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371.
Aguilar-Hernández Tanausú Contreras Manuel D. Rodríguez-Piazza Luis 《Mediterranean Journal of Mathematics》2021,18(3):1-2
Mediterranean Journal of Mathematics - The original article has been published inadvertently with errors in page number 2. 相似文献
372.
Reyna-Cavazos K. A. la Cruz A. Martínez-de Contreras David Longoria-Rodríguez F. E. 《Research on Chemical Intermediates》2022,48(3):949-967
Research on Chemical Intermediates - BiOI samples were synthesized by coprecipitation method in glycerol medium at 100 °C followed by a thermal treatment of the precursor powders at... 相似文献
373.
Rosalinda Contreras Jean Michel Grevy Zureima García‐Hernndez Marisol Gizado‐Rodriguez Bernd Wrackmeyer 《Heteroatom Chemistry》2001,12(6):542-550
A series of aminodiphenylphosphanes 1 [Ph2P‐N(H)tBu ( a ), ‐NEt2 ( b ), ‐NiPr2 ( c )], 2 [Ph2P‐NHPh ( a ), ‐NH‐2‐pyridine ( b ), ‐NH‐3‐pyridine ( c ), ‐NH‐4‐pyridine ( d ), NH‐pyrimidine ( e ), NH‐2,6‐Me2‐C6H3 ( f ), NH‐3‐Me‐2‐pyridine ( g )], 3 [Ph2P‐N(Me)Ph ( a ), ‐NPh2 ( b )], and N‐pyrrolyldiphenylphosphane 4 (Ph2P‐NC4H4) was prepared and studied by NMR (1H, 13C, 31P, 15N NMR) spectroscopy. The isotope‐induced chemical shifts 1Δ14/15N(31P) were determined at natural abundance of 15N by using HEED INEPT experiments. A dependence of 1Δ14/15N(31P) on the substituents at nitrogen was found (alkyl < H < aryl; increasingly negative values). The magnitude and sign of the coupling constants 1J(31P,15N) (positive sign) are dominated by the presence of the lone pair of electrons at the phosphorus atom. The X‐ray structural analysis of 2b is reported, showing the presence of dimers owing to intermolecular hydrogen bridges in the solid state. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:542–550, 2001 相似文献
374.
Ekaterina V. Bakhmutova Heinrich Nth Rosalinda Contreras Bernd Wrackmeyer 《无机化学与普通化学杂志》2001,627(8):1846-1854
Pseudo‐ephedrine derived 2‐imino‐1,3‐thiazolidine 1 reacts with tris(diethylamino)phosphane by stepwise replacement of the diethylamino group to give the mono‐, bis‐ and tris(imino)phosphanes 2 , 3 and 4 , respectively, of which 4 could be isolated in pure state. The analogous reaction with diethylamino‐diphenylphosphane affords the imino‐diphenylphosphane 5 . The iminophosphanes react with sulfur or selenium to give the corresponding phosphorus(V) compounds. In contrast, the reaction of the iminophosphanes with oxygen is very slow; anhydrous trimethylamine N‐oxide reacts in the melt with the phosphanes to give the oxides 4(O) and 5(O) . The molecular structures of 4(O) (in mixture with 4 ), 4(Se) , 5(S) and 5(Se) were determined by X‐ray analysis. In all cases the ring‐sulfur and the phosphorus atoms are in cis‐positions at the C=N bonds. The analogous solution structures were determined by 1H, 13C, 15N, 31P and 77Se NMR spectroscopy. In the case of the compounds 5 , 5(O) , 5(S) and 5(Se) the isotope‐induced chemical shifts 1δ14/15N(31P) were determined, using INEPT‐HEED experiments. 相似文献
375.
J. C. Cesco C. C. Denner G. O. Giubergia A. E. Rosso J. E. Prez F. S. Ortiz O. E. Taurian R. H. Contreras 《Journal of computational chemistry》1999,20(6):604-609
A mixed atomic basis set formed with ls Slater-type orbitals and 1s floating spherical Gaussian orbitals is implemented. Evaluation of multicenter integrals is carried out using a method based on expansion of binary products of atomic basis functions in terms of a complete basis set, and a systematic analysis is performed. The proposed algorithm is very stable and furnishes fairly good results for total energy and geometry. An LCAO-SCF test calculation is carried out on LiH. The trends observed show that there are some combinations of mixed orbitals that are appropriate to describe the system. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 604–609, 1999 相似文献
376.
