全文获取类型
收费全文 | 15223篇 |
免费 | 771篇 |
国内免费 | 74篇 |
专业分类
化学 | 11021篇 |
晶体学 | 43篇 |
力学 | 368篇 |
数学 | 2336篇 |
物理学 | 2300篇 |
出版年
2023年 | 117篇 |
2022年 | 163篇 |
2021年 | 250篇 |
2020年 | 346篇 |
2019年 | 369篇 |
2018年 | 187篇 |
2017年 | 199篇 |
2016年 | 523篇 |
2015年 | 578篇 |
2014年 | 597篇 |
2013年 | 833篇 |
2012年 | 1147篇 |
2011年 | 1153篇 |
2010年 | 715篇 |
2009年 | 628篇 |
2008年 | 907篇 |
2007年 | 876篇 |
2006年 | 838篇 |
2005年 | 791篇 |
2004年 | 682篇 |
2003年 | 533篇 |
2002年 | 502篇 |
2001年 | 247篇 |
2000年 | 202篇 |
1999年 | 185篇 |
1998年 | 196篇 |
1997年 | 194篇 |
1996年 | 157篇 |
1995年 | 138篇 |
1994年 | 129篇 |
1993年 | 126篇 |
1992年 | 105篇 |
1991年 | 106篇 |
1990年 | 83篇 |
1989年 | 99篇 |
1988年 | 70篇 |
1987年 | 52篇 |
1986年 | 53篇 |
1985年 | 68篇 |
1984年 | 67篇 |
1983年 | 59篇 |
1982年 | 63篇 |
1981年 | 74篇 |
1980年 | 62篇 |
1979年 | 77篇 |
1978年 | 64篇 |
1977年 | 63篇 |
1976年 | 68篇 |
1975年 | 53篇 |
1973年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
91.
92.
93.
Johann Guilleminot Christian Soize Djimedo Kondo Christophe Binetruy 《International Journal of Solids and Structures》2008,45(21):5567-5583
Many engineering materials exhibit fluctuations and uncertainties on their macroscopic mechanical properties. This randomness results from random fluctuations observed at a lower scale, especially at the meso-scale where microstructural uncertainties generally occur. In the present paper, we first propose a complete theoretical stochastic framework (that is, a relevant probabilistic model as well as a non-intrusive stochastic solver) in which the volume fraction at the microscale is modelled as a random field whose statistical reduction is performed using a Karhunen–Loeve expansion. Then, an experimental procedure dedicated to the identification of the parameters involved in the probabilistic model is presented and relies on a non-destructive ultrasonic method. The combination of the experimental results with a micromechanical analysis provides realizations of the volume fraction random field. In particular, it is shown that the volume fraction can be modelled by a homogeneous random field whose spatial correlation lengths are determined and may provide conditions on the size of the meso-volumes to be considered. 相似文献
94.
95.
Christian Hainzl Vitali Vougalter Semjon A. Vugalter 《Communications in Mathematical Physics》2003,233(1):13-26
We consider a spinless particle coupled to a photon field and prove that even if the Schr?dinger operator p
2
+V does not have eigenvalues the system can have a ground state. We describe the coupling by means of the Pauli-Fierz Hamiltonian
and our result holds in the case where the coupling constant α is small.
Received: 7 January 2002 / Accepted: 8 November 2002 Published online: 13 January 2003 相似文献
96.
The sound propagation into a courtyard shielded from direct exposure is predicted using an equivalent sources approach. The problem is simplified into that of a two-dimensional city canyon. A set of equivalent sources are used to couple the free half-space above the canyon to the cavity inside the canyon. Atmospheric turbulence causes an increase in the expected value of the sound pressure level compared to a homogeneous case. The level increase is estimated using a von Kármán turbulence model and the mutual coherences of all equivalent sources' contributions. For low frequencies the increase is negligible, but at 1.6 kHz it reaches 2-5 dB for the geometries and turbulence parameters used here. A comparison with a ray-based model shows reasonably good agreement. 相似文献
97.
Vladimir B. Arion Alexey A. Nazarov Christian G. Hartinger Gerald Giester Bernhard K. Keppler 《应用有机金属化学》2003,17(9):723-724
For the unsymmetrical title compound, 1‐bromo‐1′‐[(2S)‐N‐(1‐hydroxy‐3‐methylbutane‐2‐yl)]‐ferroceneamide, two independent molecules were found in the asymmetric unit. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
98.
99.