全文获取类型
收费全文 | 333篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
化学 | 224篇 |
力学 | 4篇 |
数学 | 34篇 |
物理学 | 82篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 10篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 14篇 |
2015年 | 8篇 |
2014年 | 13篇 |
2013年 | 36篇 |
2012年 | 32篇 |
2011年 | 33篇 |
2010年 | 13篇 |
2009年 | 17篇 |
2008年 | 19篇 |
2007年 | 22篇 |
2006年 | 11篇 |
2005年 | 15篇 |
2004年 | 13篇 |
2003年 | 8篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有344条查询结果,搜索用时 31 毫秒
81.
Bahram Ghalami-Choobar Vahid Mahdavi Shadfar Pourpanah 《Journal of solution chemistry》2012,41(1):89-99
In this work mean activity coefficient measurements for KCl in the KCl + formamide + water system, using the potentiometric
method, are reported. The electromotive force measurements were performed on a galvanic cell of the type Ag | AgCl | KCl (m), formamide (w%), H2O (1−w)% | K-ISE, in solvent mixtures containing w=(0,10,20,30, and 40)% mass percent of formamide over ionic strengths ranging from 0.0010 to 3.9578 mol⋅kg−1. Modeling of the activity coefficients of this ternary system was based on an extended Debye–Hückel equation and the Pitzer
ion-interaction model. The resulting values of the mean activity coefficients, the osmotic coefficients and the excess Gibbs
energy, together with Pitzer ion-interaction parameters (β
(0), β
(1) and C
ϕ
) and Debye–Hückel parameters (a, c and d), are reported for the investigated system. 相似文献
82.
83.
The interactions of two organoplatinum complexes, [Pt(C^N)Cl(dppa)], 1, and [Pt(C^N)Cl(dppm)], 2 (C^N = N(1), C(2')-chelated, deprotonated 2-phenylpyridine, dppa = bis(diphenylphosphino)amine, dppm = bis(diphenylphosphino)methane), as antitumor agents, with bovine serum albumin (BSA) and human serum albumin (HSA) have been studied by fluorescence and UV-vis absorption spectroscopic techniques at pH 7.40. The quenching constants and binding parameters (binding constants and number of binding sites) were determined by fluorescence quenching method. The obtained results revealed that there is a strong binding interaction between the ligands and proteins. The calculated thermodynamic parameters (ΔG, ΔH, and ΔS) confirmed that the binding reaction is mainly entropy-driven, and hydrophobic forces played a major role in the reaction. The displacement experiment shows that these Pt complexes can bind to the subdomain IIA (site I) of albumin. Moreover, synchronous fluorescence spectroscopy studies revealed some changes in the local polarity around the tryptophan residues. Finally, the distance, r, between donor (serum albumin) and acceptor (Pt complexes) was obtained according to F?rster theory of nonradiation energy transfer. 相似文献
84.
Mehrpooya Mehdi Tabatabaei Seyyed Hessamoddin Pourfayaz Fathollah Ghorbani Bahram 《Journal of Thermal Analysis and Calorimetry》2021,145(5):2547-2569
Journal of Thermal Analysis and Calorimetry - Solar thermochemical reactors have been considered in recent studies because of converting the solar energy to a fuel, which is called solar fuel. In... 相似文献
85.
86.
In this work, the onset of asphaltene flocculation for an Iranian crude oil by titration of samples with heptane in the presence and absence of the TiO2/SiO2 nanofluids was obtained by Near-IR spectroscopy. Nanoparticles and nanocomposites were characterized by BET, FESEM, EDX, XRD, and XRF analysis. Modeling and optimization of inhibition of asphaltene flocculation process by TiO2/SiO2 nanofluids were conducted by response surface methodology (RSM). Under optimum conditions (nanocomposite composition = 0.04 wt% (80%TiO2:20%SiO2), salinity = 4.01 wt%, and pH = 3.42), the onset point increased. For nanofluids stability analysis, the optimum nanofluid was compared with the two other nanofluids (SiO2 and TiO2) by visual observation method. The results indicated that high stability and surface area of the 80%TiO2 nanocomposites increase asphaltene adsorption on the particles surface that subsequently increases the onset point. In addition, the optimum nanofluid performance on the carbonate rocks was evaluated by contact angle and core flooding experiments. The 80% TiO2 nanofluid changed the wettability of carbonate rocks from strongly oil-wet to strongly water-wet condition and also decreased the residual oil saturation and enhanced the oil recovery with an increase in the recovery factor of about 15%. 相似文献
87.
