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81.
Minko S Kiriy A Gorodyska G Stamm M 《Journal of the American Chemical Society》2002,124(13):3218-3219
Single flexible polyelectrolyte molecules of poly(2-vinylpyridine) undergo conformational transition from a stretched wormlike coil to a necklace-like globule, and to a compact globule depending on pH and ionic strength in aqueous solution in good agreement with recent theoretical reports. AFM investigations allow the visualization of details of the chain conformation on mica and the extraction of quantitative statistics of molecular dimensions. 相似文献
82.
The work deals with the problem of determination of automobile petrol of various octane numbers and petroleum contamination of some objects on the basis of analysis of photoluminescence spectra of automobile petrol samples. For this purpose steady state luminescence properties of samples of automobile petrol of different types being in sale were measured. Samples of automobile petrol diluted in hexane were prepared and their luminescence spectra were measured at room and liquid nitrogen temperatures of samples. We constructed concentration dependences of luminescence intensity of both wide band luminescence of liquid solutions obtained at room temperature and peak intensities of luminescence lines of quasi linear spectra of solutions frozen at 77 K. Possibility to use luminescence method for analysis of petrol pollutions on some objects is illustrated by results of investigation of pine-wood pieces contaminated by automobile petrol. 相似文献
83.
Alexander B. Rozhenko Yuliia S. Horbenko Andrii A. Kyrylchuk Evgenij V. Zarudnitskii Sergiy S. Mykhaylychenko Yuriy G. Shermolovich Andriy V. Grafov 《Molecules (Basel, Switzerland)》2022,27(5)
Recently, an unusual elongation of the C-S bond was observed experimentally for some sulfur-containing heterocycles. Using a superior ab initio (SCS-MP2/cc-pVTZ) level of theory, we showed that the phenomenon can be explained by a contribution of a donor–acceptor adduct of a carbene with an unsaturated ligand. One may achieve further elongation of the C-S bond, eventually turning it to a coordinate one, by increasing the stability of each part of the system as, e.g., in the utmost case of spiro adducts with Arduengo carbenes. The effect of carbene stability was quantified by employing the isodesmic reactions of carbene exchange. 相似文献
84.
85.
Olga I. Kalchenko Sergiy O. Cherenok Andriy V. Solovyov Vitaly I. Kalchenko 《Chromatographia》2009,70(5-6):717-721
The addition of calix[4]arenes to MeCN/H2O or MeOH/MeCN/THF/H2O mobile phases improves LC separation of benzene or uracil derivatives on Separon SGX C18 or Separon SGX NH2 supports. Structure of the calixarenes and their host–guest supramolecular complexes with the analytes are discussed in context of the LC separation. 相似文献
86.
[reaction: see text] The concecutive Criegee rearrangement reactions were studied for tert-butyl trifluoroacetate, triarylcarbinols, and benzophenone ketales with trifluoroperacetic acid (TFPAA) in trifluoroacetic acid (TFA). The formation of methyl acetate and methyl trifluoroacetate indicates that the consecutive double-O-insertion process has taken place for tert-butyl trifluoroacetate. The intermediate dimethoxymethylcarbonium ion was detected below 5 degrees C. A consecutive triple-O-insertion process has been observed for triarylmethanols and benzophenone ketals. A new high yield method of corresponding diaryl carbonates synthesis was developed. 相似文献
87.
We have developed a liquid-phase synthesis of combinatorial libraries of new disubstituted 4-oxo-2-thioxo-1,2,3,4-tetrahydroquinazolines and trisubstituted 4-oxo-3,4-dihydroquinazoline-2-thioles. The former were prepared using two general procedures: (i) cyclization of substituted methyl anthranilates with isothiocyanates, or (ii) cyclization of substituted 2-(methylcarboxy)benzeneisothiocyanates with primary amines or hydrazines. 4-Oxo-3,4-dihydroquinazoline-2-thioles were prepared by S-alkylation of disubstituted 4-oxo-2-thioxo-1,2,3,4-tetrahydroquinazolines with alkyl or aryl halides. The hydrolysis of methyl benzimidazo[1,2-c]quinazoline-6(5H)-thione-3-carboxylate led to the corresponding acid. This acid was utilized in the synthesis of new benzimidazo[1,2-c]quinazoline-6(5H)-thione-3-carboxamide and S-substituted 6-mecaptobenzimidazo[1,2-c]quinazoline-3-carboxamide libraries. 相似文献
88.
