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41.
We experimentally demonstrate field-free, three-dimensional alignment (FF3DA) of polyatomic asymmetric top molecules. We achieve FF3DA in sulfur dioxide gas using two time-delayed, orthogonally polarized, nonresonant, femtosecond laser pulses. Our method avoids the use of rotational revivals and is therefore more robust to temperature. The alignment is probed using time-delayed coincidence Coulomb explosion imaging. FF3DA will be important for all molecular imaging, dynamics, or spectroscopy experiments for which random alignment leads to a loss of information. 相似文献
42.
K. Lawniczak-Jablonska J.J. Jia L. Lin M.M. Grush T.A. Callcott A. Asfaw J.A. Carlisle L.J. Terminello F.J. Himpsel D.L. Ederer J.H. Underwood R.C.C. Perera 《Applied Physics A: Materials Science & Processing》1997,65(2):173-177
1-x MnxS (where 0.05<x<1) were measured as the energy of the exciting radiation was tuned across the S and Mn-L2,3 absorption edges of these compounds. Strong resonance peaks in Mn-L emission spectra and the systematic appearance of new
spectral features in S-L emission spectra were observed. Partial substitution of Zn by a magnetic Mn ion results in strong
hybridization of the Mn 3d orbitals with the sp band of the host semiconductor. A detailed study of resonant inelastic scattering
in the vicinity of the S and Mn-L2,3 absorption edges of these DMS is presented.
Received: 6 March 1997 相似文献
43.
Robert Underwood 《代数通讯》2013,41(11):3447-3462
44.
Lange PP Goossen LJ Podmore P Underwood T Sciammetta N 《Chemical communications (Cambridge, England)》2011,47(12):3628-3630
A practical protocol was developed that allows performing decarboxylative cross-coupling reactions in continuous flow reactors. Various biaryls were thus synthesized from aromatic carboxylic acids and aryl triflates using a Cu/Pd-catalyst system. 相似文献
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The alternating step generator is a well-known keystream generator consisting of two stop/go clocked LFSRs, LFSR1 and LFSR2, whose clocks are controlled by another LFSR, LFSR3, which is clocked regularly. A probabilistic analysis of this generator is conducted which shows that the posterior probabilites of individual bits of the first derivatives of the regularly clocked LFSR1 and LFSR2 sequences, when conditioned on a given segment of the first derivative of the keystream sequence, can be computed efficiently in a number of probabilistic models of interest. The expected values of these probabilities, for a random keystream sequence, are derived by an approximate theoretical analysis and are also verified by systematic computer experiments. It is pointed out that these posterior probabilities can be enhanced in a resynchronization scenario and thus used for a low-complexity fast correlation attack on the two LFSRs. More generally, it is argued that even without resynchronization these probabilities may be significantly different from one half for fast correlation attacks based on iterative decoding algorithms to be successful, although with incresead complexity. A related method for computing the posterior probabilities of individual bits of the LFSR3 sequence, when conditioned on both the keystream sequence and the LFSR1 and LFSR2 sequences, is also developed. As these posterior probabilities are much more different from one half, they can be used for a low-complexity fast correlation attack on LFSR3, provided that the initial states of LFSR1 and LFSR2 are previously reconstructed. 相似文献
48.
We demonstrate a method to directly measure the change in the spectrum of intermolecular solvent fluctuations as a function of time after electronic excitation of a solute, and this method is applied to the dye Coumarin 102 (C102) in acetonitrile. The complete intermolecular response is captured following resonant excitation with time domain third-order Raman spectroscopy. In a previous report, we introduced this method and used it to probe one point in the intermolecular response as a function of time after solute excitation (Underwood, D. F., Blank, D. A. J. Phys. Chem. A 2003, 107 (7), 956). Here we extend this approach to recover the change in the entire intermolecular response as a function of time. To our knowledge the results provide the first direct measurement of the difference in the equilibrated intermolecular response after excitation of a solute and its evolution during a dipolar solvation event. Excitation of C102 results in a significant increase in the solvent-solute interaction due to a large increase in the dipole moment. The observed change in the intermolecular response is consistent with a rapid change in local solvent density, with intermolecular kinetic energy transfer changing the response on longer time scales. Evolution of the response exhibits a strong frequency dependence and suggests changes over longer distances at longer delay times. The measured change in the spectrum of solvent fluctuations represents a direct experimental confirmation of the breakdown of linear response and confirms predictions from molecular dynamics simulations. 相似文献
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