全文获取类型
收费全文 | 36871篇 |
免费 | 424篇 |
国内免费 | 149篇 |
专业分类
化学 | 18306篇 |
晶体学 | 684篇 |
力学 | 1620篇 |
综合类 | 2篇 |
数学 | 3587篇 |
物理学 | 13245篇 |
出版年
2022年 | 361篇 |
2021年 | 399篇 |
2020年 | 341篇 |
2019年 | 342篇 |
2018年 | 537篇 |
2017年 | 461篇 |
2016年 | 728篇 |
2015年 | 415篇 |
2014年 | 731篇 |
2013年 | 1596篇 |
2012年 | 1498篇 |
2011年 | 1853篇 |
2010年 | 1347篇 |
2009年 | 1339篇 |
2008年 | 1527篇 |
2007年 | 1512篇 |
2006年 | 1389篇 |
2005年 | 1198篇 |
2004年 | 1137篇 |
2003年 | 986篇 |
2002年 | 939篇 |
2001年 | 1349篇 |
2000年 | 970篇 |
1999年 | 803篇 |
1998年 | 607篇 |
1997年 | 581篇 |
1996年 | 508篇 |
1995年 | 470篇 |
1994年 | 446篇 |
1993年 | 392篇 |
1992年 | 464篇 |
1991年 | 471篇 |
1990年 | 461篇 |
1989年 | 424篇 |
1988年 | 446篇 |
1987年 | 430篇 |
1986年 | 376篇 |
1985年 | 441篇 |
1984年 | 470篇 |
1983年 | 345篇 |
1982年 | 387篇 |
1981年 | 376篇 |
1980年 | 320篇 |
1979年 | 400篇 |
1978年 | 378篇 |
1977年 | 394篇 |
1976年 | 392篇 |
1975年 | 342篇 |
1974年 | 323篇 |
1973年 | 340篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
51.
We present some algorithms related to rings of Ore polynomials (or, briefly, Ore rings) and describe a computer algebra library
for basic operations in an arbitrary Ore ring. The library can be used as a basis for various algorithms in Ore rings, in
particular, in differential, shift, and q-shift rings.
__________
Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 13, Algebra,
2004. 相似文献
52.
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
53.
Thermodynamic fluctuations in systems that are in nonequilibrium steady states are always spatially long ranged, in contrast to fluctuations in thermodynamic equilibrium. In the present paper we consider a fluid subjected to a stationary temperature gradient. Two different physical mechanisms have been identified by which the temperature gradient causes long-ranged fluctuations. One cause is the presence of couplings between fluctuating fields. Secondly, spatial variation of the strength of random forces, resulting from the local version of the fluctuation-dissipation theorem, has also been shown to generate long-ranged fluctuations. We evaluate the contributions to the long-ranged temperature fluctuations due to both mechanisms. While the inhomogeneously correlated Langevin noise does lead to long-ranged fluctuations, in practice, they turn out to be negligible as compared to nonequilibrium temperature fluctuations resulting from the coupling between temperature and velocity fluctuations. 相似文献
54.
Field emission study of thin water layers was performed to examine their properties and their changes after application of a high electric field. Comparison of field emission characteristics of water layers adsorbed on clean tungsten and gold-covered tungsten suggested that, whereas water molecules adsorbed on tungsten are oriented by oxygen atoms towards the metal surface, water layer on gold-covered tungsten has amorphous character with no preferential orientation. Both heated and non-heated layers are heavily influenced by applied high electric field strengths (F ≈30 MV/cm). Decrease of the work function and of the voltage needed for a constant emission current during successive increase of the electric field was tentatively interpreted in terms of chemical and morfological changes of the water layer due to the field dissociation and solvation. 相似文献
55.
V. Z. Kasimov O. V. Ushakova Yu. P. Khomenko 《Journal of Applied Mechanics and Technical Physics》2003,44(5):612-619
An improved procedure for modeling the operation of a light-gas gun is proposed. The motion of working bodies in both the firing chamber and the light-gas chamber is studied within the framework of the mechanics of heterogeneous media. The problem of barrel heating taking into account its melting and removal of thermal ablation products into the medium inside the bore is solved in a coupled formulation. Heat and mass transfer and friction on the barrel surface are calculated using empirical dependences. The deformable piston is considered compressible and elastoviscoplastic. Allowance is made for the presence of a clearance between the lateral surface of the piston and the barrel bore walls and the associated gas flow between the firing and the light-gas chamber. Calculation results are given. 相似文献
56.
An experimental method is developed to examine the near tip deformation at the mesoscopic scale level. The differential interference contrast (DIC) method is used by application of the Nomarski prism in polarized microscope for measuring the out of surface deformation. The method is very sensitive to small height changes detected by different interference color. Discussed are results for the crack tip deformation field. 相似文献
57.
Teys S. A. Talochkin A. B. Romanyuk K. N. Olshanetsky B. Z. 《Physics of the Solid State》2004,46(1):80-84
Physics of the Solid State - The growth of germanium nanoislands and nanowires on singular and vicinal Si(111) surfaces is investigated by scanning tunneling microscopy (STM). It is shown that the... 相似文献
58.
59.
Yu. B. Bolkhovityanov S. Ts. Krivoshchapov A. I. Nikiforov B. Z. Ol’shanetskii O. P. Pchelyakov L. V. Sokolov S. A. Teys 《Physics of the Solid State》2004,46(1):64-66
Different techniques for the fabrication of structures containing ensembles of ultrasmall germanium nanoclusters distributed with a high density over the substrate surface are discussed. How to control the morphology and ordering of these ensembles is also discussed. 相似文献
60.
X. H. Li Y. Z. Meng S. J. Wang A. Varada Rajulu S. C. Tjong 《Journal of Polymer Science.Polymer Physics》2004,42(4):666-675
The composites of biodegradable poly(propylene carbonate) (PPC) reinforced with short Hildegardia populifolia natural fiber were prepared by melt mixing followed by compression molding. The mechanical properties, thermal properties, and morphologies of the composites were studied via static and dynamic mechanical measurements, thermogravimetric analysis, and scanning electron microscopy (SEM) techniques, respectively. Static tensile tests showed that the stiffness and tensile strength of the composites increased with an increasing fiber content. However, the elongation at break and the energy to break decreased dramatically with the addition of short fiber. The relationship between the experimental results and the compatibility or interaction between the PPC matrix and fiber was correlated. SEM observations indicated good interfacial contact between the short fiber and PPC matrix. Thermogravimetric analysis revealed that the introduction of short Hildegardia populifolia fiber led to a slightly improved thermooxidative stability of PPC. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 666–675, 2004 相似文献