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61.
Staes A Timmerman E Van Damme J Helsens K Vandekerckhove J Vollmer M Gevaert K 《Journal of separation science》2007,30(10):1468-1476
Microfluidic interfaces coupled to ESI mass spectrometers hold great potential for proteomics as they have been shown to augment the overall sensitivity of measurements and require only a minimum of operator manipulations as compared to conventional nano-LC interfaces. Here, we evaluated a new type of HPLC-Chips holding larger enrichment columns (thus an increased sample loading capacity) for gel-free proteome studies. A tryptic digest of a human T-cell proteome was fractionated by strong cation exchange chromatography and selected fractions were analyzed by MS/MS on an IT mass spectrometer using both the new HPLC-Chip as well as a conventional nano-LC-MS/MS interface. Our results indicate that the HPLC-Chip is capable of handling very complex peptide mixtures and, in fact, leads to the identification of more peptides and proteins as compared to when a conventional interface was used. The HPLC-Chip preferentially produced doubly charged tryptic peptides. We further show that MS/MS spectra of doubly charged tryptic peptide ions are more readily identified by MASCOT as compared to those from triply charged precursors and thus argue that besides the improved chromatographic conditions provided by the HPLC-Chip, its peptide charging profile might be a secondary factor leading to an increased proteome coverage. 相似文献
62.
63.
Carvalho AZ El-Attug MN da Silva JA Wolfs K D'Autry W Hoogmartens J Adams E Van Schepdael A 《Journal of separation science》2012,35(10-11):1336-1343
Sodium cysteamine phosphate is a prodrug derivative of cysteamine that can be used in cystinosis treatment. Although titrimetric assays are very well established and precise, iodimetric determination of sodium cysteamine phosphate requires considerably more carefulness and time from the analyst than usual. The possibility to assess sodium cysteamine phosphate by CE was evaluated by means of the quantification of its oxidation product, cystamine, which is a more suitable substance to be used as primary standard than sodium cysteamine phosphate. Apparently, this approach should be straightforward, but systematic differences between the results obtained with CE and titrimetric assays were noticed. MS and CE-MS were employed to aid in the investigation of the possible causes of imprecision of the sodium cysteamine phosphate titration and CE determination. For this purpose, a simple and inexpensive ESI source was constructed. It was observed that cystamine is not the final product of the cysteamine and/or sodium cysteamine phosphate iodine-oxidation and other species besides cystamine may be formed depending on the reaction conditions, which explains the difficulties observed in the sodium cysteamine phosphate quantification. 相似文献
64.
We report a non-linear blue shift of the zero-phonon emission line 5D0→7F0 of Eu3+-dopant in Eu3+-doped nano-glass-ceramics in magnetic field up to 50 T. The shift is significantly larger in nano-glass-ceramics compared to its precursor glass, suggesting that the nanoceraming of the precursor glass decreases the effective mass of the f-electrons bands of Eu3+ resulting in their enhanced magnetic confinement. Moreover, the non-linear character of the magnetic field dependence of this blue energy shift denotes a spatial confinement of f-electrons wave-functions of Eu3+ dopants in the PbF2-based nanocrystals of the nano-glass-ceramics where up to 90% of the dopants partition. The spatial confinement seems to be due to an admixture to the f-states of Eu3+ of its higher lying states of opposite parity which fall in the quantum well comprising of Eu3+-doped PbF2 crystalline nanoparticles embedded in the surrounding glass network. 相似文献
65.
We present a novel mechanism for generating both the baryon and dark matter densities of the Universe. A new Dirac fermion X carrying a conserved baryon number charge couples to the standard model quarks as well as a GeV-scale hidden sector. CP-violating decays of X, produced nonthermally in low-temperature reheating, sequester antibaryon number in the hidden sector, thereby leaving a baryon excess in the visible sector. The antibaryonic hidden states are stable dark matter. A spectacular signature of this mechanism is the baryon-destroying inelastic scattering of dark matter that can annihilate baryons at appreciable rates relevant for nucleon decay searches. 相似文献
66.
