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821.
Cover Picture: Development of a Ruthenium/Phosphite Catalyst System for Domino Hydroformylation–Reduction of Olefins with Carbon Dioxide (Chem. Eur. J. 23/2014)
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822.
Dr. Ivana Nikić Dr. Tilman Plass Dr. Oliver Schraidt Dr. Jędrzej Szymański Dr. John A. G. Briggs Priv.‐Doz. Dr. Carsten Schultz Dr. Edward A. Lemke 《Angewandte Chemie (International ed. in English)》2014,53(8):2245-2249
The growing demands of advanced fluorescence and super‐resolution microscopy benefit from the development of small and highly photostable fluorescent probes. Techniques developed to expand the genetic code permit the residue‐specific encoding of unnatural amino acids (UAAs) armed with novel clickable chemical handles into proteins in living cells. Here we present the design of new UAAs bearing strained alkene side chains that have improved biocompatibility and stability for the attachment of tetrazine‐functionalized organic dyes by the inverse‐electron‐demand Diels–Alder cycloaddition (SPIEDAC). Furthermore, we fine‐tuned the SPIEDAC click reaction to obtain an orthogonal variant for rapid protein labeling which we termed selectivity enhanced (se) SPIEDAC. seSPIEDAC and SPIEDAC were combined for the rapid labeling of live mammalian cells with two different fluorescent probes. We demonstrate the strength of our method by visualizing insulin receptors (IRs) and virus‐like particles (VLPs) with dual‐color super‐resolution microscopy. 相似文献
823.
Oxidative Catalysis Using the Stoichiometric Oxidant as a Reagent: An Efficient Strategy for Single‐Electron‐Transfer‐Induced Tandem Anion–Radical Reactions
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Ing. František Kafka Ing. Martin Holan M.Sc. Denisa Hidasová Dr. Radek Pohl Dr. Ivana Císařová Dr. Blanka Klepetářová Dr. Ullrich Jahn 《Angewandte Chemie (International ed. in English)》2014,53(37):9944-9948
Oxidative single‐electron transfer‐catalyzed tandem reactions consisting of a conjugate addition and a radical cyclization are reported, which incorporate the mandatory terminal oxidant as a functionality into the product. 相似文献
824.
Reverse Spin‐Crossover and High‐Pressure Kinetics of the Heme Iron Center Relevant for the Operation of Heme Proteins under Deep‐Sea Conditions
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Dipl.‐Chem. Oliver Troeppner Dr. Rainer Lippert Dr. Tatyana E. Shubina Dr. Achim Zahl Dr. Norbert Jux Prof. Dr. Ivana Ivanović‐Burmazović 《Angewandte Chemie (International ed. in English)》2014,53(43):11452-11457
By design of a heme model complex with a binding pocket of appropriate size and flexibility, and by elucidating its kinetics and thermodynamics under elevated pressures, some of the pressure effects are demonstrated relevant for operation of heme‐proteins under deep‐sea conditions. Opposite from classical paradigms of the spin‐crossover and reaction kinetics, a pressure increase can cause deceleration of the small‐molecule binding to the vacant coordination site of the heme‐center in a confined space and stabilize a high‐spin state of its Fe center. This reverse high‐pressure behavior can be achieved only if the volume changes related to the conformational transformation of the cavity can offset the volume changes caused by the substrate binding. It is speculated that based on these criteria nature could make a selection of structures of heme pockets that assist in reducing metabolic activity and enzymatic side reactions under extreme pressure conditions. 相似文献
825.
