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281.
Drescher D Orts-Gil G Laube G Natte K Veh RW Österle W Kneipp J 《Analytical and bioanalytical chemistry》2011,400(5):1367-1373
Cell cultures form the basis of most biological assays conducted to assess the cytotoxicity of nanomaterials. Since the molecular environment of nanoparticles exerts influence on their physicochemical properties, it can have an impact on nanotoxicity. Here, toxicity of silica nanoparticles upon delivery by fluid-phase uptake is studied in a 3T3 fibroblast cell line. Based on XTT viability assay, cytotoxicity is shown to be a function of (1) particle concentration and (2) of fetal calf serum (FCS) content in the cell culture medium. Application of dynamic light scattering shows that both parameters affect particle agglomeration. The DLS experiments verify the stability of the nanoparticles in culture medium without FCS over a wide range of particle concentrations. The related toxicity can be mainly accounted for by single silica nanoparticles and small agglomerates. In contrast, agglomeration of silica nanoparticles in all FCS-containing media is observed, resulting in a decrease of the associated toxicity. This result has implications for the evaluation of the cytotoxic potential of silica nanoparticles and possibly also other nanomaterials in standard cell culture. 相似文献
282.
Trąbska J Wesełucha-Birczyńska A Zięba-Palus J Runge MT 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(4):824-830
This work aimed at characterization of a black layer covering a Bronze Age (period VI) pot surface. To solve research problems plane polarized light microscopy (PLM), scanning microscopy with X-ray microanalyser (SEM/EDS), Raman and FTIR microspectroscopies were applied. Observation of the black layer under the PLM suggests that we deal with an opaque, isotropic layer, purposely put on leather-hard, burnished surface of a pot. No traces of organic substances that might have modified a pot surface before painting were detected. The black layer coats the pot with a continuous 0.2-0.4 μm thick layer. The black layer must have been applied while warm or hot. It is recognized that the black layer is a true painting layer. Spectroscopic analyses (Raman and FTIR) point that birch tar or a birch-pine tar had been applied. Carbon black should be definitely excluded. The analyzed organic substance is structurally ordered in various degrees, due to varying temperature influence. Some Raman spectra reveal, in second-order region of the spectrum (>2000 cm(-1)), the graphite presence. Scarce points reveal the presence of inorganic admixtures: clay minerals, feldspars and quartz. The next question is: Is it an organic paint or a carbon-based, "mixed" paint? Inorganic admixtures are only casual. Relatively high concentration of alumina is expected to have appeared due to aluminum mobility in acidic environment and this was provided by organic tar/pitch substances. Phosphorus (usually with calcium) mostly concentrates together with clay minerals. Thus, hypothesis on bone powder or ash addition to tar/pitch should be excluded. Some elements may originate not only from inorganic substances but also from wood ashes. 相似文献
283.
The spectroscopic properties of series homodimmeric hemicyanine dyes based on (p-N,N-dimethylaminostyryl)benzothiazolium, (p-N,N-dimethylaminostyryl)benzoxazolium, (p-N,N-dimethylaminostyryl)-2,3,3-trimethyl-3H-indolium residues were determined. The absorption and fluorescence spectra of the dyes under study were measured in different polarity solvents at room temperature. On the basis of the solvatochromic behavior the ground state (μg) and excited state (μe) dipole moments of bis-(N,N-dimethylaminostyryl) derivatives were evaluated. The dipole moments (μg and μe) were estimated from solvatochromic shifts of absorption and fluorescence spectra as function of dielectric constant (ε) and refractive index (n) of applied solvents. The absorption and fluorescence spectra are only slightly affected by the solvent polarity. The analysis of solvatochromic behavior of the fluorescence spectra as a function of Δf (ε, n) revealed that the emission occurs from a high polarity excited state. The large dipole moment changes along with the red-shifted fluorescence, as the solvent polarity is increased, demonstrates the formation of an intramolecular charge transfer state (ICT). Six bichromophoric hemicyanine dyes, possessing benzothiazole, benzoxazole or indolinium group linked by 5 or 10 methylene groups were evaluated as fluorescence probes applied for monitoring of the polymerization process. The study on the changes in fluorescence intensity and spectroscopic shift of studied compounds were carried out during photochemically initiated polymerization of 2-ethyl-2-(hydroxymethyl)-propane-1,3-diol triacrylate (TMPTA). 相似文献
284.
