全文获取类型
收费全文 | 290篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
化学 | 196篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 18篇 |
物理学 | 79篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 37篇 |
2010年 | 18篇 |
2009年 | 13篇 |
2008年 | 11篇 |
2007年 | 11篇 |
2006年 | 17篇 |
2005年 | 16篇 |
2004年 | 5篇 |
2003年 | 14篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 7篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1975年 | 1篇 |
1972年 | 3篇 |
1969年 | 1篇 |
排序方式: 共有299条查询结果,搜索用时 0 毫秒
101.
Results of a quasi-harmonic calculation of the normal mode frequencies, mode-Grüneisen parameters, the coefficient of thermal expansion α, the heat capacity Cp, and the macroscopic Grüneisen function γ(itT) for CsBr and CsI are presented. Very good agreement with the experimental results for α and Cp is obtained. A self-consistent procedure is used to parametrize the models so that some often neglected vibrational and configuration-dependent effects can be accounted for. Predictions are made for the values that the potential energy derivatives and the elastic constants would have in the absence of vibrational motion. 相似文献
102.
Partha Ghosal Sama Ajay Sanjeev Meena Sudhir Sinha Arun K. Shaw 《Tetrahedron: Asymmetry》2013,24(15-16):903-908
The stereoselective synthesis of Jaspine B has been achieved from easily available (S)-Garner’s aldehyde. The trisubstituted tetrahydrofuran core of Jaspine B was constructed by utilizing a diastereoselective iodocyclization as the key step. Deiodination and debenzylation were performed in a single step by using n-Bu3SnH and ABCN as a conjugate catalyst system. The in vitro cytotoxicity of compounds 1 and 1a against 3 human cancer cell lines-A549 (lung), MCF7 (breast), and KB (oral); and a non-cancer cell line (NIH3T3) was determined by sulphorhodamine B based assay. 相似文献
103.
104.
In this paper, we present a validated UPLC‐MS/MS assay for determination of ramipril and ramiprilat from human plasma samples. The assay is capable of isolating phase II metabolites (acylglucornides) of ramipril from in vivo study samples which is otherwise not possible using conventional HPLC conditions. Both analytes were extracted from human plasma using solid‐phase extraction technique. Chromatographic separation of analytes and their respective internal standards was carried out using an Acquity UPLC BEH C18 (2.1 × 100 mm), 1.7 µm column followed by mass spectrometric detection using an Waters Quattro Premier XE. The method was validated over the range 0.35–70.0 ng/mL for ramipril and 1.0–40.0 ng/mL for ramiprilat. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
105.
We describe a NMR strategy to resolve temperature-gradient-monitored real-time chemical reaction involving a [3 + 3]-cyclocondensation reaction between alkynone and ethyl 2-amino-1H-indole-3-carboxylate toward the synthesis of pyrimido[1,2-a]indole catalyzed by Cs2CO3. The in situ NMR study clearly indicates that the reactant undergoes [3 + 3]-cyclocondensation reaction through a concerted mechanism, resulting in the product formation. The detailed NMR spectroscopic data led to the optimization of the reaction conditions and quantitative analysis of the product accurately and efficiently. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
106.
Baryon-antibaryon widths of the “true” diquoniums are calculated using the quark-pair-creation model, otherwise very successful for the decays of ordinary baryons and mesons. The resulting widths are one order of magnitude smaller than generally believed. Combined with an earlier study of diquonium decays into mesonic channels, this would avoid the need for “mock” configurations and make it difficult to interpret structures with widths ≈ 100 MeV as diquoniums. 相似文献
107.
