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81.
The protonation processes for eight three-membered ring molecules have been investigated using the SCF LCAO MO method with Gaussian basis sets and the results are compared with those obtained at the first order approximation, i.e. the electrostatic approximation. The electrostatic results are linearly connected with the SCF ones and are sufficient to get an ordering of the protonation energies in different chemical sites and to obtain reliable representations of the proton approaching paths. 相似文献
82.
Caterina Minelli Christoph Frommen Christian Hinderling Raphael Pugin Harry Heinzelmann Martha Liley 《Colloid and polymer science》2006,284(5):482-488
Polymer/nanoparticle composite films are receiving growing attention thanks to their potential for application in ultra-thin
electronic and optical devices. Polymer blend demixing has been shown to be a suitable technique for the structuring of polymer
thin films and the patterning of nanoparticles (NP) within them. In this work we show that the morphology of thin polymer
films made by spin-casting a polymer blend solution containing NP fillers on a surface depends strongly on the concentration
of NP fillers. More specifically, polystyrene/polymethylmethacrylate (PS/PMMA) films formed from a toluene solution, and which
demix following a nucleation and growth mechanism, were studied. It was found that both the height and the surface density
of PMMA domains increased as the concentration of CoPt:Cu NPs in the film was increased. We find that similar effects are
induced in a NP-free PS/PMMA demixed film upon increasing the molecular weight of the PS molecules. This suggests that under
certain conditions the NPs and the polymer molecules in the blend do not behave as separate species but form aggregates. 相似文献
83.
Bissantz C Logean A Rognan D 《Journal of chemical information and computer sciences》2004,44(3):1162-1176
The current study describes the development of a computer package (GPCRmod) aimed at the high-throughput modeling of the therapeutically important family of human G-protein coupled receptors (GPCRs). GPCRmod first proposes a reliable alignment of the seven transmembrane domains (7 TMs) of most druggable human GPCRs based on pattern/motif recognition for each of the 7 TMs that are considered independently. It then converts the alignment into knowledge-based three-dimensional (3-D) models starting from a set of 3-D backbone templates and two separate rotamer libraries for side chain positioning. The 7 TMs of 277 human GPCRs have been accurately aligned, unambiguously clustered in three different classes (rhodopsin-like, secretin-like, metabotropic glutamate-like), and converted into high-quality 3-D models at a remarkable throughput (ca. 3s/model). A 3-D GPCR target library of 277 receptors has consequently been setup. Its utility for "in silico" inverse screening purpose has been demonstrated by recovering among top scorers the receptor of a selective GPCR antagonist as well as the receptors of a promiscuous antagonist. The current GPCR target library thus constitutes a 3-D database of choice to address as soon as possible the "virtual selectivity" profile of any GPCR antagonist or inverse agonist in an early hit optimization process. 相似文献
84.
Ion chromatographic determination of sulfide and cyanide in real matrices by using pulsed amperometric detection on a silver electrode 总被引:1,自引:0,他引:1
The determination of free sulfide and cyanide by pulsed amperometric detection (PAD) at a silver-working electrode was improved through a deep de-oxygenation (at least 10 min) of both standard and real solutions containing the two analytes and adopting a two-potential waveform able to eliminate Ag working electrode fouling. The waveform stepped around the oxidation of Ag in the presence of 0.1-0.4 M hydroxyl ion, from -0.1 to 0.1 V versus saturated calomel electrode (SCE). The eluent composition (0.4 M NaOH plus 7.5 mM oxalate solution) allowed a very good column efficiency and selectivity. The presence of a polysulfide species was hypothesized in sulfide solutions that had not been de-oxygenated and aged. The polysulfide eluted just before sulfide and was confirmed by a chemical test with SO3(2-) producing the elimination of the polysulfide peak. Detection limits, according to the Hubaux-Vos method, were 1.0 and 2.0 microg/l for S2- and CN , respectively. We demonstrated good performance of the optimized method by repeatedly injecting standard solutions and by analyzing different real matrices. The method exhibited very good accuracy and repeatability (10 microg/l and a 500 microl injection loop, had a repeatability better than 3% for sulfide and 100 microg/l had a repeatability better than 1% for cyanide). The two-potential waveform ensured long-term stability of the electrode surface that required no manual polishing procedure for at least 1 month (20 analysis per day). 相似文献
85.
A spectrophotometric method for the rapid measurement of thiocyanate in serum and urine without separation from interfering substances is described. Thiocyanate reacts immediately with chloramine-T in presence of iron(III) chloride catalyst to give cyanogen chloride, which reacts with a mixture of γ-picoline (4-methylpyridine) and barbituric acid to form a soluble violet—blue product, which is measured at 605 nm. Other components of physiological fluids react more slowly and do not interfere if the reaction time of the chlorinating step is kept very short. The proposed procedure is compared with a highly selective method, based on the oxidation of thiocyanate to cyanide, and good agreement was obtained for both serum and urine. The method is readily adapted to a continuous-flow procedure with a Technicon AutoAnalyzer. 相似文献
86.
