全文获取类型
收费全文 | 498篇 |
免费 | 32篇 |
国内免费 | 2篇 |
专业分类
化学 | 472篇 |
晶体学 | 3篇 |
力学 | 4篇 |
数学 | 21篇 |
物理学 | 32篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 13篇 |
2021年 | 31篇 |
2020年 | 24篇 |
2019年 | 41篇 |
2018年 | 32篇 |
2017年 | 21篇 |
2016年 | 34篇 |
2015年 | 23篇 |
2014年 | 31篇 |
2013年 | 28篇 |
2012年 | 44篇 |
2011年 | 40篇 |
2010年 | 30篇 |
2009年 | 21篇 |
2008年 | 21篇 |
2007年 | 26篇 |
2006年 | 14篇 |
2005年 | 19篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
排序方式: 共有532条查询结果,搜索用时 796 毫秒
31.
Denis N. Bazhin Dmitry L. Chizhov Gerd-Volker Röschenthaler Yulia S. Kudyakova Yanina V. Burgart Pavel A. Slepukhin Victor I. Saloutin Valery N. Charushin 《Tetrahedron letters》2014
1,1,1-Trifluoro-4,5,5-trimethoxyhex-3-en-2-one and lithium (2Z)-1,1,1-trifluoro-5,5-dialkoxy-4-oxohex-2-en-2-olate were synthesized for the first time via direct trifluoroacetylation of 2,3-butanedione acetal derivatives. A simple and effective approach to acetal or acyl substituted CF3-pyrazoles, 5,5′-bis(trifluoromethyl)-3,3′-bipyrazole, and, to 5-trifluoromethylfuran-3-ones is presented. 相似文献
32.
Mandy Eibisch Yulia Popkova Rosmarie Süß Jürgen Schiller Dirk Dannenberger 《Analytical and bioanalytical chemistry》2014,406(28):7401-7405
The quantitative determination of the total free fatty acids (FFAs) is an important analytical task because FFAs exhibit important physiological effects and are also relevant in many other fields, for instance, in food research. Our aim was to investigate whether a commercially available enzymatic test kit developed for the determination of FFAs in human serum is also suitable to determine different physiological and nonphysiological FFAs and to which extent the impact on the sensitivities (i.e., the accuracy by which a given FFA can be determined) differ. It will be shown that the chain length as well as the double bond content has a significant impact on the sensitivity by which a given FFA can be determined. For instance, palmitic acid (16:0) is determined with an approximately 20 times higher sensitivity in comparison to docosahexaenoic acid (22:6n-3). All data were obtained by measuring the concentrations of the FFAs by gas chromatography, and selected FFAs were also determined in a complex matrix of human serum. It is concluded that this kit is not useful if major alterations of the FFA composition of a complex mixture are expected because the individual FFAs are not detected with the same sensitivities: the concentrations of polyunsaturated FFA determined by this kit are wrong. Figure
The used enzymatic kit detects different free fatty acids with significantly different sensitivities: the number of carbon atoms and the number of double bonds massively contribute to these differences 相似文献
33.
Ohorodnik Yulia M. Alexander Sikalov A. Khomenko Dmytro M. Doroshchuk Roman O. Raspertova Ilona V. Shova Sergiu Babak Maria V. Lampeka Rostyslav D. 《Transition Metal Chemistry》2022,47(6):213-221
Transition Metal Chemistry - The structures of new p-cymene Ru(II) complexes with 2-(1-methyl-1H-1,2,4-triazol-3-yl)pyridine and 2-(1-methyl-1H-1,2,4-triazol-5-yl)pyridine were established based on... 相似文献
34.
Yulia Shulpekova Vladimir Nechaev Svetlana Kardasheva Alla Sedova Anastasia Kurbatova Elena Bueverova Arthur Kopylov Kristina Malsagova Jabulani Clement Dlamini Vladimir Ivashkin 《Molecules (Basel, Switzerland)》2021,26(12)
Folates have a pterine core structure and high metabolic activity due to their ability to accept electrons and react with O-, S-, N-, C-bounds. Folates play a role as cofactors in essential one-carbon pathways donating methyl-groups to choline phospholipids, creatine, epinephrine, DNA. Compounds similar to folates are ubiquitous and have been found in different animals, plants, and microorganisms. Folates enter the body from the diet and are also synthesized by intestinal bacteria with consequent adsorption from the colon. Three types of folate and antifolate cellular transporters have been found, differing in tissue localization, substrate affinity, type of transferring, and optimal pH for function. Laboratory criteria of folate deficiency are accepted by WHO. Severe folate deficiencies, manifesting in early life, are seen in hereditary folate malabsorption and cerebral folate deficiency. Acquired folate deficiency is quite common and is associated with poor diet and malabsorption, alcohol consumption, obesity, and kidney failure. Given the observational data that folates have a protective effect against neural tube defects, ischemic events, and cancer, food folic acid fortification was introduced in many countries. However, high physiological folate concentrations and folate overload may increase the risk of impaired brain development in embryogenesis and possess a growth advantage for precancerous altered cells. 相似文献
35.
Dmitriy S. Yambulatov Stanislav A. Nikolaevskii Mikhail A. Kiskin Kirill V. Kholin Mikhail N. Khrizanforov Yulia G. Budnikova Konstantin A. Babeshkin Nikolay N. Efimov Alexander S. Goloveshkin Vladimir K. Imshennik Yurii V. Maksimov Evgeny M. Kadilenko Nina P. Gritsan Igor L. Eremenko 《Molecules (Basel, Switzerland)》2021,26(10)
The reaction of the redox active 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-BIAN) and iron(II) iodide in acetonitrile led to a new complex [(dpp-BIAN)FeIII2] (1). Molecular structure of 1 was determined by the single crystal X-ray diffraction analysis. The spin state of the iron cation in complex 1 at room temperature and the magnetic behavior of 1 in the temperature range of 2–300 K were studied using Mossbauer spectroscopy and magnetic susceptibility measurements, respectively. The neutral character of dpp-BIAN in 1 was confirmed by IR and UV spectroscopy. The electrochemistry of 1 was studied in solution and solid state using cyclic voltammetry. The generation of the radical anion form of the dpp-BIAN ligand upon reduction of 1 in a CH2Cl2 solution was monitored by EPR spectroscopy. 相似文献
36.
