全文获取类型
收费全文 | 970篇 |
免费 | 25篇 |
国内免费 | 5篇 |
专业分类
化学 | 507篇 |
晶体学 | 2篇 |
力学 | 67篇 |
数学 | 223篇 |
物理学 | 201篇 |
出版年
2023年 | 8篇 |
2022年 | 15篇 |
2021年 | 17篇 |
2020年 | 19篇 |
2019年 | 23篇 |
2018年 | 20篇 |
2017年 | 20篇 |
2016年 | 53篇 |
2015年 | 24篇 |
2014年 | 32篇 |
2013年 | 51篇 |
2012年 | 70篇 |
2011年 | 88篇 |
2010年 | 49篇 |
2009年 | 43篇 |
2008年 | 59篇 |
2007年 | 69篇 |
2006年 | 41篇 |
2005年 | 42篇 |
2004年 | 40篇 |
2003年 | 42篇 |
2002年 | 24篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 1篇 |
1974年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有1000条查询结果,搜索用时 15 毫秒
911.
Zurab Berezhiani Fabrizio Nesti 《The European Physical Journal C - Particles and Fields》2012,72(4):1974
Present experiments do not exclude that the neutron n oscillates, with an appreciable probability, into its invisible degenerate twin from a parallel world, the so-called mirror
neutron n′. These oscillations were searched experimentally by monitoring the neutron losses in ultra-cold neutron traps, where they
can be revealed by the magnetic field dependence of n–n′ transition probability. In this work we reanalyze the experimental data acquired by the group of A.P. Serebrov at Institute
Laue–Langevin, and find a dependence at more than 5σ away from the null hypothesis. This anomaly can be interpreted as oscillation of neutrons to mirror neutrons with a timescale
of few seconds, in the presence of a mirror magnetic field order 0.1 G at the Earth. This result, if confirmed by future experiments,
will have deepest consequences for fundamental particle physics, astrophysics and cosmology. 相似文献
912.
Gabriele Gabrielli Fabrizio Melani Sara Bernasconi Carlotta Lunghi Barbara Richichi Patrick Rollin 《Journal of carbohydrate chemistry》2013,32(3):124-141
Improved synthesis of 1,3-disaccharides, obtained diastereomerically pure by [4+2] hetero cycloadditions between glycals and α -thiono-β -keto-δ -lactones, has been reported. The choice of appropriate protecting groups for β -keto-δ -lactones, stable under cycloaddition conditions employed, sensibly shortened the synthesis of heterodienic precursors. The first example of a β -oxy-imino-δ -lactone synthesized from β -keto-δ -lactones was also reported. Molecular modeling and conformational evaluations about the cycloaddition features allowed tentatively rationalizing the experimental results. 相似文献
913.
Fabrizio Broglia 《Annali di Matematica Pura ed Applicata》1986,146(1):185-216
Sunto In questo lavoro si danno condizioni sufficienti per un ricoprimento di una varietà differenziabile V affinchè il suo nerbo abbia lo stesso tipo P.L. di V e si prova l'esistenza di una larga classe di siffatti ricoprimenti.
The author is member of G.N.S.A.G.A. of the C.N.R. and partially supported by a N.A.T.O.-C.N.R. fellowship. 相似文献
The author is member of G.N.S.A.G.A. of the C.N.R. and partially supported by a N.A.T.O.-C.N.R. fellowship. 相似文献
914.
Baltrusaitis RM Becker JJ Blaylock GT Brown JS Bunnell KO Burnett TH Cassell RE Coffman D Cook V Coward DH Dado S Dorfan DE Dubois GP Duncan AL Einsweiler KF Eisenstein BI Fabrizio R Gladding G Grancagnolo F Hamilton RP Hauser J Heusch CA Hitlin DG Köpke L Lockman WS Mallik U Mockett PM Mozley RF Nappi A Odian A Partridge R Perrier J Plaetzer SA Richman JD Roehrig JR Russell JJ Sadrozinski HF Scarlatella M Schalk TL Schindler RH Seiden A Simopoulos C Sleeman JC Spadafora AL Stockdale IE 《Physical review letters》1985,55(18):1842-1845
915.