Zirconia—A stationary phase capable of the separation of polar markers of myocardial metabolism in hydrophilic interaction chromatography
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Radim Kučera Petra Kovaříková Ivana Pasáková‐Vrbatová Jitka Slaninová Jiří Klimeš 《Journal of separation science》2014,37(9-10):1089-1093
Creatine, phosphocreatine, and adenine nucleotides are highly polar markers of myocardial metabolism that are poorly retained on RP silica sorbents. Zirconia represents an alternative material to silica with high promise to be used in hydrophilic interaction chromatography (HILIC). This study describes a first systematic investigation of the ability of ZrO2 to separate creatine, phosphocreatine, adenosine 5′‐monophosphate, adenosine 5′‐diphosphate, and adenosine 5′‐triphosphate and compares the results with those obtained on TiO2. All analytes showed a HILIC‐like retention pattern when mobile phases of different strengths were tested. Stronger retention and better column performance were achieved in organic‐rich mobile phases as compared to aqueous conditions, where poor retention and insufficient column performance were observed. The effect of mobile phase pH and ionic strength was evaluated as well. The analysis of myocardial tissue demonstrated that all compounds were separated in a relevant biological material and thus proved ZrO2 as a promising phase for HILIC of biological samples that deserves further investigation. 相似文献
826.
Cariton Kubwabo Ivana Kosarac Kaela Lalonde Warren G. Foster 《Analytical and bioanalytical chemistry》2014,406(18):4381-4392
Bisphenol A (BPA) is a widely used industrial chemical in the manufacturing of polycarbonate plastic bottles, food and beverage can linings, thermal receipts, and dental sealants. Animal and human studies suggest that BPA may disrupt normal hormonal function and hence, potentially, have negative effects on the human health. While total BPA is frequently reported, it is recognized that free BPA is the biologically active form and is rarely reported in the literature. The objective of this study was to develop a sensitive and improved method for the measurement of free and total BPA in human urine. Use of a labeled conjugated BPA (bisphenol A-d6 β-d-glucuronide) allowed for the optimization of the enzymatic reaction and permitted an accurate determination of the conjugated BPA concentration in urine samples. In addition, a 13C12-BPA internal standard was used to account for the analytical recoveries and performance of the isotope dilution method. Solid-phase extraction (SPE) combined with derivatization and analysis using a triple quadrupole GC-EI/MS/MS system achieved very low method detection limit of 0.027 ng/mL. BPA concentrations were measured in urine samples collected during the second and third trimesters of pregnancy in 36 Canadian women. Total maternal BPA concentrations in urine samples ranged from not detected to 9.40 ng/mL (median, 1.21 ng/mL), and free BPA concentrations ranged from not detected to 0.950 ng/mL (median, 0.185 ng/mL). Eighty-six percent of the women had detectable levels of conjugated BPA, whereas only 22 % had detectable levels of free BPA in their urine. BPA levels measured in this study agreed well with data reported internationally. 相似文献
827.
Supramolecular self-assembly of cyclodextrin and higher water soluble guest: thermodynamics and topological studies 总被引:1,自引:0,他引:1
De Sousa FB Denadai AM Lula IS Nascimento CS Fernandes Neto NS Lima AC De Almeida WB Sinisterra RD 《Journal of the American Chemical Society》2008,130(26):8426-8436
The supramolecular interactions between Imipramine hydrochloride (IMI), a tricyclic antidepressant, and beta-cyclodextrin (betaCD) have been investigated by experimental techniques and theoretical calculations. The association between these molecules might be lead to a host/guest compound, in which the physical chemistry properties of the guest molecule, such as high solubility, can be decreased. These new properties acquired by the inclusion phenomena are important to develop a strategy for pharmaceutical formulation. Nuclear magnetic resonance and horizontal attenuated total reflectance provided relevant information on the complex stoichiometries and the sites of interactions between the host and guest molecules. Stoichiometries of 1:2, 1:1, and 2:1 betaCD/IMI have been detected in solution. Self-diffusion coefficient and dynamic light scattering analysis provided information on the self-aggregation of the complex. Also, isothermal titration calorimetry studies indicated the existence of equilibrium between different complexes in solution. In order to determine the preferred arrangement for the inclusion complex formed by the IMI molecule and betaCD, theoretical calculations were performed. Of all proposed supramolecular structures, the 2:1 betaCD/IMI complex was calculated to be the most energetically favorable, in both gas and aqueous phases. The calculations indicated that the intermolecular hydrogen bonds involving the hydroxyl groups of betaCD play a major role in stabilizing the supramolecular 2:1 structure, corroborating experimental findings. 相似文献
828.
