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261.
Abdallah Harizi Noureddine Saïd Zine Mighri Hédi Zantour 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2623-2632
A variety of 5-aryl-3-[(1-dialcoxyphosphonyl)methyl]-1,2,4-triazoles 3 has been synthesized efficiently by treatment of trialkylphosphites with 5-aryl-3-chlorométhyl-1,2,4-triazoles 2 . Compound 2 has been prepared by action of N-chloroacylimidates 1 with hydrazines. The structure of triazoles 2 and 3 have been unequivocally confirmed by means of IR, 1 H, 13 C, 31 P NMR spectroscopy and mass spectra. 相似文献
262.
Meriem Toumi Med Abderrahmane Sanhoury Michel Bordeau Noureddine Raouafi Khaled Boujlel 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):920-930
Abstract Hindered rotation in alkyldithiocarbamates of the type RR′NC(= S)SR″ [R, R′, R″ = Me, Me, Et (1); PhCH2, Me, Et (2); PhCH2, H, Et (3); PhCH2, H, Me (4) and O(CH2CH2)2, Et (5)′ has been investigated using variable-temperature 1H NMR spectroscopy in CDCl3, C6D6, and DMSO-d6 solutions. Rotational parameters were calculated by the coalescence temperature method. Nitrogen substituent effects on the free energy of activation and on the equilibrium constant of unsymmetrical conformers at room temperature are discussed. 相似文献
263.
A. A. Atalla A. M. Kamal El-Dean A. M. Gaber 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):161-166
Abstract Thermal rearrangement of 3-phenylrhodanine (I) and 5-benzylidene-3-phenylrhodanine (IV) in air has been thoroughly investigated. Homolytic cleavage of (C—S) and (C—N) bonds occurred, followed by a series of hydrogen abstractions, coupling, and cyclization reactions. The isolated products of compound (I) are CS2, CO, H2S, NH3, aniline, dibenzylamine, tribenzylamine, thioglycolic acid, phenyl isothiocyanate, bibenzyl. stilbene, p-arninoacetophenone, thiocarbanilide, 2-thioxoindole and 2,3,4,5-tetraphenylthiophene. In case of compound (IV), the isolated products are CS2, H2S, H2O, CO, phenyl isothiocyanate, benzothiophene, 2-phenylquinoline, aniline, thiocarbanilide, 2-phenylindole, cinnamic acid and polystyrene. A suitable mechanism has been suggested to account for the obtained products. 相似文献
264.
Atalla El‐Taher Omer Kotlicki Paul Harper Sergei Turitsyn Jacob Scheuer 《Laser \u0026amp; Photonics Reviews》2014,8(3):436-442
In traditional communication systems the transmission medium is considered as a given characteristic of the channel, which does not depend on the properties of the transmitter and the receiver. Recent experimental demonstrations of the feasibility of extending the laser cavity over the whole communication link connecting the two parties, forming an ultra‐long fiber laser (UFL), have raised groundbreaking possibilities in communication and particularly in secure communications. Here, a 500 km long secure key distribution link based on Raman gain UFL is demonstrated. An error‐free distribution of a random key with an average rate of 100 bps between the users is demonstrated and the key is shown to be unrecoverable to an eavesdropper employing either time or frequency domain passive attacks. 相似文献
265.
Sanjit Acharya Noureddine Abidi Rajeev Rajbhandari Frank Meulewaeter 《Cellulose (London, England)》2014,21(6):4693-4706
Cotton fabric is usually dyed with reactive dyes. During the dyeing process, a large amount of salt is required to achieve higher exhaustion of the dye from the dyebath onto the fiber. Dyeing of cotton with reactive dyes has a substantial environmental impact due to the discharge of a large volume of highly colored and saline effluents. Chemical cationization allows cotton fibers to be dyed without salt by chemically modifying cellulosic macromolecules to introduce positively charged sites. In this study, cotton fabric was cationized using (3-chloro-2-hydroxylpropyl) trimethyl-ammonium chloride (CHPTAC). Dye uptake was assessed using two reactive dyes, CI Reactive Blue 235 and CI Reactive Blue 19. Dye exhaustion kinetics were determined using a Datacolor-HueMetrix Monitor system. Analysis of variance demonstrated significant effects of CHPTAC concentration and exhaustion time on the percent exhaustion. Color strength at the end of the dyeing cycle was significantly higher for cationized fabrics compared to the control fabric. This work shows that treatment of cotton with CHPTAC enhanced dye uptake properties due to the introduction of cationic sites and resulted in superior dyeing without the addition of salt. 相似文献
266.
