全文获取类型
收费全文 | 8038篇 |
免费 | 1167篇 |
国内免费 | 658篇 |
专业分类
化学 | 5157篇 |
晶体学 | 481篇 |
力学 | 1029篇 |
综合类 | 30篇 |
数学 | 388篇 |
物理学 | 2778篇 |
出版年
2024年 | 30篇 |
2023年 | 85篇 |
2022年 | 160篇 |
2021年 | 209篇 |
2020年 | 365篇 |
2019年 | 285篇 |
2018年 | 306篇 |
2017年 | 275篇 |
2016年 | 491篇 |
2015年 | 339篇 |
2014年 | 360篇 |
2013年 | 1016篇 |
2012年 | 400篇 |
2011年 | 397篇 |
2010年 | 346篇 |
2009年 | 439篇 |
2008年 | 393篇 |
2007年 | 502篇 |
2006年 | 457篇 |
2005年 | 411篇 |
2004年 | 331篇 |
2003年 | 354篇 |
2002年 | 246篇 |
2001年 | 202篇 |
2000年 | 185篇 |
1999年 | 197篇 |
1998年 | 161篇 |
1997年 | 123篇 |
1996年 | 127篇 |
1995年 | 99篇 |
1994年 | 86篇 |
1993年 | 62篇 |
1992年 | 58篇 |
1991年 | 45篇 |
1990年 | 52篇 |
1989年 | 26篇 |
1988年 | 43篇 |
1987年 | 30篇 |
1986年 | 30篇 |
1985年 | 19篇 |
1984年 | 28篇 |
1983年 | 9篇 |
1982年 | 25篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 6篇 |
1973年 | 7篇 |
排序方式: 共有9863条查询结果,搜索用时 31 毫秒
31.
Ottokar Leminger 《Optical and Quantum Electronics》2002,34(5-6):435-443
Photonic crystals exhibit band gaps, meaning that electromagnetic fields cannot propagate in them for specific ranges of wavelengths
and directions. The calculation of band structure diagrams has been intensively studied and is now well understood. In contrast
to that, so-called wave-vector diagrams (i.e. dispersion surfaces, depicting the loci of all relevant wave vectors at a fixed
wavelength) are less known and used. In principle, they show how the effective index of the structure depends on the direction
of propagation. A method to calculate explicitly wave-vector diagrams for two-dimensional photonic crystals is derived which
leads finally to quadratic eigenvalue problems. Results for square and triangular lattices are presented and some applications
are discussed. 相似文献
32.
阐述了紫外无机非线性光学晶体分子工程学探索方法的基本特点,具体分析深紫外无机非线性光学晶体硼铍酸锶(SBBO)以氟硼铍酸钾(KBBF)为主要参考晶体的分子设计方法,随后根据晶体结构研究、单晶培养、和非线性光学性能测定等实验结果讨论SBBO作为新型深紫外无机晶体的主要优点,即它既具有更短的紫外吸收边(接近155nm)和较大的非线性光学系数(d22(SBBO)=06×d22(BBO)=138pm/V),同时晶体无明显层状习性,并肯有良好的化学稳定性和机械性能 相似文献
33.
P.A. Postigo A.R. Alija L.J. Martínez M.L. Dotor D. Golmayo J. Snchez-Dehesa C. Seassal P. Viktorovitch M. Galli A. Politi M. Patrini L.C. Andreani 《Photonics and Nanostructures》2007,5(2-3):79-85
Two-dimensional photonic crystal lasers have been fabricated on III–V semiconductor slabs. Tuning of the spontaneous emission in micro and nanocavities has been achieved by accurate control of the slab thickness. Different structures, some of them of new application to photonic crystal lasers, have been fabricated like the Suzuki-phase or the coupled-cavity ring-like resonators. Laser emission has been obtained by pulsed optical pumping. Optical characterization of the lasing modes have been performed showing one or more laser peaks centred around 1.55 μm. Far field characterization of the emission pattern has been realized showing different patterns depending on the geometrical shape of the structures. These kinds of devices may be used as efficient nanolaser sources for optical communications or optical sensors. 相似文献
34.
35.
Wei-nan E Ping-bing Ming 《应用数学学报(英文版)》2007,23(4):529-550
We study continuum and atomistic models for the elastodynamics of crystalline solids at zerotemperature.We establish sharp criterion for the regime of validity of the nonlinear elastic wave equationsderived from the well-known Cauchy-Born rule. 相似文献
36.
The contrast of interference pattern formed by two circularly polarized waves and by a linearly polarized wave and a circularly polarized one is discussed. The results are compared with that by two linear beams. It shows that the use of circular light in holographic fabrication of three-dimensional periodic microstructures may remove the necessity of beam ratio and polarization optimization needed in the interference of three linear noncoplanar beams and improve the uniform contrast of resultant pattern simultaneously. 相似文献
37.
38.
39.
40.
Haim Gvirtzman Mordeckai Magaritz Eugenia Klein Arie Nadler 《Transport in Porous Media》1987,2(1):83-93
Cold stage Scanning Electron Microscopy (SEM) with a rapid cooling technique makes it possible to investigate the water phase within unsaturated porous media. It is thought that this technique preserves the main features of the micromorphology of the water menisci as it exists in the liquid phase in soils. Saddle-shaped elements, as well as pendular rings of water, were observed with concave and convex curvatures of the water-air interface. The hydraulic conductivity of an unsaturated soil may be inferred from SEM photographs. Observations of isolated water menisci indicate the existence of an immobile water domain. The surface geometry of the water menisci was analyzed quantitatively and surface tension and capillary pressure were determined. 相似文献