全文获取类型
收费全文 | 3746篇 |
免费 | 983篇 |
国内免费 | 333篇 |
专业分类
化学 | 1179篇 |
晶体学 | 23篇 |
力学 | 539篇 |
综合类 | 45篇 |
数学 | 526篇 |
物理学 | 2750篇 |
出版年
2024年 | 14篇 |
2023年 | 53篇 |
2022年 | 87篇 |
2021年 | 67篇 |
2020年 | 94篇 |
2019年 | 91篇 |
2018年 | 121篇 |
2017年 | 143篇 |
2016年 | 137篇 |
2015年 | 164篇 |
2014年 | 288篇 |
2013年 | 282篇 |
2012年 | 290篇 |
2011年 | 340篇 |
2010年 | 252篇 |
2009年 | 247篇 |
2008年 | 279篇 |
2007年 | 294篇 |
2006年 | 259篇 |
2005年 | 230篇 |
2004年 | 181篇 |
2003年 | 170篇 |
2002年 | 122篇 |
2001年 | 110篇 |
2000年 | 91篇 |
1999年 | 72篇 |
1998年 | 85篇 |
1997年 | 74篇 |
1996年 | 68篇 |
1995年 | 73篇 |
1994年 | 44篇 |
1993年 | 40篇 |
1992年 | 52篇 |
1991年 | 34篇 |
1990年 | 22篇 |
1989年 | 16篇 |
1988年 | 8篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有5062条查询结果,搜索用时 62 毫秒
11.
An optical fiber multi-function device consisting of a single gradient-index-rod lens and a multi-facet blazed reflection
grating is proposed to simultaneously realize functions of wavelength demultiplexing and optical signal distribution in a
multimode optical fiber transmission system. We analyzed the demultiplexing characteristics and the tolerance of optical components
using the ray trace method. This device can realize not only low loss optical signal distribution but also offers improved
demultiplexing characteristics in comparison with the previously proposed demultiplexer-multiposition switch. The following
characteristics are expected from the design using commercially available optical components: a working band of 0.64–0.88
μm, channel separation of 34–36 nm, 3 dB bandwidth of 27–28 nm, channel cross-talk of less than - 40 dB and minimum excess
insertion loss of 0.9–2.1 dB. 相似文献
12.
An infinite row of periodically spaced, identical rigid circularcylinders is excited by an acoustic line source which is parallelto the generators of the cylinders. A method for calculatingthe scattered field accurately and efficiently is presented.When the cylinders are sufficiently close together, Rayleigh–Blochsurface waves that propagate energy to infinity along the arrayare excited. An expression is derived which enables the amplitudesof these surface waves to be computed without requiring thesolution to the full scattering problem. 相似文献
13.
Curved Ferroelectric Liquid Crystal Matrix Displays Driven by Field-Sequential-Color and Active-Matrix Techniques 总被引:1,自引:0,他引:1
Hideo Fujikake Hiroto Sato Takeshi Murashige Yoshihide Fujisaki Taiichiro Kurita Tadahiro Furukawa Fumio Sato 《Optical Review》2006,13(1):14-19
This paper describes a curved field-sequential-color matrix display using fast-response ferroelectric liquid crystal. Black
matrix and transparent electrode patterns were formed on a thin plastic substrate by a transfer method from a glass substrate.
While a composite film of liquid crystal and micro-polymers of walls and fibers was formed between the flexible substrates
by printing, laminating and curing processes of a solution of monomers and liquid crystal, the mechanical stability was enhanced
by use of multi-functional monomers to form large display panels. The image pixels of the matrix panel were driven by an active
matrix scheme using an external switch transistor array at a frequency of 180 Hz for intermittent three-primary-color backlight
illumination. The flexible A4-paper-sized color display with 24 × 16 pixels and 60 Hz field frequency was demonstrated by
illuminating it with sequential three-primary-color lights from light-emitting diodes of the backlight. Our display system
is useful in various information displays because of its freedom of setting and location. 相似文献
14.
15.
16.
设{Xni:1≤i≤n,n≥1}为行间独立的B值r.v.阵列,g(z)是指数为1/p的正则变化函数,r>0,{ani 1≤t≤n,n≥1}为实数阵列,本文得到了使(?)成立的条件,推广并改进了Stout及Sung等的著名结论. 相似文献
17.
18.
19.
20.
在空间电荷主导电子束研究中,纵向聚焦非常重要,在输运过程中由于强空间电荷力的影响,束团将很快变长并崩溃,马里兰大学的电子环设计用于方形束团和抛物线形束团的研究,环中需要用三个感应腔对束团进行纵向聚焦.文中首先介绍了方形束团和抛物线形束团的纵向束流动力学,推导了两种束团纵向聚焦所需要的5MHz重复率高压脉冲波形,并给出了实现纵向聚焦的感应腔设计及其特殊要求. 相似文献