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991.
Caroline Vanderghem Pascal Boquel Christophe Blecker Michel Paquot 《Applied biochemistry and biotechnology》2010,160(8):2300-2307
Cellobiose, a disaccharide, is a valuable product that can be obtained from cellulose hydrolysis. In this study, a simple
methodology is presented to enhance the production and improve the selectivity of cellobiose during enzymatic hydrolysis of
cellulose. The approach consisted of a multistage removal of filtrate via vacuum filtration and resuspension of the retentate.
By this process, the remaining solid was further hydrolyzed without additional enzyme loading. Compared to the continuous
hydrolysis process, the production of cellobiose increased by 45%. Increased selectivity of cellobiose is due to the loss
of β-glucosidases in the filtrate, while enhanced productivity is likely due to mitigated product inhibition. 相似文献
992.
Abstract Polymerizations of racemic- and meso-d,l-lactide were conducted at 120°C in xylylene or in bulk. Lead oxide (PbO), zinc stearate, antimony(III) 2-ethylhexanoate, and bismuth(III) 2-ethylhexanoate were used as initiators. With PbO and Zn stearate, bulk polymerizations were also conducted at 150°C. High yields (?90%) were only obtained with PbO and Bi(III) 2-ethylhexanoate, but the molecular weights were low in all cases. The stereosequences were analyzed by 1H- and 13C-NMR spectroscopy. A significant stereospecificity was never detected. At higher reaction temperatures the resulting stereosequences show an increasing tendency toward randomness. 相似文献
993.
HR‐MAS NMR metabolomics of ‘Swingle’ citrumelo rootstock genetically modified to overproduce proline
Caroline S. de Oliveira Eduardo F. Carlos Luiz G. E. Vieira Luciano M. Lião Glaucia B. Alcantara 《Magnetic resonance in chemistry : MRC》2014,52(8):422-429
The accumulation of proline is a typical physiological response to abiotic stresses in higher plants. ‘Swingle’ citrumelo, an important rootstock for citrus production, has been modified with a mutated Δ1‐pyrroline‐5‐carboxylate synthetase gene (VaP5CSF129A) linked to the cauliflower mosaic virus 35S promoter to induce the overproduction of free proline. This paper presents a comparative metabolomic study of nontransgenic versus transgenic ‘Swingle’ citrumelo plants with high endogenous proline. 1H high‐resolution magic angle spinning nuclear magnetic resonance spectroscopy and multivariate analysis showed significant differences in some metabolites between the nontransgenic and transgenic leaves and roots. The overproduction of proline has reduced the sucrose content in transgenic leaves, revealing a metabolic cost for these plants. In roots, the high level of free proline acts for the adjustment of cation–anion balance, causing the reduction of acetic acid content. The same sucrose level in roots indicates that they can be considered as sucrose sink. Similar behavior may be waited for fruits produced on transgenic rootstock. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
994.
Alissa M. Chan Laura A. Peña Rosa E. Segura Ramya Auroprem Brent M. Harvey Caroline M. Brooke Patrick E. Hoggard 《Photochemistry and photobiology》2013,89(2):274-279
Dissolved hexachlororuthenate(IV) effectively catalyzes the photodecomposition of chloroform to hydrogen chloride and phosgene under near‐UV (λ > 345 nm) irradiation, whereby RuCl62? is not itself photocatalytically active, but is photochemically transformed into a species that is active, possibly RuCl5(CHCl3)?. Conversion to a photoactive species during irradiation is consistent with the acceleration of the decomposition rate during the early stages and with the apparent inverse dependence of the decomposition rate on the initial concentration of RuCl62?. The displacement of Cl? by CHCl3 in the coordination sphere to create the photoactive species is consistent with the retardation of photodecomposition by both Cl? and H2O. The much smaller photodecomposition rate in CDCl3 suggests that C–H bond dissociation occurs during the primary photochemical event, which is also consistent with the presence of a CHCl3 molecule in the first coordination sphere. 相似文献
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998.
Caroline Chauvin Pierre Thibault Daniel Plusquellec Joseph Banoub 《Journal of carbohydrate chemistry》2013,32(4-5):459-475
Abstract Structural characterization and differentiation of distinct regioisomenc esters of sucrose were obtained using lonspray ionization and low energy tandem mass spectrometry. Low energy CAD MS/MS analyses of the protonated molecules [M + H]+ provided characteristic fingerprint patterns, and permitted differentiation of the various regioisomers. MS/MS analyses of selected intermediate fragment ions formed during the ionization process provided additional structural data, and established the fragmentation routes of their [M + H]+ precursors. 相似文献
999.
Roman M Cannizzo C Pinault T Isare B Andrioletti B van der Schoot P Bouteiller L 《Journal of the American Chemical Society》2010,132(47):16818-16824
Gathering precise knowledge on weak supramolecular interactions is difficult yet is of utmost importance for numerous scientific fields, including catalysis, crystal engineering, ligand binding, and protein folding. We report on a combined theoretical and experimental approach showing that it is possible to vastly improve the sensitivity of current methods to probe weak supramolecular interactions in solution. The concept consists of using a supramolecular platform involving a highly cooperative configurational transition, the perturbation of which (by the modification of the molecular building blocks) can be monitored in a temperature scanning experiment. We tested this concept with a particular bisurea platform, and our first results show that it is possible to detect the presence of interaction differences as low as 60 J/mol, which may be due to steric repulsion between vinyl and alkyl groups or may be the result of solvation effects. 相似文献
1000.
Clarke CS Jornet-Somoza J Mota F Novoa JJ Deumal M 《Journal of the American Chemical Society》2010,132(50):17817-17830
The magnetic bistability present in some molecule-based magnets is investigated theoretically at the microscopic level using the purely organic system TTTA (1,3,5-trithia-2,4,6-triazapentalenyl). The TTTA crystal is selected for being one of the best-studied molecule-based systems presenting magnetic bistability. The magnetic properties of the high- and low-temperature structures (HT and LT phases, respectively) are accurately characterized by performing a First-Principles Bottom-Up study of each phase. The changes that the magnetic exchange coupling constants (J(AB)) undergo when the temperature is raised (LT → HT) or lowered (HT → LT) are also fully explored in order to unravel the reasons behind the presence of these two different pathways. The triclinic LT phase is diamagnetic due to the fact that the nearly eclipsed π dimer is effectively magnetically silent and not to formation of a covalent bond between two TTTA molecules. It is also shown that bistability in TTTA results from the coexistence of the monoclinic HT and triclinic LT phases in the temperature range studied. 相似文献