全文获取类型
收费全文 | 329621篇 |
免费 | 3436篇 |
国内免费 | 931篇 |
专业分类
化学 | 164797篇 |
晶体学 | 5374篇 |
力学 | 15534篇 |
综合类 | 7篇 |
数学 | 38485篇 |
物理学 | 109791篇 |
出版年
2021年 | 3131篇 |
2020年 | 3338篇 |
2019年 | 3760篇 |
2018年 | 5201篇 |
2017年 | 5439篇 |
2016年 | 7374篇 |
2015年 | 4140篇 |
2014年 | 7030篇 |
2013年 | 15906篇 |
2012年 | 12377篇 |
2011年 | 14827篇 |
2010年 | 11016篇 |
2009年 | 10916篇 |
2008年 | 13235篇 |
2007年 | 13192篇 |
2006年 | 12137篇 |
2005年 | 10521篇 |
2004年 | 9833篇 |
2003年 | 8685篇 |
2002年 | 8673篇 |
2001年 | 10394篇 |
2000年 | 7657篇 |
1999年 | 5967篇 |
1998年 | 4976篇 |
1997年 | 4813篇 |
1996年 | 4480篇 |
1995年 | 3866篇 |
1994年 | 3822篇 |
1993年 | 3703篇 |
1992年 | 4096篇 |
1991年 | 4307篇 |
1990年 | 4102篇 |
1989年 | 4008篇 |
1988年 | 3780篇 |
1987年 | 3917篇 |
1986年 | 3683篇 |
1985年 | 4633篇 |
1984年 | 4683篇 |
1983年 | 3885篇 |
1982年 | 3979篇 |
1981年 | 3701篇 |
1980年 | 3648篇 |
1979年 | 3914篇 |
1978年 | 3902篇 |
1977年 | 3907篇 |
1976年 | 3881篇 |
1975年 | 3677篇 |
1974年 | 3616篇 |
1973年 | 3651篇 |
1972年 | 2604篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
S. Yu. Davydov 《Technical Physics》2002,47(1):92-96
A relationship is analyzed between the ionization energy of atoms I and the work function φ of a metal composed of these atoms. The transition energy ∑=I?φ is assumed to be the sum of kinetic K and coulombic C contributions. Contribution K is calculated in the framework of a model of uniform gas of quasi-free electrons, and C is determined from experimental values of Σ. Calculations performed for a wide range of metals have shown that the dimensionless coefficients determining the Coulombic contribution C differ insignificantly between various groups of metals. The relationships obtained have been used for determining the work function of binary alloys. 相似文献
992.
Raman scattering in glasses is investigated theoretically. The experimental Raman spectra of glasses exhibit a low-frequency peak (at ~10 cm?1) that, as a rule, is attributed to vibrational modes of nanometer-sized structural units (nanocrystallites). It is established that the elastic moduli of nanocrystallites must necessarily be dependent on their sizes due to the Laplace pressure effect. A theory of the low-frequency peak is constructed using a realistic size distribution function of nanocrystallites with allowance made for the Laplace pressure effect and the dissipation of vibrational energy. Within this theory, the shape of the low-frequency peak and its evolution with temperature can be analyzed quantitatively. The proposed approach offers a physical interpretation of the experimental data and provides insight into the relation of the characteristic nanocrystallite sizes to the elastic moduli and surface tension coefficients of materials. 相似文献
993.
A. V. Savin E. I. Sokolov V. S. Favorskii I. V. Shatalov 《Journal of Applied Mechanics and Technical Physics》1991,32(6):893-897
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 6, pp. 78–83, November–December, 1991. 相似文献
994.
Explosion-produced plasma jets formed in free spece are experimentally investigated. The feasibility of emitting pulsed electromagnetic signals by plasma jets is shown, and the emitting conditions are studied. Comparison is made between the results of experiments with short and long plasma jets. When the jet passes through the field of a helix, a short-term increase in the emitted signal is detected. A linear parametric model of interaction between the plasma jet and an exciting electromagnetic signal is proposed. The operating performance of instrumentation developed for the investigation is presented. 相似文献
995.
We considered the kaon absorption from atomic states into the nucleus. We found that the nuclear density probed by the atomic
kaon significantly depends on the kaon orbit. Then, we re-examined the meanings of the observed strengths of one-body and
two-body kaon absorption, and investigated the effects to the formation spectra of kaon bound states by in-flight (K
-, p) reactions. As a natural consequence, if the atomic kaon probes a smaller nuclear density, the ratio of the two-body absorption
at nuclear center is larger than the observed value in kaonic atoms, and the depth of the imaginary potential is deeper even
at smaller kaon energies as in kaonic nuclear states because of the large phase space for the two-body processes. This deeper
imaginary potential makes the signals of kaonic nucleus formation more unclear in the (K
-, p) spectra. 相似文献
996.
Numerical studies were conducted to investigate the natural convection heat transfer around a uniformly heated thin plate
with arbitrary inclination in an infinite space. The numerical approach was based on the finite volume technique with a nonstaggered
grid arrangement. For handling the pressure–velocity coupling the SIMPLE-algorithm was used. QUICK scheme and first order
upwind scheme were employed for discretization of the momentum and energy convective terms respectively. Plate width and heating
rate were used to vary the modified Rayleigh number over the range of 4.8×106 to 1.87×108. Local and average heat transfer characteristics were compared with regarding to the inclination angle. The empirical expressions
for local and average Nusselt number were correlated. It has been found that for inclination angle less than 10∘, the flow and heat transfer characteristics are complicated and the average Nusselt number can not be correlated by one equation
while for inclination angle larger than 10∘, the average Nusselt number can be correlated into an elegant correlation.
Received on 18 April 2001 / Published online: 29 November 2001 相似文献
997.
Barannikov V. P. Guseinov S. S. V'ugin A. I. 《Russian Journal of Coordination Chemistry》2002,28(3):153-162
A review of the experimental and theoretical studies of the crown ether complexes with polar molecules in their crystals, solutions, and in a gas phase is given. The type of the molecular bonds in the complexes, their stoichiometry, and the change in the macrocycle conformation during complex formation are considered, as well as the effect of the macrocycle structure and the nature of the medium on the efficiency of the molecular bonding. New data are given on the enthalpies of transfer of the crown ethers from tetrachloromethane into solvents capable of forming hydrogen bonds. The enthalpies of specific interactions of macrocycles with the molecules of the solvents in the medium of the same solvents are characterized. The conformations of the crown ethers in the media under study are discussed. 相似文献
998.
999.
1000.
Thomas M. F. Case G. S. Bland J. Herring A. D. F. Stirling W. G. Tixier S. Boni P. Ward R. C. C. Wells M. R. Langridge S. 《Hyperfine Interactions》2002,141(1-4):471-476
Hyperfine Interactions - Multilayers of Ce/Fe and U/Fe were fabricated by sputtering and studied by X-ray diffraction and reflectivity, Mössbauer spectroscopy and polarised neutron... 相似文献