全文获取类型
收费全文 | 81篇 |
免费 | 0篇 |
专业分类
化学 | 42篇 |
晶体学 | 4篇 |
力学 | 3篇 |
数学 | 5篇 |
物理学 | 27篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2012年 | 6篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 6篇 |
2008年 | 1篇 |
2007年 | 6篇 |
2006年 | 1篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 4篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 3篇 |
排序方式: 共有81条查询结果,搜索用时 15 毫秒
51.
Martins-Bach AB Bloise AC Vainzof M Rahnamaye Rabbani S 《Magnetic resonance imaging》2012,30(8):1167-1176
Duchenne muscular dystrophy (DMD) is a recessive X-linked form of muscular dystrophy characterized by progressive and irreversible degeneration of the muscles. The mdx mouse is the classical animal model for DMD, showing similar molecular and protein defects. The mdx mouse, however, does not show significant muscle weakness, and the diaphragm muscle is significantly more degenerated than skeletal muscles. In this work, (1)H magnetic resonance spectroscopy (MRS) was used to study the metabolic profile of quadriceps and diaphragm muscles from mdx and control mice. Using principal components analysis (PCA), the animals were separated into groups according to age and lineages. The classification was compared to histopathological analysis. Among the 24 metabolites identified from the nuclear MR spectra, only 19 were used by the PCA program for classification purposes. These can be important key biomarkers associated with the progression of degeneration in mdx muscles and with natural aging in control mice. Glutamate, glutamine, succinate, isoleucine, acetate, alanine and glycerol were increased in mdx samples as compared to control mice, in contrast to carnosine, taurine, glycine, methionine and creatine that were decreased. These results suggest that MRS associated with pattern recognition analysis can be a reliable tool to assess the degree of pathological and metabolic alterations in the dystrophic tissue, thereby affording the possibility of evaluation of beneficial effects of putative therapies. 相似文献
52.
Reis CM Pereira DS Paiva Rde O Kneipp LF Echevarria A 《Molecules (Basel, Switzerland)》2011,16(12):10668-10684
We present an efficient procedure for the synthesis of thirty-six N?,N?-substituted thiosemicarbazones, including twenty-five ones that are reported for the first time, using a microwave-assisted methodology for the reaction of thiosemicarbazide intermediates with aldehydes in the presence of glacial acetic acid in ethanol and under solvent free conditions. Overall reaction times (20-40 min when ethanol as solvent, and 3 min under solvent free conditions) were much shorter than with the traditional procedure (480 min); satisfactory yields and high-purity compounds were obtained. The thiosemicarbazide intermediates were obtained from alkyl or aryl isothiocyanates and hydrazine hydrate or phenyl hydrazine by stirring at room temperature for 60 min or by microwave irradiation for 30 min, with lower yields for the latter. The preliminary in vitro antifungal activity of thiosemicarbazones was evaluated against Aspergillus parasiticus and Candida albicans. 相似文献
53.
C. A. B. Silva Aurea R. Vasconcellos J. Galvão Ramos Roberto Luzzi 《Journal of statistical physics》2011,143(5):1020-1034
A kinetic equation for the single particle distribution function in an open many-body system, when in far away from equilibrium
conditions is derived in the context of a Non-Equilibrium Thermo-Statistics of ample scope. It consists of a generalization
of traditional kinetic equations in that no restrictions are imposed on the characteristics of the nonequilibrium thermodynamic
state of the system. This kinetic equation do contain some contributions that become relevant in systems with a nonlinear
kinetics when driven sufficiently far from equilibrium (certain complex systems). Moreover, the handling of the kinetic equation
in a multiple-moment approach provides a generalized nonlinear higher-order thermo-hydrodynamics. 相似文献
54.
