全文获取类型
收费全文 | 14433篇 |
免费 | 2933篇 |
国内免费 | 2142篇 |
专业分类
化学 | 9280篇 |
晶体学 | 255篇 |
力学 | 1799篇 |
综合类 | 144篇 |
数学 | 1422篇 |
物理学 | 6608篇 |
出版年
2024年 | 33篇 |
2023年 | 192篇 |
2022年 | 479篇 |
2021年 | 412篇 |
2020年 | 583篇 |
2019年 | 496篇 |
2018年 | 502篇 |
2017年 | 572篇 |
2016年 | 744篇 |
2015年 | 664篇 |
2014年 | 924篇 |
2013年 | 1471篇 |
2012年 | 1038篇 |
2011年 | 999篇 |
2010年 | 836篇 |
2009年 | 893篇 |
2008年 | 929篇 |
2007年 | 997篇 |
2006年 | 858篇 |
2005年 | 742篇 |
2004年 | 688篇 |
2003年 | 628篇 |
2002年 | 481篇 |
2001年 | 460篇 |
2000年 | 452篇 |
1999年 | 351篇 |
1998年 | 348篇 |
1997年 | 263篇 |
1996年 | 247篇 |
1995年 | 211篇 |
1994年 | 206篇 |
1993年 | 151篇 |
1992年 | 133篇 |
1991年 | 90篇 |
1990年 | 69篇 |
1989年 | 68篇 |
1988年 | 58篇 |
1987年 | 41篇 |
1986年 | 41篇 |
1985年 | 32篇 |
1984年 | 29篇 |
1983年 | 8篇 |
1982年 | 24篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1973年 | 5篇 |
1971年 | 3篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A. Pompei 《Applied Acoustics》2006,67(5):420-431
In the present paper, we simulate focused wave fields generated by a system of plane transducers used in an immersion ultrasonic technique. The ultrasonic beam penetrates into the elastic medium through the fluid-solid boundary. A real-time computer algorithm is proposed to calculate stress components in the solid medium. It is shown that a good focusing wave structure can be provided by a pair of plane rectangular transducers, inclined with respect to each other and to the beam acoustic axis. 相似文献
62.
We have performed total-energy calculations to study theoretical scanning tunneling microscopy (STM) images of the Si(1 1 1)3 × 2 surfaces induced by the adsorption of alkaline-earth metals (AEMs). Previously, in a series of works on Ba/Si(1 1 1) system, we have found that the observed Si(1 1 1)3 × 1-Ba LEED phase indeed has a 3 × 2 periodicity with a Ba coverage of 1/6 ML and the HCC substrate structure. Based on results of the Ba case, we proposed that the HCC structure is also adopted for other AEM atoms, which was confirmed by our recent work. In this paper, we mainly report the STM simulations for different AEM systems to compare with existing experimental data. We discuss the difference in the detailed STM images for different AEM adsorbates. Especially, the difference in filled-state images between Mg and other AEM atoms is attributed to the strong Mg-Si interaction. 相似文献
63.
超声波波型转换与表面波的检测 总被引:1,自引:0,他引:1
分析了超声波纵波、横波、表面波3种波型的产生条件和声速关系,检测了超声波在固体表面的波型转换,并测量了声表面波的速度,讨论了声表面波在超声延迟线方面的应用. 相似文献
64.
Young Wook Kim Seong-Deog Yang 《Proceedings of the American Mathematical Society》2006,134(11):3379-3390
We prove the existence of an infinite family of complete spacelike maximal surfaces with singularities in Lorentz-Minkowski three-space and study their properties. These surfaces are distinguished by their number of handles and have two elliptic catenoidal ends.
65.
We present exact numerical results for a symmetric layered medium (prism/Ag film/nonlinear dielectric/Ag film/prism) where
the middle dielectric slab is assumed to have a saturation-type nonlinearity. We show bistable behaviour in the power dependence
of the reflectivity ofp-polarized light under the condition when coupled surface modes are excited in the structure. Moreover, we study the effect
of saturation on the bistable behaviour to show that multivalued character is inhibited by saturation effects. The field distributions
corresponding to the minimum reflectivity states of the nonlinear structure are also presented. 相似文献
66.
Gu Chaohao 《数学年刊B辑(英文版)》1994,15(4):385-400
COMPLETEEXTREMALSURFACESOFMIXEDTYPEIN3-DIMENSIONALMINKOWSKISPACE¥GUCHAOHAO(InstituteofMathematics,FudanUniversity,Shanghai200... 相似文献
67.
We consider a two-dimensional Coulomb gas of positive and negative pointlike unit charges interacting via a logarithmic potential. The density (rather than the charge) correlation functions are studied. In the bulk, the form-factor theory of an equivalent sine-Gordon model is used to determine the density correlation length. At the surface of a rectilinear plain wall, the universality of the asymptotic behavior of the density correlations is suggested. A scaling analysis implies a local form of the compressibility sum rule near a hard wall. A symmetry of the Coulomb system with respect to the Möbius conformal transformation, which induces a gravitational source acting on the particle density, is established. Among the consequences, a universal term of the finite-size expansion of the grand potential is derived exactly for a disk geometry of the confining domain. 相似文献
68.
V. P. Bubnov I. S. Krainskii E. E. Laukhina E. B. Yagubskii 《Russian Chemical Bulletin》1994,43(5):746-750
The effect of the parameters of the electric arc (helium pressure, current and voltage, clearance between electrodes) and of the peculiarities of the setup design (arrangement of electrodes, distance between the arc and the cooling surface, temperature of the soot condensation surface) on the yield of fullerenes has been studied. Conditions for producing soot with a C60 and C70 content up to 43% (toluene extract) have been found.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 805–809, May, 1994.The authors are grateful to N. G. Spitsyna and A. V. Dubovitskii for the determination of the content of C60 and C70 fullerenes in the extract.The work was financially supported by the Russian Foundation for Basic Research (Project 93-03-18705). 相似文献
69.
YBa2Cu3O7-δ and Tl2Ba2CaCu2O8 thin films for microwave filters were synthesized by pulsed laser deposition and the two-step thalliation process. Substrate
quality requirements and the relation of thin film morphology, microstructure with microwave surface resistance were discussed. 相似文献
70.
It was shown by G. A. Jones and the first author in [8] that underlying any map on a compact orientable surface S there is a natural complex structure making S into a Riemann surface. In this paper we consider regular maps and enquire about the Weierstrass points on the underlying Riemann surface. We are particularly interested to know when these are geometric, i.e. whether they lie at vertices, face-centres or edge-centres of the map. 相似文献