全文获取类型
收费全文 | 333篇 |
免费 | 29篇 |
专业分类
化学 | 326篇 |
晶体学 | 1篇 |
数学 | 11篇 |
物理学 | 24篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 44篇 |
2020年 | 19篇 |
2019年 | 22篇 |
2018年 | 12篇 |
2017年 | 17篇 |
2016年 | 22篇 |
2015年 | 22篇 |
2014年 | 21篇 |
2013年 | 27篇 |
2012年 | 25篇 |
2011年 | 23篇 |
2010年 | 13篇 |
2009年 | 16篇 |
2008年 | 24篇 |
2007年 | 13篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 1篇 |
2002年 | 1篇 |
1998年 | 1篇 |
1989年 | 1篇 |
1976年 | 1篇 |
1932年 | 1篇 |
排序方式: 共有362条查询结果,搜索用时 31 毫秒
1.
Influence of ZnO,SiO2 and TiO2 on the aging process of PLA fibers produced by electrospinning method
Kosowska Karolina Szatkowski Piotr 《Journal of Thermal Analysis and Calorimetry》2020,140(4):1769-1778
Journal of Thermal Analysis and Calorimetry - The aim of this work was to study the effect of ceramics particles addition (SiO2, ZnO, TiO2) on the ultraviolet (UV) aging of poly(lactic acid)... 相似文献
2.
Renny Mathew Karolina A. Uchman Lydia Gkoura Chris J. Pickard Maria Baias 《Magnetic resonance in chemistry : MRC》2020,58(11):1018-1025
A combined experimental and computational approach was used to distinguish between different polymorphs of the pharmaceutical drug aspirin. This method involves the use of ab initio random structure searching (AIRSS), a density functional theory (DFT)-based crystal structure prediction method for the high-accuracy prediction of polymorphic structures, with DFT calculations of nuclear magnetic resonance (NMR) parameters and solid-state NMR experiments at natural abundance. AIRSS was used to predict the crystal structures of form-I and form-II of aspirin. The root-mean-square deviation between experimental and calculated 1H chemical shifts was used to identify form-I as the polymorph present in the experimental sample, the selection being successful despite the large similarities between the molecular environments in the crystals of the two polymorphs. 相似文献
3.
Karolina Kula Agnieszka Kcka-Zych Agnieszka apczuk-Krygier Zbigniew Wzorek Anna K. Nowak Radomir Jasiski 《Molecules (Basel, Switzerland)》2021,26(5)
The present paper is a continuation of comprehensive study regarding to synthesis and properties of pyrazoles and their derivatives. In its framework an experimental and theoretical studies of thermal decomposition of the 3,3-diphenyl-4-(trichloromethyl)-5-nitropyrazoline were performed. It was found, that the decompositions of the mentioned pyrazoline system in the solution and at the melted state proceed via completely different molecular mechanisms. These mechanisms have been explained in the framework of the Molecular Electron Density Theory (MEDT) with the computational level of B3LYP/6-31G(d). A Bonding Evolution Theory (BET) examination of dehydrochlorination of the 3,3-diphenyl-4-(trichloromethyl)-5-nitropyrazoline permits elucidation of the molecular mechanism. It was found, that on the contrary for most known HCl extrusion processes in solution, this reaction is realised via single-step mechanism. 相似文献
4.
Dr. Fredrik Schaufelberger Karolina Seigel Prof. Dr. Olof Ramström 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(67):15581-15588
The reversibility of imine bonds has been exploited to great effect in the field of dynamic covalent chemistry, with applications such as preparation of functional systems, dynamic materials, molecular machines, and covalent organic frameworks. However, acid catalysis is commonly needed for efficient equilibration of imine mixtures. Herein, it is demonstrated that hydrogen bond donors such as thioureas and squaramides can catalyze the equilibration of dynamic imine systems under unprecedentedly mild conditions. Catalysis occurs in a range of solvents and in the presence of many sensitive additives, showing moderate to good rate accelerations for both imine metathesis and transimination with amines, hydrazines, and hydroxylamines. Furthermore, the catalyst proved simple to immobilize, introducing both reusability and extended control of the equilibration process. 相似文献
5.
Leo Valenta Petr Kovaí
ek Vclav Vale Zdenk Bastl Karolina A. Drogowska Timotheus A. Verhagen Radek Cibulka Martin Kalb
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1338-1342
Spatially resolved functionalization of 2D materials is highly demanded but very challenging to achieve. The chemical patterning is typically tackled by preventing contact between the reagent and material, which brings various accompanying challenges. Photochemical transformation on the other hand inherently provides remote high spatiotemporal resolution using the cleanest reagent—a photon. Herein, we combine two competing reactions on a graphene substrate to create functionalization patterns on a micrometer scale via the Mitsunobu reaction. The mild reaction conditions allow introduction of covalently dynamic linkages, which can serve as reversible labels for surface‐ or graphene‐enhanced Raman spectroscopy characterization of the patterns prepared. The proposed methodology thus provides a pathway for local introduction of arbitrary functional groups on graphene. 相似文献
6.
