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101.
Dorota G. Piotrowska 《Tetrahedron》2009,65(22):4310-1839
Aziridinium mesylates stable in the reaction medium for several hours to over a week were observed in a rearrangement of dimethyl (1R,2S)-2-(N,N-dibenzylamino)-1-mesyloxyethylphosphonates substituted at C2 with Bn, i-Pr and t-Bu to the respective 1-(N,N-dibenzylamino)-2-mesyloxyethylphosphonates. Rates of formation of these aziridinium mesylates and rates of their reactions with poorly nucleophilic mesylate anion were governed by steric and electronic factors. The conformation of (2S,3S)-1,1-dibenzyl-2-(tert-butyl)-3-(dimethoxyphosphoryl)aziridinium mesylate in solution was established based on 1H and 13C NMR spectroscopic studies including a NOESY experiment. 相似文献
102.
Sajewicz Mieczysław Kronenbach Dorota Gontarska Monika Wróbel Magdalena Piętka Robert Kowalska Teresa 《平面色谱法杂志一现代薄层色谱法》2009,22(4):241-248
JPC – Journal of Planar Chromatography – Modern TLC - As a result of our earlier studies, we were the first research group to report the spontaneous oscillatory in-vitro chiral... 相似文献
103.
Gradient elution has been studied in typical normal and reversed-phase systems. Deformations of gradient profiles have been evidenced as a result of preferential adsorption of modifiers of the mobile phase. This phenomenon was pronounced in the normal-phase system, for which gradient profiles deviated significantly from those programmed. This influenced the retention and shapes of band profiles of the eluting solute. Hence, in order to predict gradient propagation correctly the adsorption equilibrium of modifiers has been quantified. Moreover, at low modifier content, deformations of band profiles of the solute has been registered as a result of the competitive adsorption in the system solute-modifier. This effect has been predicted by a competitive adsorption model. For the reversed-phase systems the influence of the modifier adsorption on gradient propagation was insignificant for typical mobile phases investigated. Therefore, the work has been focused on gradient predictions in the normal-phase system. 相似文献
104.
Dorota Prukala 《Journal of heterocyclic chemistry》2006,43(2):337-344
Sixteen new fluorescent N4‐(E)‐stilbenyloxyalkylcarbonyl‐cytosines 9–16 and N4‐(E)‐stilbenyloxyalkylcarbonyl‐1‐methylcytosines 17–24 have been synthesized. The differences in 1H and 13C NMR spectra in two solvents (DMSO and TFA) have been pointed out and discussed. Assignment of the signals in the spectra of the compounds 9–24 in NMR in DMSO‐d6 solutions has been made the basis of the homonuclear (COSY) and heteronuclear (HETCOR) spectra. The effect of the substituent (Cl, Br, NO2) on the stilbene moiety on the fluorescence spectrum of each compound has been discussed. 相似文献
105.
We review evolution equations for the truncated Mellin moments of the parton distributions and some their applications in QCD analysis. The main finding of the presented approach is that the nth truncated moment of the parton distribution obeys also the DGLAP equation but with a rescaled splitting function P′(z) = z n P(z). This allows one to avoid the problem of dealing with the experimentally unexplored Bjorken-x region. The evolution equations for truncated moments are universal—they are valid in each order of perturbation expansion and can be useful additional tool in analysis of unpolarized as well as polarized nucleon structure functions. 相似文献
106.
Jakubczyk D Barth C Kubas A Anastassacos F Koelsch P Fink K Schepers U Brenner-Weiß G Bräse S 《Analytical and bioanalytical chemistry》2012,403(2):473-482
N-Acyl-l-homoserine lactones (AHLs) are synthesized by Gram-negative bacteria. These quorum-sensing molecules play an important role
in the context of bacterial infection and biofilm formation. They also allow communication between microorganisms and eukaryotic
cells (inter-kingdom signalling). However, very little is known about the entire mechanism of those interactions. Precise
structural studies are required to analyse the different AHL isomers as only one form is biologically most active. Theoretical
studies combined with experimental infrared and Raman spectroscopic data are therefore undertaken to characterise the obtained
compounds. To mimic interactions between AHL and cell membranes, we studied the insertion of AHL in supported lipid bilayers,
using vibrational sum-frequency-generation spectroscopy. Deuterium-labelled AHLs were thus synthesized. Starting from readily
available deuterated fatty acids, a two-step procedure towards deuterated N-acyl-l-homoserine lactones with varying chain lengths is described. This included the acylation of Meldrum’s acid followed by amidation.
Additionally, the detailed analytical evaluation of the products is presented herein. 相似文献
107.
