全文获取类型
收费全文 | 1735篇 |
免费 | 147篇 |
国内免费 | 4篇 |
专业分类
化学 | 1268篇 |
晶体学 | 2篇 |
力学 | 54篇 |
数学 | 308篇 |
物理学 | 254篇 |
出版年
2023年 | 35篇 |
2022年 | 24篇 |
2021年 | 52篇 |
2020年 | 110篇 |
2019年 | 78篇 |
2018年 | 48篇 |
2017年 | 42篇 |
2016年 | 122篇 |
2015年 | 94篇 |
2014年 | 94篇 |
2013年 | 97篇 |
2012年 | 130篇 |
2011年 | 134篇 |
2010年 | 80篇 |
2009年 | 63篇 |
2008年 | 85篇 |
2007年 | 73篇 |
2006年 | 50篇 |
2005年 | 53篇 |
2004年 | 34篇 |
2003年 | 38篇 |
2002年 | 45篇 |
2001年 | 17篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 15篇 |
1996年 | 7篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1989年 | 6篇 |
1986年 | 7篇 |
1984年 | 5篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1974年 | 5篇 |
1969年 | 7篇 |
1968年 | 5篇 |
1967年 | 7篇 |
1964年 | 4篇 |
1963年 | 6篇 |
1933年 | 4篇 |
1930年 | 5篇 |
1916年 | 4篇 |
1914年 | 4篇 |
1912年 | 5篇 |
1911年 | 5篇 |
1909年 | 5篇 |
排序方式: 共有1886条查询结果,搜索用时 15 毫秒
991.
Using nonequilibrium dynamical mean-field theory, we compute the time evolution of the current in a Mott insulator after a strong electric field is turned on. We observe the formation of a quasistationary state in which the current is almost time independent although the system is constantly excited. At moderately strong fields this state is stable for quite long times. The stationary current exhibits a threshold behavior as a function of the field, in which the threshold increases with the Coulomb interaction and vanishes as the metal-insulator transition is approached. 相似文献
992.
Tim Plath Philipp Amstutz Jörn Bödewadt Günter Brenner Nagitha Ekanayake Bart Faatz Kirsten Hacker Katja Honkavaara Leslie Lamberto Lazzarino Christoph Lechner Theophilos Maltezopoulos Matthias Scholz Siegfried Schreiber Mathias Vogt Johann Zemella Tim Laarmann 《Journal of synchrotron radiation》2016,23(5):1070-1075
Free‐electron lasers (FELs) generate femtosecond XUV and X‐ray pulses at peak powers in the gigawatt range. The FEL user facility FLASH at DESY (Hamburg, Germany) is driven by a superconducting linear accelerator with up to 8000 pulses per second. Since 2014, two parallel undulator beamlines, FLASH1 and FLASH2, have been in operation. In addition to the main undulator, the FLASH1 beamline is equipped with an undulator section, sFLASH, dedicated to research and development of fully coherent extreme ultraviolet photon pulses using external seed lasers. In this contribution, the first simultaneous lasing of the three FELs at 13.4 nm, 20 nm and 38.8 nm is presented. 相似文献
993.
G. Lengl A. Plettl P. Ziemann J.P. Spatz M. Möller 《Applied Physics A: Materials Science & Processing》2001,72(6):679-685
Diblock-copolymers (PS(1700)-b-P2VP(450) or PS(1350)-b-P2VP(400)) forming spherical micelles, can be loaded with a Au-salt
and deposited on top of various substrates. Such polymer films have been exposed to a pulsed ArF excimer laser in order to
remove the polymer matrix and, in parallel, to chemically reduce the salt into metallic Au nanodots. To analyze this process
in detail, it was subdivided into three steps: (a) laser ablation of thick and thin diblock-copolymer films; (b) laser irradiation
of Au-salt loaded diblock-copolymer films; and (c) laser irradiation of arrays of metallic Au nanodots. In (a) it was found
that a complete removal of the polymer by laser ablation is only possible in air under ambient conditions while identical
laser irradiations under vacuum result in a residual layer of approximately 14 nm. Substep (b) revealed a nucleation process
of the resulting metallic Au within the micellar core leading to clusters of small Au dots. Furthermore, this substep provided
evidence for an asymmetric interplay between the macroscopic temperature of a polymer film during laser treatment and the
energy density per laser pulse. In (c) it could be demonstrated that metallic Au nanodots on mica are stable against laser
irradiation under conditions leading to a polymer removal.
Received: 7 August 2000 / Accepted: 2 November 2000 / Published online: 3 April 2001 相似文献
994.
