全文获取类型
收费全文 | 499篇 |
免费 | 59篇 |
国内免费 | 40篇 |
专业分类
化学 | 124篇 |
晶体学 | 3篇 |
力学 | 41篇 |
综合类 | 4篇 |
数学 | 231篇 |
物理学 | 195篇 |
出版年
2023年 | 8篇 |
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 14篇 |
2019年 | 26篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 18篇 |
2015年 | 12篇 |
2014年 | 18篇 |
2013年 | 50篇 |
2012年 | 31篇 |
2011年 | 27篇 |
2010年 | 20篇 |
2009年 | 26篇 |
2008年 | 26篇 |
2007年 | 26篇 |
2006年 | 23篇 |
2005年 | 34篇 |
2004年 | 29篇 |
2003年 | 20篇 |
2002年 | 18篇 |
2001年 | 18篇 |
2000年 | 16篇 |
1999年 | 15篇 |
1998年 | 11篇 |
1997年 | 17篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有598条查询结果,搜索用时 600 毫秒
1.
总结两个保守映象不可逆地分段连续链接(称为类耗散系统)以及一个保守映象与一个耗散映象不可逆地分段连续链接(称为半耗散系统)情况下得到的五项共同动力学特征:不连续边界象集构成的随机网成为唯一的混沌轨道;由于某些相点具有两个逆象而导致的相空间塌缩(类耗散);由于系统的不连续不可逆性质而出现的胖分形禁区网;在具有吸引子共存时占据不连续边界象集随机网和胖分形禁区网区域的点滴状吸引域以及由此导致的吸引子不可预言性;即使在传统强耗散存在的情况下点滴状吸引域仍由类耗散机制主宰.以一个累积-触发电路为例,说明这五项系统动
关键词:
随机网
禁区网
点滴状吸引域 相似文献
2.
3.
The variational method in a reformulated Hamiltonian formalism of Quantum Field Theory (QFT) is used to derive relativistic n-body wave equations for scalar particles (bosons) interacting via a massive or massless mediating scalar field (the scalar Yukawa model). Simple Fock-space variational trial states are used to derive relativistic n-body wave equations. The equations are shown to have the Schrödinger non-relativistic limits, with Coulombic interparticle potentials in the case of a massless mediating field and Yukawa interparticle potentials in the case of a massive mediating field. Some examples of approximate ground state solutions of the n-body relativistic equations are obtained for various strengths of coupling, for both massive and massless mediating fields. 相似文献
4.
Steven J. Sepanski 《Journal of Theoretical Probability》1997,10(4):1053-1063
For independent identically distributed random vectors belonging to the generalized Domain of Attraction of the multivariate normal law, we define two partial sum processes analogous to that of Donsker's Theorem. We prove that each converges in distribution to a Brownian Motion in the space of continuous functions. One process uses nonrandom operator normalization, and the other is a studentization of the first, using normalization by the empirical covariance operator. 相似文献
5.
We consider the dynamics of the lowest order transversal vibration mode of a suspension bridge, for which the hangers are treated as one-sided springs, according to the model of Lazer and McKeena [SIAM Review
58, 1990, 537]. We analyze in particular the multi-stability of periodic attractors and the basin of attraction structure in phase space and its dependence with the model parameters. The parameter values used in numerical simulations have been estimated from a number of bridges built in the United States and in the United Kingdom, thus taking into account realistic, yet sometimes simplified, structural, aerodynamical, and physical considerations. 相似文献
6.
