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51.
Luana Bettanin Sumbal Saba Carlos V. Doerner Marcelo S. Franco Marcelo Godoi Jamal Rafique Antonio L. Braga 《Tetrahedron》2018,74(29):3971-3980
Herein, we described the NH4I-catalyzed CH bond chalcogenation of N-heteroaryls in the presence of a minimum amount of DMSO/H2O/acetic acid as additives (2.5/2.5/1?M equiv., respectively), under metal-free conditions. Under optimized conditions, a wide variety of sulfenyl/selenyl imidazo[1,2-α]pyridines were prepared in very good yields. Moreover, the present approach was also highly efficient for the chalcogenation of different 5-membered N-heteroaryls, e.g., indole, imidazothiazole, indazole and imidazopyrimidine derivatives. 相似文献
52.
G. Gervasio R. Rossetti P. L. Stanghellini D. Braga S. F. A. Kettle 《Journal of chemical crystallography》1993,23(4):255-264
The crystal structure of Co4(CO)10S2 has been redetermined and that of Co4(CO)10Se2 obtained by X-ray analysis. The compounds are monoclinic and isomorphous, space groupP21/n,Z=2, with (S compound)a=10.42(2)Å,b=6.794(1)Å,c=12.421(2)Å,=97.27(1) and (Se compound)a=10.110(2)Å,b=6.747(2)Å,c=12.592(4)Å,=96.37(2); finalR(S)=0.029,R
w
=0.032 for 1414 reflections and finalR (Se)=0.052,R
w
=0.054 for 1264 reflections. The molecules, which lie on a crystallographic center of symmetry, consist of a rectangle with Co atoms at the corners, each face of the rectangle being capped by a chalcogen atom. Each Co atom is bonded to two terminal CO groups; there are two bridging CO groups, one on each member of a pair of opposite sides of the rectangle. The vibrational spectra of the sulfur compound are considered in detail. A study of the crystal structure, and recognition of an approximate spectroscopic space group, are shown to be essential for an understanding of thev(CO) infrared spectrum of polycrystalline Co4(CO)10S2. In this molecule, intramolecular vibrational coupling in the crystal leads to extensive modifications of the infrared-activev(CO) molecular coordinates. 相似文献
53.
?eljko Petrovski Susana S. Braga Márcia L. Matos Martyn Pillinger Carlos C. Romão 《Journal of organometallic chemistry》2008,693(4):675-684
Seven different ferrocene derivatives have been tested in vitro against Ehrlich ascites tumor cells. Neither ferrocene nor the monosubstituted derivative N,N-dimethylaminomethylferrocene showed cytotoxic activity (IC50 > 1000 μM for 3 h treatments). Better results were obtained with 1,2-disubstituted derivatives. The IC50 values ranged from 376.6 μM for 1,2-diformylferrocene to 71.2 μM for racemic 2-(N,N-dimethylaminomethyl)ferrocenecarboxamide. The latter derivative was also encapsulated in native β-cyclodextrin (CD), heptakis-2,3,6-tri-O-methyl-β-CD (TRIMEB) and 2-hydroxypropyl-β-CD (HPβCD) to give 1:1 (host:guest) inclusion compounds. The existence of true inclusion complexes in the solid state was confirmed by a combination of powder X-ray diffraction, thermogravimetric analysis, FTIR and 13C CP MAS NMR spectroscopy. The IC50 value for the β-CD inclusion compound was identical to that obtained for the nonincluded ferrocene derivative. By contrast, the inclusion compounds comprising TRIMEB and HPβCD yielded IC50 values of 25.2 and 20.0 μM, respectively. No obvious relationship could be established between the redox behavior of the compounds determined by cyclic voltammetry and the biochemical data. 相似文献
54.
Caetano P. Sabino Martha S. Ribeiro Mark Wainwright Carolina dos Anjos Fábio P. Sellera Milena Dropa Nathalia B. Nunes Guilherme T. P. Brancini Gilberto U. L. Braga Victor E. Arana-Chavez Raul O. Freitas Nilton Lincopan Maurício S. Baptista 《Photochemistry and photobiology》2023,99(2):742-750
The unbridled dissemination of multidrug-resistant pathogens is a major threat to global health and urgently demands novel therapeutic alternatives. Antimicrobial photodynamic therapy (aPDT) has been developed as a promising approach to treat localized infections regardless of drug resistance profile or taxonomy. Even though this technique has been known for more than a century, discussions and speculations regarding the biochemical mechanisms of microbial inactivation have never reached a consensus on what is the primary cause of cell death. Since photochemically generated oxidants promote ubiquitous reactions with various biomolecules, researchers simply assumed that all cellular structures are equally damaged. In this study, biochemical, molecular, biological and advanced microscopy techniques were employed to investigate whether protein, membrane or DNA damage correlates better with dose-dependent microbial inactivation kinetics. We showed that although mild membrane permeabilization and late DNA damage occur, no correlation with inactivation kinetics was found. On the other hand, protein degradation was analyzed by three different methods and showed a dose-dependent trend that matches microbial inactivation kinetics. Our results provide a deeper mechanistic understanding of aPDT that can guide the scientific community toward the development of optimized photosensitizing drugs and also rationally propose synergistic combinations with antimicrobial chemotherapy. 相似文献
55.