Dr. Caterina Viglianisi Kristian Vasa Dr. Damiano Tanini Prof. Antonella Capperucci Dr. Riccardo Amorati Prof. Luca Valgimigli Dr. Andrea Baschieri Prof. Stefano Menichetti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(38):9108-9116
Symmetrical ditocopheryl disulfides ( Toc ) 2 S2 and symmetrical and unsymmetrical ditocopheryl sulfides ( Toc )2 S were simply prepared under remarkably mild conditions with complete control of the regiochemistry by using δ-, γ-, and β-tocopheryl-N-thiophthalimides ( Toc-NSPht ) as common starting materials. The roles of sulfur atom(s), H-bond and aryl ring substitution pattern on the antioxidant profile of these new compounds, which were assembled by linking together two tocopheryl units, are also discussed. 相似文献
87.
Prof. Lucia D'Accolti Dr. Cosimo Annese Dr. Caterina Fusco 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(52):12003-12017
The successful isolation and characterization of a dioxirane species in 1988 opened up one of the most attractive methods for the efficient oxidation of simple and/or structurally complex molecules. Dioxirane today rank among the most powerful tools in organic chemistry, with numerous applications in commercially important processes. They were quickly recognized as efficient oxygen transfer agents, especially for epoxidations and for a wide range of O-insertion reactions into C−H bonds. Dioxirane possess catalytic activity and appear as highly (chemo-, regio-, and stereo-) selective oxidants, despite their reactivity under mild and strictly neutral conditions being controlled by a combination of steric and electronic factors. In this review, we discuss some of the most recent and significant developments in the selective homogeneous and heterogeneous oxyfunctionalization of non-activated C−H bonds in hydrocarbons of natural and non-natural targets by using isolated dioxirane or, more generally, by using the ketones (i.e., the dioxirane precursors) as organocatalysts. 相似文献
88.
The three-dimensional structure of an optically active substituted s-triazine derivative, 2-chloro-4-methoxy-6-[(R)-1-phenylethylamino]-1,3,5-triazine,
has been studied by conformational analysis using density functional theory (DFT) both in vacuo and in acetonitrile solution
in the polarizable continuum model integral equation formalism framework. Time-dependent DFT methods have been used to investigate
the molecular electronic CD and absorption UV spectra. Comparison with experimental results allowed the reliability of the
theoretical predictions to be enhanced and suggested a possible interpretation of the measured data.
Electronic Supplementary Material The online version of this article doi:contains supplementary material, which is available to authorized users. 相似文献
89.
Caterina Migliorini Elena Porciatti Marek Luczkowski Daniela Valensin 《Coordination chemistry reviews》2012,256(1-2):352-368
Metal ions, especially redox active copper, are thought to play critical roles in neurodegenerative disorders. As a matter of fact, metal binding may result into severe conformational changes of proteins involved in neurodegeneration. The present review describes the interactions of metal ions with model peptides mimicking metal binding sites of such proteins, including the prion protein, the β-amyloid and the α-synuclein that have been related to the pathological onset of spongiform encephalopathies, Alzheimer's disease and Parkinson's disease, respectively. Using short protein fragments provides successful tools for characterizing the metal ion interaction with protein domains devoid of any defined secondary structure, and allows one to gain structural information on the metal ion binding properties of the corresponding proteins. Moreover, such an approach based on simplified models yields a multidimensional knowledge that would be never accessible for the natural systems, thus providing a significant and powerful tool for biochemical studies. 相似文献
90.
Marina Naldi Gloria Brusotti Gabriella Massolini Vincenza Andrisano Caterina Temporini Manuela Bartolini 《Molecules (Basel, Switzerland)》2021,26(14)
A combination of flash chromatography, solid phase extraction, high-performance liquid chromatography, and in vitro bioassays was used to isolate phytocomponents endowed with anticholinesterase activity in extract from Phyllanthus muellarianus. Phytocomponents responsible for the anti-cholinesterase activity of subfractions PMF1 and PMF4 were identified and re-assayed to confirm their activity. Magnoflorine was identified as an active phytocomponent from PMF1 while nitidine was isolated from PMF4. Magnoflorine was shown to be a selective inhibitor of human butyrylcholinesterase—hBChE (IC50 = 131 ± 9 μM and IC50 = 1120 ± 83 μM, for hBuChE and human acetylcholinesterase—hAChE, respectively), while nitidine showed comparable inhibitory potencies against both enzymes (IC50 = 6.68 ± 0.13 μM and IC50 = 5.31 ± 0.50 μM, for hBChE and hAChE, respectively). When compared with the commercial anti-Alzheimer drug galanthamine, nitidine was as potent as galanthamine against hAChE and one order of magnitude more potent against hBuChE. Furthermore, nitidine also showed significant, although weak, antiaggregating activity towards amyloid-β self-aggregation. 相似文献