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排序方式: 共有273条查询结果,搜索用时 15 毫秒
161.
Henry Insuasty Braulio InsuastyEdison Castro Jairo QuirogaRodrigo Abonía Manuel NoguerasJusto Cobo 《Tetrahedron》2012,68(46):9384-9390
Novel 4,7-dihetarylpyrazolo[1,5-a][1,3,5]triazines were synthesized from three different approaches. The first one, involved a one-step reaction between 5-amino-3-hetaryl-1H-pyrazoles and O,S-diethyl hetaroylimidothiocarbonates or S,S-diethyl hetaroylimidodithiocarbonates under solvent-free conditions employing microwave irradiation as the energy source. In the second approach, conventional heating under reflux in DMF as solvent was used instead of the microwave irradiation; and the third one was achieved from a two-step sequence through the treatment of 5-amino-3-hetaryl-1H-pyrazoles with hetaroyl isothiocyanates and the subsequent S-alkylation and cyclization process in DMF as solvent. Some intermediates were isolated and characterized to support the regiochemistry of the studied reactions. The structures of the new compounds were unambiguously established by spectroscopic and analytical techniques. 相似文献
162.
Jairo Quiroga Jaime Portilla Michael B. Hursthouse Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(4):o159-o162
Molecules of the title compound [systematic name: (5‐amino‐3‐methylpyrazol‐1‐yl)(phenyl)methanone], C11H11N3O, contain an intramolecular hydrogen bond. The molecules are linked into sheets by a combination of N—H...N, C—H...O and C—H...π(arene) hydrogen bonds. Comparisons are made with the hydrogen‐bonded structures of some related compounds. 相似文献
163.
Jairo Quiroga Jorge Trilleras Dayana Pantoja Braulio Insuasty Justo Cobo 《Tetrahedron letters》2010,51(36):4717-2666
New pyrazolo[3,4-b]pyridine-5-spirocycloalkanedione derivatives were prepared via three-component reaction between 5-(4-R-benzylamino)pyrazoles, cyclic β-diketones and paraformaldehyde. The use of indandione as β-diketone resulted in the formation of two products, the pyrazolo[3,4-b]pyridine-5-spiroindanediones and 3-tert-butyl-1-phenylindeno[2,3-e]pyrazolo[3,4-b]pyridine. The structures of the pyrazolo[3,4-b]pyridine-5-spirocycloalkanedione were confirmed by single-crystal X-ray diffraction. This protocol provides a simple one-step synthetic methodology with the advantages of easy work-up, mild reaction conditions and environmentally benign. 相似文献
164.
Jairo Quiroga Paola A. Acosta Rodrigo Abonía Manuel Nogueras Justo Cobo 《Tetrahedron letters》2010,51(41):5443-402
A series of 6-aryl-5-(1-cyclohexen-1-yl)pyrrolo[2,3-d]pyrimidines 9a-q were obtained by the three-component reaction between 6-aminopyrimidines 6, 7, 8, dimedone 2, and arylglyoxal 5a,b. The unexpected cyclization process was established by NMR and X-ray diffraction measurements. 相似文献
165.
Ana Carolina Gaviria-Castillo Jesús Daniel Artunduaga-Tole Juan Diego Rodríguez-Rubiano Jairo Alberto Zuñiga-Andrade Daniel Ricardo Delgado Abolghasem Jouyban 《Physics and Chemistry of Liquids》2019,57(1):55-66
The equilibrium solubility and preferential solvation of triclocarban in {1,4-dioxane (1) + water (2)} mixtures at 298.15 K was reported. Mole fraction solubility varies continuously from 2.85 × 10–9 in neat water to 2.39 × 10–3 in neat 1,4-dioxane. Solubility behaviour was adequately correlated by means of the Jouyban-Acree model. Based on the inverse Kirkwood-Buff integrals, preferential solvation parameters were calculated. Triclocarban is preferentially solvated by water in water-rich mixtures (0.00 < x1 < 0.18) and also in 1,4-dioxane-rich mixtures (0.78 < x1 < 1.00) but preferentially solvated by 1,4-dioxane in mixtures with similar solvent compositions. 相似文献
166.
Manfredo Hrner Almir Luis Brancher Angela Silva Jairo Bordinhao Ccilia M. Mssmer 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(5):o303-o304
The crystal structure of the title compound, C14H12N4O3, shows that the stereochemistry about the N=N double bond of the N=N—N(H) moiety is trans. The whole molecule is almost planar (r.m.s. deviation = 0.0654 Å), the interplanar angle between the phenyl rings being 0.7 (1)° and the largest interplanar angle being that between the phenyl ring and the nitro group of the 4‐nitrophenyl substituent [11.5 (2)°]. Intermolecular N—H⋯O interactions between molecules related by translation give rise to chains along the [110] and [10] directions, and these chains are held together by N⋯O π–π interactions. An unequal distribution of the double‐bond character among the N atoms suggests a delocalization of π electrons over the diazoamine group and the adjacent aryl substituents. 相似文献
167.
A potential-energy force field for methanol is calculated at the coupled-cluster singles doubles and noniterative triples correction level using the correlation-consistent polarized valence triple zeta basis set. The force field describes the coupled molecular vibrations, including the cubic and quartic anharmonicites, as a function of the torsional coordinate. The resulting molecular eigenstates are calculated using a combination of perturbative and variation calculations following the approach of Castillo-Chará and Sibert [J. Chem. Phys. 119, 11671 (2003)]. The energies, including torsional tunneling splittings, are compared with available spectroscopic data for all the fundamentals. Excellent agreement is found. Varying the torsional mass, correlation plots are constructed in order to elucidate the complex role of torsion-vibration coupling. 相似文献
168.
Jairo Quiroga Jorge Trilleras Braulio Insuasty Manuel Nogueras Justo Cobo 《Tetrahedron letters》2009,50(46):6404-2654
The reactions of N4- and 5-cyanoacetyl derivates of 4-aminopyrimidines with aromatic aldehydes have yielded the N-(pyrimidin-4-yl)-3-arylacrylamides and the dihydropyrido[2,3-d]pyrimidines, respectively. The first reaction was a Claisen-Schmidt reaction catalyzed by base, and the second one proceeded via thermal cyclocondensation. 相似文献
169.
Bienvenido Barraza Martínez Robert Denk Jairo Hernández Monzón 《manuscripta mathematica》2014,144(3-4):349-372
In this paper, we consider pseudodifferential operators with operator-valued symbols and their mapping properties, without assumptions on the underlying Banach space E. We show that, under suitable parabolicity assumptions, the \({W_p^k(\mathbb{R}^n, E)}\) -realization of the operator generates an analytic semigroup. Our approach is based on oscillatory integrals and kernel estimates for them. An application to non-autonomous pseudodifferential Cauchy problems gives the existence and uniqueness of a classical solution. As an example, we include a discussion of coagulation–fragmentation processes. 相似文献
170.
Jairo Gonzlez Javier Santamaría Alfredo Ballesteros 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(46):13882-13885
A gold(I)‐catalyzed synthesis of indanones from trimethylsilylacetylenes and acylsilanes is presented. The reaction is initiated through a synergistic acylsilane activation–gold acetylide formation and involves consecutive alkyne σ‐gold(I) addition, π‐activation, and 1,2‐migration of a silyl group. Studies performed on the reaction mechanism allowed to establish the nature of the silyl migrating group and invoke the participation of a gold(I) carbenoid intermediate. The reaction is completed by a gold(I) C H functionalization step. 相似文献