全文获取类型
收费全文 | 351篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 160篇 |
晶体学 | 2篇 |
力学 | 27篇 |
数学 | 64篇 |
物理学 | 108篇 |
出版年
2022年 | 11篇 |
2021年 | 21篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 30篇 |
2012年 | 28篇 |
2011年 | 15篇 |
2010年 | 20篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 10篇 |
2006年 | 15篇 |
2005年 | 10篇 |
2004年 | 3篇 |
2003年 | 7篇 |
2002年 | 18篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有361条查询结果,搜索用时 296 毫秒
161.
Ammar Abdalgabar A. S. Cornell Aldo Deandrea Ahmad Tarhini 《The European Physical Journal C - Particles and Fields》2014,74(5):1-8
In this work, we have studied the accretion of dark energies onto a Morris–Thorne wormhole. Previously, in ref. (González-Díaz, arXiv:hep-th/0607137), it was shown that for quintessence like dark energy, the mass of the wormhole decreases, and for phantom like dark energy, the mass of the wormhole increases. We have assumed two types of dark energy: the variable modified Chaplygin gas and the generalized cosmic Chaplygin gas. We have found the expression of the wormhole mass in both cases. We have found the mass of the wormhole at late universe and this is finite. For our choices of the parameters and the function $B(a)$ , these models generate only quintessence dark energy (not phantom) and so the wormhole mass decreases during the evolution of the universe. Next we have assumed the five kinds of parametrizations of well-known dark-energy models. These models generate both quintessence and phantom scenarios i.e., phantom crossing models. So if these dark energies accrete onto the wormhole, then for the quintessence stage, the wormhole mass decreases up to a certain value (a finite value) and then again increases to an infinite value for the phantom stage during whole evolution of the universe. That means that if the five kinds of DE accrete onto a wormhole, the mass of the wormhole decreases up to a certain finite value and then increases in the late stage of the evolution of the universe. We have also shown these results graphically. 相似文献
162.
H. Basti L. Ben Tahar L.S. Smiri F. Herbst M.-J. Vaulay F. Chau S. Ammar S. Benderbous 《Journal of colloid and interface science》2010,341(2):248-254
Superparamagnetic iron oxide nanoparticles, Fe3O4 and γ-Fe2O3, were produced by the so-called polyol process. In order to stabilize the particles in a physiological environment as potential contrast agents for Magnetic Resonance Imaging (MRI), the as-prepared particles were successfully transferred to an aqueous medium through ligand exchange chemistry of the adsorbed polyol species with the dopamine or the catechaldehyde. The ligands were able to participate in bidentate binding to the nanoparticles surface and to improve the stability of aqueous suspensions of the nanoparticles. Analysis was performed by various techniques including X-ray diffraction, transmission electron microscopy, infrared spectroscopy and thermal analysis. The results of magnetic measurements and initial in vitro magnetic resonance imaging essays are presented for the pre- and post-surface modified nanoparticles, respectively and discussed in relation with their structure and microstructure. 相似文献
163.
A screen-printed disposable electrode system for the determination of duloxetine hydrochloride (DL) was developed using screen-printing
technology. Homemade printing has been characterized and optimized on the basis of effects of the modifier and plasticizers.
The fabricated bi-electrode potentiometric strip containing both working and reference electrodes was used as duloxetine hydrochloride
sensor. The proposed sensors worked satisfactorily in the concentration range from 1.0 × 10-6-1.0 × 10-2 mol L-1 with detection limit reaching 5.0 × 10-7 mol L-1 and adequate shelf life of 6 months. The method is accurate, precise and economical. The proposed method has been applied
successfully for the analysis of the drug in pure and in its dosage forms. In this method, there is no interference from any
common pharmaceutical additives and diluents. Results of the analysis were validated statistically by recovery studies. 相似文献
164.
Farid Ammar Khodja Assia Benabdallah Manuel González-Burgos Luz de Teresa 《Comptes Rendus Mathematique》2013,351(19-20):743-746
In this note, we present a new result that relates the condensation index of a sequence of complex numbers with the null controllability of parabolic systems. We show that a minimal time is required for controllability. The results are used to prove the boundary controllability of some coupled parabolic equations. 相似文献
165.
