全文获取类型
收费全文 | 275880篇 |
免费 | 3315篇 |
国内免费 | 633篇 |
专业分类
化学 | 146301篇 |
晶体学 | 3963篇 |
力学 | 11925篇 |
综合类 | 26篇 |
数学 | 35695篇 |
物理学 | 81918篇 |
出版年
2021年 | 2986篇 |
2020年 | 3106篇 |
2019年 | 3774篇 |
2018年 | 5344篇 |
2017年 | 5364篇 |
2016年 | 7596篇 |
2015年 | 4362篇 |
2014年 | 6661篇 |
2013年 | 13239篇 |
2012年 | 11237篇 |
2011年 | 12466篇 |
2010年 | 9830篇 |
2009年 | 9768篇 |
2008年 | 11692篇 |
2007年 | 11428篇 |
2006年 | 10112篇 |
2005年 | 8992篇 |
2004年 | 8167篇 |
2003年 | 7202篇 |
2002年 | 6941篇 |
2001年 | 6999篇 |
2000年 | 5676篇 |
1999年 | 4196篇 |
1998年 | 3637篇 |
1997年 | 3654篇 |
1996年 | 3375篇 |
1995年 | 2792篇 |
1994年 | 2976篇 |
1993年 | 2817篇 |
1992年 | 3133篇 |
1991年 | 3157篇 |
1990年 | 3106篇 |
1989年 | 3072篇 |
1988年 | 2977篇 |
1987年 | 2977篇 |
1986年 | 2810篇 |
1985年 | 3561篇 |
1984年 | 3607篇 |
1983年 | 2988篇 |
1982年 | 2959篇 |
1981年 | 2925篇 |
1980年 | 2689篇 |
1979年 | 3037篇 |
1978年 | 2980篇 |
1977年 | 3178篇 |
1976年 | 3187篇 |
1975年 | 2927篇 |
1974年 | 2883篇 |
1973年 | 3011篇 |
1972年 | 2253篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
Using the simplest (sinusoidal) corrugation profile in the approximation of absence of losses in the material as an example, we study the regimes of complete transformation of an incident wave to the diffraction lobe by a corrugated metal surface or a corrugated interface of two dielectric media. A numerical-intuitive pattern of appearance and evolution of such regimes with increasing corrugation amplitude is revealed. It is shown that the regimes of complete transformation of an incident wave to the diffraction lobe are possible in both the case of autocollimation and the case of a considerable deviation from it. The examination is based on a numerical method of solving the integral equation by means of a specially created interactive processing system in Visual Fortran. 相似文献
182.
183.
184.
W. L. Liang B. K. A. Ngoi L. E. N. Lim K. Venkatakrishnan C. W. Hee 《Optics & Laser Technology》2003,35(4):285-290
In this paper, integration of interference phenomenon into femtosecond laser micromachining was reported as the femtosecond laser pulses were reshaped spatially to perform ablation. The generation of circular interference pattern was demonstrated by overlapping infrared femtosecond laser pulses. The interference pattern was subsequently focused on a copper substrate to ablate microstructures of concentric circular rings. The present technique is expected to open up new applications in the areas of rapid fabrication of micro-Fresnel lenses, hybrid microlenses and lens arrays. 相似文献
185.
186.
The paper discusses the applicability of quasi-crystalline approximation to describing the thermal motion of water molecules in their normal and supercooled states. The problem is subjected to the critical analysis of experimental data on incoherent scattering of slow neutrons based on theories developed by Singwi-Sjolander [1] and Oskotsky [2] modified to duly take into account the limited applicability range of diffusion approximation. The applicability conditions of quasi-crystalline approximation are shown to be consistently satisfied only when water is in supercooled state and within a narrow temperature range above the melting temperature. 相似文献
187.
Planar laser-induced fluorescence visualisation is used to investigate nonuniformities in the flow of a hypersonic conical nozzle. Possible causes for the nonuniformity are outlined and investigated, and the problem is shown to be due to a small step at the nozzle throat. Entrainment of cold boundary layer gas is postulated as the cause of the signal nonuniformity.
PACS 47.80.Jk, 47.40.Ki, 47.60.+i 相似文献
188.
The semiclassical theory of proximity effects predicts a gap E g~?D/L 2 in the excitation spectrum of a long diffusive superconductor/normal-metal/superconductor (SNS) junction. Mesoscopic fluctuations lead to anomalously localized states in the normal part of the junction.As a result, a nonzero, yet exponentially small, density of states (DOS) appears at energies below E g. In the framework of the supermatrix nonlinear σ model, these prelocalized states are due to the instanton configurations with broken supersymmetry. The exact result for the DOS near the semiclassical threshold is found, provided the dimensionless conductance of the normal part G N is large. The case of poorly transparent interfaces between the normal and superconductive regions is also considered. In this limit, the total number of subgap states may be large. 相似文献
189.
190.
A. N. Grishkov 《Algebra and Logic》1998,37(5):294-306
Ordinary cohomologies in an algebra most often exhibit themselves either as objects that describe extensions (of algebras,
groups, or modules) or as subjects hindering the existence of algebraic constructions. We introduce the notion of nonlinear
cohomologies at a level of cochain complexes, furnish particular examples for Lie algebras, and give an interpretation of
first nonlinear cohomologies in terms of “quasiextensions” of orthogonal modules.
Translated fromAlgebra i Logika, Vol. 37, No. 5, pp. 522–541, September–October, 1998. 相似文献