全文获取类型
收费全文 | 138篇 |
免费 | 3篇 |
专业分类
化学 | 69篇 |
晶体学 | 6篇 |
力学 | 6篇 |
数学 | 43篇 |
物理学 | 17篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 8篇 |
2012年 | 6篇 |
2011年 | 11篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 5篇 |
2007年 | 9篇 |
2006年 | 9篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1987年 | 1篇 |
排序方式: 共有141条查询结果,搜索用时 0 毫秒
21.
Jean-Claude Jumas Moulay Tahar Sougrati Alexis Perea Laurent Aldon Josette Olivier-Fourcade 《Hyperfine Interactions》2013,217(1-3):107-115
The performances of Li-ion batteries depend on many factors amongst which the important ones are the electrode materials and their structural and electronic evolution upon cycling. For a better understanding of lithium reactivity mechanism of many materials the combination of X-Ray Powder Diffraction (XRPD) and Transmission Mössbauer Spectroscopy (TMS) providing both structural and electronic information during the electrochemical cycling has been carried out. Thanks to the design of a specific electrochemical cell, derived from a conventional Swagelock cell, such measurements have been realised in operando mode. Two examples illustrate the greatness of combining XRPD and TMS for the study of LiFe0.75Mn0.25PO4 as positive electrode and TiSnSb as negative electrode. Different kinds of insertion or conversion reactions have been identified leading to a better optimization and design of performing electrodes. 相似文献
22.
Lgaz Hassane Chaouiki Abdelkarim Albayati Mustafa R. Salghi Rachid El Aoufir Yasmina Ali Ismat H. Khan Mohammad I. Mohamed Shaaban K. Chung Ill-Min 《Research on Chemical Intermediates》2019,45(4):2269-2286
Research on Chemical Intermediates - Mild steel corrosion in HCl solution is an example of corrosion in acidic mediums. The ongoing research efforts to develop novel environmentally friendly... 相似文献
23.
Hassane Assaaoudi Ian S. Butler Janusz A. Kozinski 《Journal of chemical crystallography》2006,36(11):723-733
A new manganese(II) pyrophosphate, Mn4(P2O7)2·10H2O, has been synthesized and characterized by single-crystal X-ray diffraction [orthorhombic space group Pnma, with unit cell parameters of a=9.3288(3) ?, b=25.9532(9) ?, c=8.4783(3) ?; Z=4]. All the pyrophosphate anions show non-linear P–O–P bonds with an average angle of 128.60°. The framework of this new pyrophosphate is made up of packed layers of MnO6 octahedra connected by double-tetrahedra P2O7 groups and a layer of Mn(H2O)6 units. The [P2O7]4− anions adopt a bent, near-staggered conformation. The absence of coincidences for the majority of the IR and Raman bands is in accord with the centrosymmetric structure of the material. The vibrational spectra have been interpreted in part on the basis of factor group effects. The structural changes occurring during heating have been investigated by TG-ATD. When Mn4(P2O7)2
.10H2O is gradually heated, it decomposes into an intermediate hydrated salt at 96°C and then to anhydrous Mn2P2O7 at 325°C. This thermal behaviour is different from that of Zn4(P2O7)2·10H2O. The crystal structure of the new managenese(II) pyrophosphate is compared with the known structures of Zn4(P2O7)2·10H2O, Mn2P2O7·2H2O and anhydrous Mn2P2O7. The adsorption and desorption isotherms of Mn4(P2O7)2·10H2O, Zn4(P2O7)2·10H2O and MnKHP2O7·2H2O have been investigated by BET measurements and the results show that the capacity for N2 sorption of the Mn(II) salt is two times lower than is that of the Zn(II) isotype and two or three times higher than is that of MnKHP2O7·2H2O. 相似文献
24.
Dr. Samuel F. Haysom Jonathan Machin Dr. James M. Whitehouse Dr. Jim E. Horne Dr. Katherine Fenn Dr. Yue Ma Dr. Hassane El Mkami Dr. Nils Böhringer Prof. Dr. Till F. Schäberle Prof. Dr. Neil A. Ranson Prof. Dr. Sheena E. Radford Prof. Dr. Christos Pliotas 《Angewandte Chemie (International ed. in English)》2023,62(34):e202218783
The β-barrel assembly machinery (BAM complex) is essential for outer membrane protein (OMP) folding in Gram-negative bacteria, and represents a promising antimicrobial target. Several conformational states of BAM have been reported, but all have been obtained under conditions which lack the unique features and complexity of the outer membrane (OM). Here, we use Pulsed Electron-Electron Double Resonance (PELDOR, or DEER) spectroscopy distance measurements to interrogate the conformational ensemble of the BAM complex in E. coli cells. We show that BAM adopts a broad ensemble of conformations in the OM, while in the presence of the antibiotic darobactin B (DAR-B), BAM′s conformational equilibrium shifts to a restricted ensemble consistent with the lateral closed state. Our in-cell PELDOR findings are supported by new cryoEM structures of BAM in the presence and absence of DAR-B. This work demonstrates the utility of PELDOR to map conformational changes in BAM within its native cellular environment. 相似文献
25.
