全文获取类型
收费全文 | 18523篇 |
免费 | 1687篇 |
国内免费 | 667篇 |
专业分类
化学 | 5024篇 |
晶体学 | 24篇 |
力学 | 1161篇 |
综合类 | 85篇 |
数学 | 8477篇 |
物理学 | 6106篇 |
出版年
2024年 | 28篇 |
2023年 | 175篇 |
2022年 | 334篇 |
2021年 | 410篇 |
2020年 | 490篇 |
2019年 | 490篇 |
2018年 | 363篇 |
2017年 | 397篇 |
2016年 | 633篇 |
2015年 | 511篇 |
2014年 | 856篇 |
2013年 | 1430篇 |
2012年 | 806篇 |
2011年 | 912篇 |
2010年 | 814篇 |
2009年 | 1106篇 |
2008年 | 1303篇 |
2007年 | 1285篇 |
2006年 | 1031篇 |
2005年 | 775篇 |
2004年 | 657篇 |
2003年 | 699篇 |
2002年 | 680篇 |
2001年 | 526篇 |
2000年 | 534篇 |
1999年 | 467篇 |
1998年 | 453篇 |
1997年 | 325篇 |
1996年 | 274篇 |
1995年 | 218篇 |
1994年 | 217篇 |
1993年 | 192篇 |
1992年 | 188篇 |
1991年 | 125篇 |
1990年 | 102篇 |
1989年 | 119篇 |
1988年 | 125篇 |
1987年 | 87篇 |
1986年 | 81篇 |
1985年 | 122篇 |
1984年 | 102篇 |
1983年 | 35篇 |
1982年 | 64篇 |
1981年 | 60篇 |
1980年 | 60篇 |
1979年 | 50篇 |
1978年 | 42篇 |
1977年 | 42篇 |
1976年 | 38篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
转动系统的相对论性分析力学理论 总被引:20,自引:3,他引:17
本文讨论了转动相对论力学理论,主要是建立转动系统的相对论性分析力学理论·构造转动系统的相对论性广义动能函数Tr=∑ni=1I0iΓi2(1-1-θ·2i/Γi2)和广义加速度能量函数Sr=12∑ni=1Ii(θ·i·θ¨i)2Γi2-θ·2i+θ¨2i,给出其Hamilton原理和三种不同形式的D′Alembert原理;对于完整约束系统,建立了转动系统的相对论性Lagrange方程、Nielsen方程、Appel方程和Hamilton正则方程;对于非完整约束系统,建立了转动系统的相对论性Routh方程、Чаплыгин方程、Nielsen方程和Appel方程;并给出转动系统的相对论性Noether守恒律 相似文献
122.
Rolf Vonhoff 《Mathematische Nachrichten》1998,193(1):199-210
In the paper, a new method of constructing asymptotic solutions of differential equations on manifolds with singularities is presented. This method allows not only to widen essentially the space of asymptotics but also to obtain explicit formulas for asymptotic expansions, in particular, in the case when in a neighborhood of a singular point there exist strata of different dimensions. 相似文献
123.
Uncertainty about the nature and significance of nonlinearities and the manner in which dynamics affect future realizations makes model specification the most difficult aspect of modeling dynamic systems. By interpreting several popular fishery models as subcases of a nesting dynamic Taylor series approximation, we isolate the specification differences between these models in a way that accounts for commonalities. On the argument that the differences due to alternative nonlinear forms are likely to be small compared to more mundane considerations such as delay difference and general dynamic lag specification, we propose an alternative model that uses the terms from the first order approximation common to all models combined with a data-based determination of the appropriate lags using the methods of state space time series analysis. Finally, the success of the alternative models is judged in an application to Pacific halibut data. 相似文献
124.
We have studied the vibrational frequencies and atom displacements of one-dimensional systems formed by combinations of Thue-Morse and Rudin-Shapiro quasi-regular stackings with periodic ones. The materials are described by nearest-neighbor force constants and the corresponding atom masses. These systems exhibit differences in the frequency spectrum as compared to the original simple quasi-regular generations and periodic structures. The most important feature is the presence of separate confinement of the atom displacements in one of the parts forming the total composite structure for different frequency ranges, thus acting as a kind of phononic cavity. 相似文献
125.
Henrik Flyvbjerg 《Physica A》2004,340(4):552-558
The nature of self-organized criticality (SOC) is pin-pointed with a simple mechanical model: a pinball machine. Its phase space is fully parameterized by two integer variables, one describing the state of an on-going game, the other describing the state of the machine. This is the simplest possible SOC system, having only two degrees of freedom and no spatial correlations, yet is not solvable by analytical means. 相似文献
126.
利用指数二分性理论和泛函分析方法,我们研究了自治奇摄动系统的同,异宿轨道的存在性,给出了高维奇摄动系统从退化系统分支出同异宿轨道的Mel-nikov型函数。 相似文献
127.
M. Reuhl P. Nielaba K. Binder 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(2):225-232
,Static and dynamic properties of the Potts model on the simple cubic lattice with nearest neighbor -interaction are obtained from Monte Carlo simulations in a temperature range where full thermal equilibrium still can be
achieved (). For a lattice size L
= 16, in this range finite size effects are still negligible, but the data for the spin glass susceptibility agree with previous
extrapolations based on finite size scaling of very small lattices. While the static properties are compatible with a zero
temperature transition, they certainly do not prove it. Unlike the Ising spin glass, the decay of the time-dependent order
parameter is compatible with a simple Kohlrausch function, , while a power law prefactor cannot be distinguished. The Kohlrausch exponent y
(
T
) decreases from at [0pt] to at [0pt] however. The relaxation time is compatible with the exponential divergence postulated by McMillan for spin glasses at their lower critical dimension,
but the exponent that can be extracted still differs significantly from the theoretical value, . Thus the present results support the conclusion that the Potts spin glass in d
= 3 dimensions differs qualitatively from the Ising spin glass.
Received: 8 October 1997 / Accepted: 27 November 1997 相似文献
128.
In this paper, we investigate strict stability of differential systems by variational Lyapunov function. We obtain some sufficient conditions and comparison theorems. 相似文献
129.
H.O.U. Fynbo Y. Prezado J. Äystö U.C. Bergmann M.J.G. Borge P. Dendooven W. Huang J. Huikari H. Jeppesen P. Jones B. Jonson M. Meister G. Nyman M. Oinonen K. Riisager O. Tengblad I.S. Vogelius Y. Wang L. Weissman K.W. Rolander 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):135-138