全文获取类型
收费全文 | 195篇 |
免费 | 11篇 |
专业分类
化学 | 148篇 |
晶体学 | 4篇 |
力学 | 1篇 |
数学 | 37篇 |
物理学 | 11篇 |
无线电 | 5篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 9篇 |
2012年 | 17篇 |
2011年 | 16篇 |
2010年 | 11篇 |
2009年 | 8篇 |
2008年 | 12篇 |
2007年 | 14篇 |
2006年 | 14篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有206条查询结果,搜索用时 46 毫秒
131.
Two decapeptide fragments of the non-structural hepatitis G NS3 protein (GBV-C/HGV), 513-522 (RGRTGRGRSG) and 505-514 (SAELSMQRRG), as well as their palmitoylated derivatives were synthesized. The physico-chemical properties of the peptides were analyzed in both the absence and presence of the zwitterionic 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), the negative 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DPPG) and the positive 1,2-dioeloyl-3-trimethylammonium-propane (DOTAP) lipid monolayers. Based on their high hydrophilic properties, neither parent peptide presented surface activity and their incorporation into lipid monolayers was low. In contrast, their palmitoylated derivatives showed concentration-dependent surface activity and could be inserted into lipid monolayers to varying degrees depending on their sequence. Compression isotherms showed that the presence of palmitoylated peptides in the subphase resulted in a molecular arrangement less condensed than that corresponding to the pure phospholipid. In concordance with the monolayer results, differential scanning calorimetry (DSC) demonstrated that the parent peptides did not have any effect on the thermograms, while the palmitoylated derivatives affected the thermotropic properties of DPPC bilayers. 相似文献
132.
Sergio Muñoz Josefina Pons Josep Ros Malcolm A. Halcrow 《Journal of organometallic chemistry》2011,696(14):2736-2741
The reactivity of (3,5-dimethyl-1H-pyrazol-1-yl)ethyldiphenylphosphine (L) hybrid ligand against Cu(I), Ag(I) and Au(I) has been assayed and compounds [Cu(L)2](PF6) (1), [Ag(L)]2(PF6)2·2C2H4Cl2·2C4H10O (2) and [AuCl(L)]2 (3) have been isolated and fully characterised. A fully characterisation by analytical and spectroscopic methods of 1-3 are presented and X-ray crystal structures of 1 and 2 are also reported. The similar data obtained between 2 and 3 permits to do a serious purpose of the structure of 3 in solid and solution. 相似文献
133.
134.
Francisco Snchez-Frez Joaquim Mª Rius-Bartra Jos A. Aylln Teresa Calvet Merc Font-Bardia Josefina Pons 《Molecules (Basel, Switzerland)》2022,27(4)
Aggregation between discrete molecules is an essential factor to prevent aggregation-caused quenching (ACQ). Indeed, functional groups capable of generating strong hydrogen bonds are likely to assemble and cause ACQ and photoinduced electron transfer processes. Thus, it is possible to compare absorption and emission properties by incorporating two ligands with a different bias toward intra- and intermolecular interactions that can induce a specific structural arrangement. In parallel, the π electron-donor or electron-withdrawing character of the functional groups could modify the Highest Ocuppied Molecular Orbital (HOMO)–Lowest Unocuppied Molecular Orbital (LUMO) energy gap. Reactions of M(OAc)2·2H2O (M = Zn(II) and Cd(II); OAc = acetate) with 1,3-benzodioxole-5-carboxylic acid (Piperonylic acid, HPip) and 4-acetylpyridine (4-Acpy) or isonicotinamide (Isn) resulted in the formation of four complexes. The elucidation of their crystal structure showed the formation of one paddle-wheel [Zn(μ-Pip)2(4-Acpy)]2 (1); a mixture of one dimer and two monomers [Zn(µ-Pip)(Pip)(Isn)2]2·2[Zn(Pip)2(HPip)(Isn)]·2MeOH (2); and two dimers [Cd(μ-Pip)(Pip)(4-Acpy)2]2 (3) and [Cd(μ-Pip)(Pip)(Isn)2]2·MeOH (4). They exhibit bridged (1, µ2-η1:η1), bridged, chelated and monodentated (2, µ2-η1:η1, µ1-η1:η1 and µ1-η1), or simultaneously bridged and chelated (3 and 4, µ2-η2:η1) coordination modes. Zn(II) centers accommodate coordination numbers 5 and 6, whereas Cd(II) presents coordination number 7. We have related their photophysical properties and fluorescence quantum yields with their geometric variations and interactions supported by TD-DFT calculations. 相似文献
135.