Solution rheology of 2‐vinyl pyridine and N‐methyl‐2‐vinyl pyridinium chloride random copolymers in ethylene glycol was studied over wide ranges of concentration and effective charge. The fraction of quaternized monomers α and the fraction of monomers bearing an effective charge f of these copolymers were measured using counterion titration and dielectric spectroscopy, respectively. Ethylene glycol is a good solvent for neutral poly(2‐vinyl pyridine), with very few ionic impurities. The viscosity η and relaxation time τ of dilute and semidilute unentangled solutions exhibit the scaling with concentration and effective charge expected by the Dobrynin model. Reduced viscosity data are independent of concentration in dilute solution, giving an intrinsic viscosity that depends on effective charge, and the experimental data obey the Fuoss law in the semidilute unentangled regime. Scaling concentration with the overlap concentration (c/c*) reduces these data to common curves, and c* ~ f ?12/7 as predicted by the Dobrynin model, where f is the fraction of monomers bearing an effective charge. While the overlap concentration depends strongly on effective charge until counterion condensation occurs, the entanglement concentration ce is surprisingly insensitive to effective charge, indicating that entanglement effects are not understood using the Dobrynin model. The terminal modulus G = η/τ depends only on the number density of chains G = ckT/N for c* < c < ce, and G ~ c3/2 for c > ce independent of the effective charge. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2001–2013, 2006 相似文献
7.
LetX,X
1,X
2,... be i.i.d. random vectors in d. The limit laws that can arise by suitable affine normalizations of the partial sums,S
n=X
1+...+X
n, are calledoperator-stable laws. These laws are a natural extension to
d
of the stable laws on. Thegeneralized domain of attraction of [GDOA()] is comprised of all random vectorsX whose partial sums can be affinely normalized to converge to . If the linear part of the affine transformation is restricted to take the formn
–B for some exponent operatorB naturally associated to thenX is in thegeneralized domain of normal attraction of [GDONA()]. This paper extends the theory of operator-stable laws and their domains of attraction and normal attraction. 相似文献
8.
Mao-fengZhang Qiao-hongYao Chun-huiHuang Wei-xiaoCao 《高分子科学》2005,(1):27-27
A kind of azo-containing resin (Azo-R) was synthesized by a simple way through the coupling reaction of 2-nitro-N-methyldiphenylamine-4-diazoresin (NDR) with phenol, and a new covalentely attached multilayer film from Azo-R as H-donor and photosensitive diazoresin, diphenylamine-4-diazoresin (DR) as H-acceptor via H-bonding attraction by selfassembly technique has been fabricated. Following the decomposition of diazonium group of DR under exposure to UV light, the H-bonds between the layers of the film convert to covalent bonds and the film becomes very stable toward polar solvents or electrolyte aqueous solutions. Thus the UV-irradiated azo-containing films can be used to measure photocurrent in a conventional three-electrode photoelectrochemical cell using KCl as supporting electrolyte. It was confirmed that the azo-containing multilayer film is responsible for the photocurrent generation. 相似文献
9.
5-氟尿嘧啶-1-乙酸合铜(Ⅱ)的合成及其与DNA的作用 总被引:1,自引:0,他引:1
The 5-fluorouracil-1-acetic acid (5FuAA) and its Cu(Ⅱ) complex (5FuAACu) were synthesized and the date for the crystal complex was obtained. The interaction of 5-fluorouracil-1-acetic acid (5FuAA) and its Cu(Ⅱ) complex (5FuAACu) with DNA was also investigated by using spectral, viscometric, electrochemical and agarose gel electrophoresis methods. The results of interaction with DNA suggest that both 5FuAA and 5FuAACu can bind to DNA in a static electricity attraction mode. But the attraction of 5FuAACu is greater than that of 5FuAA. 相似文献
10.
If the centered and normalized partial sums of an i.i.d. sequence of random variables converge in distribution to a nondegenerate limit then we say that this sequence belongs to the domain of attraction of the necessarily stable limit. If we consider only the partial sums which terminate atk
n
wherek
n+1
ck
n
then the sequence belongs to the domain of semistable attraction of the necessarily semistable limit. In this paper, we consider the case where the limiting distribution is nonnormal. We obtain a series representation for the partial sums which converges almost surely. This representation is based on the order statistics, and utilizes the Poisson process. Almost sure convergence is a useful technical device, as we illustrate with a number of applications.This research was supported by a research scholarship from the Deutsche Forschungsgemeinschaft (DFG). 相似文献