全文获取类型
收费全文 | 1299篇 |
免费 | 87篇 |
国内免费 | 11篇 |
专业分类
化学 | 964篇 |
晶体学 | 5篇 |
力学 | 30篇 |
综合类 | 1篇 |
数学 | 194篇 |
物理学 | 203篇 |
出版年
2023年 | 15篇 |
2022年 | 17篇 |
2021年 | 42篇 |
2020年 | 59篇 |
2019年 | 49篇 |
2018年 | 30篇 |
2017年 | 33篇 |
2016年 | 64篇 |
2015年 | 61篇 |
2014年 | 48篇 |
2013年 | 89篇 |
2012年 | 69篇 |
2011年 | 99篇 |
2010年 | 38篇 |
2009年 | 38篇 |
2008年 | 64篇 |
2007年 | 54篇 |
2006年 | 56篇 |
2005年 | 47篇 |
2004年 | 56篇 |
2003年 | 33篇 |
2002年 | 29篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1998年 | 16篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1975年 | 8篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1971年 | 6篇 |
排序方式: 共有1397条查询结果,搜索用时 15 毫秒
971.
Katrin Paschke Gunnar Blume Nils Werner André Müller Bernd Sumpf Johannes Pohl David Feise Peter Ressel Alexander Sahm Roland Bege Julian Hofmann Daniel Jedrzejczyk Günther Tränkle 《Optical Review》2018,25(1):149-159
Watt-class visible laser light with a high luminance can be created with high-power GaAs-based lasers either directly in the red spectral region or using single-pass second harmonic generation (SHG) for the colors in the blue–yellow spectral region. The concepts and results of red- and near infrared-emitting distributed Bragg reflector tapered lasers and master oscillator power amplifier systems as well as their application for SHG bench-top experiments and miniaturized modules are presented. Examples of these high-luminance light sources aiming at different applications such as flying spot display or holographic 3D cinema are discussed in more detail. The semiconductor material allows an easy adaptation of the wavelength allowing techniques such as six-primary color 3D projection or color space enhancement by adding a fourth yellow color. 相似文献
972.
Jonas Lampart Julian Schmidt Stefan Teufel Roderich Tumulka 《Mathematical Physics, Analysis and Geometry》2018,21(2):12
We consider a way of defining quantum Hamiltonians involving particle creation and annihilation based on an interior-boundary condition (IBC) on the wave function, where the wave function is the particle-position representation of a vector in Fock space, and the IBC relates (essentially) the values of the wave function at any two configurations that differ only by the creation of a particle. Here we prove, for a model of particle creation at one or more point sources using the Laplace operator as the free Hamiltonian, that a Hamiltonian can indeed be rigorously defined in this way without the need for any ultraviolet regularization, and that it is self-adjoint. We prove further that introducing an ultraviolet cut-off (thus smearing out particles over a positive radius) and applying a certain known renormalization procedure (taking the limit of removing the cut-off while subtracting a constant that tends to infinity) yields, up to addition of a finite constant, the Hamiltonian defined by the IBC. 相似文献
973.
Julian Scheuer 《Archiv der Mathematik》2018,110(6):591-604
To a real n-dimensional vector space V and a smooth, symmetric function f defined on the n-dimensional Euclidean space we assign an associated operator function F defined on linear transformations of V. F shall have the property that, for each inner product g on V, its restriction \(F_{g}\) to the subspace of g-selfadjoint operators is the isotropic function associated to f. This means that it acts on these operators via f acting on their eigenvalues. We generalize some well-known relations between the derivatives of f and each \(F_{g}\) to relations between f and F, while also providing new elementary proofs of the known results. By means of an example we show that well-known regularity properties of \(F_{g}\) do not carry over to F. 相似文献
974.
Julian Brough 《代数通讯》2018,46(2):829-833
Let G be a finite group and k an algebraically closed field of characteristic p. In this paper we investigate the Loewy structure of centers of indecomposable group algebras kG, for groups G with a normal elementary abelian Sylow p-subgroup. Furthermore, we show a reduction result for the case that a normal abelian Sylow p-subgroup is acted upon by a subgroup of its automorphism group; this is fundamental in providing generic formulae for the Loewy lengths considered. 相似文献
975.