Baltrusaitis RM Becker JJ Blaylock GT Bolton T Brown JS Bunnell KO Burnett TH Cassell RE Coffman D Cook V Coward DH Cui H Dado S Del Papa C Dorfan DE Dubois GP Duncan AL Eigen G Einsweiler KF Eisenstein BI Fabrizio R Favart D Gladding G Grancagnolo F Guy AD Hamilton RP Hauser J Heusch CA Hitlin DG Köpke L Lockman WS Mallik U Matthews CG Mockett PM Moss L Mozley RF Nappi A Nemati B Odian A Partridge R Perrier J Plaetzer SA Richman JD Roehrig J Russell JJ Sadrozinski HF Scarlatella M Schalk TL 《Physical review letters》1986,56(2):107-110
916.
Barison S Daolio S Fabrizio M De Battisti A 《Rapid communications in mass spectrometry : RCM》2004,18(3):278-284
DSA metal oxide electrodes such as the RuO(2)/IrO(2)/TiO(2) mixed system are widely studied for their excellent electrocatalytic activity. In order to understand their catalytic properties, the comprehension of the surface chemistry involved during electrochemical treatments is crucial. With this aim, RuO(2)/IrO(2)/TiO(2) mixed-oxide electrodes having various noble metal contents were studied by means of secondary ion mass spectrometry (SIMS). In particular, cathodic and anodic polarization and O(2) evolution reactions were carried out to test the electrode behaviour and SIMS analyses were performed after all these treatments. In this way, surface changes induced by electrochemical treatments and depending on electrode composition were widely investigated by SIMS, revealing, for example, the presence of hydration or preferential dissolution phenomena induced by electrochemical processing. 相似文献
917.
Fabrizio Melani Lucia Cecchi Guido Filacchioni 《Journal of heterocyclic chemistry》1984,21(3):813-815
Ethyl 3(5)-formylpyrazole-5(3)-carboxylate, 2-nitrobenzyl bromide or 2-nitrobenzoyl chloride are the starting basic materials to prepare with a few reaction steps, pyrazolo[5,1-c][1,4]benzodiazepines bearing at position 2 a substituted propionic chain ( 7–9 ) or bearing at position 5 a carbonyl group ( 12 ). Compounds 7–9, 12 are to be considered aza analogs of the antitumor antibiotic antramycin. 相似文献
918.
Federico Marini Fabrizio Balestrieri Remo Bucci Antonio L. Magrì Domenico Marini 《Microchemical Journal》2003,74(3):239-248
Supervised pattern recognition appears to be a useful tool to authenticate foodstuffs according to their geographical or varietal origin, when a set of samples whose classification is known a priori are available. In this work, linear discriminant analysis and artificial neural networks trained by the back-propagation algorithm have been used to discriminate rice bran oils manufactured in three different countries (Italy, Thailand and Switzerland) according to their geographical origin. The variables to be included in the mathematical models have been chosen by means of Fisher F-ratio value among the chemical indices routinely determined on vegetable oils (particularly fatty acids, triglycerides and sterol composition). The prediction ability of all the classifiers was 100% as evaluated by cross-validation. 相似文献
919.
Fabrizio Rodante 《Thermochimica Acta》1979,34(1):29-34
Enthalpic and entropic contributions to substituent effects for the ionization of m-and p-nitrobenzoic acids are examined, ranging from pure water to 0.8 mole fraction DMSO. The effect of the medium on the substituent and reaction constants is explained in terms of solute—solvent interactions. No structure-breaking effect was found. 相似文献
920.
Fabrizio Rodante 《Thermochimica Acta》1979,31(2):221-226
Separate enthalpic and entropic contributions to substituent effects on the dissociation of m- and p-chlorobenzoic acids in water-dimethylsulfoxide mixtures ranging from 0 to 0.8 mole fraction DMSO are presented.The effect of the medium on the substituent and reaction constants for the ionization processes is explained in terms of solute-solvent interactions and related structure breaking. 相似文献