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91.
α-Arylation and Ring Expansion of Annulated Cyclobutanones: Stereoselective Synthesis of Functionalized Tetralones
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Dr. Stanley Chang Dr. Michael Holmes Dr. Jeffrey Mowat Michael Meanwell Prof. Robert Britton 《Angewandte Chemie (International ed. in English)》2017,56(3):748-752
α-Arylcyclobutanones display unique reactivity that makes them valuable synthetic intermediates and target molecules. We describe the preparation of α-aryl- and α-heteroarylcyclobutanones through a direct α-arylation reaction. Problematic fragmentations are avoided by the use of LiOtBu, which promotes a rapid but reversible self-aldol reaction that slowly releases the enolate required for α-arylation. We also demonstrate the ring expansion of α-arylcyclobutanones, a process that is highlighted in the stereoselective synthesis of 1-methoxy coniothyrinone D. 相似文献
92.
Morphine fluorescence spectra were obtained for morphine sulfate in distilled water, in KRP solution, and in KRP solutions with various concentrations of Ca++ and Mg++. No evidence of fluorescence shifting indicative of complex formation was observed. Similar solutions were used in a potentiometric study, and no evidence for complex formation was observed. 相似文献
93.
Nicholas Douglas Charles J. Neef Robert A. Rogers Jake A. Stanley Jacob Armitage Ben Martin Todd W. Hudnall William J. Brittain 《Journal of Physical Organic Chemistry》2013,26(8):688-695
The synthesis and reactivity of a tetrahydrochromeno[2,3‐b]indoles are reported. Evidence for reversible ring‐opening is based on H/D exchange and trapping experiments. These compounds readily undergo reaction with tetra‐n‐butylammonium cyanide. The cyanide reaction is 10–100× faster when the solution is irradiated with 350 nm light. Reaction with trimethylsilyl cyanide occurs only with UV irradiation demonstrating photoreactivity. The rate of tetrahydrochromeno[2,3‐b]indole ring‐opening is greater for (i) Me substitution at the hemiaminal carbon (compared to Ph), and (ii) substitution of fluorine at the 9‐position of the indole. Under acidic conditions, the ring‐opened indolium ion is observed. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
94.
95.
Benjamin Byerly Kevin Kuhn Lisa Colletti Lynn Foster Russ Keller Elmer Lujan Alex Martinez Donivan Porterfield Dan Schwartz Khal Spencer Floyd Stanley Mariam Thomas Lisa Townsend Ning Xu Lav Tandon 《Journal of Radioanalytical and Nuclear Chemistry》2017,312(1):95-104
Thorough physical and chemical characterization of plutonium–beryllium (PuBe) neutron sources is an important capability with applications ranging from material accountancy to nuclear forensics. Characterization of PuBe sources is not trivial owing to range of existing source designs and the need for adequate infrastructure to deal with radiation and protect the analyst. This study demonstrates a method for characterization of three PuBe sources that includes physical inspection and imaging followed by controlled disassembly and destructive analysis. 相似文献
96.
97.
W.-S. Jung F. Z. Wang S. Havlin T. Kaizoji H.-T. Moon H. E. Stanley 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(1):113-119
We investigate scaling and memory effects in return intervals between price volatilities above a certain threshold q for the
Japanese stock market using daily and intraday data sets. We find that the distribution of return intervals can be approximated
by a scaling function that depends only on the ratio between the return interval τ and its mean 〈τ〉. We also find memory effects
such that a large (or small) return interval follows a large (or small) interval by investigating the conditional distribution
and mean return interval. The results are similar to previous studies of other markets and indicate that similar statistical
features appear in different financial markets. We also compare our results between the period before and after the big crash
at the end of 1989. We find that scaling and memory effects of the return intervals show similar features although the statistical
properties of the returns are different. 相似文献
98.
H. E. Stanley P. Kumar G. Franzese L. Xu Z. Yan M. G. Mazza S. V. Buldyrev S.-H. Chen F. Mallamace 《The European physical journal. Special topics》2008,161(1):1-17
We present evidence from experiments and computer
simulations supporting the hypothesis that water displays
polyamorphism, i.e., water separates into two distinct liquid
phases. This concept of a new liquid-liquid phase transition is
finding application to other liquids as well as water, such as
silicon and silica. Specifically, we investigate, the relation
between changes in dynamic and thermodynamic anomalies arising from
the presence of the liquid-liquid critical point in (i) Two models
of water, TIP5P and ST2, which display a first order liquid-liquid
phase transition at low temperatures; (ii) the Jagla model, a
spherically symmetric two-scale potential known to possess a
liquid-liquid critical point, in which the competition between two
liquid structures is generated by repulsive and attractive ramp
interactions; and (iii) A Hamiltonian model of water where the idea
of two length/energy scales is built in. This model also displays a
first order liquid-liquid phase transition at low temperatures
besides the first order liquid-gas phase transition at high
temperatures. We find a correlation between the dynamic fragility
crossover and the locus of specific heat maxima CPmax
(“Widom line”) emanating from the critical point. Our findings are
consistent with a possible relation between the previously
hypothesised liquid-liquid phase transition and the transition in
the dynamics recently observed in neutron scattering experiments on
confined water. More generally, we argue that this connection
between CPmax and the dynamic crossover is not limited to
the case of water, a hydrogen bonded network liquid, but is a more
general feature of crossing the Widom line, an extension of the
first-order coexistence line in the supercritical region.
Dedicated to Armin Bunde on the occasion of his 60th birthday. 相似文献
99.
Kin ChinKazuo Eda Noriyuki Sotani M.Stanley Whittingham 《Journal of solid state chemistry》2002,164(1):81-87
Blue potassium molybdenum bronze, K0.28MoO3, was prepared by hydrothermal heating hydrogen molybdenum bronze in KCl solution at 431 K. Hydrated molybdenum bronze was found formed as an intermediate during the conversion from hydrogen molybdenum bronze to blue bronze. The hydrothermal method proved itself an easy and effective for synthesis of mixed-valence compounds. 相似文献
100.
Skibinsky A Buldyrev SV Scala A Havlin S Stanley HE 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》1999,60(3):2664-2669
We investigate the formation of a two-dimensional quasicrystal in a monodisperse system, using molecular dynamics simulations of hard-sphere particles interacting via a two-dimensional square-well potential. We find that more than one stable crystalline phase can form for certain values of the square-well parameters. Quenching the liquid phase at a very low temperature, we obtain an amorphous phase. By heating this amorphous phase, we obtain a quasicrystalline structure with fivefold symmetry. From estimations of the Helmholtz potentials of the stable crystalline phases and of the quasicrystal, we conclude that the observed quasicrystal phase can be the stable phase in a specific range of temperatures. 相似文献