全文获取类型
收费全文 | 237篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
化学 | 185篇 |
数学 | 21篇 |
物理学 | 44篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2016年 | 3篇 |
2015年 | 7篇 |
2014年 | 5篇 |
2013年 | 14篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 6篇 |
2007年 | 10篇 |
2006年 | 25篇 |
2005年 | 17篇 |
2004年 | 14篇 |
2003年 | 19篇 |
2002年 | 20篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有250条查询结果,搜索用时 31 毫秒
71.
Wakihara T Yamakita S Iezumi K Okubo T 《Journal of the American Chemical Society》2003,125(41):12388-12389
We focus on the eteroepitaxial growth of trigonal chabazite with voids of three-dimensional intersection structures. The differences in the structures originate from the stacking sequences of the six-membered rings. Sodalite along 111 is constructed by an "abcabc" stacking sequence, while chabazite along [111] is constructed by "abab". Therefore, chabazite can grow heteroepitaxially on a sodalite substrate while keeping the relation of chabazite (111)//sodalite {111}. In this Communication, we report on the first success of the heteroepitaxial growth of a continuous zeolite (chabazite) film with a unique patterned surface-texture on a millimeter-sized sodalite single crystal. We have found that the unique texture of chabazite films is rationalized by the heteroepitaxial growth of chabazite on sodalite and the subsequent twin formation of chabazite. 相似文献
72.
Ando K Tsuji E Ando Y Kuwata N Kunitomo J Yamashita M Ohta S Kohno S Ohishi Y 《Organic & biomolecular chemistry》2004,2(4):625-635
Novel 3-acetoacetylaminobenzo[b]furan derivatives having a modified triene system at the 3-position were synthesized starting with 3-aminobenzo[b]furans. The enol isomers, 3-[(3-hydroxybut-2-enonyl)amino]benzo[b]furans (), of the 3-acetoacetylaminobenzo[b]furans were obtained as stable isomers owing to formation of a hydrogen bonding between the enol hydroxyl group and the amidocarbonyl group. The planarity of the C-2 substituent through the C-3 side chain suggested the existence of a modified conjugational triene system in the enol compound. Cysteinyl leukotriene 1 and 2 receptor antagonistic activities for these compounds were evaluated. 2-(4-Cyanobenzoyl or ethoxycarbonyl)-3-[(2-cyano-3-hydroxybut-2-enonyl)amino]benzo[b]furans (, ) were moderately active. 相似文献
73.
Synthesis and properties of optically active 1,3-diols and their derivatives as chiral dopants for ferroelectric liquid crystals 总被引:1,自引:0,他引:1
Tetsuo Kusumoto Ken-Ichi Sato Kumiko Ogino Tamejiro Hiyama Sadao Takehara Masashi Osawa Kayoko Nakamura 《Liquid crystals》1993,14(3):727-732
New chiral dopants β-hydroxy ketones 1, 1,3-diols 2, 1,3-dioxanes 3 and 1,3-dioxan-2-ones 4 were designed and synthesized. Reaction of (R)-1,2-epoxyoctane with carbanions derived from 2-(4-substituted phenyl)-1,3-dithianes followed by hydrolysis of the resulting hydroxy dithianes afforded 1. Reduction of 1 gave the diols 2, which yielded 3 upon acetalization and 4 upon carbonation. The syn isomers of 2, 3, and 4 exhibited larger spontaneous polarizations, when applied as chiral dopants, than the anti isomers or hydroxy ketones 1. 相似文献
74.
This report discusses the effect of fluoroalkyl chain on the mesomorphism. Several homologues of novel triphenylene compounds possessing fluoroalkylated side chains were synthesized. Studies of X-ray diffraction, DSC and texture observations by polarized microscope revealed that these homologues show hexagonal columnar (Colh) mesophase. These homologues made columnar mesophase stabilize and the melting point increase, as compared with corresponding alkyloxytriphenylenes. In the case of fluoroalkyloxytriphenylenes possessing fluoromethylene side chains, the increase of the fluoromethylene chain length stabilized columnar mesophase, made the phase transition enthalpy (Colh-Iso) and entropy (Colh-Iso) increase. It is considered that these results are due to the fluorophilic interaction, and that the fluorophilic interaction is important for stabilizing columnar mesophase. 相似文献
75.
Takahashi M Shimoyama K Kyotani C Sato H Ogino K 《Journal of chromatography. A》2005,1084(1-2):201-206
Chromatographic separation of copolymers depending on the chemical composition was studied by a solvent gradient method using liquefied carbon dioxide (CO2) as an adsorption promoting solvent. As the high polar stationary phase, non-bonded silica gel, crosslinked acrylamide (AA) gel and crosslinked acrylonitrile (AN) gel were utilized. All columns showed the typical normal phase type of adsorption. Polymeric stationary phases showed the higher sample recovery for styrene-methyl methacrylate (St-MMAs) copolymers, indicating suitability for quantitative analyses. The separations of butyl methacrylate (BMA)-methyl methacrylate, and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate (FBMA)-methy methacrylate copolymers were also carried out, and the latter copolymers were separated based on the CO2-philicity with acrylonitrile column. 相似文献
76.
77.
Targeted proteo-glycomics analysis of Sialyl Lewis X antigen expressing glycoproteins secreted by human hepatoma cell line. 总被引:2,自引:0,他引:2
Sialyl Lewis X (SLEX) antigen, Neu5Acalpha2-3Galbeta1-4 (Fucalpha1-3) GlcNAc-R, plays important roles in cell-to-cell interaction: for example, the E- and P-selectin-mediated influx of SLEX expressing leukocytes into inflamed areas. A human hepatocellular carcinoma cell line, HepG2 cells, was highly expressed SLEX on secreted glycoproteins and cell surface, in contrast with HuH-7 cells. We identified SLEX expressing glycoproteins in HepG2 cultured medium by two-dimensional polyacrylamide gel electrophoresis, followed by in gel digestion and peptide mass fingerprint using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOFMS), including transferrin, alpha1-antitrypsin, alpha2-HS glycoprotein and beta-glycoprotein. We analyzed N-glycans of these glycoproteins by MALDI-TOFMS in combination with exoglycosidase digestion; our results indicate increases in poly-fucosylated and high-branched N-glycans. High alpha1,3-fucosylation in glycoproteins would be caused by increased expression of alpha1,3-fucosyltransferase activities in HepG2 cells. 相似文献
78.
79.
Yutaka Ando Tomomi Hanada Kumiko Saitoh 《Journal of Polymer Science.Polymer Physics》1994,32(1):179-185
Dielectric and thermal characterizations were performed for poly (vinylidene fluoride) (PVDF)/poly (ethyl methacrylate) (PEMA) blends of different composition. The characteristics of PVDF β relaxation were shown to be little affected in the semicrystalline blends with PEMA. The relaxation strength, however, depends strongly on the PEMA content and a linear relation was found between the intensity of the β relaxation and the weight fraction of the PVDF crystal-amorphous interphase. Phase structures of the PVDF/PEMA blends are also proposed. © 1994 John Wiley & Sons, Inc. 相似文献
80.