全文获取类型
收费全文 | 2170篇 |
免费 | 82篇 |
国内免费 | 22篇 |
专业分类
化学 | 1398篇 |
晶体学 | 14篇 |
力学 | 78篇 |
数学 | 434篇 |
物理学 | 350篇 |
出版年
2024年 | 2篇 |
2023年 | 20篇 |
2022年 | 45篇 |
2021年 | 45篇 |
2020年 | 54篇 |
2019年 | 58篇 |
2018年 | 57篇 |
2017年 | 40篇 |
2016年 | 77篇 |
2015年 | 78篇 |
2014年 | 94篇 |
2013年 | 145篇 |
2012年 | 172篇 |
2011年 | 237篇 |
2010年 | 114篇 |
2009年 | 102篇 |
2008年 | 153篇 |
2007年 | 127篇 |
2006年 | 131篇 |
2005年 | 104篇 |
2004年 | 91篇 |
2003年 | 76篇 |
2002年 | 53篇 |
2001年 | 27篇 |
2000年 | 18篇 |
1999年 | 10篇 |
1998年 | 13篇 |
1997年 | 14篇 |
1996年 | 16篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1978年 | 7篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1961年 | 3篇 |
1942年 | 6篇 |
1940年 | 3篇 |
1926年 | 1篇 |
排序方式: 共有2274条查询结果,搜索用时 15 毫秒
111.
Karl Joulain Alexandre Loizeau 《Journal of Quantitative Spectroscopy & Radiative Transfer》2007,104(2):208-216
Following Greffet et al. [Coherent emission of light by thermal sources. Nature 2002;416:61-4], we study in this article, the possibility to engineer thermal coherent sources with waveguides. The idea is to rule a grating on a waveguide made of a slice of germanium deposited on a participating media such as glass. The guided waves, thermally excited are coupled to the far field by the grating and increase the system emissivity in certain directions and wavelengths. We numerically compute the diffraction of a plane wave by the grating by a rigorous coupled waves algorithm (RCWA). The reflected, transmitted and absorbed energy calculated allows to obtain the system emissivity by means of the Kirchhoff law. 相似文献
112.
Louis‐Philippe B. Beaulieu Dr. Lucie E. Zimmer Prof. Alexandre Gagnon Prof. André B. Charette 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(46):14784-14791
Herein, we report the enantio‐ and diastereoselective formation of trans‐iodo‐ and trans‐chlorocyclopropanes from α‐iodo‐ and α‐chlorozinc carbenoids by using a dioxaborolane‐derived chiral ligand. The synthetically useful iodocyclopropane building blocks were derivatized by an electrophilic trapping of the corresponding cyclopropyl lithium species or a Negishi coupling to give access to a variety of enantioenriched 1,2,3‐substituted cyclopropanes. The synthetic utility of this method was demonstrated by the formal synthesis of an HIV‐1 protease inhibitor. In addition, the related stereoselective bromocyclopropanation was also investigated. New insights about the relative electrophilicity of haloiodomethylzinc carbenoids are also presented. 相似文献
113.
Preparation of Polyfunctional Arylzinc Organometallics in Toluene by Halogen/Zinc Exchange Reactions
Moritz Balkenhohl Dorothe S. Ziegler Alexandre Desaintjean Leonie J. Bole Alan R. Kennedy Eva Hevia Paul Knochel 《Angewandte Chemie (International ed. in English)》2019,58(37):12898-12902
A wide range of polyfunctional diaryl‐ and diheteroarylzinc species were prepared in toluene within 10 min to 5 h through an I/Zn or Br/Zn exchange reaction using bimetallic reagents of the general formula R′2Zn?2 LiOR (R′=sBu, tBu, pTol). Highly sensitive functional groups, such as a triazine, a ketone, an aldehyde, or a nitro group, were tolerated in these exchange reactions, enabling the synthesis of a plethora of functionalized (hetero)arenes after quenching with various electrophiles. Insight into the constitution and reactivity of these bimetallic mixtures revealed the formation of highly active lithium diorganodialkoxyzincates of type [R′2Zn(OR)2Li2]. 相似文献
114.
