全文获取类型
收费全文 | 118篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 86篇 |
数学 | 21篇 |
物理学 | 18篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 12篇 |
2011年 | 5篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 2篇 |
2006年 | 5篇 |
2005年 | 1篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有125条查询结果,搜索用时 46 毫秒
1.
Summyia Masood Rehana Saeed Maria Ashfaq Afshan Irfan 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(12):2102-2107
Viscosities of sodium chloride in concentration range 1 × 10?2 to 9 × 10?2 ± 0.001 mol dm?3, have been determined in aqueous and aqueous maltose systems (1.0 to 9.0 wt %) at different temperatures (298 to 323 K). The viscosity data have been analyzed by using Jones-Dole equation and the derived parameters A and B coefficients were also calculated. The data obtained from viscometric studies has been used to investigate the ion-solvent interaction and ion-ion interaction. Thermal effects on the ionic interactions were also examined under the light of transition state theory. 相似文献
2.
Nathanael Ackerman Cameron Freer Aleksandra Kwiatkowska Rehana Patel 《Annals of Pure and Applied Logic》2017,168(1):19-36
We consider the space of countable structures with fixed underlying set in a given countable language. We show that the number of ergodic probability measures on this space that are -invariant and concentrated on a single isomorphism class must be zero, or one, or continuum. Further, such an isomorphism class admits a unique -invariant probability measure precisely when the structure is highly homogeneous; by a result of Peter J. Cameron, these are the structures that are interdefinable with one of the five reducts of the rational linear order . 相似文献
3.
The chemical grafting of thiol terminated poly(sodium styrenesulfonate)(HS-PSSS) chains from sodium nitrate (NaNO_3) salt solution to a gold surface was investigated with a quartz crystal microbalance with dissipation monitoring (QCM-D) in different salt concentrations.It was found that at low salt concentration grafting density of HS-PSSS was low and the grafted chains adopted a mushroom conformation.With the increase of salt concentration polyelectrolyte chains underwent a transition toward coiled stat... 相似文献
4.
J.S. Yadav B.V. Subba Reddy G. Madhusudhan Reddy S. Rehana Anjum 《Tetrahedron letters》2009,50(44):6029-5515
Aldehyde, alcohol, azide, and alkyne undergo smooth coupling by means of acetal formation, azidation, and a subsequent ‘click reaction’ in the presence of copper(II) triflate and copper metal in acetonitrile to furnish α-alkoxy-1,2,3-triazoles in good yields. The method provides a convenient route to prepare a wide range of triazoles in a one-pot operation via a four-component reaction. 相似文献
5.
M. Šiljegovi? Z.M. Ka?arevi?-Popovi? N. Bibi? Z.M. Jovanovi? S. Maleti? M. Stchakovsky A.N. Krklješ 《Radiation Physics and Chemistry》2011,80(12):1378-1385
Fluorinated ethylene propylene (FEP) and tetrafluoroethylene–perfluoro(alkoxy vinyl ether) (PFA) copolymer films were irradiated in vacuum with 60 keV C4+ and N4+ ions to fluences ranging from 1.0×1012 to 5.0×1015 cm−2. Changes in optical and dielectric properties were analyzed by spectroscopic ellipsometry and ultraviolet–visible (UV–vis), Raman and dielectric relaxation spectroscopies. Direct and indirect energy band gap values were determined from the absorption edge in the 200–800 nm region using Tauc's relation. The values of the direct energy gap have been found to be greater than the corresponding values of the indirect energy gap. Significant changes in the index of refraction, and β and γ dielectric relaxations were observed in the case of N4+ irradiated FEP and PFA samples. 相似文献
6.
7.