Sébastien Duminil Mohammed Heyouni Philippe Marion Hassane Sadok 《Numerical Algorithms》2016,71(2):383-394
The CMRH (Changing Minimal Residual method based on the Hessenberg process) method is a Krylov subspace method for solving large linear systems with non-symmetric coefficient matrices. CMRH generates a (non orthogonal) basis of the Krylov subspace through the Hessenberg process, and minimizes a quasi-residual norm. On dense matrices, the CMRH method is less expensive and requires less storage than other Krylov methods. In this work, we describe Matlab codes for the best of these implementations. Fortran codes for sequential and parallel implementations are also presented. 相似文献
26.
Kay CW El Mkami H Molla G Pollegioni L Ramsay RR 《Journal of the American Chemical Society》2007,129(51):16091-16097
It was recently suggested that partially reduced monoamine oxidase (MAO) A contains an equilibrium mixture of an anionic flavin radical and a tyrosyl radical (Rigby, S. E.; et al. J. Biol. Chem. 2005, 280, 4627-4632). These observations formed the basis for a revised radical mechanism for MAO. In contrast, an earlier study of MAO B only found evidence for an anionic flavin radical (DeRose, V. J.; et al. Biochemistry 1996, 35, 11085-11091). To resolve the discrepancy, we have performed continuous-wave electron paramagnetic resonance at 94 GHz (W-band) on the radical form of MAO A. A comparison with d-amino acid oxidase (DAAO) demonstrates that both enzymes only contain anionic flavin radicals. Pulsed electron-nuclear double resonance spectra of the two enzymes recorded at 9 GHz (X-band) reveal distinct hyperfine coupling patterns for the two flavins. Density functional theory calculations show that these differences can be understood in terms of the difference at C8alpha of the isoalloxazine ring. DAAO contains a noncovalently bound flavin whereas MAO A contains a flavin covalently bound to a cysteinyl residue at C8alpha. The similar electronic structures and hydrophobic environments of MAO and DAAO, and the similar structural motifs of their substrates suggest that a direct hydride transfer catalytic mechanism established for DAAO (Umhau, S.; et al. Proc. Natl. Acad. Sci. U.S.A. 2000, 97, 12463-12468) should be considered for MAO. 相似文献
27.
28.
Hala Samaha Nathalie Chahine Anatoly Petrovich Sobolev Luigi Menghini Hassane Makhlouf 《Molecules (Basel, Switzerland)》2021,26(16)
Despite the beneficial health properties shown by Lebanese saffron, its qualitative and quantitative composition has never been investigated before. In the present study, NMR spectroscopy, together with antioxidant activity assays, were applied to evaluate the chemical composition of saffron samples of different geographical origins (Lebanon, Italy, Iran, and India) and to categorize the Lebanese saffron for the first time. The distinction between Lebanese saffron and that produced in other countries was attributed to its higher linolenic and linoleic fatty acids, glucose and picrocrocin contents. Moreover, spices produced in three different regions of the Lebanese territory have been clearly differentiated. Saffron cultivated in the Qaa region displayed a high glucose, fatty acids and polyphenols content, whereas Hermel saffron exhibited the largest rate of picrocrocin and glycosylated carotenoids. Finally, samples from Baalbeck showed lower rates for the majority of metabolites. Moreover, Lebanese saffron showed a high antioxidant activity in ABTS and DPPH assays. A low dose of saffron extract (10 µg/mL) inhibited the growth of human lung adenocarcinoma cells, probably due to the high polyphenolic content. This study highlights the quality and peculiarity of Lebanese saffron cultivated in Northern Beqaa district and allows for a good discrimination between spices produced in relatively close territory. 相似文献
29.
M. Rabah D. Rached R. Khenata N. Moulay A. Zenati 《Solid State Communications》2009,149(23-24):941-945
We report local density functional calculations using the full potential linear muffin-tin orbital (FP-LMTO) method for binary platinum nitride (PtN), in five different crystal structures, the rock salt (B1), zinc-blende (B3), wurtzite (B4), nickel arsenide (B8), and PbS (B10) phases. The ground state properties such as the equilibrium lattice constant, elastic constants, the bulk modulus and its pressure derivative of PtN in these phases are determined and compared with the other available experimental and theoretical works.Our calculations confirm in the B3 structure that PtN is found to be mechanically stable with a large bulk modulus B=232.45 GPa and at a sufficiently high pressure the B81 structure would be favoured.The theoretical transition pressure from zinc blende (B3) to NiAs (B81), zinc-blende (B3) to rock-salt (B1) and zinc-blende (B3) to PbO (B10) is determined to be 9.10 GPa, 9.85 GPa and 69.35 GPa, respectively. Our calculation shows also in five different structures for PtN a high bulk modulus is a good indicator of a hard material. 相似文献
30.
Range restricted iterative methods based on the Arnoldi process are attractive for the solution of large nonsymmetric linear
discrete ill-posed problems with error-contaminated data (right-hand side). Several derivations of this type of iterative
methods are compared in Neuman et al. (Linear Algebra Appl. in press). We describe MATLAB codes for the best of these implementations.
MATLAB codes for range restricted iterative methods for symmetric linear discrete ill-posed problems are also presented. 相似文献