全文获取类型
收费全文 | 7796篇 |
免费 | 1382篇 |
国内免费 | 2150篇 |
专业分类
化学 | 6025篇 |
晶体学 | 310篇 |
力学 | 502篇 |
综合类 | 191篇 |
数学 | 890篇 |
物理学 | 3410篇 |
出版年
2024年 | 13篇 |
2023年 | 89篇 |
2022年 | 295篇 |
2021年 | 305篇 |
2020年 | 310篇 |
2019年 | 327篇 |
2018年 | 303篇 |
2017年 | 360篇 |
2016年 | 384篇 |
2015年 | 437篇 |
2014年 | 509篇 |
2013年 | 662篇 |
2012年 | 717篇 |
2011年 | 757篇 |
2010年 | 660篇 |
2009年 | 736篇 |
2008年 | 701篇 |
2007年 | 648篇 |
2006年 | 507篇 |
2005年 | 472篇 |
2004年 | 359篇 |
2003年 | 282篇 |
2002年 | 231篇 |
2001年 | 220篇 |
2000年 | 254篇 |
1999年 | 164篇 |
1998年 | 73篇 |
1997年 | 49篇 |
1996年 | 74篇 |
1995年 | 43篇 |
1994年 | 48篇 |
1993年 | 41篇 |
1992年 | 38篇 |
1991年 | 26篇 |
1990年 | 40篇 |
1989年 | 31篇 |
1988年 | 22篇 |
1987年 | 31篇 |
1986年 | 18篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 15篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1935年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
LI Na ZHAO Degang & YANG Hui State Key Laboratory on Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences Beijing China 《中国科学G辑(英文版)》2004,47(6):694-701
Because of their large band-gap, large high-field electron velocity, large breakdownfield, and large thermal conductivity, GaN and its heterojunction with AlGaN and InGaNhave foreseeable potential in the applications of high-power/temperature electronics, andoptoelectronic devices operative in UV and visible wavelength. Polarization inducedelectric field can reach the magnitude of ~MV/cm[1,2]. For AlGaN/GaN based FETs theconcentration of sheet carrier induced by polarization in the cha… 相似文献
62.
SHI Bingren LI Jiquan DONG Jiaqi 《核工业西南物理研究院年报(英文版)》2004,(1):115-118
The geodesic acoustic mode (GAM), first predicted by Winsor, Johnson and Dawson in an attempt to explain some experimentally observed low frequency oscillations in stellarators, is a special electrostatic fluid mode with low mode number and coupled with the so-called geodesic curvature of a toroidally confined plasma. The recent on this mode are due to the close relevance of the stabi- lization of drift turbulence by both the zonal flow and the GAM. Previously, the GAM was illustrated in very simple geometries, 相似文献
63.
KF-Al2O3催化合成2-甲基-1-苄基苯并咪唑 总被引:1,自引:0,他引:1
苯并咪唑类杂环化合物具有杀菌、消炎、抗癌、抗氧化的活性,广泛用于食品的防虫和防腐,用于动、植物病毒的防治,人体疾病和肿瘤的防治[1-3],本文用KF Al2O3作催化剂,用DMF为溶剂,利用2 甲基苯并咪唑与苄基溴反应合成2 甲基 1 苄基苯并咪唑的新型方法,考察了诸因素对产率的影响,找出了最佳的反应条件。合成路线如下:1 实验部分1 1 仪器与试剂Brurer AM 500超导核磁共振波谱仪(溶剂CDCl3);CarloErbal1106型元素分析仪,NicoletIm pact410型红外光谱仪,KBr压片,HP1100型和Finnigan FTMS 2000型质谱仪(以上均由华东理工大学分析… 相似文献
64.
65.
Taking into account the effects of quantum interference and interface scattering, combining the electron current with hole current contribution to tunnel current,we study the coherent quantum transport in normal-metal/d-wave superconductor/normal-metal (NM/d-wave SC/NM) double tunnel junctions by using extended Blonder-Tinkham-Klapwijk (BTK) approach. It is shown that all quasiparticle transport coefficients and conductance spectrum exhibit oscillating behavior with the energy, in which periodic vanishing of Andreev reflection (AR) above superconducting gap is found.In tunnel limit for the interface scattering strength taken very large, there are a series of bound states of quasiparticles formed in SC. 相似文献
66.
67.
The electronic structure and magnetism of SmCo7-xZrx alloy are investigated using the spin-polarized MS-X. method. The results show that a few of electrons are transferred to the Sm(5d0) orbital due to orbital hybridization between Sm and Co atoms. The exchange interactions between 3d and 5d electrons are more important than the polarization effects of the conductive electrons, thus it is the main reason resulting in the long-range ferromagnetic order in SmCo7-xZrx. The Curie temperature of SmCo7-xZrx is generally lower than that of corresponding pure Co, which may be explained by the weaker average coupling strength between Co lattices due to some negative couplings mainly occurring of 2e site. The calculated results for the Sm5Co32Zr2 cluster may lead to a better understanding of why SmCo7-xZrx is stable phase. Since the spin-up DOS peak of d electrons at EF arises and the bonding of electrons at EF strengthens with increasing Zr concentration, which results in the internal energy of the system decrease, the stable ferromagnetic order forms in SmCo7-xZrx. 相似文献
68.
We propose a heterogeneous agent herding model, in which the agent clusters are in active or inactive states. When agent clusters are in active states, they tend to buy or sell. In active states, an exchange may occur when two heterogeneous agent clusters encounter each other, and they may merge into a bigger one when two homogeneous agent clusters meet. The ratio of successful exchange or merging depends on two parameters: i.e. the reliability κ, reflecting the credible degree in the interacting agent clusters, being the space effect of the market, and the response degree q, reflecting the influence of the former trading to the current action, being the time effect of the market. Our numerical calculation shows that the dynamics of the model exhibits some behaviour very close to real markets when tuning the reliability and the degree of reaction to some specific values. 相似文献
69.
Na SUN 《数学学报(英文版)》2007,23(10):1909-1914
In this paper, we introduce an operator Hμ(z) on L^∞(△) and obtain some of its properties. Some applications of this operator to the extremal problem of quasiconformal mappings are given. In particular, a sufficient condition for a point r in the universal Teichmfiller space T(△) to be a Strebel point is obtained. 相似文献
70.