全文获取类型
收费全文 | 15226篇 |
免费 | 3100篇 |
国内免费 | 2334篇 |
专业分类
化学 | 7942篇 |
晶体学 | 187篇 |
力学 | 1552篇 |
综合类 | 152篇 |
数学 | 1098篇 |
物理学 | 9729篇 |
出版年
2024年 | 38篇 |
2023年 | 160篇 |
2022年 | 556篇 |
2021年 | 531篇 |
2020年 | 591篇 |
2019年 | 505篇 |
2018年 | 497篇 |
2017年 | 632篇 |
2016年 | 715篇 |
2015年 | 572篇 |
2014年 | 861篇 |
2013年 | 1324篇 |
2012年 | 970篇 |
2011年 | 1057篇 |
2010年 | 896篇 |
2009年 | 1000篇 |
2008年 | 1043篇 |
2007年 | 944篇 |
2006年 | 991篇 |
2005年 | 773篇 |
2004年 | 764篇 |
2003年 | 652篇 |
2002年 | 566篇 |
2001年 | 534篇 |
2000年 | 485篇 |
1999年 | 348篇 |
1998年 | 394篇 |
1997年 | 316篇 |
1996年 | 296篇 |
1995年 | 241篇 |
1994年 | 223篇 |
1993年 | 194篇 |
1992年 | 181篇 |
1991年 | 130篇 |
1990年 | 112篇 |
1989年 | 95篇 |
1988年 | 106篇 |
1987年 | 72篇 |
1986年 | 50篇 |
1985年 | 39篇 |
1984年 | 48篇 |
1983年 | 17篇 |
1982年 | 33篇 |
1981年 | 21篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 18篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Yasumitsu Matsuo Takehiko Ijichi Hironori Yamada Junko Hatori Seiichiro Ikehata 《Central European Journal of Physics》2004,2(2):357-366
We have fabricated a field effect transistor (FET) based on an organic ferroelectric insulator and molecular conductor, and
investigated the electrical properties and memory effects on the PEN-FET. We have observed a drastic change in the drain current
at around the coercive electric fieldE
c
of the organic ferroelectric insulator in not only a FET (PEN-FET) based on a pentacene (PEN) film but also a FET (IPEN-FET)
based on an iodine doped PEN film. The magnitude of the change of the drain current for the IPEN-FET is 200 times larger than
that for the PEN-FET. It is expected from these results that the PEN-FET (especially the IPEN-FET) is an improvement in such
devices, since it operates at a low gate electric field accompanied by the appearance of the spontaneous polarization in the
organic ferroelectric insulator. In addition, we have found that the drain current for the PEN-FET does not return to the
initial drain current ofE
G
=0 V/cm for more than one week, even if the gate electric field is changed to 0 V/cm from 500 V/cm(>E
c
). From these results, it is suggested that the PEN-FET becomes a memory device. 相似文献
52.
53.
Nonlinear susceptibility of a quantum dot (QD) embedded in a two-sided cavity, is studied theoretically from a weak-coupling to a strong-coupling regime. In the relevance of a quantum logic gate, the corresponding nonlinear phase shifts (Kerr effect) are estimated for coherent wavepackets including one photon on average. In the weak-coupling regime, the phase shift enhances strongly as a function of a coupling constant between the cavity photon and QD, and eventually saturates in the strong-coupling regime. We also show transmission spectra to evaluate the efficiency of the phase shift. Although the efficiency decreases monotonically in the weak-coupling regime, it rises in the strong-coupling regime. 相似文献
54.
Sylvia Pulmannová 《International Journal of Theoretical Physics》2003,42(5):907-919
Tensor products of quantum logics and effect algebras with some known problems are reviewed. It is noticed that although tensor products of effect algebras having at least one state exist, in the category of complex Hilbert space effect algebras similar problems as with tensor products of projection lattices occur. Nevertheless, if one of the two coupled physical systems is classical, tensor product exists and can be considered as a Boolean power. Some applications of tensor products (in the form of Boolean powers) to quantum measurements are reviewed. 相似文献
55.
56.
57.
考虑到量子相干效应和界面散射效应 ,利用 L ambert理论模型 ,计算正常金属 /绝缘层 /超导 /绝缘层 /正常金属双垒隧道结中的准粒子输运系数和隧道谱。研究表明 :( 1)所有的准粒子输运系数和电导谱在超导能隙之上都随能量作周期性振荡 ,其振荡周期依赖于超导层的厚度 ;( 2 )在超导能隙之上 Andreev反射系数随能量呈现周期性消失现象 ;( 3)在绝缘层势垒强度取很大的隧道极限下 ,超导层中会形成一系列的准粒子束缚态 ,其位置由量子化条件决定 ;( 4)界面散射效应不仅能压低各子能隙电导峰 ,还能使子能隙电导峰劈裂为两个峰。 相似文献
58.
Anna Avallone 《Mathematica Slovaca》2007,57(2):129-140
We prove the existence of separating points for every countable family of nonatomic σ-additive modular measures on a σ-complete lattice ordered effect algebra.
相似文献
59.
S. A. Kirillov A. Morresi M. Paolantoni P. Sassi 《Journal of Physical Organic Chemistry》2007,20(8):568-573
The most obvious consequence of the concept of aromaticity is the common confidence that in aromatic compounds, bond lengths do not alternate and are between typical to the single and double ones. However, in 1994, performing crystal structure investigations of substituted pyridines and their salts, Krygowski and co‐workers have discovered a very surprising angular group induced bond alteration (AGIBA) effect: It appears that some angular substituents, like methoxy or nitrozo groups, can induce bond alternation in aromatic rings. Crystal studies do not allow one to operate with liquids that are more common in organic chemistry. This paper presents the first possible evidence of spectroscopic manifestations of the AGIBA effect. Raman spectra of the liquid toluene are analyzed. It is found that instead of being single, the line corresponding to the ring breathing vibrations is clearly split by 1.0–1.4 cm?1, thus indicating the presence of two (cis‐ and trans‐) AGIBA isomers. The energy difference between these isomers estimated in temperature dependent Raman studies is found equal to 6.68 kJ mol?1. The low‐wavenumber line therefore corresponds to the cis‐AGIBA isomer and the high‐wavenumber line to the trans‐AGIBA isomer stabilized by the AGIBA effect. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
60.