全文获取类型
收费全文 | 512044篇 |
免费 | 2797篇 |
国内免费 | 939篇 |
专业分类
化学 | 240807篇 |
晶体学 | 7295篇 |
力学 | 28417篇 |
综合类 | 9篇 |
数学 | 79272篇 |
物理学 | 159980篇 |
出版年
2020年 | 4531篇 |
2019年 | 5397篇 |
2018年 | 12527篇 |
2017年 | 12919篇 |
2016年 | 12653篇 |
2015年 | 5508篇 |
2014年 | 9201篇 |
2013年 | 18909篇 |
2012年 | 17520篇 |
2011年 | 25113篇 |
2010年 | 17828篇 |
2009年 | 18094篇 |
2008年 | 23371篇 |
2007年 | 25515篇 |
2006年 | 15564篇 |
2005年 | 16859篇 |
2004年 | 14383篇 |
2003年 | 13842篇 |
2002年 | 12870篇 |
2001年 | 12066篇 |
2000年 | 9836篇 |
1999年 | 7174篇 |
1998年 | 6505篇 |
1997年 | 6413篇 |
1996年 | 6068篇 |
1995年 | 5211篇 |
1994年 | 5323篇 |
1993年 | 5312篇 |
1992年 | 5493篇 |
1991年 | 5883篇 |
1990年 | 5755篇 |
1989年 | 5788篇 |
1988年 | 5500篇 |
1987年 | 5517篇 |
1986年 | 5224篇 |
1985年 | 6372篇 |
1984年 | 6739篇 |
1983年 | 5621篇 |
1982年 | 6017篇 |
1981年 | 5602篇 |
1980年 | 5243篇 |
1979年 | 5867篇 |
1978年 | 6122篇 |
1977年 | 6171篇 |
1976年 | 6250篇 |
1975年 | 5861篇 |
1974年 | 5726篇 |
1973年 | 6046篇 |
1972年 | 4655篇 |
1971年 | 4175篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
J. C. Fabris S. V. B. Gonçalves P. E. de Souza 《General Relativity and Gravitation》2002,34(12):2111-2126
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate. 相似文献
52.
In this paper, a two-dimensional finite volume unstructured mesh method (FVUM) based on a triangular background interpolation mesh is developed for analysing the evolution of the saltwater intrusion into single and multiple coastal aquifer systems. The model formulation consists of a ground-water flow equation and a salt transport equation. These coupled and non-linear partial differential equations are transformed by FVUM into a system of differential/algebraic equations, which is solved using backward differentiation formulas of order one through five. Simulation results are compared with previously published solutions where good agreement is observed. 相似文献
53.
Optics and Spectroscopy - The relationship between the parameters of quadripoles (mirrors, for example) ensuring the fulfillment of the energy conservation law are considered. Apart from the... 相似文献
54.
The thermal decomposition of piperidine hydrothiocyanate, piperazine hydrothiocyanate, and the dihydrothiocyanates of ethylenediamine and 1,3-diaminopropane has been studied using TG. Piperidine hydrothiocyanate decomposes in a single step while the dihydrothiocyanates follow more complicated decomposition patterns yielding H2S and half of the organic moiety first. The second step involves the loss of H2S and the remainder of the organic moiety. In each case, complex polymeric materials result. Piperazine hydrothiocyanate also decomposes in two steps, the first involving the loss of half of the piperazine and the second involving the loss of piperazine and H2S. Kinetic parameters have been determined for all these reactions. 相似文献
55.
56.
A. L. Apanasenko A. V. Kuznichenko Yu. B. Govyadovskii V. G. Yakunin 《Journal of Applied Spectroscopy》1991,54(3):271-276
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 1991. 相似文献
57.
Yu. K. Voron'ko A. B. Kudryavtsev V. V. Osiko E. V. Sorokin 《Journal of Applied Spectroscopy》1991,55(4):953-957
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 535–540, October, 1991. 相似文献
58.
59.
A new geometrical method to determine the surface damage threshold for ultrashort pulses is presented. It consists in the formation of a surface damage profile by a movement of the sample across the laser beam focus. A single measurement of the maximum transversal dimension of this damage profile, which depends solely on the laser beam power, is used to calculate the local damage threshold intensity. It is also theoretically shown that the damage in the transverse dimension can be controlled under the diffraction-limited spot. 相似文献
60.
V. G. Osmolovski 《Journal of Mathematical Sciences》2006,132(3):304-312
Dependence of the phase transition temperature on the domain size is investigated for a double-well quadratic potential. It
is shown that for a domain whose boundary is subjected to a hydrostatical pressure, the temperature of phase transitions is
independent of the domain and the surface tension coefficient and depends exclusively on the properties of the elastic media.
If the displacement field vanishes on the boundary, then for sufficiently small domains, the temperature also does not depend
on the surface tension and domain size and is determined by properties of the elastic media only. Bibliography: 8 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 310, 2004, pp. 98–113. 相似文献