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排序方式: 共有78条查询结果,搜索用时 171 毫秒
1.
Erik Larsen Abdel Aleem H. Abdel Aleem Erik B. Pedersen 《Journal of heterocyclic chemistry》1995,32(5):1645-1646
α-Thymidine (4) was synthesized from thymidine (1) in 3 steps in 36% overall yield without using chro-matography and with the possibility of increasing the yield to 85% by reusing the remaining α,β-mixture. 1-(2-Deoxy-3,5-di-O-p-toluoyl-α-D-erythro-pentofuranosyl)thymine (3) was further converted to 1-(2-deoxy-α-D-erythro-pentofuranosyl)-5-methylcytosine (5) . 相似文献
2.
Synthesis and biological activities of tetrahydroquinazoline analogs of aminopterin and methotrexate
Aleem Gangjee Nurulain Zaveri Sherry F. Queener Roy L. Kisliuk 《Journal of heterocyclic chemistry》1995,32(1):243-247
(6R,6S)-5,8-Dideaza-5,6,7,8-tetrahydroaminopterin ( 1 ) and (6R,6S)-5,8-dideaza-5,6,7,8-tetrahydromethotrexate ( 2 ) were synthesized as potential inhibitors of dihydrofolate reductase (DHFR) and as antitumor agents. Cyclohexanone-4-carboxaldehyde dimethyl acetal, a key intermediate [10] was synthesized from cyclohexane-1,4-dione monoethylene ketal, which was converted via a Wittig reaction to its exocyclic 4-methylene derivative which in turn, was converted to the 4-aldehyde via a hydroboration-oxidation sequence. Selective protection of the 4-aldehyde as the dimethylacetal and cyclization with dicyandiamide afforded the 6-dimethylacetal of 2,4-diamino-5,6,7,8-tetrahydroquinazoline. Protection of the 2,4-diamino moieties and selective deprotection of the 6-aldehyde followed by reductive amination with p-aminobenzoyl-L-glutamate afforded 2,4-bisacetamido-5,8-dideaza-5,6,7,8-tetrahydroaminopterin ( 11 ). Deprotection of 11 afforded 1 . Compound 2 was obtained from 11 via N10-methylation and deprotection. The N10-methyl analogue 2 was 2–10 fold more potent than 1 as an inhibitor of various DHFRs. In the in vitro preclinical screening program of the National Cancer Institute, compound 2 inhibited the growth of eighteen of the twenty nine tumor cell lines in culture at a GI50 > 1.0 × 10?8 M. 相似文献
3.
Isaac O. Donkor Rajesh Devraj Sherry F. Queener Louis R. Barrows Aleem Gangjee 《Journal of heterocyclic chemistry》1996,33(6):1653-1661
A series of diaminobenzo[f]- and diaminobenzo[h]pyrimido[4,5-b]quinolines 1–11 were designed as 5-deaza tetracyclic nonclassical, lipophilic antifolates. The compounds were designed as conformationally semi-rigid and rigid analogs of 2,4-diamino-6-phenyl- 12 and 2,4-diamino-7-phenylpyrido[2,3-d]pyrimidines 13 and 14 . The target compounds were synthesized by cyclocondensation of chlorovinyl aldehydes obtained from appropriately substituted 1- or 2-tetralone, with 2,4,6-friaminopyrimidine. Compounds 1–11 were evaluated as inhibitors of P. carinii and T. gondii dihydrofolate reductases. These pathogens cause fatal opportunistic infections in AIDS patients. In addition, the selectivity of these agents was evaluated using rat liver dihydrofolate reductase as the mammalian source. In general the benzo[f]pyrimido[4,5-b]quinolines 1–5 were more potent than the corresponding benzo[h]pyrimido[4,5-b]quinoline analogues 6–11 against P. carinii and rat liver dihydrofolate reductase and were equipotent against T. gondii dihydrofolate reductase. Compounds 6–11 were moderately selective towards T. gondii dihydrofolate reductase with IC50S in the 10−7 M range. In contrast analogues 1–5 lacked selectivity against P. carinii or T. gondii dihydrofolate reductase and were, in general, potent inhibitors of rat liver dihydrofolate reductase with IC50S in the 10−8 M range. Analogues 1 and 4 were evaluated against a series of tumor cell lines in vitro and were found to have moderate antitumor activity (IC50 10−6 M). The structure activity/selectivity relationships suggest that benzo[f]pyrimido analogues 1–5 with the phenyl ring substitution in the “upper” portion of the tetracyclic ring are better accommodated within the rat liver (mammalian) dihydrofolate reductase and P. carinii dihydrofolate reductase active sites compared to the benzo[h]pyrimido analogues 6–11 which have the phenyl ring substitution in the “lower” portion of the tetracyclic ring. In contrast T. gondii dihydrofolate reductase does not discriminate between the isomers and binds to both series of compounds with similar affinities. 相似文献
4.