Diastereomerically pure cationic Rh(I) complexes derived from phosphinite thioglycosides I were used as catalysts in highly enantioselective hydrogenations of enamides. The conformational similarity of alpha-D-arabinopyranose with beta-L-galactopyranose allows the synthesis of both enantiomers of alpha-amino acid derivatives such as D- and L-DOPA in excellent ee (97% and 98%), using derivatives of the former sugar as catalyst precursors. 相似文献
267.
Khiar N Salvador Á Chelouan A Alcudia A Fernández I 《Organic & biomolecular chemistry》2012,10(12):2366-2368
Reported is a single high yielding step approximation to mixed olefin/sulfinamide ligands enclosing a chiral sulfur atom as the sole chiral center. The synthetic design is validated by a rapid optimization of the substituent at the sulfinyl sulfur, and by the synthesis of an efficient, highly enantioselective catalyst for the Rh-catalyzed 1,4-addition of boronic acids to both, cyclic and acyclic olefins. 相似文献
268.
Wolfgang G. Glasser Rajai H. Atalla John Blackwell R. Malcolm BrownJr. Walther Burchard Alfred D. French Dieter O. Klemm Yoshiharu Nishiyama 《Cellulose (London, England)》2012,19(3):589-598
The hypothesis advanced in this issue of CELLULOSE [Springer] by Bjorn Lindman, which asserts that the solubility or insolubility
characteristics of cellulose are significantly based upon amphiphilic and hydrophobic molecular interactions, is debated by
cellulose scientists with a wide range of experiences representing a variety of scientific disciplines. The hypothesis is
based on the consideration of some fundamental polymer physicochemical principles and some widely recognized inconsistencies
in behavior. The assertion that little-recognized (or under-estimated) hydrophobic interactions have been the reason for a
tardy development of cellulose solvents provides the platform for a debate in the hope that new scientific endeavors are stimulated
on this important topic. 相似文献
269.
Houcine Ghalla Noureddine Issaoui Brahim Oujia 《International journal of quantum chemistry》2012,112(5):1373-1383
This work presents a theoretical simulation of νO? H and νO? D band shapes in the polarized infrared spectra of 2‐furoic acid dimer crystals measured at liquid‐nitrogen temperature. The line shapes are studied theoretically within the framework of the anharmonic couplings between low‐frequency hydrogen‐bond vibrations and degenerate excited states of high‐frequency hydrogen vibrations in hydrogen‐bonded dimers and the anharmonic coupling between the first excited state of the fast mode and the harmonics or band combinations of some low‐frequency bending modes, which lead to Fermi resonances.This approach takes into account the adiabatic approximation, the intrinsic anharmonicity of the low‐frequency mode through a Morse potential, Davydov coupling triggered by resonance exchange between the excited states of the fast modes of the two hydrogen bonds involved in the cyclic dimer, and the direct and indirect damping of the fast‐stretching modes of the hydrogen bonds and of the bending modes. The infrared spectral density was calculated within the linear response theory by Fourier transform of the autocorrelation function of the transition dipole moment operator of the fast mode. Numerical results show that mixing of all these effects allows satisfactory reproduction of the main features of the experimental IR line shapes of crystalline H‐ and D‐bonded 2‐furoic acid at liquid‐nitrogen temperature and for different polarizations. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012 相似文献
270.
Noureddine Belmadoui 《Tetrahedron》2006,62(7):1372-1377
Irradiation of dyad 1 in aqueous acetone leads to the introduction of an acetonyl substituent at the naphthalene 5-position, to give photoproduct 2. The proposed reaction mechanism involves electron transfer from the naphthalene excited singlet state to the ketone. Neither thymine dimers, nor acetone photoadducts involving the thymine ring were detected. These photoproducts would arise from the thymine triplet excited state, which in dyad 1 must be efficiently depopulated via a fast intramolecular energy transfer to the naphthalene chromophore, due to the lower energy of its excited triplet state. 相似文献