全文获取类型
收费全文 | 53577篇 |
免费 | 4443篇 |
国内免费 | 2407篇 |
专业分类
化学 | 22521篇 |
晶体学 | 240篇 |
力学 | 4523篇 |
综合类 | 642篇 |
数学 | 9725篇 |
物理学 | 10156篇 |
无线电 | 12620篇 |
出版年
2024年 | 116篇 |
2023年 | 532篇 |
2022年 | 1328篇 |
2021年 | 1483篇 |
2020年 | 1501篇 |
2019年 | 1306篇 |
2018年 | 1165篇 |
2017年 | 1608篇 |
2016年 | 2149篇 |
2015年 | 1746篇 |
2014年 | 2693篇 |
2013年 | 3683篇 |
2012年 | 3343篇 |
2011年 | 3106篇 |
2010年 | 2547篇 |
2009年 | 2990篇 |
2008年 | 3122篇 |
2007年 | 3404篇 |
2006年 | 2886篇 |
2005年 | 2603篇 |
2004年 | 2424篇 |
2003年 | 2007篇 |
2002年 | 1591篇 |
2001年 | 1281篇 |
2000年 | 1229篇 |
1999年 | 1062篇 |
1998年 | 1030篇 |
1997年 | 896篇 |
1996年 | 800篇 |
1995年 | 757篇 |
1994年 | 666篇 |
1993年 | 515篇 |
1992年 | 490篇 |
1991年 | 418篇 |
1990年 | 368篇 |
1989年 | 254篇 |
1988年 | 243篇 |
1987年 | 147篇 |
1986年 | 129篇 |
1985年 | 157篇 |
1984年 | 131篇 |
1983年 | 66篇 |
1982年 | 110篇 |
1981年 | 64篇 |
1980年 | 56篇 |
1979年 | 84篇 |
1978年 | 37篇 |
1977年 | 18篇 |
1976年 | 26篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
S. P. Popov 《Computational Mathematics and Mathematical Physics》2006,46(6):983-994
Numerical solutions to three systems of integrable evolutionary equations from the Toda lattice hierarchy are analyzed. These are the classical Toda lattice, the second local dispersive flow, and the second extended dispersive flow. Special attention is given to the properties of soliton solutions. For the equations of the second local flow, two types of solitons interacting in a special manner are found. Solutions corresponding to various initial data are qualitatively outlined. 相似文献
92.
对于任意秩有限总体,在二次损失下,有关文献已给出了线性可预测变量在齐次线性预测类中的唯一线性Minimax预测.本文在正态假设下,证明了这个线性Minimax预测也是线性可预测变量在一切预测类中的唯一Minimax预测. 相似文献
93.
The prepared amorphous
γ-ZrP\SiO2 composite had a complicated composition,
since a part of γ-ZrP is converted to α-form during the exfoliation
of it. The γ-ZrP\SiO2 composite have specific surface
area of 421 m2g–1.
The acidic P–OH groups of the lamellae species placed on the surface
(it is ≈1.0 meq g–1), do not destroy until
the temperature of 1030 K. During the thermal treatment the total mass loss
of 7.79% was found. This value corresponds to 0.42 mole of H2O
per molecule unit. The water loss process was found very slow, because of
the placing of bilamellar species in the composite. 相似文献
94.
Qiu Hong WU He Xiang WANG Kun GAO State Key Laboratory of Applied Organic Chemistry College of Chemistry Chemical Engineering Lanzhou University Lanzhou 《中国化学快报》2006,17(2)
Many Ligularia species have long been used as traditional folk medicine for theirantibiotic, antiphlogistic and antitussive activities1, and were found to be an importantsource of eremophilane. In the course of our search for bioactive sesquiterpenoids, w… 相似文献
95.
96.
R.S. Kraußhar 《Journal of Mathematical Analysis and Applications》2007,325(1):359-376
In this paper we study Clifford and harmonic analysis on some examples of conformal flat manifolds that have a spinor structure, or more generally, at least a pin structure. The examples treated here are manifolds that can be parametrized by U/Γ where U is a subdomain of either Sn or Rn and Γ is a Kleinian group acting discontinuously on U. The examples studied here include RPn and the Hopf manifolds S1×Sn−1. Also some hyperbolic manifolds will be treated. Special kinds of Clifford-analytic automorphic forms associated to the different choices of Γ are used to construct explicit Cauchy kernels, Cauchy integral formulas, Green's kernels and formulas together with Hardy spaces and Plemelj projection operators for Lp spaces of hypersurfaces lying in these manifolds. 相似文献
97.
In this paper, the possibility of using the gradients of the temperature and of the internal parameters as additional state variables in Continuum Thermodynamics is considered. The expressions of the two principles are discussed and Clausius–Duhem inequality is derived under an appropriate statement of the internal entropy production. Several formulations are proposed and compared to existing results in the literature. To cite this article: P. Ireman, Q.S. Nguyen, C. R. Mecanique 332 (2004). 相似文献
98.
Performance analysis of IEEE 802.11 ad hoc networks in the presence of exposed terminals 总被引:1,自引:0,他引:1
The paper evaluates the performance effects of exposed terminals in IEEE 802.11 ad hoc networks in finite load conditions. It derives analytical models for the estimation of channel utilization and media access delay for IEEE 802.11 ad hoc networks in finite load conditions with and without exposed terminals. The simulation results show that the analytical estimated channel utilization and media access delay metrics are fairly accurate. 相似文献
99.
Ting-Ting Gao Dan Wu Ying-Ling Huang De-Zhong Yao 《中国电子科技》2007,5(3):272-277
A nonlinear method named detrended fluctuation analysis (DFA) was utilized to investigate the scaling behavior of the human electroencephalogram (EEG) in three emotional music conditions (fear, happiness, sadness) and a rest condition (eyes-closed). The results showed that the EEG exhibited scaling behavior in two regions with two scaling exponents β1 and β2 which represented the complexity of higher and lower frequency activity besides α band respectively. As the emotional intensity decreased the value of β1 increased and the value of β2 decreased. The change of β1 was weakly correlated with the 'approach-withdrawal' model of emotion and both of fear and sad music made certain differences compared with the eyes-closed rest condition. The study shows that music is a powerful elicitor of emotion and that using nonlinear method can potentially contribute to the investigation of emotion. 相似文献
100.
Canonical correlation analysis based on information theory 总被引:2,自引:0,他引:2
In this article, we propose a new canonical correlation method based on information theory. This method examines potential nonlinear relationships between p×1 vector Y-set and q×1 vector X-set. It finds canonical coefficient vectors a and b by maximizing a more general measure, the mutual information, between aTX and bTY. We use a permutation test to determine the pairs of the new canonical correlation variates, which requires no specific distributions for X and Y as long as one can estimate the densities of aTX and bTY nonparametrically. Examples illustrating the new method are presented. 相似文献