全文获取类型
收费全文 | 332189篇 |
免费 | 3531篇 |
国内免费 | 953篇 |
专业分类
化学 | 166484篇 |
晶体学 | 5392篇 |
力学 | 15588篇 |
综合类 | 7篇 |
数学 | 38998篇 |
物理学 | 110204篇 |
出版年
2021年 | 3186篇 |
2020年 | 3396篇 |
2019年 | 3821篇 |
2018年 | 5256篇 |
2017年 | 5487篇 |
2016年 | 7485篇 |
2015年 | 4243篇 |
2014年 | 7143篇 |
2013年 | 16103篇 |
2012年 | 12548篇 |
2011年 | 15010篇 |
2010年 | 11147篇 |
2009年 | 11043篇 |
2008年 | 13395篇 |
2007年 | 13344篇 |
2006年 | 12255篇 |
2005年 | 10627篇 |
2004年 | 9917篇 |
2003年 | 8749篇 |
2002年 | 8746篇 |
2001年 | 10420篇 |
2000年 | 7689篇 |
1999年 | 5990篇 |
1998年 | 4990篇 |
1997年 | 4832篇 |
1996年 | 4507篇 |
1995年 | 3888篇 |
1994年 | 3841篇 |
1993年 | 3716篇 |
1992年 | 4119篇 |
1991年 | 4318篇 |
1990年 | 4113篇 |
1989年 | 4020篇 |
1988年 | 3795篇 |
1987年 | 3929篇 |
1986年 | 3692篇 |
1985年 | 4641篇 |
1984年 | 4701篇 |
1983年 | 3898篇 |
1982年 | 3986篇 |
1981年 | 3706篇 |
1980年 | 3659篇 |
1979年 | 3922篇 |
1978年 | 3920篇 |
1977年 | 3923篇 |
1976年 | 3888篇 |
1975年 | 3680篇 |
1974年 | 3617篇 |
1973年 | 3651篇 |
1972年 | 2603篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
134.
Ieva
Dauickait Amos S. Lawless Jennifer A. Scott Peter Jan van Leeuwen 《Numerical Linear Algebra with Applications》2020,27(5)
We consider the large sparse symmetric linear systems of equations that arise in the solution of weak constraint four‐dimensional variational data assimilation, a method of high interest for numerical weather prediction. These systems can be written as saddle point systems with a 3 × 3 block structure but block eliminations can be performed to reduce them to saddle point systems with a 2 × 2 block structure, or further to symmetric positive definite systems. In this article, we analyse how sensitive the spectra of these matrices are to the number of observations of the underlying dynamical system. We also obtain bounds on the eigenvalues of the matrices. Numerical experiments are used to confirm the theoretical analysis and bounds. 相似文献
135.
136.
Gelikonov G. V. Ksenofontov S. Yu. Shilyagin P. A. Gelikonov V. M. 《Radiophysics and Quantum Electronics》2019,62(3):228-236
Radiophysics and Quantum Electronics - We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in... 相似文献
137.
A.G. Rousskikh A.V. Fedyunin A.P. Artyomov A.S. Zhigalin V.I. Oreshkin 《Current Applied Physics》2019,19(6):704-708
The aim of the study presented in this paper was to characterize quantitatively the erosion of aluminum cathodes in high-current vacuum arcs. The experimental setup comprised two current generators. The first one, capable of generating a current of amplitude up to 350 kA, was used to produce a plasma jet, that is, the object to be investigated. The second generator was used to produce a source of probe radiation for imaging the object under investigation in soft x rays of energy ?ν ≈ 0.5–3 keV. The findings of the study are based on experimental data obtained by electrophysical and radiographic methods. It has been shown that the cathode erosion rate in a high-current vacuum arc is a function of the charge passed through the cathode. 相似文献
138.
Nonlinear Dynamics - Introduction of stiffness nonlinearities to broaden the frequency bandwidth of vibratory energy harvesters has the adverse influence of complicating the response behavior of... 相似文献
139.
Synthesis,Electronic Properties and WOLED Devices of Planar Phosphorus‐Containing Polycyclic Aromatic Hydrocarbons 下载免费PDF全文
Dr. François Riobé Rózsa Szűcs Dr. Pierre‐Antoine Bouit Dr. Denis Tondelier Bernard Geffroy Fátima Aparicio Julia Buendía Prof. Luis Sánchez Prof. Régis Réau Prof. László Nyulászi Prof. Muriel Hissler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6547-6556
We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P‐containing PAHs exhibit properties expected for an emitter in white organic light‐emitting diodes (WOLEDs). 相似文献