全文获取类型
收费全文 | 188篇 |
免费 | 12篇 |
专业分类
化学 | 159篇 |
晶体学 | 8篇 |
力学 | 4篇 |
数学 | 6篇 |
物理学 | 23篇 |
出版年
2022年 | 7篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 9篇 |
2013年 | 14篇 |
2012年 | 15篇 |
2011年 | 19篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 8篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1995年 | 2篇 |
1993年 | 3篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1962年 | 2篇 |
1961年 | 2篇 |
排序方式: 共有200条查询结果,搜索用时 15 毫秒
1.
Vutukuri DR Bharathi P Yu Z Rajasekaran K Tran MH Thayumanavan S 《The Journal of organic chemistry》2003,68(3):1146-1149
A mild deprotection strategy for allyl ethers under basic conditions in the presence of a palladium catalyst is described. Under these conditions, aryl allyl ethers can be cleaved selectively in the presence of alkyl allyl ethers. These conditions are also effective in the deprotection of allyloxycarbonyl groups. The utility of the current methodology in sequence specific dendrimer synthesis is demonstrated. 相似文献
2.
A simple spectrophotometric method for determination of isoxsuprine hydrochloride in pharmaceuticals
A spectrophotometric method has been developed for the determination of isoxsuprine hydrochloride and its dosage forms, based on its coupling reaction with diazotized sulphanilic acid. The yellow chromophore has an absorption maximum at 440 nm. Beer's law holds over the range 0.8-8 mu/ml in the final solution. 相似文献
3.
[reaction: see text] Direct asymmetric catalytic Michael reactions have been performed using chiral-amine/acid bifunctional catalysts. Performed with 0.3 equiv of (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine and 0.3 equiv of trifluoroacetic acid as the catalyst, the reaction of alpha,alpha-dialkylaldehydes with (E)-beta-nitrostyrene provided the alpha,alpha-dialkyl Michael products in up to 96% yield with up to 91% ee. With respect to enantioselectivity, l-proline was a poor catalyst of this class of Michael reactions. 相似文献
4.
Glass-ceramic was prepared by sol–gel method using Ca(NO3)2·4H2O and P2O5 as Ca and P precursors, respectively. In order to improve the bioactivity of the implant material, glass-ceramic (β-Ca2P2O7) coating was developed on 316L SS substrate by spin coating method. Coating was annealed at different temperatures and its
corrosion resistance was evaluated by electrochemical polarization and impedance analysis using Ringer’s solution as electrolyte.
The results from the present study, show excellent corrosion resistance for coated 316L SS, corroborated by the high values
of charge transfer resistance from impedance analysis and higher breakdown and repassivation potential with the corresponding
lower current density from polarization measurements. Based on the results, the glass-ceramic coating on 316L SS can be considered
as a corrosion resistant material. 相似文献
5.
Chikkannagari Nagamani Jing Guo S. Thayumanavan 《Journal of polymer science. Part A, Polymer chemistry》2012,50(6):1187-1196
Biaryl hydroxy polymers with orthogonal disposition of proton transporting ? OH moieties have been synthesized via conventional free radical polymerization. The polymers are characterized for their thermal stability and proton conductivity, and the results are compared with the corresponding styrenic hydroxy polymers. The orthogonal disposition of ? OH moieties in biaryl polymers does result in lower Ea for proton transport. However, the lower Ea values in biaryl polymers did not translate into a net increase in proton conductivity. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
6.
