全文获取类型
收费全文 | 19904篇 |
免费 | 3566篇 |
国内免费 | 2672篇 |
专业分类
化学 | 4116篇 |
晶体学 | 101篇 |
力学 | 2988篇 |
综合类 | 768篇 |
数学 | 10405篇 |
物理学 | 7764篇 |
出版年
2024年 | 126篇 |
2023年 | 439篇 |
2022年 | 458篇 |
2021年 | 463篇 |
2020年 | 370篇 |
2019年 | 465篇 |
2018年 | 316篇 |
2017年 | 530篇 |
2016年 | 521篇 |
2015年 | 699篇 |
2014年 | 1325篇 |
2013年 | 1056篇 |
2012年 | 1579篇 |
2011年 | 1620篇 |
2010年 | 1380篇 |
2009年 | 1465篇 |
2008年 | 2168篇 |
2007年 | 1260篇 |
2006年 | 1126篇 |
2005年 | 1349篇 |
2004年 | 981篇 |
2003年 | 1140篇 |
2002年 | 873篇 |
2001年 | 805篇 |
2000年 | 551篇 |
1999年 | 449篇 |
1998年 | 435篇 |
1997年 | 374篇 |
1996年 | 296篇 |
1995年 | 343篇 |
1994年 | 277篇 |
1993年 | 172篇 |
1992年 | 183篇 |
1991年 | 160篇 |
1990年 | 151篇 |
1989年 | 115篇 |
1988年 | 38篇 |
1987年 | 25篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1979年 | 3篇 |
1959年 | 1篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
It is a very complex and time-consuming process to simulate the nuclear reactor neutron spectrum from the reactor core to the export channel by applying a Monte Carlo program. This paper presents a new method to calculate the neutron spectrum by using the convolution technique which considers the channel transportation as a linear system and the transportation scattering as the response function. It also applies Monte Carlo Neutron and Photon Transport Code (MCNP) to simulate the response function numerically. With the application of convolution technique to calculate the spectrum distribution from the core to the channel, the process is then much more convenient only with the simple numerical integral numeration. This saves computer time and reduces some trouble in re-writing of the MCNP program. 相似文献
992.
This paper is intended to apply the potential integration method to the differential equations of the Birkhoffian system. The method is that, for a given Birkhoffian system, its differential equations are first rewritten as 2n first-order differential equations. Secondly, the corresponding partial differential equations are obtained by potential integration method and the solution is expressed as a complete integral. Finally, the integral of the system is obtained. 相似文献
993.
994.
A second-order dynamic phase transition in a non-equilibrium Eggers urn model for the separation of sand is studied. The order parameter, the susceptibility and the stationary probability distribution have been calculated. By applying the Lee-Yang zeros method of equilibrium phase transitions, we study the distributions of the effective partition function zeros and obtain the same result for the model. Thus, the Lee-Yang theory can be applied to a more general non-equilibrium system. 相似文献
995.
Adomian decomposition method and Padé approximants for solving the Blaszak--Marciniak lattice 下载免费PDF全文
The Adomian decomposition method (ADM) and Pade approximants are combined to solve the well-known Blaszak-Marciniak lattice, which has rich mathematical structures and many important applications in physics and mathematics. In some cases, the truncated series solution of ADM is adequate only in a small region when the exact solution is not reached. To overcome the drawback, the Pade approximants, which have the advantage in turning the polynomials approximation into a rational function, are applied to the series solution to improve the accuracy and enlarge the convergence domain. By using the ADM-Pade technique, the soliton solutions of the Blaszak-Marciniak lattice are constructed with better accuracy and better convergence than by using the ADM alone. Numerical and figurative illustrations show that it is a promising tool for solving nonlinear problems. 相似文献
996.
A new variable coefficient algebraic method and non-travelling wave solutions of nonlinear equations 下载免费PDF全文
In this paper, a new auxiliary equation method is presented of constructing more new non-travelling wave solutions of nonlinear differential equations in mathematical physics, which is direct and more powerful than projective Riccati equation method. In order to illustrate the validity and the advantages of the method, (2+1)-dimensional asymmetric Nizhnik-Novikov-Vesselov equation is employed and many new double periodic non-travelling wave solutions are obtained. This algorithm can also be applied to other nonlinear differential equations. 相似文献
997.
Synchronization of stochastically hybrid coupled neural networks with coupling discrete and distributed time-varying delays 下载免费PDF全文
A general model of linearly stochastically coupled identical connected neural networks with hybrid coupling is proposed, which is composed of constant coupling, coupling discrete time-varying delay and coupling distributed timevarying delay. All the coupling terms are subjected to stochastic disturbances described in terms of Brownian motion, which reflects a more realistic dynamical behaviour of coupled systems in practice. Based on a simple adaptive feedback controller and stochastic stability theory, several sufficient criteria are presented to ensure the synchronization of linearly stochastically coupled complex networks with coupling mixed time-varying delays. Finally, numerical simulations illustrated by scale-free complex networks verify the effectiveness of the proposed controllers. 相似文献
998.
In this paper, the dynamical behaviour of a linear impulsive system is discussed both theoretically and numerically. The existence and the stability of period-one solution are discussed by using a discrete map. The conditions of existence for flip bifurcation are derived by using the centre manifold theorem and bifurcation theorem. The bifurcation analysis shows that chaotic solutions appear via a cascade of period-doubling in some interval of parameters. Moreover, the periodic solutions, the bifurcation diagram, and the chaotic attractor, which show their consistence with the theoretical analyses, are given in an example. 相似文献
999.
利用激光干涉测速技术(VISAR)测量LY12铝合金在20—34 GPa冲击压力下经历加载-卸载和加载-再加载过程的样品/窗口界面粒子速度剖面,采用AC方法确定了具有较高精度的动态屈服强度值.实验结果和文献发表的数据具有较好的一致性.通过以平面焊接方式制作组合飞片,克服了组合飞片在气炮发射过程中可能发生分离的技术困难,使铝的动态屈服强度测量压力范围从22 GPa扩展到了34 GPa.同时,根据对不同实验条件下的加载-再加载过程的比较,对再加载弹性前驱波的形成机理进行了讨论,认为位错是形成该现象的主要原因. 相似文献
1000.