全文获取类型
收费全文 | 450篇 |
免费 | 10篇 |
国内免费 | 10篇 |
专业分类
化学 | 136篇 |
晶体学 | 2篇 |
力学 | 110篇 |
综合类 | 2篇 |
数学 | 26篇 |
物理学 | 194篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 8篇 |
2017年 | 15篇 |
2016年 | 11篇 |
2015年 | 5篇 |
2014年 | 14篇 |
2013年 | 22篇 |
2012年 | 11篇 |
2011年 | 22篇 |
2010年 | 16篇 |
2009年 | 28篇 |
2008年 | 30篇 |
2007年 | 36篇 |
2006年 | 29篇 |
2005年 | 19篇 |
2004年 | 23篇 |
2003年 | 19篇 |
2002年 | 18篇 |
2001年 | 22篇 |
2000年 | 12篇 |
1999年 | 15篇 |
1998年 | 16篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有470条查询结果,搜索用时 604 毫秒
61.
L. S. Pan H. P. Lee C. Lu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,50(1):27-33
We report the synthesis and measurement of an
ultra-precise and extremely stable optical frequency in the
telecommunications window around 1543 nm. Using a fibre-based femtosecond
frequency comb we have phase-stabilised a fibre laser at 194 THz to an
optical frequency standard at 344 THz, thus transferring the properties of
the optical frequency standard to another spectral region. Relative to the
optical frequency standard, the synthesised frequency at 194 THz is
determined to within 1 mHz and its fractional frequency instability is
measured to be less than 2×10-15 at 1 s, reaching 5×
10-18 after 8000 s. We also measured the synthesised frequency against
a caesium fountain clock: here the frequency comparison itself contributes
less than 4 mHz (2×10-17) to the uncertainty. Our results
confirm the suitability of fibre based frequency comb technology for
precision measurements and frequency synthesis, and enable long-distance
comparison of optical clocks by using optical fibres to transmit the
frequency information. 相似文献
62.
An integrated optical coupler used in a fibre interferometry system for on-line surface measurements
In this paper, an integrated optical (IO) coupler produced using the technique of silica-on-silicon was described. A fibre interferometry system using the IO coupler was then developed and its performance was tested. The environmental noise and disturbances in this system were reduced significantly after combining a reference interferometer and an all fibre polarisation scrambler so as to produce good stability and repeatability. Furthermore, the measurement mirror was mounted on a piezoelectric transducer (PZT) and disturbances were introduced in the system in order to simulate on-line surface measurements. Both a commercial fibre and the IO couplers were compared using this method. Better experimental results were achieved when the system using the IO coupler than using the fibre one. 相似文献
63.
Stephen J. Mihailov Dan Grobnic Robert B. Walker Christopher W. Smelser Gino Cuglietta Tom Graver Alexis Mendez 《Optics Communications》2008,281(21):5344-5348
Bragg gratings are written with ultrafast 800 nm radiation and a phase mask through the polyimide polymer coatings of commercially available high NA fibres that are both unloaded and loaded with high pressure hydrogen gas. For polyimide coated fibres with very high germanium core concentrations, index modulations greater than 1 × 10−4 are induced. Stable core index modulations 60% of their original value were present after 115 h at 500 °C. 相似文献
64.
Liquid-liquid-solid systems are becoming increasingly common in everyday life with many possible applications. Here, we focus on a special case of such liquid-liquid-solid systems, namely, capillary suspensions. These capillary suspensions originate from particles that form a network based on capillary forces and are typically composed of solids in a bulk liquid with an added secondary liquid. The structure of particle networks based on capillary bridges possesses unique properties compared with networks formed via other attractive interactions where these differences are inherently related to the properties of the capillary bridges, such as bridge breaking and coalescence between adjacent bridges. Thus, to tailor the mechanical properties of capillary suspensions to specific requirements, it is important to understand the influences on different length scales ranging from the dynamics of the bridges with varying external stimuli to the often heterogeneous network structure. 相似文献
65.