Suspect and nontarget screening approaches to identify organic contaminant records in lake sediments
Aurea C. Chiaia-Hernandez Emma L. Schymanski Praveen Kumar Heinz P. Singer Juliane Hollender 《Analytical and bioanalytical chemistry》2014,406(28):7323-7335
Sediment cores provide a valuable record of historical contamination, but so far, new analytical techniques such as high-resolution mass spectrometry (HRMS) have not yet been applied to extend target screening to the detection of unknown contaminants for this complex matrix. Here, a combination of target, suspect, and nontarget screening using liquid chromatography (LC)-HRMS/MS was performed on extracts from sediment cores obtained from Lake Greifensee and Lake Lugano located in the north and south of Switzerland, respectively. A suspect list was compiled from consumption data and refined using the expected method coverage and a combination of automated and manual filters on the resulting measured data. Nontarget identification efforts were focused on masses with Cl and Br isotope information available that exhibited mass defects outside the sample matrix, to reduce the effect of analytical interferences. In silico methods combining the software MOLGEN-MS/MS and MetFrag were used for direct elucidation, with additional consideration of retention time/partitioning information and the number of references for a given substance. The combination of all available information resulted in the successful identification of three suspect (chlorophene, flufenamic acid, lufenuron) and two nontarget compounds (hexachlorophene, flucofuron), confirmed with reference standards, as well as the tentative identification of two chlorophene congeners (dichlorophene, bromochlorophene) that exhibited similar time trends through the sediment cores. This study demonstrates that complementary application of target, suspect, and nontarget screening can deliver valuable information despite the matrix complexity and provide records of historical contamination in two Swiss lakes with previously unreported compounds. 相似文献
55.
56.
Homoallylic thioethers facilitate the platinum-catalyzed hydrosilylation of olefins with phenyldimethylsilane. As a control, thioether substrates are shown to hydrosilylate at room temperature under conditions where no hydrosilylation is observed for isosteric substrates that lacked thioether groups. Modest diastereoselection is observed, between 2 and 5 to 1. Hydrogenation is a competing reaction that becomes prominent for internal olefins. The internal diene 6a undergoes regioselective 1,2-hydrogenation of the double bond proximal to the homoallyl thioether moiety. 相似文献
57.
The dynamics of evolution of the LO-phonon population in semiconductors under high levels of optical excitation is determined. Collision operators are written in a Boltzmann-like form, with the relaxation-times being a functional of the nonequilibrium thermodynamic parameters which describe the instantaneous macroscopic state of the whole system. The expected behavior of the relaxation channels under different experimental constraints is discussed. 相似文献
58.
Minimum volume stability limits for axisymmetric liquid bridges subject to steady axial acceleration
In this paper the influence of an axial microgravity on the minimum volume stability limit of axisymmetric liquid bridges between unequal disks is analyzed both theoretically and experimentally. The results here presented extend the knowledge of the static behaviour of liquid bridges to fluid configurations different from those studied up to now (almost equal disks). Experimental results, obtained by simulating microgravity conditions by the neutral buoyancy technique, are also presented and are shown to be in complete agreement with theoretical ones. 相似文献
59.
Arturo San Feliciano Alejandro F. Barrero Manuel Medarde Jose M.Miguel Del Corral Arrate Aramburu Aurea Perales Jose Fayos Francisco Sanchez-Ferrando 《Tetrahedron》1985,41(23):5711-5717
The application of X-ray diffraction methods has shown that the configurations of Asteriscunolides A and B at the Δ9 double bond are Z, rather than those previously proposed E, while the stereochemistries of Asteriscunolides C and D were correctly established. Some unexpected NMR data and the new assignment of the spectral signals, based on 2D-NMR correlations and NOE-difference experiments are reported. 相似文献
60.
J. Grucker J.-C. Karam F. Correia F. Perales G. Vassilev V. Bocvarski S. M. Chérif J. Baudon M. Ducloy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):467-474
Diffraction of thermal velocity metastable atoms by non-magnetic and
magnetic reflection gratings of micrometric period has been observed. This
observation is made possible by the use of an ultra narrow beam generated by
metastability exchange. Grazing incidence angles are exploited to minimise
the quenching of metastable atoms on the grating surface. Potential
applications are beam splitting, atom holography and probing of micro-sized
solid surfaces. 相似文献