全文获取类型
收费全文 | 139篇 |
免费 | 1篇 |
专业分类
化学 | 96篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 21篇 |
物理学 | 20篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 14篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 15篇 |
2012年 | 3篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1962年 | 5篇 |
1961年 | 1篇 |
1957年 | 3篇 |
1956年 | 3篇 |
1954年 | 2篇 |
1902年 | 1篇 |
排序方式: 共有140条查询结果,搜索用时 8 毫秒
61.
Mamdouh A. Hassan Ragab F. Fandy Tark M. El‐Amine 《Journal of heterocyclic chemistry》2001,38(1):179-183
Treatment of 2‐aryl‐3,6‐bis(arylamino)‐1,4‐benzoquinones 2a‐h with different acid chlorides, namely acetyl, phenylacetyl and chloroacetyl chloride yields 3a,7a‐dihydropyrrolo[2,3‐f]indole‐2,6‐dione 3, 5‐(N‐phenylacetylarylamino)‐3‐phenylindole‐2,6‐dione 4 and 3‐chloro‐5‐(N‐chloroacetylarylamino)indole‐2,6‐dione 5 respectively. Stirring 2‐aryl‐1,4‐benzoquinones ( 1 ) with ethylenediamine and/or o‐phenyl‐enediamine in methylene chloride gives pyrazino[2,3‐g]quinoxalines derivative 6 and/or tetrapentacene derivative 7 respectively. The products 5‐aryl‐ and 6‐aryl‐1/H‐indazole‐4,7‐diones 8 and 9 were obtained in the 1,3‐dipolar cycloaddition of diazomethane to ( 1 ). 相似文献
62.
Theodor W. Güntert Horst H. A. Linde Mohamed S. Ragab Sigrid Spengel 《Helvetica chimica acta》1978,61(3):977-983
Synthesis of 4-[3β, 14-Dihydroxy-5β, 14β-androstan-17β-yl]-3-pyrrolin-2-one (hothesimogenin) We describe the synthesis of 4-[3β, 14-Dihydroxy-5β, 14β-androstan-17β-yl]-3-pyrrolin-2-one (24-aza-24-desoxa-digitoxigenin) (7) , starting from 3-O-acetyl-digitoxigenin (1) . 相似文献
63.
Mostafa M. Ghorab Fatma A. Ragab Helmy I. Heiba Walid M. Ghorab 《Journal of heterocyclic chemistry》2011,48(6):1269-1279
Quinoline derivatives posses many types of biological activities and have been reported to show significant anticancer activity. There is a variety of mechanisms for the anticancer activity and the most distinguished mechanism is the inhibition of vascular epithelial growth factor receptor tyrosine kinase (VEGFRTK). Novel quinoline derivatives 6 , 7a , 7b , 7c , 8 , 9 , 10 , 11 , 12 and pyrimido[4,5‐b]quinoline derivatives 16 , 17 , 18 , 19 , 20 are reported herein. All the newly synthesized compounds were evaluated for their in vitro anticancer activity against human breast cancer cell line (MCF7) in which VEGFR is highly expressed. Compounds 6 and 7 with IC50 values of 8.5 μM and 21.9 μM were the most active compounds and exhibited cytotoxic activities higher than that of the reference drug doxorubicin (IC50= 32.02 μM). The most active compounds 6 and 7 were further evaluated for their ability to enhance the cell killing effect of γ‐radiation. J. Heterocyclic Chem., (2011). 相似文献
64.
3‐(Pyrazol‐3‐yl)‐3‐oxo‐propanenitrile derivative reacts with several nitrogen nucleophiles to give bipyrazole, pyrazolyloxazole, and pyrazolylpyrimidine derivatives. The structures of the products were confirmed on the basis of their elemental and spectral analyses. 相似文献
65.
