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排序方式: 共有7076条查询结果,搜索用时 15 毫秒
31.
We study a variation of the knapsack problem in which each item has a profit, a weight and a penalty; the sum of profits of the selected items minus the largest penalty associated with the selected items must be maximized. We present an ILP formulation and an exact optimization algorithm. 相似文献
32.
A new microwave dielectric method for studying photoinitiated chain radical polymerization processes
Carlo Carlini Francesco Ciardelli Pier Angelo Rolla Elpidio Tombari 《Journal of Polymer Science.Polymer Physics》1987,25(6):1253-1261
Measurements of both real and imaginary parts of the dielectric constant at a fixed microwave frequency have been performed on n-butyl acrylate/poly(n-butyl acrylate) mixtures. The dielectric constant of the mixtures has been compared with that of neat n-butyl acrylate during UV photoinitiated polymerization. The values of the imaginary part of the dielectric constant thus obtained have allowed determination of the instantaneous monomer concentration and verified the kinetic equation for the photoinitiated polymerization process. The limits of validity of the method as well as its capability of providing detailed kinetic information are also discussed. 相似文献
33.
Alberto Parmeggiani 《Annali dell'Universita di Ferrara》2006,52(2):431-456
Abstract Some spectral properties of certain 2×2 globally elliptic systems of ordinary differential operators, a class of vector-valued
deformations of the classical harmonic oscillator here called noncommutative harmonic oscillators, will be described, with
special emphasis on the Poisson relation and clustering properties of the eigenvalues.
Keywords: Clustering theorems, Periodic trajectories, Poisson relations, Noncommutative harmonic oscillators 相似文献
34.
Online weighted flow time and deadline scheduling 总被引:1,自引:0,他引:1
Luca Becchetti Stefano Leonardi Alberto Marchetti-Spaccamela Kirk Pruhs 《Journal of Discrete Algorithms》2006,4(3):339
In this paper we study some aspects of weighted flow time. We first show that the online algorithm Highest Density First is an O(1)-speed O(1)-approximation algorithm for P|ri,pmtn|∑wiFi. We then consider a related Deadline Scheduling Problem that involves minimizing the weight of the jobs unfinished by some unknown deadline D on a uniprocessor. We show that any c-competitive online algorithm for weighted flow time must also be c-competitive for deadline scheduling. We then give an O(1)-competitive algorithm for deadline scheduling. 相似文献
35.
Alberto Caprara Andrea Lodi Silvano Martello Michele Monaci 《Discrete Optimization》2006,3(4):317-326
We address the problem of packing a given set of rectangles into the minimum size square. We consider three versions of the problem, arising when the rectangles (i) are squares; (ii) have a fixed orientation; (iii) can be rotated by 90. For each case we study lower bounds, and analyze their worst-case performance ratio. In addition, we evaluate through computational experiments their average performance on instances from the literature. 相似文献
36.
37.
Here we prove that every compact differential manifold has a smooth algebraic model defined over Q. In dimension 2 we find an algebraic model (may be singular) defined over Q and birational over Q to the projective plane. 相似文献
38.
Alberto Gambi 《Journal of Molecular Spectroscopy》2002,216(2):508-514
The anharmonic force field of difluoromethanimine, F2C NH, has been reinvestigated theoretically using a coupled-cluster singles and doubles approach, augmented for structural optimization and harmonic force field by a contribution of connected triple excitations, CCSD(T). The cubic and quartic force constants have been obtained by numerical derivatives computed from analytical quadratic force constants calculated by second-order Møller-Plesset perturbation theory, MP2. The quadratic force constants and the equilibrium structure of F2C NH have then been scaled by a global least-squares fitting procedure to the spectroscopic data and parameters experimentally determined for this molecule. This force field, obtained in the internal coordinates space and therefore valid for all isotopomers of difluoromethanimine, yields a complete set of spectroscopic molecular constants providing a critical assessment of the experimental rotational and centrifugal distortion constants, fundamentals, overtones, and combination bands determined so far for F2C NH. In addition, the final force field can be used to make predictions of all important vibrational and rotational parameters which should be accurate and useful for new spectroscopic investigations. 相似文献
39.
Damien P. Foster Carlo Vanderzande Julia Yeomans 《Journal of statistical physics》1992,69(3-4):857-868
We study the zero-temperature behavior of several simple models for randomly self-interacting polymers in one and 1+1 dimensions. Results are based on exact enumeration and closed-form expressions. 相似文献
40.