全文获取类型
收费全文 | 5558篇 |
免费 | 891篇 |
国内免费 | 322篇 |
专业分类
化学 | 1359篇 |
晶体学 | 51篇 |
力学 | 157篇 |
综合类 | 20篇 |
数学 | 938篇 |
物理学 | 4246篇 |
出版年
2024年 | 4篇 |
2023年 | 77篇 |
2022年 | 142篇 |
2021年 | 179篇 |
2020年 | 145篇 |
2019年 | 166篇 |
2018年 | 178篇 |
2017年 | 196篇 |
2016年 | 232篇 |
2015年 | 216篇 |
2014年 | 364篇 |
2013年 | 453篇 |
2012年 | 372篇 |
2011年 | 374篇 |
2010年 | 319篇 |
2009年 | 422篇 |
2008年 | 404篇 |
2007年 | 363篇 |
2006年 | 314篇 |
2005年 | 263篇 |
2004年 | 231篇 |
2003年 | 210篇 |
2002年 | 160篇 |
2001年 | 114篇 |
2000年 | 122篇 |
1999年 | 97篇 |
1998年 | 112篇 |
1997年 | 87篇 |
1996年 | 70篇 |
1995年 | 64篇 |
1994年 | 56篇 |
1993年 | 47篇 |
1992年 | 49篇 |
1991年 | 37篇 |
1990年 | 21篇 |
1989年 | 18篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有6771条查询结果,搜索用时 15 毫秒
31.
32.
S. S. Andreev A. D. Akhsakhalyan M. A. Bibishkin N. I. Chkhalo S. V. Gaponov S. A. Gusev E. B. Kluenkov K. A. Prokhorov N. N. Salashchenko F. Schafers S. Yu. Zuev 《Central European Journal of Physics》2003,1(1):191-209
We present research investigations in the field of multilayer optics in X-ray and extreme ultra-violet ranges (XUV), aimed
at the development of optical elements for applications in experiments in physics and in scientific instrumentation. We discuss
normal incidence multilayer optics in the spectral region of “water window”, multilayer optics for collimation and focusing
of hard X-ray, multilayer dispersing elements for X-ray spectroscopy of high-temperature plasma, multilayer dispersing elements
for analysis of low Z-elements. Our research pays special attention to optimization of multilayer optics for projection EUV-lithography
(ψ-13nm) and short period multilayer optics. 相似文献
33.
Using Lagrange's multiplier rule, we find upper and lower bounds of the energy of a bipartite graph G, in terms of the number of vertices, edges and the spectral moment of fourth order. Moreover, the upper bound is attained in a graph G if and only if G is the graph of a symmetric balanced incomplete block design (BIBD). Also, we determine the graphs for which the lower bound is sharp. 相似文献
34.
Sean D. Brooks M. F. Mahmood J. A. Donaldson 《Journal of Mathematical Modelling and Algorithms》2004,3(1):19-29
A numerical investigation, based on the split-step Fourier transform algorithm of all optical switching of solitons in a low
birefringent optical fiber is presented. The numerical algorithm is described in detail.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
35.
Abnormalities in the cochlear function usually cause broadening of the auditory filters which reduces the speech intelligibility. An attempt to apply a spectral enhancement algorithm has been undertaken to improve the identification of Polish vowels by subjects with cochlear-based hearing-impairment. The identification scores of natural (unprocessed) vowels and spectrally enhanced (processed) vowels has been measured for hearing-impaired subjects. It has been found that spectral enhancement improves vowel scores by about 10% for those subjects, however, a wide variation in individual performance among subjects has been observed. The overall vowels identification scores obtained were 85% for natural vowels and 96% for spectrally enhanced vowels. 相似文献
36.
37.
Donald W. Barnes 《Transactions of the American Mathematical Society》2003,355(7):2755-2769
The concept of a spectral sequence constructor is generalised to Hopf Galois extensions. The spectral sequence constructions that are given by Guichardet for crossed product algebras are also generalised and shown to provide examples. It is shown that all spectral sequence constructors for Hopf Galois extensions construct the same spectral sequence. 相似文献
38.
I. El-Kady R. Biswas Y. Ye M. F. Su I. Puscasu Martin Pralle E. A. Johnson J. Daly A. Greenwald 《Photonics and Nanostructures》2003,1(1):69-77
In this work, we present both the theoretical basis as well as supporting experimental measurements for development of a novel mid-infrared thermally stimulated narrow band emitter with a spectral bandwidth of less than 10%. To achieve this, we utilize a metallized-surface 2D photonic crystal of air voids in a silicon background with hexagonal structure symmetry. Our results are based on the generation of discrete surface plasmon (SP) modes in the thin metallized layer residing on the top surface. This yields a series of adequately spaced discrete peaks in the reflection spectrum, dominated by a single sharp feature corresponding to the lowest plasmon order, in an otherwise uniform highly reflective spectrum (>90%) over most of the IR spectrum. This, in turn, gives rise to a sharp absorption feature with a correspondingly narrow thermal emission peak in the emission spectrum. Transfer matrix calculations simulate well both the position and strengths of the absorption peaks. By altering the period of the surface photonic lattice, the SP peak and emissive band can be tuned to the desired wavelength. These devices promise a new class of tunable infrared emitters with high power in a narrow spectral bandwidth. Such narrow band sources are critical to achieving high efficiency gas sensors. 相似文献
39.
40.
Takayuki Sakaguchi 《Optical Review》2003,10(3):136-139
We have succeeded in the operation of rotating a fine particle which was held without mechanical contact by circularly polarized laser beams with opposite propagation directions. A polystyrene latex particle 11.9 μm in diameter deformed in a disk-like shape was dispersed in water, and was trapped using the anti-parallel collinear laser beams which were set up so that they had the circular polarization rotating in the same direction. It was observed that the trapped particle rotated in the same direction as the rotation of the circular polarization of light. Inversion of the rotational direction of the circular polarization of light reversed the direction of the rotation of the particle. Although the rotational speed of a particle varied significantly from particle to particle, it was found to be proportional to the laser beam intensity. A typical value for the rotational speed per beam intensity was 2.1 Hz/W. 相似文献