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131.
132.
Alexandre BouillonJean-Charles Lancelot Jana Sopkova de Oliveira SantosValérie Collot Philipppe R BovySylvain Rault 《Tetrahedron》2003,59(50):10043-10049
This paper describes some methods for the synthesis and the isolation of novel 5 or 6-halopyridin-2-yl-boronic acids and esters 3, 4, 7. These compounds are prepared via a regioselective halogen-metal exchange using n-butyllithium and subsequent quenching with triisopropylborate starting from appropriate dihalopyridines. All substrates studied to date provided a single regioisomeric boronic acid or ester product. Additionally, these compounds have been found to undergo Pd-catalysed coupling with arylhalides and authorise a strategy to produce new pyridines libraries. 相似文献
133.
The triazinoindazolones 8 and 9 were synthesized by rearrangement of the oxadiazoles 5 and 6 or by cyclising the indazolic ethoxymethylidene-hydrazides 2 and 3. The triazinoindazolethiones 17 and 18 which were obtained by thionation of the triazinoindazolones 8 and 9 constitute the intermediates to the hydrazinoindazoles 19 and 20. The tetrrazolotriazinoindazole 21 was obtained by cyclising the hydrazinoindazole 19. The potassium indazolyldithiocarbazate 12 has been used for the synthesis of 4-thioxotriazinoindazolone 10 and 4-amino-3-thioxotriazolylindazole 15. The cyclisation of the latter gave the 3-thioxotriazinoindazolone 16. The structure of the derivatives was confirmed by 1H-nmr. 相似文献
134.
Max Robba Jean-Charles Lancelot Daniel Maume Alain Rabaron 《Journal of heterocyclic chemistry》1983,20(2):427-430
The 3H-5-(3′-indazolyl)-1,3,4-oxadiazol-2-one was obtained by cyclising the hydrazide of the 3-indazolecarboxylic acid with carbonyl chloride. The structure was assigned by 13C nmr and mass spectrometry comparing the 2H, 3H-triazino-1,2,3[4,5-b]indazoledione-1,4. Rearrangement into 3H-5-(3′-indazolyl)-1,3,4-oxadiazol-2-one precedes the fragmentation of 2H,3H-triazino-1,2,4-[4,5-b]indazoledione-1,4 upon electron-impact. 相似文献
135.
Yamien Effi Jean-Charles Lancelot Sylvain Rault Max Robba 《Journal of heterocyclic chemistry》1983,20(4):913-918
The 4,5-dihydropyrrolo[1,2-e]pyrazin-5-one (1) exhibits lactam-lactim tautomerism. N-Electrophilic substitutions could be achieved via the intermediate of the substitutions could be achieved via the intermediate of the sodium salt la. The 5-chloropyrazine 11 obtained by chlorodehydroxylation of pyrazinone 1 allowed nucleophilic substitution. Thionation of the pyrazinone 1 afforded the thioxopyrazine 27 wich gave studied and the tautomerism of the hydrazinopyrazine 14 and its derivatives are discussed in terms of hydrazone and azine structures 相似文献
136.
Xiao Feng Jean-Charles Lancelot Alain-Claude Gillard Henriette Landelle Sylvain Rault 《Journal of heterocyclic chemistry》1998,35(6):1313-1316
The synthetic pathway leading to 5,6-dihydro-4H-furo[3,2-f]pyrrolo[1,2-a][1,4]diazepines is described in four steps starting from α-bromophenones via 2-amino-3-furonitriles. 相似文献
137.
138.
Thomas Parr Lancelot Da Costa Conor Heins Maxwell James D. Ramstead Karl J. Friston 《Entropy (Basel, Switzerland)》2021,23(9)
In theoretical biology, we are often interested in random dynamical systems—like the brain—that appear to model their environments. This can be formalized by appealing to the existence of a (possibly non-equilibrium) steady state, whose density preserves a conditional independence between a biological entity and its surroundings. From this perspective, the conditioning set, or Markov blanket, induces a form of vicarious synchrony between creature and world—as if one were modelling the other. However, this results in an apparent paradox. If all conditional dependencies between a system and its surroundings depend upon the blanket, how do we account for the mnemonic capacity of living systems? It might appear that any shared dependence upon past blanket states violates the independence condition, as the variables on either side of the blanket now share information not available from the current blanket state. This paper aims to resolve this paradox, and to demonstrate that conditional independence does not preclude memory. Our argument rests upon drawing a distinction between the dependencies implied by a steady state density, and the density dynamics of the system conditioned upon its configuration at a previous time. The interesting question then becomes: What determines the length of time required for a stochastic system to ‘forget’ its initial conditions? We explore this question for an example system, whose steady state density possesses a Markov blanket, through simple numerical analyses. We conclude with a discussion of the relevance for memory in cognitive systems like us. 相似文献
139.
Kai Ueltzhffer Lancelot Da Costa Daniela Cialfi Karl Friston 《Entropy (Basel, Switzerland)》2021,23(9)
Dissipative accounts of structure formation show that the self-organisation of complex structures is thermodynamically favoured, whenever these structures dissipate free energy that could not be accessed otherwise. These structures therefore open transition channels for the state of the universe to move from a frustrated, metastable state to another metastable state of higher entropy. However, these accounts apply as well to relatively simple, dissipative systems, such as convection cells, hurricanes, candle flames, lightning strikes, or mechanical cracks, as they do to complex biological systems. Conversely, interesting computational properties—that characterize complex biological systems, such as efficient, predictive representations of environmental dynamics—can be linked to the thermodynamic efficiency of underlying physical processes. However, the potential mechanisms that underwrite the selection of dissipative structures with thermodynamically efficient subprocesses is not completely understood. We address these mechanisms by explaining how bifurcation-based, work-harvesting processes—required to sustain complex dissipative structures—might be driven towards thermodynamic efficiency. We first demonstrate a simple mechanism that leads to self-selection of efficient dissipative structures in a stochastic chemical reaction network, when the dissipated driving chemical potential difference is decreased. We then discuss how such a drive can emerge naturally in a hierarchy of self-similar dissipative structures, each feeding on the dissipative structures of a previous level, when moving away from the initial, driving disequilibrium. 相似文献
140.
H. S. El‐Kashef A. M. Kamal El‐Dean A. A. Geies J. C. Lancelot P. Dallemagne S. Rault 《Journal of heterocyclic chemistry》2000,37(6):1521-1526
The synthesis of the title compounds was achieved using the key intermediate ethyl 4,6‐dimethyl‐3‐(pyrrol‐1‐yl)thieno[2,3‐b]pyridine‐2‐ carboxylate 2. This latter compound was obtained via the interaction of the thienopyridine amino ester 1 with 2,5 dimethoxytetrahydrofuran in acidic medium. 相似文献