全文获取类型
收费全文 | 3521篇 |
免费 | 475篇 |
国内免费 | 164篇 |
专业分类
化学 | 348篇 |
晶体学 | 5篇 |
力学 | 110篇 |
综合类 | 148篇 |
数学 | 1391篇 |
物理学 | 2158篇 |
出版年
2024年 | 8篇 |
2023年 | 31篇 |
2022年 | 272篇 |
2021年 | 253篇 |
2020年 | 133篇 |
2019年 | 102篇 |
2018年 | 75篇 |
2017年 | 130篇 |
2016年 | 161篇 |
2015年 | 115篇 |
2014年 | 203篇 |
2013年 | 214篇 |
2012年 | 152篇 |
2011年 | 198篇 |
2010年 | 192篇 |
2009年 | 204篇 |
2008年 | 204篇 |
2007年 | 227篇 |
2006年 | 178篇 |
2005年 | 164篇 |
2004年 | 134篇 |
2003年 | 119篇 |
2002年 | 92篇 |
2001年 | 75篇 |
2000年 | 56篇 |
1999年 | 41篇 |
1998年 | 46篇 |
1997年 | 39篇 |
1996年 | 32篇 |
1995年 | 48篇 |
1994年 | 38篇 |
1993年 | 18篇 |
1992年 | 15篇 |
1991年 | 17篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 18篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1976年 | 5篇 |
1974年 | 4篇 |
1972年 | 4篇 |
排序方式: 共有4160条查询结果,搜索用时 15 毫秒
31.
We extend an optimal entanglement distillation of the triplet Greenberger-Horne-Zeilinger (GHZ) state via entanglement concentrating in the three-partite partially electron-spin-entangled systems. Two entanglement concen- tration protocols are similarly designed in detail with the post-selection in quantum-dot (QD) and micro-cavity coupled systems. The proposed protocol can be repeated several rounds to achieve an optimal success probability with an as- sistance of the ancillary QD, where only the single photon needs to pass through the micro-cavity for each round. It increases the total success probability of the distillation even if the implemented cavity is imperfect in practice during the whole process. 相似文献
32.
Effects of information asymmetry on cooperation in the prisoners’ dilemma game are investigated. The amplitude A is introduced to describe the degree of information asymmetry. It is found that there exists an optimal value of amplitude Aopt at which the fraction of cooperation reaches its maximal value. The reason lies in that cooperators on the two-dimensional grid form large clusters at Aopt . In addition, the theoretical analysis in terms of the meanfield theory is used to understand this kind of phenomenon. It is confirmed that the information asymmetry plays an important role in the dynamics of the dilemma games of spatial prisoners. 相似文献
33.
数字全息图在微电路检测、粒度分析、透明场测量等小孔径、小视场对象测量和细胞观测等显微测量方面有着广泛的应用前景。根据离轴数字全息图的频谱特点,提出采用复数滤波器,利用计算机及相关算法对离轴数字全息图进行滤波,消除其零级及共轭像,同时可以得到全息图的相位分布。讨论了复数滤波器的设计方法,给出了实验结果。为数字全息图的压缩、再现和相息图制作提供了方便。 相似文献
34.
分别利用空间和光纤马赫—曾德尔干涉仪对空间和光纤传输中的单个光子的干涉现象进行了研究,干涉对比度可达到90%以上,实现了空间和光纤中的单个光子的路由操控。实验采用脉冲调制加衰减的方法产生单个光子,获得了每个脉冲中只包含0.1个光子的准单光子源。通过改变压电换能器的电压控制马赫—曾德尔干涉仪的单个光子在两个输出端的选择,实现了光子在节点上的路由。采用同步符合检测技术,利用重复频率为1kHz,脉冲宽度为100ns的同步信号对输出信号进行符合,实现了量子效率高于70%,暗计数小于0.2s^-1的单光子高灵敏度检测,观测到了单个光子在相位操控下出射到两个输出端的有序分配现象。验证了基于马赫—曾德尔干涉仪的单个光子路由操控实现的可能性。 相似文献
35.
36.
37.
38.
Takuya Yamano 《Entropy (Basel, Switzerland)》2021,23(3)
An electron in a constant magnetic field has energy levels, known as the Landau levels. One can obtain the corresponding radial wavefunction of free-electron Landau states in cylindrical polar coordinates. However, this system has not been explored so far in terms of an information-theoretical viewpoint. Here, we focus on Fisher information associated with these Landau states specified by the two quantum numbers. Fisher information provides a useful measure of the electronic structure in quantum systems, such as hydrogen-like atoms and under some potentials. By numerically evaluating the generalized Laguerre polynomials in the radial densities, we report that Fisher information increases linearly with the principal quantum number that specifies energy levels, but decreases monotonically with the azimuthal quantum number m. We also present relative Fisher information of the Landau states against the reference density with , which is proportional to the principal quantum number. We compare it with the case when the lowest Landau level state is set as the reference. 相似文献
39.
A linear optical unambiguous discrimination of hyperentangled Bell states is proposed for two‐photon systems entangled in both the polarization and momentum degrees of freedom (DOFs) assisted by time bin. This unambiguous discrimination scheme can completely identify 16 orthogonal hyperentangled Bell states using only linear optical elements, where the function of the auxiliary entangled Bell state is replaced by time bin. Moreover, the possibility of extending this scheme for distinguishing hyperentangled Bell states in n DOFs is discussed, and it shows that hyperentangled Bell states in n ( ) DOFs can be distinguished with k ( ) auxiliary entangled states of additional DOFs by introducing a time delay, which decreases the auxiliary entanglement resource required for unambiguous discrimination of hyperentangled Bell state. Therefore, this scheme provides a new way for distinguishing hyperentangled states with current technology, which will extend the application of discrimination of hyperentangled states via linear optics to other quantum information protocols besides hyperdense coding schemes in the future. 相似文献
40.