全文获取类型
收费全文 | 7724篇 |
免费 | 193篇 |
国内免费 | 1182篇 |
专业分类
化学 | 4134篇 |
晶体学 | 43篇 |
力学 | 354篇 |
综合类 | 4篇 |
数学 | 231篇 |
物理学 | 4333篇 |
出版年
2024年 | 11篇 |
2023年 | 114篇 |
2022年 | 141篇 |
2021年 | 137篇 |
2020年 | 152篇 |
2019年 | 139篇 |
2018年 | 120篇 |
2017年 | 198篇 |
2016年 | 234篇 |
2015年 | 214篇 |
2014年 | 335篇 |
2013年 | 367篇 |
2012年 | 310篇 |
2011年 | 621篇 |
2010年 | 525篇 |
2009年 | 661篇 |
2008年 | 519篇 |
2007年 | 757篇 |
2006年 | 677篇 |
2005年 | 380篇 |
2004年 | 393篇 |
2003年 | 367篇 |
2002年 | 216篇 |
2001年 | 221篇 |
2000年 | 162篇 |
1999年 | 173篇 |
1998年 | 151篇 |
1997年 | 133篇 |
1996年 | 144篇 |
1995年 | 92篇 |
1994年 | 74篇 |
1993年 | 58篇 |
1992年 | 51篇 |
1991年 | 42篇 |
1990年 | 39篇 |
1989年 | 21篇 |
1988年 | 26篇 |
1987年 | 15篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1974年 | 3篇 |
1973年 | 6篇 |
1971年 | 3篇 |
排序方式: 共有9099条查询结果,搜索用时 15 毫秒
31.
The impingement and interdiffusion of adsorbed Pb and Bi layers spreading from separated 3D pure bulk sources on Cu(1 0 0) has been studied, at T = 513 K, by in situ scanning Auger microscopy. When the leading edges of the pure Pb and Bi diffusion profiles impinge, they both consist of low-coverage lattice gas surface alloyed phases. In these low-coverage phases, Pb displaces surface alloyed Bi and the point of intersection of the profiles drifts towards the Bi source. These features lead to the conclusion that Pb atoms are more strongly bound at surface alloyed sites in Cu(1 0 0) than Bi atoms. Once the total coverage (Pb + Bi) on the substrate reaches about one monolayer, Pb and Bi are dealloyed from the substrate, and the interdiffusion profiles become essentially symmetric. Pb and Bi mix in all proportions, with an interdiffusion coefficient of ∼10−13 m2/s. This is considerably smaller than the self-diffusion coefficients previously observed for pure Pb and Bi in their respective high-coverage phases, indicating that the mechanism of interdiffusion is different from that of self-diffusion. As interdiffusion proceeds, the point of intersection of the Pb and Bi profiles reverses its drift direction, leading to the conclusion that binding of Bi atoms to the Cu(1 0 0) substrate is stronger than that of Pb atoms in the highest-coverage surface dealloyed layers. 相似文献
32.
Drevensek Olenik I Kocevar K Musevic I Rasing T 《The European physical journal. E, Soft matter》2003,11(2):169-175
Brewster-angle reflection ellipsometry and surface optical
second harmonic generation were used to study the growth of
4'-n-octyl-4-cyanobiphenyl
(8CB) films evaporated in air onto polymeric and quartz glass
substrates. The layer-by-layer growth of the films terminates
after formation of two distinctive interfacial layers. Both of
these two layers are polar and tilted. In the first layer the
molecules lie nearly flat on the surface, while in the second
layer they point on average about 50° toward the surface normal.
The dipole moment of the second layer has a lower magnitude and
an opposite direction with respect to the dipole moment of the
first layer. 相似文献
33.
The growth processes and structures of Fe/Si(1 1 1) ultrathin films grown by solid-phase reactive epitaxy were investigated by coaxial impact-collision ion scattering spectroscopy (CAICISS). It has been revealed that the Fe(1 1 1) thin films with a bcc-type structure were epitaxially grown on a Si(1 1 1) crystal, even at room temperature, and formed a single-domain structure: Fe(1 1 1)∥Si(1 1 1). After annealing at above 600 °C, the Fe(1 1 1) films were transformed into β-FeSi2 via the collapse of the bcc-type structure to an amorphous or polycrystalline structure. On the basis of the thickness dependences of the growth processes, this phenomenon was discussed in terms of the diffusion of Si into Fe thin films. 相似文献
34.