We present theoretical calculations, based on a random phasor sum model, which show that the optical coherence tomography speckle contrast ratio is dependent on the local density of scattering particles in a sample, provided that the effective number of scatterers in the probed volume is less than about five. We confirm these theoretical predictions experimentally, using suspensions of microspheres in water. The observed contrast ratios vary in value from the Rayleigh limit of 0.52 to in excess of 2, suggesting that the contrast ratio could be useful in optical coherence tomography, particularly when imaging in ultrahigh-resolution regimes. 相似文献
976.
Nikola Markovi Felipe Conzuelo Julian Szczesny María Begoa GonzlezGarcía David HernndezSantos Adrian Ruff Wolfgang Schuhmann 《Electroanalysis》2019,31(2):217-221
We report a prototype air‐breathing carbon cloth‐based electrode that was fabricated starting from a commercially available screen‐printed electrode equipped with a transparent ITO working electrode (DropSens, ref. ITO10). The fabrication of the air‐breathing electrodes is straightforward, shows satisfactory reproducibility and a good electrochemical response as evaluated by means of [Fe(CN)6]3?/4? voltammetry. The gas‐diffusion electrodes were successfully modified with the O2 reducing enzyme bilirubin oxidase from Myrothecium verrucaria in a direct electron transfer regime. The enzyme modified electrodes showed a remarkable high current density for O2 reduction in passive air‐breathing mode of up to 5 mA cm?2. Moreover, the enzyme modified electrodes were applied as O2 reducing biocathodes in a glucose/air enzymatic biofuel cell in combination with a high current density glucose oxidase/redox polymer bioanode. The biofuel cell provides a high maximum power density of (0.34±0.02) mW cm?2 at 0.25 V. The straightforward design, low cost and the high reproducibility of these electrodes are considered as basis for standardized measurements under gas‐breathing conditions and for high throughput screening of gas converting (bio‐)catalysts. 相似文献
977.
Forsythe D Julian SR Bergemann C Pugh E Steiner MJ Alireza PL McMullan GJ Nakamura F Haselwimmer RK Walker IR Saxena SS Lonzarich GG Mackenzie AP Mao ZQ Maeno Y 《Physical review letters》2002,89(16):166402
We have measured the temperature and field dependence of the resistivity of the unconventional superconductor Sr2RuO4 at pressures up to 3.3 GPa. Using the Shubnikov-de Haas effect, we find that the Fermi surface sheet believed to be primarily responsible for superconductivity becomes more two-dimensional with increasing pressure, a surprising result that is, however, consistent with a recent model of orbital-dependent superconductivity in this system. Many-body enhancements and the superconducting transition temperature all fall gradually with increasing pressure, contrary to previous suggestions of a ferromagnetic quantum critical point at approximately 3 GPa. 相似文献
978.
Julian I. Palmore 《Letters in Mathematical Physics》1975,1(1):71-73
We announce several theorems on the evolution of relative equilibria classes in the planar n-body problem. In an earlier paper [1] we announced a partial classification of relative equilibria of four equal masses. In [2] we described these new relative equilibria classes and showed the way in which a degeneracy arose in the four body problem. These results point the way toward classifying relative equilibria for any n > 4.Research supported in part by NSF grant MPS-73-03735 A04. 相似文献
979.
Extensive Monte Carlo folding simulations for four proteins of various structural classes are carried out, using a single continuous potential (united-residue force field). In all cases, collapse occurs at a very early stage, and proteins fold into their nativelike conformations at appropriate temperatures. We also observe that glassy transitions occur at low temperatures. The simulation results demonstrate that the folding mechanism is controlled not only by thermodynamic factors but also by kinetic factors: The way a protein folds into its native structure is also determined by the convergence point of early folding trajectories, which cannot be obtained by the free energy surface. 相似文献
980.
We derive sharp injectivity criteria for mappings in terms of Ahlfors' definition of the Schwarzian derivative for such mappings.