全文获取类型
收费全文 | 195419篇 |
免费 | 31651篇 |
国内免费 | 22231篇 |
专业分类
化学 | 133137篇 |
晶体学 | 2280篇 |
力学 | 12584篇 |
综合类 | 1425篇 |
数学 | 25767篇 |
物理学 | 74108篇 |
出版年
2024年 | 204篇 |
2023年 | 3489篇 |
2022年 | 4130篇 |
2021年 | 6268篇 |
2020年 | 7454篇 |
2019年 | 7237篇 |
2018年 | 6534篇 |
2017年 | 6117篇 |
2016年 | 9107篇 |
2015年 | 8797篇 |
2014年 | 10966篇 |
2013年 | 14490篇 |
2012年 | 17323篇 |
2011年 | 18314篇 |
2010年 | 12701篇 |
2009年 | 12281篇 |
2008年 | 12994篇 |
2007年 | 11888篇 |
2006年 | 11056篇 |
2005年 | 9244篇 |
2004年 | 7118篇 |
2003年 | 5641篇 |
2002年 | 5201篇 |
2001年 | 4403篇 |
2000年 | 3875篇 |
1999年 | 4097篇 |
1998年 | 3518篇 |
1997年 | 3209篇 |
1996年 | 3213篇 |
1995年 | 2791篇 |
1994年 | 2619篇 |
1993年 | 2140篇 |
1992年 | 1919篇 |
1991年 | 1738篇 |
1990年 | 1396篇 |
1989年 | 1076篇 |
1988年 | 843篇 |
1987年 | 704篇 |
1986年 | 689篇 |
1985年 | 563篇 |
1984年 | 414篇 |
1983年 | 298篇 |
1982年 | 263篇 |
1981年 | 179篇 |
1980年 | 132篇 |
1979年 | 72篇 |
1978年 | 57篇 |
1976年 | 59篇 |
1975年 | 55篇 |
1974年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 991 毫秒
991.
本文在经典风险模型的基础上,将索赔到达过程推广为更新过程,索赔可以批量到达,且带有常数利息力和Brown运动干扰项,得到一个新的风险模型,运用Markov骨架过程的方法,得出盈余过程的瞬时分布和生存概率. 相似文献
992.
Xiaowei Sun Zijiang Liu Qifeng Chen Chengwei Wang 《Journal of Physics and Chemistry of Solids》2007,68(2):249-255
Molecular dynamics (MD) method is used to investigate the behavior of the pressure-volume-temperature (P-V-T) relationship, lattice constant and thermal expansivity for ZnO with rock-salt structure at high pressures and temperatures. The interionic potential is taken to be the sum of pair-wise additive Coulomb, van der Waals attraction, and repulsive interactions. The isothermal and isobaric properties are discussed from the corresponding P-V-T relationship, and it is shown that the MD simulation is successful in reproducing the measured volumes of ZnO over a wide range of temperature and pressure. Meanwhile, the equations of state parameters including lattice constant, linear thermal expansion coefficient, and isothermal bulk modulus are calculated and compared with the available experimental data and the latest theoretical results. At an extended pressure and temperature range, P-V-T relationship, lattice constant, and linear thermal expansion coefficient have been predicted. The structural and thermodynamic properties of ZnO with rock-salt structure are summarized in the pressure 0-100 GPa ranges and the temperature up to 3100 K. 相似文献
993.
A novel heath monitoring system of the rocket based on fiber optic Bragg gratings is brought forward, its component units and working principle are also described. 相似文献
994.
给出目标信息系统学习的多准则决策方法,建立多准则决策的规则学习模型,讨论该模型的性质。该模型优于Z.Pawlak方法,将规则提取与信息融合为一体。也优于AHP等模型,具有简洁性.通过实例计算,取得了满意结果。 相似文献
995.
996.
Single-crystalline layered lithium manganese oxide nanorods were prepared via a low-temperature molten salt synthesis method. The material was investigated by a variety of techniques, including X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS). 相似文献
997.
The first-principle was employed to study the six possible models for the Fe3O4(110) surface, namely the AB-terminated surface (AB model), the AB-terminated with FeA vacancy (AB-FeA vac model), the AB-terminated with FeB vacancy (AB-FeB vac model), the B-terminated surface (B model), the B-terminated surface with FeB vacancy (B-FeB vac model) and the B-terminated surface with O vacancy (B-O vac model). The stability, the electronic structure and the magnetic
properties of the six surface models were also calculated. The results predict that the B-O vac model is more stable than
other types of surface models. The half-metallic property remain in the AB and B models, while the other four surface models
exhibit metallic properties. At the same time, the AB, AB-FeA vac, AB-FeB vac, B and the B-FeB vac models have ferrimagnetic properties, while the B-O vac model has antiferromagnetic property.
相似文献
998.
Fabrication of bamboo-shaped GaN nanorods 总被引:1,自引:0,他引:1
H. Li J.Y. Li M. He X.L. Chen Z. Zhang 《Applied Physics A: Materials Science & Processing》2002,74(4):561-562
Bamboo-shaped GaN nanorods were formed through a simple sublimation method. They were characterized by means of X-ray powder
diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected-area
electron diffraction (SAED). The TEM image showed that the nanorods were bamboo-like. XRD, HRTEM and SAED patterns indicated
that the nanorods were single-crystal wurtzite GaN.
Received: 8 January 2001 / Accepted: 28 April 2001 / Published online: 20 December 2001 相似文献
999.
Controllability of Functional Integro-Differential Inclusions with an Unbounded Delay 总被引:1,自引:0,他引:1
In this paper, a sufficient condition is established for the controllability of neutral functional integro-differential inclusions
with an unbounded delay in Banach spaces. The approach used is a fixed-point theorem for condensing maps due to Martelli and
the theory of analytic semigroup of linear operators.
Communicated by F. Zirilli
Research supported by NNSF of China, by the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education
Institutions of the Ministry of Education of China, and by the Qing Lan Talent Engineering Fund QL-05-164 of Lanzhou Jiaotong
University. The authors are grateful to Professor F. Zirilli and two anonymous referees for valuable suggestions improving
this paper. 相似文献
1000.
Gu-Qiang Li 《Theoretical and Mathematical Physics》2007,151(1):586-589
We use the Parikh-Wilczek method to treat Hawking radiation as a tunneling process across the event horizon and calculate
the emission rate of a Gibbons-Maeda dilaton black hole. We show that if self-gravitation is taken into account, then the
radiation deviates from the purely thermal spectrum, and the corrected spectrum is consistent with an underlying unitary theory.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 151, No. 1, pp. 172–175, April, 2007. 相似文献