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排序方式: 共有291条查询结果,搜索用时 875 毫秒
81.
Indranil Biswas 《Indagationes Mathematicae》2005,16(1):1-19
Let G be a connected semisimple linear algebraic group defined over an algebraically closed field k and P ⊂ G a parabolic subgroup without any simple factor. Let H be a connected reductive linear algebraic group defined over the field k such that all the simple quotients of H are of classical type. Take any homomorphism π : P → H such that the image of p is not contained in any proper parabolic subgroup of H. Consider the corresponding principal H-bundle EP(H) = (G × H)/P over G/P. We prove that EP (H) is strongly stable with respect to any polarization on G/P. 相似文献
82.
Indranil Bhattacharyya Sanjib Ganguly Bikash Kumar Panda Animesh Chakravorty 《Journal of Chemical Sciences》2008,120(1):87-93
The reaction of [RhCl2(HPhL)(PhL)] with MII(ClO4)2·6H2O in presence of alkali has furnished trinuclear [RhCl2(PhL)2]2M(H2O)2·H2O (HPhL is phenylazobenzaldoxime; M = Mn, Co, Ni). A similar reaction with MI(PPh3)2NO3 yielded binuclear [RhCl2(PhL)2]M(PPh3)2 (M = Cu, Ag). In these molecules the oximato group acts as a bridge between RhIII (bonded at N) and MII or MI (bonded at O). In structurally characterized [RhIIICl2(PhL)2]2Mn(H2O)2.H2O the centrosymmetric distorted octahedral MnO6 coordination sphere is spanned by four oximato oxygen atoms and two water molecules lying in trans position. In the lattice the neighbouring molecules are held together by H2O⋯H2O⋯H2O hydrogen bonds generating infinite zigzag chains. The manganese atoms lie parallel to the C-axis, the shortest Mn...Mn distance
being 7.992 ?. Magnetic exchange interactions if any are small as seen in room temperature magnetic moments. The manganese
system displays a strong EPR signal near g = 2.00. In the complex [RhCl2(PhL)2]Cu(PPh3)2 the copper atom is coordinated to two oximato oxygen atoms and the two phosphorus atoms in a distorted tetrahedral geometry.
The softness of the phosphine ligand is believed to sustain the stable coordination of hard oximato oxygen to soft CuI. The coordination sphere of the RhIII atom in both the complexes is uniformly trans-RhN4Cl2. 相似文献
83.
Let X be an irreducible smooth projective curve, of genus at least two, defined over an algebraically closed field of characteristic
different from two. If X admits a nontrivial automorphism σ that fixes pointwise all the order two points of Pic0(X), then we prove that X is hyperelliptic with σ being the unique hyperelliptic involution. As a corollary, if a nontrivial automorphisms of X fixes pointwise all the theta characteristics on X, then X is hyperelliptic with being its hyperelliptic involution.
相似文献
84.
A novel methodology for the synthesis of 9,10-dihydrophenanthrene and its analogues has been developed via a palladium-assisted 6pi electrocyclic reaction followed by formaldehyde elimination. 相似文献
85.
Baran P Boca R Chakraborty I Giapintzakis J Herchel R Huang Q McGrady JE Raptis RG Sanakis YO Simopouloso A 《Inorganic chemistry》2008,47(2):645-655
A one-pot synthetic procedure yields the octanuclear Fe(III) complexes Fe(8)(micro(4-)O)(4)(micro-pz(*))(12)X(40, where X = Cl and pz(*) = pyrazolate anion (pz = C(3)H(3)N(2)-) (1), 4-Cl-pz (2), and 4-Me-pz (3) or X = Br and pz(*) = pz (4). The crystal structures of complexes 1-4, determined by X-ray diffraction, show an Fe(4)O(4)-cubane core encapsulated in a shell composed of four interwoven Fe(micro-pz(*))(3)X units. Complexes 1-4 have been characterized by 1H NMR, infrared, and Raman spectroscopies. M?ssbauer spectroscopic analysis distinguishes the cubane and outer Fe(III) centers by their different isomer shift and quadrupole splitting values. Electrochemical analyses by cyclic voltammetry show four consecutive, closely spaced, reversible reduction processes for each of the four complexes. Magnetic susceptibility studies, corroborated by density functional theory calculations, reveal weak antiferromagnetic coupling among the four cubane Fe centers and strong antiferromagnetic coupling between cubane and outer Fe atoms of 1. The structural similarity between the antiferromagnetic Fe(8)(micro(4-)O)(4) core of 1-4 and the antiferromagnetic units contained in the minerals ferrihydrite and maghemite is demonstrated by X-ray and M?ssbauer data. 相似文献
86.
