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101.
102.
Jeffrey M. Spraggins Julie A. Lloyd Murray V. Johnston Julia Laskin Douglas P. Ridge 《Journal of the American Society for Mass Spectrometry》2009,20(9):1579-1592
The gas-phase fragmentation reactions of singly charged angiotensin II (AngII, DR+VYIHPF) and the ozonolysis products AngII+O (DR+VY*IHPF), AngII+3O (DR+VYIH*PF), and AngII+4O (DR+VY*IH*PF) were studied using SID FT-ICR mass spectrometry, RRKM modeling, and molecular dynamics. Oxidation of Tyr (AngII+O)
leads to a low-energy charge-remote selective fragmentation channel resulting in the b
4
+O fragment ion. Modification of His (AngII+3O and AngII+4O) leads to a series of new selective dissociation channels. For
AngII+3O and AngII+4O, the formation of [MH+3O]
+
−45 and [MH+3O]
+
−71 are driven by charge-remote processes while it is suggested that b
5
and [MH+3O]
+
−88 fragments are a result of charge-directed reactions. Energy-resolved SID experiments and RRKM modeling provide threshold
energies and activation entropies for the lowest energy fragmentation channel for each of the parent ions. Fragmentation of
the ozonolysis products was found to be controlled by entropic effects. Mechanisms are proposed for each of the new dissociation
pathways based on the energies and entropies of activation and parent ion conformations sampled using molecular dynamics. 相似文献
103.
Karyne M. Rogers Kerry Somerton Pamela Rogers Julie Cox 《Rapid communications in mass spectrometry : RCM》2010,24(16):2370-2374
Carbon isotope analyses (δ13C) of some New Zealand Manuka honeys show that they often fail the internationally recognised Association of Official Analytical Chemists sugar test (AOAC method 998.12) which detects added C4 sugar, although these honeys are from unadulterated sources. Failure of these high value products is detrimental to the New Zealand honey industry, not only in lost export revenue, but also in brand and market reputation damage. The standard AOAC test compares the carbon isotope value of the whole honey and corresponding protein isolated from the same honey. Differences between whole honey and protein δ13C values should not be greater than +1.0‰, as it indicates the possibility of adulteration with syrups or sugars from C4 plants such as high fructose corn syrup or cane sugar. We have determined that during the standard AOAC method, pollen and other insoluble components are isolated with the flocculated protein. These non‐protein components have isotope values which are considerably different from those of the pure protein, and can shift the apparent δ13C value of protein further away from the δ13C value of the whole honey, giving a false positive result for added C4 sugar. To eliminate a false positive C4 sugar test for Manuka honey, prior removal of pollen and other insoluble material from the honey is necessary to ensure that only the pure protein is isolated. This will enable a true comparison between whole honey and protein δ13C isotopes. Furthermore, we strongly suggest this modification to the AOAC method be universally adopted for all honey C4 sugar tests. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
104.
105.
106.
Erwann Guénin Marc Lecouvey Julie Hardouin 《Rapid communications in mass spectrometry : RCM》2009,23(9):1395-1400
1‐Hydroxymethylene‐1,1‐bisphosphonic acids (or bisphosphonates) are compounds that have interesting pharmacological applications. However, few mass spectrometric investigations have been carried out to determine their fragmentation patterns. Herein, we evaluated different matrices for the study by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) of the formation and fragmentation of the protonated, the cationized (MNa+ and MK+) and the deprotonated bisphosphonates. Some in‐source fragmentations were observed both in positive and in negative ion modes. The fragmentation patterns obtained in post‐source decay mode are also discussed. In contrast to previous electrospray ionization/multi‐stage mass spectrometry (ESI‐MSn) studies, some new fragmentation pathways were deduced and the effects of alkali ions on the fragmentation patterns were shown. The results summarized here completed the data previously recorded by ESI‐MSn and could be used for the characterization of bisphosphonates as alkali complexes in biological mixtures. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
107.
Jonathan P. Williams Julie Ann Lough Iain Campuzano Keith Richardson Peter J. Sadler 《Rapid communications in mass spectrometry : RCM》2009,23(22):3563-3569
We report the development of an enhanced algorithm for the calculation of collision cross‐sections in combination with Travelling‐Wave ion mobility mass spectrometry technology and its optimisation and evaluation through the analysis of an organoruthenium anticancer complex [(η6‐biphenyl)RuII(en)Cl]+. Excellent agreement was obtained between the experimentally determined and theoretically determined collision cross‐sections of the complex and its major product ion formed via collision‐induced dissociation. Collision cross‐sections were also experimentally determined for adducts of this ruthenium complex with the single‐stranded oligonucleotide hexamer d(CACGTG). Ion mobility tandem mass spectrometry measurements have allowed the binding sites for ruthenium on the oligonucleotide to be determined. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
108.
Isabelle Lefebvre 《Set-Valued Analysis》2001,9(3):273-288
In the first place, we present a quasi fixed-point theorem for a correspondence defined on some infinite-dimensional locally convex topological vector space such that some variables have open lower sections and the other ones are upper semicontinuous.In the second place, we propose a direct application of the quasi fixed-point result in an economic model. More precisely, we prove a nonemptiness result of the core of an exchange economy with asymmetric information, a continuum of states and a finite number of commodities. 相似文献
109.
Yue Xuan Andrew J. Creese Julie A. Horner Helen J. Cooper 《Rapid communications in mass spectrometry : RCM》2009,23(13):1963-1969
We have applied high‐field asymmetric waveform ion mobility spectrometry (FAIMS) to the analysis of the phosphopeptides APLpSFRGSLPKSYVK, APLSFRGpSLPKSYVK, and APLSFRGSLPKpSYVK. The peptides have identical amino acid sequences and differ only in the site of phosphorylation. The results show that FAIMS is capable of at least partially separating these species. Separation was confirmed by coupling FAIMS with high‐resolution electron transfer dissociation (ETD) mass spectrometry. Phosphorylation is retained on the ETD peptide fragments thereby allowing assignment of the site of the modification. Co‐eluting phosphopeptides which differ only in the site of modification are frequently observed in liquid chromatography/tandem mass spectrometry phosphoproteomics experiments, and therefore these proof‐of‐principle results have implications for the application of FAIMS in that field. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
110.