全文获取类型
收费全文 | 28154篇 |
免费 | 4828篇 |
国内免费 | 4311篇 |
专业分类
化学 | 21796篇 |
晶体学 | 365篇 |
力学 | 1404篇 |
综合类 | 394篇 |
数学 | 3371篇 |
物理学 | 9963篇 |
出版年
2024年 | 64篇 |
2023年 | 552篇 |
2022年 | 790篇 |
2021年 | 890篇 |
2020年 | 1134篇 |
2019年 | 1166篇 |
2018年 | 932篇 |
2017年 | 835篇 |
2016年 | 1356篇 |
2015年 | 1400篇 |
2014年 | 1626篇 |
2013年 | 2133篇 |
2012年 | 2477篇 |
2011年 | 2591篇 |
2010年 | 1885篇 |
2009年 | 1757篇 |
2008年 | 1931篇 |
2007年 | 1780篇 |
2006年 | 1691篇 |
2005年 | 1530篇 |
2004年 | 1161篇 |
2003年 | 1032篇 |
2002年 | 1091篇 |
2001年 | 878篇 |
2000年 | 706篇 |
1999年 | 606篇 |
1998年 | 458篇 |
1997年 | 411篇 |
1996年 | 418篇 |
1995年 | 340篇 |
1994年 | 310篇 |
1993年 | 264篇 |
1992年 | 204篇 |
1991年 | 175篇 |
1990年 | 132篇 |
1989年 | 129篇 |
1988年 | 87篇 |
1987年 | 68篇 |
1986年 | 55篇 |
1985年 | 63篇 |
1984年 | 51篇 |
1983年 | 31篇 |
1982年 | 25篇 |
1981年 | 19篇 |
1980年 | 17篇 |
1979年 | 4篇 |
1977年 | 5篇 |
1973年 | 5篇 |
1957年 | 8篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Under the dielectric continuum model and Loudon’s uniaxial crystal model, the properties of the quasi-confined (QC) optical phonon dispersions and the electron-QC phonons coupling functions in a cylindrical wurtzite nanowire are deduced via the method of electrostatic potential expanding. Numerical computations on a GaN/Al0.15Ga0.85N wurtzite nanowire are performed. Results reveal that, for a definite axial wave number kz and a certain azimuthal quantum number m, there are infinite branches of QC modes. The frequencies of these QC modes fall into two regions, i.e. a high frequency region and a low frequency region. The dispersion of the QC modes are quite apparant only when kz and m are small. The lower-order QC modes in the higher frequency region play more important role in the electron-QC phonon interactions. Moreover, for the higher-order QC modes in the high frequency region, the electrostatic potentials “escaping” out of the well-layer material nearly could be ignored. 相似文献
102.
求解非线性方程的一个新方法 总被引:2,自引:0,他引:2
张艺 《宁波大学学报(理工版)》2002,15(3):55-57
提出了一种求解非线性方程的数值方法,此方法不需要导数的计算,其收敛阶与抛物线法相同,但计算量要比抛物线法小得多。 相似文献
103.
The plastic deformation field near the horizontal surface of a half space of perfectly plastic material associated with an indenting rotating rigid tooth is studied using slip line theory. The tooth is one of many on a roll surface and indents first into the half-space material and then rotates about the roll center. A slip line field is proposed for the deforming plastic region and a solution scheme is outlined. The emphasis is on determining the shape of the deforming region, especially that of the free surface. The study has a potential application in roughness transfer in metal forming processing. 相似文献
104.
对Sn-C60薄膜进行紫外可见光吸收,X-射线衍射和扫描电镜的测定结果显示,薄膜样品紫外可见光吸收的两个短波段吸收峰比纯C60薄膜的吸收峰显著下降,说明Sn-C60薄膜的电子光吸收跃迁为间接跃迁,能带中有杂质能级的存在;样品的X射线衍射峰则对应于面心立方结构;扫描电镜结果显示薄膜为纳米级颗粒组成。 相似文献
105.
我国医疗费用增长与医疗设备投入的相关性研究 总被引:3,自引:0,他引:3
近年来我国卫生总费用占GDP的比例增长很快,而在卫生费用结构上则发生政府投入下降和个人支出的上升。本文采集了大量的统计数据,采用统计相关性研究的方法,论证了医疗设备规模的不断扩大是导致医疗费用上升的主要因素之一;医疗设备的快速增长与医院维修费用投入的增长直接相关,而引起医疗设备维修大量投入的主要原因则是故障期内医疗设备的非正常闲置。本文通过对个人卫生费用的上升、医疗设备规模的扩大及其医疗设备维修投入费用增加相关性的分析,说明了在这种关系下,十分有必要研究医院医疗设备维修体系,以在卫生投入和患者权益上达到平衡。 相似文献
106.
We describe a scheme of stochastic implementations of quantum teleportation and entanglement swapping in terms of neutral kaons. In this scheme, the kaon whose state is to be teleported collides with one of the two entangled kaons in an Einstein–Podolsky–Rosen state. Subsequent detection of the outgoing particles of the collision completes the two-qubit projection on Alice side. There appear novel features, which connects quantum information science with fundamental laws of particle physics. 相似文献
107.
108.
Zhijun Yi Tingyu LiuQiren Zhang Yuanyuan Sun 《Journal of Electron Spectroscopy and Related Phenomena》2006
The electronic structures of PbWO4 crystals containing F type color centers with the lattice structure optimized are studied within the framework of the fully relativistic self-consistent Direc–Slater theory, using a numerically discrete variational (DV-Xα) method. The calculated results show that F and F+ centers have donor energy level in forbidden band. Their optical transition energy are 1.84 eV, 2.21 eV, respectively, which corresponds to the 680 nm, 550 nm absorption bands. It predicts that the 680 nm, 550 nm absorption bands originate form the F and F+ centers in PbWO4 crystals. 相似文献
109.
We propose a weighted evolving network model in which the underlying topological structure is still driven by the degree according to the preferential attachment rule while the weight assigned to the newly established edges is dependent on the degree in a nonlinear form. By varying the parameter a that controls the function determining the assignment of weight, a wide variety of power-law behaviours of the total weight distributions as well as the diversity of the weight distributions of edges are displayed. Variation of correlation and heterogeneity in the network is illustrated as well. 相似文献
110.
Cao H. P. Chen G. Grechkoseeva M. A. Mazurov V. D. Shi W. J. Vasil'ev A. V. 《Siberian Mathematical Journal》2004,45(6):1031-1035
The spectrum of a finite group is the set of its element orders. A finite group G is said to be recognizable by spectrum, if every finite group with the same spectrum as G is isomorphic to G. The purpose of the paper is to prove that for every natural m the finite simple Chevalley group F
4(2
m
) is recognizable by spectrum. 相似文献