全文获取类型
收费全文 | 31018篇 |
免费 | 5228篇 |
国内免费 | 3707篇 |
专业分类
化学 | 22277篇 |
晶体学 | 388篇 |
力学 | 1994篇 |
综合类 | 193篇 |
数学 | 3243篇 |
物理学 | 11858篇 |
出版年
2024年 | 115篇 |
2023年 | 645篇 |
2022年 | 1137篇 |
2021年 | 1160篇 |
2020年 | 1197篇 |
2019年 | 1222篇 |
2018年 | 1063篇 |
2017年 | 992篇 |
2016年 | 1551篇 |
2015年 | 1454篇 |
2014年 | 1846篇 |
2013年 | 2346篇 |
2012年 | 2841篇 |
2011年 | 2933篇 |
2010年 | 1980篇 |
2009年 | 1905篇 |
2008年 | 2057篇 |
2007年 | 1905篇 |
2006年 | 1619篇 |
2005年 | 1431篇 |
2004年 | 1096篇 |
2003年 | 871篇 |
2002年 | 831篇 |
2001年 | 690篇 |
2000年 | 630篇 |
1999年 | 575篇 |
1998年 | 473篇 |
1997年 | 404篇 |
1996年 | 448篇 |
1995年 | 409篇 |
1994年 | 337篇 |
1993年 | 262篇 |
1992年 | 264篇 |
1991年 | 236篇 |
1990年 | 210篇 |
1989年 | 178篇 |
1988年 | 129篇 |
1987年 | 108篇 |
1986年 | 92篇 |
1985年 | 81篇 |
1984年 | 59篇 |
1983年 | 41篇 |
1982年 | 20篇 |
1981年 | 26篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1957年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
F. Liang Y. H. Yang J. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(3):337-341
We propose an electrical scheme for the generation of a pure spin current without a charge current in a two-terminal device,
which
consists of a scattering region of a two-dimensional electron gas
(2DEG) with Rashba (R) and/or Dresselhaus (S) spin-orbit interaction (SOI)
and two normal leads. The SOI is modulated by a time-dependent gate
voltage to pump a spin current. Based on a tight-binding model and
the Keldysh Green’s function technique, we obtain the analytical
expression of the spin current. It is shown that a pure spin current
can be pumped out, and its magnitude could be modulated by
device parameters such as the oscillating frequency of the SOI, as
well as the SOI strength. Moreover, the spin polarisation direction of
the spin current could also be tuned by the strength ratio between
RSOI and DSOI. Our proposal provides not only a fully electrical means
to generate a pure spin current but also a way to control the spin
polarisation direction of the generated spin current. 相似文献
983.
Dual-channel phase-shifting interferometry for simultaneous phase microscopy is presented. Red and blue light beams are used for microscope illumination. A 45 tilted beamsplitter replicates the object and reference waves in red light together with the object wave in blue light into two parallel beams. The two resulting quadrature phase-shifting interferograms in red light and the object waves in blue light are generated in the two channels. The two interferograms are recorded simultaneously by a color charge-coupled device (CCD) camera, and can be separated via RGB components of the recorded color patterns without crosstalk. As a result, the phase of tested specimen can be retrieved. The feasibility of the proposed method is demonstrated by test performed on a microscopic specimen. 相似文献
984.
一种相对距离导向的相位展开算法 总被引:1,自引:1,他引:1
提出了一种相对距离导向的相位展开算法,根据相邻像素相位数据的特点,在复数平面上定义一个像素间的相对距离,构成相对距离树,用来标识相位展开路径的可靠性,由距离树导向进行相位展开.给出了距离树的物理意义和算法设计,以相位测量轮廓术为例给出了新算法的应用实例.实验结果表明,算法是合理的和有效的.相位展开的路径总是沿着具有最小距离值的路径到较高距离值的路径方向进行,所以在最坏的情况下误差也被限制在局部最小区域. 相似文献
985.
