全文获取类型
收费全文 | 1366904篇 |
免费 | 25902篇 |
国内免费 | 7846篇 |
专业分类
化学 | 681301篇 |
晶体学 | 20707篇 |
力学 | 75450篇 |
综合类 | 113篇 |
数学 | 244390篇 |
物理学 | 378691篇 |
出版年
2021年 | 13554篇 |
2020年 | 15987篇 |
2019年 | 16089篇 |
2018年 | 14347篇 |
2017年 | 12760篇 |
2016年 | 28633篇 |
2015年 | 21079篇 |
2014年 | 30569篇 |
2013年 | 74685篇 |
2012年 | 39112篇 |
2011年 | 37468篇 |
2010年 | 38574篇 |
2009年 | 40748篇 |
2008年 | 36412篇 |
2007年 | 32689篇 |
2006年 | 36494篇 |
2005年 | 30567篇 |
2004年 | 30919篇 |
2003年 | 28882篇 |
2002年 | 29612篇 |
2001年 | 28679篇 |
2000年 | 24952篇 |
1999年 | 22560篇 |
1998年 | 21071篇 |
1997年 | 21108篇 |
1996年 | 21165篇 |
1995年 | 19238篇 |
1994年 | 18704篇 |
1993年 | 18250篇 |
1992年 | 18241篇 |
1991年 | 18524篇 |
1990年 | 17682篇 |
1989年 | 17745篇 |
1988年 | 17317篇 |
1987年 | 17327篇 |
1986年 | 16220篇 |
1985年 | 22665篇 |
1984年 | 23903篇 |
1983年 | 20031篇 |
1982年 | 21725篇 |
1981年 | 20952篇 |
1980年 | 20327篇 |
1979年 | 20507篇 |
1978年 | 21798篇 |
1977年 | 21390篇 |
1976年 | 21115篇 |
1975年 | 19781篇 |
1974年 | 19464篇 |
1973年 | 19906篇 |
1972年 | 14385篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
M. P. Nosov V. A. Smirnova Yu. F. Zabashta A. Ya. Fridman M. P. Mokhnach 《Mechanics of Composite Materials》1989,25(1):8-12
Conclusion A method was proposed which makes it possible to study the low-frequency internal friction of complex fibers. This method was used to study the internal friction of complex composite fibers based on PCA and PE. We observed a relaxation process which is typical of the composite and is absent in the pure materials.Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 11–15, January–February, 1989. 相似文献
992.
P. P. Kirpichok N. B. Voronina A. F. Sitnikov V. Ya. Garmash 《Russian Physics Journal》1989,32(1):26-30
The effect of rare-earth oxides on the properties of anisotropic barium ferrites has been studied by x-ray structural and Mössbauer methods. Additions of SrCO3, as well as SrCO3 and La2O3, SrCO3 and Pr6O11, SrCO3 and Nd2O3, SrCO3 and Sm2O3 in amounts of 7.5 mole % Sr and 10 mole % rare-earth element to grade-A barium powder results in the substitution of barium ions by Sr and rare-earth ions; consequently, the energy of magnetic anisotropy changes and the technically important parameters Br and (BH)max increase.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 34–39, January, 1989. 相似文献
993.
Dynamic stage repair policies where the stage repair probabilities are determined by the number of items in the buffer are examined through a model of a manufacturing system with two unreliable workstages connected by a minimal intermediate storage buffer. Definitions for workstage availability and line balance are extended for sequential manufacturing systems with dynamic repair policies. A measure for stage repair inputs and a general form of dynamic stage repair policies are presented. The steady-state probabilities of the resultant state-inhomogeneous Markov chain are computed by an efficient solution procedure. Insights obtained from extensive numerical studies are illustrated and discussed. 相似文献
994.
N. Vogel 《等离子体物理论文集》1989,29(1):11-24
The stepwise increase of the burning voltage of short break arcs has been found not only in a gas but also in vacuum. It is suggested that the effect is associated with the occurrence of a positive anode fall which enhances ionisation phenomena near the anode. This view is supported by the simultaneous registration of arc current, burning voltage, light emission from the anode region, of spectral lines of ions, atoms and continuum from the near anode plasma. The phenomena occur beyond a critical gap distance which can be related to the characteristic geometry of the discharge. 相似文献
995.
R. R. Zapatrin 《International Journal of Theoretical Physics》1989,28(11):1323-1332
A refined definition of basic concepts for logic describing physical systems is proposed. Within the suggested formalism of generating semigroups the active logic of questions and passive logic of answers are introduced. The objects for which both logics are isomorphic are called self-adequate. It is shown that the assumption of self-adequacy implies that the object is either quantum or classical. The possibility of application of the theory to non-self-adequate objects is discussed. 相似文献
996.
Z.J. Yang T.H. Johansen H. Bratsberg G. Helgesen A.T. Skjeltorp 《Physica C: Superconductivity and its Applications》1989,160(5-6):461-465
Based on a dipole-dipole interaction model, we discuss the levitation force and related vibration problems to understand the effects of flux pinning in type-II superconductors, and the applications of levitation in superconducting systems. 相似文献
997.
In an effort to clarify the role of controlled oxygen exposure in the synthesis of LaBa2Cu3Oy samples which achieve zero resistivity above 90 K, we have prepared samples of La(1+x)Ba(2–x)Cu3Oy with x approximately equal to 0 and with y varying between 6.22 and 7.00. We find that for large values of y, 6.88相似文献
998.
The influence of an electrical field on the charge transfer in crystals with orbital degeneration is investigated. An expression is obtained for the current density in crystals with narrow d-conduction bands in transition metal compounds. As the electrical field intensity increases, a current density maximum is observed with a subsequent section of negative differential conductivity. The results of the investigation agree qualitatively with experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 14–18, February, 1989. 相似文献
999.
Summary We have estimated and measured the daily thermal expansion of an oceanographic platform. This has been found negligible as
far as the calibration of a satellite altimeter is concerned. 相似文献
1000.
V. A. Popova I. V. Podgornaya V. G. Lundina L. I. Kurnikova A. I. Tarasov 《Russian Chemical Bulletin》1987,36(11):2361-2364
Conclusions Complex compounds of bisacyl derivatives of diaminodibenzo-18-crown-6 ether are active catalysts of the two stages of the synthesis of poly(ethylene terephthalate).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2544–2547, November. 1987. 相似文献