全文获取类型
收费全文 | 5977篇 |
免费 | 154篇 |
国内免费 | 46篇 |
专业分类
化学 | 3734篇 |
晶体学 | 35篇 |
力学 | 209篇 |
数学 | 1274篇 |
物理学 | 925篇 |
出版年
2022年 | 46篇 |
2021年 | 58篇 |
2020年 | 65篇 |
2019年 | 67篇 |
2018年 | 58篇 |
2017年 | 49篇 |
2016年 | 97篇 |
2015年 | 116篇 |
2014年 | 135篇 |
2013年 | 310篇 |
2012年 | 295篇 |
2011年 | 328篇 |
2010年 | 222篇 |
2009年 | 208篇 |
2008年 | 306篇 |
2007年 | 320篇 |
2006年 | 305篇 |
2005年 | 278篇 |
2004年 | 267篇 |
2003年 | 218篇 |
2002年 | 208篇 |
2001年 | 98篇 |
2000年 | 92篇 |
1999年 | 99篇 |
1998年 | 73篇 |
1997年 | 66篇 |
1996年 | 91篇 |
1995年 | 67篇 |
1994年 | 74篇 |
1993年 | 82篇 |
1992年 | 65篇 |
1991年 | 44篇 |
1990年 | 75篇 |
1989年 | 59篇 |
1988年 | 48篇 |
1987年 | 55篇 |
1986年 | 47篇 |
1985年 | 68篇 |
1984年 | 81篇 |
1983年 | 53篇 |
1982年 | 78篇 |
1981年 | 80篇 |
1980年 | 95篇 |
1979年 | 75篇 |
1978年 | 80篇 |
1977年 | 76篇 |
1976年 | 72篇 |
1975年 | 52篇 |
1974年 | 38篇 |
1973年 | 58篇 |
排序方式: 共有6177条查询结果,搜索用时 46 毫秒
41.
Michel Crouzeix 《Numerical Algorithms》2003,33(1-4):193-201
We consider the lumped mass method with piecewise linear finite elements in two dimensions. When the triangulation is of Delaunay type it is known that the discrete scheme satisfies a maximum principle. In this work we pursue the analysis and prove that the discrete semi-group is l
p
contractive in a sector, which implies smoothing effects and provide some resolvent estimates. 相似文献
42.
Michel Vasquez 《Journal of Heuristics》2004,10(4):407-413
For the Queens_n
2 graph coloring problems no chromatic numbers are available for n > 9 except where n is not a multiple of 2 or 3. In this paper we propose an exact algorithm that takes advantage of the particular structure of these graphs. The algorithm works on the independent sets of the graph rather than on the vertices to be colored. It combines branch and bound, for independent set assignment, with a clique based filtering procedure. A first experimentation of this approach provided the coloring number values ranging for n = 10 to n = 14. 相似文献
43.
In this paper we provide an error bound estimate and an implicit multifunction theorem in terms of smooth subdifferentials and abstract subdifferentials. Then, we derive a subdifferential calculus and Fritz–John type necessary optimality conditions for constrained minimization problems. 相似文献
44.
We study the asymptotic behaviour of the solution of elliptic problems with periodic data when the size of the domain on which the problem is set becomes unbounded. To cite this article: M. Chipot, Y. Xie, C. R. Acad. Sci. Paris, Ser. I 339 (2004). 相似文献
45.
When trains of impulse controls are present on the right-hand side of a system of ordinary differential equations, the solution
is no longer smooth and contains jumps which can accumulate at several points in the time interval. In technological and physical
systems the sum of the absolute value of all the impulses is finite and hence the total variation of the solution is finite.
So the solution at best belongs to the space BV of vector functions with bounded variation. Unless variable node methods are
used, the loss of smoothness of the solution would a priori make higher-order methods over a fixed mesh inactractive. Indeed
in general the order of -convergence is and the nodal rate is . However in the linear case -convergence rate remains but the nodal rate can go up to by using one-step or multistep scheme with a nodal rate up to when the solution belongs to . Proofs are given of error estimates and several numerical experiments confirm the optimality of the estimates.
Received March 15, 1996 / Revised version received January 3, 1997 相似文献
46.
Hans van den Berg Michel Mandjes Rudesindo Núñez-Queija 《Operations Research Letters》2007,35(3):297-307
We study a processor-sharing model in which users choose between a high- and a low-priority service, based on their utility functions and prices charged by the service provider. The latter aims at revenue maximization. The model is motivated by file transmissions in data networks with distributed congestion control. 相似文献
47.
We prove embedding results of weighted W1,p(RN) spaces of radially symmetric functions. The results then are used to obtain ground and bound state solutions of quasilinear equations with unbounded or decaying radial potentials. 相似文献
48.
The kinetics and the equilibrium constant of the chlorine transfer reaction between monochloramine NH2Cl and the amines: C2H5NH2, (CH3)2CHNH2, (CH3)2NH, and (C2H5)2NH are investigated by spectrophotometry in aqueous medium at 25°C, in the pH range from 8 to 13 and for an ionic strength equal to 1.03 ± 0.05M. For a concentration of total ammonia equal to 1M, the observed rate constant is pH independent below 8 and above 12.8 and reaches a maximum located between the pKas of NH4+ and RR'NH2+. From these results and those obtained earlier for NH2Cl and CH3NH2, the reaction is shown to involve an interaction between neutral molecules NH2Cl and RR'NH, subject to general acid catalysis. The ability of an interaction corresponding to a specific catalysis and involving NH3Cl+ and RR'NH rather than NH2Cl and RR'NH2+ is also discussed. The activation parameters are given for each reaction. 相似文献
49.
The first object of this paper is to introduce a new evolution equation for the characteristic function of the boundary Γ
of a Lipschitzian domain Ω in the N-dimensional Euclidean space under the influence of a smooth time-dependent velocity field. The originality of this equation is that the evolution takes place in an Lp-space with respect to the (N − 1)-Hausdorff measure. A second more speculative objective is to discuss how that equation can be relaxed to rougher velocity
fields via some weak formulation. A candidate is presented and some of the technical difficulties and open issues are discussed.
Continuity results in several metric topologies are also presented. The paper also specializes the results on the evolution
of the oriented distance function to initial sets with zero N-dimensional Lebesgue measure. 相似文献
50.