全文获取类型
收费全文 | 1546篇 |
免费 | 61篇 |
国内免费 | 2篇 |
专业分类
化学 | 947篇 |
晶体学 | 3篇 |
力学 | 71篇 |
数学 | 293篇 |
物理学 | 295篇 |
出版年
2024年 | 4篇 |
2023年 | 10篇 |
2022年 | 35篇 |
2021年 | 53篇 |
2020年 | 42篇 |
2019年 | 31篇 |
2018年 | 35篇 |
2017年 | 27篇 |
2016年 | 90篇 |
2015年 | 45篇 |
2014年 | 53篇 |
2013年 | 86篇 |
2012年 | 100篇 |
2011年 | 131篇 |
2010年 | 66篇 |
2009年 | 50篇 |
2008年 | 68篇 |
2007年 | 76篇 |
2006年 | 80篇 |
2005年 | 77篇 |
2004年 | 58篇 |
2003年 | 57篇 |
2002年 | 37篇 |
2001年 | 17篇 |
2000年 | 23篇 |
1999年 | 11篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 18篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 15篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1985年 | 5篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1969年 | 4篇 |
1934年 | 4篇 |
1915年 | 5篇 |
1905年 | 3篇 |
1893年 | 3篇 |
1891年 | 3篇 |
1880年 | 3篇 |
排序方式: 共有1609条查询结果,搜索用时 31 毫秒
1.
In this paper, the authors deal with bifunctions defined on complete metric spaces and with values in locally convex spaces ordered by closed convex cones. The aim is to provide a vector version of Ekeland’s theorem related to equilibrium problems. To prove this principle, a weak notion of continuity of a vector-valued function is considered, and some of its properties are presented. Via the vector Ekeland’s principle, existence results for vector equilibria are proved in both compact and noncompact domains. 相似文献
2.
Summary Campaign results of high-repetition ionospheric soundings, performed at the ionospheric station of Rome using a Digisonde
128P, are presented. We introduce an index derived from run rapid ionograms that can be used to detect oscillations of isodensity
surfaces ofF ionospheric region started by morning solar terminator. 相似文献
3.
4.
Giovanni Tartarini Alessandra Lena Davide Passaro Lorenzo Rosa Stefano Selleri Pier Faccin Enrico Maria Fabbri 《Optical and Quantum Electronics》2006,38(9-11):869-876
A comprehensive numerical tool has been developed for the evaluation of the performances of Radio over Fiber (RoF) links intended for wireless signal distribution.At the transmitter end an appropriate set of rate equations allows to model the optical source as a solitary laser or as an appropriately injection locked laser. The optical channel is modeled putting into account the combined effect of fiber dispersion, laser source non ideal performances (e.g. non-linear effects, frequency chirp), and quadratic detection of the receiving photodiode. The simulation model developed can be a useful tool at the design stage allowing a preliminary evaluation of the characteristics of real RoF links. 相似文献
5.
Davide Guzzetti 《纯数学与应用数学通讯》2002,55(10):1280-1363
6.
7.
Andrea Lodi Monica Caselli Alessandro Casnati Fabio Momicchioli Francesco Sansone Davide Vanossi Glauco Ponterini 《Journal of Molecular Structure》2007,846(1-3):49-54
The sulfonated calixarene I8C12 acts as a host for homologous merocyanines Mc1 and Mc2 in organic solvents, exhibiting neither selectivity towards the guest dyes nor solvent dependence of the complexation equilibria. In water, on the contrary, only the lower homologue, Mc1, is solubilized in the presence of the calixarene. A combination of UV–visible and fluorescence spectroscopic and photophysical analysis and MD structural simulation of the calixarene-dye complexes was employed to account for the observations, and suggests that a radical change in the complexation mode occurs upon moving from an organic to an aqueous environment. 相似文献
8.
Franco Piacenti Mario Bianchi Piero Frediani Ugo Matteoli 《Journal of organometallic chemistry》1975,87(3):C54-C55
Both normal and secondary alkylcobalt carbonyls are shown not to undergo isomerization under catalytic “oxo” conditions, and the relevance of this obervation for the mechanism of the “oxo” reaction is discussed. 相似文献
9.
The electron density distribution in the crystal of diborane has been determined using structure factors based on molecular densities. The libration-correction and third-cumulant terms have also been included in the expression for the temperature factor. The equilibrium re values for BH bond lengths obtained by this treatment are about 0.02Åshorter than the spectroscopic ones. A total librational motion of the diborane molecule is determined: the root-mean-square oscillations about inertial axis are 11.0° (8), 9.6° (5) and 7.2° (5), respectively. The dynamic theoretical deformation density shows a three-center BHB bond picture for the bridge structure. 相似文献
10.
Mario Bianchi Ugo Matteoli Piero Frediani Gloria Menchi Franco Piacenti 《Journal of organometallic chemistry》1982,236(3):375-380
Hydrogen transfer from racemic alcohols to prochiral ketones in the presence of H4Ru4(CO)8[(?)-DIOP]2 has been examined. The enantiomer-discrimination is influenced by the structure of the reactants, temperature and the excess of phosphine present. 相似文献