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61.
Alvarez P Lastra E Gimeno J Bassetti M Falvello LR 《Journal of the American Chemical Society》2003,125(9):2386-2387
Intramolecular [2 + 2] cycloaddition of two C=C bonds in vinylidene complexes [Ru(eta5-C9H7){=C=C(R)H}(PPh3){kappa1-(P)-PPh2(C3H5)][BF4] affords cyclobutylidene complexes [Ru(eta5-C9H7){kappa2-(P,C)-(=CC(R)HCH2CHCH2PPh2)}(PPh3)][BF4], which can be also obtained by reaction of terminal alkynes with [Ru(eta5-C9H7)(PPh3){kappa3-(P,C,C)-PPh2(C3H5)}][PF6]. The reaction proceeds under mild conditions via vinylidene complexes, and the activation parameters were determined by kinetic studies. 相似文献
62.
J Pacheco A Alvarez I García F Angel-Bello 《The Journal of the Operational Research Society》2012,63(5):569-581
The work addressed in this paper is motivated from a real problem proposed to the authors by a bakery company in Northern Spain. The objective is to minimize the total distance travelled for the daily routes over the week. In order to reduce this total distance, some flexibility in the dates of delivery is introduced. A mixed-integer linear model for the problem is formulated. In addition, a two-phase method based in GRASP and path-relinking metaheuristic strategies is proposed. Computational experiments show that the method performs very well, obtaining high-quality solutions in short computational times. Moreover, when it is applied to real-data-based instances, the obtained solutions considerably reduce transportation costs over the planning horizon. 相似文献
63.
P. Perez‐Tejeda A. Jimenez‐Ruiz E. M. Grueso R. Prado‐Gotor C. Carrasco A. Pastor N. Alvarez M. Garcia‐Lora M. Garcia‐Pageo 《国际化学动力学杂志》2013,45(12):780-786
The electron transfer reaction between [Ru(NH3)5pz]2+ and [Co(C2O4)3]3? was studied in the presence of monomers and aggregates of bile salts (sodium deoxycholate, sodium taurodeoxycholate, and sodium glycocholate) at 298.2 ± 0.1 K. The results show a decreasing rate constant with the successive addition of bile salts. To rationalize the trends of the reaction rate on the [bile salts], two models were used. One of them takes into account the aggregation feature by considering a stepwise self‐association between monomers, whereas the other assumes the formation of a critical micellar concentration. Binding constants between [Ru(NH3)5pz]2+ species and deoxycholate or taurodeoxycholate aggregates were higher than that for glycocholate aggregates. These results are consistent with the way in which the monomers are added to form the bile anion aggregates. 相似文献
64.
Prof. Santiago Alvarez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4350-4377
After briefly reviewing the applications of the coordination ability indices proposed earlier for anions and solvents toward transition metals and lanthanides, a new analysis of crystal structures is applied now to a much larger number of coordinating species: anions (including those that are present in ionic solvents), solvents, amino acids, gases, and a sample of neutral ligands. The coordinating ability towards s-block elements is now also considered. The effect of several factors on the coordinating ability will be discussed: (a) the charge of an anion, (b) the chelating nature of anions and solvents, (c) the degree of protonation of oxo-anions, carboxylates and amino carboxylates, and (d) the substitution of hydrogen atoms by methyl groups in NH3, ethylenediamine, benzene, ethylene, pyridine and aldehydes. Hit parades of solvents and anions most commonly used in the areas of transition metal, s-block and lanthanide chemistry are deduced from the statistics of their presence in crystal structures. 相似文献
65.
Sergio Auricchio Ada M. Truscello Mirvana Lauria Stefano V. Meille 《Tetrahedron》2012,68(36):7441-7449
2H-Azirines were found to react with imines, enaminones and enaminoesters in the presence of metal salts. Imidazoles, pyrroles and new pyrrolinones derivatives are isolated in good overall yields. The role of metal salts was investigated as they can act as Lewis acids or electron donors. Mechanisms are proposed suggesting that imidazoles arise from addition of azirine to imines via radical or ionic mechanism; pyrroles and pyrrolinones are obtained from azirines with enamino derivatives when the salt acts as a Lewis acid. In the latter case the properties of the metallic compound influence the reaction regioselectivity. 相似文献
66.
In network problems, latency is associated with the metric used to evaluate the length of the path from a root vertex to each vertex in the network. In this work we are dealing with two applications or variations of the minimum latency problem known as the repairman problem and the deliveryman problem. We have developed two integer formulations for the minimum latency problem and compared them with other two formulations from the literature for the time-dependent traveling salesman problem. The present work highlights the similarities and differences between the different formulations. In addition, we discuss the convenience of including a set of constraints in order to reduce the computation time needed to reach the optimal solution. We have carried out extensive computational experimentation on asymmetrical instances, since they provide the characteristics of the deliveryman and repairman problems in a better way. 相似文献
67.
68.
Eva Alvarez de Eulate Shane O'Sullivan Sharon Fletcher Prof. Dr. Philip Newsholme Prof. Dr. Damien W. M. Arrigan 《化学:亚洲杂志》2013,8(9):2096-2101
The behavior of proteins and polypeptides at electrified aqueous–organic interfaces is of benefit in label‐free detection strategies. In this work, rat amylin (or islet amyloid polypeptide) was studied at the interface formed between aqueous liquid and gelled organic phases. Amylin is a polypeptide that is co‐secreted with insulin from islet beta‐cells and is implicated in fibril formation. In this study, rat amylin was used, which does not undergo aggregation. The polypeptide underwent an interfacial transfer process, from water to the gelled organic phase, under applied potential stimulation. Cyclic voltammetry revealed steady‐state forward and peak‐shaped reverse voltammograms, which were consistent with diffusion‐controlled water‐to‐organic transfer and thin‐film stripping or desorptive back‐transfer. The diffusion‐controlled forward current was greater when amylin was present in an acidic aqueous phase than when it was present in an aqueous phase at physiological pH; this reflects the greater charge on the polypeptide under acidic conditions. The amylin transfer current was concentration dependent over the range 2–10 μM , at both acidic and physiological pH. At physiological pH, amylin was selectively detected in the presence of a protein mixture, which illustrated the bioanalytical possibilities for this electrochemical behavior. 相似文献
69.
Luis Alvarez Thon Carlos Bustos Fernando Diaz‐Marín Maria Teresa Garland Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(1):101-104
The title compound, C17H10F5N5O2, is described and compared with its 4‐nitrophenyl isomer [Bustos, Sánchez, Schott, Alvarez‐Thon & Fuentealba (2007). Acta Cryst. E 63 , o1138–o1139]. The title molecule presents its nitro group split into two rotationally disordered components, which in conjunction with the rotation of the `unclamped' rings constitute the main molecular differences. Packing is directed by a head‐to‐tail type `I' C—F...F—C interaction, generating double‐chain strips running along [100]. These substructures are interlinked by a variety of weak F...F, O...F, F...π and O...π interactions. 相似文献
70.
Luis Alvarez‐Thon Carlos Bustos Katherina Espinoza‐Santibaez Maria Teresa Garland Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(10):1200-1204
The title compound, C17H11F5N4O, is described and compared with two closely related analogues in the literature. There are two independent molecules in the asymmetric unit, linked by N—H...O hydrogen bonds and π–π interactions into dimeric entities, presenting a noticeable noncrystallographic C2 symmetry. These dimers are in turn linked by a medium‐strength type‐I C—F...F—C interaction into elongated tetramers. Much weaker C—H...F contacts link the tetramers into broad two‐dimensional substructures parallel to (101). 相似文献