全文获取类型
收费全文 | 3628篇 |
免费 | 97篇 |
国内免费 | 2篇 |
专业分类
化学 | 2386篇 |
晶体学 | 39篇 |
力学 | 72篇 |
数学 | 259篇 |
物理学 | 971篇 |
出版年
2023年 | 37篇 |
2022年 | 62篇 |
2021年 | 61篇 |
2020年 | 90篇 |
2019年 | 105篇 |
2018年 | 69篇 |
2017年 | 59篇 |
2016年 | 128篇 |
2015年 | 73篇 |
2014年 | 122篇 |
2013年 | 238篇 |
2012年 | 238篇 |
2011年 | 292篇 |
2010年 | 176篇 |
2009年 | 146篇 |
2008年 | 216篇 |
2007年 | 181篇 |
2006年 | 162篇 |
2005年 | 140篇 |
2004年 | 110篇 |
2003年 | 75篇 |
2002年 | 75篇 |
2001年 | 60篇 |
2000年 | 57篇 |
1999年 | 46篇 |
1998年 | 29篇 |
1997年 | 23篇 |
1996年 | 38篇 |
1995年 | 29篇 |
1994年 | 35篇 |
1993年 | 43篇 |
1992年 | 29篇 |
1991年 | 27篇 |
1989年 | 19篇 |
1988年 | 21篇 |
1987年 | 27篇 |
1986年 | 21篇 |
1985年 | 19篇 |
1984年 | 31篇 |
1983年 | 20篇 |
1982年 | 22篇 |
1981年 | 30篇 |
1980年 | 19篇 |
1979年 | 27篇 |
1978年 | 16篇 |
1977年 | 18篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1973年 | 11篇 |
1957年 | 13篇 |
排序方式: 共有3727条查询结果,搜索用时 15 毫秒
31.
32.
33.
Effects of Hall current on a steady hydromagnetic (MHD) fully developed flow in a rotating environment within a parallel plate
channel in the presence of an inclined magnetic field is studied. From an extension of literature [13] subject to a forced
oscillation it is observed that the present paper is methodically more correct to work first in the steady state where forced
oscillation becomes insignificant and then new results are expected for an unsteady MHD flow under the influence of a pulse-oscillator.
Exact solutions of the governing equations are obtained in a closed form. The graphical representation for the velocity and
the induced magnetic field are depicted graphically and the heat transfer at both the plates are presented in tables. 相似文献
34.
Sadhan Ghosh 《Journal of magnetism and magnetic materials》2011,323(5):552-556
This work reports isothermal reversible variation of magnetization in nanoporous Pd-Ni alloys subjected to continuous charging and discharging of the sample in aprotic electrolyte medium. Polarizing metal surface with excess charge also finds strain in the nanoporous structure using the sample as working electrode. Therefore, it is proposed that pressure induced by strain is the key parameter for the observed reversible magnetization in the transition metal alloys. 相似文献
35.
We show that, when a turbid medium with a layered fluorophore distribution is excited by linearly polarized light, measurement of angle-resolved polarized fluorescence can provide depth-resolved fluorescence measurements. 相似文献
36.
Using an algebraic technique based on the Lie algebra of the group SO(2, 1) the eigenvalues of the triple-well anharmonic
oscillator are calculated for all ranges of the coupling constant. Approximate analytic formulas for the eigenvalues up to
second order are given. The results obtained are compared with those of other authors. 相似文献
37.
We present exact explicit expressions for the row spin-spin correlation functions
00
n0 in the isotropicd= 2 Ising model, in terms of elliptic integrals, forn 5. We also give a general structural formula for
00
n0. 相似文献
38.
S. K. Ghosh E. Tettamanti P. L. Indovina 《Zeitschrift für Physik B Condensed Matter》1976,24(2):227-233
Contributions to the spin-lattice relaxation time (T
1) and the spin-spin relaxation time (T
2) due to critical fluctuations (CF) have been determined in para-azoxyanisole (PAA) from the corresponding proton relaxation times measured at 60 MHz over a temperature range of about 35 °K above the nematic-isotropic transition temperatureT
C
.In determining the CF contributions, the procedure followed here is the same as the present authors used earlier for a similar study in p-methoxybenzylidene p-n butylaniline (MBBA). Like that in MBBA at 14 MHz, a maximum in the CF contribution toT
1, has been observed. Following a recent theory we identify this contribution toT
1 arising from the nonlocal part of CF, and we call thisT
1)CFN. The correlation time associated with this nonlocal part of CF,
CFN, has been determined at different temperatures fromT
1)CFN. The temperature dependence of
CFN is in good agreement with the Landau-de Gennes theory and is consistent with that observed earlier in MBBA. The temperature dependence ofT
2)CF is also in reasonable agreement with the above behavior of
CFN. However, ourT
2)CF data can also be fitted to a temperature dependence expected from a contribution toT
2)CF arising from the local part of CF, such a fitting is comparatively poorer than the former. Since ourT
2)CF data are neither sufficiently accurate nor elaborate, no attempt has been made here to separate these two contributions, nonlocal and local parts of CF, which have been predicted from theoretical considerations. A behavior similar to that of ourT
2)CF is also shown by the earlier data of Cabane and Clark obtained from14N resonance when their data are processed properly.Work done with the financial support of the Consiglio Nazionale delle Ricerche granted through the Gruppo Nazionale di Struttura della Materia to the Istituto di Fisica, Università dell' AquilaA preliminary report of this work was presented at the Fifth International Symposium on Magnetic Resonance held at Bombay, India, January 14–18, 1974 相似文献
39.
The fourth central moment of an X-ray diffraction profile from an aggregate of distorted crystallites has been expressed by
Mitra (1964a) as a function of the crystallite size, strain and strain gradients in the specimen. While the usual methods
of line profile analysis yield information regarding either the apparent strain or the rms strain, the present study provides
additional information regarding strain distribution in the form of strain derivatives and rms displacements of atoms over
a given distancet in the direction of study. The strain parameters like 〈ee′〉, 〈ee″〉 have been obtained from fourth moment of the strain profile against range plots. The strain parameters thus obtained have
subsequently been used to determine the rms displacements of the atoms. Alloys of copper and zinc at different stages of cold
working and annealing have been studied by this method. The results have been discussed in the light of dislocation distribution,
polygonisation and grain growth as well as distortion waves in the distorted crystals. 相似文献
40.
Rotational structure of a series of new absorption bands of PO in the region 1850 to 1600 Å has been analyzed from a spectrum taken at high resolution. The bands are attributed to an electronic transition P2Π-X2Π, where P2Π is a new valence state of PO. Some of these bands have been found to be perturbed. A qualitative account of these perturbations is presented. A probable electron-configuration has been suggested for the new state. From the predissociation observed in the higher vibrational levels of P an upper limit of 48 885 cm?1 (X2Π, T0 = 0) for the ground state dissociation energy has been obtained. 相似文献