全文获取类型
收费全文 | 110篇 |
免费 | 2篇 |
专业分类
化学 | 78篇 |
数学 | 3篇 |
物理学 | 31篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 11篇 |
2007年 | 5篇 |
2006年 | 13篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有112条查询结果,搜索用时 15 毫秒
61.
Masafumi Tamura Hayato Ogata Yuu Ishida Yasunori Takahashi 《Tetrahedron letters》2017,58(40):3808-3813
Pd-catalyzed asymmetric 1,4-addition of phenylboronic acid to α,β-unsaturated carbonyl compounds was developed using chiral 1,10-phenanthroline derivative as ligand. Good yields (up to 97%), and high enantioselectivities (up to 97% ee) were achieved. 相似文献
62.
Yutaka Tokiwa Akira Iwamoto Masatoshi Koyama Naoaki Kataoka Haruo Nishida 《Macromolecular Symposia》1992,57(1):273-279
Biodegradable blend plastics such as polycaprolactone (PCL)-conventional plastics blends, PCL-polystyrene blend foams, PCL-poly-3-hydroxybutyrate (PHB) blends, PCL-raw cornstarch (CS) blends and PCL-CaCO3 blends were developed. It was suggested that the thermophilic composting of biodegradable plastics containing PCL was one of powerful technologies for recycling of biodegradable plastics. Furthermore, we tried to get useful products from biodegradable plastics by microbial fermentation processes. Polypropylene (PP)-CS blend and PCL-CS blend plastics were aerobically converted into ethanol by Bacillus polymyxa. PHB and PP-CS blend and PCL-CS blend plastics were anaerobically converted into some organic acids and methane gas by mixed microbial cultures with a methanogenic bacterium. 相似文献
63.
Yuu UCHIO Naoko SHIMA Kaho NAKAMURA Osamu NITTA Tetsuo IKAI 《Physical Therapy Research》2021,24(3):204
Objective: To clarify the corrected age of walking attainment in very low birth weight infants by birth weight and gestational age, and determine perinatal factors affecting the delay in walking attainment. Method: This was a longitudinal study. We investigated walking attainment and perinatal factors in 145 very low birth weight infants without neurological abnormalities (mean birth weight 1019.3 ± 299.7 g, gestational age 29.0 ± 2.9 weeks). The study infants were stratified by birth weight (group A: <1,000 g, group B: 1,000 g≤, <1,500 g) and gestational age (group I: <28 weeks, group II: 28 weeks≤, <37 weeks) and were compared using unpaired t-tests. Furthermore, we examined the perinatal factors that affect the delay in walking attainment using multiple regression analysis. Results: Of the walking attainment, infants in Group A were older than those in Group B (50th percentile, 15.8 vs. 14.7 months). Infants in Group I were older than those in Group II (50th percentile, 16.0 vs. 14.8 months). Using multiple regression analysis with walking attainment age as the dependent variable, the duration of mechanical ventilation was found to be significantly related. Conclusion: Very low birth weight infants with light weight and short gestational age have delayed walking attainment, and longer duration of mechanical ventilation increases the risk of delay. 相似文献
64.
Citrinadin A, a novel pentacyclic alkaloid from marine-derived fungus Penicillium citrinum 总被引:4,自引:0,他引:4
Tsuda M Kasai Y Komatsu K Sone T Tanaka M Mikami Y Kobayashi J 《Organic letters》2004,6(18):3087-3089
[structure: see text] A novel pentacyclic alkaloid, citrinadin A (1), was isolated from the cultured broth of the fungus Penicillium citrinum, which was separated from a marine red alga, and the structure was elucidated by spectroscopic data. The relative stereochemistry of the pentacyclic core was assigned on the basis of NOESY data and (1)H-(1)H coupling constants, and the presence of an N,N-dimethyl-L-valine residue in 1 was determined by chiral HPLC analysis of the hydrolysate. 相似文献
65.
Hajime Shigemitsu Dr. Ichiro Hisaki Eriko Kometani Daisuke Yasumiya Yuu Sakamoto Keisuke Osaka Dr. Tejender S. Thakur Dr. Akinori Saeki Prof. Dr. Shu Seki Dr. Fumiko Kimura Prof. Dr. Tsunehisa Kimura Dr. Norimitsu Tohnai Prof. Dr. Mikiji Miyata 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15366-15377
Supramolecular nanofibers (SNFs) composed of low‐molecular‐weight π‐conjugated molecules exhibit attractive optical and electrical properties and are expected to be the next optoelectronic materials. In this work, five crystalline SNFs have been constructed from three dehydrobenzoannulene (DBA) derivatives. The DBAs were designed to assemble in one dimension in a strategy based on anisotropic crystal growth. The crystallinity of the SNFs allowed the molecular arrangements in the SNFs to be determined. Therefore the mechanism of construction and correlations between the molecular arrangements and optical and electrical properties could be considered. The results clearly indicate that the properties of the SNFs are affected by the chemical structures and molecular arrangements. Moreover, one of the SNFs exhibits a high charge‐carrier mobility (Σμ=0.61 cm2 V?1 s?1) because of its crystallinity and appropriate molecular arrangement. This systematic experimental study based on a proposed strategy has provided information for improving the electrical properties of SNFs. This strategy will lead to highly functional SNFs. 相似文献
66.
