全文获取类型
收费全文 | 3539篇 |
免费 | 106篇 |
国内免费 | 5篇 |
专业分类
化学 | 2541篇 |
晶体学 | 19篇 |
力学 | 37篇 |
数学 | 480篇 |
物理学 | 573篇 |
出版年
2023年 | 35篇 |
2022年 | 28篇 |
2021年 | 46篇 |
2020年 | 98篇 |
2019年 | 88篇 |
2018年 | 37篇 |
2017年 | 29篇 |
2016年 | 64篇 |
2015年 | 51篇 |
2014年 | 64篇 |
2013年 | 110篇 |
2012年 | 140篇 |
2011年 | 150篇 |
2010年 | 83篇 |
2009年 | 84篇 |
2008年 | 130篇 |
2007年 | 123篇 |
2006年 | 126篇 |
2005年 | 101篇 |
2004年 | 84篇 |
2003年 | 76篇 |
2002年 | 74篇 |
2001年 | 40篇 |
2000年 | 40篇 |
1999年 | 40篇 |
1997年 | 30篇 |
1996年 | 36篇 |
1995年 | 33篇 |
1994年 | 43篇 |
1993年 | 32篇 |
1992年 | 31篇 |
1991年 | 37篇 |
1988年 | 29篇 |
1987年 | 28篇 |
1986年 | 27篇 |
1985年 | 39篇 |
1984年 | 43篇 |
1983年 | 41篇 |
1982年 | 51篇 |
1981年 | 35篇 |
1980年 | 39篇 |
1979年 | 65篇 |
1978年 | 63篇 |
1977年 | 49篇 |
1976年 | 51篇 |
1975年 | 44篇 |
1974年 | 41篇 |
1973年 | 30篇 |
1970年 | 36篇 |
1934年 | 26篇 |
排序方式: 共有3650条查询结果,搜索用时 31 毫秒
1.
Pan Huang Dawen Xu Robert M. Reich Felix Kaiser Boping Liu Fritz E. Kühn 《Tetrahedron letters》2019,60(24):1574-1577
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis. 相似文献
2.
A profit-maximizing supply chain network design model with demand choice flexibility 总被引:1,自引:0,他引:1
Zuo-Jun Max Shen 《Operations Research Letters》2006,34(6):673-682
We present a profit-maximizing supply chain design model in which a company has flexibility in determining which customers to serve. The company may lose a customer to competition if the price it charges is too high. We show the problem formulation and solution algorithm, and discuss computational results. 相似文献
3.
In this Note, we give a necessary and sufficient condition for Lagrangians in a symplectic vector bundle to be deformed stably into transversal Lagrangians. In the case of three Lagrangians, we show that the associated Grothendieck group can be identified with a Hermitian K-theory group. To cite this article: M. Karoubi, M.L. Lapa de Souza, C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
4.
Vicenç Branchadell Roser Pleixats Claude Commandeur Max Malacria 《Journal of organometallic chemistry》2003,687(2):337-345
Regioselectivity of the Tsuji-Trost reaction on allyl acetates and carbonates substituted with silyl groups at the olefinic moiety has been analyzed. Silicon atom in the central carbon atom increases the stability of the intermediate π-allylpalladium cation with respect to the isomeric π-allylpalladium cation featuring the silicon in a terminal carbon atom. 相似文献
5.
Eggenhffner R. Masini R. Bellingeri E. Cimberle M. R. Ferdeghini C. Costa G. A. Kaiser E. Signorelli E. 《Il Nuovo Cimento D》1994,16(10):1659-1664
Il Nuovo Cimento D - The formation of Hg-based HTSC materials was investigated through the development of non-conventional techniques. The former was based on a singlestep synthesis at temperatures... 相似文献
6.
7.
Data about the existence of native HO? CH2? CH2? OH (MEG) in natural wines and champagne has led to delicate questions because of legal decisions already made to declare wine or champagne illegal for sale if the MEG concentrations found are above 10 mg/liter. Action has been taken because of the DEG (diethylene glycol) disaster in European wines of 1985…86. An incorrect legal decision was made due to the belief that MEG cannot be produced biochemically by grape vines. A further reason may be lack of correct data on native MEG trace concentrations, as a result of the special behavior of this diol. As first member of a homologous series whose higher members (C4) are normally found in all wines at quite high concentration levels, MEG shows extremely adsorptive behavior. The solution of the chromatographic problems is summarized in this paper. MEG concentrations in Riesling as example are in the range of 2 to 6 mg/liter and can easily be increased by biotechnological steps to a level of around 10 to 60 mg/liter. This is again due to the specific adsorptive behavior of MEG, which can be enriched on filter surfaces and displaced when the wine acidity changes with changing types. In order to control and guarantee the qualitative and quantitative results of MEG analyses we used a combination of Deans heart cutting on-line with Multi-Chromatography. It was easy to produce false data by many otherwise useful single column or two-dimensional separation processes, etc. 相似文献
8.
9.
The 29th PME research forum on theories included only one European perspective on mathematics education. In order to convey trends in theory usage in Europe we compile, survey and analyze a large subset of the research papers from the 4th European Congress on Mathematics Education (CERME4). That is, this paper includes a discussion of trends seen within CERME4 reports1 on theory usage by European researchers inseven of the fourteen working groups and (a) Outlines similarities and differences in theory usage and (b) takes a futuristic stance on ways in which researchers from different traditions could understand each other. Such an enterprise would further Hans-Georg Steiner's vision of bridging theoretical traditions which are independently formulated in different regions of the world. 相似文献
10.
Uwe Bandelow Mindaugas Radziunas Andrei Vladimirov Bernd Hüttl Ronald Kaiser 《Optical and Quantum Electronics》2006,38(4-6):495-512
We study both theoretically and experimentally typical operation regimes of 40 GHz monolithic mode-locked lasers. The underlying
Traveling Wave Equation model reveals quantitative agreement for characteristics of the fundamental mode-locking as pulse
width and repetition frequency tuning, as well as qualitative agreement with the experiments for other dynamic regimes. Especially
the appearance of stable harmonic mode-locking at 80 GHz has been predicted theoretically and confirmed by measurements. Furthermore,
we derive and apply a simplified Delay-Differential-Equation model which guides us to a qualitative analysis of bifurcations
responsible for the appearance and the breakup of different mode-locking regimes. Higher harmonics of mode-locking are predicted
by this model as well. 相似文献