全文获取类型
收费全文 | 1315篇 |
免费 | 274篇 |
国内免费 | 15篇 |
专业分类
化学 | 133篇 |
晶体学 | 15篇 |
力学 | 15篇 |
综合类 | 1篇 |
数学 | 5篇 |
物理学 | 1435篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 17篇 |
2020年 | 20篇 |
2019年 | 16篇 |
2018年 | 23篇 |
2017年 | 45篇 |
2016年 | 44篇 |
2015年 | 33篇 |
2014年 | 57篇 |
2013年 | 47篇 |
2012年 | 52篇 |
2011年 | 85篇 |
2010年 | 69篇 |
2009年 | 65篇 |
2008年 | 107篇 |
2007年 | 92篇 |
2006年 | 77篇 |
2005年 | 57篇 |
2004年 | 57篇 |
2003年 | 42篇 |
2002年 | 92篇 |
2001年 | 43篇 |
2000年 | 47篇 |
1999年 | 32篇 |
1998年 | 29篇 |
1997年 | 37篇 |
1996年 | 34篇 |
1995年 | 35篇 |
1994年 | 15篇 |
1993年 | 14篇 |
1992年 | 10篇 |
1991年 | 16篇 |
1990年 | 13篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1987年 | 20篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 16篇 |
1982年 | 22篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有1604条查询结果,搜索用时 15 毫秒
61.
L. Wu S. Zhu Y. Ni 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):349-354
Combination of two basic types of synchronization, anticipatory
synchronization and lagged synchronization, is investigated
numerically between two coupled semiconductor lasers. It is found
that lagged synchronization produced by a backward coupling with a
suitable delay can combine with the originally hidden anticipatory
synchronization and produce a type of synchronization overcoming the
original lagged synchronization produced by a forward coupling. We
study the combination synchronization phenomenon when the delay of
the backward coupling is different from that of the original
anticipatory synchronization. Our results suggest that the
synchronization combination phenomenon might allow an interpretation
of an experimental observation by Sivaprakasam et al. [Phys.
Rev. Lett. 87, 154101 (2001)] that the anticipating time is
irrespective of the external-cavity round trip time, which to date remains to be understood. 相似文献
62.
Optical model, scalar or vectorial one, describing behaviour of an optical field within a diode-laser cavity, is one of the
most important parts of modelling of a diode-laser operation. As compared to more accurate vectorial optical approaches, scalar
ones are known to be less exact but simultaneously they need much less computation time. Besides, they have been sometimes
found to be surprisingly exact even beyond their confirmed range of validity. Therefore, in this paper, real validity limits
of their application have been determined by comparing their simplified results with more exact results obtained with the
aid of vectorial models. The analysis comprises a comparison of an application of the most popular scalar approach to optical
properties of diode lasers, i.e., the effective index method, and the vectorial method of lines for the standard 1.3-μm GaAs-based
stripe-geometry diode laser. The scalar model has been found to be quite exact in the case of a determination of the effective
refractive index, i.e., the wavelength of emitted radiation, whereas its exactness in the lasing threshold analysis is much
worse, especially in the case of higher-order modes. Our analysis is concluded with a determination of the regions where both
models give satisfactorily close results. 相似文献
63.
A dual mode multi-section gain-coupled distributed feedback laser with tunable mode spacing is subharmonically injection locked at 0.315 THz. The injected signal consists of an optical comb with harmonics 35 GHz apart and a bandwidth of approximately 1.9 THz. The optical comb is a result of strong four-wave mixing in a highly-nonlinear dispersion-shifted fiber. In order to observe locking of the multi-section laser, the output is optically downconverted to RF frequencies using the same optical comb. The locked multi-section DFB laser is a coherent and tunable optical source suitable for continuous-wave terahertz generation systems. 相似文献
64.
Guanshi Qin Tatsuya Yamashita Yusuke Arai Yasutake Ohishi 《Optics Communications》2007,279(2):298-302
We demonstrate a 22 dB all-fiber amplifier at 546 nm using Er3+-doped fluoride fiber by forward upconversion pumping of a 974 nm laser diode. The gain saturation effects and the power conversion efficiency of this amplifier are investigated in detail based on gain characteristics and numerical simulations. 相似文献
65.
