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981.
982.
983.
SHEN Wen-Jie YAN Shi-Run ZHOU Jing-Lai ZHANG Bi-JiangInstitute of Coal Chemistry Academia Sinica Taiyuan Shanxi 《天然气化学杂志》1995,(3)
The kinetics of the Fischer-Tropsch Synthesis reaction is studied in an internally recycled reactor (CSTR) over a commercial, precipitated Fe/Mn/K catalyst. Kinetic data are obtained with 1 47-4.04 H2/CO feed gas over a temperature range of 265-320℃, a pressure range of 1.0-2.6 MPa, and a space velocity range of 300-800 h-1 . The kinetic model which fits the experimental data well is the same as that of the intrinsic kinetics, i.e. -RH2 CO=kPH2PCO/(PCO bPH2O, where k is the kinetic constant for the rate-determining step and b is a function of temperature only. This model may be derived by assuming that the rate-determining step is the hydrogenation of adsorbed CO according to the enol mechanism. It is found that the CO usage ratio is probably independent of synthesis gas conversion and total pressure, and the catalyst shows high water-gas-shift activity. 相似文献
984.
985.
Marc Küther 《Numerische Mathematik》2003,93(4):697-727
Summary. We introduce a new technique for proving a priori error estimates between the entropy weak solution of a scalar conservation
law and a finite–difference approximation calculated with the scheme of Engquist-Osher, Lax-Friedrichs, or Godunov. This technique
is a discrete counterpart of the duality technique introduced by Tadmor [SIAM J. Numer. Anal. 1991]. The error is related
to the consistency error of cell averages of the entropy weak solution. This consistency error can be estimated by exploiting
a regularity structure of the entropy weak solution. One ends up with optimal error estimates.
Received December 21, 2001 / Revised version received February 18, 2002 / Published online June 17, 2002 相似文献
986.
In this paper we propose a nonmonotone trust region method. Unlike traditional nonmonotone trust region method, the nonmonotone technique applied to our method is based on the nonmonotone line search technique proposed by Zhang and Hager [A nonmonotone line search technique and its application to unconstrained optimization, SIAM J. Optim. 14(4) (2004) 1043–1056] instead of that presented by Grippo et al. [A nonmonotone line search technique for Newton's method, SIAM J. Numer. Anal. 23(4) (1986) 707–716]. So the method requires nonincreasing of a special weighted average of the successive function values. Global and superlinear convergence of the method are proved under suitable conditions. Preliminary numerical results show that the method is efficient for unconstrained optimization problems. 相似文献
987.
988.
C. Léonard 《Probability Theory and Related Fields》1995,101(1):1-44
Summary We consider a dynamical interacting particle system whose empirical distribution tends to the solution of a spatially homogeneous Boltzmann type equation, as the number of particles tends to infinity. These laws of large numbers were proved for the Maxwellian molecules by H. Tanaka [Tal] and for the hard spheres by A.S. Sznitman [Szl]. In the present paper we investigate the corresponding large deviations: the large deviation upper bound is obtained and, using convex analysis, a non-variational formulation of the rate function is given. Our results hold for Maxwellian molecules with a cutoff potential and for hard spheres. 相似文献
989.
Summary. In this work we address the issue of integrating
symmetric Riccati and Lyapunov matrix differential equations. In
many cases -- typical in applications -- the solutions are positive
definite matrices. Our goal is to study when and how this property
is maintained for a numerically computed solution.
There are two classes of solution methods: direct and
indirect algorithms. The first class consists of the schemes
resulting from direct discretization of the equations. The second
class consists of algorithms which recover the solution by
exploiting some special formulae that these solutions are known to
satisfy.
We show first that using a direct algorithm -- a one-step scheme or
a strictly stable multistep scheme (explicit or implicit) -- limits
the order of the numerical method to one if we want to guarantee
that the computed solution stays positive definite. Then we show two
ways to obtain positive definite higher order approximations by
using indirect algorithms. The first is to apply a symplectic
integrator to an associated Hamiltonian system. The other uses
stepwise linearization.
Received April 21, 1993 相似文献
990.
Frédéric Haglund 《Mathematische Zeitschrift》2002,242(1):97-148
Résumé. Dans ce travail, nous introduisons une classe d'immeubles hyperboliques de dimension 2 à allure locale prescrite. Nous prouvons
l'existence et l'unicité de ces immeubles. Nous montrons que leur groupe d'automorphismes est transitif sur les chambres.
Ces résultats permettent d'identifier des immeubles hyperboliques construits par les diverses méthodes utilisées jusqu'ici:
“blueprints” de Ronan-Tits et immeubles de Kac-Moody, revêtements ramifiés d'immeubles euclidiens, polygones de groupes etc...
Nos méthodes s'appliquent en fait à des complexes polygonaux hyperboliques beaucoup plus généraux que les seuls immeubles.
Received: 3 April 2000; in final form: 25 September 2000 / Published online: 23 July 2001 相似文献