全文获取类型
收费全文 | 163篇 |
免费 | 6篇 |
国内免费 | 3篇 |
专业分类
化学 | 142篇 |
力学 | 2篇 |
数学 | 4篇 |
物理学 | 24篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 3篇 |
2014年 | 8篇 |
2013年 | 7篇 |
2012年 | 7篇 |
2011年 | 24篇 |
2010年 | 14篇 |
2009年 | 12篇 |
2008年 | 8篇 |
2007年 | 11篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1998年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1987年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1925年 | 1篇 |
排序方式: 共有172条查询结果,搜索用时 31 毫秒
81.
82.
83.
Bhupendra S. Rane Muddassar A. Kazi Sandeep M. Bagul Deepak P. Shelar Raghunath B. Toche Madhukar N. Jachak 《Journal of fluorescence》2010,20(1):415-420
A convenient route was successfully developed for the synthesis of novel heterocycles such as spiro-oxazino-quinoline derivatives
from 2-aminoquinoline-3-carbonitrile (4) in good yield. The Spiro-quinoline derivatives (6, 8 and 10) were synthesized and
further studied for their photophysical properties. Semiempirical molecular orbital calculation (PM3/PM6 for structure) proves
to be a suitable tool for the prediction of absorption and fluorescence properties of these compounds. 相似文献
84.
The enantioselective synthesis of some β-silyl γ-alkyl γ-butyrolactones has been achieved by an organo-catalyzed Michael addition of enolizable aldehydes onto a silylmethylene malonate followed by a silicon-facilitated Bayer–Villiger oxidation of the β-silyl aldehyde adducts as the key step. γ-Alkyl γ-butenolides were obtained from the β-silyl γ-alkyl γ-butyrolactones by Fleming–Tamao oxidation of the silyl group to a hydroxy group and subsequent elimination. These butenolides are the advanced intermediates of some natural products such as (+)-γ-caprolactone, (+)-methylenolactocine, and (?)-quercus lactone. 相似文献
85.
4-Hetero-1-yl-2-bromothieno[3,2-c]pyridines 3(a–d) were synthesized by the reaction of 2-bromo-4-chlorothieno[3,2-c]pyridine (1) and cyclic amine 2(a–d), which on Suzuki coupling with substituted boronic acids 4(a–f) exclusively converted to corresponding 4-hetero -1-yl-2-arylthieno[3,2-c]pyridine 5(a–x) in good yields. The effect of donor-acceptor substituent on absorption emission properties and fluorescent quantum yield of new thienopyridine derivatives 5(a-x) were studied. 相似文献
86.
Vadde Ravinder Sigala Ashok M. Satish Varma C. V. Raghunath Babu Kanne Shanker Gubba Balaswamy 《Chromatographia》2009,70(1-2):229-232
A rapid isocratic chiral LC method has been developed for the separation of (S)-cinacalcet from (R)-cinacalcet. Good resolution with R S > 3 was obtained using a Chiralpak-IA column (250 × 4.6 mm, particle size 5 μm) and n-hexane, ethanol and trifluoroacetic acid as the mobile phase (95:5:0.1, v/v) at ambient temperature. Flow rate was kept at 1.0 mL min–1 and elution was monitored by UV detection at 223 nm. This method was further used to determine the presence of (S)-cinacalcet in enantiopure pharmaceutical formulations containing (R)-cinacalcet. This method allowed for the detection and quantitation of (S)-cinacalcet of levels at 0.04 and 0.16 μg mL–1, respectively. The method was validated following ICH guidelines. 相似文献
87.
Nalawade Pravin Aware Babasaheb Dand Neha Kadam Vilasrao Hirlekar Rajashree 《Journal of inclusion phenomena and macrocyclic chemistry》2009,65(3-4):377-383
In this work, we illustrate the usefulness of cyclodextrins, namely, methyl-β-cyclodextrin (MβCD), an amorphous, methylated derivative of the natural β-cyclodextrin, as a tool to form an inclusion complex with Valsartan (VAL), a poorly water soluble drug. The phase solubility study showed AL type of curve with slope less than one indicating the formation of complexes in 1:1 molar ratio of drug and CD. The stability constant was found to be 538.14 ± 5.4 Mole?1. Solid binary systems between VAL and MβCD were prepared experimentally in a stoichiometry 1:1 by different techniques (physical mixing, kneading, co-evaporation). Afterward these products were characterized by Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), Scanning electron microscopy (SEM) and 1H Nuclear magnetic resonance study (1H NMR). The results obtained suggested that co-evaporation methods yield a higher degree of amorphous entities suggesting the formation of inclusion complex between VAL and MβCD. The dissolution of VAL from the binary systems was studied to select the most appropriate system for the formulation development. It was concluded that the preparation technique played an important role in the dissolution behavior of the drug and the inclusion complex between VAL and MβCD obtained by co-evaporation method allowed better performance. 相似文献
88.
Gas-phase kinetics and mechanisms of SiH(3) reactions with SiH(4), Si(2)H(6), Si(3)H(8), and Si(4)H(10), processes of relevance to a-Si thin-film deposition, have been investigated by ab initio molecular orbital and transition-state theory (TST) calculations. Geometric parameters of all the species involved in the title reactions were optimized by density functional theory at the B3LYP and BH&HLYP levels with the 6-311++G(3df,2p) basis set. The potential energy surface of each reaction was refined at the CCSD(T)/6-311++G(3df,2p) level of theory. The results show that the most favorable low energy pathways in the SiH(3) reactions with these silanes occur by H abstraction, leading to the formation of SiH(4) + Si(x)H(2x+1) (silanyl) radicals. For both Si(3)H(8) and n-Si(4)H(10) reactions, the lowest energy barrier channels take place by secondary Si-H abstraction, yielding SiH(4) + s-Si(3)H(7) and SiH(4) + s-Si(4)H(9), respectively. In the i-Si(4)H(10) reaction, tertiary Si-H abstraction has the lowest barrier producing SiH(4) + t-Si(4)H(9). In addition, direct SiH(3)-for-X substitution reactions forming Si(2)H(6) + X (X = H or silanyls) can also occur, but with significantly higher reaction barriers. A comparison of the SiH(3) reactions with the analogous CH(3) reactions with alkanes has been made. The rate constants for low-energy product channels have been calculated for the temperature range 300-2500 K by TST with Eckart tunneling corrections. These results, together with predicted heats of formation of various silanyl radicals and Si(4)H(10) isomers, have been tabulated for modeling of a-Si:H film growth by chemical vapor deposition. 相似文献
89.
90.
Mata Prasad Dasharath Lal Shrivastava Raghunath Sahai Gupta 《Colloid and polymer science》1925,37(2):101-104
Ohne Zusammenfassung
Deutsch von Johannes Albrecht. 相似文献