全文获取类型
收费全文 | 928篇 |
免费 | 132篇 |
国内免费 | 67篇 |
专业分类
化学 | 454篇 |
晶体学 | 27篇 |
力学 | 166篇 |
综合类 | 8篇 |
数学 | 49篇 |
物理学 | 423篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 20篇 |
2021年 | 18篇 |
2020年 | 35篇 |
2019年 | 31篇 |
2018年 | 24篇 |
2017年 | 39篇 |
2016年 | 56篇 |
2015年 | 48篇 |
2014年 | 46篇 |
2013年 | 120篇 |
2012年 | 49篇 |
2011年 | 38篇 |
2010年 | 51篇 |
2009年 | 55篇 |
2008年 | 62篇 |
2007年 | 44篇 |
2006年 | 58篇 |
2005年 | 53篇 |
2004年 | 51篇 |
2003年 | 49篇 |
2002年 | 35篇 |
2001年 | 28篇 |
2000年 | 19篇 |
1999年 | 18篇 |
1998年 | 18篇 |
1997年 | 18篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有1127条查询结果,搜索用时 250 毫秒
141.
Angular distributions of CH3I fragment ions under the irradiation of single pulse and trains of ultrashort laser pulses 下载免费PDF全文
The angular distribution of CH3I is investigated experimentally using a single Fourier transform-limited laser pulse and a pulse train, where a 90-fs 800-nm linearly polarized laser field with a moderate intensity of 2.8×1013 W/cm2 is used. The dynamic alignment is demonstrated in a single pulse experiment. Moreover, a pulse train is used to optimize the molecular alignment, and the alignment degree is almost identical to that with the single pulse. The results are analysed by using chirped femtosecond laser pulses, and it demonstrates that the structure of pulse train rather than its effective duration is crucial to the molecular alignment. 相似文献
142.
The lifting Hele-Shaw cell (LHSC) is used to study adhesion as well as viscous fingering. In the present paper we report a
series of observations of development of the interface for different viscous fluids, both Newtonian and non-Newtonian, in
a LHSC operated at a constant lifting force. Glass and perspex are used as the plates in two different sets of experiments.
The objectives are 1) to measure the time required to separate the plates as a function of the lifting force and 2) to note
the force above which viscous fingering appears. We find that for the Newtonian fluids, the plate separation time follows
a universal power law with the lifting force, irrespective of fluid and substrate. The non-Newtonian fluids too, with proper
scaling obey the same power law. The appearance of fingering, however, depends on the properties of the fluid as well as the
substrate. We suggest a modified form of the capillary number which controls the onset of fingering; this new quantity, termed
the “fingering parameter” involves the dielectric constants of the substrate and fluid in addition to the viscosity and surface
tension. 相似文献
143.
Ju Hwan Lee Jonghoon Won Hae-Chang Jeong Dong Hyun Kim Dong Wook Lee Byeong-Yun Oh 《Soft Materials》2019,17(1):32-40
Liquid crystal (LC) alignment characteristics were investigated using a solution-derived lanthanum-doped zinc oxide (La:ZnO) film that was exposed to various intensities of ion-beam (IB) irradiation. At an IB intensity of 1700 eV, uniform and homogeneous LC alignment was achieved, as revealed by cross-polarized optical microscopy and pre-tilt angle measurement. Field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were used to verify that the IB irradiation induced physical and chemical surface reformation of the La:ZnO film that relate to LC alignment. FE-SEM and AFM revealed that the IB irradiation reformed the existing surface structure into a new structure with an altered surface roughness. The XPS results showed that the van der Waals force with anchoring energy increased as the IB intensity increased, and this profoundly affected the state of LC alignment. The capacitance-voltage (C-V) hysteresis curve was measured as a function of IB intensity to characterize the accumulated charge as a residual DC. Nearly zero C-V hysteresis was achieved at an IB intensity of 1700 eV. Therefore, a solution-derived La:ZnO film with an IB intensity of 1700 eV has great potential for high-quality LC applications. 相似文献
144.
145.
146.
147.
148.
Shie-Chang Jeng 《Liquid crystals》2020,47(8):1223-1231
ABSTRACT The Tamm-plasmon-polariton (TPP) occurs at the interface between a metallic film and the photonic-crystal (PC) substrate. Unlike conventional surface-plasmon-polariton (SPP), TPP can be directly excited by both the transverse electric (TE) and transverse magnetic (TM) electromagnetic waves without using additional coupling optics. The fact that the optical functionality of most plasmonics devices is determined after fabrication limits their applications. Tunable SPP devices by applying liquid crystals (LCs) have been widely demonstrated due to their large birefringence and easy controllability via external stimuli. However, actively tuning TPP is difficult because the localised electric field is between the metallic film and PC substrate, the change of refractive index above the metallic film has only small influences on TPP. This article is intended to briefly review recent progress towards using LCs for actively tuning TPP devices. Not only TPP devices can gain benefits from LCs, we will also discuss the applications of TPP for measuring the anisotropy of the alignment films of LC devices. The sensitivity of the proposed scheme will be discussed. 相似文献
149.
经过短短十年的发展,钙钛矿太阳能电池效率已经超过25%,极具商业化价值,这得益于三维(3D)钙钛矿材料具有合适的带隙、吸光系数高、电子迁移距离长等优点。但3D钙钛矿的稳定性依然是其亟待解决的问题。二维(2D)钙钛矿器件除了兼具3D钙钛矿的优异光电性质之外,其稳定性良好,是解决3D钙钛矿太阳能电池稳定性问题的一个可行方案。2D钙钛矿晶格中的疏水性大烷基胺阳离子能阻止湿气侵入的可能路径,使其成为光电器件的备选材料。由于2D钙钛矿对许多不同的有机和无机成分具有较高的耐受性,使其组成具有多样性,进而影响其能带变化。本文对2D钙钛矿的带隙调控及能带调控进行总结,希望对制备高效、稳定的低维度钙钛矿太阳能电池具有一定的指导意义。 相似文献
150.
Leandro F. Gil‐Silva Raquel Santamaría‐Fernández Prof. Dr. Armando Navarro‐Vázquez Prof. Roberto R. Gil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):472-476
A new DMSO‐compatible aligning gel based on cross‐linked poly(2‐hydroxylethyl methacrylate) (poly‐HEMA) has been developed. Due to a significant difference in bulk magnetic susceptibility between the DMSO inside and outside the gel, it is possible to simultaneously collect isotropic and anisotropic NMR data, such as residual dipolar couplings (RDC), in the same NMR tube. RDC‐assisted structural analysis of menthol and the alkaloid retrorsine is reported as proof of concept. 相似文献