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41.
Organometallic compounds of general formula (RAsO)α are associated as trimers (R = C2H5, C3H7, C4H9) or even as a tetramer (R = CH3). Their physicochemical properties show them to be cyclic, the oxygen atoms being located in the bridging position. A “limited” electron delocalization may occur in these rings. 相似文献
42.
43.
Robert Durand Patrick Geneste Jean-Louis Oliv 《Magnetic resonance in chemistry : MRC》1983,21(5):301-304
The 13C NMR spectra were recorded for isoxazolines and isoxazolidines from 2,4,6-trimethylbenzonitrile oxide or α-phenyl-N-phenyl nitrone as dipolarophiles with the thiophene and benzo[b]thiophene S-oxide and S,S-dioxide series. The effects of the isoxazoline or isoxazolidine groups are not very different. Owing to the electronegativity of the oxygen atom, the main influence arises from the regioselectivity of the addition to the carbon atoms located at the α or β position from SO or SO2. 相似文献
44.
Rottereau M Gimel JC Nicolai T Durand D 《The European physical journal. E, Soft matter》2005,18(1):15-19
The influence of the Brownian step size in off-lattice Monte Carlo simulations of the aggregation and gelation of spheres
is studied. It is found that the kinetics are strongly influenced if the step size is larger than the mean smallest distance
between the sphere surfaces. The structure of the clusters and the gels is influenced, but only over length scales smaller
than the step size. Using large step sizes leads to a narrower size distribution of the clusters. Implications of the present
results are discussed for simulations reported in the literature in which the Brownian step size was chosen equal to the sphere
diameter. 相似文献
45.
López Fontán JL Costa J Ruso JM Prieto G Sarmiento F 《The European physical journal. E, Soft matter》2004,15(2):133-140
The application of a statistical method, the local polynomial regression method, (LPRM), based on a nonparametric estimation of the regression function to determine the critical micelle concentration (cmc) is presented. The method is extremely flexible because it does not impose any parametric model on the subjacent structure of the data but rather allows the data to speak for themselves. Good concordance of cmc values with those obtained by other methods was found for systems in which the variation of a measured physical property with concentration showed an abrupt change. When this variation was slow, discrepancies between the values obtained by LPRM and others methods were found.Received: 2 October 2003, Published online: 25 March 2004PACS:
02.50.-r Probability theory, stochastic processes, and statistics - 82.70.-y Disperse systems; complex fluids 相似文献
46.
[reaction: see text] Nitronic acids undergo an intramolecular 1,3-dipolar cycloaddition to unactivated double bonds, and the resulting isoxazolidines spontaneously evolve by an unprecedented in situ oxidative ring cleavage. The extension of this transformation to silyl nitronates results in a general diastereoselective construction of hydroxymethyl nitro functionalized tetrahydro-furans and -pyrrolidine having up to four consecutive stereogenic centers. 相似文献
47.
48.
E. Galichet F. Gulminelli D. C. R. Guinet M. F. Rivet J. F. Lecolley R. Bougault G. Auger B. Borderie B. Bouriquet A. Buta J. L. Charvet A. Chbihi J. Colin D. Cussol R. Dayras D. Durand J. D. Frankland B. Guiot S. Hudan P. Lautesse F. Lavaud N. Le Neindre O. Lopez L. Manduci J. Marie L. Nalpas J. Normand M. Pârlog P. Paw lowski E. Plagnol E. Rosato J. C. Steckmeyer B. Tamain A. Van Lauwe E. Vient C. Volant J. P. Wieleczko INDRA Collaboration 《The European Physical Journal A - Hadrons and Nuclei》2003,18(1):75-86
The transport properties of the 36Ar +58Ni system at
measured with the INDRA array, are studied within the BNV kinetic equation. A general protocol of comparison between the N-body experimental fragment information and the one-body distribution function is developed using global variables, with a special focus on charge density. This procedure avoids any definition of sources and any use of an afterburner in the simulation. We shall discuss the feasibility of such an approach and the distortions induced by the finite detection efficiency and the completeness requirements of the data selection. The sensitivity of the different global observables to the macroscopic parameters of the effective nuclear interaction will be studied in detail.Received: 21 January 2003, Published online: 5 August 2003PACS:
25.70.-z Low and intermediate energy heavy-ion reactions - 24.10.-i Nuclear reaction models and methodsN. Le Neindre: Permanent address: Institut de Physique Nuclaire, IN2P3-CNRS, F-91406 Orsay cedex, France. 相似文献
49.
G. Durand F. Spiegelmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):237-243
The stability against fragmentation and possible relaxation of the lowest excited states of the Na5F4 cluster (representative of cubic non stoechiometric clusters with an excess sodium atom, also called sodium-tail) is investigated
by means of one-electron pseudopotential calculations with particular reference to photoabsorption processes from the ground
state. Whereas the equilibrium configuration of the ground state has C3v symmetry, the doubly degenerate 12E excited state is affected by a conical intersection and a Jahn-Teller effect associated with the rotation of the sodium
tail around the C3-axis. This yields a “Mexican hat" topology for the lowest sheet with three equivalent Cs minima. Alternatively the 22A1 state has a minimum retaining the C3v symmetry. The dissociation paths of the cluster along the C3-axis into respectively Na4F4 + Na and Na4F3 + NaF are also investigated. Among the former paths, the excited states are found adiabatically stable with respect to the
products. However in the A1 symmetry, fragmentation into NaF exhibits an interesting avoided crossing between configurations correlated respectively
with Na4F3
+ + NaF- and Na4F3 + NaF. Such interaction, similar to the well-known charge exchange processes in elementary molecules might induce non adiabatic
predissociation of the 22A1 state. This mechanism is invoked to explain the differences between R2PI and depletion spectra, correlated with the dissociation
or relaxation of the excited states.
Received 24 March 2000 and Received in final form 11 July 2000 相似文献
50.
B. Tatischeff M. P. Comets Y. Le Bornec N. Willis B. Bonin J. C. Lugol B. Mayer Y. Terrien R. Beurtey A. Boudard J. M. Durand P. Fassnacht F. Hibou 《Zeitschrift für Physik A Hadrons and Nuclei》1987,328(2):147-149
Some evidence is presented for a narrow peak at 1969±2 MeV (FWHM=9±2 MeV) in the missing mass spectrum of the3He(p, d) reaction, with 3 standard deviations. The nature of this state, the mass of which is below the NN threshold, is discussed in connection with structures found in other experiments. 相似文献