全文获取类型
收费全文 | 355篇 |
免费 | 6篇 |
专业分类
化学 | 307篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 15篇 |
物理学 | 34篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 18篇 |
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 15篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 36篇 |
2012年 | 17篇 |
2011年 | 21篇 |
2010年 | 15篇 |
2009年 | 13篇 |
2008年 | 13篇 |
2007年 | 19篇 |
2006年 | 18篇 |
2005年 | 11篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 9篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有361条查询结果,搜索用时 15 毫秒
351.
Yulia M. Sadykova Larisa M. Sadikova Alena V. Zalaltdinova Yulia K. Voronina Alexander R. Burilov Michael A. Pudovik 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):705-710
AbstractThe reaction of 4-chloro- and 4-bromoresorcinol with 2-ethoxyvinylphosphonic acid dichloroanhydride has been investigated for the first time. It has been determined that the product of the reaction is the mixture of structural isomers of bicyclic phosphonates at the ratio of 9:1. The structure and composition of the compounds have been elucidated from 1H, 31P, and 13C NMR spectroscopy, mass-spectrometry (MALDI-TOF), as well as elemental and X-ray analysis. 相似文献
352.
The inner walls of fused silica micro-capillaries were successfully coated with polyaniline nanofibres using the “grafting” approach. The optical response of polyaniline coatings was evaluated during the subsequent redoping–dedoping processes with hydrochloric acid and ammonia solutions, respectively, that were passed inside the micro-capillary in continuous flow. The optical absorbance of the polyaniline coatings was measured and analysed in the wavelength interval of [300–850 nm] to determine its optical sensitivity to different concentrations of ammonia. It was found that the optical properties of polyaniline coatings change in response to ammonia solutions in a wide concentration range from 0.2 ppm to 2000 ppm. The polyaniline coatings employed as a sensing material for the optical detection of aqueous ammonia have a fast response time and a fast regeneration time of less than 5 s at room temperature. The coating was fully characterised by scanning electron microscopy, Raman spectroscopy, absorbance measurements and kinetic studies. The response of the coatings showed very good reproducibility, demonstrating that this platform can be used for the development of micro-capillary integrated sensors based on the inherited sensing properties of polyaniline. 相似文献
353.
Larisa Calu Mihaela Badea Denisa Falcescu Daria Duca Dana Marinescu Rodica Olar 《Journal of Thermal Analysis and Calorimetry》2013,111(3):1725-1730
In order to develop new metallo-antimicrobials the complexes of type MLCl·nH2O ((1) M: Co, n = 0; (2) M: Ni, n = 2; (3) M: Cu, n = 2.5; (4) M: Zn, n = 0, HL: Schiff base derived from acetylacetone and 3-amino-4H-1,2,4-triazole) were synthesized by template condensation. The features of complexes have been assigned from microanalytical, IR and UV–Vis-NIR data. The species heating in air evidenced processes as melting, water and hydrochloride endothermic elimination as well as oxidative degradation of the Schiff base. The temperature ranges as well as modification in the electronic spectra of dehydrated intermediates indicate the presence of both coordination and crystallisation water molecules. The final product of decomposition was the most stable metal oxide as powder X-ray diffraction indicated. 相似文献
354.
Alexander M. Wasserman Mikhail V. Motyakin Larisa L. Yasina Yulia A. Zakharova Vladimir N. Matveenko Yulia V. Shulevich Lidia Z. Rogovina 《Applied magnetic resonance》2010,38(1):117-135
Molecular dynamics, structure, and phase state of two new micellar systems were investigated using spin-probe electron paramagnetic
resonance spectroscopy. While the local mobility of the new cationic long-chain detergents varies in micelles in a minor way
when the length of a chain increases from 16 to 22 carbon atoms, the order parameter increases noticeably. The latter is caused
by gain of hydrophobic interactions. It is worthwhile to note that the incorporation of the two hydroxyl groups into the polar
head group of the C22 detergent influences particularly on the molecular dynamics and phase state of an aqueous solution of
the detergent. Furthermore, not only the local mobility decreases and ordering factor increases, but also the phase state
of the system changes, being transited from the solid to the micellar (liquid) state. Addition of the KCl salt in an aqueous
solution of the long-chain detergents results in a decrease of local mobility and increase of ordering factor. The phase transitions
are found to be caused by the addition of the salt. The cationic monomer [2-(methacryloyloxy)ethyl]trimethylammonium methyl
sulfate was shown to decrease the critical concentration of micelle formation of the anionic detergent sodium dodecyl sulfate
(SDS). Most likely this is because, being the counterion, the cationic monomer forms a dense layer around the SDS micelle.