Noemí Andrade-Lpez Armando Ariza-Castolo Rosalinda Contreras Amrica Vzquez-Olmos Norh Barba Behrens Hugo Tlahuext 《Heteroatom Chemistry》1997,8(5):397-410
The structure, dynamic behavior, protonation, methylation, and coordination sites of 2-guanidinobenzimidazole 1a were investigated. Structures of compounds [2-guanidinium-1,3,10-trihydrobenzimidazole]sulfate 1b , [2-guanidinium-1,3-dihydro-benzimidazole]sulfate 1c–1d , [2-guanidinium-1,3-dihydro-benzimidazole]tetrafluoroborate 1e , [2-guanidinium-1,3-dihydro-benzimidazole]chloride 1f , [2-guanidinium-1,3-dihydro-benzimidazole] perchlorate 1g , 2-guanidino-1-methyl-benzimidazole 2a , [2-guanidinium-1,3-dimethyl-benzimidazole]iodide 2b , [2-guanidinium-1-methyl-3-hydro-benzimidazole]chloride 2c , [2-guanidinium-1,10-dihydro-benzimidazole]acetate 3 , 2-guanidino-1-hydro-3-borane-benzimidazole 4a , 2-guanidino-1-methyl-3-borane-benzimidazole 4b , (2-guanidino-benzimidazole)dimethyltin 5 , [bis(2-guanidino-10-hydro-benzimidazole)nickel(II)] 6 , and [bis(2-guanidino-1,10-dihydro-benzimidazole)zinc(II)]nitrate 7 were determined based on 1H, 13C, and 15N NMR spectroscopy. The X-ray diffraction structures of 2a, 2b, 3, 6 , and 7 were obtained. The results show that 1a has an open structure without an intramolecular hydrogen bond in DMSO or DMF. The imidazolic N-3 is the preferred basic site in solution for protonation, methylation, and coordination and not N-10 as was suggested from semiempirical calculations. Under strong acidic conditions, diprotonation occurs at N-3 and N-10. In the solid state, 3 and 6 were protonated preferently at N10 rather than at N-1. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8: 397–410, 1997 相似文献
377.
Powerful recombination centers resulting from reactions of hydrogen with carbon–oxygen defects in n‐type Czochralski‐grown silicon
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378.
M. Leonor Contreras Diego Cortés-Arriagada Ignacio Villarroel José Alvarez Roberto Rozas 《Structural chemistry》2014,25(4):1045-1056
The hydrogen adsorption energies for nitrogen-containing carbon nanotubes (N-CNTs) and for bare carbon nanotubes were calculated using the density functional theory methods at the B3LYP/6–31-G(d) level, including dispersion force corrections. The N-CNTs were finite saturated and non-saturated single-walled carbon nanotubes that contained one or more pyrimidine units, the relative positions of which defined the different configurations of the nanotube. The chemisorption of atomic hydrogen to a full exocyclic monolayer of zigzag, armchair, and chiral N-CNTs was studied as a function of the structural parameters. Zigzag N-CNTs of any configuration, with a larger number of nitrogen atoms, a small diameter and a small length, are more reactive compared to chiral and armchair N-CNTs. The presence of nitrogen in the carbon nanotubes enhances their reactivity to chemisorb atomic hydrogen, showing exothermic energy values. In contrast, the physisorption of molecular hydrogen was endothermic for most of the studied saturated N-CNTs, even when including corrections for van der Waals interactions. The endothermicity was greatest for zigzag nanotubes, then decreased for chiral nanotubes and decreased again for armchair nanotubes. In general, the endothermicity decreased for longer nanotubes, which have larger diameters, and a small number of nitrogen atoms. The results of this study suggest that, with saturated bare carbon nanotubes, saturated, and unsaturated N-CNTs could potentially have a higher capacity as hydrogen-storage media than the corresponding unsaturated carbon nanotubes. 相似文献
379.
380.
Oxidative homocoupling of arylboronic acids catalyzed by a 4‐aminoantipyrine–Pd(II)complex
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Claudia Araceli Contreras‐Celedón José Arturo Rincón‐Medina Darío Mendoza‐Rayo Luis Chacón‐García 《应用有机金属化学》2015,29(7):439-442
A one‐step synthesis of symmetric biaryls is reported under very mild conditions via the homocoupling reaction of substituted arylboronic acids using an air‐ and moisture‐stable 4‐aminoantipyrine–Pd(II) complex as catalyst. The reaction is conducted at a low catalyst loading of 0.1 mol% at room temperature in methanol in the presence of K2CO3 as the base and KMnO4 as the oxidant. The catalytic methodology is shown to be compatible with diverse functional groups and affords the desired biphenyls in good to excellent yields. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献