Teow Chong Teoh Sawsam J. Al-Harbi Ammar Yasir Abdulrahman Hussin A. Rothan 《Molecules (Basel, Switzerland)》2021,26(14)
Zika virus (ZIKV) represents a re-emerging threat to global health due to its association with congenital birth defects. ZIKV NS2B-NS3 protease is crucial for virus replication by cleaving viral polyprotein at various junctions to release viral proteins and cause cytotoxic effects in ZIKV-infected cells. This study characterized the inhibitory effects of doxycycline against ZIKV NS2B-NS3 protease and viral replication in human skin cells. The in silico data showed that doxycycline binds to the active site of ZIKV protease at a low docking energy (−7.8 Kcal/mol) via four hydrogen bonds with the protease residues TYR1130, SER1135, GLY1151, and ASP83. Doxycycline efficiently inhibited viral NS2B-NS3 protease at average human temperature (37 °C) and human temperature with a high fever during virus infection (40 °C). Interestingly, doxycycline showed a higher inhibitory effect at 40 °C (IC50 = 5.3 µM) compared to 37 °C (9.9 µM). The virus replication was considerably reduced by increasing the concentration of doxycycline. An approximately 50% reduction in virus replication was observed at 20 µM of doxycycline. Treatment with 20 µM of doxycycline reduced the cytopathic effects (CPE), and the 40 µM of doxycycline almost eliminated the CPE of human skin cells. This study showed that doxycycline binds to the ZIKV protease and inhibits its catalytic activity at a low micro-molecular concentration range. Treatment of human skin fibroblast with doxycycline eliminated ZIKV infection and protected the cells against the cytopathic effects of the infection. 相似文献
166.
M. S. A. El-Gaby N. M. Saleh J. A. Micky Y. A. Ammar H. S. A. Mohamed 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):1655-1663
Cyclopentanone (1) was exploited as a starting material for the syntheses of hitherto unknown cyclopenta[d][1,3]thiazine derivatives. 相似文献
167.
Pascal Morel Ammar Sharaiha Romain Brenot Bruno Thédrez 《Optical and Quantum Electronics》2006,38(1-3):231-236
Modelling Semiconductor Optical Amplifiers (SOA) is of great interest for their multi-functional application studies. We defined a wideband model thanks to SOA material gain and spontaneous emission wideband definitions. We managed to fit simulations for several SOAs for a wide range of input wavelengths, bias currents and input optical powers. 相似文献
168.
R. A. Karakhanov V. I. Kelarev V. N. Koshelev G. V. Morozova Ammar Dibi 《Chemistry of Heterocyclic Compounds》1995,31(2):208-218
The condensation of hydrochloride sats of iminoesters of furan acids with hydrazides of carboxylic acids gives 2,5-disubstituted 1,3,4-oxadiazoles containing furan fragments. Such compounds are also formed in the condensation of hydrazides of 5-R-furan-2-carboxylic acids with hydrocloride salts of carboxylic acid iminoesters. The reaction of furan acids with hydrazine dihydrochloride in polyphosphoric acid gave symmetrically disubstituted 1,3,4-oxadiazoles containing furan fragments.Communication 3, see ref. [1].I. M. Gubkin State Petroleum and Natural Gas Institute, 117917, Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 238–249, February, 1995. Original article submitted January 24, 1995. 相似文献
169.
A. M. A. Alaghaz R. A. A. Ammar 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2827-2844
Interaction of hydrazones and semicarbazones derivatives I a ? t with diphenylchlorophosphine II , gave new compounds III a?t , and their complexation ability towards various divalent metal acetates Mn(OAc)2. 4H2O, Co(OAc)2. 4H2O, Ni(OAc)2. 4H2O, and Cu(OAc)2. H2O, in organic solvents are described. The metal/ phosphorsemi-carbazones ratios are measured and the results discussed. All these complexes are insoluble in organic solvents and in water. The structures of the isolated products were proposed on the basis of microanalyical data, TGA, IR, (UV/ VIS), (MS), and 1H, 13C, and 31P-NMR spectroscopic analyses and magnetic susceptibility. The proposed structure of the complexes is based on a 1: 2 metal: ligand ratio. All of the complexes are found to have an octahedral geometry, with the exception of the square planar copper (II) complexes. The corrosion inhibition of aluminium and copper in 1 M HCl and chromium–nickel steel in crude oil using IIIn have been studied by weight loss method. 相似文献
170.
Y. A. Ammar Y. A. Mohamed G. A. M. El-Hagali A. S. Abd El-Aal M. S. A. El-Gaby 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):1386-1394
2-Ethoxycarbonylmethylidine-4,5-dihydro-4-thiazolinone (1) was condensed with bis aromatic aldehydes such as terephthalaldehyde or 4,4′-bisformyl-diphenylether (2a,b) (2:1 molar ratio) and furnished bis-4-thiaozlidinones (3a,b). The reaction of (3a,b) with malononitrile and aromatic aldehydes (1:2:2 molar ratio) gave bis thiazolopyridines (4a–d). Bis-(thiazolopyridine) derivative (6) was obtained by reaction of 4-thiaozlinone (5c) with bis aldehyde (2b) in refluxing ethanol containing piperidine. Cyclization of 4-thiazolinones (5a,b) with different α-cyanocinnamonitriles gave thiazolo[3,2-a]pyridines (7a–d). Compound 9 was produced via the reaction of 8 with thioglycolic acid, which reacted with p-chlorobenzaldehyde to produce 10. Compound 10 was condensed with hydrazine hydrate and afforded 11. Compounds 12 and 16a,b were produced by the reaction of 9 with isatin and α-ethoxycarbonylcinnamonitriles, respectively. 相似文献