全文获取类型
收费全文 | 32850篇 |
免费 | 2189篇 |
国内免费 | 2488篇 |
专业分类
化学 | 2505篇 |
晶体学 | 54篇 |
力学 | 953篇 |
综合类 | 390篇 |
数学 | 9247篇 |
物理学 | 3342篇 |
综合类 | 21036篇 |
出版年
2024年 | 83篇 |
2023年 | 276篇 |
2022年 | 486篇 |
2021年 | 633篇 |
2020年 | 588篇 |
2019年 | 656篇 |
2018年 | 685篇 |
2017年 | 896篇 |
2016年 | 936篇 |
2015年 | 992篇 |
2014年 | 1675篇 |
2013年 | 1907篇 |
2012年 | 1756篇 |
2011年 | 1898篇 |
2010年 | 1482篇 |
2009年 | 1825篇 |
2008年 | 1911篇 |
2007年 | 2332篇 |
2006年 | 2069篇 |
2005年 | 1911篇 |
2004年 | 1782篇 |
2003年 | 1561篇 |
2002年 | 1345篇 |
2001年 | 1004篇 |
2000年 | 972篇 |
1999年 | 844篇 |
1998年 | 689篇 |
1997年 | 636篇 |
1996年 | 509篇 |
1995年 | 500篇 |
1994年 | 427篇 |
1993年 | 401篇 |
1992年 | 343篇 |
1991年 | 307篇 |
1990年 | 265篇 |
1989年 | 236篇 |
1988年 | 180篇 |
1987年 | 132篇 |
1986年 | 75篇 |
1985年 | 53篇 |
1984年 | 43篇 |
1983年 | 28篇 |
1982年 | 41篇 |
1981年 | 37篇 |
1980年 | 24篇 |
1979年 | 22篇 |
1978年 | 23篇 |
1977年 | 16篇 |
1976年 | 10篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
31.
小波分析在证券分析中的应用 总被引:1,自引:0,他引:1
传统股市投资分析中的证券分析方法之一———MACD法 ,利用DIF的移动平均值以确定证券的买卖时机 ,存在着时滞性 ,对非平稳的股市信息分析不能及时、较好地刻画股市的基本变化趋势 .作者根据证券投资理论 ,建立了相应的证券投资分析数学模型 ,根据小波分析多尺度分析能力强的特点 ,利用小波分解提取反映股市基本变化趋势的低频信息 ,改进了传统分析方法 ,建立了改进后的数学模型Ⅲ .该模型求解方便 ,同时与实际模型较好地逼近 ,具有时效性 .此外 ,以路桥建设股票 14 0个交易日的DIF和MACD值作为原始数据 ,用Matlab作为工具进行计算 ,求解模型Ⅲ .结果表明 :与传统分析方法相比 ,从模型Ⅲ中能得到更多的买卖点信息 ,而且价差更大 ,效果显著 ,充分显示了小波分析在股市技术分析中的强大生命力 相似文献
32.
33.
The theory of tree-growing (RECPAM approach) is developed for outcome variables which are distributed as the canonical exponential family. The general RECPAM approach (consisting of three steps: recursive partition, pruning and amalgamation), is reviewed. This is seen as constructing a partition with maximal information content about a parameter to be predicted, followed by simplification by the elimination of ‘negligible’ information. The measure of information is defined for an exponential family outcome as a deviance difference, and appropriate modifications of pruning and amalgamation rules are discussed. It is further shown how the proposed approach makes it possible to develop tree-growing for situations usually treated by generalized linear models (GLIM). In particular, Poisson and logistic regression can be tree-structured. Moreover, censored survival data can be treated, as in GLIM, by observing a formal equivalence of the likelihood under random censoring and an appropriate Poisson model. Three examples are given of application to Poisson, binary and censored survival data. 相似文献
34.
本文定义了二阶微分方程的弱 Carathéodory解 ,在不涉及紧型条件的情形下 ,直接用迭代法证明了 Banach空间二阶非线性常微分方程两点边值问题存在唯一解 ,并给出逼近解迭代序列的误差估计 ,对周期边值问题得到类似的结果 相似文献
35.
Filippo Bracci Roberto Tauraso Fabio Vlacci 《Journal of Mathematical Analysis and Applications》2002,270(2):1131-473
Let f,g be two commuting holomorphic self-maps of the unit disc. If f and g agree at the common Wolff point up to a certain order of derivatives (no more than 3 if the Wolff point is on the unit circle), then f≡g. 相似文献
36.
37.
This paper solves the problem of the duration of the total eclipseof a satellite of a body, provided that (a) the body is sphericalin shape and the mass distribution inside the body is sphericallysymmetrical; (b) the satellite is a very small object; (c) thesatellite's orbit around a body is circular and the satellitecan pass through the centre of its shadow; (d) a source of lightis the source of the conical body's shadow (umbra) and it doesnot change its apparent position in the sky; (e) there are noperturbations on the satellite's orbit. The solution presentedrepresents the general discussion of the problem based on utilizationof some parts of the theory of contraction mappings. 相似文献
38.
A simple scheme is developed for treatment of vertical bed topography in shallow water flows. The effect of the vertical step on flows is modelled with the shallow water equations including local energy loss terms. The bed elevation is denoted with zb‐ for the left and zb+ for the right values at each grid point, hence exactly representing a discontinuity in the bed topography. The surface gradient method (SGM) is generalized to reconstruct water depths at cell interfaces involving a vertical step so that the fluxes at the cell interfaces can accurately be calculated with a Riemann solver. The scheme is verified by predicting a surge crossing a step, a tidal flow over a step and dam‐break flows on wet/dry beds. The results have shown good agreements compared with analytical solutions and available experimental data. The scheme is efficient, robust, and may be used for practical flow calculations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
39.
T. Temesvári C. De Dominicis I.R. Pimentel 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(3):361-372
Symmetry considerations and a direct, Hubbard-Stratonovich type, derivation are used to construct a replica field-theory relevant
to the study of the spin glass transition of short range models in a magnetic field. A mean-field treatment reveals that two
different types of transitions exist, whenever the replica number n is kept larger than zero. The Sherrington-Kirkpatrick critical point in zero magnetic field between the paramagnet and replica
magnet (a replica symmetric phase with a nonzero spin glass order parameter) separates from the de Almeida-Thouless line,
along which replica symmetry breaking occurs. We argue that for studying the de Almeida-Thouless transition around the upper
critical dimension d = 6, it is necessary to use the generic cubic model with all the three bare masses and eight cubic couplings. The critical
role n may play is also emphasized. To make perturbative calculations feasible, a new representation of the cubic interaction is
introduced. To illustrate the method, we compute the masses in one-loop order. Some technical details and a list of vertex
rules are presented to help future renormalisation-group calculations.
Received 9 October 2001 相似文献
40.
Cai Xiaochun 《Annals of Differential Equations》2006,22(1):1-6
In this paper, we apply a critical point theorem and obtain the condition for the existence of three solutions to two-point boundary value problem of a second order nonlinear difference equation. 相似文献