全文获取类型
收费全文 | 46291篇 |
免费 | 9192篇 |
国内免费 | 10143篇 |
专业分类
化学 | 34541篇 |
晶体学 | 1105篇 |
力学 | 3146篇 |
综合类 | 1063篇 |
数学 | 5673篇 |
物理学 | 20098篇 |
出版年
2024年 | 129篇 |
2023年 | 734篇 |
2022年 | 1611篇 |
2021年 | 1620篇 |
2020年 | 1783篇 |
2019年 | 1888篇 |
2018年 | 1684篇 |
2017年 | 1879篇 |
2016年 | 2142篇 |
2015年 | 2485篇 |
2014年 | 3033篇 |
2013年 | 3870篇 |
2012年 | 4283篇 |
2011年 | 4456篇 |
2010年 | 3519篇 |
2009年 | 3686篇 |
2008年 | 3978篇 |
2007年 | 3472篇 |
2006年 | 3202篇 |
2005年 | 2612篇 |
2004年 | 2007篇 |
2003年 | 1602篇 |
2002年 | 1679篇 |
2001年 | 1480篇 |
2000年 | 1337篇 |
1999年 | 986篇 |
1998年 | 638篇 |
1997年 | 525篇 |
1996年 | 466篇 |
1995年 | 394篇 |
1994年 | 402篇 |
1993年 | 343篇 |
1992年 | 279篇 |
1991年 | 210篇 |
1990年 | 206篇 |
1989年 | 156篇 |
1988年 | 141篇 |
1987年 | 114篇 |
1986年 | 111篇 |
1985年 | 82篇 |
1984年 | 60篇 |
1983年 | 59篇 |
1982年 | 36篇 |
1981年 | 35篇 |
1980年 | 16篇 |
1979年 | 37篇 |
1978年 | 9篇 |
1977年 | 12篇 |
1957年 | 8篇 |
1925年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Jiang Tongsong Liu Yonghui Wei Musheng 《高校应用数学学报(英文版)》2006,21(1):113-118
This paper derives a theorem of generalized singular value decomposition of quaternion matrices (QGSVD),studies the solution of general quaternion matrix equation AXB -CYD= E,and obtains quaternionic Roth's theorem. This paper also suggests sufficient and necessary conditions for the existence and uniqueness of solutions and explicit forms of the solutions of the equation. 相似文献
132.
为了实验研究粲偶素ψ'级联衰变过程ψ'→γ'xcJ→γ'γJ/ψ,一个用于正确描述全部末态角分布的产生子是必要的.可以通过分析角分布的关联来确定这一过程的多极展开参数(或者等效的螺旋度振幅),而从中可以知道高阶电磁多极矩和相对论修正的贡献,同时可以检验ψ'是不是ψ'(2S)和ψ'(1D)的混合.介绍了一个能完全描述这一过程的角分布的产生子,同时讨论了测量多极参数的测量方法.这些都可以被用在BESⅢ或者CLEOc的分析当中. 相似文献
133.
For vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated feedback, there exist several synchronization
types such as synchronizations between total powers and synchronizations between separate polarization modes. Based on the
two-mode rate equations, we study and compare numerically the performances of different synchronization types. Our results
show that three synchronization types exhibit good performances when their synchronization conditions are satisfied. They
are the complete synchronization between total powers, complete synchronization between x-polarized modes, and generalized synchronization between x-polarized and y-polarized modes. The former two types are sensitive to the injection rate and spontaneous emission, while the third type
is contrary. Synchronization type with the best performance may switch from one to another, with changing of injection rate
and spontaneous emission factor. 相似文献
134.
135.
136.
1 Introduction Inrecentyears,boththetheoreticalandexperimentalinvestigationsonlasercoolingandtrappinghavebecomeoneofthemajorfieldsinatomic,molecularandoptical physics[1~ 8] .Thedevelopmentoflasercoolingandtrappingtechnologyisimportantfortheapplicationssu… 相似文献
137.
Investigation of remelting and cladding processing with laminar plasma jets on several metals has been conducted looking for possible development of a new surface modification technique. The remelting tests illustrated that the new method could evidently improve the material microstructure and properties of cast iron. The cladding was done with Al2O3 ceramic powder on stainless steel. The energy dispersive spectra (EDS) analysis was used to determine the distribution of the major cladding element in the plasma-processed layers, for which the microstructure observations and hardness measurements were also performed. 相似文献
138.
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
139.
The influence of the electron-LO-phonon coupling on energy spectrum of the low-lying states ofan exciton inparabolic quantum dots is investigated as a function of dot size. Calculations are made by using the method of few-bodyphysics within the effective-mass approximation. A considerable decrease of the energy in the stronger confinement rangeis found for the low-lying states of an exciton in quantum dots, which results from the confinement of electron-phononcoupling. 相似文献
140.
C.-S. Huang T. Li L. Wei Q.-S. Yan 《The European Physical Journal C - Particles and Fields》2002,23(1):195-199
It is shown that new sources of CP violation can be generated in models with more than one extra dimension. In the supersymmetric models on the space-time , where the radius moduli have auxiliary vacuum expectation values and the supersymmetry breaking is mediated by the Kaluza–Klein
states of the gauge supermultiplets, we analyze the gaugino masses and trilinear couplings for two scenarios and obtain the
result that there exist relative CP violating phases among the gaugino masses and trilinear couplings.
Received: 10 October 2001 / Published online: 20 December 2001 相似文献