Priyanka Lohar Manish Kumar Sharma Amit Kumar Sahu Rajeswari Rathod Pinaki Sengupta 《Biomedical chromatography : BMC》2019,33(12)
The combination of acebrophylline (ABP), levocetirizine (LCZ) and pranlukast (PRN) is used to treat allergic rhinitis, asthma, hay‐fever and other conditions where patients experience difficulty in breathing. This study was carried out with the aim of developing and validating a reverse‐phase high‐performance liquid chromatographic bioanalytical method to simultaneously quantitate ABP, LCZ and PRN in rat plasma. The objective also includes determination of the pharmacokinetic interaction of these three drugs after administration via the oral route after individual and combination treatment in rat. Optimum resolution between the analytes was observed with a C18 Kinetex column (250 mm × 4.6 mm × 5 μm). The chromatography was performed in a gradient elution mode with a 1 mL/min flow rate. The calibration curves were linear over the concentration range of 100–1600 ng/mL. The intra‐ and inter‐day precision and accuracy were found to be within acceptable limits as specified in US Food and Drug Administration guideline for bioanalytical method validation. The analytes were stable on the bench‐top (8 h), after three freeze–thaw cycles, in the autosampler (8 h) and as a dry extract (?80°C for 48 h). The statistical results of the pharmacokinetic study in Sprague–Dawley rats showed a significant change in pharmacokinetic parameters for PRN upon co‐administration of the three drugs. 相似文献
7.
Seth Sheeba Thavamani Murugesan Sudharsan Anitha Santhana Mariya Devarajan Suresh Arlin Jose Amali Sanniyasi Rajeswari Thomas Peter Amaladhas 《应用有机金属化学》2020,34(9):e5752
The catalytic activity of CeO2 and palladium nanoparticles supported fly ash zeolite (CeO2/Pd@FAZ) for Csp2-Csp2 bond formation was studied. CeO2/Pd@FAZ was characterized by FTIR, XRD, EDAX and TEM studies. In the Suzuki-Miyauracross-coupling reaction, biphenyl derivatives with excellent yields were obtained, and the reaction conditions were optimized. The catalytic activity was explored using a wide variety of diversely substituted aryl bromides and chlorides with aryl boronic acid under optimized reaction conditions. The recyclability of the catalyst was established for three cycles, with the conversion rate from 99 to 40%, which gained the advantage of heterogeneous catalysis. 相似文献
8.
9.
A. Sengupta B. Rajeswari R. M. Kadam R. J. Kshirsagar 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(2):903-908
The use of serpentine as a potential nuclear shielding material necessitates a chemical quality control of the samples before
its use in reactors. With this in view, characterization of these mineral samples was carried out using inductively coupled
plasma atomic emission spectrometry (ICP-AES) and Instrumental neutron activation analysis (INAA) methods. The analytical
results obtained by both ICP-AES and NAA techniques were found to be comparable. Na, Cr, Co, Zn, and Cu were found to be present
in all samples of Indian origin while Ga, Ag, Ni, and Cd were found to below the limits of detection. A comparison on the
detection limits of elements of interest was also carried out by both the analytical techniques and found to be in good agreement.
An infrared spectroscopic investigation was also carried out on all the mineral samples. Bands at 3,689 and 3,648 cm−1 were attributed to inner and outer hydroxyl stretching of Mg–OH, respectively. The weak and broad band centered around 3,416 cm−1 was assigned due to the stretching vibrations of the adsorbed water molecules while three bands at 1076, 1022 and 968 cm−1 were prescribed to the vibrations of the SiO4 tetrahedra. 相似文献
10.
N. Rajeswari R. Nagarathinam S. Viswanathan H. Kothandaraman E. Ponnusamy 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1585-1610
New polymaleamides were synthesized by ring-opening polyaddition of N,N'-biphenylbismaleimide (BPBMI) to the aliphatic diamines 1,4-diaminobutane, 1,6-diaminohexane, 1,8-diaminooctane, piperazine, and 2,5-dimethylpiperazine in m-cresol. The appropriate model compound was also prepared. These polymers are completely soluble in concentrated sulfuric acid as well as in m-cresol and are found to be insoluble in common organic solvents. The identities of BPBMI, the model compound, and the polymaleamides were confirmed by elemental analysis and IR spectroscopy. These polymaleamides were found to have inherent viscosities in the range 0.10–0.14 dL/g. Their IR spectra reveal the retention of cis-geometry about the C=C bonds in BPBMI and in the polymaleamides. The thermal degradation behavior of the polymaleamides was studied by thermogravimetric analysis, differential scanning calorimetry, and mass spectrometry. Fragmentation schemes for the polymaleamides are proposed. 相似文献