全文获取类型
收费全文 | 28646篇 |
免费 | 1752篇 |
国内免费 | 4287篇 |
专业分类
化学 | 26920篇 |
晶体学 | 567篇 |
力学 | 233篇 |
综合类 | 156篇 |
数学 | 1534篇 |
物理学 | 5275篇 |
出版年
2024年 | 36篇 |
2023年 | 233篇 |
2022年 | 567篇 |
2021年 | 523篇 |
2020年 | 592篇 |
2019年 | 1534篇 |
2018年 | 704篇 |
2017年 | 1519篇 |
2016年 | 945篇 |
2015年 | 861篇 |
2014年 | 1100篇 |
2013年 | 2335篇 |
2012年 | 1681篇 |
2011年 | 1859篇 |
2010年 | 1357篇 |
2009年 | 1666篇 |
2008年 | 1869篇 |
2007年 | 1928篇 |
2006年 | 1784篇 |
2005年 | 1554篇 |
2004年 | 1535篇 |
2003年 | 1259篇 |
2002年 | 1074篇 |
2001年 | 877篇 |
2000年 | 858篇 |
1999年 | 644篇 |
1998年 | 580篇 |
1997年 | 502篇 |
1996年 | 426篇 |
1995年 | 418篇 |
1994年 | 311篇 |
1993年 | 277篇 |
1992年 | 281篇 |
1991年 | 192篇 |
1990年 | 123篇 |
1989年 | 117篇 |
1988年 | 85篇 |
1987年 | 52篇 |
1986年 | 50篇 |
1985年 | 57篇 |
1984年 | 41篇 |
1983年 | 21篇 |
1982年 | 50篇 |
1981年 | 43篇 |
1980年 | 29篇 |
1979年 | 48篇 |
1978年 | 20篇 |
1977年 | 18篇 |
1976年 | 15篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
Potential for micromachined actuation of ultra-wide continuously tunable optoelectronic devices 总被引:1,自引:0,他引:1
H. Hillmer J. Daleiden C. Prott F. Römer S. Irmer V. Rangelov A. Tarraf S. Schüler M. Strassner 《Applied physics. B, Lasers and optics》2002,75(1):3-13
Tailored scaling represents a principle of success that, both in nature and in technology, allows the effectiveness of physical
effects to be enhanced. Mutation and selection in nature are imitated in technology, e.g. by model calculation and design.
Proper scaling of dimensions in natural photonic crystals and our fabricated artificial 1D photonic crystals (DBRs, distributed
Bragg reflectors) enable efficient diffractive interaction in a specific spectral range. For our optical microsystems we illustrate
that tailored miniaturization may also increase the mechanical stability and the effectiveness of spectral tuning by thermal
and electrostatic actuation, since the relative significance of the fundamental physical forces involved considerably changes
with scaling. These basic physical principles are rigorously applied in micromachined 1.55-μm vertical-resonator-based devices.
We modeled, implemented and characterized 1.55-μm micromachined optical filters and vertical-cavity surface-emitting laser
devices capable of wide, monotonic and kink-free tuning by a single control parameter. Tuning is achieved by mechanical actuation
of one or several air-gaps that are part of the vertical resonator including two ultra-highly reflective DBR mirrors of strong
refractive index contrast: (i) Δn=2.17 for InP/air-gap DBRs (3.5 periods) using GaInAs sacrificial layers and (ii) Δn=0.5
for Si3N4/SiO2 DBRs (12 periods) with a polymer sacrificial layer to implement the air-cavity. In semiconductor multiple air-gap filters,
a continuous tuning of >8% of the absolute wavelength is obtained. Varying the reverse voltage (U=0–5 V) between the membranes
(electrostatic actuation), a tuning range of >110 nm was obtained for a large number of devices. The correlation of the wavelength
and the applied voltage is accurately reproducible without any hysteresis. In two filters, tuning of 127 and 130 nm was observed
for about ΔU=7 V. The extremely wide tuning range and the very small voltage required are record values to the best of our
knowledge. For thermally actuated dielectric filters based on polymer sacrificial layers, Δλ/ΔU=-7 nm/V is found.
Received: 10 May 2002 / Published online: 8 August 2002 相似文献
63.
64.
We study the propagation of the light mesons σ,ω,ρ, and a0(980) in dense hadronic matter in an extended derivative scalar coupling model. Within the scheme proposed it is possible
to unambiguously define effective density-dependent couplings at the Lagrangian level. We first apply the model to study asymmetric
nuclear matter with fixed isospin asymmetry, and then we pay particular attention to hypermatter in β-equilibrium. The equation
of state and the potential contribution to the symmetry coefficient arising from the mean-field approximation are investigated.
Received: 16 October 2001 / Accepted: 10 January 2002 相似文献
65.
The implementation of a nonzero-order joint transform correlator using the double port Mach-Zehnder interferometric technique is proposed and demonstrated. This approach provides on-line processing for directly removing the zero-order components of a joint power spectrum in one step and performs the nonzero-order optical correlation. Experimental results are presented and discussed. 相似文献
66.
67.
Yi-Shiue Lin 《Applied Surface Science》2006,252(16):5892-5899
Dissociative adsorption of CCl4 on TiO2 at 35 °C has been studied by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and electron spin resonance. CCl4 decompose to form CO, CO2, and CO3 on the surface, at such a low temperature, in which CO2 formation is not from CO oxidation on TiO2, but CO3 can be produced by CO and CO2 adsorption. The Cl generated from CCl4 decomposition is left on the surface and bonded to titanium ions. Mineralization of CCl4 on TiO2 involves the lattice oxygens. Thermodynamical driving force and possible reaction routes for CO and CO2 formation in the CCl4 decomposition on TiO2 are discussed. 相似文献
68.
Analytic Solution of Charge Density of Single Wall Carbon Nanotube under Conditions of Field Electron Emission
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We derive the analytic solution of induced electrostatic potential along single wall carbon nanotubes. Under the hypothesis of constant density of states in the charge-neutral level, we are able to obtain the linear density of excess charge in an external field parallel to the tube axis. 相似文献
69.
70.
Polyvinyl alcohol (PVA)-based proton conducting polymer electrolytes have been prepared by the solution cast technique. The
conductivity is observed to increase from 10−9 to 10−4 S cm−1 as a result of orthophosphoric acid (H3PO4) addition. The plot of conductivity vs temperature shows that a phase transition occurred at 343 K in the sample PVA-33 wt%
H3PO4. The β-relaxation peak is observed at 313 K. The glass transition temperature of PVA-33 wt% H3PO4 is 343 K. Orthophosphoric acid seems to play a dual role, i.e., as a proton source and as a plasticizer. The ac conductivity
σ
ac = Aω
s was also calculated in the temperature range from 303 to 353 K. The conduction mechanism was inferred by plotting the graph
of s vs T from which the conduction mechanism for sample PVA-17 wt% H3PO4 was inferred to occur by way of the overlapping large polaron tunneling (OLPT) model and the conduction mechanism for the
sample PVA-33 wt% H3PO4 by way of the correlated barrier height (CBH) model. 相似文献