全文获取类型
收费全文 | 350篇 |
免费 | 5篇 |
国内免费 | 11篇 |
专业分类
化学 | 70篇 |
力学 | 3篇 |
数学 | 134篇 |
物理学 | 110篇 |
无线电 | 49篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 11篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 12篇 |
2012年 | 21篇 |
2011年 | 22篇 |
2010年 | 20篇 |
2009年 | 14篇 |
2008年 | 21篇 |
2007年 | 13篇 |
2006年 | 14篇 |
2005年 | 19篇 |
2004年 | 14篇 |
2003年 | 12篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 17篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1970年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有366条查询结果,搜索用时 15 毫秒
141.
We show, by using numerical simulations, that self-similar pulses with a duration on the order of few nanoseconds and an energy on the order of 10?μJ can be obtained at the output of a fiber Bragg grating (FBG) written in a fiber amplifier. The evolution of the amplified pulses is determined by the combined effect of Kerr nonlinearity, normal-dispersion, gain, and gain saturation, which limit the pulse energy. The output pulse mainly depends on the initial pulse energy rather than on the initial pulse profile. The reduced group velocity in FBGs can significantly increase the total gain for a given amplifier length. Hence we find that the proposed amplification scheme can be highly advantageous for amplification of nanosecond-scale pulses in fiber amplifiers. 相似文献
142.
A multiplicative secret sharing scheme allows players to multiply two secret-shared field elements by locally converting their shares of the
two secrets into an additive sharing of their product. Multiplicative secret sharing serves as a central building block in
protocols for secure multiparty computation (MPC). Motivated by open problems in the area of MPC, we introduce the more general
notion of d-multiplicative secret sharing, allowing to locally multiply d shared secrets, and study the type of access structures for which such secret sharing schemes exist. 相似文献
143.
Nonequilibrium bosonization technique is used to study current fluctuations of interacting electrons in a single-channel quantum wire representing a Luttinger liquid (LL) conductor. An exact expression for the time resolved full counting statistics of the transmitted charge is derived. It is given by the Fredholm determinant of the counting operator with a time-dependent scattering phase. The result has a form of counting statistics of noninteracting particles with fractional charges, induced by scattering off the boundaries between the LL wire and the noninteracting leads. 相似文献
144.
145.
A one-dimensional system of interacting electrons out of equilibrium is studied in the framework of the Luttinger liquid model. We analyze several setups and develop a theory of tunneling into such systems. A remarkable property of the problem is the absence of relaxation in energy distribution functions of left and right movers yet the presence of the finite dephasing rate due to electron-electron scattering, which smears zero-bias-anomaly singularities in the tunneling density of states. 相似文献
146.
We study the effect of a noisy environment on spin and charge transport in ballistic quantum wires with spin-orbit coupling (Rashba coupling). We find that the wire then acts as a dephasing diode, inducing very different dephasing of the spins of right and left movers. We also show how Berry phase (geometric phase) in a curved wire can induce such asymmetric dephasing, in addition to purely geometric dephasing. We propose ways to measure these effects through spin detectors, spin-echo techniques, and Aharanov-Bohm interferometry. 相似文献
147.
We study the interaction between two Bragg solitons in the vicinity of a defect inside a fiber Bragg grating. A soliton that is trapped in the defect can be released by launching a second soliton. The effect can be used to obtain an all-optical memory that is not strongly sensitive to the phase and the timing arrival of the solitons. 相似文献
148.
The empirical entropy is a key statistical measure of data frequency vectors, enabling one to estimate how diverse the data are. From the computational point of view, it is important to quickly compute, approximate, or bound the entropy. In a distributed system, the representative (“global”) frequency vector is the average of the “local” frequency vectors, each residing in a distinct node. Typically, the trivial solution of aggregating the local vectors and computing their average incurs a huge communication overhead. Hence, the challenge is to approximate, or bound, the entropy of the global vector, while reducing communication overhead. In this paper, we develop algorithms which achieve this goal. 相似文献
149.
The electrical conductivity process in a new class of ion-containing polymers—highly concentrated solid solutions of hydrated perchlorate salts in polyacrylonitrile (PAN)—is described (σdc = 10?7?10?2Ω?1cm?1). A low-ac instrument (70 cps) is used to measure electrical conductivity. We present a cryogenic system in which the temperature dependence of the conductivity is studied (78–340°K). The ionic character of the conductivity process is established. The conductivity both above and below the glass-transition (Tg) point is thermally activated with an activation energy of 0.7–0.9 e V for the glassy state (?g) and 0.12–0.6 eV for the rubber-like state (?r). The systems described exhibit a compensation effect between the pre-exponential factor for the conductivity in the glassy state σ0g and the difference in activation energy ?g – ?r 相似文献
150.
The extended physical theory of diffraction (EPTD), which is an extension of Ufimtsev's (1962) theory to aperture integration, is formulated in terms of incremental diffraction coefficients (IDC). Closed-form expressions for these coefficients are derived. The utility of the derived IDC is exemplified in a calculation of the cross-polar pattern of a parabolic reflector 相似文献