S Monari G Battistuzzi CA Bortolotti S Yanagisawa K Sato C Li I Salard D Kostrz M Borsari A Ranieri C Dennison M Sola 《Journal of the American Chemical Society》2012,134(29):11848-11851
The hydrophobic patch of azurin (AZ) from Pseudomonas aeruginosa is an important recognition surface for electron transfer (ET) reactions. The influence of changing the size of this region, by mutating the C-terminal copper-binding loop, on the ET reactivity of AZ adsorbed on gold electrodes modified with alkanethiol self-assembled monolayers (SAMs) has been studied. The distance-dependence of ET kinetics measured by cyclic voltammetry using SAMs of variable chain length, demonstrates that the activation barrier for short-range ET is dominated by the dynamics of molecular rearrangements accompanying ET at the AZ-SAM interface. These include internal electric field-dependent low-amplitude protein motions and the reorganization of interfacial water molecules, but not protein reorientation. Interfacial molecular dynamics also control the kinetics of short-range ET for electrostatically and covalently immobilized cytochrome c. This mechanism therefore may be utilized for short-distance ET irrespective of the type of metal center, the surface electrostatic potential, and the nature of the protein-SAM interaction. 相似文献
108.
We present a simple derivation of the spectra of the action variables of the quantized compactified Ruijsenaars-Schneider system. We obtain the spectra by combining K?hler quantization with the identification of the classical action variables as a standard toric moment map on a complex projective space. The result is consistent with the Schr?dinger quantization of the system previously developed by van Diejen and Vinet. 相似文献
109.
The Mitochondria-Independent Cytotoxic Effect of Leflunomide on RPMI-8226 Multiple Myeloma Cell Line
Grzegorz Adamczuk Ewelina Humeniuk Magdalena Iwan Dorota Natorska-Chomicka Kamila Adamczuk Agnieszka Korga-Plewko 《Molecules (Basel, Switzerland)》2021,26(18)
Leflunomide, an anti-inflammatory agent, has been shown to be effective in multiple myeloma (MM) treatment; however, the mechanism of this phenomenon has not been fully elucidated. The aim of the study was to assess the role of mitochondria and dihydroorotate dehydrogenase (DHODH) inhibition in the cytotoxicity of leflunomide in relation to the MM cell line RPMI 8226. The cytotoxic effect of teriflunomide—an active metabolite of leflunomide—was determined using MTT assay, apoptosis detection, and cell cycle analysis. To evaluate DHODH-dependent toxicity, the cultures treated with teriflunomide were supplemented with uridine. Additionally, the level of cellular thiols as oxidative stress symptom was measured as well as mitochondrial membrane potential and protein tyrosine kinases (PTK) activity. The localization of the compound in cell compartments was examined using HPLC method. Teriflunomide cytotoxicity was not abolished in uridine presence. Observed apoptosis occurred in a mitochondria-independent manner, there was also no decrease in cellular thiols level. Teriflunomide arrested cell cycle in the G2/M phase which is not typical for DHODH deficiency. PTK activity was decreased only at the highest drug concentration. Interestingly, teriflunomide was not detected in the mitochondria. The aforementioned results indicate DHODH- and mitochondria-independent mechanism of leflunomide toxicity against RPMI 8226 cell line. 相似文献
110.
Michalina Zaborowska Damian Dziubak Dorota Matyszewska Slawomir Sek Renata Bilewicz 《Molecules (Basel, Switzerland)》2021,26(18)
A model biomimetic system for the study of protein reconstitution or drug interactions should include lipid rafts in the mixed lipid monolayer, since they are usually the domains embedding membrane proteins and peptides. Four model lipid films composed of three components: 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), cholesterol (Chol) and sphingomyelin (SM) mixed in different molar ratios were proposed and investigated using surface pressure measurements and thermodynamic analysis of the monolayers at the air–water interface and imaged by Brewster angle microscopy. The ternary monolayers were transferred from the air–water onto the gold electrodes to form bilayer films and were studied for the first time by electrochemical methods: alternative current voltammetry and electrochemical impedance spectroscopy and imaged by atomic force microscopy. In excess of DOPC, the ternary systems remained too liquid for the raft region to be stable, while in the excess of cholesterol the layers were too solid. The layers with SM in excess lead to the formation of Chol:SM complexes but the amount of the fluid matrix was very low. The equimolar content of the three components lead to the formation of a stable and well-organized assembly with well-developed raft microdomains of larger thickness, surrounded by the more fluid part of the bilayer. The latter is proposed as a convenient raft model membrane for further physicochemical studies of interactions with drugs or pollutants or incorporation of membrane proteins. 相似文献