全文获取类型
收费全文 | 124篇 |
免费 | 5篇 |
专业分类
化学 | 109篇 |
力学 | 3篇 |
数学 | 5篇 |
物理学 | 12篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 3篇 |
2013年 | 15篇 |
2012年 | 9篇 |
2011年 | 9篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 9篇 |
2006年 | 8篇 |
2005年 | 3篇 |
2004年 | 8篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 3篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有129条查询结果,搜索用时 15 毫秒
121.
122.
P. H. Umadikar Milind Vaidya S. R. Joshi S. K. Karadnikar R. Nagarajan V. R. Marathe 《Hyperfine Interactions》1988,41(1):521-524
We report here our57Fe Mössbauer studies on the mixed and substituted iron garnets. Magnetisation studies on substituted SmIG system {Sm3?x Cax} [Snx Fe2?x](Fe3)012 (0.2≤x≤1.8) show that the Tc decreases as x increases. We attribute this to the reduced strength of a-d interaction as a result of dilution of a-site. While the Mössbauer spectra seem to reflect this, an interesting feature is the unresolved hyperfine spectrum seen at 80K for x=1.0, even though the transition temperature (Tc) is 285K. For this concentration, varying the rare earth ion from Sm to Er, results in very similar spectra. We speculate spin glass behaviour for x=1.0. In mixed and substituted garnet system {Gd2.5R0.2Ca0.3} [Sn0.3Fe1.7](Fe3)012 (R=Y, Sm, Eu, Ho and Er), we observe well resolved spectra with no change in the hyperfine field with substitution of rare earth. This is consistant with the dominance of a-d interaction in these systems. 相似文献
123.
A short, versatile, and enantioselective synthesis of 1-deoxy-8-epi-castanospermine (5), 1-deoxy-8-hydroxymethyl castanospermine (6), and (6S,7S,8R,8aR)-8-amino-octahydroindolizine-6,7-diol (7) is achieved from a common template 12. The key step utilized is PET provoked amine radical cyclization of 11 to 12 in excellent diastereoselectivity. The exocyclic double bond at C-8 of the template is functionalized to obtain 5-7 as exclusive diastereomers. 1-Deoxy-8-epi-castanospermine exhibited inhibition of α- and β-galactosidase and β-glucosidase. Compounds 6 and 7 were found to be weak inhibitors of β-glucosidase. 相似文献
124.
Banerjee A Misra M Pai D Shih LY Woodley R Lu XJ Srinivasan AR Olson WK Davé RN Venanzi CA 《Journal of chemical information and modeling》2007,47(6):2216-2227
Six rigid-body parameters (Shift, Slide, Rise, Tilt, Roll, Twist) are commonly used to describe the relative displacement and orientation of successive base pairs in a nucleic acid structure. The present work adapts this approach to describe the relative displacement and orientation of any two planes in an arbitrary molecule-specifically, planes which contain important pharmacophore elements. Relevant code from the 3DNA software package (Nucleic Acids Res. 2003, 31, 5108-5121) was generalized to treat molecular fragments other than DNA bases as input for the calculation of the corresponding rigid-body (or "planes") parameters. These parameters were used to construct feature vectors for a fuzzy relational clustering study of over 700 conformations of a flexible analogue of the dopamine reuptake inhibitor, GBR 12909. Several cluster validity measures were used to determine the optimal number of clusters. Translational (Shift, Slide, Rise) rather than rotational (Tilt, Roll, Twist) features dominate clustering based on planes that are relatively far apart, whereas both types of features are important to clustering when the pair of planes are close by. This approach was able to classify the data set of molecular conformations into groups and to identify representative conformers for use as template conformers in future Comparative Molecular Field Analysis studies of GBR 12909 analogues. The advantage of using the planes parameters, rather than the combination of atomic coordinates and angles between molecular planes used in our previous fuzzy relational clustering of the same data set (J. Chem. Inf. Model. 2005, 45, 610-623), is that the present clustering results are independent of molecular superposition and the technique is able to identify clusters in the molecule considered as a whole. This approach is easily generalizable to any two planes in any molecule. 相似文献
125.
