全文获取类型
收费全文 | 14769篇 |
免费 | 2279篇 |
国内免费 | 952篇 |
专业分类
化学 | 2512篇 |
晶体学 | 85篇 |
力学 | 1291篇 |
综合类 | 309篇 |
数学 | 8635篇 |
物理学 | 5168篇 |
出版年
2024年 | 15篇 |
2023年 | 124篇 |
2022年 | 298篇 |
2021年 | 412篇 |
2020年 | 386篇 |
2019年 | 436篇 |
2018年 | 399篇 |
2017年 | 565篇 |
2016年 | 632篇 |
2015年 | 471篇 |
2014年 | 769篇 |
2013年 | 1278篇 |
2012年 | 819篇 |
2011年 | 904篇 |
2010年 | 810篇 |
2009年 | 902篇 |
2008年 | 958篇 |
2007年 | 914篇 |
2006年 | 824篇 |
2005年 | 735篇 |
2004年 | 605篇 |
2003年 | 662篇 |
2002年 | 582篇 |
2001年 | 453篇 |
2000年 | 416篇 |
1999年 | 378篇 |
1998年 | 333篇 |
1997年 | 319篇 |
1996年 | 246篇 |
1995年 | 195篇 |
1994年 | 140篇 |
1993年 | 115篇 |
1992年 | 113篇 |
1991年 | 82篇 |
1990年 | 75篇 |
1989年 | 75篇 |
1988年 | 65篇 |
1987年 | 54篇 |
1986年 | 51篇 |
1985年 | 92篇 |
1984年 | 50篇 |
1983年 | 35篇 |
1982年 | 44篇 |
1981年 | 37篇 |
1980年 | 20篇 |
1979年 | 26篇 |
1978年 | 19篇 |
1977年 | 16篇 |
1976年 | 17篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
In this paper a new definition of a lattice valued intuitionistic fuzzy set (LIFS) is introduced, in an attempt to overcome
the disadvantages of earlier definitions. Some properties of this kind of fuzzy sets and their basic operations are given.
The theorem of synthesis is proved: For every two families of subsets of a set satisfying certain conditions, there is an
lattice valued intuitionistic fuzzy set for which these are families of level sets.
The research supported by Serbian Ministry of Science and Technology, Grant No. 1227. 相似文献
43.
44.
Hirofumi Tsumura. 《Mathematics of Computation》2004,73(245):251-258
In this paper, we give some evaluation formulas for Tornheim's type of alternating series by an elementary and combinatorial calculation of the uniformly convergent series. Indeed, we list several formulas for them by means of Riemann's zeta values at positive integers.
45.
In this paper, we exhibit a unified treatment of the mixed initial boundary value problem for second order (in time) parabolic linear differential equations in Banach spaces, whose boundary conditions are of a dynamical nature. Results regarding existence, uniqueness, continuous dependence (on initial data) and regularity of classical and strict solutions are established. Moreover, several examples are given as samples for possible applications.
46.
Carl M. Bender 《Czechoslovak Journal of Physics》2004,54(1):13-28
The Hamiltonian H specifies the energy levels and the time evolution of a quantum theory. It is an axiom of quantum mechanics that H be Hermitian. The Hermiticity of H guarantees that the energy spectrum is real and that the time evolution is unitary (probability preserving). In this talk we investigate an alternative formulation of quantum mechanics in which the mathematical requirement of Hermiticity is replaced by the more physically transparent condition of space-time reflection (PT) symmetry. We show that if the PT symmetry of a Hamiltonian H is not broken, then the spectrum of H is real. Examples of PT-symmetric non-Hermitian Hamiltonians are H=p
2+ix
3 and H=p
2-x
4. The crucial question is whether PT-symmetric Hamiltonians specify physically acceptable quantum theories in which the norms of states are positive and the time evolution is unitary. The answer is that a Hamiltonian that has an unbroken PT symmetry also possesses a physical symmetry that we call C. Using C, we show how to construct an inner product whose associated norm is positive definite. The result is a new class of fully consistent complex quantum theories. Observables exhibit CPT symmetry, probabilities are positive, and the dynamics is governed by unitary time evolution. 相似文献
47.
This work is devoted to near-optimal controls of large-scale discrete-time nonlinear dynamic systems driven by Markov chains; the underlying problem is to minimize an expected cost function. Our main goal is to reduce the complexity of the underlying systems. To achieve this goal, discrete-time control models under singularly-perturbed Markov chains are introduced. Using a relaxed control representation, our effort is devoted to finding near-optimal controls. Lumping the states in each irreducible class into a single state gives rise to a limit system. Applying near-optimal controls of the limit system to the original system, near-optimal controls of the original system are derived. 相似文献
48.
吴臻 《数学物理学报(B辑英文版)》2004,24(1):91-99
The existence and uniqueness results of fully coupled forward-backward stochastic differential equations with stopping time (unbounded) is obtained. One kind of comparison theorem for this kind of equations is also proved. 相似文献
49.
In this paper, we suggest and analyze a new two-step predictor–corrector type iterative method free from second derivatives for solving nonlinear equations of the type f(x)=0. This new method includes the two-step Newton method as a special case. We prove that the new iterative method is of fourth-order. Several examples are given to illustrate the efficiency of this new method and its comparison with other iterative methods. This method can be considered as a significant improvement of the Newton method and its variant forms. 相似文献
50.
Piotr Biler 《Reports on Mathematical Physics》2003,52(2):205-225
We study asymptotic properties of solutions to an extension to arbitrary dimensions of the astrophysical model proposed by Chavanis et al. to explain phenomena of gravitational collapse in clouds of self-gravitating particles. In particular, we show that in the two-dimensional case the solutions can be continued to global ones, while in three space dimensions large data of negative energy blow up in a finite time. Relations between isothermal, Streater's energy-transport and the present models are also studied. 相似文献