全文获取类型
收费全文 | 205107篇 |
免费 | 3473篇 |
国内免费 | 447篇 |
专业分类
化学 | 118150篇 |
晶体学 | 2386篇 |
力学 | 7594篇 |
综合类 | 7篇 |
数学 | 23761篇 |
物理学 | 57129篇 |
出版年
2022年 | 1436篇 |
2021年 | 1883篇 |
2020年 | 1998篇 |
2019年 | 2087篇 |
2018年 | 2623篇 |
2017年 | 2470篇 |
2016年 | 4413篇 |
2015年 | 3175篇 |
2014年 | 4060篇 |
2013年 | 9795篇 |
2012年 | 8486篇 |
2011年 | 9941篇 |
2010年 | 6455篇 |
2009年 | 6191篇 |
2008年 | 8850篇 |
2007年 | 8907篇 |
2006年 | 8195篇 |
2005年 | 7514篇 |
2004年 | 6558篇 |
2003年 | 5542篇 |
2002年 | 5395篇 |
2001年 | 5309篇 |
2000年 | 4177篇 |
1999年 | 3227篇 |
1998年 | 2754篇 |
1997年 | 2614篇 |
1996年 | 2579篇 |
1995年 | 2306篇 |
1994年 | 2320篇 |
1993年 | 2173篇 |
1992年 | 2403篇 |
1991年 | 2452篇 |
1990年 | 2229篇 |
1989年 | 2206篇 |
1988年 | 2120篇 |
1987年 | 2004篇 |
1986年 | 1942篇 |
1985年 | 2555篇 |
1984年 | 2671篇 |
1983年 | 2133篇 |
1982年 | 2323篇 |
1981年 | 2219篇 |
1980年 | 2106篇 |
1979年 | 2238篇 |
1978年 | 2395篇 |
1977年 | 2254篇 |
1976年 | 2273篇 |
1975年 | 2179篇 |
1974年 | 2183篇 |
1973年 | 2209篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
F. Ameli M. Bonori F. Massa 《The European Physical Journal C - Particles and Fields》2002,25(1):67-75
We describe the measurement of the deep sea optical background in some sites south of Capo Passero, Sicily. A continuous
flux of about 440 photons cm
-2
s
-1
in the wavelength interval 440-550 nm is estimated due to the decays of the 40K contained in the sea water. Bioluminescence light bursts are also observed and an example of time evolution is reported.
All the measurements were accomplished using a deep sea module also described in this article.
Received: 20 April 2002 / Published online: 26 July 2002 相似文献
102.
On mechanical characteristics of nanocrystals 总被引:2,自引:0,他引:2
The dependence of the elastic moduli of a nanocrystal on its size is investigated theoretically with reference to a two-dimensional single-crystal strip. It is shown that the uncertainty (of a fundamental nature) in the size of a nanocrystal causes the determination of many of its mechanical characteristics to be ambiguous. It is found that the Cauchy-Green relations are modified and the elastic-constant tensor ceases to be symmetric; the size and shape of a nanocrystal render its mechanical properties more anisotropic. For a single-crystal strip, the Poisson ratio decreases and the Young modulus increases with decreasing thickness of the strip; in the case of a very thin crystal film (two atomic layers thick), these elastic moduli can differ from their macroscopic values by a factor of two. The size effects which make the continuum elasticity theory inapplicable to nanocrystals are estimated. The size effects that occur when the molecular dynamics method is applied for modeling macroscopic objects are also discussed. 相似文献
103.
A. G. Artukh G. F. Gridnev M. Gruszecki F. Koscielniak A. G. Semchenkov O. V. Semchenkova Yu. M. Sereda J. Szmider Yu. G. Teterev 《Physics of Atomic Nuclei》2002,65(3):393-399
A systematic investigation of the forward-angle inclusive yields of 2≤Z≤11 isotopes produced in collisions of 18O projectile nuclei with a 9Be target in the Fermi energy region (35A MeV) is performed. The measurements were based on the use of the COMBAS double achromatic kinematical separator in the spectrometry mode at the Flerov Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research, FLNR (JINR, Dubna). The velocity, isotopic, and element distributions are presented. There is no unique mechanism that would explain the total set of results obtained in this experiment. A dominant role of low-energy reaction mechanisms is observed. The intensity of secondary beams of halolike nuclei 11Li, 12Be, and 14Be is determined. 相似文献
104.
105.
Jerónimo Rodríguez 《Comptes Rendus Mathematique》2004,339(6):445-450
In the present Note we introduce an extension of the conservative space–time mesh refinement method presented by Fouquet et al. We also propose a post-treatment of the solution that reduces the spurious phenomena due to the non-conformity between the time meshes. A reinterpretation of the equations in terms of new unknowns leads to a new scheme with second order consistent coupling equations. Numerical experiments in 2D and a plane wave analysis for the 1D model show that the method is second order accurate for an arbitrary refinement. To cite this article: J. Rodríguez, C. R. Acad. Sci. Paris, Ser. I 339 (2004). 相似文献
106.
F. Pijlman 《Few-Body Systems》2005,36(1-4):209-213
Within the theoretical framework which we apply, a suggested origin for single-spin asymmetries is the presence of gauge links in transverse momentum-dependent distribution functions. Recently we found new gauge-link structures in a number of hard processes. These structures need to be considered in the evolution of parton distribution functions and for establishing factorization. 相似文献
107.
J.-C. Thomas L. Achouri J. Äystö R. Béraud B. Blank G. Canchel S. Czajkowski P. Dendooven A. Ensallem J. Giovinazzo N. Guillet J. Honkanen A. Jokinen A. Laird M. Lewitowicz C. Longour F. de Oliveira Santos K. Peräjärvi M. Stanoiu 《The European Physical Journal A - Hadrons and Nuclei》2004,21(3):419-435
108.
Sauer, Shelah, Vapnik and Chervonenkis proved that if a set system on n vertices contains many sets, then the set system has full trace on a large set. Although the restriction on the size of the
groundset cannot be lifted, Frankl and Pach found a trace structure that is guaranteed to occur in uniform set systems even
if we do not bound the size of the groundset. In this note we shall give three sequences of structures such that every set
system consisting of sufficiently many sets contains at least one of these structures with many sets. 相似文献
109.
G. Tóth 《Journal of Radioanalytical and Nuclear Chemistry》1989,137(4):259-264
The distribution of mono- poly- and unlabelled protein molecules in the radiolabelling mixture was calculated from probability point of view as a function of the radioiodine/protein ratio. 相似文献
110.
J. Krause und F. Umland 《Fresenius' Journal of Analytical Chemistry》1989,335(7):791-795
Summary This paper presents some applications of cyclic voltammetry at the interface of two immiscible electrolyte solutions by means of an experimental set-up described in a former publication. When using special sample preparation good results are obtained for the determination of iodide and quinine in pharmaceutical products as well as for the determination of quinine in tonic water and dodecylsulfate in a tooth-salt.
Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet 相似文献
Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet 相似文献