Bahram Hasani Abbasali Zamani Mahdieh Koorepazan Moftakhar Maryam Mostafavi Mohammad Reza Yaftian Massomeh Ghorbanloo 《Journal of Analytical Chemistry》2018,73(1):82-90
Bis(2-hydroxybenzaldehyde)-1,2-diaminoethane (LI), bis(2-hydroxybenzaldehyde)-1,3-diaminopropane (LII) and bis(2-hydroxybenzaldehyde)-4,4'-methylendianiline (LIII) were examined as ionophores for fabrication of polyvinylchloride (PVC) membrane Cu(II) ion-selective potentiometric sensors. The optimum composition (%) for the sensors was: 5 LI, 30 PVC, 6 sodium tetraphenylborate (NaTPB), 59 ortho-nitrophenyloctyl ether (NPOE); 4 LII, 30 PVC, 5 NaTPB, 61 dibutyl phthalate; 6 LIII, 30 PVC, 5 NaTPB, 59 NPOE. The linear response range of the electrodes was 5 × 10–4–0.05 (LI), 5 × 10–4–0.1 (LII) and 1 × 10–6–0.01 M (LIII), and the corresponding detection limits were 4 × 10–4, 4 × 10–4 and 2 × 10–7 M, respectively. The sensors were showed rapid response time (≈10 s). Their responses were independent on pH in the range 2.5–5.0 (LI), 3.2–4.7 (LII) and 4.0–5.0 (LIII). The selectivity of the prepared electrodes towards copper ions over some mono-, di- and trivalent metal ions was evaluated. The sensors were used as indicator electrode in potentiometric titration of copper ions in aqueous solutions. 相似文献
88.
Parisa Izadiyan Bahram Hemmateenejad S. Mohsen Taghavi Mahsa Izadiyan 《Journal of the Iranian Chemical Society》2018,15(2):259-268
Local names are not reliable sources for identification of plants, because they differ significantly from one region to another. Apart from confusing nomenclature, the similar appearance and fragrance of Shirazi thyme and Thymus species cause misidentification. In order to prevent the adverse events in relation to the use of improper herbal products, easy-to-use quality control (QC) methodology was developed to classify these culinary plants. Fourier transform infrared (FT-IR) fingerprinting technique was applied for classification of these plants on the basis of their biochemical compositions. Powerful PLS-DA classification model with classification accuracy of 100% was obtained. For the first time in the present study, it was revealed that Shirazi thyme samples have higher antioxidant activity [average IC50 of 37.03 (µg/ml)] compared to different Thymus species [average IC50 of 148.35 (µg/ml)]. FT-IR fingerprint profiles were also used to construct a predictive model for antioxidant activity of the plants based on a reliable PLSR model. The developed PLSR model revealed that IR wavenumbers of 1000–1200, 1700, and 3200–3500 cm?1 are important for antioxidant activity prediction of the analyzed plants. The applied approach has the potential for being used in QC programs not only for fraud mitigation and detection, but also for estimation of antioxidant activity of the culinary plants. 相似文献
89.
In this paper a new and very simple method was developed for the simultaneous determination of binary and ternary mixtures, without prior separation steps. This method is based on the mean centering of ratio spectra. The mathematical explanation of the procedure is illustrated. After modeling procedure, the method has been successfully applied to the simultaneous analysis of binary mixtures of mefnamic acid and paracetamol and ternary mixtures of acetylsalysilic acid, ascorbic acid and paracetamol. The analytical characteristics of the method such as detection limit, accuracy, precision, relative standard deviation (R.S.D.) and relative standard error (R.S.E.) was calculated. The results showed that the proposed method is simple, rapid, accurate and precise method for analysis of binary and ternary mixtures. 相似文献
90.
Hemmateenejad B Akhond M Miri R Shamsipur M 《Journal of chemical information and computer sciences》2003,43(4):1328-1334