Laura Aracely Contreras-Angulo Aldo Moreno-Ulloa Rommel A. Carballo-Castaeda Josefina Len-Felix Jos Geovanni Romero-Quintana Maribel Aguilar-Medina Rosalío Ramos-Payn J. Basilio Heredia 《Molecules (Basel, Switzerland)》2022,27(20)
The eggplant is a fruit rich in natural products and produced worldwide. However, its cultivation generates a large amount of scarcely used agricultural residues with poor chemical characterization. This study aimed to identify and quantify the metabolome and determine the composition of select phytochemicals and the overall antioxidant capacity of various anatomical parts of the plant. The plant’s root, leaf, stem, and fruit were analyzed by quantitative mass spectrometry-based untargeted metabolomics and chemoinformatics, and phytochemicals were quantified by spectrophotometric analysis. Moreover, we determined the total antioxidant capacity of the distinct plant parts to infer a possible biological effect of the plant’s metabolites. Various secondary metabolites were identified as terpenes, phenolic compounds, alkaloids, and saponins, distributed throughout the plant. The leaf and fruit presented the highest concentration of phenolic compounds, flavonoids, anthocyanins, and alkaloids, accompanied by the highest antioxidant capacity. Although the stem and root showed the lowest abundance of secondary metabolites, they provided around 20% of such compounds compared with the leaf and fruit. Overall, our study improved the understanding of the eggplant metabolome and concluded that the plant is rich in secondary metabolites, some with antioxidant properties, and shows potential nutraceutical and biopharmaceutical applications. 相似文献
136.
Sáez-Muñoz Marina Bagán Héctor Tarancón Alex García José F. Ortiz Josefina Carlos Sofía Martorell Sebastián 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(3):1397-1408
Journal of Radioanalytical and Nuclear Chemistry - This study describes a rapid and novelty method for radiostrontium determination in aerosol filters and vegetation based on the use of plastic... 相似文献
137.
Roselló-Merino M Díez J Conejero S 《Chemical communications (Cambridge, England)》2010,46(48):9247-9249
Pyridinium 2-carboxylates decompose thermally in the presence of a variety of late transition metal precursors to yield the corresponding 2-pyridylidene-like complexes. The mild reaction conditions and structural diversity that can be generated in the heterocyclic ring make this method an attractive alternative for the synthesis of 2-pyridylidene complexes. IR spectra of the Ir(i) carbonyl compounds [IrCl(NHC)(CO)(2)] indicate that these N-heterocyclic carbene ligands are among the strongest σ-electron donors. 相似文献
138.
M.?C.?ArenasEmail author Gabriela?Sánchez M.?E.?Nicho Josefina?Elizalde-Torres V.?M.?Casta?o 《Applied Physics A: Materials Science & Processing》2012,106(4):901-908
Conducting Polyaniline films (Pani) on Corning glass substrates, produced using either an in-situ doping process or a co-doping
process, were prepared by the oxidative polymerization of aniline in N,N,dimethylformamide. Bicyclic aliphatic camphorsulfonic
acid (CSA), aromatic toluenesulfonic acid (TSA) and carboxylic trifluoroacetic acid (TFA) were employed as doping agents,
and CSA mixed with TSA and CSA mixed with TFA were employed as the co-doping materials. The topography of the Pani films was
analyzed by atomic-force microscopy (AFM), and their doping and oxidizing states were characterized by Fourier-transform infrared
(FT-IR) spectroscopy and optical (UV-Vis) spectroscopy. Flower-like clusters, microfibers, and nanofibers were obtained by
doping with CSA, TSA, and the mix of both (CSATSA), respectively. The flower-like morphology limits the conductivity of the
film while the microfiber morphology leads to a highly conductive film. The conductivity of the films increases with the doping
level, coil-like conformation of the chain and the protonation of the imine in quinoid units. The codoped process reduces
the roughness of the CSA-doped films by 50%, but the conductivity depends on the acid type used for this process (TSA or TFA).
The optical gas sensor response of the films is related to both the morphology and the degree of protonation. In this study,
Pani with a microfiber morphology obtained from TSA-doping is the most sensitive to ammonia gas sensing, and Pani with flower-like
morphology is the least sensitive. 相似文献
139.
140.