全文获取类型
收费全文 | 2556篇 |
免费 | 266篇 |
国内免费 | 89篇 |
专业分类
化学 | 798篇 |
力学 | 170篇 |
综合类 | 99篇 |
数学 | 1216篇 |
物理学 | 628篇 |
出版年
2024年 | 11篇 |
2023年 | 28篇 |
2022年 | 130篇 |
2021年 | 111篇 |
2020年 | 74篇 |
2019年 | 61篇 |
2018年 | 70篇 |
2017年 | 140篇 |
2016年 | 143篇 |
2015年 | 87篇 |
2014年 | 195篇 |
2013年 | 150篇 |
2012年 | 170篇 |
2011年 | 167篇 |
2010年 | 124篇 |
2009年 | 122篇 |
2008年 | 139篇 |
2007年 | 120篇 |
2006年 | 127篇 |
2005年 | 140篇 |
2004年 | 105篇 |
2003年 | 62篇 |
2002年 | 54篇 |
2001年 | 46篇 |
2000年 | 40篇 |
1999年 | 35篇 |
1998年 | 40篇 |
1997年 | 33篇 |
1996年 | 25篇 |
1995年 | 23篇 |
1994年 | 20篇 |
1993年 | 19篇 |
1992年 | 9篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有2911条查询结果,搜索用时 15 毫秒
881.
在银行体系脆弱性评价中借助物元的概念,建立了银行体系脆弱性评价模型,并采用较为客观的评价方法——可拓方法对该模型进行评价,介绍了一种新的银行体系脆弱性评价方法.消除了其它主观评价方法带来的偏差,从而为我国银行体系脆弱性的监管决策提供有益参考. 相似文献
882.
883.
针对多层次系统的动态评价问题,首先,应用极大不相关法筛选指标以去除重复的信息;其次,对指标进行一致化和无量纲化的预处理;再次,采用逐层纵横向拉开档次评价法确定评价对象在不同时刻的评价值;最后,应用时序几何平均算子来集结多个时间点的评价值,以得出最终的动态排序。这种方法没有丝毫主观色彩,适用于经济管理系统的动态评价问题。以评价电力企业的效益作为算例,说明了方法的应用价值。 相似文献
884.
885.
2010上海世博会影响力的定量评估——影响力的点刺激连带效应定量评估模型 总被引:2,自引:0,他引:2
利用互联网数据,在合理假设的前提下,给出了上海世博会对上海旅游业影响的定量评估.利用线性加权综合分析法建立综合评价指标的线性模型,并从两个不同的角度,分别得出上海世博会对上海旅游业的综合评价指标,同时建立灰色系统预测模型,利用2006至2009年的评价指标,对2010年的评价指标进行预测.通过实际的增长值与预测增长值的... 相似文献
886.
The interaction between Ni2+ and calf thymus DNA (ctDNA) was investigated in simulated physiological buffer (pH 7.4) using the Neutral Red (NR) dye as a spectral probe by UV-vis absorption and fluorescence spectroscopy, as well as CD spectra. The experimental results showed that the conformational changes in DNA helix induced by Ni2+ are the reason for the fluorescence quenching of the DNA-NR system. From the experimental results, conclusion can be drawn that Ni2+ can cause structural changes of ctDNA and bind with DNA by electrostatic interaction. At the same time, the paper proved that conformation changes of DNA can also lead to the fluorescence decrease of DNA-probe systems. 相似文献
887.
This article presents a numerical study of dispersion characteristics of some symmetric and antisymmetric composites modelled as multilayered packets of layers with arbitrary anisotropy of each layer. The authors introduce a subsidiary boundary problem of three-dimensional elasticity theory for the system of partial differential equations describing the harmonic oscillations of the composite caused by a surface load. The problem reduces to a boundary problem for ordinary differential equations by employing the Fourier transform. An algorithm of constructing the Fourier transform of the Green’s matrix of the given boundary problem is presented. The wave numbers of Lamb waves propagating in composites, their phase velocity surfaces and group wave surfaces are presented through the poles of the transform of the Green’s matrix. The authors obtain the dispersion curves for different directions and frequencies and investigate the dispersion curves and surfaces of wave numbers, phase velocities and group wave surfaces for various composites. The numerical results are then compared with the results obtained by applying other methods. 相似文献
888.
Full wavefield measurements obtained with either an air-coupled transducer mounted on a scanning stage or a scanning laser vibrometer can be combined with effective signal and imaging processing algorithms to support characterization of guided waves as well as detection, localization and quantification of structural damage. These wavefield images contain a wealth of information that clearly shows details of guided waves as they propagate outward from the source, reflect from specimen boundaries, and scatter from discontinuities within the structure. The analysis of weaker scattered waves is facilitated by the removal of source waves and the separation of wave modes, which is effectively achieved via frequency-wavenumber domain filtering in conjunction with the subsequent analysis of the resulting residual signals. Incident wave removal highlights the presence and the location of weak scatterers, while the separation of individual guided wave modes allows the characterization of their separate contribution to the scattered field and the evaluation of mode conversion phenomena. The effectiveness of these methods is demonstrated through their application to detection of a delamination in a composite plate and detection of a crack emanating from a hole. 相似文献
889.
890.
Zeng Wu Ming Yan Shi-He Hu Zhi-Cheng Yu Yong Zhu Ya-Dong Cheng Hai-Chun Liu Yan-Min Zhang Si-Hui Yao Wei-Fang Tang Tao Lu 《中国化学快报》2014,25(2):351-354
A series of novel indole derivatives were designed and synthesized and their inhibitory activity against B-Raf and HepG2 cell were also described. Among them, compounds 7a and 7b exhibited excellent potency, which showed the potential for further research as lead compounds. 相似文献