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排序方式: 共有481条查询结果,搜索用时 15 毫秒
411.
412.
Orazio A. Attanasi Silvia Bartoccini Gianfranco Favi Gianluca Giorgi Francesca R. Perrulli Stefania Santeusanio 《Tetrahedron》2012,68(2):608-613
1,2-Diaza-1,3-dienes (DDs) undergo, under neutral conditions, N-nucleophilic attack from a 4-ethoxycarbonylisoxazol-5-one derivative. The first aza-Michael addition is followed by an intramolecular second, affording a fused heterobicyclic system that, upon ring opening and decarboxylation processes, gives rise to novel substituted imidazoles with an acetate functionality in the 2-position. On the contrary, under the same reaction conditions, 3-phenylisoxazol-5-one provides a double Michael addition at two units of DD involving first the C-4 and then the N-2 of the heterocycle. The resulting diadduct spontaneously undergoes ring-opening/ring-closing process that concludes with a ring enlargement of the heterocycle providing the 1,3-oxazin-6-one derivative. 相似文献
413.
Dr. Gabriel Canard Judicaelle Andeme Edzang Zhongrui Chen Matthieu Chessé Dr. Mourad Elhabiri Dr. Michel Giorgi Dr. Olivier Siri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(16):5756-5766
Six tetraaza[1.1.1.1]cyclophane derivatives bearing peripheral amide groups were prepared according to two distinct synthetic strategies that depend on the connection pattern between the aryl units. NMR experiments combined with the X‐ray structures of two tetraamide derivatives 4 b and 10 show that these cavitands adopt a 1,3‐alternate conformation both in solution and in the solid state. Consequently, the four amide groups of the aza[1.1.1.1]‐m,m,m,m‐cyclophane isomer 10 can contribute to the same recognition process towards neutral water molecules or anion guests. NMR experiments, mass spectrometry analyses and single‐crystal X‐ray structures confirm the anion‐binding ability of this receptor. Absorption spectrophotometric titrations in nonpolar solvents provided evidence for the selectivity of 10 to chloride anions in the halide series, with a corresponding association constant Ka reaching 2.5×106 m ?1. 相似文献
414.
Konrad Pietruk Magorzata Gbylik-Sikorska Beata ebkowska-Wieruszewska Anna Gajda Mario Giorgi Irene Sartini Piotr Jedziniak 《Molecules (Basel, Switzerland)》2021,26(7)
Paracetamol/acetaminophen (APAP) is one of the most popular pharmacologically active substances used as an analgesic and antipyretic agent. The metabolism of this drug occurs in the liver and leads to the formation of two main metabolites—glucuronic acid and sulfate derivate. Despite the wide use of paracetamol in veterinary medicine, a handful of analytical methods were published for the determination of paracetamol residues in animal tissues. In this paper, a multimatrix method has been developed for the determination of paracetamol and two metabolites—paracetamol sulfate (PS) and p-Acetamidophenyl β-D-glucuronide (PG). A validation procedure was conducted to verify method reliability and fit purpose as a tool for analyzing acetaminophen and metabolites in muscle, liver, lung, and kidney samples from different species of animals. Established validation parameters were in agreement with acceptable criteria laid by the European legislation. The initial significant matrix effect was successfully reduced by implementing an internal standard—4-Acetamidophenyl β-D-glucuronide-d3 (PG-d3, IS). The usefulness of the developed method was verified by analyzing samples from an experiment in which paracetamol was administrated to geese. 相似文献
415.
A linear viscoelastic solid is considered along with the complete set of thermodynamic restrictions on the relaxation function. It is shown that such reslrictions imply the validity of a dissipativity condition, so far regarded as unrelated to the second law. Next it is remarked that the thermodynamic restrictions imply the convexity of a commonly used bilinear functional and the stationarity only if the class of displacement field is appropriate. Then it is proved that the Laplace transform of the solution to the mixed problem gives the strict minimum of a bilinear functional and vice versa. Finally, a bilinear functional with a weight function is considered and it is shown that the solution to the mixed problem gives the strict minimum and vice versa. 相似文献
416.
Piero Baglioni Debora BertiMassimo Bonini Emiliano CarrettiLuigi Dei Emiliano FratiniRodorico Giorgi 《Advances in colloid and interface science》2014
Past restorations performed with acrylic and vinyl polymers showed detrimental effects to wall paintings that lead to the complete disfiguration of the painted surfaces. The removal of these materials performed with the traditional solvent-based methodology represents a real challenge to conservators and usually achieves very poor results. This review reports on the new palette, nowadays available to restorers, based on microemulsions, micellar systems, physical and chemical gels specifically formulated for the cleaning of cultural heritage artefacts. These systems have been developed in the last twenty years within the cultural framework of colloids and surface science. 相似文献
417.
418.
De Giorgi M Vasanelli A Rinaldi R Anni M Lomascolo M Antonaci S Passaseo A Cingolani R Taurino A Catalano M Di Fabrizio E 《Micron (Oxford, England : 1993)》2000,31(3):245-251
We show how the electronic states of quantum wires and quantum dots can be evaluated exactly starting from the profile of the nanostructure observed by transmission electron microscopy, scanning tunneling microscopy and atomic force microscopy. The calculated quantization energies reproduce the energy position of the luminescence resonances in the optical spectra of different samples, without fitting parameters. 相似文献
419.
S. Marchetti R. Simili M. Giorgi 《International Journal of Infrared and Millimeter Waves》1993,14(7):1425-1433
By tuning a high pressure CO2 laser (HPL) around strong ammonia lines nearly coincident with CO2 lines an of-fresonant absorption is observed which can be confirmed by the superfluorescent MIR emission. This effect is related to a two frequency v1, v3 HPL emission in the regime of moderate pulling. Around a strong absorption line a mixed v4=2v1–v3 frequency is produced that is strongly absorbed 相似文献
420.
Di‐ and Triphosphate Recognition and Sensing with Mono‐ and Dinuclear Fluorescent Zinc(II) Complexes: Clues for the Design of Selective Chemosensors for Anions in Aqueous Media 下载免费PDF全文
Dr. Francesco Bartoli Prof. Andrea Bencini Dr. Alessandra Garau Prof. Claudia Giorgi Prof. Vito Lippolis Dr. Alessandro Lunghi Prof. Federico Totti Prof. Barbara Valtancoli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(42):14890-14901
The synthesis of a new ligand (L1) containing two 1,4,7‐triazacyclononane ([9]aneN3) moieties linked by a 4,5‐dimethylenacridine unit is reported. The binding and fluorescence sensing properties toward Cu2+, Zn2+, Cd2+, and Pb2+ of L1 and receptor L2, composed of two [9]aneN3 macrocycles bridged by a 6,6′′‐dimethylen‐2,2′:6′,2′′‐terpyridine unit, have been studied by coupling potentiometric, UV/Vis absorption, and emission measurements in aqueous media. Both receptors can selectively detect Zn2+ thanks to fluorescence emission enhancement upon metal binding. The analysis of the binding and sensing properties of the Zn2+ complexes toward inorganic anions revealed that the dinuclear Zn2+ complex of L1 selectively binds and senses the triphosphate anion (TP), whereas the mononuclear Zn2+ complex of L2 displays selective recognition of diphosphate (DP). Binding of TP or DP induces emission quenching of the Zn2+ complexes with L1 and L2, respectively. These results are exploited to discuss the role played by pH, number of coordinated metal cations, and binding ability of the bridging units in metal and/or anion coordination and sensing. 相似文献