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41.
Several binary systems made from two laterally substituted azo/ester isomers, namely 2?- (and 3?-) methyl-4-substituted phenyl 4?-(4?-alkoxyphenylazo) benzoates, where the length of the terminal alkoxy group = 8 and 16 carbons, while the other terminal substituent, X, varies between CH3O, CH3, H, Br and CN groups, were investigated using differential scanning calorimetry (DSC) and phases identified by polarised light microscope (PLM). For the sake of comparison, two another binary systems made from 2?- (or 3?-) methyl-4-substituted phenyl 4?-(4?-alkoxyphenylazo) benzoates (n = 8 and X = CH3) each was mixed with its laterally neat analogue and similarly investigated. Results were discussed on the basis of constructed phase diagrams whereby various mesomorphic properties were observed dependent on X, n, and position of the lateral methyl group. In most of the cases, the mixtures exhibited eutectic compositions, while linear or nearly linear nematic and smectic A-composition temperature dependence were observed. 相似文献
42.
《中国化学》2018,36(7):587-593
An organocatalytic approach for direct conversion of racemic diarylmethanols to valuable chiral diarylmethylamines is described. Different from the previously reported elegant “borrowing hydrogen” approach, the present process employs a distinct complementary formal SN1 strategy. This approach enjoys excellent enantioselectivity, mild conditions, broad scope, and easy product derivatization. Mechanistically, control experiments also provided important insights into some notable features, such as substrate kinetic resolution and reversibility as well as the critical role of the ortho‐ hydroxy group in the substrate. 相似文献
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44.
《Magnetic resonance in chemistry : MRC》2018,56(8):767-774
A systematic study of the accuracy factors for the computation of 15N NMR chemical shifts in comparison with available experiment in the series of 72 diverse heterocyclic azines substituted with a classical series of substituents (CH3, F, Cl, Br, NH2, OCH3, SCH3, COCH3, CONH2, COOH, and CN) providing marked electronic σ‐ and π‐electronic effects and strongly affecting 15N NMR chemical shifts is performed. The best computational scheme for heterocyclic azines at the DFT level was found to be KT3/pcS‐3//pc‐2 (IEF‐PCM). A vast amount of unknown 15N NMR chemical shifts was predicted using the best computational protocol for substituted heterocyclic azines, especially for trizine, tetrazine, and pentazine where experimental 15N NMR chemical shifts are almost totally unknown throughout the series. It was found that substitution effects in the classical series of substituents providing typical σ‐ and π‐electronic effects followed the expected trends, as derived from the correlations of experimental and calculated 15N NMR chemical shifts with Swain–Lupton's F and R constants. 相似文献
45.
1,2,3-Triazolium salts draw much attentions in recent years. We developed a new synthetic method to heteroatom-functionalized triazoliums via nucleophilic substitution of 4-bromomethyltriazolium. This method afforded triazoliums with different S, N, and O heteroatom-substituents. Moreover, SN2′ reaction was observed with alcohols or hydroxides. In addition, debromination and debromomethylation reaction occurred in some cases. 相似文献
46.
The title compounds were synthesized from the selectively protected N-acylated d-glucosamine derivatives, containing α-halo carboxylic acid moieties, via intramolecular 3-O-alkylation. It was found that if the starting compound contains asymmetric electrophilic center, isomuramic acid derivatives were mainly formed, regardless of the configuration of the electrophilic carbon atom. An explanation for the observed stereochemical results was proposed on the basis of the analysis of steric interactions in the molecules of the starting compounds, as well as using the concept of anchimeric assistance. It was shown that N-acetylation of the obtained lactam derivatives and subsequent methanolysis under mild conditions led to the selective cleavage of δ-lactam ring resulting in the formation of the corresponding ester derivatives of N-acetylmuramic acid or its analogues in high yields. 相似文献
47.
Marta Chrzanowska Anna Kozakiewicz Ralph Puchta 《Journal of Coordination Chemistry》2018,71(11-13):1761-1777
AbstractThe substitution behavior of the [RuII(terpy)(ampy)Cl]Cl (terpy = 2,2′:6′,2′′-terpyridine, ampy = 2-(aminomethyl)pyridine) complex in water with several bio-relevant ligands such as chloride, thiourea and N,N′-dimethylthiourea, was investigated and compared with the reactivity of the [RuII(terpy)(bipy)Cl]Cl and [RuII(terpy)(en)Cl]Cl (bipy =2,2′-bipyridine and en?=?ethylenediamine) complexes. Earlier results have shown that the reactivity and pKa values of Ru(II) complexes can be tuned by a systematic variation of electronic effects provided by bidentate spectator chelates. The reactivity of both the chlorido and aqua derivatives of the studied Ru(II) complexes increases in the order [RuII(terpy)(bipy)X]+/2+?<?[RuII(terpy)(ampy)X]+/2+?<?[RuII(terpy)(en)X]+/2+. This finding can be accounted for in terms of π back-bonding effects provided by the pyridine ligands. The activation parameters for all the studied reactions support an associative interchange substitution mechanism. 相似文献
48.
报道了新近合成的二硫纶·取代菲咯啉铁 (Ⅱ )配合物FeLL′(L =mnt2 - ,1 ,2 二氰基乙烯 1 ,2 二硫醇离子 ,L′ =phen 5,6 dione,1 ,1 0 菲咯啉 5,6 二酮 ;5 NO2 phen ,5 硝基 1 ,1 0 菲咯啉 )的电子吸收光谱、电子发射光谱及对CdS的光敏性 ,研究了FeLL′对CdS的光敏化作用与其电子光谱间的关系 相似文献
49.
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