全文获取类型
收费全文 | 90805篇 |
免费 | 2282篇 |
国内免费 | 3151篇 |
专业分类
化学 | 35199篇 |
晶体学 | 1030篇 |
力学 | 7223篇 |
综合类 | 210篇 |
数学 | 33171篇 |
物理学 | 19405篇 |
出版年
2024年 | 42篇 |
2023年 | 212篇 |
2022年 | 451篇 |
2021年 | 499篇 |
2020年 | 507篇 |
2019年 | 545篇 |
2018年 | 10801篇 |
2017年 | 10678篇 |
2016年 | 6638篇 |
2015年 | 1524篇 |
2014年 | 1148篇 |
2013年 | 1453篇 |
2012年 | 4954篇 |
2011年 | 11704篇 |
2010年 | 6578篇 |
2009年 | 6912篇 |
2008年 | 7607篇 |
2007年 | 9674篇 |
2006年 | 1064篇 |
2005年 | 1985篇 |
2004年 | 2103篇 |
2003年 | 2436篇 |
2002年 | 1463篇 |
2001年 | 660篇 |
2000年 | 619篇 |
1999年 | 416篇 |
1998年 | 381篇 |
1997年 | 274篇 |
1996年 | 325篇 |
1995年 | 234篇 |
1994年 | 182篇 |
1993年 | 173篇 |
1992年 | 112篇 |
1991年 | 122篇 |
1990年 | 113篇 |
1989年 | 84篇 |
1988年 | 96篇 |
1987年 | 75篇 |
1986年 | 85篇 |
1985年 | 70篇 |
1984年 | 62篇 |
1983年 | 52篇 |
1982年 | 48篇 |
1981年 | 44篇 |
1980年 | 51篇 |
1979年 | 49篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
994.
We investigate the face-to-face collision between multisolitons in spin-1/2 quantum plasma. It is studied in the framework of the model proposed by Marklund et al in Phys. Rev. E 76, 067401 (2007). This study is done with the help of the extended Poincare–Lighthill–Kno (PLK) method. The extended PLK method is also used to obtain two Korteweg–de Vries (KdV) equations and the phase shifts and trajectories during the head-on collision of multisolitons. The collision-induced phase shifts (trajectory changes) are also obtained. The effects of the Zeeman energy, total mass density of the charged plasma particles, speed of the wave and the ratio of the sound speed to Alfvén speed on the phase shifts are studied. It is observed that the phase shifts are significantly affected by all these parameters. 相似文献
995.
We study the junction condition relating the pressure to heat flux at the boundary of an accelerating and expanding spherically symmetric radiating star. We transform the junction condition to an ordinary differential equation by making a separability assumption on the metric functions in the space–time variables. The condition of separability on the metric functions yields several new exact solutions. A class of shear-free models is found which contains a linear equation of state and generalizes a previously obtained model. Four new shearing models are obtained; all the gravitational potentials can be written explicitly. A brief physical analysis indicates that the matter variables are well behaved. 相似文献
996.
In this paper we report a time-delayed chameleon-like chaotic system which can belong to different families of chaotic attractors depending on the choices of parameters. Such a characteristic of self-excited and hidden chaotic flows in a simple 3D system with time delay has not been reported earlier. Dynamic analysis of the proposed time-delayed systems are analysed in time-delay space and parameter space. A novel adaptive modified functional projective lag synchronization algorithm is derived for synchronizing identical time-delayed chameleon systems with uncertain parameters. The proposed time-delayed systems and the synchronization algorithm with controllers and parameter estimates are then implemented in FPGA using hardware–software co-simulation and the results are presented. 相似文献
997.
Although LiFePO4/C has been successfully put into practical use in lithium-ion batteries equipped on new energy vehicles, its unsatisfactory low temperature results in poor low performance of lithium-ion batteries, leading to a much smaller continue voyage course at extreme environments with low temperature for electric vehicles. In this paper, the electrochemical performance of the LiFePO4/C prepared by polyol route was investigated at a temperature range from 25 to ?20 °C. Compared to commercial ones, as-prepared LiFePO4/C shows a much better low-temperature performance with a reversible capacity of 30 mA h g?1 even at 5 C under ?20 °C and a capacity retention of 91.1 % after 100 cycles at 0.1 C under 0 °C. Moreover, high-resolution transmission electron microscopy (HRTEM) revealed that this outstanding performance at low temperatures could be assigned to uniform carbon coating and the nano-sized particles with a highly crystalline structure. 相似文献
998.
Bashir Ahmad Najla Alghamdi Ahmed Alsaedi Sotiris K. Ntouyas 《The European physical journal. Special topics》2017,226(16-18):3369-3390
In this paper, we discuss the existence and uniqueness of solutions for a new class of multi-point boundary value problems of multi-term fractional differential equations by using standard fixed point theorems. We also demonstrate the application of the obtained results with the aid of examples. The paper concludes with the study of multi-term fractional integro-differential equations supplemented with multi-point boundary conditions. Our results are new and contribute significantly to the existing literature on the topic. 相似文献
999.
1000.