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排序方式: 共有400条查询结果,搜索用时 15 毫秒
391.
392.
Fonseca PR Dekker RF Barbosa AM Silveira JL Vasconcelos AF Monteiro NK Aranda-Selverio G da Silva Mde L 《Molecules (Basel, Switzerland)》2011,16(9):7488-7501
Differential scanning calorimetry (DSC), thermogravimetry (TG) and Fourier-transform infra-red spectroscopy (FT-IR) analyses were performed to investigate changes in the physico-chemical properties of botryosphaerans, a family of exopolysaccharides (EPS) produced by the fungus Botryosphaeria rhodina MAMB-05 grown on glucose (EPS(GLC)), sucrose (EPS(SUC)) and fructose (EPS(FRU)). A slight endothermic transition and small mass loss attributable to the removal of water of hydration were observed in the DSC and TG analyses, respectively, for the three EPS samples. The FT-IR spectra confirmed no structural changes occurred during thermal treatment. Viscometry was utilized to obtain information on the rheological behaviour of the EPS in aqueous solutions. The Power Law and Cross Equations determined the natural pseudoplastic characteristics of the EPS. Comparatively, results obtained for EPS produced when B. rhodina MAMB-05 was grown on each of the three carbohydrate sources demonstrated similar apparent viscosity values for EPS(GLC) and EPS(SUC), while EPS(FRU) displayed the lowest apparent viscosity of the three botryosphaerans, suggesting a higher degree of ramification and lower Mw. EPS(GLC) and EPS(SUC) possessed similar degrees of ramification. The slight differences found in their viscosities can be explained by the differences in the type of branching among the three botryosphaerans, thus varying the strength of intermolecular interactions and consequently, consistency and viscosity. The physico-chemical studies of botryosphaerans represent the originality of this work, and the knowledge of these properties is an important criterion for potential applications. 相似文献
393.
Araújo MG Hilário F Nogueira LG Vilegas W Santos LC Bauab TM 《Molecules (Basel, Switzerland)》2011,16(12):10479-10490
Chemical fractionation of the methanolic extract of leaves of Leiothrix spiralis Ruhland afforded the flavonoids luteolin-6-C-β-D-glucopyranoside (1), 7-methoxyluteolin-6-C-β-D-glucopyranoside (2), 7-methoxyluteolin-8-C-β-D-glucopyranoside (3), 4'-methoxyluteolin-6-C-β-D-glucopyranoside (4), and 6-hydroxy-7-methoxyluteolin (5), and the xanthones 8-carboxymethyl-1,5,6-trihydroxy-3-methoxyxanthone (6), 8-carboxy-methyl-1,3,5,6-tetrahydroxyxanthone (7). Methanolic extract, fractions, and isolated compounds of the leaves of L. spiralis were assayed against Gram-positive (Staphylococcus aureus, Bacillus subtilis and Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella setubal and Helicobacter pylori) and fungi (the yeasts Candida albicans, C. tropicalis, C. krusei and C. parapsilosis). We observed the best minimum inhibitory concentration values for the methanolic extract against Candida parapsilosis, for the fraction 5 + 6 against Gram-negative bacteria E. coli and P. aeruginosa, and compound 7 against all tested Candida strains. The methanolic extract contents suggest that this species may be a promising source of compounds to produce natural phytomedicines. 相似文献
394.
Builes S Roussel T Ghimbeu CM Parmentier J Gadiou R Vix-Guterl C Vega LF 《Physical chemistry chemical physics : PCCP》2011,13(35):16063-16070
In this study we attempt to investigate the potential use of two zeolite template carbon (ZTC), EMT-ZTC and FAU-ZTC, to capture CO(2) at room temperature. We report their high pressure CO(2) adsorption isotherms (273 K) that show for FAU-ZTC the highest carbon capture capacity among published carbonaceous materials and competitive data with the best organic and inorganic adsorbing frameworks ever-known (zeolites and mesoporous silicas, COFs and MOFs). The importance of these results is discussed in light of mitigation of CO(2) emissions. In addition to these new experimental CO(2) adsorption data, we also present new insight into the adsorption process of the two structures by Monte Carlo simulations: we propose that two separate effects are responsible for the apparent similarity of the adsorption behaviour of the two structures: (i) pore blocking occurring on EMT-ZTC, and (ii) the change of the carbon polarizability due to the extreme curvature of FAU-ZTC. 相似文献
395.
Sucunza D Samadi A Chioua M Silva DB Yunta C Infantes L Carmo Carreiras M Soriano E Marco-Contelles J 《Chemical communications (Cambridge, England)》2011,47(17):5043-5045
The Sandmeyer reaction of differently C-2 substituted N-(prop-2-yn-1-ylamino)pyridines is an efficient, mild, new and practical method for the stereospecific synthesis of (E)-exo-halomethylene bicyclic pyridones bearing the imidazo[1,2-a]pyridine heterocyclic ring system. 相似文献
396.
