evolve into bulk superconductivity. Interestingly, for O2-annealed samples, complete suppression of magnetic order and the occurrence of bulk superconductivity were observed when x≥0.1. We found that O2-annealing induces bulk superconductivity for FeTe1?xSex. Oxygen probably plays a key role in the suppression of the magnetic order and the appearance of bulk superconductivity. 相似文献
994.
995.
Smog chamber/FTIR techniques were used to study the Cl atom initiated oxidation of CH2FOCH2F in 700 Torr of N2/O2 at 296 K. Relative rate techniques were used to measure k(Cl + CH2FOCH2F) = (4.6 ± 0.7) × 10?13 and k(Cl + CH2FOC(O)F) = (2.9 ± 0.8) × 10?15 (in units of cm3 molecule?1 s?1). Three competing fates for alkoxy radical CH2FOCHFO· formed in the self‐reaction of the corresponding peroxy radicals were identified. In 1 atm of air at 296 K, 48 ± 3% of CH2FOCHFO· radicals decompose via C? O bond scission, 21 ± 4% react with O2, and 31 ± 4% undergo hydrogen atom elimination. Chemical activation effects were observed for CH2FOCHFO· radicals formed in the CH2FOCHFOO· + NO reaction. Infrared spectra of CH2FOC(O)F and FC(O)OC(O)F, which are produced during the Cl atom initiated oxidation of CH2FOCH2F, are presented. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 139–147, 2002; DOI 10.1002/kin.10038 相似文献
996.
Adsorption of dyes onto carbonaceous materials produced from coffee grounds by microwave treatment 总被引:6,自引:0,他引:6
Hirata M Kawasaki N Nakamura T Matsumoto K Kabayama M Tamura T Tanada S 《Journal of colloid and interface science》2002,254(1):17-22
Organic wastes have been burned for reclamation. However, they have to be recycled and reused for industrial sustainable development. Carbonaceous materials were produced from coffee grounds by microwave treatment. There are many phenolic hydroxyl and carboxyl groups on the surface of carbonaceous materials. The base consumption of the carbonaceous materials was larger than that of the commercially activated carbon. The carbonaceous materials produced from coffee grounds were applied to the adsorbates for the removal of basic dyes (methylene blue and gentian violet) in wastewater. This result indicated that the adsorption of dyes depended upon the surface polar groups on the carbonaceous materials. Moreover, the Freundlich constants of isotherms for the adsorption of methylene blue and gentian violet onto the carbonaceous materials produced from coffee grounds were greater than those for adsorption onto activated carbon or ceramic activated carbon. The interaction was greatest between the surface or porosity of the carbonaceous materials and methylene blue and gentian violet. The microwave treatment would be useful for the carbonization of organic wastes to save energy. 相似文献
997.
By utilizing a flexible co-ligand 1,2-bis(2-pyridyl)ethylene (2,2'-bpe), two new azido-bridged cobalt(II) complexes with the formulae [Co?(N?)?(OH?)?(2,2'-bpe)?](n)(2,2'-bpe)(n) (1) and [Co(N?)?(2,2'-bpe)?](n) (2) have been synthesized and structurally characterized. Compound 1 shows an uncommon 1D chain comprised of double EO azido bridged five- and six-coordinated Co(II) geometries in a unique (-5-5-6-)(n) sequence of the coordination number. The 2,2'-bpe acts as a terminal co-ligand and an uncoordinated molecule in the crystal lattice. Moreover the adjacent 1D chain is assembled by C-Hπ interactions and the intermolecular hydrogen bonding between uncoordinated 2,2'-bpe and coordinated water molecules building a 2D layer. Whereas, compound 2 is a 2D coordination network containing the alternating double EO and double EE bridging modes of azides and ditopic 2,2'-bpe bridges. The magnetic investigation of 1 reveals dominant intra-chain ferromagnetic interactions, with the double EO azide-bridge and weak inter-chain antiferromagnetic interactions, with overall metamagnetic behaviour, having magnetic ordering at 6 K. The magnetic behaviour of 2 shows spin-canted antiferromagnetism below a T(N) of 12 K. 相似文献
998.
Ikuo Kawasaki 《Tetrahedron letters》2005,46(38):6549-6553
Reaction of 1-substituted 3-alkenyl-1H-indoles with an equimolar amount of trifluoroacetic acid in dichloromethane gave cyclic dimers, 1,3-trans-N,N′-disubstituted cyclopent[b]indoles, in 53-84% yields as sole products through an acid-mediated stereoselective cyclo-dimerization process. The structure of the cyclic dimer derived from 3-cyclopentylidenemethyl-1-methyl-1H-indole was elucidated by X-ray crystallographic analysis. 相似文献
999.
Ikuo Kawasaki 《Tetrahedron letters》2005,46(7):1199-1203
Reaction of 1-tert-butoxycarbonyl-3-cyclopentylidenemethyl-1H-indole with an excess of trifluoroacetic acid in dichloromethane at room temperature gave a cyclic dimer, 13-cyclopentyl-6,7,12,13-tetrahydrospiro[5H-cyclohepta[1,2-b:4,5-b′]diindole-6,1′-cyclopentane] in 73% yield as the sole product through a novel cyclo-dimerization process. Structure of the cyclic dimer derived from 5-bromo-1-t-butoxycarbonyl-3-cyclopentylidenemethyl-1H-indole was elucidated by X-ray crystallographic analysis. 相似文献
1000.
Kawasaki N Kinoshita H Oue T Nakamura T Tanada S 《Journal of colloid and interface science》2004,275(1):40-43
The adsorption behavior of benzene, toluene, o-xylene, m-xylene, and p-xylene onto activated carbon was investigated using the flow method. The removal efficiency of aromatic hydrocarbons in the gaseous phase was estimated based on the adsorption kinetic constants and the saturated amount of aromatic hydrocarbons adsorbed on the activated carbon. The saturated amount of benzene and toluene adsorbed was greater than that of xylene adsorbed because the molecular sizes of benzene and toluene are smaller than that of xylene. The adsorption kinetic constant increased in the order of xylene, toluene, and benzene. Those of the three xylene isomers were similar. These results indicated that the adsorption rate of benzene by the activated carbon was the fastest and the kinetic constant depended upon the different between the boiling point and the melting point and the molecular size of the aromatic hydrocarbons. 相似文献