Lucena JR Sharma A Reva ID Araújo RM Ventura E do Monte SA Braga CF Ramos MN Fausto R 《The journal of physical chemistry. A》2008,112(46):11641-11648
The molecular structure and infrared spectrum of the atmospheric pollutant 3,3-dichloro-1,1,1-trifluoropropane (HCFC-243) were characterized experimentally and theoretically. The theoretical calculations show the existence of two conformers, with the gauche (G) and trans (T) orientation around the HCCC dihedral angle. Conformer G was calculated to be more stable than form T by more than 10 kJ mol (-1). In consonance with the large predicted relative energy of conformer T, only the G form was identified spectroscopically in cryogenic argon (10 K) and xenon (20 K) matrices prepared from room-temperature equilibrium vapor of the compound. The observed infrared spectra of the matrix-isolated HCFC-243 were interpreted with the aid of high-level density functional theory calculations and normal coordinate analysis. For experimental identification of the weakest IR absorption bands, the spectrum of HCFC-243 in the neat solid state at 145 K was obtained. This spectrum also confirmed the sole presence of the G conformer in the sample. Natural bond orbital and atomic charge analyses were carried out for the two conformers to shed light on the most important intramolecular interactions in the two conformers, in particular those responsible for their relative stability. 相似文献
56.
Braga D Palladino G Polito M Rubini K Grepioni F Chierotti MR Gobetto R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(32):10149-10159
Three crystal forms of the co-crystal 4,4'-bipy/pimelic acid (bipy: bipyridine), [NH(4)C(5)-C(5)H(4)N][HOOC(CH(2))(5)COOH], have been prepared and their relationship investigated by single-crystal X-ray diffraction, variable-temperature X-ray powder diffraction, differential scanning calorimetry and solid-state NMR spectroscopy. Both X-ray and NMR spectroscopic results indicate that no proton transfer takes place, that is, the three crystal forms are true co-crystals of neutral molecules. Forms I and II both convert into Form III at high temperature, Forms II and III being the thermodynamically stable forms at room and high temperature, respectively. 相似文献
57.
58.
Regioselective,Solvent‐ and Metal‐Free Chalcogenation of Imidazo[1,2‐a]pyridines by Employing I2/DMSO as the Catalytic Oxidation System 下载免费PDF全文
Dr. Jamal Rafique Dr. Sumbal Saba Dr. Alisson R. Rosário Prof. Dr. Antonio L. Braga 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11854-11862
Highly efficient molecular‐iodine‐catalyzed chalcogenations (S and Se) of imidazo[1,2‐a]pyridines were achieved by using diorganoyl dichalcogenides under solvent‐free conditions. This approach afforded the desired products that had been chalcogenated regioselectively at the C3 position in up to 96 % yield by using DMSO as an oxidant, in the absence of a metal catalyst, and under an inert atmosphere. This mild, green approach allowed the preparation of different types of chalcogenated imidazo[1,2‐a]pyridines with structural diversity. Furthermore, the current protocol was also extended to other N‐heterocyclic cores. 相似文献
59.
Josiney A. Souza Carlos J. Braga Barros Victor H. L. Rocha 《Mathematische Nachrichten》2016,289(10):1272-1287
The present paper is dedicated to the study of various aspects of attraction and stability for semigroup actions on topological spaces. The main purpose is to present the connections among the distinct notions of attractors and stable sets. The concept of Conley attractor is also investigated and related to the other notions of attractors. All the results are applied to the theory of control systems. 相似文献
60.
Braga D Maini L Fagnano C Taddei P Chierotti MR Gobetto R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(4):1222-1230
The structural relationship between the two crystal forms of cinchomeronic acid (CA 3,4-dicarboxypyridine) has been investigated by single crystal X-ray diffraction, IR and Raman spectroscopy and solid state NMR spectroscopy, showing that the two polymorphs form a monotropic system, with the orthorhombic form I being the thermodynamically stable form, while the monoclinic form II is unstable. In both forms CA crystallizes as a zwitterion and decomposes before melting. The crystal structure and spectroscopic analysis indicate that the difference in stability can be ascribed to the strength of the hydrogen-bonding patterns established by the protonated N-atom and the carboxylic/carboxylate O-atoms. 相似文献