全文获取类型
收费全文 | 3671篇 |
免费 | 465篇 |
国内免费 | 827篇 |
专业分类
化学 | 2145篇 |
晶体学 | 35篇 |
力学 | 586篇 |
综合类 | 76篇 |
数学 | 404篇 |
物理学 | 1717篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2020年 | 1篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 85篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 1篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2003年 | 324篇 |
2002年 | 1404篇 |
2001年 | 1193篇 |
2000年 | 370篇 |
1999年 | 289篇 |
1998年 | 227篇 |
1997年 | 60篇 |
1996年 | 115篇 |
1995年 | 170篇 |
1994年 | 112篇 |
1993年 | 151篇 |
1992年 | 107篇 |
1991年 | 92篇 |
1990年 | 125篇 |
1989年 | 104篇 |
1985年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有4963条查询结果,搜索用时 15 毫秒
91.
(Tm,Ho):YLF晶体激光器的实验研究 总被引:1,自引:1,他引:1
报道了一台连续792nmTi:Al2O3激光器纵向抽运的(Tm,Ho):YLF微片激光器。在室温条件下,当抽运功率为680mW时,激光器在2.06μm波长的输出功率达到90mW。激光器阈值为380mW,光光转换效率为13%,斜率效率为26%. 相似文献
92.
研究了结晶度对Ag11In12Te26Sb51相变薄膜光学常数的影响。用初始化仪使相变薄膜晶化,改变晶化参量得到不同的结晶度,当转速固定时,随激光功率的增加,折射率基本随之减小,消光系数先是增大,而后减小;当激光功率固定时,随转速的增大,折射率也随之增大,消光系数也是先增大后减小。非晶态与晶态间的变换、薄膜微结构的变化(包括晶型的转变和原子间键合状态的变化)以及薄膜内残余应力的影响Ag11In12Te26Sb51相变薄膜复数折射率的主要原因。测量了单层膜的透过率和CD-RW相变光盘中Ag11In12Te26Sb51薄膜非晶态和晶态的反射率。 相似文献
93.
对射频反应性溅射Cd-In合金靶制备的透明导电CdIn2O4薄膜,研究了基片温度及沉积后在氩气流中退火对薄膜的透射、反射和吸收光谱,光学常数和载流子浓度的影响。结果表明:提高基片温度减少了薄膜的载流子浓度,退火增加了薄膜的载流子浓度。随着基片温度提高,薄膜折射率n和消光系数κ的短波峰将逐渐蓝移,而退火使其出现红移。基片温度和退火对薄膜光学常数的影响与其对薄膜载流子浓度的影响是一致的。在制备CdIn2O4这样一种对于沉积方法和沉积条件极为敏感的透明导电薄膜的沉积过程中,这一现象对于实时监控具有极为重要的意义。 相似文献
94.
本文给出一种求解相容性线性方程组的并行迭代解法,并证明此方法对任意相容性线方程组收敛,同时还讨论了方法的加速技术。 相似文献
95.
Mixed symmetry states are studied in the framework of the neutron-proton interacting boson model.It is found that some of the mixed symmetry states with moderate high spins change very fast with respect to the Majorana interaction.Under certain conditions,they become the yrast state or yrare state.These states are difficult to decay and become very stable.This study suggests that a possible new mode of isomers may exist due to the special nature in their proton and neutron degrees of freedom. 相似文献
96.
In this second paper of a series of papers,we explore the difference discrete versions for the Euler-Lagrange cohomology and apply them to the symplectic or multisymplectic geometry and their preserving properties in both the Lagrangian and Hamiltonian formalisms for discrete mechanics and field theory in the framework of multiparameter differential approach.In terms of the difference discrete Euler-Lagrange cohomological concepts,we show that the symplectic or multisymplectic geometry and their difference discrete structure-preserving properties can always be established not only in the solution spaces of the discrete Euler-Lagrange or canonical equations erived by the difference discrete variational principle but also in the function space in each case if and only if the relevant closed Euler-Lagrange cohomological conditions are satisfied. 相似文献
97.
The decay process J/ψ→p X X→p P,where p,p and P are the proton,antiproton and pseudoscalar states,respectively,has been studied in terms of the angular distribution and the generalized moment analysis methods.The result shows that we can identify the spin,but cannot determine the parity of the baryon resonance state X produced in the process J/ψ→p X X→p P. 相似文献
98.
The adiabatic effective baryon-baryou interactions and dibaryon candidates are studied systematically with three constituent quark models based on different effective degrees of freedom:Glozman-Riska-Brown Goldstone boson exchange model based on constituent quark and Goldstone boson coupling;Fujiwara model based on constituent quark gluon coupling and Nijmegen one-boson exchange;QDCSM based on constituent quark and gluon coupling with quark delocalization and color screening.We find that the three models predicted the similar effective baryon-baryon interactions for roughly two thirds among the 64 states consisted of octet and decuplet baryons.The differences among three models and their separate characteristics are also studied. 相似文献
99.
The classical Molecular dynamics simulation has been used to study the equation of state of gas H2,D2 and T2.It has also been investigated that the isotope mass affects on the accuracy of equation of state.Our calculated Iesults show that the classical effect is principal and the isotope mass effects on the equation of state are obvious for the much light gases.At the same time,some useful theoretical data of equation of state for these gases have been provided.It is found that the classical simulation is still effective to the quantum gas.However,the quantum mechanics simulation and the improvement of intermolecular interaction potential are necessary if more accurate computational results are expected. 相似文献
100.
We study the quantum fluctuations of the charge and current of two L-C dissipative mesoscopic circuit with the mutual inductance in the vacuum state.Our results show that the system state will evolve to a squeezed coherent state under the effect of external source.We find that the squeezing amplitude parameter is relative to the parameters of circuit and the mutual-inductance coefficient in the existence of dissipation.When the circuit has no dissipation or there is complete coupling between two meshes,the squeezing amplitude parameter only depends on the capacitance‘s ratio. 相似文献