Chakraborty I Baran P Sanakis Y Simopoulos A Fachini E Raptis RG 《Inorganic chemistry》2008,47(24):11734-11737
A formally Fe(III)(7)Fe(II) complex, containing an inner Fe(4)O(4)-cubane and four peripheral Fe centers, is derived from the one-electron reduction of its Fe(III)(8) precursor. Spectroscopic analysis of the former reveals that the redox activity of this Fe(8) system is confined within its cubane core. The resulting (Fe(4)O(4))(3+)-cubane, which is valence-delocalized in the NMR, M?ssbauer, and IR spectroscopy time scales but valence-trapped in the X-ray photoelectron spectroscopy (XPS) time scale, is better described as a Robin-Day class-II system by the analysis of its near-infrared (NIR) intervalence charge transfer (IVCT) band profile. 相似文献
87.
Chakraborty T Chakraborty I Moulik SP Ghosh S 《The journal of physical chemistry. B》2007,111(10):2736-2746
The interaction between pepsin and CTAB has been elaborately studied with a number of techniques. The enzyme-induced interaction produced complexes, aggregates, and micelles of CTAB with distinct physicochemical features. It was found that at very low surfactant concentration (much below the critical micellar concentration (cmc) of pure CTAB), the surfactant got adsorbed both in monomeric and lower aggregated forms to the high-energy sites of the native biopolymer, leading to enhanced hydrophobicity of the combine, and hence, lowering of the interfacial (air/solution) tension. This was followed by the formation of a faintly turbid solution of the polymer-surfactant coacervate. The CTAB interacted unfolded pepsin along with the surfactant monomer remained adsorbed at the interface to decrease the interfacial tension (gamma) to a low level to produce a break in the gamma vs log [CTAB] plot prior to the normally observed extended cmc (cmce) in presence of polymers. The cac-like aggregation (as observed in tensiometry and viscometry) was not found in conductometry and microcalorimetry, whereas microcalorimetry evidenced the formation of the cmce of CTAB in the presence of the biopolymer. The CTAB influenced structural features of the pepsin were assessed from spectral, viscometric, and circular dichroism measurements. 相似文献
88.
Indranil Biswas 《Archiv der Mathematik》2007,88(2):164-172
Let T be a complex torus and E
T
a holomorphic principal T-bundle over a connected complex manifold M. We prove that the total space of E
T
admits a K?hler structure if and only if M admits a K?hler structure and E
T
admits a flat holomorphic connection whose monodromy preserves a K?hler form on T. If E
T
admits a K?hler structure, then
is isomorphic to
.
Received: 2 September 2005 相似文献
89.
Frolova LV Evdokimov NM Hayden K Malik I Rogelj S Kornienko A Magedov IV 《Organic letters》2011,13(5):1118-1121
Privileged medicinal scaffolds based on the structures of tetra- and pentasubstituted 2-aminopyrroles were prepared via one-pot multicomponent reactions of structurally diverse aldehydes and N-(aryl-, hetaryl-, alkylsulfonamido)acetophenones with activated methylene compounds. This methodology was used in a four-step synthesis of alkaloids rigidins A, B, C, and D in overall yields of 61%, 58%, 60%, and 53%, respectively. Of these, rigidins B, C, and D were synthesized for the first time. 相似文献
90.