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101.
102.
Identification of bioactive peptides in hypoallergenic infant milk formulas by capillary electrophoresis-mass spectrometry 总被引:1,自引:0,他引:1
Català-Clariana S Benavente F Giménez E Barbosa J Sanz-Nebot V 《Analytica chimica acta》2010,683(1):119-125
In this study, we use capillary electrophoresis-mass spectrometry (CE-MS) for the identification of bioactive peptides in hypoallergenic infant milk formulas (IF), which are complex bovine milk protein hydrolysates. A sample clean-up pretreatment with a citrate buffer containing dithiothreitol and urea followed by solid-phase extraction (SPE) with different reversed-phase commercial cartridges was investigated to achieve optimum detection sensitivity in CE-MS. SPE with C18, StrataX and Oasis HLB cartridges allowed detection of the largest number of low molecular mass components, but combination of C18 and StrataX results was enough to achieve an excellent coverage of the studied IF. The monoisotopic molecular mass values of the low molecular mass components obtained by capillary electrophoresis ion-trap mass spectrometry (CE-IT-MS) allowed the tentative identification of nine bioactive sequences. Only the identification of five of them could be confirmed when accurate mass measurements were performed by capillary electrophoresis time-of-flight mass spectrometry (CE-TOF-MS), namely LKP, IPY, ALPM, PGPIHN and VAGTWY, which were reported to present angiotensin-converting enzyme (ACE) inhibitory and antimicrobial activity (only VAGTWY). 相似文献
103.
González-Melchor M Mayoral E Velázquez ME Alejandre J 《The Journal of chemical physics》2006,125(22):224107
The electrostatic interactions in dissipative particle dynamics (DPD) simulations are calculated using the standard Ewald [Ann. Phys. 64, 253 (1921)] sum method. Charge distributions on DPD particles are included to prevent artificial ionic pair formation. This proposal is an alternative method to that introduced recently by Groot [J. Chem. Phys. 118, 11265 (2003)] where the electrostatic field was solved locally on a lattice. The Ewald method is applied to study a bulk electrolyte and polyelectrolyte-surfactant solutions. The structure of the fluid is analyzed through the radial distribution function between charged particles. The results are in good agreement with those reported by Groot for the same systems. We also calculated the radius of gyration of a polyelectrolyte in salt solution as a function of solution pH and degree of ionization of the chain. The radius of gyration increases with the net charge of the polymer in agreement with the trend found in static light scattering experiments of polystyrene sulfonate solutions. 相似文献
104.
Aguado E Longarte A Alejandro E Fernandez JA Castaño F 《The journal of physical chemistry. A》2006,110(18):6010-6015
The adiabatic ionization threshold (AIT) of trans- and gauche-benzocaine has been measured by zero electron kinetic energy-pulsed field ionization (ZEKE-PFI) spectroscopy to be 7.8412+/-0.0008 eV (lasers at 34,134.4 and 29,109.3 cm(-1)) and 7.8421+/-0.0004 eV (34,144.8+29105.7 cm(-1)), respectively. AITs computed at the B3LYP/AUG-cc-p-VDZ level for the two conformers are some approximately 2,500 cm(-1) lower than the experimental; in contrast their energy difference is very close. The trans-benzocaine cation ZEKE spectra has been recorded taking a number of S(1) intermediate vibronic states. The spectra provide an energy threshold for the appearance of intramolecular vibrational redistribution (IVR) around approximately 540 cm(-1) in the S(1) state. 相似文献
105.
Erland Bjrklund Fernando Maya Sren A. Bak Martin Hansen Jos Manuel Estela Víctor Cerd 《Microchemical Journal》2011,98(2):190-199
This paper explores the potential of applying reversed-phase sequential injection chromatography (SIC) to determine the anticoccidial agents Lasalocid and Toltrazuril in various matrices including ground water, pharmaceutical formulations and feed. SIC was performed by connecting a 25 × 4.6 mm monolithic C18 column to a 2 m long pathlength capillary flow cell, where the usage of a flow cell lowers the detection limit compared to a conventional short-distance flow cell, providing a simple detection system for these two compounds which are initially poorly UV absorbents.The proposed set-up provides a high injection throughput of 12 h− 1, as well as a limit of detection of 0.019 and 0.010 mg/L for Toltrazuril and Lasalocid, respectively. The repeatabilities obtained (n = 10) were lower than 2% and 4% for Toltrazuril and Lasalocid, respectively. 相似文献
106.
