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41.
The problem of coupled heat and mass transfer by natural convection from a semi-infinite inclined flat plate in the presence
of an external magnetic field and internal heat generation or absorption effects is formulated. The plate surface has a power-law
variation of both wall temperature and concentration and is permeable to allow for possible fluid wall suction or blowing.
The resulting governing equations are transformed using a similarity transformation and then solved numerically by an implicit,
iterative, finite-difference scheme. Comparisons with previously published work are performed and good agreement is obtained.
A parametric study of all involved parameters is conducted and a representative set of numerical results for the velocity
and temperature profiles as well as the skin-friction parameter, average Nusselt number, and the average Sherwood number is
illustrated graphically to show typical trends of the solutions.
Received on 26 October 1998 相似文献
42.
43.
The job-shop scheduling problem (JSP) is one of the hardest problems (NP-complete problem). In a lot of cases, the combination of goals and resource exponentially increases search space. The objective of resolution of such a problem is generally, to maximize the production with a lower cost and makespan. In this paper, we explain how to modify the objective function of genetic algorithms to treat the multi-objective problem and to generate a set of diversified “optimal” solutions in order to help decision maker. We are interested in one of the problems occurring in the production workshops where the list of demands is split into firm (certain) jobs and predicted jobs. One wishes to maximize the produced quantity, while minimizing as well as possible the makespan and the production costs. Genetic algorithms are used to find the scheduling solution of the firm jobs because they are well adapted to the treatment of the multi-objective optimization problems. The predicted jobs will be inserted in the real solutions (given by genetic algorithms). The solutions proposed by our approach are compared to the lower bound of the cost and makespan in order to prove the quality and robustness of our proposed approach. 相似文献
44.
Turky Abdallah Bayoumi Ashraf H. Sherbiny Farag F. El-Adl Khaled Abulkhair Hamada S. 《Molecular diversity》2021,25(1):403-420
Molecular Diversity - The discovery of potent STAT3 inhibitors has gained noteworthy impetus in the last decade. In line with this trend, considering the proven biological importance of... 相似文献
45.
Saoud A. M. Metwally Maisa I. Abdel Moneim Yasser A. Elossely Radwa I. Awad Khaled Abou-Hadeed 《Chemistry of Heterocyclic Compounds》2010,46(4):426-437
Syntheses of various derivatives of 3,5-pyrazolidenedione are reported. This includes 4-arylidene (alkylidene or aralkylidene)-3,5-pyrazolidinediones,
which on epoxidation gave unreported oxiranes. The syntheses of these derivatives were based on either the Knoevenagel reaction
of carbonyl derivatives with 3,4-pyrazolidinedione or cyclization of arylidene (alkylidene) malonic acid hydrazide with glacial
acetic acid. 4-Arylazo-3,5-pyrazolidinedione derivatives were also prepared by coupling of aryldiazonium salts with 3,5-pyrazolidinedione
or cyclization of arylazomalonic acid hydrazide. Reduction of 4-benzylidene derivatives gave the corresponding benzyl derivatives.
The structure of the new products was confirmed by elemental and spectral analyses and X-ray crystallography. 相似文献
46.
Khaled Boughzala Nadia Gmati Khaled Bouzouita Ali Ben Cherifa Pierre Gravereau 《Comptes Rendus Chimie》2010,13(11):1377-1383
Several studies demonstrated the ability of britholites to retain radionuclides such as the caesium and actinides. Therefore, three compounds with formulas Sr8LaCs(PO4)6F2, Sr7La2Cs(PO4)5(SiO4)F2 and Sr2La7Cs(SiO4)6F2, were prepared by solid state reaction. However, it seems that only the mono-silicated composition was obtained in a pure state. In this present work, the X-ray diffraction and magnetic nuclear resonance have been used to investigate the structure for this composition. The results showed that in fact this phase was not pure, but it was mixed with a secondary phase, SrLaCs(PO4)2. The refinement by the Rietveld method allowed also to precise the distribution of La3+ and Cs+ ions between the two cationic sites of the apatite. 相似文献
47.
