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排序方式: 共有381条查询结果,搜索用时 15 毫秒
361.
Abstract: γ-Hydroxysilanes 4 can be easily prepared from bromosilyl ethers 3 by a reaction involving 1,4-migration of the silicon group from oxygen to carbon. 相似文献
362.
In this work, the polypropylene impact copolymers were synthesized by a modified sequential polymerization process. The copolymerization of ethylene and propylene was carried out between two homopolymerization stages at two different pressures and temperatures and the rheology, morphology and thermal properties of reactor alloys were studied. It is found that the ethylene propylene rubber (EPR) content increased up to 32 wt% by increasing the copolymerization time to 20 min. At a fixed copolymerization time of 10 min, the addition of 50 ppm hydrogen (H2), increased the EPR content from 9.7 to 12.8 wt%. By doubling H2 concentration, no considerable change in EPR wt% was observed. It is found that the zero shear viscosity of the alloys is significantly under the influence of EPR wt%, not the molecular weight of matrix. The molecular weight of PP matrices determined by rheological data, mildly decreased from 463000 to 458000 g/mol by increasing the copolymerization time from 10 min to 15 min. At high copolymerization time/high H2 concentration, a melting peak in the differential scanning calorimetry test around 165°C for isotactic PP and also an endothermic peak around 127°C for the block copolymer with long ethylene segments, is observed. The study of interfacial strength by theoretical emulsion models showed that 15 min copolymerization time is optimum considering EPR wt%. 相似文献
363.
Rushdi I. Yousef Martin BetteGoran N. Kalu?erovi? Reinhard PaschkeCui Yiran Dirk SteinbornHarry Schmidt 《Polyhedron》2011,30(12):1990-1996
Potassium dichlorido(l-prolinato)platinate(II), K[PtCl2(l-proH)] (1), and chlorido(dimethyl sulfoxide)(l-prolinato)platinum(II), [PtCl(l-proH)(dmso)] (2), were synthesized by ligand substitution reactions. Both complexes were characterized by 1H, 13C, and 195Pt NMR spectroscopy, elemental analysis, and HR-ESI-MS. The molecular structures of 1 and 2 were determined by single crystal X-ray diffraction, proving bidentate coordinated l-prolinato ligand and SP-4-4 configuration of 2a. With the help of DFT calculations stability of possible isomers of 1 and 2 was studied. A considerable difference in the in vitro cytotoxicity of 1 versus 2a (exchange of one chlorido ligand by dmso) against four human cancer cell lines was found. 相似文献
364.
Yousef Fazaeli Amir R. Jalilian Mostafa M. Amini Ali Rahiminejad-kisomi Saeed Rajabifar Fatemeh Bolourinovin Sedigheh Moradkhani 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(1):17-24
[67Ga]labeled tetraphenyl porphyrin ([67Ga]-TPP) was prepared using freshly prepared [67Ga]GaCl3 and tetraphenyl porphyrin (TPPH2) for 30–60 min at 25 °C (radiochemical purity: >97 ± 1% ITLC, >98 ± 0.5% HPLC, specific activity: 13–14 GBq/mmol). Stability
of the complex was checked in final formulation and human serum for 24 h. The partition coefficient was calculated for the
compound (log P 1.89). The biodistribution of the labeled compound in vital organs of wild-type rats was studied using scarification studies
and SPECT imaging up to 24 h. A detailed comparative pharmacokinetic study performed for 67Ga cation and [67Ga]-TPP. The complex is mostly washed out from the circulation through kidneys and can be an interesting tumor imaging/targeting
agent due to low liver uptake and rapid excretion through the urinary tract. 相似文献
365.
A dynamic unreliability assessment and optimal maintenance strategies for multistate weighted k‐out‐of‐n:F systems 下载免费PDF全文
In this paper, a dynamic evaluation of the multistate weighted k‐out‐of‐n:F system is presented in an unreliability viewpoint. The expected failure cost of components is used as an unreliability index. Using failure cost provides an opportunity to employ financial concepts in system unreliability estimation. Hence, system unreliability and system cost can be compared easily in order to making decision. The components' probabilities are computed over time to model the dynamic behavior of the system. The whole system has been assessed by recursive algorithm approach. As a result, a bi‐objective optimization model can be developed to find optimal decisions on maintenance strategies. Finally, the application of the proposed model is investigated via a transportation system case. Matlab programming is developed for the case, and genetic algorithm is used to solve the optimization model. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
366.
Yousef Jahani 《先进技术聚合物》2011,22(6):942-950
The effect of filler types of mica and talc on the oscillatory shear rheological properties, mechanical performance, and morphology of the chemically coupled polypropylene composites is studied in this work. The Maleic Anhydride grafted Polypropylene (MAPP) was used as an adhesion promoter for coupling mineral particles with the polypropylene matrix. The samples were prepared by a co‐rotating, L/D = 40, 25 mm twin screw extruder. The tensile tests carried out on the injection molded samples showed a reinforcing effect of talc up to 20 wt% on the Polypropylene (PP). The tensile strength of PP‐mica composites showed a slight decrease at all percentages of mica. The effect of chemical coupling by using MAPP on the tensile strength was more pronounced in increasing the tensile strength for PP‐mica than PP‐talc composites. The complex viscosity curve of pure PP and the composites, showed a Newtonian plateau (η0) up to 30 wt% at low frequency terminal zone. By increasing the filler content to 40 and 50 wt%, the complex viscosity at very low shear rates sharply increased and showed yield behavior that can be due to the formation of filler particles networks in the melt. At the optimum amount of coupling agent, a minimum in cross over frequency curve against MAPP content is observed. The optimum amount of coupling agent for PP‐talc composites is about 1.5%, and about 3% for PP‐mica formulations. The analysis of viscosity behavior at power‐law high region, revealed the more shear thinning effect of mica than talc on the PP matrix resin. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
367.