Diana V. Aleksanyan Yulia V. Nelyubina Zinaida S. Klemenkova Vladimir A. Kozlov 《Phosphorus, sulfur, and silicon and the related elements》2014,189(7-8):1028-1042
AbstractNovel phosphorus-containing ligands have been synthesized by the condensation of 2-(thio)phosphorylated anilines with 2,6-dichloro- and 4-chloropyridine-2-carbonyl chlorides in the presence of Et3N and unsubstituted pyridine-2-carboxylic acid using P(OPh)3 as a coupling agent. The compounds derived readily form complexes with a range of transition metals (M=Re(I), Pd(II), and Cu(II)), serving as bi- or tridentate monoanionic ligands. The composition and structure of the resulting metallocycles depend both on the presence/amount of the Cl atoms in the pyridine ring and on the nature of the donor atom X in the P=X moiety. The novel compounds were characterized by multinuclear NMR and IR spectroscopy as well as X-ray crystallography. 相似文献
37.
Marcos V. Foguel Angelica M. Balcarcel Mark A. Reed Percy Calvo‐Marzal Yulia V. Gerasimova Dmitry M. Kolpashchikov Karin Y. Chumbimuni‐Torres 《Electroanalysis》2020,32(4):835-841
One major challenge in nucleic acids analysis by hybridization probes is a compromise between the probe's tight binding and sequence‐selective recognition of nucleic acid targets folded into stable secondary structures. We have been developing a four‐way junction (4WJ)‐based sensor that consists of a universal stem‐loop (USL) probe immobilized on an electrode surface and two adaptor strands (M and F). The sensor was shown to be highly selective towards single base mismatches at room temperature, able to detect multiple targets using the same USL probe, and have improved ability to detect folded nucleic acids. However, some nucleic acid targets, including natural RNA, are folded into very stable secondary and tertiary structures, which may represent a challenge even for the 4WJ sensors. This work describes a new sensor, named MVF since it uses three probe stands M, V and F, which further improves the performance of 4WJ sensors with folded targets. The MVF sensor interrogating a 16S rRNA NASBA amplicon with calculated folding energy of ?32.82 kcal/mol has demonstrated 2.5‐fold improvement in a signal‐to‐background ratio in comparison with a 4WJ sensor lacking strand V. The proposed design can be used as a general strategy in the analysis of folded nucleic acids including natural RNA. 相似文献
38.
Ganeeva Yulia M. Yusupova Tatiana N. Okhotnikova Ekaterina S. 《Journal of Thermal Analysis and Calorimetry》2020,139(1):273-278
Journal of Thermal Analysis and Calorimetry - The bitumen-containing reservoir rocks taken from Devonian terrigenous formation of Romashkino and Bavly oil fields (Russia) were sampled and... 相似文献
39.
Veselov Mark S. Ivanenkov Yan A. Yamidanov Renat S. Osterman Ilya A. Sergiev Petr V. Aladinskiy Vladimir A. Aladinskaya Anastasia V. Terentiev Victor A. Ayginin Andrey A. Skvortsov Dmitry A. Komarova Katerina S. Chemeris Alexey V. Baimiev Alexey Kh. Sofronova Alina A. Machulkin Alexey E. Petrov Rostislav A. Maklakova Svetlana Yu. Bezrukov Dmitry S. Filkov Gleb I. Zainullina Liana F. Maximova Marina A. Zileeva Zulfiya R. Kartsev Victor G. Vakhitova Yulia V. Dontsova Olga A. 《Molecular diversity》2020,24(1):233-239
Molecular Diversity - A series of 5-oxo-4H-pyrrolo[3,2-b]pyridine derivatives was identified as novel class of highly potent antibacterial agents during an extensive large-scale high-throughput... 相似文献
40.
Yulia Shenberger Ortal Marciano Hugo E. Gottlieb 《Journal of Coordination Chemistry》2018,71(11-13):1985-2002
AbstractCopper transporter 1 (CTR1) is the main copper transporter in the eukaryotic system. CTR1 has several important roles: It binds Cu(II) ions that are present in the blood; it reduces those Cu(II) ions to Cu(I); and it subsequently transfers Cu(I) to the cytoplasmic domain, where the ion is delivered to various cellular pathways. Here, we seek to identify CTR1 binding sites for Cu(II) and Cu(I) and to shed light on the Cu(II)-to-Cu(I) reduction process. We focus on the first 14 amino acids of CTR1. This N-terminal segment is rich with histidine and methionine residues, which are known to bind Cu(II) and Cu(I), respectively; thus, this region has been suggested to have an important function in recruiting Cu(II) and reducing it to Cu(I). We utilize electron paramagnetic resonance (EPR) spectroscopy together with nuclear magnetic resonance (NMR) and UV-VIS spectroscopy and alanine substitution to reveal Cu(II) and Cu(I) binding sites in the focal 14-amino-acid segment. We show that H5 and H6 directly coordinate to Cu(II), whereas M7, M9, and M12 are involved in Cu(I) binding. This research is another step on the way to a complete understanding of the cellular copper regulation mechanism in humans. 相似文献