Early stages of rare-earth metal (Yb and Eu) growth on a vicinal, single-domain Si(1 0 0)2 × 1 surface have been studied in the coverage range of 0.1-0.3 monolayer (ML) by low energy electron diffraction, scanning tunneling microscopy, and synchrotron radiation photoemission spectroscopy. We show that Yb induces the 2 × 3 periodicity in the whole range of coverage studied. The 2 × 3 reconstruction coexists with the local 3 × 2/4 × 2 structure at about 0.2 ML of Yb. In contrast, Eu forms the 3 × 2 periodicity at 0.1-0.2 ML, whereas this structure is converted into the 2 × 3 phase at about 0.3 ML. The atomic arrangement and electronic properties of these reconstructions and the adsorbate-mediated modification of surface morphology are investigated. 相似文献
35.
本文应用线弹簧模型法,基于Sih.G.C.含二维裂纹球壳理论建立了含表面裂纹球壳的控制方程,采用数值方法选取位移试函数及合理地处理了对偶奇异积分方程使计算大为简化,通过电算实现了计算求解过程,从而获得了球壳表面裂纹前沿各点的应力强度因子之值。 最后将计算结果与考虑“膨胀效应”后的Ncwoun-Raju 解进行了比较,同时研究了曲率因素对表面裂纹线弹性断裂性态的影响。 相似文献
36.
We have measured the complex film impedance 1/σd (σ conductivity, d film thickness) of three YBaCuO thin films with d = 44, 115, and 168 nm on MgO substrates at 10.2 GHz in the temperature range between 300 and 4 K. Below Tc, the experimental results are discussed in terms of the two-fluid model and the BCS theory. The residual resistance decreases with the film thickness. The thinnest film has a residual surface resistance of 3 · 10?4 Ω. For this film, the complex microwave conductivity is calculated and compared with the models. Apart from the residual resistance, the measured conductivity is in agreement with the peak caused by the energy gap of the BCS theory. All measurements were performed with a cavity perturbation method which we have to our knowledge applied for the first time to superconducting thin films. The method allows to determine the complex impedance of films with arbitrary thickness. In particular, films with thicknesses small compared to the skin depth δ or the London penetration depth λ can be measured. Therefore, we are able to measure the impedance both in the normal and superconducting state. 相似文献
37.
38.
K. Blaum G. Bollen F. Herfurth A. Kellerbauer H.-J. Kluge M. Kuckein E. Sauvan C. Scheidenberger L. Schweikhard 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):245-248
The cyclotron frequencies of singly charged carbon clusters Cn
+ (n ≥ 2) were measured with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The present limit of mass accuracy δm/m = 1.2 . 10-8 and the extent of the mass-dependent systematic shift (δm/m)sys = 1.7(0.6) . 10-10/u
. (m - m
ref) of the setup were investigated for the first time. In addition, absolute mass measurements by use of pure clusters of the
most abundant carbon isotope 12C are now possible at ISOLTRAP.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"Present address: CERN, CH-1211 Geneva 23, Switzerland; e-mail: klaus.blaum@cern.ch 相似文献
39.
40.
Microstructures of nickel surfaces electrodeposited on indium tin oxides coated glasses are investigated using atomic force microscopy. The fractal dimension D and Hurst exponent H of the nickel surface images are determined from a frequency analysis method proposed by Aguilar et al. [J. Microsc. 172 (1993) 233] and from Hurst rescaled range analysis. The two methods are found to give the same value of the fractal dimension D∼2.0. The roughness exponent α and growth exponent β that characterize scaling behaviors of the surface growth in electrodeposition are calculated using the height-difference correlation function and interface width in Fourier space. The exponents of α∼1.0 and β∼0.8 show that the surface growth does not belong to the universality classes theoretically predicted by statistical growth models. 相似文献