A series of large-eddy simulations of a turbulent asymptotic suction boundary layer (TASBL) was performed in a periodic domain, on which uniform suction was applied over a flat plate. Three Reynolds numbers (defined as ratio of free-stream and suction velocity) of Re = 333, 400 and 500 and a variety of domain sizes were considered in temporal simulations in order to investigate the turbulence statistics, the importance of the computational domain size, the arising flow structures as well as temporal development length required to achieve the asymptotic state. The effect of these two important parameters was assessed in terms of their influence on integral quantities, mean velocity, Reynolds stresses, higher order statistics, amplitude modulation and spectral maps. While the near-wall region up to the buffer region appears to scale irrespective of Re and domain size, the parameters of the logarithmic law (i.e. von Kármán and additive coefficient) decrease with increasing Re, while the wake strength decreases with increasing spanwise domain size and vanishes entirely once the spanwise domain size exceeds approximately two boundary-layer thicknesses irrespective of Re. The wake strength also reduces with increasing simulation time. The asymptotic state of the TASBL is characterised by surprisingly large friction Reynolds numbers and inherits features of wall turbulence at numerically high Re. Compared to a turbulent boundary layer (TBL) or a channel flow without suction, the components of the Reynolds-stress tensor are overall reduced, but exhibit a logarithmic increase with decreasing suction rates, i.e. increasing Re. At the same time, the anisotropy is increased compared to canonical wall-bounded flows without suction. The reduced amplitudes in turbulence quantities are discussed in light of the amplitude modulation due to the weakened larger outer structures. The inner peak in the spectral maps is shifted to higher wavelength and the strength of the outer peak is much less than for TBLs. An additional spatial simulation was performed, in order to relate the simulation results to wind tunnel experiments, which – in accordance with the results from the temporal simulation – indicate that a truly TASBL is practically impossible to realise in a wind tunnel. Our unique data set agrees qualitatively with existing literature results for both numerical and experimental studies, and at the same time sheds light on the fact why the asymptotic state could not be established in a wind tunnel experiment, viz. because experimental studies resemble our simulation results from too small simulation boxes or insufficient development times. 相似文献
995.
Using nonequilibrium dynamical mean-field theory, we study the isolated Hubbard model in a static electric field in the limit of weak interactions. Linear response behavior is established at long times, but only if the interaction exceeds a critical value, below which the system exhibits an ac-type response with Bloch oscillations. The transition from ac to dc response is defined in terms of the universal long-time behavior of the system, which does not depend on the initial condition. 相似文献
996.
Johannes Frisch Martin Herder Philipp Herrmann Georg Heimel Stefan Hecht Norbert Koch 《Applied Physics A: Materials Science & Processing》2013,113(1):1-4
The change in the valence electronic structure upon switching of two photochromic diarylethene derivatives, i.e. 1,2-bis(2-methyl-5-p-tolylthiophen-3-yl)cyclopent-1-ene (DAE1) and 1,2-bis(5-(4-hexyloxycarbonylphenyl)-2-methylthiophen-3-yl)cyclopent-1-ene (DAE2), was measured by photoelectron spectroscopy. Switching between open and closed forms was followed in situ upon illumination. The increase of the ionization energy from the closed to the open form was 0.85 eV for DAE1 and 0.80 eV for DAE2. For DAE1, the work function also decreased by 0.25 eV upon switching, which is explained by a decrease of the intrinsic molecular dipole moment and a preferential orientation of molecules in thin films. 相似文献
997.
Philipp Schneeweiss Samuel T. Dawkins Rudolf Mitsch Daniel Reitz Eugen Vetsch Arno Rauschenbeutel 《Applied physics. B, Lasers and optics》2013,110(3):279-283
We demonstrate optical transport of cold cesium atoms over millimeter-scale distances along an optical nanofiber. The atoms are trapped in a one-dimensional optical lattice formed by a two-color evanescent field surrounding the nanofiber, far red- and blue-detuned with respect to the atomic transition. The blue-detuned field is a propagating nanofiber-guided mode while the red-detuned field is a standing-wave mode which leads to the periodic axial confinement of the atoms. Here, this standing wave is used for transporting the atoms along the nanofiber by mutually detuning the two counter-propagating fields which form the standing wave. The performance and limitations of the nanofiber-based transport are evaluated and possible applications are discussed. 相似文献
998.
999.
We have developed a coarse-grained interaction potential between icosahedral nanocrystals and united CH x or SH atoms that interact via Lennard–Jones interactions. This interaction potential can be used to efficiently compute thermodynamic and structural properties of alkyl-thiol capping layers adsorbed on gold nanocrystals. 相似文献
1000.
Ana Menéndez-Manjón Andreas Schwenke Timo Steinke Matthias Meyer Ulrich Giese Philipp Wagener Stephan Barcikowski 《Applied Physics A: Materials Science & Processing》2013,110(2):343-350
Polymer matrix nanocomposites filled with metallic and alloy nanoparticles add functionality in various applications such as optical devices and in the energy sector. However, matrix coupling agents or nanoparticle ligands may be unwanted additives, potentially inhibiting the resulting nanocomposite to be processed by injection molding. The generation of stabilizer-free Au, Ag, and AuAg alloy nanoparticle acrylate composites is achieved by picosecond-pulsed laser ablation of the respective metal target in the liquid monomer. Complementary to laser ablation of the solid alloy, we have alloyed nanoparticles by post-irradiation of Au and Ag colloids in the liquid monomer. The optical properties of the colloidal nanoparticles are successfully transferred to the solid poly(methyl methacrylate) matrix and characterized by their plasmon resonance that can be easily tuned between 400 and 600 nm by laser alloying in the liquid monomer. 相似文献