The reaction of (1R,2R)‐(–)‐1,2‐diaminocyclohexane ( 1 ) [DACH] with the aldehyde (1R)‐(–)‐myrtenal ( 2 ) in MeOH afforded the bidentate diimine ligand, (1R,2R)‐(–)‐N1,N2‐bis{(1R)‐(–)myrtenylidene}‐1,2‐diaminocyclohexane ( 3 ) in a high yield. Reduction of 3 using LiAlH4 led to the formation of the desired ligand ( 4 ) (1R,2R)‐(–)‐N1,N2‐bis{(1R)‐(–)myrtenyl}‐1,2‐diaminocyclohexane. Treatment of compound 4 with K2PtCl4 or K2PdCl4 yielded the corresponding platinum(II) and palladium(II) complexes, Pt‐5 and Pd‐6 , respectively. The reaction of compound 3 with K2PtCl4 gave the diimine complex Pt‐7 . The cytotoxic activity of the complexes Pt‐5 , Pd‐6 and Pt‐7 was tested and compared to the approved drugs, cisplatin ( Cis ‐Pt ) and oxaliplatin ( Ox‐Pt ). The complexes ( Pt‐5 , Pd‐6 and Pt‐7 ) inhibit L1210 cell line proliferation with an IC50 of 0.6, 4.2, and 0.7 μL, respectively as evidenced by measuring thymidine incorporation. 相似文献
368.
Thermal Degradation of Hydrolyzed and Oxidized Lignins 总被引:1,自引:0,他引:1
Nada A. M. A. Abou Yousef H. El-Gohary S. 《Journal of Thermal Analysis and Calorimetry》2002,68(1):265-273
The infrared spectra of lignin treated with hydrochloric acid and peroxyacetic acid is investigated. The hydrolysed lignin
spectra show a high intensity phenolic OH band at 1375 cm−1 and a decrease in the intensities of CH vibration of methoxyl group at 2920–2810 cm−1 and of the linkage (β–O–4 linkage) at 1120 cm−1.
In contrast, the intensity of methoxy group band increases in the case of lignin treated with peroxyacetic acid. This treatment
increases also the intensity of the C=O band at 1710 cm−1. The intensity of C=C of aromatic ring band at 1605 and1505 cm−1 is highly affected by the treatment of lignin with peroxyacetic acid, it decreases with large value than in case of lignin
treated with HCl.
The thermal behavior of these types of lignin has also been studied. The initial and char temperatures of lignin were determined
to be 280 and 700°C respectively for unreacted lignin while were 265and 550; 220 and 580°C for lignins treated with hydrochloric
and peroxyacetic acid respectively. The rate constants of the mass loss of untreated, hydrolysed and oxidized lignins were
found to be 0.05, 0.045 and 0.044 min−1 respectively.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
369.
Yousef TA Abu El-Reash GM Rakha TH El-Ayaan U 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,83(1):271-278
Manganese(II), iron(II), cobalt(II), nickel(II), copper(II), and chromium(III) complexes of (E)-2-(2-(2-hydroxybenzylidene)hydrazinyl)-2-oxo-N-phenylacetamide were synthesized and characterized by elemental and thermal (TG and DTA) analyses, IR, UV-vis and (1)H NMR spectra as well as magnetic moment. Mononuclear complexes are obtained with 1:1 molar ratio except [Mn(HOS)(2)(H(2)O)(2)] and [Co(OS)(2)](H(2)O)(2) complexes which are obtained with 1:2 molar ratios. The IR spectra of ligand and metal complexes reveal various modes of chelation. The ligand behaves as a monobasic bidentate one and coordination occurs via the enolic oxygen atom and azomethine nitrogen atom. The ligand behaves also as a monobasic tridentate one and coordination occurs through the carbonyl oxygen atom, azomethine nitrogen atom and the hydroxyl oxygen. Moreover, the ligand behaves as a dibasic tridentate and coordination occurs via the enolic oxygen, azomethine nitrogen and the hydroxyl oxygen atoms. The electronic spectra and magnetic moment measurements reveal that all complexes possess octahedral geometry except the copper complexes possesses a square planar geometry. From the modeling studies, the bond length, bond angle, HOMO, LUMO and dipole moment had been calculated to confirm the geometry of the ligands and their investigated complexes. The thermal studies showed the type of water molecules involved in metal complexes as well as the thermal decomposition of some metal complexes. The protonation constant of the ligand and the stability constant of metal complexes were determined pH-metrically in 50% (v/v) dioxane-water mixture at 298 K and found to be consistent with Irving-Williams order. Moreover, the minimal inhibitory concentration (MIC) of these compounds against Staphylococcus aureus, Escherechia coli and Candida albicans were determined. 相似文献
370.
Yousef I. Salamin 《Physics letters. A》2010,374(48):4950-4953
Two constants of the motion, which simplify the relativistic particle dynamics in a laser beam of radial polarization, are identified. Many-particle simulations based on the reduced set of equations of motion in a beam of relativistic intensity, demonstrate acceleration in vacuum to GeV energies of electrons, alpha particles and oxygen bare nuclei. The axially-injected particles are shown to be accelerated with negligible diffraction. 相似文献