Serhii Holota Sergiy Komykhov Stepan Sysak Andrzej Gzella Andriy Cherkas Roman Lesyk 《Molecules (Basel, Switzerland)》2021,26(4)
The present paper is devoted to the search for drug-like molecules with anticancer properties using the thiazolo[3,2-b][1,2,4]triazole-6-one scaffold. A series of 24 novel thiazolo-[3,2-b][1,2,4]triazole-6-ones with 5-aryl(heteryl)idene- and 5-aminomethylidene-moieties has been synthesized employing three-component and three-stage synthetic protocols. A mixture of Z/E-isomers was obtained in solution for the synthesized 5-aminomethylidene-thiazolo[3,2-b]-[1,2,4]triazole-6-ones. The compounds have been studied for their antitumor activity in the NCI 60 lines screen. Some compounds present excellent anticancer properties at 10 μM. Derivatives 2h and 2i were the most active against cancer cell lines without causing toxicity to normal somatic (HEK293) cells. A preliminary SAR study had been performed for the synthesized compounds. 相似文献
89.
Xu C Losytskyy MY Kovalska VB Kryvorotenko DV Yarmoluk SM McClelland S Bianco PR 《Journal of fluorescence》2007,17(6):671-685
The dimeric cyanine dyes, YOYO-1 and TOTO-1, are widely used as DNA probes because of their excellent fluorescent properties.
They have a higher fluorescence quantum yield than ethidium homodimer, DAPI and Hoechst dyes and bind to double-stranded DNA
with high affinity. However, these dyes are limited by heterogeneous staining at high dye loading, photocleavage of DNA under
extended illumination, nicking of DNA, and inhibition of the activity of DNA binding enzymes. To overcome these limitations,
seven novel cyanine dyes (Cyan-2, DC-21, DM, DM-1, DMB-2OH, SH-0367, SH1015-OH) were synthesized and tested for fluorescence
emission, resistance to displacement by Mg2+, and the ability to function as reporters for DNA unwinding. Results show that Cyan-2, DM-1, SH-0367 and SH1015-OH formed
highly fluorescent complexes with dsDNA. Of these, only Cyan-2 and DM-1 exhibited a large fluorescence enhancement in buffers,
and were resistant to displacement by Mg2+. The potential of these two dyes to function as reporter molecules was evaluated using continuous fluorescence, DNA helicase
assays. The rate of DNA unwinding was not significantly affected by either of these two dyes. Therefore, Cyan-2 and DM-1 form
the basis for the synthesis of novel cyanine dyes with the potential to overcome the limitations of YOYO-1 and TOTO-1. 相似文献
90.
Gunawidjaja R Peleshanko S Genson KL Tsitsilianis C Tsukruk VV 《Langmuir : the ACS journal of surfaces and colloids》2006,22(14):6168-6176
Star polymers composed of equal numbers of poly(ethylene oxide) (PEO) and polystyrene (PS) arms with variable lengths and a large (up to 38 total) number of arms, PEO(n)PS(n), have been examined for their ability to form domain nanostructures at the air-water and air-solid interfaces. All PEO(n)PS(n) star polymers formed stable Langmuir-Blodgett (LB) monolayers transferable to a solid substrate. A range of nanoscale surface morphologies have been observed, ranging from cylindrical to circular domains to bicontinuous structures as the weight fraction of the PEO block varied from 19% to 88% and n from 8 to 19. For the PS-rich stars and at elevated surface pressure, a two-dimensional supramolecular netlike nanostructure was formed. In contrast, in the PEO-rich star polymer with the highest PEO content, we observed peculiar dendritic superstructures caused by intramolecular segregation of nonspherical core-shell micellar structures. On the basis of Langmuir isotherms and observed monolayer morphologies, three different models of possible surface behavior of the star polymers at the interfaces were proposed. 相似文献