Gusenbauer Claudia Peter Karolina Cabane Etienne Konnerth Johannes 《Cellulose (London, England)》2022,29(2):763-776
Cellulose - Chemical force microcopy, a variation of atomic force microscopy, opened the door to visualize chemical nano-properties of various materials in their natural state. The key function of... 相似文献
7.
8.
Marcin Kubisiak Karolina Zelga Wojciech Bury Iwona Justyniak Krzysztof Budny-Godlewski Zbigniew Ochal Janusz Lewiński 《Chemical science》2015,6(5):3102-3108
This paper reports a series of comparative experiments on the activity of carbon- and oxygen-centred radical species in a model reaction of the radical addition of THF to imines mediated by a series of zinc alkyl/air reaction systems. The study strongly contradicts the notion that generally R˙ radicals are the initiating species in organic reactions mediated by RnM/air systems, and simultaneously demonstrates that oxygen-centred radical species are the key intermediates responsible for the initiation process. In addition, a new efficient RZn(L)/air initiating system for radical organic reactions exampled by a model reaction of radical addition of THF to imines is developed. Moreover, the isolation and structural characterization of the first zinc alkylperoxide supported by a carboxylate ligand, [Zn4(μ3-OOtBu)3(μ4-O)(O2CEt)3]2, as well as the novel octanuclear zinc oxo(alkoxide) aggregate with entrapped O–THF species, [Zn4(μ4-O)(μ3-2-O–THF)(O2CEt)5]2, provide clear mechanistic signatures for the mode of function of the RZn(O2CR′)/air system. 相似文献
9.
Agata Górska Karolina Szulc Ewa Ostrowska-Ligęza Joanna Bryś Magdalena Wirkowska-Wojdyła 《Journal of Thermal Analysis and Calorimetry》2017,128(1):177-183
Epoxy-based nanocomposites containing different concentrations (0–3%) of surface-modified graphene nanosheets (GNS) with 3-aminopropyltriethoxysilane were prepared and their thermal and mechanical properties including dynamic mechanical analysis, tensile strength, hardness, and abrasion tests were evaluated in order to have a database for thermo-mechanical properties of epoxy nanocomposites. The main aim of this study was to understand the optimum percentage of GNS which would perform the best reinforcing influence on mechanical and physical performance of an epoxy nanocomposite. The results explain how applying the analysis of variance (ANOVA) method as a useful tool in optimization of GNS concentration in preparation of high-performance epoxy-based nanocomposites. 相似文献
10.
Dr. Julian Heinrich Dr. Karolina Bossak-Ahmad Mie Riisom Dr. Haleh H. Haeri Tasha R. Steel Vinja Hergl Alexander Langhans Corinna Schattschneider Jannis Barrera Dr. Stephen M. F. Jamieson Prof. Matthias Stein Prof. Dariush Hinderberger Prof. Christian G. Hartinger Prof. Wojciech Bal Prof. Nora Kulak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(72):18093-18102
Redox-active Cu(II) complexes are able to form reactive oxygen species (ROS) in the presence of oxygen and reducing agents. Recently, Faller et al. reported that ROS generation by Cu(II) ATCUN complexes is not as high as assumed for decades. High complex stability results in silencing of the Cu(II)/Cu(I) redox cycle and therefore leads to low ROS generation. In this work, we demonstrate that an exchange of the α-amino acid Gly with the β-amino acid β-Ala at position 2 (Gly2→β-Ala2) of the ATCUN motif reinstates ROS production (•OH and H2O2). Potentiometry, cyclic voltammetry, EPR spectroscopy and DFT simulations were utilized to explain the increased ROS generation of these β-Ala2-containing ATCUN complexes. We also observed enhanced oxidative cleavage activity towards plasmid DNA for β-Ala2 compared to the Gly2 complexes. Modifications with positively charged Lys residues increased the DNA affinity through electrostatic interactions as determined by UV/VIS, fluorescence, and CD spectroscopy, and consequently led to a further increase in nuclease activity. A similar trend was observed regarding the cytotoxic activity of the complexes against several human cancer cell lines where β-Ala2 peptide complexes had lower IC50 values compared to Gly2. The higher cytotoxicity could be attributed to an increased cellular uptake as determined by ICP-MS measurements. 相似文献