全文获取类型
收费全文 | 30372篇 |
免费 | 3630篇 |
国内免费 | 3526篇 |
专业分类
化学 | 10415篇 |
晶体学 | 106篇 |
力学 | 2613篇 |
综合类 | 233篇 |
数学 | 11714篇 |
物理学 | 12447篇 |
出版年
2024年 | 93篇 |
2023年 | 320篇 |
2022年 | 679篇 |
2021年 | 779篇 |
2020年 | 974篇 |
2019年 | 888篇 |
2018年 | 880篇 |
2017年 | 982篇 |
2016年 | 1163篇 |
2015年 | 993篇 |
2014年 | 1514篇 |
2013年 | 2659篇 |
2012年 | 1627篇 |
2011年 | 1871篇 |
2010年 | 1508篇 |
2009年 | 1868篇 |
2008年 | 1921篇 |
2007年 | 1965篇 |
2006年 | 1684篇 |
2005年 | 1505篇 |
2004年 | 1201篇 |
2003年 | 1207篇 |
2002年 | 1112篇 |
2001年 | 922篇 |
2000年 | 935篇 |
1999年 | 750篇 |
1998年 | 693篇 |
1997年 | 550篇 |
1996年 | 377篇 |
1995年 | 360篇 |
1994年 | 307篇 |
1993年 | 289篇 |
1992年 | 280篇 |
1991年 | 230篇 |
1990年 | 238篇 |
1989年 | 221篇 |
1988年 | 199篇 |
1987年 | 192篇 |
1986年 | 162篇 |
1985年 | 182篇 |
1984年 | 176篇 |
1983年 | 95篇 |
1982年 | 133篇 |
1981年 | 124篇 |
1980年 | 105篇 |
1979年 | 109篇 |
1978年 | 91篇 |
1977年 | 94篇 |
1976年 | 80篇 |
1973年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Introduction In the previous studies on the oxidation reaction,peroxydisulfate was widely used as an oxidizingagent.1-5 One of the advantages of this oxidant lies in itsstability in a wide range of pH values. The reaction be-tween Fe(CN)5L3- (L=N-aromatic heterocyclic li-gands) and S2O8 2- has been proved to proceed throughan outer-sphere electron transfer mechanism.5 For a re-action [(Eq. (1)] to be under an outer-sphere mechanismthe steps involved are the formation of a reactant … 相似文献
62.
Patrick Guidotti 《Mathematische Nachrichten》2004,272(1):32-45
We consider elliptic and parabolic problems in unbounded domains. We give general existence and regularity results in Besov spaces and semi‐explicit representation formulas via operator‐valued fundamental solutions which turn out to be a powerful tool to derive a series of qualitative results about the solutions. We give a sample of possible applications including asymptotic behavior in the large, singular perturbations, exact boundary conditions on artificial boundaries and validity of maximum principles. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
63.
C. -H. L. Ong 《Annals of Pure and Applied Logic》2004,130(1-3):125-171
We prove that the observational equivalence of third-order finitary (i.e. recursion-free) Idealized Algol (IA) is decidable using Game Semantics. By modelling the state explicitly in our games, we show that the denotation of a term M of this fragment of IA is a compactly innocent strategy-with-state, i.e. the strategy is generated by a finite view function fM. Given any such fM, we construct a real-time deterministic pushdown automaton (DPDA) that recognizes the complete plays of the knowing-strategy denotation of M. Since such plays characterize observational equivalence, and there is an algorithm for deciding whether any two DPDAs recognize the same language, we obtain a procedure for deciding the observational equivalence of third-order finitary IA. Restricted to second-order terms, the DPDA representation cuts down to a deterministic finite automaton; thus our approach gives a new proof of Ghica and McCusker’s regular-expression characterization for this fragment. Our algorithmic representation of program meanings, which is compositional, provides a foundation for model-checking a wide range of behavioural properties of IA and other cognate programming languages. Another result concerns second-order IA with full recursion: we show that observational equivalence for this fragment is undecidable. 相似文献
64.
K. Kubilius 《Acta Appl Math》2003,78(1-3):233-242
We consider the integral equation driven by a standard Brownian motion and by a fractional Brownian motion. Sufficient conditions under which the equation has a weak solution are obtained. 相似文献
65.
通过对非饱和土非线性本构方程和场方程的线性化,推导出了非饱和土的线性本构方程和场方程,把线性方程表示为与Biot饱和多孔介质方程相似的形式;证明了Darcy定律对非饱和土的适用性;说明了Biot饱和多孔介质方程是这些线性方程的特征。所有这些都表明用混合理论处理非饱和土本构问题的正确性。 相似文献
66.
基于粗糙集理论的知识约简及应用实例 总被引:5,自引:0,他引:5
在保持分类能力不变的前提下 ,通过利用粗糙集理论中的知识约简方法 ,在保护知识库分类不变的条件下 ,删除其中不相关或不重要的知识 ,从而导出问题的决策 .利用基于决策表的粗糙集模型算法 ,实例分析如何数字化表示决策表 ,并对其进行属性约简和属性值的约简 ,从而提取决策规则 . 相似文献
67.
The electromagnetic (EM) energy flow near single spheres is investigated by applying Mie theory. From the patterns of the energy flow, the absorption and the scattering of light can be understood in the microscopic point of view. In the absorption profiles of metallic particles, most absorbed energy is consumed on the surface of the particles, which indicates that the resonance of surface plasmon is different from that of the bulk plasmon. Two mechanisms to enhanced local EM field are also distinguished. One is the surface plasmon resonance, and another one is the intensified energy flow. 相似文献
68.
Luis L. Bonilla 《Journal of statistical physics》1987,46(3-4):659-678
A nonlinear Fokker-Planck equation is derived to describe the cooperative behavior of general stochastic systems interacting via mean-field couplings, in the limit of an infinite number of such systems. Disordered systems are also considered. In the weak-noise limit; a general result yields the possibility of having bifurcations from stationary solutions of the nonlinear Fokker-Planck equation into stable time-dependent solutions. The latter are interpreted as non-equilibrium probability distributions (states), and the bifurcations to them as nonequilibrium phase transitions. In the thermodynamic limit, results for three models are given for illustrative purposes. A model of self-synchronization of nonlinear oscillators presents a Hopf bifurcation to a time-periodic probability density, which can be analyzed for any value of the noise. The effects of disorder are illustrated by a simplified version of the Sompolinsky-Zippelius model of spin-glasses. Finally, results for the Fukuyama-Lee-Fisher model of charge-density waves are given. A singular perturbation analysis shows that the depinning transition is a bifurcation problem modified by the disorder noise due to impurities. Far from the bifurcation point, the CDW is either pinned or free, obeying (to leading order) the Grüner-Zawadowki-Chaikin equation. Near the bifurcation, the disorder noise drastically modifies the pattern, giving a quenched average of the CDW current which is constant. Critical exponents are found to depend on the noise, and they are larger than Fisher's values for the two probability distributions considered. 相似文献
69.
Rie Natsui 《Acta Mathematica Hungarica》2005,108(4):299-318
Summary Let Fq be a finite field with q elements. We consider formal Laurent series of Fq -coefficients with their continued fraction expansions by Fq -polynomials. We prove some arithmetic properties for almost every formal Laurent series with respect to the Haar measure. We construct a group extension of the non-archimedean continued fraction transformation and show its ergodicity. Then we get some results as an application of the individual ergodic theorem. We also discuss the convergence rate for limit behaviors. 相似文献
70.