全文获取类型
收费全文 | 76篇 |
免费 | 1篇 |
专业分类
化学 | 53篇 |
力学 | 2篇 |
数学 | 7篇 |
物理学 | 15篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 2篇 |
2012年 | 8篇 |
2011年 | 4篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 2篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有77条查询结果,搜索用时 171 毫秒
61.
62.
Nonlinear Dynamics - Bayesian inference techniques have been used extensively in recent years for parameter estimation in nonlinear systems. Despite the many advances made in the field, highly... 相似文献
63.
Alana L. Rister Tiana L. Martin Eric D. Dodds 《Journal of mass spectrometry : JMS》2019,54(5):429-436
Steroid analysis is essential to the fields of medicine and forensics, but such analyses can present some complex analytical challenges. While chromatographic methods require long acquisition times and often provide incomplete separation, ion mobility spectrometry (IMS) as coupled to mass spectrometry (MS) has demonstrated significant promise for the separation of steroids, particularly in concert with metal adduction and multimerization. In this study, traveling wave ion mobility spectrometry (TWIMS) was employed to separate multimer steroid metal adducts of isomers in mixtures. The results show the ability to separate steroid isomers with a decrease in resolution compared with single component standards because of the formation of heteromultimers. Additionally, ion‐neutral collision cross sections (CCS) of the species studied were measured in the mixtures and compared with CCSs obtained in single component standards. Good agreement between these values suggests that the CCS may aid in identification of unknowns. Furthermore, a complex mixture composed of five sets of steroid isomers were analyzed, and distinct features for each steroid component were identified. This study further demonstrated the potential of TWIMS‐MS methods for the rapid and isomer‐specific study of steroids in biological samples for use either in tandem with or without chromatographic separation. 相似文献
64.
Veronica M. Piggott Scott C. Lloyd James I. Matchynski Shane A. Perrine Alana C. Conti 《Molecules (Basel, Switzerland)》2021,26(7)
The cannabinoid system is independently affected by stress and chronic ethanol exposure. However, the extent to which co-occurrence of traumatic stress and chronic ethanol exposure modulates the cannabinoid system remains unclear. We examined levels of cannabinoid system components, anandamide, 2-arachidonoylglycerol, fatty acid amide hydrolase, and monoacylglycerol lipase after mouse single-prolonged stress (mSPS) or non-mSPS (Control) exposure, with chronic intermittent ethanol (CIE) vapor or without CIE vapor (Air) across several brain regions using ultra-high-performance liquid chromatography tandem mass spectrometry or immunoblotting. Compared to mSPS-Air mice, anandamide and 2-arachidonoylglycerol levels in the anterior striatum were increased in mSPS-CIE mice. In the dorsal hippocampus, anandamide content was increased in Control-CIE mice compared to Control-Air, mSPS-Air, or mSPS-CIE mice. Finally, amygdalar anandamide content was increased in Control-CIE mice compared to Control-Air, or mSPS-CIE mice, but the anandamide content was decreased in mSPS-CIE compared to mSPS-Air mice. Based on these data we conclude that the effects of combined traumatic stress and chronic ethanol exposure on the cannabinoid system in reward pathway regions are driven by CIE exposure and that traumatic stress affects the cannabinoid components in limbic regions, warranting future investigation of neurotherapeutic treatment to attenuate these effects. 相似文献
65.
Andrew J. Clark Stuart R. Coles Alana Collis David R. Fullaway Nicholas P. Murphy Paul Wilson 《Tetrahedron letters》2009,50(46):6311-9061
Reaction of N-alkyl-N-arylsulfonyl-2-halo-propionamides with pentamethyldiethylenetriamine and either CuBr or CuCl leads to 2-aryl propionamides via initial radical generation, 1,4-aryl migration with loss of SO2 and reduction of the intermediate amidyl radical in 40-99% yields. 相似文献
66.
S.M. Collis R. Dall J. Howard D. Andruczyk B.W. James 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(6-7):340-346
A time-dependent collisional radiation model has been used to validate the use of a pulsed helium beam to measure electron temperature profiles in the H-1NF flexible heliac. The diagnostics technique is based on the measurement of helium spectral line ratios which are a strong function of electron temperature while being a weak function of electron density. The validation procedure involves comparing measured and calculated emissivities of spectral lines emitted by helium atoms as a function of position in the beam. 相似文献
67.
