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排序方式: 共有265条查询结果,搜索用时 78 毫秒
1.
2.
Khalid A. Aleissa El-Said I. Shabana Fahad I.S. Al-Masoud 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(3):683-687
The capacity of algae to concentrate uranium under natural environmental conditions is measured by a-spectrometry. Spirogyra, a filamentous green fresh-water alga, has concentrated uranium from a surface concrete ponds with elevated uranium levels
(140-1140 ppb). The concentration factors (CFs) ranged from 8.9-67 with an average value of 22.Cladophora spp, a filamentous green marine alga has concentrated uranium from the marine water with a concentration factor ranged from 220–280.
The average concentration factor was 250. The factors affecting the sorption process are discussed in detail.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
The difference between the classical treatment offlexible body impact and the treatment of impact in flexiblemultibody dynamics is due to several fundamental reasons. Inthe classical impact theory, simple structures such as beamsand plates are used. Infinite dimensional models can bedeveloped for these simple structural elements to study theimpact dynamics and the wave propagation problem. Flexiblemultibody impact problems, on the other hand, involve bodieswith complex geometry that cannot be modeled using infinitenumber of degrees of freedom. Furthermore, the classicalimpact theory has been mainly concerned with the impactbetween a rigid mass that moves without constraints beforeit impacts a simple flexible structure. This is not amultibody simulation scenario in which the impact occursbetween kinematically constrained bodies that are subjectedto impulsive constraint forces in addition to the impactforces. These constraint forces can influence the motion ofthe two bodies immediately after impact, and as aconsequence, the simple classical theory scenario of impactdoes not apply. It is the objective of this paper to discussthe use of the restitution condition in flexible multibodyimpact problems and demonstrate that the use of thisapproach does not exclude the classical formulation.Nonetheless, the impulse momentum balance approach can serveas an effective and efficient procedure for solving theimpact problem in finite dimensional models that do not obeythe classical wave theory. Energy results of simplestructural elements are presented in order to demonstratethe consistency of using the impulse momentum balanceapproach in solving impact problems in finite dimensionalflexible body applications. 相似文献
4.
The kinetic behaviour of Cl(-), Br(-) and SCN(-) exchanges on hydrous tin oxide have been investigated under conditions of particle diffusion and the limited bath technique. Values for the diffusion coefficients, energy of activation and entropy of activation have been calculated. The data obtained have been compared with those reported for other organic and inorganic exchangers. 相似文献
5.
A new crystal-engineering motif has been developed where a ditopic receptor 1 shows a novel syn-syn hydrogen-bonded polymeric supramolecular complex (Fig. 4b) (instead of a 1:1 dimeric syn-syn or polymeric syn-anti complex) giving rise to a hydrogen-bonded stair-like polymeric ribbon structure between the binding groups of the receptor pyridine amide and the carboxyl groups of the guest substrate. 相似文献
6.
The extraction of hydrochloric, nitric, and sulphuric acids with TBP was studied as a function of methanol, ethanol, isopropanol, and acetone concentration in the aqueous phase. Extraction increases in the order: methanol相似文献
7.
R. Shabana S. M. Khalifa S. Abdalla H. F. Aly 《Journal of Radioanalytical and Nuclear Chemistry》1986,106(1):55-63
Extraction of WO
4
2–
and ReO
4
–
by Adogen-381, tricaprylmethylammonium chloride, Hyamine 10-X, trioctylphosphine oxide or dibenzylsulphoxide in xylene from HNO3, HCl or H2SO4 acid medium was investigated. Based on the separation factors obtained, the separation of ReO
4
–
from WO
4
2–
was elucidated. ReO
4
–
was separated from WO
4
2–
in high radiochemical purity: >99.9% by three successive extractions and strippings using Adogen-381 from HCl or HNO3 acid medium. 相似文献
8.
The distribution of Pa(V) between aqueous HCl solutions and organic phases of tricaprylamine has been described. The dependence of extraction on acidity, salting-agent and extractant concentration was investigated. The possible extraction mechanism is discussed in the light of results obtained. The separation of Pa(V) from Th(IV), U(VI) and rare earths, is also suggested. 相似文献
9.
A systematic study is presented on Pu IV extraction with tri-n-butyl phosphate and trilaurylamine from binary mixtures of H2SO4 with HCl and HBr. The addition of sulfuric acid to the mentioned mineral acid solutions, was found to affect appreciably DPu, which recommended some useful purification procedures. The effect of water-miscible alcohols on the extraction of plutonium from HCl and HNO3 solutions was also investigated. 相似文献
10.
R. Shabana 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2-4):293-296
Abstract Sodium alkoxide, a hard nucleophile, reacts with 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide (LR) on phosphorus to give O-alkyl S-sodium-(4-methoxyphenyl) phosphonothiolothionate 5 as an intermediate. Compound 5 reacts with benzyl (or benzoyl) chloride to give good yields of O-alkyl S-benzyl (benzoyl) (4-methoxy-phenyl)phosphonothiolothionate (6a–e). 相似文献