Binding of SDS micelle with the monomer strongly reduces the local mobility of the detergent. 相似文献
355.
Alexander D. Milov Rimma I. Samoilova Alexander A. Shubin Elena Yu. Gorbunova Larisa G. Mustaeva Tatyana V. Ovchinnikova Jan Raap Yuri D. Tsvetkov 《Applied magnetic resonance》2010,38(1):75-84
The ion channel-forming peptide antibiotic zervamicin A was studied in egg phosphocholin lipid membranes of large multilamellar
vesicles (LMV) at 77 K. Continuous wave electron paramagnetic resonance (EPR) and electron spin echo envelope modulation (ESEEM)
methods combined with site-specific electron spin labeling were used to study the aggregation and immersion depth of two analog
molecules, i.e., each monolabeled either at the N- or C-terminal end of the helical molecule. Analysis of the shape of the
EPR spectra indicates that zervamicin molecules form aggregates in which the dipolar interaction between the spin labels at
the N-terminus is substantially larger than that between the labels at the C-terminus. The ESEEM method was used to study
the interaction between the nitroxide radical spin labels of the zervamicin molecules and deuterium nuclei in LMV, which were
prepared using a D2O buffer. It is established that the largest amplitude of deuterium modulation of the unpaired electron is observed for zervamicin
molecules labeled at the N-terminus. Based on the analysis of the Fourier parameters of the deuterium modulated spectrum,
a model of the immersion depth of the terminal ends of the zervamicin molecule in a lipid bilayer is formulated. All of the
spin labels at the N-terminus are grouped at the lipid–water interface, whereas 60% of labels at the C-terminus are located
at the lipid–water interface and 40% are more deeply inserted into the lipid bilayer. 相似文献
356.
Denisa Ioana Voiculescu Diana Larisa Roman Vasile Ostafe Adriana Isvoran 《Molecules (Basel, Switzerland)》2022,27(15)
Difenoconazole is a chemical entity containing two chiral centers and having four stereoisomers: (2R,4R)-, (2R,4S)-, (2S,4R)- and (2S,4S)-difenoconazole, the marketed product containing a mixture of these isomers. Residues of difenoconazole have been identified in many agricultural products and drinking water. A computational approach has been used to evaluate the toxicological effects of the difenoconazole stereoisomers on humans. It integrates predictions of absorption, distribution, metabolism, excretion and toxicity (ADMET) profiles, prediction of metabolism sites, and assessment of the interactions of the difenoconazole stereoisomers with human cytochromes, nuclear receptors and plasma proteins by molecular docking. Several toxicological effects have been identified for all the difenoconazole stereoisomers: high plasma protein binding, inhibition of cytochromes, possible hepatotoxicity, neurotoxicity, mutagenicity, skin sensitization potential, moderate potential to produce endocrine disrupting effects. There were small differences in the predicted probabilities of producing various biological effects between the distinct stereoisomers of difenoconazole. Furthermore, there were significant differences between the interacting energies of the difenoconazole stereoisomers with plasma proteins and human cytochromes, the spectra of the hydrogen bonds and aromatic donor–acceptor interactions being quite distinct. Some distinguishing results have been obtained for the (2S,4S)-difenoconazole: it registered the highest value for clearance, exposed reasonable probabilities to produce cardiotoxicity and carcinogenicity and negatively affected numerous nuclear receptors. 相似文献
357.
Vladislav V. Oreshko Kseniya S. Kovaleva Ekaterina D. Mordvinova Olga I. Yarovaya Yuri V. Gatilov Dmitry N. Shcherbakov Nikolai I. Bormotov Olga A. Serova Larisa N. Shishkina Nariman F. Salakhutdinov 《Molecules (Basel, Switzerland)》2022,27(15)
A set of heterocyclic products was synthesized from natural (+)-camphor and semi-synthetic (−)-camphor. Then, 2-Imino-4-thiazolidinones and 2,3-dihydrothiazoles were obtained using a three-step procedure. For the synthesized compounds, their antiviral activity against the vaccinia virus and Marburg virus was studied. New promising agents active against both viruses were found among the tested compounds. 相似文献
358.
