全文获取类型
收费全文 | 139篇 |
免费 | 8篇 |
专业分类
化学 | 117篇 |
晶体学 | 1篇 |
力学 | 4篇 |
物理学 | 25篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 11篇 |
2013年 | 13篇 |
2012年 | 7篇 |
2011年 | 12篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 9篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有147条查询结果,搜索用时 265 毫秒
71.
A short synthesis of hydroxyethylene dipeptide isostere, a core unit of the HIV-protease inhibitors ritonavir and lopinavir, its C-3 epimer and C2 symmetric diamino diol is described. The crucial aspects of the synthesis are self-cross metathesis and exploitation of C2-symmetric of the metathesis product 8 to obtain the required skeleton. 相似文献
72.
Rubel Chakravarty Rakesh Shukla Ramu Ram Avesh Kumar Tyagi Ashutosh Dash Meera Venkatesh 《Chromatographia》2010,72(9-10):875-884
The feasibility of using tetragonal nano-zirconia (t-ZrO2) as an effective sorbent for developing a 99Mo/99mTc chromatographic generator was demonstrated. The structural characteristics of the sorbent matrix were investigated by different analytical techniques such as XRD, BET surface area analysis, FT-IR, TEM etc. The material synthesized was nanocrystalline, in tetragonal phase with an average particle size of ~7 nm and a large surface area of 340 m2 g?1. The equilibrium sorption capacity of t-ZrO2 is >250 mg Mo g?1. The present study indicates that 99Mo is both strongly and selectively retained by t-ZrO2 at acidic pH and 99mTc could be readily eluted from it, using 0.9% NaCl solution. A 9.25 GBq (250 mCi) t-ZrO2 based chromatographic 99Mo/99mTc generator was developed and its performance was repeatedly evaluated for 10 days. 99mTc could be eluted with >85% yield having acceptable radionuclidic, radiochemical and chemical purity for clinical applications. The compatibility of the product in the preparation of 99mTc labeled formulations such as 99mTc-EC and 99mTc-DMSA was evaluated and found to be satisfactory. 相似文献
73.
An efficient one-pot synthesis of polyhydroquinolines by four-component coupling reactions of aldehydes, ethyl acetoacetate, dimedone and ammonium acetate in the presence of HY-zeolite at ambient temperature has been achieved. The conversions took shorter times to form the products in excellent yields. HY-zeolite can be recovered and reused. 相似文献
74.
Ahmed Kamal R. Ramu Mohd. Ameruddin Azhar G.B. Ramesh Khanna 《Tetrahedron letters》2005,46(15):2675-2677
Copper(II) tetrafluoroborate catalyzes efficiently the selective opening of epoxides by amines leading to the synthesis of β-amino alcohols. The reaction works well with aromatic and aliphatic amines in high yields under solvent-free conditions. 相似文献
75.
Ring-opening of aziridines with potassium thiocyanate and thiols has efficiently been carried out at room temperature in the presence of sulfated zirconia to give the corresponding β-aminothiocyanates and β-aminosulfides, respectively, in high yields within 2 h and with high regioselectivity. The catalyst, a solid acid, functions under heterogeneous conditions. 相似文献
76.
Biswanath Das Joydeep BanerjeeR. Ramu Rammohan PalN. Ravindranath C. Ramesh 《Tetrahedron letters》2003,44(29):5465-5468
Aromatic acetates were selectively deprotected in the presence of aliphatic acetates to the corresponding phenols in excellent yields using Amberlyst-15 or iodine as catalysts in methanol at room temperature. The first catalyst can be recovered. 相似文献
77.
Ramu Rajasekaran Prakash Rao Aruna Dornadula Koteeswaran Loganathan Padmanabhan Kulandaivel Muthuvelu Ram Rathan Rai Palraj Thamilkumar Chilakapati Murali Krishna Singaravelu Ganesan 《Photochemistry and photobiology》2013,89(2):483-491
Urine is one of the diagnostically important bio fluids, as it has different metabolites in it, where many of them are native fluorophores. Native fluorescence characteristics of human urine samples were studied using excitation–emission matrices (EEMs) over a range of excitation and emission wavelengths, and emission spectra at 405 nm excitation, to discriminate patients with cancer from the normal subjects. The fluorescence spectra of urine samples of cancer patients exhibit considerable spectral differences in both EEMs and emission spectra with respect to normal subjects. Different ratios were calculated using the fluorescence intensity values of the emission spectra and they were used as input variables for a multiple linear discriminant analysis across different groups. The discriminant analysis classifies 94.7% of the original grouped cases and 94.1% of the cross‐validated grouped cases correctly. Based on the fluorescence emission characteristics of urine and statistical analysis, it may be concluded that the fluorophores nicotinamide adenine dinucleotide (NADH) and flavins may be considered as metabolomic markers of cancer. 相似文献
78.
In this study, a fluorescent material, 2‐naphthyl‐4‐amino benzoate, is synthesized by the esterification of 4‐aminobenzoic acid with 2‐naphthol. This molecule is used in the bulk polymerization of aniline, which results in the formation of poly(aniline‐2‐naphthyl‐4‐aminobenzoate). For comparison, polyaniline and also poly(aniline‐4‐aminobenzoic acid) salts are prepared via bulk polymerization. Formation and properties of these polymeric materials are evaluated by Fourier‐transform infrared (FT‐IR), 13C nuclear magnetic resonance, matrix‐assisted laser desorption ionization, UV‐Vis, Fluorescence, X‐ray diffraction (XRD), Field emission‐scanning electron microscopy (FE‐SEM), Differential scanning calorimetry (DSC), thermogravimetric analysis, electrical resistance and electrochemical techniques. P(ANI‐2NA4ABA) is obtained in nanofiber morphology in 106 wt% yield with respect to the amount of aniline used with comparable conductivity of conventional polyaniline salts. This polymer salt is stable up to 220°C and indicates melting at 146°C on heating and crystal formation at 128°C on cooling. This polymer shows higher wavelength fluorescence compared to the conventional polyaniline salts. This polymer is used as an electrode material without binder, which shows a specific capacitance of 360 F g?1 at 0.25 A g?1. 相似文献
79.
80.
Naidu Sagi V Karri P Hu F Krishnamurthy R 《Angewandte Chemie (International ed. in English)》2011,50(35):8127-8130
Jack of all trades: Water-soluble salts of DHF underwent self-condensation to afford the threo diastereomer of pentulosonic acid, through differing reaction pathways contingent on the metal salt used. This transformation exemplifies the diverging roles of DHF as a nucleophile (a synthon for α-hydroxyacetyl anion) and an electrophile (an α-carboxyglycolaldehyde equivalent). 相似文献