全文获取类型
收费全文 | 594篇 |
免费 | 18篇 |
专业分类
化学 | 388篇 |
晶体学 | 19篇 |
力学 | 3篇 |
数学 | 35篇 |
物理学 | 167篇 |
出版年
2023年 | 4篇 |
2022年 | 17篇 |
2021年 | 18篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 17篇 |
2015年 | 13篇 |
2014年 | 20篇 |
2013年 | 12篇 |
2012年 | 27篇 |
2011年 | 51篇 |
2010年 | 23篇 |
2009年 | 19篇 |
2008年 | 31篇 |
2007年 | 32篇 |
2006年 | 23篇 |
2005年 | 24篇 |
2004年 | 18篇 |
2003年 | 16篇 |
2002年 | 16篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1997年 | 5篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1965年 | 2篇 |
1959年 | 2篇 |
1930年 | 2篇 |
1928年 | 2篇 |
1910年 | 2篇 |
1907年 | 2篇 |
排序方式: 共有612条查询结果,搜索用时 15 毫秒
11.
12.
H. Kühne Th. Morgenstern A. Fischer G. Kissinger D. Krüger 《Crystal Research and Technology》1994,29(2):199-206
In multi-wafer deposition of Si/Ge thin films from silane, germane mixtures at low-temperature epitaxy conditions not only the depletion of the silicon source but also of the germanium source along the reactor tube axis has to be counteracted in order to get homogeneous layer thickness as well as composition. Carrier gas throughput must be minimized to have a sufficient effective chemical reaction rate at low temperature. Thus it cannot be used to flatten layer growth along the susceptor. Yet the addition of a chemically reactive gas, as for instance hydrogen chloride, is suitable to ensure a nearly constant content of the layer forming source gases along the reactor tube. On the other hand hydrogen chloride may infiltrate additional contaminants leading for instance to high oxygen concentration in the deposited layer. However, oxygen soluted or precipitated changes particular features of Si/Ge behaviour for instance during the thin film growth, the following technological stress of the wafer, or the running electronic structures of microelectronic devices. 相似文献
13.
M. Sc. Stephanie Kindt Karina Wicht Prof. Dr. Markus R. Heinrich 《Angewandte Chemie (International ed. in English)》2016,55(30):8744-8747
The radical carbohydroxylation of styrenes with aryldiazonium salts has been achieved under mild thermal conditions. A broad range of aryldiazonium salts was tolerated, and the reaction principle based on a radical–polar crossover mechanism could be extended to carboetherification as well as to a two‐step, metal‐free variant of the Meerwein arylation leading to stilbenes. 相似文献
14.
Marczinowski F Wiebe J Tang JM Flatté ME Meier F Morgenstern M Wiesendanger R 《Physical review letters》2007,99(15):157202
We present low-temperature scanning tunneling spectroscopy measurements on Mn acceptors in InAs in comparison with tight-binding calculations. We find a strong (001)-mirror asymmetry of the bound hole wave function close to the (110) surface. In addition, multiple acceptor-related peaks are observed and are attributed to a spin-orbit splitting of the acceptor level. Because of the p-d exchange interaction the local density of states near the acceptors is enhanced in the valence band and suppressed in the conduction band. We also observe signs of anisotropic scattering of the conduction band states by neutral acceptors. 相似文献
15.
Abe K Akagi T Anthony PL Antonov R Arnold RG Averett T Band HR Bauer JM Borel H Bosted PE Breton V Button-Shafer J Chen JP Chupp TE Clendenin J Comptour C Coulter KP Court G Crabb D Daoudi M Day D Dietrich FS Dunne J Dutz H Erbacher R Fellbaum J Feltham A Fonvieille H Frlez E Garvey D Gearhart R Gomez J Grenier P Griffioen KA Hoibraten S Hughes EW Hyde-Wright C Johnson JR Kawall D Klein A Kuhn SE Kuriki M Lindgren R Liu TJ Lombard-Nelsen RM Marroncle J Maruyama T Maruyama XK McCarthy J Meyer W 《Physical review letters》1995,74(3):346-350
16.
C. J. Zwakhals R. Morgenstern A. Niehaus 《Zeitschrift für Physik A Hadrons and Nuclei》1982,307(1):41-49
We present electron energy spectra that arise in Li+ —He collisions in the laboratory collision energy range from 1.4 to 3 keV, and that are observed at 0° and 180° with respect to the Li+ beam. The spectra are composed of a component due to atomic autoionization of doubly excited He in the field of Li+, and a component due to molecular autoionization of the collision system. The variation of the latter component with collision energy and observation angle is analyzed in terms of a newly developed spectral shape function for molecular autoionization that implies a “distribution of travelling velocities” of the collision system during electron emission. From the comparison of calculated and measured spectra it is concluded that the physical interpretation on which the analysis is based is correct. Two parameters of the distribution of travelling velocities are determined. 相似文献
17.
Summary At first, a necessary and sufficient condition for a K?hler-Norden manifold to be holomorphic Einstein is found. Next, it
is shown that the so-called (real) generalized Einstein conditions for K?hler-Norden manifolds are not essential since the
scalarcurvature of such manifolds is constant. In this context, we study generalized holomorphic Einstein conditions. Using
the one-to-one correspondence between K?hler-Norden structures and holomorphic Riemannian metrics, we establish necessary
and sufficient conditions for K?hler-Norden manifolds to satisfy the generalized holomorphic Einstein conditions. And a class
of new examples of such manifolds is presented. Finally, in virtue of the obtained results, we mention that Theorems 1 and
2 of H. Kim and J. Kim [10] are not true in general. 相似文献
18.
We advance a perspective outcome of tempered α-stable processes used in modeling of anomalous diffusion, a physical mechanism underlying the non-Debye relaxations. The tempered processes are characterized by a heavy tail truncation in time and have finite moments, but they also save some useful features of a purely skewed α-stable process. Due to these features, the relaxation phenomena get a transient character being shown in their asymptotic behavior. From the stochastic subordination scenario of the tempered anomalous diffusion we derive relaxation functions with independent low- and high-frequency exponents falling in the range (0, 1]. Those functions can be used to model all types of experimentally observed two-power-law relaxation patterns. 相似文献
19.
Karina Muñoz-Becerra Nery Villegas-Escobar César Zúñiga-Loyola Diego Cortés-Arriagada 《Molecular physics》2019,117(9-12):1451-1458
ABSTRACTAurones are potential candidates to be employed as fluorescent probes or as pharmacophores for biological applications. This work describes a density functional theory (DFT) and time-dependent -DFT study at the PBE0/6-31?+?G(d) level of theory to analyse the structural, electronic and photophysical properties of a series of new proposed 4′-amine-aurone derivatives in its E and Z isomeric conformations. The maximum absorption wavelength of the proposed aurones appears in the range 390???514?nm, while the most allowed emission pathways were computed in the range 493–530?nm. The bathochromic shift of these compounds with respect to the non-substituted aurone is modulated by the acceptor strength of the added 4-substituents, in addition to the ability of the substituents to localise the frontier molecular orbitals over the acceptor benzofuranone moiety without losing the tricyclic planarity, which favours the push–pull nature of these molecules. The influence of the 4-substituent is also evidenced in the Stokes shifts for the whole series; as the electron-withdrawing character of the 4-substituents enhances, higher is the polarisation of the structure resulting in higher Stokes shifts. As a result, -CF3 and -NO2 substituents were responsible of larger Stokes shifts, then compounds containing these substituents are proposed as potential fluorescence probes for useful applications in biological systems. 相似文献
20.