Estela Giménez Victòria Sanz-Nebot Andreas Rizzi 《Analytical and bioanalytical chemistry》2013,405(23):7307-7319
Glycan reductive isotope labeling (GRIL) using [12C]- and [13C]-coded aniline was used for relative quantitation of N-glycans. In a first step, the labeling method by reductive amination was optimized for this reagent. It could be demonstrated that selecting aniline as limiting reactant and using the reductant in excess is critical for achieving high derivatization yields (over 95 %) and good reproducibility (relative standard deviations ~1–5 % for major and ~5–10 % for minor N-glycans). In a second step, zwitterionic–hydrophilic interaction liquid chromatography in capillary columns coupled to electrospray mass spectrometry with time-of-flight analyzer (μZIC-HILIC-ESI-TOF-MS) was applied for the analysis of labeled N-glycans released from intact glycoproteins. Ovalbumin, bovine α1-acid-glycoprotein and bovine fetuin were used as test glycoproteins to establish and evaluate the methodology. Excellent separation of isomeric N-glycans and reproducible quantitation via the extracted ion chromatograms indicate a great potential of the proposed methodology for glycoproteomic analysis and for reliable relative quantitation of glycosylation variants in biological samples. 相似文献
107.
Dr. Andrew J. Eberhart Harry J. Shrives Estela Álvarez Dr. Amandine Carrër Yuntong Zhang David J. Procter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7428-7434
A sulfoxide‐directed, metal‐free ortho‐propargylation of aromatics and heteroaromatics exploits intermolecular delivery of a propargyl nucleophile to sulfur followed by an intramolecular relay to carbon. The operationally simple cross‐coupling procedure is general, regiospecific with regard to the propargyl nucleophile, and shows complete selectivity for products of ortho‐propargylation over allenylation. The use of secondary propargyl silanes allows metal‐free ortho‐coupling to form carbon–carbon bonds between aromatic and heteroaromatic rings and secondary propargylic centres. The ‘safety‐catch’ nature of the sulfoxide directing group is illustrated in a selective, iterative double cross‐coupling process. The products of propargylation are versatile intermediates and they have been readily converted into substituted benzothiophenes. 相似文献
108.
Improved spectrophotometric determination of paraquat in drinking waters exploiting a Multisyringe liquid core waveguide system 总被引:1,自引:0,他引:1
A novel Multisyringe flow injection analysis (MSFIA) system combined with a 200 cm long pathlength liquid core waveguide (LCW) has been developed enabling for the first time the sensitive spectrophotometric determination at μg L−1 levels of the herbicide paraquat (Pq2+) in drinking waters. The proposed system is a simple, economic and fast alternative for obtaining the first evidence of paraquat pollution prior the use of more complex instrumental techniques.The proposed methodology is based on the production of a blue free radical by reaction of Pq2+ with ascorbic acid (partially oxidized with potassium iodate) in basic medium. Limits of detection and quantification as low as 0.7 and 2.3 μg L−1, were obtained respectively. The working range is linear up to a concentration of 250 μg L−1 of Pq2+. The injection throughput of the proposed method is 34 h−1. The results obtained with the LCW are compared with those using a conventional 1 cm flow cell. The automation of standard addition procedures has been studied and implemented for samples causing matrix effects. Finally the proposed system has been applied to the determination of paraquat in drinking water samples. 相似文献
109.
Candel I Bernardos A Climent E Marcos MD Martínez-Máñez R Sancenón F Soto J Costero A Gil S Parra M 《Chemical communications (Cambridge, England)》2011,47(29):8313-8315
A hybrid nanoscopic capped mesoporous material, that is selectively opened in the presence of nerve agent simulants, has been prepared and used as a probe for the chromo-fluorogenic detection of these chemicals. 相似文献