The aim of this paper is to investigate the effects of external optical injection taking account of polarization and electron spin properties in vertical-cavity surface-emitting lasers (VCSELs). Using external polarized injection we seek the locked phases and amplitudes of specific polarized fields in terms of injection level and frequency detuning, taking account of two kinds of distinguishable carrier density (spin-up and spin-down). For the conventional form of optical injection without taking account of spin-polarized fields there are three fundamental equations describing the carrier density, field amplitude and phase. However, by using the spin flip model (SFM), the combined effect of polarized fields along two perpendicular crystal axes and electron spin properties results in six equations. We analyse the conditions for stable locking and also the influence of birefringence effects on the stability map of detuning versus optical injection for both cases of injection polarized parallel and perpendicular to the lasing mode of the solitary VCSEL. For given values of pumping and spin relaxation rate there is a minimum birefringence rate for orthogonal injection. Above this value three regions of elliptical polarization are found in the stability map, namely “quasi-stability” (QS), “coupled limit cycle” (CLC) and “coupled chaos” (CC). The three regions of linear polarization, namely chaos, limit cycle and stability, are reduced in area compared to the case of parallel injection. For orthogonal injection it is found that increased birefringence or reduced spin relaxation rate causes the stable locking region to begin at higher injected power and frequency detuning. 相似文献
66.
V.A. Kheraj C.J. Panchal P.K. Patel B.M. Arora T.K. Sharma 《Optics & Laser Technology》2007,39(7):1395-1399
The optical output power of a laser diode can be enhanced by anti-reflection (AR) and high-reflection (HR) facet coatings, respectively, at the front and back facet. AR and HR coatings also serve the purpose of protection and passivation of laser diode facets. In this work, we have designed and optimized a single layer λ/4 thick Al2O3 film for the AR coating and a stack of λ/4 thick Al2O3/λ/4 thick Si bi-layers for the HR coating for highly strained InGaAs quantum-well edge emitting broad area (BA) laser diodes. Effect of the front and back facet reflectivities on output power of the laser diodes has been studied. The light output versus injected current (L–I characteristics) measurements were carried out on selected devices before and after the facet coatings. We have also carried out the numerical simulation and analysis of L–I characteristics for this particular diode structure. The experimental results have been compared and verified with the numerical simulation. 相似文献
67.
It is predicted theoretically that broadening the optical confinement layer in monolithic mode-locked semiconductor lasers
may suppress Q-switching instability, by increasing the carrier transport time, and lead to emission of shorter, more stable
optical pulses. 相似文献
68.
Unraveling of all of the information contained in proteomes poses a tremendous chemical challenge, which is balanced by the promise of potentially transformational knowledge. Mass spectrometry offers an unprecedented arsenal of tools for diverse proteomic investigations. Recently, it was demonstrated that ultraviolet light can be utilized to initiate unique and potentially useful fragmentations in peptides and proteins. Either nonspecific dissociation or highly specific dissociation at engineered chromophoric sites is possible following photon absorption. The level of specificity and control over fragmentation in these experiments is greater than with other fragmentation methods. Novel techniques made possible by this technology are poised to make substantial contributions to the field of proteomics. 相似文献
69.
The Raman spectrum of any molecule consists of two mirror-image signals, th e Stokes and anti-Stokes Raman spectra. In most cases, unless highly specific sampling conditions are used, the anti-Stokes signal is much weaker than that of the Stokes. The recent application of intensified diode array detectors to Raman spectroscopy has produced a marked increase in the sensitivity of the technique which makes a study of the anti-Stokes spectrum potentially more rewarding than it has been to date. The present study has shown that, although of limited use for general purposes, there are some specific instances where the anti-Stokes spectrum can be of considerable practical use. Such applications are to extend the operating range of the Raman spectrometer, to study photodegradable samples and for the analysis of samples which exhibit strong fluorescence. 相似文献
70.