全文获取类型
收费全文 | 31782篇 |
免费 | 4038篇 |
国内免费 | 3802篇 |
专业分类
化学 | 9540篇 |
晶体学 | 211篇 |
力学 | 4858篇 |
综合类 | 527篇 |
数学 | 12048篇 |
物理学 | 12438篇 |
出版年
2024年 | 52篇 |
2023年 | 317篇 |
2022年 | 758篇 |
2021年 | 812篇 |
2020年 | 973篇 |
2019年 | 874篇 |
2018年 | 797篇 |
2017年 | 1099篇 |
2016年 | 1284篇 |
2015年 | 967篇 |
2014年 | 1622篇 |
2013年 | 2445篇 |
2012年 | 1711篇 |
2011年 | 2024篇 |
2010年 | 1738篇 |
2009年 | 2078篇 |
2008年 | 1986篇 |
2007年 | 2046篇 |
2006年 | 1667篇 |
2005年 | 1527篇 |
2004年 | 1426篇 |
2003年 | 1242篇 |
2002年 | 1236篇 |
2001年 | 1031篇 |
2000年 | 886篇 |
1999年 | 787篇 |
1998年 | 745篇 |
1997年 | 557篇 |
1996年 | 498篇 |
1995年 | 451篇 |
1994年 | 437篇 |
1993年 | 385篇 |
1992年 | 380篇 |
1991年 | 288篇 |
1990年 | 273篇 |
1989年 | 262篇 |
1988年 | 246篇 |
1987年 | 278篇 |
1986年 | 244篇 |
1985年 | 253篇 |
1984年 | 251篇 |
1983年 | 157篇 |
1982年 | 122篇 |
1981年 | 82篇 |
1980年 | 45篇 |
1979年 | 53篇 |
1978年 | 43篇 |
1977年 | 40篇 |
1976年 | 25篇 |
1973年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
271.
“后配额时代”中国纺织品服装出口预测 总被引:2,自引:0,他引:2
本文利用单整自回归移动平均模型,依据2000年1月至2004年12月中国纺织品服装出口额数据,对2005年和2006年中国纺织品服装出口走势进行预测分析。 相似文献
272.
为了让临床医生更方便地使用M eta分析方法,我们根据四格表数据特点,提出了一种基于固定效应模型的简明方法。该方法简单而容易操作,且统计结果与原方法完全等价,在循证医学领域很有推广价值。 相似文献
273.
王晓瑛 《纯粹数学与应用数学》2002,18(4):367-370
构造了一类新的分数布朗运动模型,它不同于Mandelbrot,Barton及Decreusefond等人所定义的分数布朗运动模型。 相似文献
274.
孙福伟 《数学的实践与认识》2002,32(3):370-373
本文提出了位移和速度同时反馈的数学模型 .并给出了位移和速度反馈的实现方法 ,该方法用传统的差动变压器实现了位移和速度的同时反馈 相似文献
275.
Recent experiments revealed that the dielectric dispersion spectrum of fission yeast cells in a suspension was mainly composed of two sub-dispersions. The low-frequency sub-dispersion depended on the cell length, while the high-frequency one was independent of it. The cell shape effect was simulated by an ellipsoidal cell model but the comparison between theory and experiment was far from being satisfactory. Prompted by the discrepancy, we proposed the use of spectral representation to analyze more realistic cell models. We adopted a shell-spheroidal model to analyze the effects of the cell membrane. It is found that the dielectric property of the cell membrane has only a minor effect on the dispersion magnitude ratio and the characteristic frequency ratio. We further included the effect of rotation of dipole induced by an external electric field, and solved the dipole-rotation spheroidal model in the spectral representation.Good agreement between theory and experiment has been obtained. 相似文献
276.
We define events so as to reduce the number of events and decision variables needed for modeling batch-scheduling problems such as described in [15]. We propose a new MILP formulation based on this concept, defining non-uniform time periods as needed and decision variables that are not time-indexed. It can handle complicated multi-product/multi-stage machine processes, with production lines merging and diverging, and with minimum and maximum batch sizes. We compare it with earlier models and show that it can solve problems with small to medium demands relative to batch sizes in reasonable computer times. 相似文献
277.
A mean-field model of nonlinearly coupled oscillators with randomly distributed frequencies and subject to independent external white noises is analyzed in the thermodynamic limit. When the frequency distribution isbimodal, new results include subcritical spontaneous stationary synchronization of the oscillators, supercritical time-periodic synchronization, bistability, and hysteretic phenomena. Bifurcating synchronized states are asymptotically constructed near bifurcation values of the coupling strength, and theirnonlinear stability properties ascertained. 相似文献
278.
279.
We consider a two-dimensional Coulomb gas of positive and negative pointlike unit charges interacting via a logarithmic potential. The density (rather than the charge) correlation functions are studied. In the bulk, the form-factor theory of an equivalent sine-Gordon model is used to determine the density correlation length. At the surface of a rectilinear plain wall, the universality of the asymptotic behavior of the density correlations is suggested. A scaling analysis implies a local form of the compressibility sum rule near a hard wall. A symmetry of the Coulomb system with respect to the Möbius conformal transformation, which induces a gravitational source acting on the particle density, is established. Among the consequences, a universal term of the finite-size expansion of the grand potential is derived exactly for a disk geometry of the confining domain. 相似文献
280.
Crossed modules have longstanding uses in homotopy theory and the cohomology of groups. The corresponding notion in the setting of categorical groups, that is, categorical crosses modules, allowed the development of a low-dimensional categorical group cohomology. Now, its relevance is also shown here to homotopy types by associating, to any pointed CW-complex (X,∗), a categorical crossed module that algebraically represents the homotopy 3-type of X. 相似文献