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151.
The synthesis of a family of 1,1-diarylethylenes from an α-stannyl β-silylstyrene through a combination of a Stille coupling and a protodesilylation reaction is described. This approach avoids the problematic cine-substitution, which is a well documented side reaction during the palladium-assisted elaboration of α-substituted vinylstannanes to 1,1-disubstituted ethylenes. 相似文献
152.
153.
The synthesis of a fluorous diol 4 bearing a perfluorodecyl chain was described. A series of boronic acid were attached to 4 by esterification. The purification of the products was fulfilled by facile filtration instead of expensive and environmental troublesome fluorous liquid-liquid extraction. The Suzuki cross-coupling reactions of the formed fluorous boronates 5 underwent smoothly and the fluorous diol 4 was recycled in good yields. 相似文献
154.
155.
Simon Doherty Julian G. Knight Tom H. Scanlan Mark R. J. Elsegood William Clegg 《Journal of organometallic chemistry》2002,650(1-2):231-248
The aprotic and protic bi- and multidentate iminophosphines 2-Ph2PC6H4N=CR1R2 (R1=H, R2=Ph=2a; R1=Me R2=Ph=2b; R1=H, R2=2-thienyl=2c; R1=H, R2=C6H4-2-PPh2=2d; R1=H, R2=C6H4-2-OH=2e, R1=H, R2=C6H4-2-OH-3-But=2f; R1=H, R2=CH2C(O)Me=2g) have been prepared by the acid catalyzed condensation of 2-(diphenylphosphino)aniline with the corresponding aldehyde–ketone. Iminophosphine 2d can be reduced with sodium cyanoborohydride to give the corresponding amino-diphosphine 2-Ph2PC6H4N(H)CH2C6H4-2-PPh2 (2h). In the presence of a stoichiometric quantity of acid, 2-(diphenylphosphino)aniline reacts in an unexpected manner with benzaldehyde, salicylaldehyde, or acetophenone to give the corresponding 2,3-dihydro-1H-benzo[1,3]azaphosphol-3-ium salts and with pyridine-2-carboxaldehyde to give N-(pyridin-2-ylmethyl)-2-diphenylphosphinoylaniline, the latter of which has been characterized by single-crystal X-ray crystallography, as its palladium dichloride derivative. The attempted condensation of 2-(diphenylphosphino)aniline with pyridine-2-carboxaldehyde to give the corresponding pyridine-functionalized iminophosphine resulted in an unusual transformation involving the diastereoselective addition of two equivalents of aldehyde to give 1,2-dipyridin-2-yl-2-(o-diphenylphosphinoyl)phenylamino-ethanol, which has been characterized by a single-crystal X-ray structure determination. The bidentate iminophosphine 2-Ph2PC6H4N=C(H)Ph reacts with [(cycloocta-1,5-diene)PdClX] X=Cl, Me) to give [Pd{2-Ph2PC6H4N=C(H)Ph}ClX] and the imino-diphosphine 2-Ph2PC6H4N=C(H)C6H4-PPh2 reacts with [(cycloocta-1,5-diene)PdClMe] to give [Pd{2-Ph2PC6H4N=C(H)C6H4---PPh2}ClMe] and each has been characterized by single-crystal X-ray crystallography. The monobasic iminophosphine 2-Ph2PC6H4N=C(Me)CH2C(O)Me reacts with [Ni(PPh3)2Cl2] in the presence of NaH to give the phosphino–ketoiminate complex [Ni{2-Ph2PC6H4N=C(Me)CHC(O)Me}Cl], which has been structurally characterized. Mixtures of iminophosphines 2a–h and a palladium source catalyze the Suzuki cross coupling of 4-bromoacetophenone with phenyl boronic acid. The efficiency of these catalysts show a marked dependence on the palladium source, catalysts formed from [Pd2(OAc)6] giving consistently higher conversions than those formed from [Pd2(dba)3] and [PdCl2(MeCN)2]. Catalysts formed from neutral bi- and terdentate iminophosphines 2a–d gave significantly higher conversions than those formed from their monobasic counterparts 2e–f. Notably, under our conditions the conversions obtained with 2a–c compare favorably with those of the standards; catalysts formed from tris(2-tolyl)phosphine and tris(2,4-di-tert-butylphenyl)phosphite and a source of palladium. In addition, mixtures of [Ir(COD)Cl]2 and 2a–h are active for the hydrosilylation of acetophenone; in this case catalysts formed from monobasic iminophosphines 2e–f giving the highest conversions. 相似文献
156.
