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71.
Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) is rarely used for the analysis of small molecules (< 700 Da) because the low m/z signal is overwhelmed by a high background of matrix ions. We have developed a solution to this problem that employs a novel polymer composite which is formed by covalently cross-linking alpha-cyano-4-hydroxycinnamic acid (HCCA) to SU-8 photoresist via cationic photo-polymerization. Since the HCCA molecules are immobilized, background noise resulting from the matrix ions is significantly reduced or eliminated. Moreover, owing to the hydrophobic surface of the polymer film, the sample spots shrink during solvent evaporation and thus the analytes can be concentrated. As a result, this polymer composite improves detection sensitivity and extends the analyzable species to the low-mass region. The covalent incorporation of HCCA with SU-8 was validated with reflectance FTIR spectroscopy, and the polymer surface was characterized with scanning electron microscopy (SEM). Using MRFA, a small peptide as a standard, 8 mg of HCCA per mL of SU-8 photoresist was found to yield the highest sensitivity and the lowest background noise. Analytes such as peptides or small organic molecules were further examined on this composite surface and no analyte degradation was observed. In a trial of peptide mass fingerprinting of cytochrome c on the composite substrate, the inclusion of low m/z tryptic peptides in the database search dramatically improved the protein identification probability score. 相似文献
72.
Electroanalysis of Natural Compounds as Copper Chelating Agents for Alzheimer’s Disease Therapy 下载免费PDF全文
Vinci Wing Sze Hung Lucas Paines Bressan Kanghoon Seo Kagan Kerman 《Electroanalysis》2015,27(11):2670-2678
The development of therapeutic compounds that can attenuate the toxicity exerted by the accumulation of metal ions has been an area of intensive research in neurodegenerative diseases. In this report, an electrochemical method was developed to determine the Cu(II)‐chelating ability of polyphenols that were implicated in Alzheimer’s disease (AD). The results suggested the strength of flavonoids to chelate Cu(II) as epigallocatechin‐3‐gallate (EGCG)>resveratrol>clioquinol>baicalein~scyllo‐inositol. Furthermore, the number of hydroxyl groups was found to play a role to lower Cu(II) oxidation signal using differential pulse voltammetry. 相似文献
73.
Chen X Chan WY Wong PS Yeung HS Chan TW 《Journal of the American Society for Mass Spectrometry》2011,22(2):233-244
Peptides adducted with different divalent Group IIB metal ions (Zn2+, Cd2+, and Hg2+) were found to give very different ECD mass spectra. ECD of Zn2+ adducted peptides gave series of c-/z-type fragment ions with and without metal ions. ECD of Cd2+ and Hg2+ adducted model peptides gave mostly a-type fragment ions with M+• and fragment ions corresponding to losses of neutral side chain from M+•. No detectable a-ions could be observed in ECD spectra of Zn2+ adducted peptides. We rationalized the present findings by invoking both proton-electron recombination and metal-ion reduction
processes. As previously postulated, divalent metal-ions adducted peptides could adopt several forms, including (a) [M + Cat]2+, (b) [(M + Cat – H) + H]2+, and (c) [(M + Cat – 2H) + 2H]2+. The relative population of these precursor ions depends largely on the acidity of the metal–ion peptide complexes. Peptides
adducted with divalent metal-ions of small ionic radii (i.e., Zn2+) would form predominantly species (b) and (c); whereas peptides adducted with metal ions of larger ionic radii (i.e., Hg2+) would adopt predominantly species (a). Species (b) and (c) are believed to be essential for proton-electron recombination
process to give c-/z-type fragments via the labile ketylamino radical intermediates. Species (c) is particularly important for the formation of
non-metalated c-/z-type fragments. Without any mobile protons, species (a) are believed to undergo metal ion reduction and subsequently induce
spontaneous electron transfer from the peptide moiety to the charge-reduced metal ions. Depending on the exothermicity of
the electron transfer reaction, the peptide radical cations might be formed with substantial internal energy and might undergo
further dissociation to give structural related fragment ions. 相似文献
74.
A clickable, affinity-based probe (AfBP), which was modified from staurosporine (a natural product kinase inhibitor), has been synthesized and used in situ for activity-based proteome profiling of potential cellular targets of staurosporine in HepG2 cancer cells. 相似文献
75.
Ryu G Huang J Hofmann O Walshe CA Sze JY McClean GD Mosley A Rattle SJ deMello JC deMello AJ Bradley DD 《Lab on a chip》2011,11(9):1664-1670
We demonstrate a compact, low cost and practical fluorescence detection system for lab-on-a-chip applications. The system comprises a commercially available InGaN light emitting diode (501 nm) as light source, an organic or silicon photodiode detector, absorptive dye coated colour filters and linear and reflective polarisers. An injection moulded polystyrene microfluidic chip is used as the platform for fluorescence immunoassays for cardiac markers myoglobin and CK-MB. The optical limit of detection (LOD) is measured using a TransFluoSphere? suspension at 5.6 × 10(4) beads μl(-1) which can be equated to ~3 nM fluorescein equivalent concentration. The LOD for the human plasma immunoassays is measured as 1.5 ng ml(-1) for both myoglobin and CK-MB. 相似文献
76.
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78.
Wahl EH Fidric B Rella CW Koulikov S Kharlamov B Tan S Kachanov AA Richman BA Crosson ER Paldus BA Kalaskar S Bowling DR 《Isotopes in environmental and health studies》2006,42(1):21-35
Recent measurements of carbon isotopes in carbon dioxide using near-infrared, diode-laser-based cavity ring-down spectroscopy (CRDS) are presented. The CRDS system achieved good precision, often better than 0.2 per thousand, for 4% CO2 concentrations, and also achieved 0.15-0.25 per thousand precision in a 78 min measurement time with cryotrap-based pre-concentration of ambient CO2 concentrations (360 ppmv). These results were obtained with a CRDS system possessing a data rate of 40 ring-downs per second and a loss measurement of 4.0 x 10(-11) cm(-1) Hz(-1/2). Subsequently, the measurement time has been reduced to under 10 min. This standard of performance would enable a variety of high concentration (3-10%) isotopic measurements, such as medical human breath analysis or animal breath experiments. The extension of this ring-down to the 2 microm region would enable isotopic analysis at ambient concentrations, which, combined with the small size, robust design, and potential for frequent measurements at a remote site, make CRDS technology attractive for remote atmospheric measurement applications. 相似文献
79.
Chien-Yao Huang Jyh-Rou Sze Kuo-Cheng Huang Chao-Hui Kuo Shih-Feng Tseng Chang-Pin Chou 《Optical Review》2011,18(1):96-98
This paper presents a precision glass-molding process to fabricate planar-integrated micro-optical components (PIMOC) applied to a micro projection display system, optical interconnection system and optical storage system. The PIMOC was designed based on wave propagation theory, and fabricated using a glass molding process. Experimental results are discussed in this article. The experiment showed that the PIMOC fabricated in a vacuum environment meets the design value with precision glass-molding technology (PGMT) at a molding force of 2.75 kN, a molding temperature of 750 °C and a cooling rate of 49 °C/min. 相似文献
80.
Upon treatment with Fe(CO)5 in an aromatic hydrocarbon solvent aromatic acid chlorides gave an mixture of triarlmethane and tetraarylethane. The reaction may proceed via benzaldehyde and diarylmethanol intermediates. A free radical mechanism is proposed. 相似文献