Maheshwar KundarapuDamien Marchand Shrinivas G. DumbrePiet Herdewijn 《Tetrahedron letters》2011,52(51):6896-6898
A series of 2′ functionalized acyclic nucleoside phosphonate derivatives of 1-[3′-(phosphonomethoxy)propyl]uracil (1-4) have been synthesized together with the 1′ and 2′-ethynyl derivatives of 9/1-[2′-(phosphonomethoxy)ethyl]adenine/thymine (5-7). Key intermediates leading to the latter series are (±)-[2-{diethyl(phosphonomethoxy)}-1-hydroxy]-but-3-yne (25) and (±)-diisopropyl{[2-hydroxy-4-(trimethylsilyl)but-3-yn-1-yl]oxy}methylphosphonate (30). Compounds 25 and 30 are easily obtained starting from (±)-solketal. 相似文献
126.
Shrinivas C. Kothekar 《Journal of Dispersion Science and Technology》2013,34(4):627-631
Foamability and foam stability, emulsifying power, surface tension, and interfacial tension were investigated for different ratios of binary surfactant system of Arlacel‐165 (glyceryl stearate (and) PEG‐100 stearate) and Myrj‐59 (polyoxyethylene 100 stearate). Among all the ratios tested for their foaming power and foamabilty, the ratios 8:2, 5:5, 4:6, 2:8, and 1:9 of Arlacel‐165 and Myrj‐59 showed the best results. At these ratios, the foaming power and foamability was found to be 100%. The surfactants having foam stability more than 50% can be considered as metastable and those less than 50% are considered as low‐stability foams. In case of surface tension and interfacial tension property measurements, 8:2 and 9:1 showed the best results. At 8:2 and 9:1 of Arlacel‐165 and Myrj‐59, the surface tension was found to be 37.7 dynes/cm and 1.33 dynes/cm respectively at 30°C ambient temperature. Also, 7:3 of this binary mixture was found to exhibit the best emulsifying power among all the ratios tested. At 30°C, the emulsifying property of the binary mixture was 6 hours. 相似文献
127.
Milind Rode R. C. Gupta B. K. Karale S. S. Rindhe 《Journal of heterocyclic chemistry》2008,45(6):1597-1602
128.
A new, rapid and sensitive RP-HPLC method with UV spectrophotometric detection was developed and validated for the concomitant estimation of adenosine and related purines in rat brain tissue preparations. The HPLC system consisted of C-18 column with UV-photodiode-array detection ranging from 210 to 400 nm, facilitating the online confirmation of peak purity. The column temperature was maintained at 30 degrees C and the injection volume was 20 muL. Elution with an isocratic mobile phase consisting of water/methanol/acetonitrile (88:5:7 by volume) at a flow rate of 0.8 mL/min yielded sharp, utmost-resolved peaks of adenosine (Ade), inosine (Ino), hypoxanthine (Hypoxan) and adenine (Adn) within 10 min. The method was validated with respect to the linearity, accuracy, precision, sensitivity, selectivity and stability. The method was also employed to estimate the naturally occurring purines in discrete regions of rat brain. A new protocol developed for tissue preparation utilizing H(2)SO(4) and Tris buffer gave well-resolved peaks and high component recoveries (>96%) which eliminated the need of an internal standard. The results show that the method for the determination of Ade, Ino, Hypoxan and Adn by RP-HPLC described here has good linearity, accuracy, precision, sensitivity, selectivity and is simple and rapid to perform. 相似文献
129.
The efficacy of the surface modification of fly ash by quarternary ammonium cations in the removal of dyes from aqueous solution is demonstrated. A series of organo-fly ash materials were synthesized by treating fly ash with quarternary ammonium cations such as tetraethylammonium, hexadecyltrimethylammonium, and benzyldimethyltetradecylammonium (TEA, HDTMA, and BDTDA). Two types of dyes were used for the investigation, disperse and anionic dyes. The effects of initial dye concentration, contact time, temperature, and the mechanism of dye sorption were investigated. The sorption was found to be affected by the structure and size of the quaternary ammonium cations as well as that of the dyes. Sorption of dyes was considerably enhanced by the surface modification. Thermodynamic parameters such as free energy (DeltaG0), enthalpy (DeltaH0), and entropy (DeltaS0) for the sorption process were also calculated. 相似文献