M. Mohammad A. Y. Khan M. S. Subhani N. Bibi Safeer Ahmad Saba Saleemi 《Research on Chemical Intermediates》2001,27(3):259-267
Rate constants for the reaction of superoxide O-
2 with various substrates were obtained through stationary electrode polarography theory and technique. In solvent acetonitrile, the substrate and the rate constants of the reaction O-
2 + AH-
k2Product, are, AH = isopropanol (k2 < 0.01 M-1 s-1); ethanol (k2 = 1.42 × 102 M-1 s-1); methanol (k2 = 1.1 × 107 M-1 s-1), H2O (k2 = 1.0 × 105 M-1 s-1). In MeCN, O-2 was found to be rather unreactive towards glucose and acetone but it reacts with fructose and sucrose catalytically. However, in DMF2, O-
2reacts with glucose and fructose with k2 order of 105 M-1 s-1. The mechanism of the reaction of O-
2 with the substrates (AH) is proposed as O-
3 + AH k2O, AHk2
k-1 k [O2H + AH]-, k-2O2H + A- with k1 = 109 M-1 s-1 and k-1 = 108 -109 s-1. With these values of k-1 and k1, k k2(obs). The reversible E1/2 for O2 + e O-
2 in various solvents: MeCN, acetone, isopropanol, methanol, H2O were obtained either directly from the reversible voltammogram or from experimental voltammograms and the rate constants obtained (as above) using stationary electrode polargraphy theory; E1/2 being -0.82 (MeCN),-0.85 (acetone),-0.72 (isopropanol);-0.66 (MeOH),-0.56 (H2O) vs SCE. 相似文献
8.
The activation of nuclear factor-kappa B1 (NFkB1) in cancer cells may confer resistance to ionizing radiation (IR). To enhance the therapeutic efficiency of IR in lung cancer, we screened for microRNAs (miRNAs) that suppress NFkB1 and observed their effects on radiosensitivity in a human lung cancer cell line. From time series data of miRNA expression in γ-irradiated H1299 human lung cancer cells, we found that the expression of miR-9 was inversely correlated with that of NFκB1. Overexpression of miR-9 down-regulated the level of NFκB1 in H1299 cells, and the surviving fraction of γ-irradiated cells was decreased. Interestingly, let-7g also suppressed the expression of NFκB1, although there was no canonical target site for let-7g in the NFκB1 3' untranslated region. From these results, we conclude that the expression of miR-9 and let-7g could enhance the efficiency of radiotherapy for lung cancer treatment through the inhibition of NFκB1. 相似文献
9.
Zaheer Ahmad Itrat Fatima Sajid Mehmood Rehana Ifzal Abdul Malik Nighat Afza 《Helvetica chimica acta》2008,91(1):73-78
Three new 20,24‐epoxydammarane triterpenes, santolins A–C ( 1 – 3 ), were isolated from the AcOEt‐soluble fraction of the MeOH extract of Salvia santolinifolia (whole plant). Their structures were assigned based on 1H‐NMR, 13C‐NMR (DEPT), and 2D‐NMR analyses, in combination with HR‐MS experiments and comparison with literature data of related compounds. 相似文献
10.
M. A. Salam Md. Azharul Arafath Mouayed A. Hussein Rabeya Basri Rehana Pervin 《Phosphorus, sulfur, and silicon and the related elements》2016,191(8):1101-1107
Four new organotin(IV) complexes with 2-hydroxynaphthaldehyde-N(4)-ethylthiosemicarbazone [(H2DNET), (1)] of the type [MeSnCl(DNET] (2), [BuSnCl(DNET)] (3), [PhSnCl(DNET)] (4), and [Ph2Sn(DNET] (5) have been synthesized by the direct reaction of H2DNET (1) with organotin(IV) chloride(s) in the presence of potassium hydroxide in absolute methanol. All the compounds were characterized by elemental analyses, molar conductivity, UV-Vis, IR, 1H, 13C, and 119Sn NMR spectral studies. The molecular structure of ligand (1) has been confirmed by X-ray single crystal diffraction. Spectroscopic data clearly suggested that Sn(IV) center is coordinated with the ONS tridentate ligand (H2DNET) and exhibits a five-coordinate geometry in solution. Antibacterial studies were carried out in vitro against four bacterial strains. All organotin(IV) compounds (2–5) showed good activity against various bacteria but lower activity than the reference drug (Ciprofloxacin). The results demonstrate that organic groups attached to tin(IV) moiety have significant effect on their biological activities. Among them, diphenyltin(IV) derivative 5 exhibits significantly good activity than the other organotin(IV) derivatives (2–4). 相似文献