全文获取类型
收费全文 | 4038篇 |
免费 | 110篇 |
国内免费 | 14篇 |
专业分类
化学 | 2690篇 |
晶体学 | 97篇 |
力学 | 121篇 |
数学 | 335篇 |
物理学 | 919篇 |
出版年
2023年 | 32篇 |
2022年 | 82篇 |
2021年 | 76篇 |
2020年 | 97篇 |
2019年 | 96篇 |
2018年 | 72篇 |
2017年 | 68篇 |
2016年 | 106篇 |
2015年 | 103篇 |
2014年 | 135篇 |
2013年 | 305篇 |
2012年 | 263篇 |
2011年 | 292篇 |
2010年 | 148篇 |
2009年 | 147篇 |
2008年 | 246篇 |
2007年 | 216篇 |
2006年 | 170篇 |
2005年 | 139篇 |
2004年 | 113篇 |
2003年 | 76篇 |
2002年 | 77篇 |
2001年 | 55篇 |
2000年 | 35篇 |
1999年 | 28篇 |
1998年 | 32篇 |
1997年 | 26篇 |
1996年 | 35篇 |
1995年 | 38篇 |
1994年 | 40篇 |
1993年 | 43篇 |
1992年 | 39篇 |
1991年 | 20篇 |
1990年 | 24篇 |
1989年 | 29篇 |
1988年 | 29篇 |
1987年 | 40篇 |
1986年 | 36篇 |
1985年 | 41篇 |
1984年 | 42篇 |
1983年 | 42篇 |
1982年 | 42篇 |
1981年 | 39篇 |
1980年 | 31篇 |
1979年 | 41篇 |
1978年 | 49篇 |
1977年 | 33篇 |
1976年 | 27篇 |
1974年 | 26篇 |
1973年 | 20篇 |
排序方式: 共有4162条查询结果,搜索用时 0 毫秒
61.
When a crystal is fractured impulsively by the impact of a moving piston, then initially the mechanoluminescence (ML) intensity increases quadratically with time, attains a peak value and later on it decreases with time. Considering that the solid state ML and gas discharge ML are excited due to the charging and subsequent production of electric field near the tip of moving cracks, expressions are derived for the transient ML intensity I, time tm and intensity Im corresponding to the peak of ML intensity versus time curve, respectively, the total ML intensity IT, and for fast and slow decays of the ML intensity. It is shown that the decay time for the fast decrease of the ML intensity after tm, is related to the decay time of the strain rate of crystals, and the decay time of slow decay of ML, only observed in phosphorescent crystals, is equal to the decay time of phosphorescence. The value of tm decreases with the increasing impact velocity, Im increases with the increasing impact velocity, and IT initially increases and then it tends to attain a saturation value for higher values of the impact velocity. The values of tm, Im and IT increase linearly with the thickness, area of cross-section and volume of the crystals, respectively. So far as the rise, attainment of ML peak, and fast decay of ML are concerned, there is no any significant difference in the time-evolution of solid state ML, gas discharge ML, and the ML emission consisting of both the solid state ML and gas discharge ML. From the time-dependence of ML, the values of the time-constant for decrease of the surface area created by the movement of a single crack, the time-constant for the decrease of strain rate of crystals, and the decay time of phosphorescence of crystals can be determined. A good agreement is found between the theoretical and experimental results. The importance of fracto ML induced by impulsive deformation of crystals is discussed. 相似文献
62.
63.
Physics of the Solid State - Using ab initio technique the physical properties of ScIr2 superconductor have been investigated with Tc 1.03 K with a MgCu2-type structure. We have carried out the... 相似文献
64.
65.
S. K. Chandra 《Czechoslovak Journal of Physics》1973,23(6):589-593
The perturbation method of Lindstedt is applied to study the non linear effect of a nonlinear equation $$\nabla ^2 {\rm E} - \frac{1}{{c^2 }}\frac{{\partial ^2 {\rm E}}}{{\partial t^2 }} - \frac{{\omega _0^2 }}{{c^2 }}{\rm E} + \frac{{2v}}{{c^2 }}\frac{{\partial {\rm E}}}{{\partial t}} + E^2 \left[ {\frac{{\partial {\rm E}}}{{\partial t}} \times A} \right] = 0,$$ where (A. E)=0 andA,c, ω 0 andν are constants in space and time. Amplitude dependent frequency shifts and the solution up to third order are derived. 相似文献
66.
The sharp gradient in the intensity of a surface wave over a simiconductor-vacuum interface gives rise to a strong ponderomotive force on electrons and thus generates a second harmonic wave. The power of the second harmonic shows a resonance at (ω and ωp being the wave and plasma frequencies) and tends to a saturation value at very high values of ωp. 相似文献
67.
K. Shahi Nitish K. Sanyal S. Chandra 《Journal of Physics and Chemistry of Solids》1975,36(12):1349-1352
Thermoelectric power using reversible silver electrodes and electrical conductivity on the compressed pellets of (Me4N)2Ag13I15, and (Et4N)2Ag13I15 have been measured between room temperature and below 160°C. The results of θ can be expressed by the equations:?θ = 0.115 (103/T)+0.2905VK?1 and ?θ = 0.150 (103/T) + 0.305mV K?1; and those of conductivity by the equations; σ = 28.7 exp (?0.17eV/kT) ohm?1cm?1 and ohm?1cm?1; respectively for Me- and Et-electrolytes. The results are discussed and compared with those of previous authors. 相似文献
68.
Electron spin resonance studies have been carried out on Cu2+ ion doped in single crystals of cadmium maleate dihydrate at 303 and 77K. It has been found that Cu2+ enters this lattice interstitially. The spin Hamiltonian parameters have been evaluated and the ground state wave function
is found to be predominantly |X
2 −Y
2〉 with a slight admixture of |3Z
2 −r
2〉. 相似文献
69.
The coefficient of variation is an important parameter in many physical, biological and medical sciences. In this paper we study the estimation of the square of the coefficient of variation in a weighted inverse Gaussian model which is a mixture of the inverse Gaussian and the length biased inverse Gaussian distribution. This represents a rich family of distributions for different values of the mixing parameter and can be used for modelling various life testing situations. The maximum likelihood as well as the Bayes estimates of the parameters are obtained. These estimates are used to derive the estimates of the square of the coefficient of variation of the model under study. Several important data sets are analysed to illustrate the results. © 1996 John Wiley & Sons, Ltd. 相似文献
70.