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91.
The adsorption of sodium poly(4-styrene sulfonate) on oppositely charged beta-FeOOH particles is studied by electrooptics. The focus of this paper is on the release of condensed counterions from adsorbed polyelectrolyte upon surface charge overcompensation. The fraction of condensed Na+ counterions on the adsorbed polyion surface is estimated according to the theory of Sens and Joanny and it is compared with the fraction of condensed counterions on nonadsorbed polyelectrolyte. The relaxation frequency of the electrooptical effect from the polymer-coated particle is found to depend on the polyelectrolyte molecular weight. This is attributed to polarization of the layer from condensed counterions on the polyion surface, being responsible for creation of the effect from particles covered with highly charged polyelectrolyte. The number of the adsorbed chains is calculated also assuming counterion condensation on the adsorbed polyelectrolyte and semiquantative agreement is found with the result obtained from the condensed counterion polarizability of the polymer-coated particle. Our findings are in line with theoretical predictions that the fraction of condensed counterions remains unchanged due to the adsorption of highly charged polyelectrolyte onto weakly charged substrate. 相似文献
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Dr. Xi Liu Dr. Viktoria Fabos Stuart Taylor Prof. David W. Knight Dr. Keith Whiston Prof. Graham J. Hutchings 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(35):12290-12294
We report the direct production of 1,3‐butadiene from the dehydration of 2,3‐butandiol by using alumina as catalyst. Under optimized kinetic reaction conditions, the production of methyl ethyl ketone and isobutyraldehyde, formed via the pinacol–pinacolone rearrangement, was markedly reduced and almost 80 % selectivity to 1,3‐butadiene and 1,3‐butadiene could be achieved. The presence of water plays a critical role in the inhibition of oligomerization. The amphoteric nature of γ‐Al2O3 was identified as important and this contributed to the improved catalytic selectivity when compared with other acidic catalysts. 相似文献
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Dr. Viktoria H. Gessner Florian Meier Diana Uhrich Prof. Dr. Martin Kaupp 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(49):16729-16739
Herein, we report the preparation of a new unsymmetrical, bis(thiophosphinoyl)‐substituted dilithio methandiide and its application for the synthesis of zirconium‐ and palladium‐carbene complexes. These complexes were found to exhibit remarkably shielded 13C NMR shifts, which are much more highfield‐shifted than those of “normal” carbene complexes. DFT calculations were performed to determine the origin of these observations and to distinguish the electronic structure of these and related carbene complexes compared with the classical Fischer and Schrock‐type complexes. Various methods show that these systems are best described as highly polarized Schrock‐type complexes, in which the metal–carbon bond possesses more electrostatic contributions than in the prototype Schrock systems, or even as “masked” methandiides. As such, geminal dianions represent a kind of “extreme” Schrock‐type ligands favoring the ionic resonance structure M+? CR2? as often used in textbooks to explain the nucleophilic nature of Schrock complexes. 相似文献
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Trimeric diphenylanthracene macrocycles were synthesized via the zirconocene-mediated coupling of 9,10-bis-[4-trimethylsilyl(ethynyl)phenyl]anthracene. The macrocycles feature a strained architecture due to orientation of the anthracene units into the plane of the macrocycle. The demetalated cyclophane exhibits a considerably higher flexibility in solution, while the zirconocene-containing macrocycle is quite rigid. 相似文献
99.
Thioflavin T (ThT) is a molecular-rotor-type fluorophore reputed for the selective binding to amyloid fibrils. Using induced circular dichroism, here we show that ThT binds in an orderly manner to α-helical poly-L-glutamic acid (PLGA) implying that neither stacked β-sheets nor π-π stacking interactions are necessary for the binding between the dye and proteins. 相似文献
100.
Tanja Freichel Viktoria Heine Dominic Laaf Eleanor E. Mackintosh Sophia Sarafova Lothar Elling Nicole L. Snyder Laura Hartmann 《Macromolecular bioscience》2020,20(9)
Within this work, a new class of sequence‐defined heteromultivalent glycomacromolecules bearing lactose residues and nonglycosidic motifs for probing glycoconjugate recognition in carbohydrate recognition domain (CRD) of galectin‐3 is presented. Galectins, a family of β‐galactoside‐binding proteins, are known to play crucial roles in different signaling pathways involved in tumor biology. Thus, research has focused on the design and synthesis of galectin‐targeting ligands for use as diagnostic markers or potential therapeutics. Heteromultivalent precision glycomacromolecules have the potential to serve as ligands for galectins. In this work, multivalency and the introduction of nonglycosidic motifs bearing either neutral, amine, or sulfonated/sulfated groups are used to better understand binding in the galectin‐3 CRD. Enzyme‐linked immunosorbent assays and surface plasmon resonance studies are performed, revealing a positive impact of the sulfonated/sulfated nonglycosidic motifs on galectin‐3 binding but not on galectin‐1 binding. Selected compounds are then tested with galectin‐3 positive MCF 7 breast cancer cells using an in vitro would scratch assay. Preliminary results demonstrate a differential biological effect on MCF 7 cells with high galectin‐3 expression in comparison to an HEK 293 control with low galectin‐3 expression, indicating the potential for sulfonated/sulfated heteromultivalent glycomacromolecules to serve as preferential ligands for galectin‐3 targeting. 相似文献