A highly efficient Pd/C-catalyzed ligandless, heterogeneous Suzuki reaction of p-(un)substituted phenyl halide with (p-substituted phenyl)boronic acid in DMF/H2O solvent in a short reaction time (0.5 h) at 75 ℃ was developed. The key for such a catalytic system was the addition of 1 equivalent of tetrabutylammonium bromide. A wide variety of substituents can be tolerated and high yields of cross coupling products were achieved. The palladium catalyst can be easily recovered and reused without significantly decreasing its efficiency. 相似文献
157.
2-Substituted secondary alcohol o-DPPB esters (o-DPPB=ortho-diphenylphosphanylbenzoyl) have been prepared and their o-DPPB-directed diastereoselective hydroformylation examined. It was found that the diastereoselectivity increased as a function of the steric demand of the substituents both at the stereogenic center and in the alkene 2-position. Hydrolytic cleavage of the o-DPPB group afforded-via the lactols 29-the corresponding lactones 30, the relative configurations of the vicinal stereogenic centers of which were ascertainable by 2D-NOESY spectroscopy. In addition, a crystal structure analysis of the hydroformylation product 2 d provided further confirmation of the relative configuration. Replacement of the ester carbonyl group of the o-DPPB by a methylene unit resulted in significantly worse diastereoselectivity in the course of the hydroformylation (34-->35), which indicates a decisive role for the ester carbonyl function. All the experimental observations were combined in a model of the origin of the 1,2-asymmetric induction during the title reaction. The key feature is the consideration of diastereomeric trigonal-bipyramidal rhodium-hydrido-olefin complexes I and II, capable on the basis of the Hammond postulate of acting as good models for the transition states of the selectivity-determining hydrometalation step. Investigation of these complexes by force-field methods indicated good correlation between theoretically predicted and experimentally determined diastereoselectivities. 相似文献
158.
Naoki KakusawaYoshinori Tobiyasu Shuji YasuikeKentaro Yamaguchi Hiroko SekiJyoji Kurita 《Tetrahedron letters》2003,44(47):8589-8592
The reaction of 12-arylethynyl-6-methyl-5,6,7,12-tetrahydrodibenzo[c,f][1,5]-azastibocines with organic halides such as acyl halides and aryl halides in the presence of PdCl2(PPh3)2 as a catalyst led to the formation of cross-coupling products, alkynyl ketones and diaryl acetylenes, in good yields. The reactivity of the ethynyl group on the 1,5-azastibocines was far superior to that on diphenyl(phenylethynyl)stibane, which brought about marked improvement in the reaction conditions (lower temperature and shorter reaction time) and in the yields of the cross-coupling products. Single-crystal X-ray analysis of the ethynyl-1,5-azastibocine showed the presence of intramolecular Sb?N interaction which should be responsible for the remarkable reactivity enhancement of the 1,5-azastibocines for this type of reaction. 相似文献
159.
In the context of a European project, a new approach of sampling of volatile polycyclic aromatic hydrocarbons (PAHs) from air was developed. In fact, the aim of this project was to test the efficiency of an air cleansing prototype reactor, which was operating by non-thermal plasmolysis. With an eye to model the atmosphere ejected by the prototype, we needed to vaporise the volatile PAHs in an air stream at concentrations as low as those recommended by European Directives (96/62/CE) for PAHs in ambient air (i.e. 1 ng m−3). Our strategy was based on the analysis of PAHs trapped in an aqueous medium, in order to avoid important losses of volatile compounds observed during the delicate desorption-concentration step when classical solid supports are used. Then a study was carried out to determine: the design of the collecting part, the flow-rate of the air sampling, the nature and concentration of chemical additives used to enhance PAH solubility in water. The very highly diluted aqueous media obtained after the bubbling step were concentrated by solid-phase extraction (SPE) on hydrophobic cartridges and analysed on-line by reversed-phase HPLC with UV and fluorimetric detections. Lastly, the sampling technique was directly applied to the outlet of the air cleansing prototype and the analysis after 3-6 h of non-thermal plasmolysis showed that the target volatile PAHs were not present in an air stream initially polluted by volatile organic compounds. 相似文献
160.
The reactions of β-naphthol with 5-diazoimidazoles and imidazolyl-5-diazonium salts containing chemically different carboxamide
groups in position 4 were studied. Heterocyclization of 4-arylcarbamoyl-5-(2-hydroxynaphthylazo)imidazoles formed in these
reactions was investigated. The presence of the NH fragment in the amide group prevents this process, the reaction giving
instead 3-substituted 3,7-dihydroimidazo[4,5-d][1,2,3]triazin-4-ones, which is due to reversibility of C-azo coupling. Methods for modification of 1-ethoxycarbonyl group in the naphtho[2,1-e]imidazo[5,1-c][1,2,4]triazine system were developed and used to prepare substituted carboxamides inaccessible by other routes.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1208–1213, July, 2006. 相似文献