全文获取类型
收费全文 | 3775篇 |
免费 | 71篇 |
国内免费 | 19篇 |
专业分类
化学 | 2583篇 |
晶体学 | 25篇 |
力学 | 66篇 |
数学 | 531篇 |
物理学 | 660篇 |
出版年
2022年 | 44篇 |
2021年 | 54篇 |
2020年 | 34篇 |
2019年 | 49篇 |
2018年 | 30篇 |
2017年 | 31篇 |
2016年 | 82篇 |
2015年 | 84篇 |
2014年 | 92篇 |
2013年 | 128篇 |
2012年 | 161篇 |
2011年 | 168篇 |
2010年 | 105篇 |
2009年 | 93篇 |
2008年 | 133篇 |
2007年 | 184篇 |
2006年 | 132篇 |
2005年 | 137篇 |
2004年 | 145篇 |
2003年 | 106篇 |
2002年 | 110篇 |
2001年 | 48篇 |
2000年 | 56篇 |
1999年 | 46篇 |
1998年 | 31篇 |
1997年 | 34篇 |
1996年 | 42篇 |
1995年 | 37篇 |
1994年 | 34篇 |
1993年 | 28篇 |
1992年 | 36篇 |
1991年 | 22篇 |
1988年 | 26篇 |
1987年 | 29篇 |
1986年 | 27篇 |
1985年 | 34篇 |
1983年 | 23篇 |
1982年 | 30篇 |
1981年 | 38篇 |
1980年 | 28篇 |
1978年 | 25篇 |
1974年 | 20篇 |
1965年 | 41篇 |
1964年 | 91篇 |
1963年 | 126篇 |
1962年 | 160篇 |
1961年 | 142篇 |
1960年 | 145篇 |
1959年 | 25篇 |
1958年 | 45篇 |
排序方式: 共有3865条查询结果,搜索用时 15 毫秒
131.
The preparation of former unknown 2-(2,4,6-triarylphenyl) substituted 1H-benzimidazolium perchlorates 7 and benzothiazolium perchlorates 8 from 2-methyl substituted derivatives 5/6 by a 2,6-[C5+C] ring transformation of 2,4,6-triarylpyrylium and 2,4,6-triarylthiopyrylium salts 1/9 in the presence of an appropriate base ( 7 : sodium ethoxide, 8 : sodium acetate) is reported. Spectroscopic data of the transformation products and their mode of formation via anhydrobases of the salts 5/6 are discussed. 相似文献
132.
133.
134.
Herben Zimmermann 《Nachrichten aus der Chemie》1980,28(11):797-800
135.
The preliminary results of the hydroformylation of 2-phenylsulfonyl substituted norbornene and norbornadiene derivatives catalyzed by the unmodified Rh(CO)2acac system are presented. The reaction, occurring under standard oxo conditions, gives polyfunctionalized exo norbornene- and exo norbornanecarboxaldehydes. The effect of the phenylsulfonyl group has been evaluated: it has been found that the steric properties of the sulfonyl substituent, more than the electronic ones, influence the regioselectivity of the process. 相似文献
136.
Johanne Heitmann Solheim Boris Zimmermann Valeria Tafintseva Simona Dzurendov Volha Shapaval Achim Kohler 《Molecules (Basel, Switzerland)》2022,27(6)
Extended multiplicative signal correction (EMSC) is a widely used preprocessing technique in infrared spectroscopy. EMSC is a model-based method favored for its flexibility and versatility. The model can be extended by adding constituent spectra to explicitly model-known analytes or interferents. This paper addresses the use of constituent spectra and demonstrates common pitfalls. It clarifies the difference between analyte and interferent spectra, and the importance of orthogonality between model spectra. Different normalization approaches are discussed, and the importance of weighting in the EMSC is demonstrated. The paper illustrates how constituent analyte spectra can be estimated, and how they can be used to extract additional information from spectral features. It is shown that the EMSC parameters can be used in both regression tasks and segmentation tasks. 相似文献
137.
The Casimir-Polder-Lifshitz force felt by an atom near the surface of a substrate is calculated out of thermal equilibrium in terms of the dielectric function of the material and of the atomic polarizability. The new force decays like 1/z3 at large distances (i.e., slower than at equilibrium), exhibits a sizable temperature dependence, and is attractive or repulsive depending on whether the temperature of the substrate is higher or smaller than the one of the environment. Our predictions can be relevant for experiments with ultracold atomic gases. Both dielectric and metal substrates are considered. 相似文献
138.
139.
Ben Ali K Lafon O Zimmermann H Guittet E Lesot P 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,187(2):205-215
We describe several homo- and heteronuclear 2D NMR strategies dedicated to the analysis of anisotropic (2)H spectra of a mixture of dideuterated unlike/like stereoisomers with two remote stereogenic centers, using weakly orienting chiral liquid crystals. To this end, we propose various 2D correlation experiments, denoted "D(H)(n)D" or "D(H)(n)C" (with n=1, 2), that involve two heteronuclear polarization transfers of INEPT-type with one or two proton relays. The analytical expressions of correlation signals for four pulse sequences reported here were calculated using the product-operators formalism for spin I=1 and S=1/2. The features and advantages of each scheme are presented and discussed. The efficiency of these 2D sequences is illustrated using various deuterated model molecules, dissolved in organic solutions of polypeptides made of poly-gamma-benzyl-L-glutamate (PBLG) or poly-epsilon-carbobenzyloxy-L-lysine (PCBLL) and NMR numerical simulations. 相似文献
140.
Heinrich BW Limot L Rastei MV Iacovita C Bucher JP Djimbi DM Massobrio C Boero M 《Physical review letters》2011,107(21):216801
Low-temperature scanning tunneling microscopy and spectroscopy combined with first-principles simulations reveal a nondissociative physisorption of ferrocene molecules on a Cu(111) surface, giving rise to ordered molecular layers. At the interface, a 2D-like electronic band is found, which shows an identical dispersion as the Cu(111) Shockley surface-state band. Subsequent deposition of Cu atoms forms charged organometallic compounds that localize interface-state electrons. 相似文献