全文获取类型
收费全文 | 776篇 |
免费 | 21篇 |
专业分类
化学 | 470篇 |
晶体学 | 7篇 |
力学 | 10篇 |
数学 | 153篇 |
物理学 | 157篇 |
出版年
2022年 | 19篇 |
2021年 | 13篇 |
2020年 | 21篇 |
2019年 | 17篇 |
2018年 | 27篇 |
2017年 | 22篇 |
2016年 | 34篇 |
2015年 | 23篇 |
2014年 | 23篇 |
2013年 | 40篇 |
2012年 | 40篇 |
2011年 | 36篇 |
2010年 | 30篇 |
2009年 | 33篇 |
2008年 | 48篇 |
2007年 | 33篇 |
2006年 | 31篇 |
2005年 | 32篇 |
2004年 | 21篇 |
2003年 | 32篇 |
2002年 | 27篇 |
2001年 | 19篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1976年 | 6篇 |
1975年 | 14篇 |
1974年 | 7篇 |
1973年 | 10篇 |
1972年 | 3篇 |
1971年 | 6篇 |
1970年 | 5篇 |
1968年 | 3篇 |
排序方式: 共有797条查询结果,搜索用时 31 毫秒
71.
72.
We report on the results of mass-spectroscopic analysis of the hydrogen yield from metals saturated with hydrogen under the
action of accelerated electrons (with an energy of up to 100 keV and a current density from 3 to 30 μA). It is found that
the desorption rate is determined not only by parameters of the electron bunch, but also by the structure of the oxide film.
It is discovered that the electronic subsystem of hydrogen-enriched metals enhances their ability to absorb the energy of
the external electromagnetic action and to preserve it for a longer time as compared to a pure metal. This facilitates nonequilibrium
migration and yield of hydrogen under the action of radiation in the subthreshold range. A theoretical model is proposed and
analytic dependences are derived for the intensity of hydrogen yield from metals exposed to an electron bunch. The results
of this study can be used for the removal of hydrogen from metals and for obtaining submicrocrystalline materials (e.g., titanium). 相似文献
73.
We discuss a nonperturbative mechanism for generation of the single-spin asymmetries in hadron interactions. It is based on
the chiral quark model combined with unitarity and impact parameter picture and provides explanation for the experimental
regularities observed under the measurements of the spin asymmetries. 相似文献
74.
A spanning subgraph H of a graph G is a 2-detour subgraph of G if for each x, y ∈ V(G), d
H
(x, y) ≤ d
G
(x, y) + 2. We prove a conjecture of Erdős, Hamburger, Pippert, and Weakley by showing that for some positive constant c and every n, each 2-detour subgraph of the n-dimensional hypercube Q
n
has at least clog2
n · 2
n
edges.
József Balogh: Research supported in part by NSF grants DMS-0302804, DMS-0603769 and DMS-0600303, UIUC Campus Reseach Board
#06139 and #07048, and OTKA 049398.
Alexandr Kostochka: Research supported in part by NSF grants DMS-0400498 and DMS-0650784, and grant 06-01-00694 of the Russian
Foundation for Basic Research. 相似文献
75.
76.
Sergey Miltsov Vladimir Karavan Alexandr Misharev Galina Starova Julian Alonso-Chamarro Mar Puyol 《Tetrahedron letters》2017,58(34):3353-3357
meso-Bromosubstituted indodicarbocyanine dyes produce dimeric molecules, together with the debrominated species, under acid catalysis. The relationship between the dimerization and hydrodebromination routes depends on the aryl substitution of the dyes. A possible reaction mechanism is also proposed. 相似文献
77.
S. Yu. Torilov K. A. Gridnev V. I. Zherebchevsky M. Brenner L. I. Vinogradov V. Z. Goldberg T. V. Korovitskaya T. Lönnroth N. A. Maltsev M. Mutterer B. G. Novatskii M. Norrby J. M. K. Slotte Yu. G. Sobolev W. H. Trzaska G. P. Tyurin S. V. Khlebnikov 《JETP Letters》2011,94(1):6-10
High-spin states of the 22Ne nucleus in the excitation energy range of 15–30 MeV have been studied. The angular correlation method has been used to determine the spins of excited states. A number of new states with high angular momenta—20.0 MeV (9?), 20.7 MeV (11?), 21.6 MeV (9?), 22.2 MeV (12+), and 25.0 MeV (9?)—have been revealed. They are intensely populated in the reaction 14C(12C, α1)22Ne* → α2 + 18O and correspond to the rotational bands of various structures. 相似文献
78.
M. A. Kudryashov A. I. Mashin A. S. Tyurin A. E. Fedosov G. Chidichimo G. De Filpo 《Technical Physics》2011,56(1):92-96
Silver/polyacrylonitrile (Ag/PAN) nanocomposites are synthesized at the stage of simultaneous acrylonitrile polymerization
and the reduction of silver ions from a mixture of silver nitrate AgNO3, acrylonitrile, and a photoinitiator. The synthesized films are transparent in the visible region and are characterized by
a uniform dispersion of silver nanoparticles in a PAN matrix without any macroscopic agglomeration. The effects of the metal
salt and photoinitiator concentrations on the size and density of metal nanoparticles in a composite are revealed. 相似文献
79.
In the (r∣p)-centroid problem, two players, called leader and follower, open facilities to service clients. We assume that clients are identified with their location on the Euclidean plane, and facilities can be opened anywhere in the plane. The leader opens p facilities. Later on, the follower opens r facilities. Each client patronizes the closest facility. In case of ties, the leader’s facility is preferred. The goal is to find p facilities for the leader to maximize his market share. We show that this Stackelberg game is \(\varSigma_{2}^{P}\) -hard. Moreover, we strengthen the previous results for the discrete case and networks. We show that the game is \(\varSigma_{2}^{P}\) -hard even for planar graphs for which the weights of the edges are Euclidean distances between vertices. 相似文献
80.
Stanislav V. Maslennikov Roman A. Ignatyev Alexandr V. Piskounov Irina V. Spirina 《应用有机金属化学》2001,15(3):161-168
Synthesis of magnesium dicyclopentadienide from metal and cyclopentadiene in THF is effectively catalyzed by the derivatives of vanadium and titanium. The kinetics of the synthesis, as well as thermodynamic parameters of reagents adsorption on the magnesium surface, have been determined. The process catalyzed by titanium derivatives is accompanied by the quantitative hydrogenation of cyclopentadiene to cyclopentene whereas the catalysis by vanadium derivatives leads to hydrogen gas evolution. A number of reaction intermediates including Cp2TiCl, Cp2TiH2MgCl, Cp2Ti(cyclo‐C5H7) and Cp2V, were identified by the electron spin resonance method. The equilibrium constants, enthalpies and entropies of adsorption of metal halides on the magnesium surface were calculated. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献