Khaled M. Elsabawy Morsy M. Abou Sekkina Mohamed A. Asker Mohamed H. El-Newehy 《Solid State Sciences》2010,12(7):1094-1097
The sample with in the general formula Bi2-xPbxSrV2O9, where x = 0.0, 0.05, 0.1, 0.2, 0.3, and 0.6 mol were synthesized by the high temperature solid state reaction and firing method. The X-ray diffractograms confirmed the formation of single phased layered perovskite in all samples. TGA and DTA thermal analyses on the green samples included steps of thermal analysis of strontium carbonate, bismuth carbonate, ammonium vanadate, lead oxide and finally on the high temperature solid state formation. The effect of lead dopings on the sintering, structural and micro-structure, properties of 212BiSrV-ceramics were investigated. The infrared absorption spectra show a series of vibrational modes within the range of 400–1600 cm?1. 相似文献
48.
Khaled Habib 《Optical Review》2011,18(4):324-330
A critical (steady state) value of the thermal expansion coefficients of different coatings was determined by a nondestructive
technique (NDT) known as laser shearography. The behavior of organic coatings, i.e., ACE premium-grey enamel, a yellow acrylic
lacquer, and a gold nail polish on a metallic alloy, i.e., a carbon steel, was investigated over a temperature range of 20–60
°C. The value of the thermal expansion coefficients of coatings was derived from the slope of the plot of the thermal deformation
(strain) versus the applied temperature. The integrity of the coatings with respect to time was assessed by comparison the
measured coefficients of thermal expansion (CTE) to the critical (steady state) or asymptotic value of CTE. By shearography,
measurement of coating properties could be performed independent of parameters such as UV exposure, humidity, presence of
chemical species, and other parameters which may normally interfere with conventional methods of the assessing of the integrity
of coatings. Therefore, one may measure CTE of coatings, regardless of the history of the coating, in order to assess the
integrity of coatings. Also, the obtained shearography data were found to be in a reasonable trend with the data of electrochemical
impedance spectroscopy (EIS) in 3%NaCl solution. 相似文献
49.
We study the complexity of determining whether a polytope given by its vertices or facets is combinatorially isomorphic to its polar dual. We prove that this problem is Graph Isomorphism hard, and that it is Graph Isomorphism complete if and only if Vertex Enumeration is Graph Isomorphism easy. To the best of our knowledge, this is the first problem that is not equivalent to Vertex Enumeration and whose complexity status has a non-trivial impact on the complexity of Vertex Enumeration irrespective of whether checking Self-duality turns out to be strictly harder than Graph Isomorphism or equivalent to Graph Isomorphism. The constructions employed in the proof yield a class of self-dual polytopes that are interesting on their own. In particular, this class of self-dual polytopes has the property that the facet-vertex incident matrix of the polytope is transposable if and only if the matrix is symmetrizable as well. As a consequence of this construction, we also prove that checking self-duality of a polytope, given by its facet-vertex incidence matrix, is Graph Isomorphism complete, thereby answering a question of Kaibel and Schwartz. 相似文献
50.
It has been found that dimethyl heptalene-4,5-dicarboxylates, when treated with 4 mol-equiv. of lithiated N,N-dialkylamino methyl sulfones or methyl phenyl sulfone, followed by 4 mol-equiv. of BuLi in THF in the temperature range of ?78 to 20°, give rise to the formation of 3-[(N,N-dialkylamino)sulfonyl]- or 3-(phenylsul-fonyl)benzo[a]heptalene-2,4-diols of. (cf. Scheme 4, and Tables 2 and 3). Accompanying products are 2,4-bis{[(N,N-dialkylamino)sulfonyl]methyl}- or 2,4-bis[(phenylsulfonyl)methyl]-4,10a-dihydro-3H-heptaleno[1,10-bc]furan-3-carboxylates as mixtures of diastereoisomers of. cf. Scheme 4, and (Tables 2 and 3) which are the result of a Michael addition reaction of the lithiated methyl sulfones at C(3) of the heptalene-4,5-dicarboxylates, followed by (sulfonyl)methylation of the methoxycarbonyl group at C(5) and cyclization of. (cf. Scheme 5). It is assumed that the benzo[a]heptalene formation is due to (sulfonyl)methylation of both methoxycarbonyl groups of the heptalene-4,5-dicarboxylates of. (cf. Schemes 6 and 8). The resulting bis-enolates 35 are deprotonated further. The thus formed tris-anions 36 can then cyclize to corresponding tris-anions 37 of cyclopenta[d]heptalenes which, after loss of N,N-dialkylamido sulfite or phenyl sulfinate, undergo a ring-enlargement reaction by 1,2-C migration finally leading to the observed benzo[a]heptalenes of. (cf. Schemes 8 and 9). The structures of the new product types have been finally established by X-ray crystal-structure analyses (cf. Figs. 1 and 2 as well as Exper. Part). 相似文献