全文获取类型
收费全文 | 16607篇 |
免费 | 2522篇 |
国内免费 | 2523篇 |
专业分类
化学 | 5463篇 |
晶体学 | 369篇 |
力学 | 4276篇 |
综合类 | 204篇 |
数学 | 5393篇 |
物理学 | 5947篇 |
出版年
2024年 | 46篇 |
2023年 | 200篇 |
2022年 | 419篇 |
2021年 | 481篇 |
2020年 | 537篇 |
2019年 | 429篇 |
2018年 | 352篇 |
2017年 | 595篇 |
2016年 | 671篇 |
2015年 | 514篇 |
2014年 | 790篇 |
2013年 | 1171篇 |
2012年 | 939篇 |
2011年 | 946篇 |
2010年 | 899篇 |
2009年 | 995篇 |
2008年 | 1045篇 |
2007年 | 1216篇 |
2006年 | 1022篇 |
2005年 | 1025篇 |
2004年 | 929篇 |
2003年 | 935篇 |
2002年 | 770篇 |
2001年 | 652篇 |
2000年 | 603篇 |
1999年 | 537篇 |
1998年 | 431篇 |
1997年 | 408篇 |
1996年 | 298篇 |
1995年 | 246篇 |
1994年 | 203篇 |
1993年 | 188篇 |
1992年 | 168篇 |
1991年 | 136篇 |
1990年 | 114篇 |
1989年 | 67篇 |
1988年 | 85篇 |
1987年 | 72篇 |
1986年 | 67篇 |
1985年 | 71篇 |
1984年 | 59篇 |
1983年 | 29篇 |
1982年 | 41篇 |
1981年 | 51篇 |
1980年 | 26篇 |
1979年 | 42篇 |
1978年 | 43篇 |
1977年 | 32篇 |
1976年 | 20篇 |
1971年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Linear complexity and linear complexity profile are important characteristics of a sequence for applications in cryptography
and Monte-Carlo methods.
The nonlinear congruential method is an attractive alternative to the classical linear congruential method for pseudorandom
number generation.
Recently, a weak lower bound on the linear complexity profile of a general nonlinear congruential pseudorandom number generator
was proven by Gutierrez, Shparlinski and the first author. For most nonlinear generators a much stronger lower bound is expected.
Here, we obtain a much stronger lower bound on the linear complexity profile of nonlinear congruential pseudorandom number
generators with Dickson polynomials. 相似文献
72.
《中国科学B辑(英文版)》2007,(6)
Five polymer bonded explosives (PBXs) with the base explosive ε-CL-20 (hexanitrohexaazaisowurtzi- tane), the most important high energy density compound (HEDC), and five polymer binders (Estane 5703, GAP, HTPB, PEG, and F2314) were constructed. Molecular dynamics (MD) method was employed to investigate their binding energies (Ebind), compatibility, safety, mechanical properties, and energetic properties. The information and rules were reported for choosing better binders and guiding formula- tion design of high energy density material (HEDM). According to the calculated binding energies, the ordering of compatibility and stability of the five PBXs was predicted as ε-CL-20/PEG > ε-CL-20/ Estane5703 ≈ε-CL-20/GAP > ε-CL-20/HTPB > ε-CL-20/F2314. By pair correlation function g(r) analyses, hydrogen bonds and vdw are found to be the main interactions between the two components. The elasticity and isotropy of PBXs based ε-CL-20 can be obviously improved more than pure ε-CL-20 crystal. It is not by changing the molecular structures of ε-CL-20 for each binder to affect the sensitivity. The safety and energetic properties of these PBXs are mainly influenced by the thermal capability (C°p) and density (ρ) of binders, respectively. 相似文献
73.
In this paper, we discuss the viscosity solutions of the weakly coupled systems of fully nonlinear second-order degenerate parabolic equations and their Cauchy-Dirichlet problem. We prove the existence, uniqueness and continuity of viscosity solution by combining Perron's method with the technique of coupled solutions. The results here generalize those in Proc. London Math. Soc. 63 (1991) 212-240 and Comm. Partial Differential Equations 16 (1991) 1095-1128. 相似文献
74.
The motion of a particle in the field of an electromagnetic monopole (in the Coulomb–Dirac field) perturbed by an axially symmetric potential after quantum averaging is described by an integrable system. Its Hamiltonian can be written in terms of the generators of an algebra with quadratic commutation relations. We construct the irreducible representations of this algebra in terms of second-order differential operators; we also construct its hypergeometric coherent states. We use these states in the first-order approximation with respect to the perturbing field to obtain the integral representation of the eigenfunctions of the original problem in terms of solutions of the model Heun-type second-order ordinary differential equation and present the asymptotic approximation of the corresponding eigenvalues. 相似文献
76.
本文研究了催化反应非线性奇摄动边值问题.利用微分不等式理论和方法,得到了问题的解的任意次近似渐近估计. 相似文献
77.
The sound field both in the loudspeaker box and in the room is calculated by an analytical solution of three-dimensional wave equation. It is shown in theory that the amplitude response in small rooms is affected by the following positions: driver position on the front panel of the box, box position in the room, absorption material position in the box and absorption material position on the interior walls of the room. Both our computer prediction and experiments prove that the optimum positions are beneficial to the amplitude response. 相似文献
78.
研究了应用于锂二次电池正极的新型高能量密度存贮材料Li(AlxCo1-x)O2 (x=01—05)的磁性.发现Al3+的掺杂可导致Co3+中d电子自旋态发生变化,即有部分d电子进入高自旋态.伴随Co3+中电子状态的改变,材料结构演化也发生了相应变化,表现为c/a比增大明显减缓,较好地解释了材料结构对Vegard定律的正偏离.这对材料的微观结构与性能设计具有重要意义.
关键词:
锂电池材料
Li(AlxCo1-x)O2
磁性
自旋态
结构演化 相似文献
79.
In this paper, based on the Lame function and Jacobi elliptic function, the perturbation method is appliedto some nonlinear evolution equations to derive their multi-order solutions. 相似文献
80.
Andrzej Dabrowski Erich Robens Peter Klobes Klaus Meyer Przemyslaw Podkocielny 《Particle & Particle Systems Characterization》2003,20(5):311-322
Since a comprehensive survey published in 1999 [1] much work was done in standardizing measuring methods to characterize the surface geometry of dispersed and/or porous solids and to certify reference materials. The present paper is an extension of a short communication [2]. It gives a survey on existing standards and reports on new drafts and proposals. 相似文献