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201.
This paper deals with the periodic solutions of the Cauchy problem to the Burgers-Hopf equation containing small viscosity
term. We propose at first an explicit formula for the exact solution of the Cauchy problem and then we give an approximate
formula. We use CNN approach for constructing the approximate solution and we find precise estimates of the remainder term.
This work was supported by the NATO Grant ICS.NR.CLG 981757. 相似文献
202.
González S Petrović M Radetic M Jovancic P Ilic V Barceló D 《Rapid communications in mass spectrometry : RCM》2008,22(10):1445-1454
A method based on the application of ultra-performance liquid chromatography (UPLC) coupled to hybrid quadrupole-time-of-flight mass spectrometry (QqTOF-MS) with an electrospray (ESI) interface has been developed for the screening and confirmation of several anionic and non-ionic surfactants: linear alkylbenzenesulfonates (LAS), alkylsulfate (AS), alkylethersulfate (AES), dihexyl sulfosuccinate (DHSS), alcohol ethoxylates (AEOs), coconut diethanolamide (CDEA), nonylphenol ethoxylates (NPEOs), and their degradation products (nonylphenol carboxylate (NPEC), octylphenol carboxylate (OPEC), 4-nonylphenol (NP), 4-octylphenol (OP) and NPEO sulfate (NPEO-SO4). The developed methodology permits reliable quantification combined with a high accuracy confirmation based on the accurate mass of the (de)protonated molecules in the TOFMS mode. For further confirmation of the identity of the detected compounds the QqTOF mode was used. Accurate masses of product ions obtained by performing collision-induced dissociation (CID) of the (de)protonated molecules of parent compounds were matched with the ions obtained for a standard solution. The method was applied for the quantitative analysis and high accuracy confirmation of surfactants in complex mixtures in effluents from the textile industry. Positive identification of the target compounds was based on accurate mass measurement of the base peak, at least one product ion and the LC retention time of the analyte compared with that of a standard. The most frequently surfactants found in these textile effluents were NPEO and NPEO-SO4 in concentrations ranging from 0.93 to 5.68 mg/L for NPEO and 0.06 to 4.30 mg/L for NPEO-SO4. AEOs were also identified. 相似文献
203.
Petrov P Yuan J Yoncheva K Müller AH Tsvetanov CB 《The journal of physical chemistry. B》2008,112(30):8879-8883
A transition from spherical to wormlike micelles of a poly(ethylene oxide) 20- block-poly(propylene oxide) 70- block-poly(ethylene oxide) 20 triblock copolymer Pluronic P123 induced by solubilization of a tetrafuctional monomer, Pentaerythritol tetraacrylate (PETA), in aqueous media has been studied. The wormlike micelles shape was locked by UV cross-linking of PETA within the micelles resulting in stabilized polymeric micelles (SPMs). The stability of SPMs in a good solvent for both polyether blocks like THF, and upon dilution below the critical micelle concentration (CMC) of P123 in water was confirmed by dynamic light scattering (DLS) and scanning force microscopy (SFM). Formation of cadmium sulfide (CdS) nanoparticles within the wormlike SPMs was carried out via the reduction of Cd (2+) with NaS and analyzed by transmission electron microscopy (TEM) and UV-vis absorption measurements. A stable water-dispersible hybrid system consisting of CdS quantum dots embedded into the wormlike SPMs was obtained. 相似文献
204.
The synthesis of three novel dimethyl (2‐(4,4‐dimethyl‐2,5‐dioxoimidazolidin‐1‐ylamino)‐ 2‐oxoethylamino)methylphosphonate, dimethyl (1‐ (4,4‐dimethyl‐2,5‐dioxoimidazolidin‐1‐ylamino)‐4‐ methyl‐1‐oxopentan‐2‐ylamino)methylphosphonate, and dimethyl (1‐(4,4‐dimethyl‐2,5‐dioxoimidazolidin‐ 1‐ylamino)‐1‐oxo‐3‐phenylpropan‐2‐ylamino)methylphosphonate, respectively, is reported. The newly synthesized compounds were prepared via the Kabachnik–Fields reaction. Their structures have been characterized by elemental analysis, IR, and NMR (1H, 13C, and 31P) spectra. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:669–672, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20731 相似文献
205.
Petar T. Todorov Rosica N. Petrova Emilia D. Naydenova Boris L. Shivachev 《Central European Journal of Chemistry》2009,7(1):14-19
The crystal structures of 3-amino-cycloheptanespiro-4′-imidazolidine-2′,5′-dione (I) {systematic name: 3-amino-1,3-diazaspiro[4.6]
undecane-2,4-dione} and 3-amino-cyclooctanespiro-4′-imidazolidine-2′,5′-dione (II) {systematic name: 3-amino-1,3-diazaspiro[4.7]
dodecane-2,4-dione}, have been determined. In both compounds the polar hydantoin groups cause molecules to aggregate via N-H...O
and N-H...N interactions, forming a layer structure, in which the cycloalkane rings project outwards from the central, more
polar, region. The observed molecular structure is compared with that calculated by density functional theory methods.
相似文献
206.
From a synthetic perspective, divergent dendrimer syntheses are often presented as idealized hyperbranched growth processes leading to perfect dendritic structures. Experimentally it has been found that in addition to ideal structures, varying amounts of structural errors are produced at each growth stage (generation). These defects (mutants) are created as a function of processing conditions and generation specific steric effects. This investigation focused on the divergent synthesis of Starburstr̀ polyamidoamine dendrimers** and the use of electrospray mass spectroscopy for appraising ideal structure/defect ratios as a function of generation. With this methodology, initial defect types and so called “defect propagation chains” have been identified and characterized. These hyperbranched mutation (defect) patterns provide ample evidence for the “genealogically directed” character of this divergent polymerization strategy. 相似文献