Galina A. Oleinik Vladimir V. Koval Svetlana V. Usova Larisa N. Shishkina Alexander A. Chernonosov 《Molecules (Basel, Switzerland)》2022,27(11)
The aim of this work was to develop and validate a sensitive and robust method of liquid chromatography coupled with tandem mass spectrometry to quantitate ST-246 (tecovirimat) in plasma using an internal standard (2-hydroxy-N-{3,5-dioxo-4-azatetracyclo [5.3.2.02.6.08.10]dodec-11-en-4-yl}-5-methylbenzamide). The method was validated in negative multiple reaction monitoring mode following recommendations of the European Medicines Agency for the validation of bioanalytical methods. The calibration curve for the analyte was linear in the 10–2500 ng/mL range with determination coefficient R2 > 0.99. Intra- and inter-day accuracy and precision for three concentrations of quality control were <15%. Testing of long-term stability of ST-246 (tecovirimat) in plasma showed no degradation at −20 °C for at least 3 months. The method was applied to a clinical assay of a new antipoxvirus compound, NIOCH-14. Thus, the proposed method is suitable for therapeutic drug monitoring of ST-246 (tecovirimat) itself and of NIOCH-14 as its metabolic precursor. 相似文献
359.
Vladimir A. Bershtein Larisa M. Egorova Valery A. Ryzhov Pavel N. Yakushev 《Macromolecular Symposia》2000,149(1):87-92
Differential scanning calorimetry (DSC) and laser‐interferometric creep rate spectroscopy (CRS) were used for kinetic and discrete analysis of segmental motion within (and close to) glass transition range in polystyrene ‐ poly(α‐methyl styrene) (PS/PMS) and polystyrene ‐ poly(vinyl methyl ether) (PS/PVME) miscible blends. Two kinds of segmental dynamics heterogeneity were found. Separate ‘unfreezing’ of PS and PMS segmental motions was observed that manifested itself in two Tgs and simultaneous large drop in the Tg s, as well as glass transition activation energy, motional event scale and cooperativity degree values, down to the β‐relaxation parameters. The wide activation energy dispersion within a single broad glass transition in PS/PVME blends was found, and this relaxation region was subdivided, by CRS, into several predicted kinds of segmental motion. Both results are treated in the framework of the concept of common segmental nature of α‐ and β‐relaxations in flexible chain polymers. 相似文献
360.
Alain Deffieux Larisa Shcheglova Anna Barabanova Jean Marc Maréchal Stephane Carlotti 《Macromolecular Symposia》2004,215(1):17-28
The influence of MgR2 and AlR3 additives on alkyllithium initiators in the anionic polymerization of butadiene has been investigated in non polar solvents. A strong decrease of the diene polymerization rate in the presence of the two Lewis acids was observed, similarly to that observed in the retarded anionic polymerisation of styrene. With n,s-Bu2Mg, the percentage of 1,2 vinyl units increases with the [Mg]/[Li] ratio. This behavior is specific to magnesium derivatives bearing secondary alkyl groups and likely results from the additional complexation of lithium species by free dialkylmagnesium and/or a 1,4- to 1,2- chain end isomerization process during chain exchanges between polybutadienyl active chains and dormant ones attached to magnesium species. These reversible exchanges also lead to the formation of one supplementary chain by initial dialkyl magnesium which acts as reversible chain transfer agent. On the contrary with the R3Al/RLi systems the number of chains is only determined by the concentration of initial alkyllithium and no modification of the polybutadiene microstructure compared to lithium initiators (1,4 units = 80%) is noticed. Dialkyl magnesiate complexes with alkali metal derivatives (i.e. alkoxide) are also able to influence the stereochemistry of the styrene insertion during the propagation reaction. Polystyrenes with different tacticities ranging from predominantly isotactic (85% triad iso) to syndiotactic (80% triad syndio) can be obtained with these initiators. 相似文献