全文获取类型
收费全文 | 62612篇 |
免费 | 4713篇 |
国内免费 | 3821篇 |
专业分类
化学 | 20376篇 |
晶体学 | 394篇 |
力学 | 3869篇 |
综合类 | 506篇 |
数学 | 10697篇 |
物理学 | 19864篇 |
无线电 | 15440篇 |
出版年
2024年 | 191篇 |
2023年 | 803篇 |
2022年 | 1370篇 |
2021年 | 1581篇 |
2020年 | 1632篇 |
2019年 | 1418篇 |
2018年 | 1248篇 |
2017年 | 1571篇 |
2016年 | 1937篇 |
2015年 | 1604篇 |
2014年 | 2657篇 |
2013年 | 3894篇 |
2012年 | 2942篇 |
2011年 | 3090篇 |
2010年 | 2394篇 |
2009年 | 3468篇 |
2008年 | 3767篇 |
2007年 | 4190篇 |
2006年 | 3591篇 |
2005年 | 2868篇 |
2004年 | 2447篇 |
2003年 | 2701篇 |
2002年 | 2958篇 |
2001年 | 2247篇 |
2000年 | 2099篇 |
1999年 | 1746篇 |
1998年 | 1675篇 |
1997年 | 1012篇 |
1996年 | 966篇 |
1995年 | 844篇 |
1994年 | 882篇 |
1993年 | 658篇 |
1992年 | 739篇 |
1991年 | 503篇 |
1990年 | 479篇 |
1989年 | 354篇 |
1988年 | 298篇 |
1987年 | 285篇 |
1986年 | 250篇 |
1985年 | 234篇 |
1984年 | 234篇 |
1983年 | 150篇 |
1982年 | 194篇 |
1981年 | 186篇 |
1980年 | 123篇 |
1979年 | 154篇 |
1978年 | 129篇 |
1977年 | 118篇 |
1976年 | 75篇 |
1973年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
E. Hatta H. Hosoi H. Akiyama T. Ishii K. Mukasa 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):347-349
We have observed a remarkable two-armed spiral in the collapse process of a floating monolayer at the air-water interface
by phase contrast microscopy. This demonstrates that the floating monolayer as a form of soft condensed matter reorganizes
itself due to a certain kind of macroscopic or collective behavior of molecules as it collapses. This pattern formation is
caused by the breakdown of a critical dynamical balance between the deformation of solid domain and the applied surface pressure.
The fragility as well as the flexibility of the floating monolayer can be associated with the observed pattern growth. There
are also observed interesting, periodically arranged collections of molecules in numerous collapsed regions.
Received: 8 July 1997 / Accepted: 4 November 1997 相似文献
52.
R. Gerbaldo G. Ghigo G. Giunchi L. Gozzelino F. Laviano E. Mezzetti 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):297-300
We present results from an extended magneto-optical (MO) analysis of two samples cut from high-density pellets of MgB2. The first sample was studied in order to show that no matter how large the sample is and despite the bulk granularity, the
material enters into a critical state in a crystal-like fashion. The second sample was chosen for the quantitative analysis.
A numerical approach based on an inverted 2D Biot-Savart model was used to calculate the current paths across the homogeneous
polycrystalline bulk, as well as in the vicinity and across some morphological defects. Local current densities in the homogeneous
part were estimated as a function of the applied magnetic field at different temperatures, in three regimes: below full penetration,
at full penetration and above full penetration, respectively. A hypothesis of interpretation of the apparent absence of magnetic
granularity inside the polycrystalline microstructure is presented. It is related to a critical state likely reached by a
network of strongly coupled Josephson junctions.
Received 31 May 2001 and Received in final form 5 December 2001 相似文献
53.
