全文获取类型
收费全文 | 148篇 |
免费 | 3篇 |
专业分类
化学 | 31篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 12篇 |
物理学 | 104篇 |
出版年
2020年 | 1篇 |
2019年 | 3篇 |
2017年 | 1篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 6篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 6篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 8篇 |
2003年 | 2篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 1篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有151条查询结果,搜索用时 390 毫秒
11.
The band structure of graphene ribbons with zigzag edges have two valleys well separated in momentum space, related to the two Dirac points of the graphene spectrum. The propagating modes in each valley contain a single chiral mode originating from a partially flat band at the band center. This feature gives rise to a perfectly conducting channel in the disordered system, if the impurity scattering does not connect the two valleys, i.e., for long-range impurity potentials. Ribbons with short-range impurity potentials, however, through intervalley scattering display ordinary localization behavior. The two regimes belong to different universality classes: unitary for long-range impurities and orthogonal for short-range impurities. 相似文献
12.
We present the first photoacoustic spectrometer for gas sensing employing both the fundamental and the frequency-doubled radiation
of a continuously tunable high-pressure CO2 laser with room temperature operation. A quasi-phase-matched diffusion-bonded GaAs crystal is used in the system for second-harmonic
generation. A pulsed photoacoustic detection scheme with a non-resonant cell, equipped with an 80-microphone array, is employed.
The wide continuous tuning range in the fundamental (9.2–10.7 μm) and the frequency-doubled (4.6–5.35 μm) regimes, together
with the narrow linewidth of 540 MHz (0.018 cm-1) for the 10-μm region and of 1050 MHz (0.0315 cm-1) for the 5-μm region, allow the measurement of gas mixtures, individual species and isotope discrimination. This is illustrated
with measurements on NO and CO2. The measured isotope ratio 15
NO/14
NO=(3.58±0.55)×10-3 agrees well with the literature (3.700×10-3) and demonstrates the good selectivity of the system.
Received: 30 April 2002 / Revised version: 10 June 2002 / Published online: 2 September 2002
RID="*"
ID="*"Corresponding author. Fax: +41-1/633-1077, E-mail: sigrist@iqe.phys.ethz.ch 相似文献
13.
We present a new mid-infrared laser spectrometer for high-precision measurements of isotopic ratios of molecules at ppm concentrations.
Results are discussed for nitrous oxide (N2O), where a precision of 3‰ for a single measurement and a reproducibility of 6‰ have been achieved for a concentration of
825 ppm. The room-temperature laser source employed is based on difference-frequency generation delivering a continuous-wave
power up to 23 μW at wavelengths between 4.3 μm and 4.7 μm and a line width of 1 MHz. Two different measurement methods are
compared; wavelength modulation with first-harmonic detection and direct absorption spectroscopy by recording the spectrum
with a data-acquisition card. Two different detection schemes were employed; either all isotopomers were measured using the
long path (36 m) of the multipass cell or a balanced path length detection scheme was used, where the main isotope was measured
with a beam along a shorter path (40 cm) in the multipass cell. A single-pass reference cell was designed, offering two different
path lengths for balanced path length detection. All combinations of measurement methods and detection schemes were tested
regarding precision of a single measurement and long-term stability. The advantages and disadvantages of various measurement
approaches are discussed.
PACS 42.62.Fi; 42.65.Ky; 32.10.Bi 相似文献
14.
The symmetry classification of possible singlet and also triplet states in the case of the 2-dim square lattice, and 3-dim tetragonal and orthorhombic lattices is examined. If particle-hole symmetry is present then an additional symmetry classification is possible. However in the lower symmetry crystal structures that actually occur, no distinction on symmetry grounds can be drawn between usuals-wave, extendeds-wave and some of thed-wave states. 相似文献
15.
A new method named photothermal diffuse reflectance (PTDR) is presented. This method combines the diffuse reflectance spectroscopy with the photothermal technique and is particularly suited for the investigation of strongly scattering samples. This method takes advantage of the high spectral selectivity and absorption of the mid-infrared region with the larger scattering cross section and high detector sensitivity available in the near-infrared. A model describing the PTDR method is proposed and supported with experimental results. The potential of the PTDR technique is illustrated by experimental signals obtained from various scattering media like polymers, liquids and powders. 相似文献
16.
3 is reported. Using an external cavity diode laser, tunable from 795 to 825 nm, and a cw diode-pumped Nd:YAG ring laser at
1064 nm, we produced narrowband mid-ir laser light between 3.16 and 3.67 μm. This broad tuning range of 440 cm-1 can be critically phase-matched by changing the external crystal angle within a range of only 0.4°. Even for a fixed crystal
angle broadband phase-matching over 230 cm-1 was achieved. No realignment was required when tuning the laser over the whole wavelength range, which enabled the use of
a compact 36-m multipass cell as gas chamber. The conversion efficiency could be improved by almost a factor of 3 by applying
noncollinear instead of collinear phase-matching, resulting in 30 nW of idler power with good beam quality. Spectra of methane
were recorded in laboratory air, which demonstrate the rapid and continuous broad tunability at high sensitivity, enabling
sub-ppm detection. Finally, wavelength modulation spectroscopy at high resolution was applied as a promising tool for further
inproving the performance of this laser spectrometer.
Received: 16 March 1998/Revised version: 1 July 1998 相似文献
17.
We report, between 0.32 and 5.50 eV, the optical conductivity of polycrystalline thin films of molybdenum. The films have been deposited in ultra high vacuum and the measurements have been carried out in situ. We observe two maxima at 2.75 and 4.0 eV and two shoulders at 1.85 and 5.1 eV. The structure is understood in terms of interband transitions, the conductivity is compared to a joint density of states histogram deduced from Petroff and Viswanathan energy bands. 相似文献
18.
Joseph Hersch Karl Sigrist 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1970,21(5):836-841
Summary Some isoperimetric inequalities for vibrating membranes are extended to an elastically supported boundary, using conformal transplantation. A further inequality for fixed-free boundaries is given in section 3. 相似文献
19.
The minimal energy loss (dE/d ζ)k [MeV cm2/mg] for the formation of a track in an insulator has been determined for mica, tourmaline, quartz glass, quartz crystal, lithium niobate and beryl. The investigations show that the (dE/d ζ)k value of a track detector can be roughly estimated from the thermal conductivity of the given material. 相似文献
20.
R. Roldán A. Rüegg M. Sigrist 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(2):185-192
Metamagnetism in layered ruthenates has been interpreted as a novel kind of quantum critical behavior. In an external magnetic
field, Ca2-xSrxRuO4 undergoes a metamagnetic transition accompanied by a pronounced magnetostriction effect. In this paper we present a mean-field
study for a microscopic model that naturally reproduces the key features of this system. The phase diagram calculated is equivalent
to the experimental T-x phase diagram. The presented model also gives a good basis to discuss the critical metamagnetic behavior measured in the
system. 相似文献