全文获取类型
收费全文 | 1098篇 |
免费 | 65篇 |
国内免费 | 85篇 |
专业分类
化学 | 185篇 |
晶体学 | 8篇 |
力学 | 82篇 |
综合类 | 4篇 |
数学 | 396篇 |
物理学 | 573篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 24篇 |
2021年 | 29篇 |
2020年 | 21篇 |
2019年 | 33篇 |
2018年 | 25篇 |
2017年 | 30篇 |
2016年 | 33篇 |
2015年 | 26篇 |
2014年 | 45篇 |
2013年 | 106篇 |
2012年 | 28篇 |
2011年 | 56篇 |
2010年 | 43篇 |
2009年 | 86篇 |
2008年 | 63篇 |
2007年 | 62篇 |
2006年 | 60篇 |
2005年 | 57篇 |
2004年 | 49篇 |
2003年 | 57篇 |
2002年 | 40篇 |
2001年 | 28篇 |
2000年 | 32篇 |
1999年 | 39篇 |
1998年 | 21篇 |
1997年 | 20篇 |
1996年 | 29篇 |
1995年 | 17篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1974年 | 1篇 |
排序方式: 共有1248条查询结果,搜索用时 15 毫秒
81.
Andrew Janca P.F. Bernath N.F. Zobov S.V. Shirin Oleg L. Polyansky Jonathan Tennyson 《Journal of Molecular Spectroscopy》2003,219(1):132-135
Fourier transform emission spectra were recorded using a mixture of H2O and D2O at a temperature of 1500 °C. The spectra were recorded in three overlapping sections and cover the wavenumber range 1800-3932 cm−1. This spectrum is analyzed together with a previously reported one spanning the 380-2190 cm−1 range [Parekunnel et al., J. Mol. Spectrosc. 2001 (28) 101]. This analysis leads to 4409 newly assigned HDO emission lines. This work particularly extends data on the (200) and (120) states of HDO for which newly determined energy levels are presented. 相似文献
82.
Wen-Rong Dai 《Journal of Mathematical Analysis and Applications》2007,327(1):188-202
In this paper, we study the regularity of the eigenvalues and eigenvectors and the existence of normalized coordinates for quasilinear hyperbolic systems with characteristic fields of constant multiplicity. We prove that the eigenvalues and eigenvectors of the system have the same regularity as the coefficients of the system. On the other hand, we show that, for the quasilinear hyperbolic system of conservation laws with characteristic fields of constant multiplicity, the normalized coordinates exist on the domain under consideration. 相似文献
83.
工程场地与城市在空间尺度上相去甚远 ,但工程场地所具备的与环境行为相近的共性 ,使其属性分析可以推广应用到城市建设所面对的整个工程地质环境。从这一意义上说 ,工程场地是整个城市宏观工程地质环境的微观单元 ,众多微观单元的组合构成了环境的宏观总体。为此 ,工程场地的三大属性———特性、适宜性、稳定性 ,可以作为城市工程地质环境分析中分析方法的基础。从工程场地分析推广到城市工程地质环境分析 ,还将有助于保证城市工程地质环境分析的定量化水平。 相似文献
84.
Hilbert空间中最终范数连续半群的特征条件 总被引:5,自引:0,他引:5
本文给出了Hilbert空间中当t>t0(t0≥0)时,按一致算子拓扑连续C0半 群T(t)的四个特征条件. 相似文献
85.
86.
用Ar气作保护气体 ,气压保持在一个标准大气压 ,用Nd :YAG脉冲激光烧蚀Al靶获得等离子体。利用时空分辨技术 ,采集了激光脉冲能量在 5 2 ,92 ,115和 14 5mJ情况下等离子体辐射的时空分辨谱。详细描述了 115mJ时等离子体的辐射特征 ,简要分析了其他脉冲能量下Ar的特征辐射规律。根据这些脉冲能量下Ar 特征谱线的分布规律 ,简要论述了Ar气体电离与激光脉冲能量的关系。讨论了环境气体电离机制 ,并对结果进行了简单解释。结果发现 ,在本实验采用的能量范围内 ,较高的脉冲能量更容易使环境气体电离 ,产生较强的Ar 离子辐射 ,且Ar 辐射持续时间较长。 相似文献
87.
A new dual band erbium-doped fiber amplifier configuration that provides 120 nm of optical bandwidth is simulated. This configuration employs a split-band architecture in which optical signals are splitted using a 1550/1610 nm port filter into two independent sub-bands which then pass in parallel through separate branches of the optical amplifier. Each branch may be optimized for the sub-band that traverses it. The independent sub-bands are combined and flattened before output, resulting in a 120 nm bandwidth gain-flattened optical amplifier. 相似文献
88.
Tadeus Nawka Lutz Christian Anders Mario Cebulla David Zurakowski 《Journal of voice》1997,11(4):422-428
Spectral analysis of vowels during connected speech can be performed using the spectral intensity distribution within critical bands corresponding to a natural scale on the basilar membrane. Normalization of the spectra provides the opportunity to make objective comparisons independent from the recording level. An increasing envelope peak between 3,150 and 3,700 Hz has been confirmed statistically for a combination of seven vowels in three groups of male speakers with hoarse, normal, and professional voices. Each vowel is also analyzed individually. The local energy maximum is called “the speaker's formant” and can be found in the region of the fourth formant. The steepness of the spectral slope (i.e. the rate of decline) becomes less pronounced when the sonority or the intensity of the voice increases. The speaker's formant is connected with the sonorous quality of the voice. It increases gradually and is approximately 10 dB higher in professional male voices than in normal male voices at neutral loudness (60 dB at 0.3 min). The peak intensity becomes stronger (30 dB above normal voices) when the overall speaking loudness is increased to 80 dB. Shouting increases the spectral energy of the adjacent critical bands but not the speaker's formant itself. 相似文献
89.
Larry J. Gerstein 《Linear and Multilinear Algebra》2004,52(5):381-383
Characteristic elements have been useful in the classification of unimodular lattices over the integers. This article gives an explicit formula for characteristic elements of a lattice in terms of a basis for the lattice and the dual of that basis. 相似文献
90.
Prof. Dr. B. F. Arnold 《Mathematical Methods of Operations Research》1990,34(1):59-74
Summary In controlling the mean of a multivariate normally distributed quality characteristic the main disadvantage of the globalT
2-control charts is that they don't indicate the component of the quality characteristic which gives rise to an alarm. To avoid this disadvantage the joint use of¯x-charts is proposed in this paper, where — for the sake of simplicity — the investigations are restricted to the case of independent components and to one-sided¯x-charts. On the basis of an economic objective function an approximation to the optimal design of the¯x-charts procedure is derived and discussed. It turns out that at least in the bivariate case the nearly optimal economic design is very close to the exact solution.Supported by the Deutsche Forschungsgemeinschaft (DFG). 相似文献