全文获取类型
收费全文 | 1006篇 |
免费 | 33篇 |
国内免费 | 3篇 |
专业分类
化学 | 598篇 |
晶体学 | 7篇 |
力学 | 29篇 |
数学 | 80篇 |
物理学 | 328篇 |
出版年
2023年 | 16篇 |
2022年 | 22篇 |
2021年 | 28篇 |
2020年 | 30篇 |
2019年 | 30篇 |
2018年 | 25篇 |
2017年 | 24篇 |
2016年 | 33篇 |
2015年 | 15篇 |
2014年 | 35篇 |
2013年 | 53篇 |
2012年 | 49篇 |
2011年 | 61篇 |
2010年 | 37篇 |
2009年 | 35篇 |
2008年 | 57篇 |
2007年 | 54篇 |
2006年 | 53篇 |
2005年 | 40篇 |
2004年 | 41篇 |
2003年 | 35篇 |
2002年 | 18篇 |
2001年 | 20篇 |
2000年 | 15篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 14篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1933年 | 3篇 |
排序方式: 共有1042条查询结果,搜索用时 15 毫秒
71.
M.N.K. Chowdhury M.W. Khan M.F. Mina M.D.H. Beg Maksudur R. Khan A.K.M.M. Alam 《Radiation Physics and Chemistry》2012,81(10):1606-1611
Grafting of styrene/maleic anhydride and methyl methacrylate/maleic anhydride binary monomers onto the low density polyethylene film was performed using the γ-ray irradiation technique. Then, the synthesized grafted films were treated with different ammonia derivatives for developing chelating functionalization. These chelating products were characterized by the gravimetric method as well as by the Fourier transformed infrared spectroscopic method, and were used for removal of arsenic and some heavy metals from aqueous solutions. The optimum absorbed dose of 30 kGy reveals the graft yielding of about 325% in the films. Uptake of arsenic and some heavy-metal ions (Cr(III), Mn(II), Fe(III), Ni(II), Cu(II) and Pb(II)) from contaminated water by the chelating functionalized films (CFF) was examined by an atomic absorption spectrophotometer. The maximum arsenic removal capacity of 5062 mg/kg has been observed for the film treated with hydroxylamine hydrochloride. The CFF prepared by semicarbazide and thiol analogs show affinity toward the metal ions with an order: Cu(II)>Fe(III)>Mn(II) etc. The results obtained from this study indicate that the functionalized films show good chelating and ion-exchange property for metal ions. 相似文献
72.
73.
74.
Chowdhury Debasruti Bose Navonil Ghosh Dipankar Basu Mousumi 《Optical and Quantum Electronics》2017,49(9):1-12
Optical and Quantum Electronics - The nonlinear scattering of two non-collinear Gaussian pulses with different central frequencies and lengths, incident on the periodic stacks of semiconductor... 相似文献
75.
A. Chowdhury C. I. Christov 《Numerical Methods for Partial Differential Equations》2010,26(5):1125-1145
The temperature distribution around two spheres is considered when the main field has a constant gradient at infinity. Bispherical coordinates are used, together with a transformation of the dependent variable that leads to separation of variables. Then the solution can be sought in Legendre series with respect to one of the bispherical coordinates. An important element of the proposed work is the effective way to reduce an essentially 3D problem to a set of three 2D problems. The Legendre spectral method is shown to have an exponential convergence which is confirmed by the computations. The efficiency is so high that even for the hard cases of two closely situated spheres, an accuracy of 10?10 is achieved with as few as 20 terms in the expansion. Solutions with both longitudinal and transverse gradients at infinity are obtained, and the contour lines of the temperature field are presented graphically. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010 相似文献
76.
The well-characterized, monodispersed nature of reverse micelles formed by sodium bis(2-ethylhexyl)sulfosuccinate/heptane and their usefulness in approximating a membrane-like environment have been exploited to investigate the effect of pH and water pool size on the photophysical properties of hypericin (Hyp). Our measurements reveal two titratable groups of pKa approximately 1.5 and approximately 12.5. These are assigned to the HypH+/Hyp equilibrium (the deprotonation of a carbonyl group) and the Hyp-/Hyp2- equilibrium (the deprotonation of a peri hydroxyl group). The low-energy absorbance maxima of HypH+, of Hyp and Hyp- and of Hyp2- are 583, 594 and 613 nm, respectively. Neither at pH 13 nor at 1 M HCl is the system entirely in the Hyp2- or the HypH+ forms. Ours is the first study of Hyp in reverse micelles as well as the first time-resolved study of Hyp as a function of pH. 相似文献
77.
Summary We have derived a modified cylindrical K-dV (MCK-dV) equation for an ion-acoustic wave in a warm plasma with two-temperature
electrons, in a cylindrical geometry, near the critical density where the nonlinearity of the usual CK-dV vanishes. The solitary-wave
solution of MCK-dV is then discussed analytically using the concept of adiabatic invariants and the basic theorem due to Lax,
instead of any numerical evaluation. This modulated form of the solitary wave is then discussed graphically as regards its
variation with respect to the change in concentration of law- and high-temperature electrons. 相似文献
78.
An investigation is made of the influence of band non-parabolicity on the relation between the Fermi energies in the presence and absence of magnetic quantization in degenerate semi-conductors through derivation of a simplified form of the relation.On leave of absence from theDept. of Physics, B. N. College, Patna University, Patna 800004. 相似文献
79.
A. N. Chakravarti A. K. Chowdhury K. P. Ghatak D. R. Choudhury 《Czechoslovak Journal of Physics》1980,30(10):1161-1166
An expression is derived for the diffusivity-mobility ratio of the carriers in n-channel inversion layers on semiconductors like the ternary compounds which have strongly non-parabolic energy bands. The dependence of the ratio on alloy composition is also studied under the weak-field limit taking n-channel Hg1–xCdx.Te as an example.On leave of absence fromthe Department of Physics, Patna University, Patna, India. 相似文献
80.
We have obtained the inverse scattering equations associated with a new pair of coupled nonlinear evolution equations in two dimensions. The spectral parameter is introduced by invoking the invariance of the equation set, and imposing those on the Lax pair. 相似文献