全文获取类型
收费全文 | 739篇 |
免费 | 26篇 |
国内免费 | 1篇 |
专业分类
化学 | 437篇 |
晶体学 | 3篇 |
力学 | 75篇 |
数学 | 58篇 |
物理学 | 193篇 |
出版年
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 28篇 |
2020年 | 22篇 |
2019年 | 18篇 |
2018年 | 23篇 |
2017年 | 19篇 |
2016年 | 42篇 |
2015年 | 30篇 |
2014年 | 28篇 |
2013年 | 43篇 |
2012年 | 49篇 |
2011年 | 48篇 |
2010年 | 46篇 |
2009年 | 45篇 |
2008年 | 41篇 |
2007年 | 32篇 |
2006年 | 27篇 |
2005年 | 31篇 |
2004年 | 36篇 |
2003年 | 21篇 |
2002年 | 25篇 |
2001年 | 10篇 |
2000年 | 10篇 |
1999年 | 12篇 |
1998年 | 11篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1906年 | 1篇 |
排序方式: 共有766条查询结果,搜索用时 15 毫秒
61.
V.P. Gonçalves M.V.T. Machado 《The European Physical Journal C - Particles and Fields》2003,29(1):37-44
The heavy quark production in ultraperipheral heavy ion collisions is investigated, with particular emphasis on the results
from the coherent interactions given by the two-photon process. One addresses the heavy quark total cross sections at photon
level considering the saturation model and the BFKL dynamics in the color dipole picture. The corresponding cross sections
at nuclear level are presented. It is verified that the QCD dynamics implies an enhancement of the cross section in comparison
with previous calculations.
Received: 30 January 2003 / Revised version: 26 March 2003 / Published online: 13 May 2003
RID="a"
ID="a" e-mail: barros@ufpel.tche.br
RID="b"
ID="b" e-mail: magnus@if.ufrgs.br 相似文献
62.
Cecí lia Ferreira Armando Machado 《Proceedings of the American Mathematical Society》2000,128(7):2181-2186
Let denote the set of all -roots of the identity in a Lie group . We show that is always an embedded submanifold of , having the conjugacy classes of its elements as open submanifolds. These conjugacy classes are examples of -symmetric spaces and we show, more generally, that every -symmetric space of a Lie group is a covering manifold of an embedded submanifold of . We compute also the Hessian of the inclusions of and into , relative to the natural connection on the domain and to the symmetric connection on .
63.
This paper addresses the calculation of derivatives of fractional order for non-smooth data. The noise is avoided by adopting an optimization formulation using genetic algorithms (GA). Given the flexibility of the evolutionary schemes, a hierarchical GA composed by a series of two GAs, each one with a distinct fitness function, is established.
相似文献64.
R Bonfiglio RC King TV Olah K Merkle 《Rapid communications in mass spectrometry : RCM》1999,13(12):1175-1185
A post-column infusion system was developed in order to analyze suppression of electrospray ionization (ESI) tandem mass spectrometry response in the presence of endogenous plasma interferences. By enabling direct detection of these interfering components, this experimental system was used to analyze the ability of several common extraction procedures to remove endogenous plasma components that cause changes in the ESI response of model drug substances. Methyl-t-butyl ether (MTBE) liquid-liquid, Oasis and Empore solid-phase, and acetonitrile (ACN) protein precipitation sample preparation methods were tested using the post-column infusion system. In all cases, ACN protein precipitation samples showed the greatest amount of ESI response suppression while liquid-liquid extracts demonstrated the least. In addition, the three test compounds, phenacetin, caffeine, and a representative Merck compound, demonstrated that ESI response suppression is compound dependent. Suppression was greatest with caffeine, the most polar analyte, and the smallest for the Merck compound, the least polar analyte. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
65.
66.
M.V.T. Machado 《The European Physical Journal C - Particles and Fields》2008,54(3):443-449
We present a study of heavy quarkonium production in hard diffractive processes by pomeron exchange for Tevatron and LHC energies.
The numerical results are computed using a recent experimental determination of the diffractive parton density functions in
the pomeron and these are corrected by unitarity corrections through the gap survival probability factor. We give predictions
for single as well as central diffractive ratios. These processes are sensitive to the gluon content of the pomeron at small
Bjorken variable x and may be particularly useful in studying small-xphysics. They may also be a good place to test the different
available mechanisms for quarkonium production at hadron colliders.
PACS 13.60.Hb; 12.38.Bx; 12.40.Nn; 13.85.Ni; 14.40.Gx 相似文献
67.
68.
Fernando Cruz Moraes Sonia Tomie Tanimoto Giancarlo Richard Salazar‐Banda Sergio Antonio Spinola Machado Lucia Helena Mascaro 《Electroanalysis》2009,21(9):1091-1098
The electrochemical detection of the hazardous pollutant 4‐nitrophenol (4‐NP) at low potentials, in order to avoid matrix interferences, is an important research challenge. This study describes the development, electrochemical characterization and utilization of a multiwall carbon nanotube (MWCNT) film electrode for the quantitative determination of 4‐NP in natural water. Electrochemical impedance spectroscopy measurements showed that the modified surface exhibits a decrease of ca. 13 times in the charge transfer resistance when compared with a bare glassy carbon (GC) surface. Voltammetric experiments showed the possibility to oxidize a hydroxylamine layer (produced by the electrochemical reduction of 4‐NP on the GC/MWNCT surface) in a potential region which is approximately 700 mV less positive than that needed to oxidize 4‐NP, thus minimizing the interference of matrix components. The limit of detection for 4‐NP obtained using square‐wave voltammetry (0.12 μmol L?1) was lower than the value advised by EPA. A natural water sample from a dam located in São Carlos (Brazil) was spiked with 4‐NP and analyzed by the standard addition method using the GC/MWCNT electrode, without any further purification step. The recovery procedure yielded a value of 96.5% for such sample, thus confirming the suitability of the developed method to determine 4‐NP in natural water samples. The electrochemical determination was compared with that obtained by HPLC with UV‐vis detection. 相似文献
69.
Samit Mandal J Gerl H Geissel K Hauschild M Hellström Z Janas I Kojouharov Y Kopatch RC Lemmon P Mayet Z Podolyak PH Regan H Schaffner C Schlegel J Simpson HJ Wollersheim 《Pramana》2001,57(1):161-164
Feasibility of gamma-ray spectroscopy at relativistic energies with exotic heavy-ions and new generation of germanium detectors
(segmented Clover) is discussed. An experiment with such detector array and radioactive is discussed. 相似文献
70.