Aleem Gangjee Kwasi A. Ohemeng Fu-Tyan Lin Arthur A. Katoh 《Journal of heterocyclic chemistry》1986,23(2):523-528
Cyclocondensation of 6-amino-2,4-dioxopyrimidine or 2,4,6-triaminopyrimidine with 1-cyclohexenecarbox-aldehyde 13 afforded regiospecifically, tricyclic, angular 1,3-disubstituted tetrahydropyrimido[4,5-c]isoquin-olines 5 and 6 respectively. In addition, 2,4,6-triaminopyrimidine when condensed with 2-chloro-1-cyclohex-enecarboxaldehyde 14 , regiospecifically afforded the angular isomer 6 . However, the cyclocondensation of 2,6-diamino-4-oxopyrimidine with 13 was regioselective and afforded a mixture of the linear and angular tetrahydropyrimidoisoquinolines 2 and 4 . The growth of leukemia L-1210 cells in culture were inhibited 50% by 6 at 9 × 10?8 M. Compounds 4 and 5 were not significantly active. 相似文献
5.
Synthesis of Novel Modified Guanidines: Reaction of Dicyandiamide with Amino Acids,Amides, and Amines in Aqueous Medium 下载免费PDF全文
Ahmed M. Soliman Shaaban K. Mohamed Mahmoud. Abd El Aleem. Ali. Ali. El‐Remaily H. Abdel‐Ghany 《Journal of heterocyclic chemistry》2014,51(5):1322-1326
Reaction of dicyandiamide with series of amino acids afforded guanidinyl pyrazolones 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , respectively. Although reaction of dicyandiamide with urea, acetamide, bezamide, allantion, p‐aminobenzoic acid, sulphanilic acid, and adenine gave biguanides 20 , 21 , 22 , 23 , 24 , 25 , 26 , respectively. All compounds have been characterized on the basis of IR and 1H‐NMR. 相似文献
6.
Ahmed M. M. Soliman Mahmoud. Abd El‐Aleem. Ali. Ali. El‐Remaily Adel. A. Sultan Hossam. Abdel‐Ghany 《Journal of heterocyclic chemistry》2014,51(5):1476-1481
5‐Amino‐3‐anilino‐1H‐pyrazole‐4‐carbonitrile 1 was alkylated with various halo reagents under phase transfer conditions to give the corresponding imidazopyrazole derivatives 2a , 2b , 2c , 3 , 4 , 5 , 6 . Pyrazolo[1,5‐a] pyrimidine derivatives 11 , 12 , 13 , 14 were prepared by treating compound 1 with different dicarbonyl reagents, namely, diethymalonate, ethyl 3‐oxo‐3‐phenylpropanoate, pentane‐2,4‐dione or ethyl 3‐oxobutanoate. 相似文献
7.
