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191.
Summary Metal complexes of the title ligands were characterized in order to determine the factors influencing the stability of chelate isomerism in the same molecule. The ligands were prepared by 1:1 condensation of isonitrosoacetylacetone (Hiso) with eithero-aminophenol (H2
isoaph),p-aminophenol (H2
isopph), or aniline (Hisoanil). The following complexes have been synthesized: [(isoaph)Cu]4, (Hisoaph)2Co, (Hisopph)2
M·nH2O (M=Ni(II), n=2;M=Pd(II), n=0;M=Co(II), n=2), [(isopph) Cu·H2O]2, and (isoanil)2
M (M=Ni(II), Cu(II), Co(II), or Pd(II)). Both chelate rings in these metal complexes are five-membered. Transimination of one –C=N–C6H5 group to –C=NH in (isoanil)2Ni produced a six-membered chelate ring in (isoim)Ni(isoanil). The induced chelate isomerism is ascribed to intermolecular hydrogen bonding of the imino-hydrogen and the basic nitrogen of the same six-membered chelate ring of an adjacent square planar molecule. Other types of hydrogen bondings with the oximato oxygen (intra- or intermolecular) favour the formation of five-membered chelate rings. Analytical, spectroscopic, and magnetic moment data are in accordance with the suggested formulations.Part of the Ph.D. thesis of Sana M. Imam 相似文献
192.
Estevan F Lahuerta P Lloret J Sanaú M Ubeda MA Vila J 《Chemical communications (Cambridge, England)》2004,(21):2408-2409
Enantiomerically pure dirhodium(II) complexes with ortho-metalated p-substituted aryl phosphines have been shown to be enantio- and diastereoselective in the cyclopropanation of styrene by ethyl diazoacetate. Enantioselectivities up to 91% and diastereoselectivities up to 90% are observed for ethyl cis-2-phenylcyclopropanecarboxylate. 相似文献
193.
The carbene-ligand precursors methylenebis(N-alkylimidazolium) iodide (alkyl = methyl, neo-pentyl) and ethylenebis(N-methylimidazolium) chloride have been used in the preparation of several new Ru(II)-p-cymene complexes where the ligand behaves as mono- and bidentate. The molecular structures of the two biscarbene-complexes are reported. From the data reported, we can conclude that steric reasons (mainly the bisimidazolium linkers, methylene/ethylene) are the main factors determining both reactivity and synthetic difficulties of the products reported. 相似文献
194.
M. Sana 《International journal of quantum chemistry》1981,19(1):139-161
We use an experimental design method for computing a local quadratic form which is adequate to find stationary points and to evaluate the force constant matrix on a k-dimensional potential energy hypersurface. Two types of designs are particularly discussed: the composite and the Doehiert's plane. We give examples for illustrating the methodology. Some thermodynamical properties are deduced from our results. Such a method may be used with every type of theoretical calculations (SCF or CI ) and with any program without modification. 相似文献
195.
Summary We describe the geometric, electronic and energetic (H
f) properties of B2H
6
+
and BH
3
+
. Comparisons with experimental measurements have also been made with borane, diborane, BH, BH+ and BH
2
+
. All the theoretical calculations have been performed with various basis sets: 6-31G, 6-31G and 6-31+G (2d,f). The geometry optimizations are done at the SCF (RHF or UHF), MP2 and MP4 levels. 相似文献
196.
An h-hypergraph H is said to be quasi linear if every two edges of H intersect in 0 or r vertices (r ≥ 1 and h ≥ 2r + 1). The main result of this paper is the following: if G and H are chromatically equivalent h-hypergraphs, H is quasi linear and h ≥ 3r ? 1, then any two edges of G intersect in 0,1 or r vertices and the result cannot be strengthened. This extends the corresponding result of the first author for linear hypergraphs (case r = 1) [Tomescu in J Combin Theory B2 72: 229–235, 1988] 相似文献
197.
Let 𝒜 = (A n ) n≥0 be an ascending chain of commutative rings with identity, S ? A 0 a multiplicative set of A 0, and let 𝒜[X] (respectively, 𝒜[[X]]) be the ring of polynomials (respectively, power series) with coefficient of degree i in A i for each i ∈ ?. In this paper, we give necessary and sufficient conditions for the rings 𝒜[X] and 𝒜[[X]] to be S ? Noetherian. 相似文献
198.
Mumraiz Sana Ali Aamir Awais M. Shutaywi Meshal Shah Zahir 《Journal of Thermal Analysis and Calorimetry》2021,143(3):2135-2148
Journal of Thermal Analysis and Calorimetry - This paper explores the influence of entropy production on MHD hybrid nanofluid (Al2O3–Cu/H2O) flow due to permeable stretching sheet with... 相似文献
199.
Sungur S Uzar A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(1):225-229
The pH dependence of the complexes was determined by both potentiometric and spectrophotometric studies. Stability constants and stoichiometries of the formed complexes were determined using slope ratio method. Fe(III) was formed complexes with tannic acid of various stoichiometries, which in the 1:1 molar ratio at pH<3, in the 2:1 molar ratio at pH 3-7 and in the 4:1 molar ratio at pH>7. Fe(III) was formed complexes with myricetin in the 1:2 molar ratio at pH 4 and 5 and in the 1:1 molar ratio at pH 6. Stability constant values were found to be 10(5) to 10(17) and 10(5) to 10(9) for Fe(III)-tannic acid complexes and Fe(III)-myricetin complexes. Both tannic acid and myricetin were possessed minimum affinities to Cu(II) and Zn(II). They had less affinity for Al(III) than for Fe(III). 相似文献
200.