Korany A. Ali Heba S. Abdalghfar Khaled Mahmoud Eman A. Ragab 《Journal of heterocyclic chemistry》2013,50(5):1157-1164
The versatile multifunctional unreported pyridine‐2,6‐bis(2‐cyano‐N‐phenyl‐3‐oxopropanethioamide) ( 3 ) was prepared starting from pyridine‐2,6‐bis‐(3‐oxopropanenitrile) ( 1 ). Several new series of polysubstituted thiophenes and 1,3,4‐thiadiazoles incorporating 2,6‐pyridine moiety were efficiently synthesized. The newly synthesized compounds were evaluated for their in vitro anticancer activity against human cancer cell lines: hepatocellular liver carcinoma (HEPG2) and Caucasian breast adenocarcinoma (MCF‐7). Some of the newly synthesized compounds exhibited better activity than doxorubicin as a reference drug. 相似文献
66.
A Facile Access to Some New Pyrazole, 1,3,4-Thiadiazole,and Thiophene Derivatives via β-Ketosulfones
Kamal M. Dawood Nabila A. Kheder Eman A. Ragab Sanaa N. Mohamed 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):330-339
3-Bromoacetyl-1,5-diphenyl-1H-pyrazole-4-carbonitrile (1) reacts with sodium benzenesulfinate to give the corresponding ketosulfone 2. Treatment of 2 with hydrazonoyl chlorides 3a,b gives the 3,3′-bipyrazoles 5a,b. Ketosulfone 2 reacts also with arylidenemalononitriles to give the pyrazolylpyridones 10a,b. The reaction of compound 2 with phenylisothiocyanate and potassium hydroxide and treating intermediate with hydrazonoyl halides and with α-haloketones gives the 1,3,4-thiadiazoles 18a–c and thiophenes 21a–f, respectively. 相似文献
67.
Korany A. Ali Eman A. Ragab Grzegorz Mlostoń Małgorzata Celeda Anthony Linden Heinz Heimgartner 《Helvetica chimica acta》2013,96(4):633-643
On treatment of 3‐amino‐5‐aryl‐1H‐pyrazoles 1 with dialkyl dicyanofumarates (=(E)‐but‐2‐enedioates) 4 in boiling 1,2‐dichloroethane, two competitive reactions occurred leading to 3‐aryl‐5‐cyano‐6,7‐dihydro‐6‐oxo‐1H‐pyrazolo[3,4‐b]pyridine‐4‐carboxylates 10 and 7‐amino‐2‐arylpyrazolo[1,5‐a]pyrimidine‐5,6‐dicarboxylates 11 . In DMF at room temperature, as well as at 100°, only compounds 10 were isolated. The formation of the major products of type 10 was rationalized via Michael addition of 1 as a C(4)‐nucleophile onto 4 , followed by HCN elimination and lactamization. On the other hand, the minor products 11 result from a Michael addition of 1 onto 4 via the NH2 group, and subsequent HCN elimination and cyclization. The structures of the products have been established by X‐ray crystallography. 相似文献
68.
The spectral and kinetic parameters of transient species generated in the irradiation of 6-ethoxy-2,2,4-trimethyl-8-nitro-1,2-dihydroquinoline
were examined by stationary and pulse photolysis in the solvents: heptane, acetonitrile, methanol, and ethanol. Upon excitation
of the long-wavelength absorption band (λex > 450 nm), a reversible photochemical reaction was revealed, and the spectral and kinetic parameters of three transient species
observed in the photolysis were characterized (λmax = 390, 400, and 420 nm (acetonitrile), k = 97, 500, and 2000 s−1, respectively). The absorption spectra and the rate constants of the decay of transient species are almost independent of
the medium polarity and the presence of oxygen in the system. The excited state generated during irradiation to the short-wavelength
absorption band (290 < λex < 350 nm) is inactive in the photochemical reaction and deactivates without the formation of transient species. The mechanism
of the reversible photochemical reaction is suggested, which involves the opening of the heterocycle N-C bond upon photoexcitation
of the long-wavelength absorption band and the thermal back reaction. 相似文献
69.
70.
F. M. Ragab 《Mathematische Zeitschrift》1962,78(1):222-230
Ohne Zusammenfassung 相似文献