An efficient two-step method for the synthesis of 1,3-diaryl-2-methoxyindenes from 1-(1-aryl-2-methoxyvinyl)-2-bromobenzenes has been developed. Thus, the reaction of 2-(1-aryl-2-methoxyvinyl)phenyllithiums, generated in situ by halogen–lithium exchange between 1-(1-aryl-2-methoxyvinyl)-2-bromobenzenes and butyllithium, with aromatic aldehydes gives aryl[2-(1-aryl-2-methoxyvinyl)phenyl]methanols, which in turn are treated with a catalytic amount of concentrated hydriodic acid to afford the corresponding 1,3-diaryl-2-methoxyindenes in reasonable yields. 相似文献
67.
Ito Y Tomiyasu Y Kawanabe T Uemura K Ushimizu Y Nishino H 《Organic & biomolecular chemistry》2011,9(5):1491-1507
Cyclophane-type macrocyclic compounds from 21 to 56 members having two fused dihydrofuran rings were synthesized by the manganese(III)-mediated oxidation of terminal dienes with bis(3-oxobutanoate)s containing aromatics. The reaction detail, characterization and reaction pathways are described. 相似文献
68.
Intra-board interconnection between optical waveguide channels is suitable for assembling high-speed optoelectronic printed
wiring boards (OE-PWB). Here, we propose a novel optical interconnection method combining techniques for both wavelength-based
optical waveguide addressing and plug-in optical waveguide alignment with a micro-hole array (MHA). This array was fabricated
by the mask transfer method. For waveguide addressing, we used a micro passive wavelength selector (MPWS) module, which is
a type of Littrow mount monochromator consisting of an optical diffraction grating, a focusing lens, and the MHA. From the
experimental results, we found that the wavelength addressing operation of the MPWS module was effective for intra-board optical
interconnection. 相似文献
69.
Many experimental and modeling studies have examined several factors affecting radon emanation. Of these factors, the effect of temperature shown in earlier experiments has not been discussed with model calculations. In the present study, radon emanation fractions were calculated for various temperatures, namely different air densities, using a simple model into which the emanation processes originating from alpha recoil were incorporated. As a result, the slightly negative correlation that the radon emanation fraction decreased with increasing temperature was observed within a certain range of grain size, while temperature had no effect within the other range. Considering the current knowledge of processes through which radon emanation occurs, this result would be expected to be qualitatively reasonable. However, the result is not similar to all previous experimental results showing the positive correlation. These papers occasionally explain that the positive correlation is attributable to the adsorption of radon on solids during its transfer among grains. Since the general definition of radon emanation includes no transfer process after its release from a grain, their explanation could not be well established. The discrepancy between the calculated and measured data may suggest the needs of review and improvement of experimental and/or modeling techniques. 相似文献
70.
Masako Sasaki Sumihiro Koyama Kiminori Tokiwa Hitoshi Fujita 《Photochemistry and photobiology》1993,57(5):796-802
Abstract— Intracellular targets for the photosensitizer α-terthienyl (αT) were examined by fluorescence microscopy and microfluorospectrometry using human nonkeratinized buccal cells. Intracellular distribution of αT was observed as fluorescent patches widely dispersed in the cytoplasm. The distribution of the fluorescent patches was compared with that of acid phosphatase activity visualized as an azo dye produced by the fast garnet 2-methyl-4-[(2-methyl-phenyl)azo]benzenediasonium sulfate reaction. Because both the distribution sites coincided, lysosomes were the likely sites of intracellular affinity of αT. However, because acid phosphatase is not a specific lysosomal marker, we tried to detect another lysosomal enzyme, β-galactosidase, to confirm if the fluorescent patches were lysosomes, using fluorescein-di-(β-D-galactopyranoside) (FDG) as a fluorogenic substrate. Without UV-A (320–400 nm) irradiation of the cells after uptake of αT and FDG, no significant fluorescence was observed. In contrast, with prior UV-A irradiation in the presence of αT and FDG, the bright yellow fluorescence of fluorescein, which is the digested product of FDG, was clearly detected in the cells by fluorescence microscopy. This observation implied that inflow of external FDG into the lysosomes is caused by lysosomal membrane damage on αT photosensitization. The present results indicated that lysosomes are the primary photosensitization site of αT. 相似文献