Ivana L. Mello 《European Polymer Journal》2008,44(9):2893-2898
Catalysts constituted by neodymium versatate, diisobutylaluminium hydride and t-butyl chloride were used in this work. After their synthesis, they were aged at 40 °C for 48 h. Afterwards, they were maintained at 10 °C for more 5, 15, 40, 80, 160 and 250 days and finally the aged catalysts were evaluated in butadiene polymerization. The polybutadienes were characterized by size exclusion chromatography (SEC) to determine the molecular weight characteristics and by infrared spectroscopy (FTIR) to determine the microstructure. The aim of this work is to evaluate the effect of ageing time on 1,4 polymerization of butadiene. The results showed that the stereoselectivity of the active sites was not affected by the ageing conditions. However, the catalyst activity increased for long times of ageing. 相似文献
829.
Sehnal P Krausova Z Teplý F Stara IG Starý I Rulísek L Saman D Císarova I 《The Journal of organic chemistry》2008,73(6):2074-2082
Diastereoselective CoI-mediated [2 + 2 + 2] cycloisomerization of CH(3)O-substituted optically pure aromatic triynes to obtain nonracemic functionalized helicene-like compounds (comprising a penta-, hexa-, and heptacyclic helical scaffold) was studied. The stereochemical outcome of the reaction at 140 degrees C using CpCo(CO)(2) was controlled by thermodynamic factors yielding diastereomeric ratios up to 91:9. Using CpCo(ethylene)(2) at room temperature, a kinetic control took place leading to the loss of stereoselectivity. Barriers to epimerization for selected helicene-like compounds were measured indicating their lower configurational stability in comparison to the parent carbohelicenes. Free energy differences between corresponding pairs of diastereomers (calculated at the DFT B3LYP/TZV+P level) were in excellent agreement with the experimental data and allowed for the prediction of the stereochemical outcome of the reaction. An optically pure hexacyclic helicene-like alcohol was prepared on a multigram scale. Its X-ray structure confirmed the previous helicity assignments being based on (1)H-(1)H correlations in ROESY (1)H NMR spectra. 相似文献
830.
Petr Štěpni?ka Martin Zábranský Ivana Císa?ová Martin Lama? 《Journal of organometallic chemistry》2008,693(26):3831-3841
(Ferrocenylmethyl)(2-hydroxyethyl)amine (1) reacts with mono- (CH3CO2H and PhCO2H) and dicarboxylic acids (HO2C(CH2)nCO2H (n = 0-2), (E)- and (Z)-HO2CCHCHCO2H) to give the respective carboxylates, viz [1H](RCO2) (2, R = CH3; 3, R = Ph), [1H]2(O2C(CH2)nCO2) (4, n = 0; 5, n = 1; 6, n = 2), [1H]2((E)-O2CCHCHCO2) (7) and [1H]2((Z)-HO2CCHCHCO2) (8), as defined crystalline solids. Crystal structures of 2-8 have been determined by single-crystal X-ray diffraction analysis, revealing extensive hydrogen bonding interactions based predominantly on charge-supported N+-H···O− and O-H···O− hydrogen bonds, and on C-H···O contacts. Whereas the crystal assemblies of the monocarboxylate salts propagate preferentially in one dimension (2: cross-linked chains, 3: columnar stacks), those of the salts prepared from the dicarboxylic acids (including hydrogenmaleate 8) are best described as layered composite arrays resulting via alternation of polar, hydrogen-bonded layers and of non-polar sheets constituted by the ferrocenyl substituents. 相似文献