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51.
This paper explores the provenance and content of a previously unknown personal letter by John Dalton (1766-1844), which is dated 12 April 1803. It relates to a startling breakthrough in Dalton's research, which pre-dates by five months the earliest date in his laboratory notebook, namely, 6 September 1803. The author acquired the letter about thirty years ago, and now offers it to the public. He makes no attempt to explain how it contributes to--or even changes--our understanding of Dalton, but leaves that privilege to Dalton scholars. 相似文献
52.
McGrath AJ Garrett GE Valgimigli L Pratt DA 《Journal of the American Chemical Society》2010,132(47):16759-16761
A persistent triptycenyl sulfenic acid is used as a model for cysteine-derived and other biologically relevant sulfenic acids in experiments which define their redox chemistry. EPR spectroscopy reveals that sulfinyl radicals are persistent and unreactive toward O(2), allowing the O-H bonding dissociation enthalpy (BDE) of the sulfenic acid to be readily determined by equilibration with TEMPO as 71.9 kcal/mol. The E° (RSO?/RSO(-)) and pK(a) of this sulfenic acid are also reported. 相似文献
53.
Frank J. Dinan Willis T. Schwartz Roger A. Wolfe Daniel S. Hojnicki Terry St. Clair J. Richard Pratt 《Journal of polymer science. Part A, Polymer chemistry》1992,30(1):111-118
Solution and solid-state proton decoupled 13C-NMR spectra were determined on two diimides derived from 4, 4′-oxydiphthalic anhydride. Comparison of the individual diimide spectra to that of a mixture of the two diimides indicates that ordering of these materials occurs in the solid state via charge transfer complex formation. A similar study was conducted using two isomeric dianhydrides, 4, 4′-isophthaloyldiphthalic anhydride (IDPA) and 4, 4′-terephthaloyldiphthalic anhydride (TDPA). The solution spectra of these compounds are similar and are those which would be expected for these compounds. However, their solid state spectra differ from each other. The solid-state spectrum of TDPA resembles its solution spectrum, whereas, that of IDPA differs greatly from its solution spectrum and indicates charge transfer complex formation occurs with this molecule. This difference is explained in terms of the stereochemistry of the two isomeric dianhydrides. 相似文献
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F.L. Pratt S.J. Blundell P.A. Pattenden W. Hayes K.H. Chow A.P. Monkman T. Ishiguro K. Ishida K. Nagamine 《Hyperfine Interactions》1997,106(1-4):33-38
We report studies of spin dynamics in the conducting polymers polyaniline and polypyrrole using both μ+SR and μ-SR techniques. These measurements reveal characteristic field dependences and cutoff frequencies for the muon spin relaxation
which can be related to the spin diffusion process. Clear evidence is seen for increased spin localisation at low temperatures
where a crossover occurs from two or three dimensional spin diffusion to a one dimensional diffusion regime.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
56.
A Scalable Biomimetic Synthesis of Resveratrol Dimers and Systematic Evaluation of their Antioxidant Activities 下载免费PDF全文
Bryan S. Matsuura Mitchell H. Keylor Bo Li YuXuan Lin Shelby Allison Prof. Dr. Derek A. Pratt Prof. Dr. Corey R. J. Stephenson 《Angewandte Chemie (International ed. in English)》2015,54(12):3754-3757
An efficient synthetic route to the resveratrol oligomers quadrangularin A and pallidol is reported. It features a scalable biomimetic oxidative dimerization that proceeds in excellent yield and with complete regioselectivity. A systematic evaluation of the natural products and their synthetic precursors as radical‐trapping antioxidants has revealed that, contrary to popular belief, this mode of action is unlikely to account for their observed biological activity. 相似文献
57.
Ian Pratt‐Hartmann 《Mathematical Logic Quarterly》2015,61(6):474-515
We consider the two‐variable fragment of first‐order logic with counting, subject to the stipulation that a single distinguished binary predicate be interpreted as an equivalence. We show that the satisfiability and finite satisfiability problems for this logic are both NExpTime ‐complete. We further show that the corresponding problems for two‐variable first‐order logic with counting and two equivalences are both undecidable. 相似文献
58.
Priya MH Pratt LR Paulaitis ME 《Langmuir : the ACS journal of surfaces and colloids》2011,27(22):13713-13718
We compare protein-protein and protein-polymer osmotic virial coefficients measured by static light scattering for aqueous solutions of lysozyme with low-molecular-weight, hydroxy-terminated (hPEG) and methyl-terminated (mPEG) poly(ethylene glycol) at two solution conditions: pH 7.0 and 0.01 M ionic strength, and pH 6.2 and 0.8 M ionic strength. We find that adding PEG to aqueous lysozyme solutions makes a net repulsive contribution to lysozyme-lysozyme interactions, independent of ionic strength and PEG end-group hydrophobicity. PEG end-group hydrophobicity has a profound effect on the magnitude of this contribution, however, at low ionic strength where mPEG-lysozyme attractive interactions become significant. The enhanced attractions promote mPEG-lysozyme preferential interactions at the expense of lysozyme self-interactions, which leads to lysozyme-lysozyme interactions that are more repulsive in the presence of mPEG. These preferential interactions also lead to the preferential exclusion of diffusable ions locally around the protein, which results in a pronounced ionic strength dependence of mPEG-mediated lysozyme-lysozyme interactions. 相似文献
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