全文获取类型
收费全文 | 396篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
化学 | 290篇 |
力学 | 4篇 |
数学 | 7篇 |
物理学 | 100篇 |
出版年
2024年 | 1篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 9篇 |
2012年 | 14篇 |
2011年 | 20篇 |
2010年 | 15篇 |
2009年 | 11篇 |
2008年 | 19篇 |
2007年 | 21篇 |
2006年 | 30篇 |
2005年 | 20篇 |
2004年 | 18篇 |
2003年 | 10篇 |
2002年 | 22篇 |
2001年 | 15篇 |
2000年 | 10篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 14篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有401条查询结果,搜索用时 187 毫秒
41.
We studied the quantum interference of electrons in the Bi (p(x), p(y)) orbital-derived j = 1/2 spin-split surface states at Bi/Ag(111)√3 × √3 surfaces of 10 monolayer thick Ag(111) films on Si(111) substrates. Surface electron standing waves were observed clearly at the energy (E) below the intersection of the two spin-split downward dispersing parabola bands (E(x)). The E dependence of the standing wave pattern reveals the dispersion as the average of the two spin-split surface bands due to the interference between |(k + Δ), ↑> and |-(k - Δ), ↑> [or (|(k - Δ), ↓>) and |-(k + Δ), ↓>] states. In contrast, it was impossible to deduce the dispersion from the standing wave pattern at E ≥ E(x) because the surface electron cannot find its backscattered state with the same spin polarization. 相似文献
42.
Takashina K Niida Y Renard VT Fujiwara A Fujisawa T Muraki K Hirayama Y 《Physical review letters》2011,106(19):196403
We examine the temperature dependence of resistivity in a two-dimensional electron system formed in a silicon-on-insulator quantum well. The device allows us to tune the valley splitting continuously in addition to the electron density. Our data provide a global picture of how the resistivity and its temperature dependence change with valley polarization. At the boundary between valley-polarized and partially polarized regions, we demonstrate that there is an insulating contribution from spin-degenerate electrons occupying the upper valley-subband edge. 相似文献
43.
A method is proposed for obtaining the spectrum for noise that causes the phase decoherence of a qubit directly from experimentally available data. The method is based on a simple relationship between the spectrum and the coherence time of the qubit in the presence of a π pulse sequence. The relationship is found to hold for every system of a qubit interacting with the classical-noise, bosonic, and spin baths. 相似文献
44.
We study the Unruh effect on the dynamics of quarks and mesons in the context of AdS5/CFT4 correspondence. We adopt an AdS5 metric with the boundary Rindler horizon extending into a bulk Rindler-like horizon, which yields the thermodynamics with Unruh temperature verified by computing the boundary stress tensor. We then embed in it a probe fundamental string and a D7 brane in such a way that they become the dual of an accelerated quark and a meson in Minkowski space, respectively. Using the standard procedure of holographic renormalization, we calculate the chiral condensate, and also the spectral functions for both the accelerated quark and meson. Especially, we extract the corresponding strength of random force of the Langevin dynamics and observe that it can characterize the phase transition of meson melting. This result raises an issue toward a formulation of complementarity principle for the Rindler horizon. We find most of the dynamical features are qualitatively similar to the ones in the thermal bath dual to the AdS black hole background, though they could be quite different quantitatively. 相似文献
45.
46.
The X-ray crystal structure of the title complex, Co(Cl2bprpi) is described. In this complex the Co(II) center displays a distorted octahedral coordination geometry. The piperazine ring exhibits boat conformation, forming chelate rings and capping the Co atom. The N2-Col-N3 angle is 69.41(15) degrees, extremely smaller than 90 degrees. Because the small angle causes a large steric hindrance, the piperazine ring can be effective as an ion size-recognition site. The molecular structure is stabilized by intramolecular N-H...O hydrogen bonds and Cl...H contacts. 相似文献
47.
48.
In this paper, we consider polling systems with J stations with Poisson arrivals and general service distributions attended by a cyclic server. The service discipline at each station is either exhaustive or gated. We propose a new approach to analysis of the mean waiting times in the polling systems. The outline of our method is as follows. We first define the stochastic process Q that represents an evolution of the system state, and define three types of the performance measures W i ,H i and F i , which are the expected waiting times conditioned on the system state. Then from the analysis of customers at polling instants, we find their linear functional expressions. The steady state average waiting times can be derived from the performance measures by simple limiting procedures. Their actual values can be obtained by solving J(J+1) linear equations. 相似文献
49.
Andreas Richter Ken-ichi Matsuda Tatsushi Akazaki Tadashi Saku Hiroyuki Tamura Yoshiro Hirayama Hideaki Takayanagi 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):472-478
We present studies on the electric transport in a lateral GaAs/AlGaAs quantum dot defined by a patterned single connected metallic front-gate. This gate design allows to easily couple a large number of quantum dots and therefore holds high potential in the design of new materials with tailor-made band structures based on quantum dot superlattices of controlled shape. Clear Coulomb diamond structures and well pronounced tunneling peaks observed in experiment indicate that single-electron control has been achieved. However, the dependence on electron density in the heterostructure embedding the dot, which is controlled by an additional back-gate, reveals that transport characteristics are strongly influenced supposedly by potential fluctuations in the dot and lead regions. 相似文献
50.
Toshikazu Kaise Hiroshi Yamauchi Yoshiya Horiguchi Takayuki Tani Shigenobu Watanabe Teruhisa Hirayama Shozo Fukui 《应用有机金属化学》1989,3(3):273-277
The acute toxicity of methylarsonic acid, CH3AsO(OH)2 (MAA), dimethylarsininc acid, (CH3)2AsO(OH) (DMAA), and trimethylarsine oxide, (CH3)3AsO (TMAO), were examined in mice with oral administration. The LD50 values of MAA, DMAA and TMAO were 1.8, 1.2 and 10.6 g kg?1 respectively. The toxicity of MAA and DMAA was very much lower than that for inorganic arsenic compounds. It was shown that TMAO has a similar acute toxicity to arsenobetaine. On the other hand, when the mice were administered 14.4 g kg?1 of TMAO once only orally, a garlic-like odor (trimethylarsine, (CH3)3As) was definitely detectable in the exhalation of the animals by the human olfactory sense within about a few minutes. 相似文献