Effect of current density on the microstructure and corrosion behaviour of plasma electrolytic oxidation treated AM50 magnesium alloy 总被引:1,自引:0,他引:1
P. Bala Srinivasan J. Liang C. Blawert M. Störmer W. Dietzel 《Applied Surface Science》2009,255(7):4212-4218
Plasma electrolytic oxidation (PEO) of an AM50 magnesium alloy was accomplished in a silicate-based electrolyte using a DC power source. Coatings were produced at three current densities, i.e. 15 mA cm−2, 75 mA cm−2, and 150 mA cm−2 and were characterised for thickness, roughness, microstructural morphology, phase composition, and corrosion resistance. Even though the 15 min treated coatings produced at higher current density levels were thicker, they showed poor corrosion resistance when compared to that of the coatings obtained at 15 mA cm−2. Short-term treatments (2 min and 5 min) at 150 mA cm−2 yielded coatings of thickness and corrosion resistance comparable to that of the low current density coatings. The superior corrosion resistance of the low thickness coatings is attributed to the better pore morphology and compactness of the layer. 相似文献
986.
We report the fabrication of one-dimensional (1D) Bi nanowires grown on Ag(1 1 1) with average lateral width from 9 to 20 nm by physical vapor deposition in ultra high vacuum conditions. In situ low-temperature scanning tunneling microscopy analyses reveal that the preferred growth of 1D Bi nanostructures is driven by the highly anisotropic bonding in the crystallographic structure of the Bi(1 1 0) plane. The Bi nanowires grow along direction and align with the directions on Ag(1 1 1). The growth of the Bi nanowires proceeds in a bilayer growth mode resulting from the layer pairing in Bi(1 1 0) which saturates the dangling bonds and lowers the total energy. 相似文献
987.
Ruopeng Li Qiang Peng Bing Han Yuanyu Ke Xin Wang Xubing Lu Xueyuan Wu Jiantao Kong Zhifeng Ren Eser Metin Akinoglu Michael Giersig Guofu Zhou Jun‐Ming Liu Krzysztof Kempa Jinwei Gao 《Laser \u0026amp; Photonics Reviews》2016,10(3):465-472
We demonstrate a high optoelectronic performance and application potential of our random network, with subwavelength diameter, ultralong, and high‐quality silver nanowires, stabilized on a substrate with a UV binder. Our networks show very good optoelectronic properties, with the single best figure of merit of ∼1686, and excellent stability under harsh mechanical strain, as well as thermal, and chemical challenge. Our network transparency strongly exceeds the simple shading limit. We show that this transmission enhancement is due to plasmonic refraction, which in an effective medium picture involves localized plasmons, and identify the inhomogeneous broadening as the key factor in promoting this mechanism. Such networks could become a basis for a next generation of ultrahigh‐performance transparent conductors.
988.
QIU Liang WANG An-Min MA Xiao-San 《理论物理通讯》2008,49(2):516-520
We analyze the time evolution of entanglement of two-qutrit system
within the framework of Milburn's model of intrinsic decoherence.
The entanglement evolution relies not only on the parameters of
system, but also on the concrete states either pure or mixed. The
linear entropy used to measure the extent to which the
intrinsic decoherence affects quantum states is evaluated. 相似文献
989.
Inverse scattering method and soliton solutionfamily for the Einstein--Maxwell theory with multiple Abelian gauge fields 下载免费PDF全文
A Hauser-Ernst-type extended hyperbolic complex linear system given in our previous paper [Gao Y J 2004 Chin. Phys. 13 602] is slightly modified and used to develop a new inverse scattering method for the stationary axisymmetric Einstein-Maxwell theory with multiple Abelian gauge fields. The reduction procedures in this inverse scattering method are found to be fairly simple, which makes the inverse scattering method be fine and effective in practical application. As an example, a concrete family of soliton solutions for the considered theory is obtained. 相似文献
990.
现在诱惑态已被证明是一种可以大大提高量子密钥分发安全性能的现实可行的方法.由于考虑到现实应用中激光器在调制过程中的消光比不能做到100%,以及激光器固有的自发辐射因而使得制备真空态并不是一件容易的事情. 因此本文将对理想情况下准单光子光源量子密钥分发系统应用中的诱惑态结论作了补充和扩展,提出了两个弱光强态的诱惑态方案和一个弱光强诱惑态方案.最后,将“双探测器”的理论应用在准单光子源(HSPS)光源系统中,使系统的安全传输距离可达到2215km,比使用普通探测器的系统增加了约50km. 相似文献