Aleem Syed Michael D. Lesoine Ujjal Bhattacharjee Jacob W. Petrich Emily A. Smith 《Photochemistry and photobiology》2014,90(4):767-772
Time binning is used to increase the number of photon counts in the peak channel of stimulated emission depletion fluorescence lifetime decay curves to determine how it affects the resulting lifetime image. The fluorescence lifetime of the fluorophore, Alexa Fluor 594 phalloidin, bound to F‐actin is probed in cultured S2 cells at a spatial resolution of ~40 nm. This corresponds to a 10‐fold smaller probe volume compared to confocal imaging, and a reduced number of photons contributing to the signal. Pixel‐by‐pixel fluorescence lifetime measurements and error analysis show that an average of 40 ± 30 photon counts in the peak channel with a signal‐to‐noise ratio of 20 is enough to calculate a reliable fluorescence lifetime from a single exponential fluorescence decay. No heterogeneity in the actin cytoskeleton in different regions of the cultured cells was measured in the 40–400 nm spatial regime. 相似文献
8.
Abdul Aleem Jamali Bernd Witzigmann Rodica Morarescu Thomas Baumert Frank Träger Frank Hubenthal 《Applied Physics A: Materials Science & Processing》2013,110(4):743-749
In this contribution we present recent experimental and theoretical results on local near-field assisted laser ablation. Along these lines, we have generated sub-diffraction sized nanostructures on fused silica substrates, exploiting the local near fields of highly ordered triangular gold nanoparticle arrays generated by nanosphere lithography. After preparation, the nanoparticle arrays were irradiated with a single 35 fs long laser pulse with a central wavelength of λ=790 nm. The pulse energy was set to E=3.9 μJ, resulting in a fluence well below the ablation threshold of the fused silica substrates. In addition, 3D electromagnetic simulations using a finite integration technique in time domain have been performed. The simulations demonstrate that indeed the local field in the vicinity of the tips of the triangular nanoparticles overcome the ablation threshold and easily explain the generated nanostructures. Most importantly, the simulations show, that higher order modes contribute to the ablation process. These modes cause ablation along the side edges of the nanoparticles. Finally, we demonstrate, that the optical properties of the triangular nanoparticles, which can be tuned by their morphology, are crucial parameters for the generation of the ablation structures. 相似文献
9.
Hong KH Siddiqui A Moses J Gopinath J Hybl J Ilday FO Fan TY Kärtner FX 《Optics letters》2008,33(21):2473-2475
We generate linearly polarized, 287 W average-power, 5.5 ps pulses using a cryogenically cooled Yb:YAG amplifier at a repetition rate of 78 MHz. An optical-to-optical efficiency of 41% is obtained at 700 W pump power. A 6 W, 0.4 nm bandwidth picosecond seed source at 1029 nm wavelength is constructed using a chirped-pulse fiber amplification chain based on chirped volume Bragg gratings. The combination of a fiber amplifier system and a cryogenically cooled Yb:YAG amplifier results in good spatial beam quality at large average power. Low nonlinear phase accumulation as small as 5.1 x 10(-3) rad in the bulk Yb:YAG amplifier supports power scalability to a > 10 kW level without being affected by self-phase modulation. This amplification system is well suited for pumping high-power high-repetition-rate optical parametric chirped-pulse amplifiers. 相似文献
10.
Laser controlled melting is one of the methods to achieve structural integrity in the surface region of the carbide tools. In the present study, laser heating of carbide cutting tool and temperature distribution in the irradiated region are examined. The phase change process during the heating is modeled using the enthalpy–porosity method. The influence of laser pulse intensity distribution across the irradiated surface (β) on temperature distribution and melt formation is investigated. An experiment is carried out and the microstructural changes due to laser consecutive pulse heating is examined using the scanning electron microscope (SEM). It is found that melt depth predicted agrees with the experimental results. The maximum depth of the melt layer moves away from the symmetry axis with increasing β. 相似文献