全文获取类型
收费全文 | 502462篇 |
免费 | 3872篇 |
国内免费 | 1490篇 |
专业分类
化学 | 245968篇 |
晶体学 | 7403篇 |
力学 | 26229篇 |
综合类 | 13篇 |
数学 | 80054篇 |
物理学 | 148157篇 |
出版年
2020年 | 3513篇 |
2019年 | 3889篇 |
2018年 | 15150篇 |
2017年 | 14861篇 |
2016年 | 13247篇 |
2015年 | 5331篇 |
2014年 | 7495篇 |
2013年 | 18331篇 |
2012年 | 17411篇 |
2011年 | 26551篇 |
2010年 | 17185篇 |
2009年 | 17294篇 |
2008年 | 21717篇 |
2007年 | 23938篇 |
2006年 | 15162篇 |
2005年 | 14652篇 |
2004年 | 13877篇 |
2003年 | 13041篇 |
2002年 | 11906篇 |
2001年 | 12454篇 |
2000年 | 9730篇 |
1999年 | 7448篇 |
1998年 | 6429篇 |
1997年 | 6333篇 |
1996年 | 5988篇 |
1995年 | 5527篇 |
1994年 | 5508篇 |
1993年 | 5172篇 |
1992年 | 5803篇 |
1991年 | 5886篇 |
1990年 | 5688篇 |
1989年 | 5380篇 |
1988年 | 5514篇 |
1987年 | 5453篇 |
1986年 | 5140篇 |
1985年 | 6806篇 |
1984年 | 7193篇 |
1983年 | 5981篇 |
1982年 | 6287篇 |
1981年 | 6177篇 |
1980年 | 6046篇 |
1979年 | 6101篇 |
1978年 | 6437篇 |
1977年 | 6366篇 |
1976年 | 6449篇 |
1975年 | 5954篇 |
1974年 | 6017篇 |
1973年 | 6277篇 |
1972年 | 4297篇 |
1971年 | 3509篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Zarubitskii O. G. Budnik V. G. Omel'chuk A. A. Melekhin V. T. Opanasyuk V. P. Zakharchenko N. F. 《Russian Journal of Applied Chemistry》2002,75(4):558-561
Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry. 相似文献
62.
G. Dattoli 《Journal of Mathematical Analysis and Applications》2002,269(2):716-725
Bilateral generating functions are those involving products of different types of polynomials. We show that operational methods offer a powerful tool to derive these families of generating functions. We study cases relevant to products of Hermite polynomials with Laguerre, Legendre and other polynomials. We also propose further extensions of the method which we develop here. 相似文献
63.
Data Envelopment Analysis (DEA) offers a piece-wise linear approximation of the production frontier. The approximation tends to be poor if the true frontier is not concave, eg in case of economies of scale or of specialisation. To improve the flexibility of the DEA frontier and to gain in empirical fit, we propose to extend DEA towards a more general piece-wise quadratic approximation, called Quadratic Data Envelopment Analysis (QDEA). We show that QDEA gives statistically consistent estimates for all production frontiers with bounded Hessian eigenvalues. Our Monte-Carlo simulations suggest that QDEA can substantially improve efficiency estimation in finite samples relative to standard DEA models. 相似文献
64.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 5, pp. 815–819, May, 1991. 相似文献
65.
66.
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
67.
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
68.
Aidan Mooney John G. Keating Daniel M. Heffernan 《Chaos, solitons, and fractals》2006,30(5):1088-1097
A digital watermark is a visible, or preferably invisible, identification code that is permanently embedded in digital media, to prove owner authentication and provide protection for documents. Given the interest in watermark generation using chaotic functions a detailed study of one chaotic function for this purpose is performed. In this paper, we present an approach for the generation of watermarks using the logistic map. Using this function, in conjunction with seed management, it is possible to generate chaotic sequences that may be used to create highpass or lowpass digital watermarks. In this paper we provide a detailed study on the generation of optically detectable watermarks and we provide some guidelines on successful chaotic watermark generation using the logistic map, and show using a recently published scheme, how care must be taken in the selection of the function seed. 相似文献
69.
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
70.
M. Brokate D. Rachinskii 《NoDEA : Nonlinear Differential Equations and Applications》2006,13(4):385-411
The paper is concerned with the study of plasticity models described by differential equations with stop and play operators.
We suggest sufficient conditions for the global stability of a unique periodic solution for the scalar models and for the
vector models with biaxial inputs of a particular form, namely the sum of a uniaxial function and a constant term. For another
class of simple biaxial inputs, we present an example of the existence of unstable periodic solutions.
The paper was written during the research stay of D. Rachinskii at the Technical University Munich supported by the research
fellowship from the Alexander von Humboldt Foundation. His work was partially supported by the Russian Science Support Foundation, Russian Foundation for Basic Research (Grant No. 01-01-00146, 03-01-00258), and the Grants of the President of Russia (Grant No. MD-87.2003.01, NS-1532.2003.1). The support is gratefully acknowledged. 相似文献