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51.
Preparation of macroscopic amount of C60 clusters (fullerenes) by the iodine laser is reported. 相似文献
52.
We solve the previously derived Fokker-Planck equations of laser cooling for several cases: no diffusion processes included, the final stage when the distribution is narrow, and for an ansatz of Gaussian shape at all times. The results are particularized to a transition (j=0)→(j=1) and the numerical values for Mg atoms are used. The results are compared with earlier work on laser cooling and discussed. 相似文献
53.
Juha Knuutinen Reino Laatikainen Jaakko Paasivirta 《Magnetic resonance in chemistry : MRC》1980,14(5):360-365
The 13C NMR spectra of six hydroxybenzenes, all chlorobenzenes, all chlorophenols and eight chlorocatechols are measured and assigned. The additivity of the substituent effects and the usefulness of some corrective parameters are studied with regression analysis. The order of the chemical shifts is most efficiently predicted by the simplest substituent effect model, containing only the direct effects of the substituents, although the 95% confidence limits of the calculated shifts are as high as 5.6 ppm. If the chemical shifts need to be predicted within the measuring errors (approximately 0.05–0.10 ppm, in the present data), the number of necessary corrections is very impractical. The correction parameters are found to be independent of the solvent if no conformational effects are operative. These corrections, or the non-additivity parameters, are thus theoretically interesting. Approximate 1J(CH) couplings are also reported and the additivity of substitution effects on these parameters are discussed. 相似文献
54.
Juha?M.?Saarela Torbj?rn?L?fqvist Kerstin?Ramser Per?Gren Erik?Olson Jan?Niemi Mikael?Sj?dahl 《Central European Journal of Physics》2010,8(2):235-241
This study is focused on exploring the feasibility of an all-optic surface scanning method in determining the size and position
of a submerged, laser generated, optoacoustic (OA) source. The optoacoustic effect in this case was generated when the absorption
of a short electromagnetic pulse in matter caused a dielectric breakdown, a plasma emission flash and a subsequent acoustic
wave. In the experiment, a laser pulse with λ = 1064 nm and 12 ns pulse length was aimed at a volume of deionized water. When
the laser beam was focused by a f = 16 mm lens, a single dielectric breakdown spot occurred. When a f = 40 mm was used several breakdowns in a row were induced. The breakdowns were photographed using a double shutter camera.
The acoustic wave generated by the dielectric breakdowns were detected at a point on the water surface using a laser Doppler
vibrometer (LDV). First, the LDV signal was used to calculate the speed of sound with an accuracy of 10 m/s. Secondly, the
location and length of the dielectric breakdown was calculated with an accuracy of 1 mm. The calculated position matched the
breakdown location recorded by a camera. The results show that it is possible to use LDV surface measurements from a single
spot to determine both the position and length of the OA source as well as the speed of sound in the medium. Furthermore,
the LDV measurements also show a secondary peak that originates from the OA source. To unravel the origin and properties of
this interesting feature, further investigations are necessary 相似文献
55.
Margarida Baía Farid Bozorgnia Léonard Monsaingeon Juha Videman 《Journal of Mathematical Analysis and Applications》2018,457(1):77-103
The objective of this work is to study a coupled system of degenerate and nonlinear partial differential equations governing the transport of reactive solutes in groundwater. We show that this system admits a unique weak solution provided the nonlinear adsorption isotherm associated with the reaction process satisfies certain physically reasonable structural conditions, by addressing a more general problem. In addition, we conclude, that the solute concentrations stay non-negative if the source term is componentwise non-negative and investigate numerically the finite speed of propagation of compactly supported initial concentrations, in a two-component test case. 相似文献
56.
We study the action of the so-called discrete maximal operator on Newtonian, Hölder and BMO spaces on metric measure spaces equipped with a doubling measure and a Poincaré inequality. The discrete maximal operator has better regularity properties than the standard Hardy-Littlewood maximal operator and hence is a more flexible tool in this context. 相似文献
57.
Pentti Haukkanen Pauliina Ilmonen Ayse Nalli Juha Sillanpää 《Linear and Multilinear Algebra》2013,61(5):599-616
A divisor d ∈ ?+ of n ∈ ?+ is said to be a unitary divisor of n if (d, n/d) = 1. In this article we examine the greatest common unitary divisor (GCUD) reciprocal least common unitary multiple (LCUM) matrices. At first we concentrate on the difficulty of the non-existence of the LCUM and we present three different ways to overcome this difficulty. After that we calculate the determinant of the three GCUD reciprocal LCUM matrices with respect to certain types of functions arising from the LCUM problematics. We also analyse these classes of functions, which may be referred to as unitary analogs of the class of semimultiplicative functions, and find their connections to rational arithmetical functions. Our study shows that it does make a difference how to extend the concept of LCUM. 相似文献
58.
We find numerically that in the limit of weak atom-atom interactions a Bose-Einstein condensate in an optical lattice may develop a pulsating dynamical instability in which the atoms nearly periodically form a peak in the occupation numbers of the lattice sites, and then return to the unstable initial state. Multiple peaks behaving similarly are also found. Simple arguments show that the pulsating instability is a remnant of integrability, and give a handle on the relevant physical scales. 相似文献
59.
We present a general and systematic electronic structure theory of the nuclear magnetic resonance shielding tensor and the associated chemical shift for paramagnetic atoms, molecules, and nonmetallic solids. The approach is for the first time rigorous for an arbitrary spin state as well as arbitrary spatial symmetry and is formulated without reference to spin susceptibility. The leading-order magnetic-field dependence of shielding is derived. The theory is demonstrated by first principles calculations of organometallic molecules. 相似文献
60.
Using large-scale atomistic simulations, we show that the macroscopic cratering behavior emerges for projectile impacts on Au at projectile sizes between 1000 and 10000 Au atoms at impact velocities comparable to typical meteoroid velocities. In this size regime, we detect a compression of material in Au nanoparticle impacts similar to that observed for hypervelocity macroscopic impacts. The simulated crater volumes agree with the values calculated using the macroscopic crater size scaling law, in spite of a downwards extrapolation over more than 15 orders of magnitude in terms of the impactor volume. The result demonstrates that atomistic simulations can be used as a tool to understand the strength properties of materials in cases where only continuum models have been possible before. 相似文献