全文获取类型
收费全文 | 2063篇 |
免费 | 88篇 |
国内免费 | 18篇 |
专业分类
化学 | 1409篇 |
晶体学 | 4篇 |
力学 | 69篇 |
数学 | 436篇 |
物理学 | 251篇 |
出版年
2022年 | 11篇 |
2021年 | 15篇 |
2020年 | 19篇 |
2019年 | 34篇 |
2018年 | 27篇 |
2017年 | 20篇 |
2016年 | 48篇 |
2015年 | 56篇 |
2014年 | 46篇 |
2013年 | 143篇 |
2012年 | 119篇 |
2011年 | 119篇 |
2010年 | 92篇 |
2009年 | 75篇 |
2008年 | 120篇 |
2007年 | 125篇 |
2006年 | 109篇 |
2005年 | 99篇 |
2004年 | 116篇 |
2003年 | 95篇 |
2002年 | 97篇 |
2001年 | 43篇 |
2000年 | 36篇 |
1999年 | 26篇 |
1998年 | 27篇 |
1997年 | 22篇 |
1996年 | 42篇 |
1995年 | 21篇 |
1994年 | 24篇 |
1993年 | 13篇 |
1992年 | 23篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 23篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 20篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 17篇 |
1979年 | 15篇 |
1978年 | 16篇 |
1977年 | 16篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1974年 | 14篇 |
1973年 | 17篇 |
排序方式: 共有2169条查询结果,搜索用时 171 毫秒
991.
992.
Julie Schobing Valérie Tschamber Jean-François Brilhac Aglaé Auclaire Yves Hohl 《Comptes Rendus Chimie》2018,21(3-4):221-231
Simultaneous NOx reduction and soot combustion over a commercial vanadia-based selective catalytic reduction (SCR) catalyst were investigated. Carbon black was used as model soot. The impact of the contact intensity between carbon and catalyst was studied. The experiments appeared as promising results for the utilization of vanadia-based SCR catalysts in SCR on filter system as, in the SCR operating temperature range (250–400 °C), no significant impact of the presence of carbon black on NOx reduction was observed. However, a decrease in the specific carbon oxidation rate was highlighted. This latter increases with the contact between carbon and catalyst and is attributed to a lack of NO2, consumed by the fast SCR reaction. At temperatures greater than 400 °C, the contact between carbon particles and the SCR catalyst partially inhibits the NOx reduction, whereas it exhibits a catalytic effect on the carbon oxidation rate. The tighter the contact between the two materials, the more significant is this behavior. A redox mechanism, which competes with the redox cycle of the SCR mechanism, was proposed. The impregnation of a V-based SCR catalyst with 2 wt % of calcium was also performed. A drastic loss of DeNOx activity was observed, whereas the effect of the contact between carbon and catalyst was reduced. 相似文献
993.
Taking Photochromism beyond Visible: Direct One‐Photon NIR Photoswitches Operating in the Biological Window 下载免费PDF全文
Kristin Klaue Yves Garmshausen Prof. Stefan Hecht 《Angewandte Chemie (International ed. in English)》2018,57(5):1414-1417
The success of photopharmacology is inevitably tied to the availability of photoswitches, which can be operated within the biological window (λ=650–1450 nm) to maximize penetration in tissue. A general design strategy has been devised and a dihydropyrene derivative is described here that displays negative T‐type photochromism, allowing for efficient and nearly quantitative (95 %) switching induced by NIR light λ>800 nm. The thermal half‐life of the decolored ring‐open meta‐cyclophanediene isomer ranges from minutes to hours, depending on the solvent polarity and hence serves as a probe of the local environment. Due to the rather subtle geometrical differences between the two isomers, suitably modified NIR photoswitches are potential candidates for switching when bound in the pocket of the biological target, in principle allowing for reversible light‐induced inhibitor deactivation as an alternative approach to externally regulate biological functions. 相似文献
994.
Yves Fé lix Aniceto Murillo 《Proceedings of the American Mathematical Society》1998,126(2):625-627
Let be the group of homotopy classes of self-homotopy equivalences of such that . We prove that is a nilpotent group and that .
995.
Tuning the mesh of a mixed method for the stream function Vorticity formulation of the Navier-Stokes equations 总被引:3,自引:0,他引:3
Summary In this article we study a new mixed method for the Stokes and Navier-Stokes equations. The method uses two meshes, one very fine for and a coarser one for . Error estimates show that boundary layers do not require to refine the mesh for the stream function as much as for the vorticity when the Reynolds number is large. We prove estimates and study implementation problems. 相似文献
996.
Sans résumé
Travail réalisé dans le cadre du groupe Fibres vectoriels du réseau Europrog 相似文献
997.
Yves Deniel 《Journal of Theoretical Probability》1989,2(4):475-485
We give a new direct proof of the a.s. convergence of the Cesàro- means of a stationary process (X
n) when 0<<1 andE(X
n
p
)<+ with p>1 and we show that this result does not hold in general for p=1. We also consider similar questions for orthogonal random variables. Finally, we study the a.s. convergence of Riesz harmonic means. 相似文献
998.
The Correct Use of "Average" Fluorescence Parameters 总被引:1,自引:0,他引:1
When more than one fluorophore is present or when one fluorophore displays a multiple exponential decay "average" fluorescence parameters are derived, which can be combined with "average" lifetimes for further interpretation. However, two kinds of average lifetimes are used in this context: the intensity and the amplitude average lifetime. In this paper the different average parameters are carefully analyzed and their "best" combinations are derived. These average parameters are analyzed in the context of external and internal dynamic and static quenching, Föster energy transfer and the calculation of the radiative rate constant. The use of the amplitude average lifetime for the analysis of multiple fluorophore-containing systems and the detection of interactions is discussed. 相似文献
999.
Carine Duhayon Yves Canac Laurent Dubrulle Carine Maaliki Remi Chauvin 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(3):198-202
Electrostatic interactions between localized integral charges make the stability and structure of highly charged small and rigid organics intriguing. Can σ/π‐electron delocalization compensate reduced conformational freedom by lowering the repulsion between identical charges? The crystal structure of the title salt, C14H16N42+·2CF3SO3−, (2), is described and compared with that of the 2,2′′‐bis(diphenylphosphanyl) derivative, (4). The conformations of the dications and their interactions with neighbouring trifluoromethanesulfonate anions are first analyzed from the standpoint of formal electrostatic effects. Neither cation exhibits any geometrical strain induced by the intrinsic repulsion between the positive charges. In contrast, the relative orientation of the imidazolium rings [i.e. anti for (2) and syn for (4)] is controlled by different configurations of the interactions with the closest trifluoromethanesulfonate anions. The long‐range arrangement is also found to be specific: beyond the formal electrostatic packing, C—H…O and C—H…F contacts have no definite `hydrogen‐bond' character but allow the delineation of layers, which are either pleated or flat in the packing of (2) or (4), respectively. 相似文献
1000.
Robin Frédérique Sericola Bruno Anceaume Emmanuelle Mocquard Yves 《Methodology and Computing in Applied Probability》2022,24(3):2195-2211
Methodology and Computing in Applied Probability - We propose and analyze a new asynchronous rumor spreading protocol to deliver a rumor to all the nodes of a large-scale distributed network. This... 相似文献