Alana Huszar Steffen Marcus Martin Ulirsch 《Journal of Pure and Applied Algebra》2019,223(5):2036-2061
The classical clutching and gluing maps between the moduli stacks of stable marked algebraic curves are not logarithmic, i.e. they do not induce morphisms over the category of logarithmic schemes, since they factor through the boundary. Using insight from tropical geometry, we enrich the category of logarithmic schemes to include so-called sub-logarithmic morphisms and show that the clutching and gluing maps are naturally sub-logarithmic. Building on the recent framework developed by Cavalieri, Chan, Wise, and the third author, we further develop a stack-theoretic counterpart of these maps in the tropical world and show that the resulting maps naturally commute with the process of tropicalization. 相似文献
68.
Tamires C. Lima Alana R. Ferreira Daniele F. Silva Edeltrudes O. Lima 《Natural product research》2018,32(5):572-575
Candida albicans is an important opportunistic fungal pathogen capable of provoking infection in humans. In the present study, we evaluated the antifungal effect of 23 ester derivatives of the cinnamic and benzoic acids against 3 C. albicans strains (ATCC-76645, LM-106 and LM-23), as well as discuss their Structure–Activity Relationship (SAR). The antifungal assay results revealed that the screened compounds exhibited different levels of activity depending on structural variation. Among the ester analogues, methyl caffeate (5) and methyl 2-nitrocinnamate (10) were the analogues that presented the best antifungal effect against all C. albicans strains, presenting the same MIC values (MIC = 128 μg/mL), followed by methyl biphenyl-2-carboxylate (21) (MIC = 128, 128 and 256 μg/mL for C. albicans LM-106, LM-23, and ATCC-76645, respectively). Our results suggest that certain molecular characteristics are important for the antifungal action. 相似文献
69.
J. Embery R. S. Graham R. A. Duckett D. Groves M. Collis M. R. Mackley T. C. B. McLeish 《Journal of Polymer Science.Polymer Physics》2007,45(4):377-394
To study the effect of processing history, molecular weight/molecular weight distribution, and thermal history on solid state properties (in particular fracture properties and orientation), carefully characterized polydisperse and monodisperse polystyrene samples were drawn above Tg and the orientation frozen in. The objective was to simulate the incidental orientation of polymer chains after processing, molding, and so forth (e.g., injection or compression, blow molding) as a result of melt flow. A series of polystyrene samples was produced by hot drawing at temperatures of 113 and 148 °C, followed by a relaxation period, and then a quench to below Tg. The level of segmental orientation imposed in the samples was determined by birefringence measurements. The tear energy of the sheets was measured at 20 °C by tearing along the draw direction, ultimately giving a value for the fracture energy, G3C. Samples of high draw ratio and low segmental orientation were unexpectedly found to have highly anisotropic fracture properties despite the low level of optical anisotropy. The fracture properties also depended significantly on whether the samples were drawn with or without lateral constraint. The results are compared with measurements of isotropic samples and the findings of a previous investigation utilizing SANS and birefringence. Modeling the drawing conditions at the chain level using a recent nonlinear tube theory explains how birefringence alone is an inadequate measure of molecular orientation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 377–394, 2007 相似文献
70.
Andrei Blasko Alana Leahy-Dios William O. Nelson Steven A. Austin Robert B. Killion Gary C. Visor Ian J. Massey 《Monatshefte für Chemie / Chemical Monthly》2001,132(7):789-798
Summary. The kinetic and thermodynamic solubilities of Roche (Ro) pharmaceutical compounds were determined by HPLC, titrimetry, and UV/Vis spectroscopy in aqueous buffers and in non-buffered
systems. For kinetic solubility, a turbidimetric method that allows the rapid determination of solubilities using small amounts
of compounds (5–50 mg) was used. Two types of precipitation were observed during the kinetic solubility determinations: i) a disperse precipitation where the solution became foggy with very small particles uniformly distributed in the solution,
and ii) discrete precipitation characterized by formation of crystals that rapidly sediment. The thermodynamic solubility was determined
by shake flask and titrimetrically using a pH-STAT. The pH-STAT titrimetric method for the pH-thermodynamic solubility profile determination eliminates the buffer species and represents a new way to approach the solubility
characterization of pharmaceutical compounds. The strengths of the turbidimetric method for determining the kinetic solubility
are its rapidity, minimal compound requirements, and suitability for high throughput screening. The limitations are that the
maximum solubility is limited to less than 100 mg · cm−3, and the precipitation of trace impurities cannot be distinguished from precipitation of the analyte. The pH-STAT titrimetric approach for the thermodynamic solubility has a lower throughput and is suitable for the characterization
of the lead candidate. It is not limited in its solubility range and provides a common basis for the comparison of the solubility
values at different pH values in contrast to traditional buffered systems.
Received August 21, 2000. Accepted (revised) February 5, 2001 相似文献