An effective residual interaction between particles and holes for shell model calculations around 208Pb, derived from the interaction between free nucleons, is compared with the measured properties of proton-hole neutron states
in 208Tl and the interaction between proton holes is adjusted to newly measured level energies in 206Hg. These interaction elements are particularly relevant for neutron-rich nuclei. The adjustment of two mixing elements reproduces
the known γ-decay data in 208Tl.
Received: 2 April 2002 / Accepted: 2 May 2002 相似文献
54.
K. Weibert J. Main G. Wunner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):379-388
In the periodic orbit quantization of physical systems, usually only the leading-order ? contribution to the density of states is considered. Therefore, by construction, the eigenvalues following from semiclassical
trace formulae generally agree with the exact quantum ones only to lowest order of ?. In different theoretical work the trace formulae have been extended to higher orders of ?. The problem remains, however, how to actually calculate eigenvalues from the extended trace formulae since, even with ? corrections included, the periodic orbit sums still do not converge in the physical domain. For lowest-order semiclassical trace formulae the convergence problem can be elegantly, and universally, circumvented by application of the
technique of harmonic inversion. In this paper we show how, for general scaling chaotic systems, also higher-order
? corrections to the Gutzwiller formula can be included in the harmonic inversion scheme, and demonstrate that corrected semiclassical
eigenvalues can be calculated despite the convergence problem. The method is applied to the open three-disk scattering system,
as a prototype of a chaotic system.
Received 10 September 2001 and Received in final form 3 January 2002 相似文献
55.
Dimitrios Tzovaras Nikos Grammalidis Michael G. Strintzis 《Signal Processing: Image Communication》1998,11(3):205-230
In the present paper techniques are examined for the coding of the depth map and disparity fields for stereo or multiview image communication applications. It is assumed that both the left and right channels of the multiview image sequence are coded using block- or object-based methods. A dynamic programming algorithm is used to estimate a disparity field between each stereo image pair. Depth is then estimated and occlusions are optionally detected, based on the estimated disparity fields. Spatial interpolation techniques are examined based on the disparity/depth information and the detection of occluded regions using either stereoscopic or trinocular camera configurations. It is seen that the presence of a third camera at the transmitter site improves the estimation of disparities, the detection of occlusions and the accuracy of the resulting spatial interpolation at the receiver. Various disparity field and depth map coding techniques are then proposed and evaluated, with emphasis given to the quality of the resulting intermediate images at the receiver site. Block-based and wireframe modeling techniques are examined for the coding of isolated depth or disparity map information. Further, 2D and 3D motion compensation techniques are evaluated for the coding of sequences of depth or disparity maps. The motion fields needed may be available as a byproduct of block-based or object-based coding of the intensity images. Experimental results are given for the evaluation of the performance of the proposed coding and spatial interpolation methods. 相似文献
56.
57.
58.
纳米科学技术将成为21世纪最重要的高技术之一。纳米技术的最终目标是直接操纵单个原子和分子,制造量子功能器件,从而开拓人类崭新的生产生活模式。文章评述利用电子束、离子束的精细技术和STM原子操纵技术的研究现状,介绍原子层蚀刻,单层抗蚀剂自形成蚀刻,纳米自然蚀刻和电子束全息纳米蚀刻等高技术前沿动态,展望纳米技术的发展前景。 相似文献
59.
The phase behavior of binary blends of poly(ether ether ketone) (PEEK), sulfonated PEEK, and sulfamidated PEEK with aromatic polyimides is reported. PEEK was determined to be immiscible with a poly(amide imide) (TORLON 4000T). Blends of sulfonated and sulfamidated PEEK with this poly(amide imide), however, are reported here to be miscible in all proportions. Blends of sulfonated PEEK and a poly(ether imide) (ULTEM 1000) are also reported to be miscible. Spectroscopic investigations of the intermolecular interactions suggest that formation of electron donoracceptor complexes between the sulfonated/sulfamidated phenylene rings of the PEEKs and the n-phenylene units of the polyimides are responsible for this miscibility. © 1993 John Wiley & Sons, Inc. 相似文献
60.