全文获取类型
收费全文 | 724篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
化学 | 508篇 |
晶体学 | 4篇 |
力学 | 28篇 |
数学 | 66篇 |
物理学 | 131篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 14篇 |
2014年 | 12篇 |
2013年 | 45篇 |
2012年 | 44篇 |
2011年 | 63篇 |
2010年 | 38篇 |
2009年 | 25篇 |
2008年 | 47篇 |
2007年 | 45篇 |
2006年 | 32篇 |
2005年 | 33篇 |
2004年 | 38篇 |
2003年 | 31篇 |
2002年 | 27篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 15篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有737条查询结果,搜索用时 15 毫秒
141.
Lorraine M. Deck Quintino Mgani Andrea Martinez Alice Martinic Lisa J. Whalen David L. Vander Jagt Robert E. Royer 《Tetrahedron letters》2012,53(4):373-376
A convenient and efficient synthesis of novel highly substituted dimethoxybenzylnaphthalenes, which are precursors to several dihydroxynaphthoic acids, is described. The approach involves the use of aldol chemistry to provide a number of benzylidene tetralones, which are converted to the target naphthalenes in three steps, with good to excellent yields. Grignard reaction of intermediate benzyl tetralones provided 1-substituted benzyl naphthalenes. The reported synthesis is flexible and scalable and provides access to naphthalenes having a variety of substitution patterns. These benzyl substituted naphthalenes are being converted to naphthoic acids and the bioactivities of these compounds are currently being investigated. 相似文献
142.
Maxwell D. Cummings Tse‐I Lin Lili Hu Abdellah Tahri David McGowan Katie Amssoms Stefaan Last Benoit Devogelaere Marie‐Claude Rouan Leen Vijgen Jan Martin Berke Pascale Dehertogh Els Fransen Erna Cleiren Liesbet vanderHelm Gregory Fanning Kristof VanEmelen Origne Nyanguile Kenny Simmen Pierre Raboisson Sandrine Vendeville 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2012,124(19):4715-4718
143.
We give a combinatorial interpretation of the negative moments of the values at the edge of the critical strip of the L functions of modular forms of GL(2) and GL(3). We deduce some results about the size of these numbers. 相似文献
144.
A. De Giacomo O. De Pascale 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1405-1407
In this work final results on TiO2 film deposition by Plasma Assisted Pulsed Laser Deposition (PAPLD) with an rf biased substrate are presented. In previous work it has been shown that PAPLD is an improvement over conventional PLD for the elimination of particulates in high refractive index thin film deposition. This paper will give a comparison between conventional PLD and PAPLD on the stoichiometry, morphology, and optical properties of deposited TiO2 films. It will be demonstrated that oxygen rf discharge during the PLD process makes incorporation of oxygen into the depositing films extremely effective. This effect of the rf discharge allows operation of the PLD process at a lower oxygen background pressure while enhancing the deposition rate. Also, the production of a good quality TiO2 film by PAPLD using a pure metal titanium target will be shown. PACS 79.20.Ds; 52.80.Pi 相似文献
145.
O. De Pascale C. Esposito M. Lepore P. Boffi M. Gaudio M. Vilnio 《Optics and Lasers in Engineering》1989,10(2)
Plane-polarized CO2 laser beams can be successfully employed in controlled surface temperature laser heat treating in order to improve the coupling between radiation and steel. The coupling efficiency has been quantitatively determined by means of a simple energy balance model, by using a medium-power CO2 laser. In this way, the angle at which the best coupling can be obtained has also been singled out. Moreover, some heat treatments performed with a high power laser beam obliquely impinging on medium carbon steel samples have confirmed that controlled surface temperature laser heat treating can be completely free of the problems concerning the use of coatings generally employed. 相似文献
146.
The diethylaminoethyl ethers of various bis[Bz-hydroxy]bibenzofurans have been synthesized, either from 2-hydroxy-5-methoxybenzyl alcohol, or from benzofurancarboxylic acids. The corresponding ethers of bis[Bz- hydroxy-2-benzofuryl]methanones were prepared from methoxysalicyl-aldehydes. 相似文献
147.
Sylvain Hudlet Sbastien Aubert Aurlien Bruyant Renaud Bachelot Pierre-Michel Adam Jean-Louis Bijeon Gilles Lrondel Pascal Royer Andrei A. Stashkevich 《Optics Communications》2004,230(4-6):245-251
Apertureless scanning near field optical microscopy techniques have become a common way of studying surface samples. By using a nano-probe that scatters the electromagnetic non-propagative waves emerging from a given sample, this microscopy provides optical images with a resolution beyond the diffraction limit. Despite a great diversity of works covering a wide variety of physical domains, the formation of the images obtained is not yet fully understood. The purpose of this letter is to assess the influence of the tip position and imposed oscillation of the tip in apertureless SNOM when a background field is added to the scattered near field. We propose a simple analytical model which enables us to account for the experimental results and explains how, depending on the experimental conditions, the near field signal can totally disappear or, on the contrary, be greatly enhanced. 相似文献
148.
The barriers standing against the formation of superheavy elements and their consecutive decay have been determined in the quasimolecular shape path within a Generalized Liquid Drop Model including the proximity effects between nucleons in a neck, the mass and charge asymmetry, a precise nuclear radius and the shell effects given by the Droplet Model. For moderately asymmetric reactions double-hump potential barriers stand and fast fission of compact shapes in the outer well is possible. Very asymmetric reactions lead to one hump barriers which can be passed only with a high energy relatively to the superheavy element energy. Then, only the emission of several neutrons or an particle can allow to reach an eventual ground state. For almost symmetric heavy-ion reactions, there is no more external well and the inner barrier is higher than the outer one. Predictions for partial decay half-lives are given. 相似文献
149.
Let X be a Banach space of differentiable functions and A: XX be a superposition operator. We consider for A the conditions
相似文献
150.
Bachir Douara Yannick J. Esvan Elisabeth Pereira Francis Giraud Yulia L. Volodina Dmitry N. Kaluzhny Alexander A. Shtil Fabrice Anizon Pascale Moreau 《Tetrahedron》2018,74(8):892-901
Pyrazole analogs of the staurosporine aglycon K252c were recently described as potent inhibitors of the three Pim protein kinase isoforms. To evaluate the impact of the introduction of a sugar moiety on the biological activities of this heterocyclic scaffold, four new glucosylated pyrazole analogs of K252c were synthesized. Their biological evaluation demonstrated that most active compounds 11 and 19 substituted by a β-d-glucosyl moiety at N12 or N13 positions exhibited antiproliferative activities toward HCT116 cells. 相似文献
|