全文获取类型
收费全文 | 26501篇 |
免费 | 3278篇 |
国内免费 | 1193篇 |
专业分类
化学 | 5920篇 |
晶体学 | 161篇 |
力学 | 3158篇 |
综合类 | 228篇 |
数学 | 12735篇 |
物理学 | 8770篇 |
出版年
2024年 | 49篇 |
2023年 | 257篇 |
2022年 | 452篇 |
2021年 | 548篇 |
2020年 | 685篇 |
2019年 | 648篇 |
2018年 | 521篇 |
2017年 | 683篇 |
2016年 | 908篇 |
2015年 | 739篇 |
2014年 | 1177篇 |
2013年 | 1982篇 |
2012年 | 1236篇 |
2011年 | 1288篇 |
2010年 | 1183篇 |
2009年 | 1459篇 |
2008年 | 1687篇 |
2007年 | 1807篇 |
2006年 | 1519篇 |
2005年 | 1344篇 |
2004年 | 1115篇 |
2003年 | 1221篇 |
2002年 | 1118篇 |
2001年 | 906篇 |
2000年 | 878篇 |
1999年 | 814篇 |
1998年 | 718篇 |
1997年 | 565篇 |
1996年 | 425篇 |
1995年 | 354篇 |
1994年 | 320篇 |
1993年 | 301篇 |
1992年 | 254篇 |
1991年 | 194篇 |
1990年 | 172篇 |
1989年 | 136篇 |
1988年 | 154篇 |
1987年 | 121篇 |
1986年 | 110篇 |
1985年 | 160篇 |
1984年 | 134篇 |
1983年 | 56篇 |
1982年 | 89篇 |
1981年 | 93篇 |
1980年 | 73篇 |
1979年 | 68篇 |
1978年 | 75篇 |
1977年 | 61篇 |
1976年 | 48篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
191.
Pierre L'Ecuyer 《Annals of Operations Research》1994,53(1):77-120
In typical stochastic simulations, randomness is produced by generating a sequence of independent uniform variates (usually real-valued between 0 and 1, or integer-valued in some interval) and transforming them in an appropriate way. In this paper, we examine practical ways of generating (deterministic approximations to) such uniform variates on a computer. We compare them in terms of ease of implementation, efficiency, theoretical support, and statistical robustness. We look in particular at several classes of generators, such as linear congruential, multiple recursive, digital multistep, Tausworthe, lagged-Fibonacci, generalized feedback shift register, matrix, linear congruential over fields of formal series, and combined generators, and show how all of them can be analyzed in terms of their lattice structure. We also mention other classes of generators, like non-linear generators, discuss other kinds of theoretical and empirical statistical tests, and give a bibliographic survey of recent papers on the subject. 相似文献
192.
Masahiro Kubo 《Journal of Mathematical Analysis and Applications》2005,307(1):232-244
We study Neumann problem for a class of nonlinear degenerate parabolic PDE. A typical nonlinearity we have in mind is, for instance, β(u)=−1/u(u>0). We establish a necessary and sufficient condition on given data for existence of solution. 相似文献
193.
本文描述了利用KTP晶体和腔的基波输出镜构成非线性镜实现1.08μmNd:YAP激光器的被动锁模。实验表明,这种新的锁模技术比用染料作可饱和吸收体的被动锁模技术有很多突出的优点,具有很大的发展潜力。实验测得锁模时基波1.08μm输出2.4mJ,二次谐波0.54μm输出0.5mJ(同样条件下的静态输出为2.5mJ),基波脉冲的平均脉宽为40ps。 相似文献
194.
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
195.
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
196.
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
197.
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
198.
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
200.
Peter A. Markowich Gerhard Rein Gershon Wolansky 《Journal of statistical physics》2002,106(5-6):1221-1239
We consider the Schrödinger–Poisson system in the repulsive (plasma physics) Coulomb case. Given a stationary state from a certain class we prove its nonlinear stability, using an appropriately defined energy-Casimir functional as Lyapunov function. To obtain such states we start with a given Casimir functional and construct a new functional which is in some sense dual to the corresponding energy-Casimir functional. This dual functional has a unique maximizer which is a stationary state of the Schrödinger–Poisson system and lies in the stability class. The stationary states are parameterized by the equation of state, giving the occupation probabilities of the quantum states as a strictly decreasing function of their energy levels. 相似文献