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941.
Luciana Marçal Ravaglia Deisy dos Santos Freitas Thiago Gomes Ricci Carlos Eduardo Domingues Nazario Glaucia Braz Alcantara 《Magnetic resonance in chemistry : MRC》2020,58(2):186-190
High sodium dietary intake has a positive association with an increase in blood pressure and can be correlated with risk factors of disease. Considering that the World Health Organization recommends a sodium intake lower than 2 g day-1 for adults, the hidden sodium content in processed foods is an important factor that compromises the assessment of a healthy diet. Accordingly, the present paper aimed to quantitate the sodium content of conventional soft drinks and their diet versions using nuclear magnetic resonance spectroscopy as a quantitative analytical technique (23Na qNMR). The results show one free sodium signal (Na+) displayed as a singlet at 0 ppm in the 23Na NMR spectrum, making its quantitation highly specific. This signal alone was used to directly determine the concentration of sodium in soft drinks. Flame photometry analysis was used to validate the method, and an excellent linearity was found in qNMR analysis (r = 0.9994) in comparison with flame photometry (r = 0.9958). In addition, a good correlation was found between sodium concentrations obtained by 23Na NMR and flame photometry in the evaluated commercial soft drinks. Since the intensity of the resonance line is directly proportional to the number of nuclei (spins), the concentration of sodium in soft drinks can be determined via this straightforward method without the need for external calibration. The experimental acquisitions are fast (approximately 15 min), allowing the analysis of several samples in a short period of time. This is a novel alternative for sodium quantitation using an efficient NMR methodology. 相似文献
942.
Luiz H. K. Queiroz Jr. Patrick Giraudeau Fabiane A. B. dos Santos Kleber T. de Oliveira Antonio G. Ferreira 《Magnetic resonance in chemistry : MRC》2012,50(7):496-501
Ultrafast (UF) 2D NMR makes it possible to obtain a 2D NMR spectrum in less than a second. Here, UF‐HSQC experiments are used for the real‐time mechanistic study of an acetal hydrolysis at ¹³C natural abundance, and it is possible to characterize the presence of the hemiacetal, an intermediate with a well‐known short lifetime. The assignments are confirmed and rationalized by quantum calculations of ¹H and ¹³C NMR chemical shifts and natural bonding orbital analysis. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
943.
Jéssica Maria de Souza Bruno Rodrigues Fazolo Jhully Wellen Ferreira Lacerda Mariana de Souza Moura Arielly Celestino Rodrigues dos Santos Leonardo Gomes de Vasconcelos Paulo Teixeira de Sousa Junior Evandro Luiz Dall’Oglio Akbar Ali Olívia Moreira Sampaio Lucas Campos Curcino Vieira 《Photochemistry and photobiology》2020,96(6):1233-1242
We report the synthesis of twelve indole derivatives bearing nitro or amide groups via Fischer indole methodology followed by reduction/acetylation and amidation reactions. After thorough characterization, these indoles were subjected to a number of studies in order to evaluate their bioactive potential as photosynthesis and plant growth inhibitors. Firstly, these molecular hybrids were evaluated as photosystem II (PSII) inhibitors through chlorophyll a (Chl a) fluorescence measurement. In this study, 6-chloro-8-nitro-2,3,4,9-tetrahydro-1H-carbazole ( 15a ) and 5-chloro-2,3-dimethyl-7-nitro-1H-indole ( 15b ) showed the best results by reducing the phenomenological parameters of reaction centers ABS/RC, TR0/RC and ET0/RC of PSII. Electron chain blockage by these compounds may lead to diminished ATP synthesis and CO2 fixation which interrupt the plant development. The compounds 15a and 15b both act as postemergent herbicides, reducing the dry biomass of Ipomoea grandifolia and Senna alata weeds by an average of 40% and 37%, respectively, corroborating the fluorescence results. Additionally, the molecular docking study revealed that the presence of strong electron-withdrawing groups at the indole phenyl ring is important for the ligand’s interaction with the binding pocket of protein D1 on PSII. The optimization of these molecular features is the goal of our research group in further understanding and development of new potent herbicides. 相似文献
944.
