全文获取类型
收费全文 | 3575篇 |
免费 | 548篇 |
国内免费 | 361篇 |
专业分类
化学 | 1347篇 |
晶体学 | 40篇 |
力学 | 627篇 |
综合类 | 50篇 |
数学 | 1165篇 |
物理学 | 1255篇 |
出版年
2024年 | 7篇 |
2023年 | 18篇 |
2022年 | 44篇 |
2021年 | 57篇 |
2020年 | 98篇 |
2019年 | 142篇 |
2018年 | 125篇 |
2017年 | 179篇 |
2016年 | 172篇 |
2015年 | 222篇 |
2014年 | 193篇 |
2013年 | 262篇 |
2012年 | 193篇 |
2011年 | 208篇 |
2010年 | 146篇 |
2009年 | 160篇 |
2008年 | 178篇 |
2007年 | 177篇 |
2006年 | 171篇 |
2005年 | 190篇 |
2004年 | 138篇 |
2003年 | 187篇 |
2002年 | 192篇 |
2001年 | 163篇 |
2000年 | 150篇 |
1999年 | 148篇 |
1998年 | 117篇 |
1997年 | 91篇 |
1996年 | 82篇 |
1995年 | 49篇 |
1994年 | 33篇 |
1993年 | 22篇 |
1992年 | 32篇 |
1991年 | 21篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有4484条查询结果,搜索用时 15 毫秒
11.
We study the two-dimensional first passage problem in which bonds have zero and unit passage times with probabilityp and 1–p, respectively. We prove that as the zero-time bonds approach the percolation thresholdp
c, the first passage time exhibits the same critical behavior as the correlation function of the underlying percolation problem. In particular, if the correlation length obeys(p) ¦p–p
c¦–v, then the first passage time constant satisfies(p)¦p–p
c¦v. At pc, where it has been asserted that the first passage time from 0 tox scales as ¦x¦ to a power with 0<<1, we show that the passage times grow like log ¦x¦, i.e., the fluid spreads exponentially rapidly. 相似文献
12.
用铥空心阴极灯,采用光电流光谱技术测得铥原子21条一级跃迁谱线,确定了相应跃迁上能级的超精细结构常数,其中7个能级的参数为首次发表,运用同一空心阴极灯,采用双色双光子级联共振技术,由荧光法首次测得4个第二激发能级的超精细结构常数. 相似文献
13.
14.
近底水充中推移质的输称属于固液二相流问题,本文针对固相推移质具有的随机和力学双重特性,通过类似分子运动论中Boltzmann方程的推导方法,建立起推移质运动的控制微分方程,其中碰撞项主要考虑推移层颗粒与床面层颗粒的碰撞效应,据此获得推移质输移问题的固液二相流模型--动力学模型,将推移质通量与所受外力联系起来,便于揭示推移质运动的力学本质,开辟推移质理论研究的新途径。 相似文献
15.
实用的三维真彩色模压全息 总被引:2,自引:0,他引:2
三维真彩色模压全息图从艺术角度、信息量、技术含量和防伪功能均优于平面假彩色和平面真彩色模压全息图。本文分析了拍摄三维真彩色彩虹全息图的原理,给出了本方法实现实用三维真彩色模压全息的特点。 相似文献
16.
In a spin‐polarized electron gas, Coulomb interaction couples the spin and motion degrees of freedom to build propagating spin waves. The spin wave stiffness Ssw quantifies the energy cost to trigger such excitation by perturbing the kinetic energy of the electron gas (i.e. putting it in motion). Here we introduce the concept of spin–orbit stiffness, Sso, as the energy necessary to excite a spin wave with a spin polarization induced by spin–orbit coupling. This quantity governs the Coulombic enhancement of the spin–orbit field acting of the spin wave. First‐principles calculations and electronic Raman scattering experiments carried out on a model spin‐polarized electron gas, embedded in a CdMnTe quantum well, demonstrate that Sso = Ssw. Through optical gating of the structure, we demonstrate the reproducible tuning of Sso by a factor of 3, highlighting the great potential of spin–orbit control of spin waves in view of spintronics applications. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
17.
On the Positivity of the Coefficients of a Certain Polynomial Defined by Two Positive Definite Matrices 总被引:1,自引:0,他引:1
It is shown that the polynomialp(t) = Tr[(A+tB)m]has positive coefficients when m = 6 and A and B are any two 3-by-3 complex Hermitian positive definite matrices. This case is the first that is not covered by prior, general results. This problem arises from a conjecture raised by Bessis, Moussa, and Villani in connection with a long-standing problem in theoretical physics. The full conjecture, as shown recently by Lieb and Seiringer, is equivalent to p(t) having positive coefficients for any m and any two n-by-n positive definite matrices. We show that, generally, the question in the real case reduces to that of singular A and B, and this is a key part of our proof. 相似文献
18.
Controllable growth and characterizations of hybrid spiral-like atomically thin molybdenum disulfide
Monolayer MoS2 is an emerging two-dimensional semiconductor with wide-ranging potential applications in novel electronic and optoelectronic devices. Here, we reported controlled vapor phase growth of hybrid spiral-like MoS2 crystals investigated by multiple means of X-Ray photoemission spectroscopy, scanning electron microscopy, atomic force microscopy, kelvin probe force microscopy, Raman and Photoluminescence techniques. Morphological characterizations reveal an intriguing hybrid spiral-like MoS2 feature whose lower planes are AB Bernal stacking and upper structure is spiral. We ascribe the hybrid spiral-like structure to a screw dislocation drive growth mechanism owing to lower supersaturation and layer-by-layer growth mode. In addition, the electrostatic properties of MoS2 microflakes with hybrid spiral structures are obvious inhomogeneous and dependent on morphology manifested by kelvin probe force microscopy. Our work deepens the understanding of growth mechanisms of CVD-grown MoS2, which is also adoptable to other TMDC materials. 相似文献
19.
由D3群一维表示,得到了正三角形上满足Dirichlet边界条件拉普拉斯算子的本征值和本征函数,并讨论了本征函数的对称性. 相似文献
20.
G. Plechinger F.‐X. Schrettenbrunner J. Eroms D. Weiss C. Schüller T. Korn 《固体物理学:研究快报》2012,6(3):126-128
We present a photoluminescence study of single‐layer MoS2 flakes on SiO2 surfaces. We demonstrate that the luminescence peak position of flakes prepared from natural MoS2, which varies by up to 25 meV between individual flakes, can be homogenized by annealing in vacuum. We use HfO2 and Al2O3 layers prepared by atomic layer deposition to cover some of our flakes. In these flakes, we observe a suppression of the low‐energy luminescence peak which appears in asprepared flakes at low temperatures. We infer that this peak originates from excitons bound to surface adsorbates. We also observe different temperature‐induced shifts of the luminescence peaks for the oxide‐covered flakes. This effect stems from the different thermal expansion coefficients of the oxide layers and the MoS2 flakes. It indicates that the single‐layer MoS2 flakes strongly adhere to the oxide layers and are therefore strained. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献