A first-order liquid-liquid phase transition in high-pressure hydrogen between molecular and atomic fluid phases has been predicted in computer simulations using ab initio molecular dynamics approaches. However, experiments indicate that molecular dissociation may occur through a continuous crossover rather than a first-order transition. Here we study the nature of molecular dissociation in fluid hydrogen using an alternative simulation technique in which electronic correlation is computed within quantum Monte Carlo methods, the so-called coupled electron-ion Monte Carlo method. We find no evidence for a first-order liquid-liquid phase transition. 相似文献
67.
Anderson AW Heptulla RA Driesen N Flanagan D Goldberg PA Jones TW Rife F Sarofin H Tamborlane W Sherwin R Gore JC 《Magnetic resonance imaging》2006,24(6):693-697
Functional magnetic resonance imaging (fMRI) was used to measure the effects of acute hypoglycemia caused by passive sensory stimulation on brain activation. Visual stimulation was used to generate blood-oxygen-level-dependent (BOLD) contrast, which was monitored during hyperinsulinemic hypoglycemic and euglycemic clamp studies. Hypoglycemia (50 +/- 1 mg glucose/dl) decreased the fMRI signal relative to euglycemia in 10 healthy human subjects: the fractional signal change was reduced by 28 +/- 12% (P < .05). These changes were reversed when euglycemia was restored. These data provide a basis of comparison for studies that quantify hypoglycemia-related changes in fMRI activity during cognitive tasks based on visual stimuli and demonstrate that variations in blood glucose levels may modulate BOLD signals in the healthy brain. 相似文献
68.
Byung-Yong Lee Kris Behler Murat Erdem Kurtoglu Meghan Ann Wynosky-Dolfi Richard F. Rest Yury Gogotsi 《Journal of nanoparticle research》2010,12(7):2511-2519
This article reports on titanium dioxide (TiO2)-coated nanofibers deposited on a filter surface by the electrospinning process. After depositing a micrometer-thick film
of polyamide 11 nanofibers on polypropylene fabric, TiO2 nanoparticles can be directly electrosprayed onto the nanofibers. X-ray diffraction and Raman spectroscopy showed minimal
change in the phase composition (anatase and rutile) and no change in the particle size of nanocrystalline TiO2 after coating. Scanning electron microscopy demonstrated that nanofibers were uniformly coated by titanium dioxide nanoparticles
without agglomeration. TiO2-coated filters showed excellent photocatalytic-bactericidal activity and photo-induced hydrophilicity. 相似文献
69.
Klaas W. Decoene Kamil Unal An Staes Olivier Zwaenepoel Jan Gettemans Kris Gevaert Johan M. Winne Annemieke Madder 《Chemical science》2022,13(18):5390
Labelling of tyrosine residues in peptides and proteins has been reported to selectively occur via a ‘tyrosine-click’ reaction with triazolinedione reagents (TAD). However, we here demonstrate that TAD reagents are actually not selective for tyrosine and that tryptophan residues are in fact also labelled with these reagents. This off-target labelling remained under the radar as it is challenging to detect these physiologically stable but thermally labile modifications with the commonly used HCD and CID MS/MS techniques. We show that selectivity of tryptophan over tyrosine can be achieved by lowering the pH of the aqueous buffer to effect selective Trp-labelling. Given the low relative abundance of tryptophan compared to tyrosine in natural proteins, this results in a new site-selective bioconjugation method that does not rely on enzymes nor unnatural amino acids and is demonstrated for peptides and recombinant proteins.A new strategy for selective tryptophan modification using triazolinedione (TAD) chemistry at pH 4 is shown on peptides and proteins. Additionally, off-target modification of tryptophan residues during the classical TAD-Y click reaction is uncovered. 相似文献
70.
Kris Matyjaszewski 《Journal of Polymer Science.Polymer Physics》1991,29(2):263-263