《Current Applied Physics》2020,20(5):720-737
Roll-to-roll (R2R) production is an innovative approach and is fast becoming a very popular industrial method for high throughput and mass production of solar cells. Replacement of costly indium tin oxide (ITO), which conventionally has served as the transparent electrode would be a great approach for roll to roll production of flexible cost effective solar cells. Indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) are brittle and ultimately limit the device flexibility. Perovskite solar cells (PSCs) have been the centre of photovoltaic research community during the recent years owing to its exceptional performance and economical prices. The best reported PSCs fabricated by employing mesoporous TiO2 layers require elevated temperatures in the range of 400–500 °C which limits its applications to solely glass substrates. In such a scenario developing flexible PSCs technology can be considered a suitable and exciting arena from the application point of view, them being flexible, lightweight, portable, and easy to integrate over both small, large and curved surfaces. 相似文献
66.
《Comptes Rendus Chimie》2016,19(9):1062-1070
Plant cell cultures constitute pesticide-free sources for obtaining plant secondary metabolites or plant extracts. Additionally, they do not contain any fungal contaminants, mycotoxins or heavy metals providing to the consumer potential health benefits and justifying the development of this technology at an industrial scale. Significant production levels of these secondary metabolites can be obtained through the use of elicitors, which activate plant defense mechanisms. Resveratrol, a well-known grapevine polyphenolic compound which possesses potent antioxidant and antiaging activities as well as a protective action on skin, is a good example of such plant secondary metabolites. Resveratrol and its oligomeric derivatives are used by several companies of cosmetic products but their extraction from vine stems and similar vegetal sources remains difficult. Therefore grapevine cell suspensions could represent interesting systems for the large-scale bioproduction of those compounds. Here we present an update of the methods used for the production of phytostilbenes by using grapevine cell cultures and the results obtained. 相似文献
67.
68.
The zeta potential of kaolin suspensions measured by electrophoresis and electroacoustics 总被引:1,自引:0,他引:1
The zeta potentials of kaolin dilute and concentrated suspensions were monitored using the techniques of electrophoresis and
electroacoustics, respectively. The effect of addition of salt (KCl), a polymer material (Triton X-100), and an anionic surfactant
(sodium dodecyl sulphate, SDS) on the suspension properties was investigated by electrophoresis. Electroacoustics was employed
for the measurement of zeta potentials for the highest possible kaolin content in suspension and the effect of dilution. The
effect of aging of a freshly prepared sample and kaolin isoelectric point was also studied. Using both techniques it was noted
that there was no isoelectric point, just a maximum value in the magnitude of the kaolin suspension zeta potential. These
maxima were observed also in the presence of Triton X-100 and SDS. An increase of the concentration of KCl and SDS in suspension
shifted the maxima towards more acidic values, while in the presence of Triton X-100 the position of the zeta potential maxima
remained constant. Electroacoustic techniques revealed that a freshly prepared concentrated suspension requires about six
hours to equilibrate to achieve a steady zeta potential. Diluting the concentrated suspensions led to decrease of the zeta
potential as ions bound to the surface desorbed and screened the surface charge. The zeta potential maxima remained unchanged
even after heating the powder in an oven at 200°C (to remove any organic material) thereby suggesting that the most likely
explanation for the maxima is isomorphic substitution. 相似文献
69.
R. S. Huerfano M. A. López M. Socolovsky 《International Journal of Theoretical Physics》2007,46(11):2961-2966
We show that the connection responsible for any Abelian or non-Abelian Aharonov–Bohm effect with n parallel “magnetic” flux lines in ℝ3, lies in a trivial G-principal bundle P→M, i.e. P is isomorphic to the product M×G, where G is any path connected topological group; in particular a connected Lie group. We also show that two other bundles are involved:
the universal covering space
, where path integrals are computed, and the associated bundle P×
G
ℂ
m
→M, where the wave function and its covariant derivative are sections. 相似文献
70.
Al-Mg MMH溶胶和钠土悬浮体的相互作用机理 总被引:1,自引:0,他引:1
通过流变参数、电泳淌度和pH值的测定,研究了无机盐(CaCl2、KCl、NaCl)和pH值对铝镁混合金属氢氧化物与钠土悬浮体间相互作用的影响。发现随着混合金属氢氧化物含量的增加,钠土体系的pH值逐渐降低,而动切力(YP)先上升,经最大值后逐渐下降;当钠土体系为NaCl所饱和时,相同混合金属氢氧化物加量下YP的上升幅度明显减小,在实验混合金属氢氧化物浓度范围内,YP未出现峰值。混合金属氢氧化物/钠土体系的YP随pH值的变化曲线呈抛物线形,加入相同浓度的无机盐,△YP、△pH(绝对值)按CaCl2KCl~NaCl次序递减。 相似文献