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981.
One of the classical problem in computational biology is the character compatibility problem or perfect phylogeny problem. A standard formulation of this problem in terms of two closely related questions is the following. Given a data set consisting
of a finite set X and a set
of partitions induced on X by a set of characters. Is
compatible, that is, does there exist an evolutionary tree that represents (in a well-defined sense) the data? If this is the case,
is this tree unique? A fundamental result in phylogenetics states that the answer to the former of the two questions is yes
precisely if the partition intersection graph
associated to
can be made chordal by obeying a certain rule.
The main insight from this paper is that the relation graph
associated to a set
of partitions may provide a key for deciding whether such a chordalization of
exists. To prove our results, we introduce an extension of the concept of the partition intersection graph associated to
using
.
Received August 27, 2004 相似文献
982.
983.
L. Dymiska A. Gagor M. Maczka Z. Wgliski J. Hanuza 《Journal of Raman spectroscopy : JRS》2010,41(9):1021-1029
The molecular structures and vibrational properties of 1H‐imidazo[4,5‐b]pyridine in its monomeric and dimeric forms are analyzed and compared to the experimental results derived from the X‐ray diffraction (XRD), infrared (IR), and Raman studies. The theoretical data are discussed on the basis of density functional theory (DFT) quantum chemical calculations using Lee–Yang–Parr correlation functional (B3LYP) and 6‐31G(d,p) basis. This compound crystallizes in orthorhombic structure, space group Pna21(C2v9) and Z = 4. The planar conformation of the skeleton and presence of the N H···N hydrogen bond was found to be characteristic for the studied system. The temperature dependence of IR and Raman modes was studied in the range 4–294 K and 8–295 K, respectively. The normal modes, which are unique for the imidazopyridine derivatives are identified. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
984.
Alexis Bohlin Fredrik Vestin Jeanine Bonamy Pierre Joubert Per‐Erik Bengtsson 《Journal of Raman spectroscopy : JRS》2010,41(8):875-881
Rotational coherent anti‐Stokes Raman spectroscopy (CARS) in fuel‐rich hydrocarbon flames, with a large content of hydrogen in the product gases (∼20%), has in previous work shown that evaluated temperatures are raised several tens of Kelvin by taking newly derived N2 H2 Raman line widths into account. To validate these results, in this work calibrated temperature measurements at around 300, 500 and 700 K were performed in a cell with binary gas mixtures of nitrogen and hydrogen. The temperature evaluation was made with respect to Raman line widths either from self‐broadened nitrogen only, N2 N2 [energy‐corrected‐sudden (ECS)], or by also taking nitrogen broadened by hydrogen, N2 H2 [Robert–Bonamy (RB)], Raman line widths into account. With increased amount of hydrogen in the cell at constant temperature, the evaluated CARS temperatures were clearly lowered with the use of Raman line widths from self‐broadened nitrogen only, and the case with inclusion of N2 H2 Raman line widths was more successful. The difference in evaluated temperatures between the two different sets increases approximately linearly, reaching 20 K (at T ∼ 300 K), 43 K (at T = 500 K) and 61 K (at T = 700 K) at the highest hydrogen concentration (90%). The results from this work further emphasize the importance of using adequate Raman line widths for accurate rotational CARS thermometry. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
985.
In this article, we generalize a recently proposed method to obtain an exact general solution for the classical Susceptible, Infected, Recovered and Susceptible (SIRS) epidemic mathematical model. This generalization is based upon the nonlinear coupling of two frequencies in an infinite modal series solution. It is shown that these series provide a nonstandard approach in order to obtain an accurate analytical solution for the classical SIRS epidemic model. Numerical results of the SIRS epidemic model for real and complex frequencies are included in order to test the validity and reliability of the method. This method could be applied to a wide class of models in physics, chemistry or engineering. 相似文献
986.
Herein we develop a psychophysical model of decision making based on the difference between objective clock time and the human brain’s perception of time. In this model the utility function is given by the survival probability, which is shown to be a generalized hyperbolic distribution. The parameters of the utility function are fit to intertemporal choice model experimental data and decision making is determined to be a 1/f-noise process. 相似文献
987.
The causal approach to perturbative quantum field theory is presented in detail, which goes back to a seminal work by Henri Epstein and Vladimir Jurko Glaser in 1973 [12]. Causal perturbation theory is a mathematically rigorous approach to renormalization theory, which makes it possible to put the theoretical setup of perturbative quantum field theory on a sound mathematical basis. Epstein and Glaser solved this problem for a special class of distributions, the time-ordered products, that fulfill a causality condition, which itself is a basic requirement in axiomatic quantum field theory. In their original work, Epstein and Glaser studied only theories involving scalar particles. In this review, the extension of the method to theories with higher spin, including gravity, is presented. Furthermore, specific examples are presented in order to highlight the technical differences between the causal method and other regularization methods, like, e.g. dimensional regularization. 相似文献
988.
989.
The main propose of this paper is to study the blow-up of solutions of an initial boundary value problem with a nonlocal boundary condition for a system of nonlinear singular viscoelastic equations. where the blow-up of solutions in finite time with nonpositive initial energy combined with a positive initial energy are shown. 相似文献
990.