Laura Nunes dos Santos Comprido Dr. Johannes E. M. N. Klein Prof. Dr. Gerald Knizia Prof. Dr. Johannes Kästner Prof. Dr. A. Stephen K. Hashmi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):2892-2895
We herein report a computational study of the bonding in gold(I) vinylidene complexes and compare them to their carbene and CO analogues. The relevance of these intermediates is analysed for the intramolecular cyclisation leading to vinyl sulfonates. 相似文献
945.
Rui C. Santos Tânia S. Almeida Filipe Agapito Rui M. Borges dos Santos José A. Martinho Simões 《Structural chemistry》2013,24(6):2017-2026
A revised parameterization of the extended Laidler bond additivity method and quantum chemistry calculations were independently used to assess the standard molar enthalpies of formation of 20 non-polycyclic hydrocarbons in the gas phase. The detected discrepancies between predicted and experimental values are discussed, illustrating how this methodology can be useful in curing thermochemical data. 相似文献
946.
Heloisa A. Guimarães Ivo J. C. Vieira Raimundo Braz‐Filho Antônio E. M. Crotti Vitor S. dos Almeida Renata C. de Paula 《Helvetica chimica acta》2013,96(9):1793-1800
Two novel indole alkaloids with plumeran skeleton, N‐benzoyl‐12‐demethoxycylindrocarine and N‐cinnamoyl‐12‐demethoxycylindrocarine ( 1 and 2 , resp.), were isolated from the MeOH extract of the stem bark of Aspidosperma cylindrocarpon Müll .Arg . These compounds were obtained by high‐speed counter‐current chromatography, and their structures were elucidated on the basis of their NMR (1D and 2D) data. They were tested in vitro against chloroquine‐resistant strains of Plasmodium falciparum, and only 2 showed a weak activity (IC50 127.97 ng/ml with respect to the standard drug). Several other known compounds, comprising steroids, flavonoids, the rarely found atraric acid, as well as the previously reported alkaloid 3 , were also isolated by conventional chromatographic techniques. 相似文献
947.
948.
André Luiz dos Santos Elisete A. Batista Luís Moreira Gonçalves 《International journal of environmental analytical chemistry》2017,97(2):159-167
An electrochemical sensor for the determination of 3,5,6-trichloro-2-pyridinol (TCP), the main metabolite of the pesticide chlorpyrifos, was herein developed. TCP has greater solubility than the source pesticide, and its occurrence in ground and surface water is more frequent and more dangerous. The sensor was fabricated using carbon paste modified with the inorganic complex chloro-5,10,15,20-tetrakis-(pentafluorophenyl)-21 H,23 H-porphyrin iron(III) (FeTPPCl); this metallic complex has a chemical core structure similar to the heme cofactor of the cytochrome P450 (CYPs). Measurements were performed with square-wave voltammetry. Using the optimised voltammetric parameters and without any sample preparation, the sensor showed a limit of detection of 2.8 mg L?1 (14 μmol L?1), recoveries ca. 102%, suitable selectivity and long durability (over 1 month). 相似文献
949.
Henrique F. de Lima Antonio F. de Sousa Fábio R. dos Santos Marco Antonio L. Velásquez 《Mediterranean Journal of Mathematics》2016,13(6):3907-3919
In this paper, our aim is to establish optimal upper estimates for the first positive eigenvalue of a Jacobi type operator, which is a suitable extension of the linearized operators of the higher order mean curvatures of a closed hypersurface immersed either in spherical or in hyperbolical spaces. 相似文献
950.
Electrospray ionization tandem mass spectrometry analysis of isopimarane diterpenes from Velloziaceae 下载免费PDF全文