Jorge J. Betancor Juan C. Fariña Lourdes Rodríguez-Mesa Ricardo Testoni José L. Torrea 《数学学报(英文版)》2015,31(11):1759-1774
In this paper, we study fractional square functions associated with the Poisson semigroup for Schrdinger operators. We characterize the potential spaces in the Schrdinger setting by using vertical, area and g*λ fractional square functions. 相似文献
397.
Lourdes Jachero Betsabet Sepúlveda Inés Ahumada Edwar Fuentes Pablo Richter 《Analytical and bioanalytical chemistry》2013,405(24):7711-7716
A method of sample preparation based on use of rotating disk sorptive extraction (RDSE) has been developed for determination of triclosan (TCS) and methyl-triclosan (MTCS) in water samples. The sorptive and desorptive behavior of the analytes was studied by use of a rotating disk coated with polydimethylsiloxane (PDMS) on one of its surfaces. Chemical and extraction behavior were studied to establish the best conditions for extraction. The optimum conditions for both analytes were: sample volume 25 mL, pH?4.5, NaCl concentration 6 % (w/v), disk rotational velocity 1,250 rpm, and extraction time 80 min. A desorption time of 30 min was used with 5 mL methanol. The detection limits for TCS and MTCS were 46 and 34 ng?L?1, respectively. Recovery was evaluated at two concentrations, 160 and 800 ng?L?1, and the values obtained were between 80 and 100 %. The method was applied to analysis of influent water at two treatment plants in Santiago, Chile. 相似文献
398.
Raisul Awal Mahmood Anamul Hasan Mohammed Rahmatullah Alok K. Paul Rownak Jahan Khoshnur Jannat Tohmina Afroze Bondhon Tooba Mahboob Veeranoot Nissapatorn Maria de Lourdes Pereira Tridib K. Paul Ommay Hany Rumi Christophe Wiart Polrat Wilairatana 《Molecules (Basel, Switzerland)》2022,27(15)
COVID-19, caused by the coronavirus SARS-CoV-2, emerged in late December 2019 in Wuhan, China. As of 8 April 2022, the virus has caused a global pandemic, resulting in 494,587,638 infections leading to 6,170,283 deaths around the world. Although several vaccines have received emergency authorization from USA and UK drug authorities and two more in Russia and China, it is too early to comment on the prolonged effectiveness of the vaccines, their availability, and affordability for the developing countries of the world, and the daunting task to vaccinate 7 billion people of the world with two doses of the vaccine with additional booster doses. As a result, it is still worthwhile to search for drugs and several promising leads have been found, mainly through in silico studies. In this study, we have examined the binding energies of several alkaloids and anthocyanin derivatives from the Solanaceae family, a family which contains common consumable vegetables and fruit items such as eggplant, pepper, and tomatoes. Our study demonstrates that Solanaceae family alkaloids such as incanumine and solaradixine, as well as anthocyanins and anthocyanidins, have very high predicted binding energies for the 3C-like protease of SARS-CoV-2 (also known as Mpro). Since Mpro is vital for SARS-CoV-2 replication, the compounds merit potential for further antiviral research towards the objective of obtaining affordable drugs. 相似文献
399.
Teresa Mancilla Dolores Castillo Lourdes Carrillo Norberto Farfn 《Heteroatom Chemistry》1999,10(2):133-139
The reaction of N‐methyl‐2,2′‐diphenolamine 1 and 2,2′‐diphenolamine 2 with some diorganotin(IV) oxides [R1/2SnO: R1 = Me, n‐Bu, t‐Bu and Ph] led to the syntheses of diorgano[N‐methyl‐2,2′‐diphenolato‐O,O′,N]tin (IV) 3–6 and diorgano[2,2′‐diphenolato‐O,O′,N]tin (IV) 7–9 . All compounds (except 7 ) studied in this work were characterized by 1H, 13C, 119Sn NMR, infrared, and mass spectroscopy. Their 119Sn NMR data show that the tin atom is tetracoordinated in CDCl3 but penta and hexacoordinated in DMSO‐d6. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 133–139, 1999 相似文献
400.
Teresa Mancilla Ma. De Jesus Rosales Efren V. García-Baez Lourdes Carrillo 《Heteroatom Chemistry》1995,6(6):605-609
The reactions of methyl glyoxylate hemiacetal 1 with 2-(methylamino)ethanol 2 , (1R,2S)-(–)-ephedrine 3 and (1S,2S)-(+)-pseudoephedrine 4 provide the (2S)-2-hydroxy-1,4-oxazin-3-ones 2a , 3a , 4a in good yield. They were characterized by 1H, 13C, NMR, and infrared and mass spectroscopy. The structures of 2a and 3a were established by X-ray diffraction. The configuration of C2 (S) is demonstrated by 1H NMR data and confirmed for compounds 2a and 3a by single-crystal X-ray diffraction studies. © John Wiley & Sons, Inc. 相似文献