Rane MR Sarode PD Chaudhari BL Chincholkar SB 《Applied biochemistry and biotechnology》2008,151(2-3):665-675
Biocontrol ability of Pseudomonas aeruginosa ID 4365, a biocontrol agent of groundnut phytopathogens from marine origin, was previously attributed to the production of pyoverdin type of siderophores. However, pyoverdin-rich supernatants of this organism showed better antifungal activity compared to equivalent amount of purified pyoverdin indicating presence of undetected metabolite(s) in pyoverdin rich supernatants. On the basis of observation that antagonistic activity was iron-dependent and iron-independent, an attempt was made to detect the presence of additional metabolites. In addition to pyoverdin, strain produced additional siderophores, viz. pyochelin and salicylic acid. Two broad spectrum antifungal compounds, viz. pyocyanin and phenazine-1-carboxylic acid, were detected, characterized, and activity against phytopathogens was demonstrated. Iron- and phosphate-dependent co-production of siderophores and phenazines was confirmed. Strain showed additional features like production of hydrogen cyanide, indol-3-acetic acid, and phosphate solubilization. 相似文献
108.
Jacob JA Mahal HS Biswas N Mukherjee T Kapoor S 《Langmuir : the ACS journal of surfaces and colloids》2008,24(2):528-533
We demonstrate that dihydroxy benzenes are excellent reducing agents and may be used to reduce silver ions to synthesize stable silver nanoparticles in air-saturated aqueous solutions. The formation of Ag nanoparticles in deaerated aqueous solution at high pH values suggests that the reduction of silver ions occurs due to oxidation of dihydroxy benzenes and probably on the surface of Ag2O. Pulse radiolysis studies show that the semi-quinone radical does not participate in the reduction of silver ions at short time scales. Nevertheless, results show that primary intermediates undergo slower transformation in the presence of dihydroxy benzenes than in their absence. This slow transformation eventually leads to the formation of silver nanoparticles. The Ag nanoparticles were characterized by UV-vis absorption spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). XRD and TEM techniques showed the presence of Ag nanoparticles with an average size of 30 nm. 相似文献
109.
Aqueous solutions of amphiphilic polymers usually comprise of inter- and intramolecular associations of hydrophobic groups often leading to a formation of a rheologically significant reversible network at low concentrations that can be identified using techniques such as static light scattering and rheometry. However, in most studies published till date comparing water soluble polymers with their respective amphiphilic derivatives, it has been very difficult to distinguish between the effects of molecular mass versus hydrophobic associations on hydrodynamic (intrinsic viscosity [η]) and thermodynamic parameters (second virial coefficient A 2), owing to the differences between their degrees of polymerization. This study focuses on the dilute and semi-dilute solutions of hydroxyethyl cellulose (HEC) and its amphiphilic derivatives (hmHEC) of the same molecular mass, along with other samples having a different molecular mass using capillary viscometry, rheometry and static light scattering. The weight average molecular masses (M W ) and their distributions for the non-associative HEC were determined using size exclusion chromatography. Various empirical approaches developed by past authors to determine [η] from dilute solution viscometry data have been discussed. hmHEC with a sufficiently high degree of hydrophobic modification was found to be forming a rheologically significant network in dilute solutions at very low concentrations as opposed to the hmHEC with a much lower degree of hydrophobic modification which also enveloped the hydrophobic groups inside the supramolecular cluster as shown by their [η] and A 2. The ratio A 2 M W /[η], which takes into account hydrodynamic as well as thermodynamic parameters, was observed to be less for associative polymers compared to that of the non-associative polymers. 相似文献
110.
Chita Ranjan Sahoo Jyotirmaya Sahoo Monalisa Mahapatra Debananda Lenka Pratap Kumar Sahu Budheswar Dehury Rabindra Nath Padhy Sudhir Kumar Paidesetty 《Arabian Journal of Chemistry》2021,14(2):102922
Nowadays, bacterial infections epitomize significant health threats globally with an increased morbidity and mortality. Most contemporary antibacterial agents are resisted by pathogenic bacteria - the multidrug resistant (MDR) bacterial strains arising from cross resistances operative in natural bacterial consortia inside human body and in environments. Consequently, the development of newer potential drug candidate(s) is required against the broad spectrum of MDR bacteria. Indeed, the phytochemical coumarin and its derivatives had been reported with broad biological inhibitory properties, including antibacterial activities. In this review, several methods of synthetic strategies of coumarin derivatives as antibacterials were considered with individual schematic compounds by structure-activity relationship (SAR) studies as essential corollaries. Overall, substituents at positions C-3 and C-4 of coumarin are coveted for the development of newer antibacterial agents. 相似文献