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81.
82.
Dieter Seebach Werner Wykypiel Winfried Lubosch Hans-Otto Kalinowski 《Helvetica chimica acta》1978,61(8):3100-3102
On the Sterochemical Course of Electrophilic Substitution at CH Groups in α-Position to the N-Atom of Hindered Amides It is shown by 1H-NMR. analysis of the aminoalcohol derivatives 4b and 4c that the lithiation/hydroxyalkylation with acetone of 1-nitroso-and 1-(2,4,6-triiso-propylbenzoyl)-4-phenyl-piperidine leads to configurationally different products. The assigned cis and trans configuration of the substituents in 4b and 4c , respectively, is compatible with the electronic structures 2 and 1 , respectively, which were previously proposed for the lithio-derivatives 3 involved in such transformations. 相似文献
83.
Kalinowski J Mezyk J Meinardi F Tubino R Cocchi M Virgili D 《The Journal of chemical physics》2008,128(12):124712
We investigate quenching mechanisms of excited states in emitter layers for organic light emitting diodes (LEDs). An extensive study of a strong electric field-induced modulation (over 50%) of the time-resolved luminescence in a diamine derivative (TPD): polycarbonate blend films doped with an organic complex of europium are presented as a typical example of an important class of emitters for organic monochromatic LEDs. Using this method allowed us to identify the quenched species as the excited ligand precursors of the emissive europium ion states. Manipulating the electrode materials and their electrical bias, the electric field-enhanced dissociation, and interaction with injected charge could be separated and found as principal quenching mechanisms. We show the first one to follow the three-dimensional Onsager theory of geminate recombination, and the second one raised by their interaction with the TPD-transported holes. The interaction rate constant is found to be underlain by the three-dimensional diffusion of excited ligand singlets, combining the exciton diffusion coefficient and long-range (Forster type) energy transfer parameters. The dynamic parameters of the hole-precursor excitons interactions, extracted from the experimental data, allow us to establish the criteria for identifying useful ligands and matrices in the optimized design of electrophosphorescent, linelike emitting molecules, and device structure for organic LEDs. 相似文献
84.
Edyta Nalewajko-Sieliwoniuk Magdalena Iwanowicz Sławomir Kalinowski Anatol Kojło 《Analytica chimica acta》2016
In this work, we present a novel chemiluminescence (CL) method based on direct-injection detector (DID) integrated with the multi-pumping flow system (MPFS) to chemiluminescence determination of the total polyphenol index. In this flow system, the sample and the reagents are injected directly into the cone-shaped detection cell placed in front of the photomultiplier window. Such construction of the detection chamber allows for fast measurement of the CL signal in stopped-flow conditions immediately after mixing the reagents. The proposed DID-CL-MPFS method is based on the chemiluminescence of nanocolloidal manganese(IV)-hexametaphosphate-ethanol system. The application of ethanol as a sensitizer, eliminated the use of carcinogenic formaldehyde. Under the optimized experimental conditions, the chemiluminescence intensities are proportional to the concentration of gallic acid in the range from 5 to 350 ng mL−1. The DID-CL-MPFS method offers a number of advantages, including low limit of detection (0.80 ng mL−1), high precision (RSD = 3.3%) and high sample throughput (144 samples h−1) as well as low consumption of reagents, energy and low waste generation. The proposed method has been successfully applied to determine the total polyphenol index (expressed as gallic acid equivalent) in a variety of plant-derived food samples (wine, tea, coffee, fruit and vegetable juices, herbs, spices). 相似文献
85.
Kalinowski S Koronkiewicz S Kotulska M Kubica K 《Bioelectrochemistry (Amsterdam, Netherlands)》2007,70(1):83-90
Chronopotentiometry on planar lipid bilayer (BLM) is proposed as a method for modeling the electrical phenomena in electroporated cell. Two techniques are discussed: constant-current and linear-current chronopotentiometry. It is proposed that the constant-current chronopotentiometry may provide basis for modeling the electroporated cell shortly after the removal of the electric field, when activity of cellular pumps counteracts ionic fluxes through the electropore and ionic channels. The linear-current method can be considered for modeling the cell in the later stage after electroporation, when energetical resources of the cell are gradually getting exhausted and the activity of pumps decreases. Based on this idea, it may be postulated that the electropore in the cell has fluctuating dynamics whose stochastic characteristics, similarly as biological channels, shows 1/f noise. The model implies that the fluctuations would disappear leaving the electropore with a constant resistance when efficiency of the pumps becomes very small. The results of chronopotentiometry also may suggest that opening time, conductivity and selectivity of the electropore can be controlled by the cell environment or membrane composition. 相似文献
86.
Anselmetti D Hansmeier N Kalinowski J Martini J Merkle T Palmisano R Ros R Schmied K Sischka A Toensing K 《Analytical and bioanalytical chemistry》2007,387(1):83-89
Analytics of single biological cells allows quantitative investigation from a structural, functional and dynamical point of
view and opens novel possibilities to an unamplified subcellular analysis. In this article, we report on three different experimental
methods and their applications to single cellular systems with a subcellular sensitivity down to the single molecule level.
