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11.
Sana Siva Prasad Bandameeda Ramesh Naidu Marlia M. Hanafiah Jangam Lakshmidevi Ravi Kumar Marella Sivarama Krishna Lakkaboyana Katta Venkateswarlu 《Molecules (Basel, Switzerland)》2021,26(17)
Metalloporphyrins (and porphyrins) are well known as pigments of life in nature, since representatives of this group include chlorophylls (Mg-porphyrins) and heme (Fe-porphyrins). Hence, the construction of chemistry based on these substances can be based on the imitation of biological systems. Inspired by nature, in this article we present the preparation of five different porphyrin, meso-tetraphenylporphyrin (TPP), meso-tetra(p-anisyl)porphyrin (TpAP), tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (TSTpSPP), meso-tetra(m-hydroxyphenyl)porphyrin (TmHPP), and meso-tetra(m-carboxyphenyl)porphyrin (TmCPP) as well as their N-pincer Pd(II)-complexes such as Pd(II)-meso-tetraphenylporphyrin (PdTPP), Pd(II)-meso-tetra(p-anisyl)porphyrin (PdTpAP), Pd(II)-tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (PdTSTpSPP), Pd(II)-meso-tetra(m-hydroxyphenyl)porphyrin (PdTmHPP), and Pd(II)-meso-tetra(m-carboxyphenyl)porphyrin (PdTmCPP). These porphyrin N-pincer Pd(II)-complexes were studied and found to be effective in the base-free self-coupling reactions of potassium aryltrifluoroborates (PATFBs) in water at ambient conditions. The catalysts and the products (symmetrical biaryls) were characterized using their spectral data. The high yields of the biaryls, the bio-mimicking conditions, good substrate feasibility, evading the use of base, easy preparation and handling of catalysts, and the application of aqueous media, all make this protocol very attractive from a sustainability and cost-effective standpoint. 相似文献
12.
Rama Moorhy Appa S. Siva Prasad Jangam Lakshmidevi Bandameeda Ramesh Naidu Manchala Narasimhulu Katta Venkateswarlu 《应用有机金属化学》2019,33(10)
An agro waste‐derived, ‘water extract of pomegranate ash’ (WEPA), has been utilized for the first time as a renewable medium for Pd(OAc)2‐catalysed Suzuki–Miyaura cross‐coupling at room temperature. This method offers a simple and sustainable synthesis of biaryls from aryl halides and arylboronic acids under ligand‐ and external base‐free aerobic and ambient conditions. This method has been found effective for both activated and unactivated aryl halides in the production of biaryls with moderate to nearly quantitative yields. The protocol shows high chemoselectivity over identical/similar reactive sites in aryl halides (i.e. selectivity over identical halogens or different halogens of aryl halides). This method exhibits high regioselectivity, i.e. the selective reactivity of a halogen over other identical halogens at different positions on the aromatic nucleus. Therefore, we disclose here a clean, benign, substantial chemo‐ and regioselective and highly economic alternative method for the palladium‐assisted synthesis of biaryls using an agro waste‐derived medium. 相似文献
13.
A.Vijender ReddyK. Ravinder T.Venkateshwar GoudP. Krishnaiah T.V. RajuY. Venkateswarlu 《Tetrahedron letters》2003,44(33):6257-6260
Reaction of indoles with electron deficient olefins under the influence of bismuth triflate has been studied at ambient temperature and affords the corresponding 3-alkylated indoles in excellent yields. 相似文献
14.
An efficient, cost-effective and environmentally benign synthesis of novel tetracyclic bis-isoxazolopyrroloquinoline derivatives has been developed via one-pot four-component reaction of 4-amino-3-methyl-5-styrylisoxazoles, dimedone, aryl glyoxal monohydrates and 5-amino-3-methylisoxazole by employing water as a reaction medium and acetic acid (AcOH) as a green promoter. The advantages of this protocol are environmentally friendly, metal-free, less reaction time, operational simplicity, high yields, broad substrate scope and easy purification. Most significant of all, this method is green. 相似文献
15.
16.
Forbidden hyperfine transitions are observed in the electron spin resonance spectrum of divalent Mn55 ion in NaCl single crystal for a particular associated pair. From the measurements of the M = + 1/2 → ?1/2, Δm = ± 1 transitions the parametersQ′ and Q″ of the nuclear electric quadrupole part of the spin-Hamiltonian Ho = Q′ [Iz 2 ? 1/3 I (I + 1)] + Q″ (Ix 2?Iy 2) are found to be + 1.70 × 10?4 cm.?1 and +0.16 × 10?4 cm.?1 respectively. 相似文献
17.
The purpose of this note is to generalize a theorem of Tamura’s [3] providing a self-contained and, we think, more elementary
proof than Tamura’s in that it avoids using the theory of contents. Tamura’s result states that a semigroup S satisfies an
identify xy=f(x,y) with f(x,y) a word of length greater than 2 which starts with y and ends in x if and only if S is an inflation
of a semilattice of groups satisfying the same identity. We investigate semigroups as in Tamura’s Theorem, except that we
permit f(x,y) to vary with x and y. 相似文献
18.
19.
The absorption spectrum of Co2+ doped NH4Cl has been studied from the room temperature to the liquid nitrogen temperature. A sudden change in the spectrum is observed between 243° K and 233° K which is attributed to the phase transition in the crystal. From the observed spectrum it is suggested that Co2+ goes in interstitially as well as substitutionally. Both the types of centers exist at room temperature, but with decrease in temperature substitutional ions migrate to interstitial sites, the process being stimulated at the phase transformation point so that the 77° K spectrum seems to be mostly due to the interstitial centers. The 77° K spectrum is analyzed in the approximation of octahedral symmetry for interstitial ions and the band positions are fitted fairly well with B = 870 cm.?1 Dq = 850 cm.?1 and C = 4·4 B. A blue shift of about 100 cm.?1 is observed for4T1 (P) band at the phase transition which is attributed to the increase in Dq value with the anomalous lattice contraction at the phase transition. The decrease in the lattice parameter calculated from this blue shift is around 0·4% which is in good agreement with the results of X-ray measurements. Two possible models for the interstitial complex are examined and the one with fourfold chlorine coordination associated with two neutral water molecules at the first neighbour (NH4)+ site lying along < 100> direction is suggested to be more probable. 相似文献
20.
Utility of Zeo-Karb 226 and Dowex A-l for the separation of Tl and In at 5-ppm level from high-purity zinc and zinc-base alloys has been investigated. With Zeo-Karb 226 (NH(4)(+)), T1(+) is conveniently separated from these materials and also from many other cations, with l.0M ammonium nitrate as the eluent. It is subsequently determined with Rhodamine B. This separation principle is also applied to the analysis of Pb-Tl alloys. Both Tl and In (along with Fe) are preconcentrated on Zeo-Karb 226(H(+)) from a solution of the sample at pH 3.0. Suitable methods of subsequent determination of Tl and In are described. In the case of Dowex A-1(H(+)), Tl(+), In(3+), Fe(3+) and Cu(2+) are retained from a solution of the sample at pH 2.0. An o-phenanthroline solution at pH 2.0 elutes all but traces of Cu(2+). In(3+) along with Fe(3+) is eluted with l.0M hydrochloric acid. Finally, Tl is eluted with 2.0M hydrochloric acid containing sulphurous acid. 相似文献