Andreas Sp?th Janina Gonschor Burkhard K?nig 《Monatshefte für Chemie / Chemical Monthly》2011,41(6):1289-1308
Abstract
The ammonium ion binding site of the enzyme glutaminase HisF inspired us to design guanidinium biscarboxylates as potential self-organized ionophores in molecular recognition. The syntheses of the title compounds based on aliphatic and aromatic building blocks, along with a general method for the preparation of δ-aminoethoxyacetic acids, are presented in this work. Investigation of the binding properties of the title compounds in dimethyl sulfoxide (DMSO) and methanol solution revealed no ammonium ion affinity, but interaction of the guanidinium moiety with acetate ions. 相似文献285.
Johannes Müller Janina Buck Prof. Dr. Andreas Hirsch 《European journal of organic chemistry》2023,26(9):e202201310
Within the scope of this paper, nine π-expanded mono-substituted 5,8,11,14,17-pentakis-(tert-butyl)-hexa-peri-hexabenzocoronenes (HBC) are introduced. 2-Iodo-5,8,11,14,17-pentakis-(tert-butyl)-hexa-peri-hexabenzocoronene served as precursor and was reacted with ethynyltrimethylsilane in a Sonogashira coupling reaction. The acetylene unit is used as a linker and can undergo another Sonogashira coupling reaction combining different phenyl coupling partners with the HBC core. The electron-withdrawing groups such as nitrile, pyridine and carbonyl species (aldehyde, methylester, carboxylic acid) as well as the three quinoxaline based species (diphenylquinoxaline, dibenzo[a,c]phenazine, phenanthro[4’,5’-a,b,c]phenazine) serve as substitution moieties. Their influence on the optoelectronic properties were investigated by UV/Vis absorption spectroscopy demonstrating a maximum redshift of 7 nm compared to starting compound 2-Iodo-5,8,11,14,17-pentakis-(tert-butyl) HBC. As for the phenanthro[4’,5’-a,b,c]phenazine substituted HBC a dramatic decrease in the intensity of the absorption of the UV/Vis spectrum was observed. The fluorescence spectroscopy pointed out that the dibenzo[a,c]phenazine and phenanthro[4’,5’-a,b,c]phenazine substitution changed the spectra to one broad peak departing from the characteristic HBC-like emission pattern. 相似文献
286.
Archiv der Mathematik - In this paper we give necessary and sufficient conditions for a functor to be representable in a strongly generated triangulated category which has a linear action by a... 相似文献
287.
Janina Kneipp Harald Kneipp Anpuchchelvi Rajadurai Robert W. Redmond Katrin Kneipp 《Journal of Raman spectroscopy : JRS》2009,40(1):1-5
During surface‐enhanced Raman scattering (SERS), molecules exhibit a significant increase in their Raman signals when attached, or in very close vicinity, to gold or silver nanostructures. This effect is exploited as the basis of a new class of optical labels. Here we demonstrate robust and sensitive SERS labels as probes for imaging live cells. These hybrid labels consist of gold nanoparticles with Rose Bengal or Crystal Violet attached as reporter molecules. These new labels are stable and nontoxic, do not suffer from photobleaching, and can be excited at any excitation wavelength, even in the near infrared. SERS labels can be detected and imaged through the specific Raman signatures of the reporters. In addition, surface‐enhanced Raman spectroscopy in the local optical fields of the gold nanoparticles also provides sensitive information on the immediate molecular environment of the label in the cell and allows imaging of the native constituents of the cell. This is demonstrated by images based on a characteristic Raman line of the reporter as well as by displaying lipids based on the SERS signal of the C H deformation/bending modes at ∼1470 cm−1. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献