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71.
Everaldo Medeiros Kyril Tintarev 《Nonlinear Analysis: Theory, Methods & Applications》2010,72(5):2170-2177
We establish some multiplicity results for a class of boundary value problems involving the Hardy-Sobolev operator using Morse theory. 相似文献
72.
Total syntheses of (+)-norsecurinine and (+)-allonorsecurinine are described that utilize a rhodium carbenoid-initiated O-H insertion/Claisen rearrangement/1,2-allyl migration domino process for the stereoselective introduction of the tertiary alcohol moiety. Overall the employed strategy is flexible and will allow access to other members of the Securinega family of alkaloids. 相似文献
73.
Regina M. Takeuchi André L. Santos Maria J. Medeiros Nelson R. Stradiotto 《Mikrochimica acta》2009,164(1-2):101-106
A linear sweep anodic stripping voltammetric method was developed for copper determination in commercial ethanol fuel samples by using a gold microelectrode. Under the optimized conditions, a linear range from 0.05 to 1.0 μM was obtained, with detection limit of 22 nM. The method was employed to determine copper ions in six commercial ethanol fuel samples and the results were compared with those obtained by FAAS. This study showed that for most samples both methods produced concordant results. However, for two samples, copper is distributed in its labile and complexed forms leading to copper contents contrasting with those obtained by flame atomic absorption spectroscopy (FAAS). It was observed that acidification of the samples is a very efficient way to recover copper from its complexed forms. After acidification, the copper contents obtained were concordant with those obtained by FAAS. Thus, the method can be employed to the reliable copper determination in commercial ethanol fuel samples. Moreover, this is the first work providing some insights about copper speciation in commercial ethanol fuel samples. 相似文献
74.
The stability constants of the 1:1 and 1:2 complexes of nickel and copper(II) with beta-ethylthioethylenethioglycollic acid have been determined at 25 degrees at ionic strength 1.0 (NaClO(4)). The values for the nickel complexes are K(1) = 1.11 +/- 0.06 x 10(2) (spectrophotometrically) or 1.25 +/- 0.11 x 10(2) (potentiometrically) and K(2) = 3.04 +/- 0.24 x 10(2) (potentiometrically). The corresponding values for the copper complexes are K(1) = 1.27 +/- 0.02 x 10(3) or 1.28 +/- 0.03 x 10(3) and K(2) = 7.29 +/- 0.30 x 10(2). 相似文献
75.
The discovery of multilocal DNA fingerprinting represented a revolution in criminal identification and paternity testing. However, for routine use in clinical laboratories, the standard DNA fingerprint methodology is too complex. We have been successful in the development of a simplified DNA nonisotopic fingerprinting system using biotin-labeled probes which we have called DNA bioprints. To achieve this we explored three main technical features: utilization of biotinylated nonradioactive probes as a simpler substitute for 32P-labeled probes, utilization of oligonucleotide probes as a simpler substitute for recombinant probes, and direct hybridization in the dried agarose gel as a simpler substitute for Southern blots. In this article we review our results in the development of DNA bioprints. 相似文献
76.
Glaucia R. Martinez Flávia Garcia Jean Cadet Graziella E. Ronsein Marisa H.G. Medeiros 《Tetrahedron》2006,62(46):10762-10770
We report herein the synthesis of a new hydrophilic and non-ionic anthracene derivative, the N,N′-di-(2,3-dihydroxypropyl)-9,10-anthracenedipropanamide. The evaluation of this compound as chemical trap of singlet molecular oxygen by using labeling experiments and HPLC-MS analysis showed that it could be efficiently used in biological investigations. 相似文献
77.
Nucleating Effect and Dynamic Crystallization of a Poly(propylene)/Attapulgite System 总被引:3,自引:0,他引:3
Medeiros E. S. Tocchetto R. S. Carvalho L. H. Conceição M. M. Souza A. G. 《Journal of Thermal Analysis and Calorimetry》2002,67(2):279-285
In this work, the influence of attapulgite concentration on the nucleating efficiency of isotactic polypropylene (iPP) and
on the kinetics of non-isothermal crystallization were ascertained.The study was conducted by DSC. The nucleating efficiency
was determined according to the procedure described by Fillon and the kinetics of non-isothermal crystallization was determined
using Ozawa's method using cooling rates of 2, 5 and 10°C min−1.Our results indicate that both the relative crystallinity and the crystallization temperature increase with filler content
and that a maximum occurs at 2% mass/mass filler content. Both parameters decrease with increasing cooling rates. The Ozawa's
exponent tended to increase with temperature and filler content.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
78.
S.K. Medeiros E.L. Albuquerque F.F. Maia Jr. E.W.S. Caetano V.N. Freire 《Chemical physics letters》2006,430(4-6):293-296
Density functional theory ab initio calculations of the structural parameters, electronic structure, carriers effective masses, and optical absorption of the CaCO3 aragonite polymorph were performed within the local density and generalized gradient approximations, local density approximation (LDA) and generalized gradient approximation (GGA) respectively. A good agreement between the calculated lattice parameters and experimental results was obtained. Both the LDA and GGA results for CaCO3 aragonite exhibit very close indirect and direct energy gaps, and the computed effective masses are heavy and anisotropic. Two optical absorption regimes related to distinct electronic transitions are predicted by the calculations. 相似文献
79.
80.
A. C. D. de Medeiros N. A. B. de Cervantes A. P. B. Gomes R. O. Macêdo 《Journal of Thermal Analysis and Calorimetry》2001,64(2):745-750
TG and DSC data were used to determine the thermal parameters of prednisone drug and tablets. Two formulations of prednisone
20 mg were analysed in the form of tablets. The TG curves of prednisone drug and tablets A and B displayed six, eight and
seven thermal decomposition processes, respectively. Analysis of the DSC data pointed to chemical interactions between prednisone
drug and the excipients of tablets A and B, suggested by alterations in the melting temperature of prednisone. The analysis
revealed that prednisone drug is more stable than tablets A and B.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献