First, the subcellular surface structure of living bacteria (Corynebacterium glutamicum) was investigated with atomic force microscopy (AFM) at the resolution of individual surface layer (S-layer) proteins; discrimination
of bacterial strains that lack the expression of hexagonally packed surface layer proteins was possible. Second, quantitative
measurement of individual recognition events of membrane-bound receptors on living B-cells was achieved in single cell manipulation
and probing experiments with optical tweezers (OT) force spectroscopy. And third, intracellular dynamics of translocating
photoactivatable GFP in plant protoplasts (Nicotiana tabacum BY-2) was quantitatively monitored by two-photon laser scanning microscopy (2PLSM). 相似文献
87.
The unsymmetrical distribution of the unpaired electron in the ground state of the DBTTFI(?-) radical anion (bi(6-n-butyl-5,7-dioxo-6,7-dihydro-5H-[1,3]dithiolo[4,5-f]isoindole-2-ylidene) is theoretically predicted using the M06-2X/6-31+G(d,p) level of calculations. The results are additionally confirmed by single point calculations at B3LYP/aug-cc-pVTZ, LC-ωPBE/aug-cc-pVTZ, and M06-2X/aug-cc-pVTZ levels. DBTTFI, containing the TTF (tetrathiafulvalene) fragment, may be used in the construction of organic microelectronic devices, similarly to the radical anion of QTTFQ. The unsymmetrical distribution of spin density in (QTTFQ)(?-) has been confirmed using M06-2X/aug-cc-pVTZ calculations, with subsequent study using topological analysis of electron localization function (ELF). The reorganization of the chemical bonds during intramolecular electron transfer in (QTTFQ)(?-) and (DBTTFI)(?-) has been analyzed using bonding evolution theory (BET). The reaction path has been simulated by the IRC procedure, and the evolution of valence basins has been described using catastrophe theory. The simple mechanisms: (QTTFQ)(?-): η-1-3-CC(+)-0: (-?)(QTTFQ) and (DBTTFI)(?-): η-1-3-[F](4)[F(+)](4)-0: (-?)(DBTTFI), each consisting of three steps, have been observed. Two cusp or 4-fold catastrophes occur immediately after the TS. Our study shows that potential future microelectronic devices, constructed on the basis of the (QTTFQ)(?-) and (DBTTFI)(?-) systems, should exploit the properties of the C═C bond. 相似文献
88.
Stariat J Sesták V Vávrová K Nobilis M Kollárová Z Klimeš J Kalinowski DS Richardson DR Kovaříková P 《Analytical and bioanalytical chemistry》2012,403(1):309-321
The iron chelator, 2-benzoylpyridine-4-ethyl-3-thiosemicarbazone (Bp4eT), was identified as a lead compound of the 2-benzoylpyridine
thiosemicarbazone series, which were designed as potential anti-cancer agents. This ligand has been shown to possess potent
anti-proliferative activity with a highly selective mechanism of action. However, further progress in the development of this
compound requires data regarding its metabolism in mammals. The aim of this study was to identify the main in vitro and in
vivo phase I metabolites of Bp4eT using liquid chromatography tandem mass spectrometry (LC-MS/MS). Two metabolites were detected
after incubation of this drug with rat and human liver microsomal fractions. Based on LC-MSn analysis, the metabolites were demonstrated to be 2-benzoylpyridine-4-ethyl-3-semicarbazone and N
3-ethyl-N
1-[phenyl(pyridin-2-yl)methylene]formamidrazone, with both resulting from the oxidation of the thiocarbonyl group. The identity
of these metabolites was further shown by LC-MS/MS analysis of these latter compounds which were prepared by oxidation of
Bp4eT with hydrogen peroxide and their structures confirmed by nuclear magnetic resonance and infrared spectra. Both the semicarbazone
and the amidrazone metabolites were detected in plasma, urine, and feces after i.v. administration of Bp4eT to rats. In addition,
another metabolite that could correspond to hydroxylated amidrazone was found in vivo. Thus, oxidative pathways play a major
role in the phase I metabolism of this promising anti-tumor agent. The outcomes of this study will be further utilized for:
(1) the development and validation of the analytical method for the quantification of Bp4eT and its metabolites in biological
materials; (2) to design pharmacokinetic experiments; and to (3) evaluate the potential contribution of the individual metabolites
to the pharmacodynamics/toxico-dynamics of this novel anti-proliferative agent. 相似文献
89.
90.
Patricia E. Simmons Tom Albers Debbie Barco Michelle Barker Ron Beer Cassandra Belton Betty Burris Hal Donovan Pili Dressel Ron Giesler Terri Gipson Neal Gleditsch Marian Heimbouch Lea Heintz Linda Kalinowski Kathy Ketterer Kit Klein Lebee Meehan Diane Miller Donna Northcott Barb Pollman Tom Potter Jeffrey Powell Dan Prater Doug Raney Chris Roman Beryl Rosenthal Brian Schaffer Joe Seidler Laura Sturmfels Mary Stewart Carey Tisdal Carol Valenta Suzanne Walton Ralph Wilke 《School science and mathematics》1998,98(7):354-356