Loredo A Plessy A El Hafidi A Hamzaoui N 《The Journal of the Acoustical Society of America》2011,129(4):1905-1918
A numerical vibroacoustic model that can manage multilayered plates locally covered with damping patches is presented. All the layers can have an on-axis orthotropic viscoelastic behavior. Continuity of displacements and transverse shear stresses at each interface is enforced, which permits to write the entire displacement field in function of the displacements of the--common--first layer, leading to a two-dimensional plate model. The problem is then discretized by Rayleigh-Ritz's method using a trigonometric basis that includes both sine and cosine functions in order to treat various boundary conditions. The excitation can be of mechanical kind (concentrated or distributed forces) or of acoustic kind (plane wave of any incidence, diffuse field, etc.). The model permits to compute different vibroacoustic indicators: the mean square velocity of the plate, the radiation efficiency, and the transmission loss. Comparisons between the present model and numerical results from literature or finite element computations show that the model gives good results in both mechanical and acoustical aspects. Then, a comparison of the effects of different distributions of patches is presented. The role of the surface covering rate is first discussed, followed by a study involving different geometries for the same surface covering rate. 相似文献
115.
116.
Zanchet A Halvick P Rayez JC Bussery-Honvault B Honvault P 《The Journal of chemical physics》2007,126(18):184308
First quasiclassical trajectory calculations have been carried out for the C(3P)+OH(X 2Pi)-->CO(X 1Sigma+)+H(2S) reaction using a recent ab initio potential energy surface for the ground electronic state, X 2A', of HCO/COH. Total and state-specific integral cross sections have been determined for a wide range of collision energies (0.001-1 eV). Then, thermal and state-specific rate constants have been calculated in the 1-500 K temperature range. The thermal rate constant varies from 1.78x10(-10) cm3 s-1 at 1 K down to 5.96x10(-11) cm3 s-1 at 500 K with a maximum value of 3.39x10(-10) cm3 s-1 obtained at 7 K. Cross sections and rate constants are found to be almost independent of the rovibrational state of OH. 相似文献
117.
Adenilson J. Chiquito Marcia T. Escote Marcelo O. Orlandi Alexandre J.C. Lanfredi Edson R. Leite Elson Longo 《Physica B: Condensed Matter》2007,400(1-2):243-247
This paper reports on the measurements of transport properties of high crystalline quality Sn doped In2O3 nanobelts. The samples presented metallic conduction in a large range of temperatures; however, at low temperatures, the resistivity showed a slight increase and the current–voltage curves showed a tendency to saturate even in the low-voltage range. From these observations, we discuss some arguments on the possibility of low dimensional conducting channels as the main responsible for the conduction at low temperatures. Additionally, we present an alternative technique for production of low resistance ohmic contacts, which can be further used in devices’ construction. 相似文献
118.
119.
Alexandre Freire Stefan Müller Michael Struwe 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》1998,15(6):725
We show that a weak limit of a sequence of wave maps in (1 + 2) dimensions with uniformly bounded energy is again a wave map. Essential ingredients in the proof are Hodge structures related to harmonic maps,
1 estimates for Jacobians,
1-BMO duality, a “monotonicity” formula in the hyperbolic context and the concentration compactness method. Application of similar ideas in the elliptic context yields a drastically shortened proof of recent results by Bethuel on Palais-Smale sequences for the harmonic map functional on two dimensional domains and on limits of almost H-surfaces. 相似文献
120.
Sarah Sulzer‐Mossé Alexandre Alexakis Prof. Jiri Mareda Dr. Guillaume Bollot Gerald Bernardinelli Dr. Yaroslav Filinchuk Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(13):3204-3220
Chiral framework : Chiral amines with pyrrolidine frameworks catalyze the enantioselective conjugate addition of a wide range of aldehydes to various vinyl sulfones and vinyl phosphonates in high yields and with enantioselectivities up to >99 % ee (see scheme). The high versatility of the Michael adducts is exemplified by various functionalizations with conservation of the optical purity.