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231.
Maury O Viau L Sénéchal K Corre B Guégan JP Renouard T Ledoux I Zyss J Le Bozec H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(18):4454-4466
A series of D3 (Fe(II), Ru(II), Zn(II), Hg(II)) and D2d (Cu(I), Ag(I), Zn(II)) octupolar metal complexes featuring different functionalized bipyridyl ligands has been synthesized, and their thermal, linear (absorption and emission), and nonlinear optical (NLO) properties were determined. Their quadratic NLO susceptibilities were determined by harmonic light scattering at 1.91 microm, and the molecular hyperpolarizability (beta0) values are in the range of 200-657 x 10(-30) esu for octahedral complexes and 70-157 x 10(-30) esu for tetrahedral complexes. The octahedral zinc(II) complex 1 e, which contains a 4,4'-oligophenylenevinylene-functionalized 2,2'-bipyridine, exhibits the highest quadratic hyperpolarizability ever reported for an octupolar derivative (lambdamax=482 nm, beta1.91(1 e)=870 x 10(-30) esu, beta0(1 e)=657 x 10(-30) esu). Herein, we demonstrate that the optical and nonlinear optical (NLO) properties are strongly influenced by the symmetry of the complexes, the nature of the ligands (donor endgroups and pi linkers), and the nature of the metallic centers. For example, the length of the pi-conjugated backbone, the Lewis acidity of the metal ion, and the increase of ligand-to-metal ratio result in a substantial enhancement of beta. The contribution of the metal-to-ligand (MLCT) transition to the molecular hyperpolarizability is also discussed with respect to octahedral d6 complexes (M=Fe, Ru). 相似文献
232.
The electrochemical reduction processes of [Fe(H_2O)_3(NCS)_3] (18-C-6) have been studied in nonaqueous media by method of cyclic voltammetry and spectroelec-trochemistry at an optical transparent thin layer electrode. The formal potential, E°′, electron transfer number, n, diffusion cofficient, D_O, formal heterogeneous electron transfer rate constant, k_S′, and electrochemical transfer coefficient, a, are deter-minated. Significant effect of solvents on the electrochemical behaviors has been observed. The higher the β, the higher the thermodynamic and kinetic stabilities of the coordination compound resulted. 相似文献
233.
The structures of B32 and B32H2–32 with Ih symmetry have been investigated by means of ab initio calculations at STO-3G level. The relationship between molecular orbitals of them has been analyzed and their bonding properties have been discussed. Then the possibility of their existence, as well as the similarity and difference between B32 (B32H2–32) and C60 (C60H60) have been inferred. 相似文献
234.
235.
Summary Two new cyclodextrin (CD) derivatives, heptakis{2,6-di-O-pentyl-3-O-[3′-(2″-chloro-4″,5″-dioxylmethene)-phenyl-5′-iso-oxazolylmethyl]}-β-CD
(CD I) and heptakis{2,6-di-O-methyl-3-O-[3′-(2″-chloro)-phenyl-5′-iso-oxazolylmethyl]}-β-CD (CD II) were synthesized and coated
on fused-silica capillary columns. Their chromatographic characteristics, including column efficiency, polarity, selectivity
and phase transition were studied and compared with similar β-CD stationary phases. It was found that the heterocycle group
has a significant effect on the selectivity of the CD stationary phases. Both stationary phases can be successfully used to
separate many di- and trisubstituted benzene positional isomers and show stronger separation ability in separating low-polarity
benzene positional isomers than other β-CD stationary phases. 相似文献
236.
稀土高氯酸盐开环冠醚三缩乙二醇(EO_3)[La(C_6H_(14)O_4)_3(H_2O)](ClO_4)_3·H_2O,单斜晶系,P2_1/c空间群。晶胞参数为:a=15.474(2),b=11.386(1),c=20.841(4),β=99.82(1)°,V=3618(1),MoKα,Z=4,D_c=1.718g/cm3,μ=1.499mm ̄(-1)。全矩阵最小二乘精细修正,结构因子R=0.056,R_w=0.083。中心原子La与开环冠醚醚链上的O(1)~O(9)及一个水分子形成10配位双帽四方反棱柱结构。弱配体高氯酸根不参加配位。 相似文献
237.
[reaction: see text] Reported herein is a strategy employing a Mukaiyama reaction in tandem with a hydrogen transfer reaction for the elaboration of 2,3-anti-3,4-anti and 2,3-anti-3,4-syn propionate motifs. The mode of complexation is controlled through monodentate or chelate pathways for the Mukaiyama reaction to give access to either syn or anti aldol products, precursors of the free-radical reduction reaction. Boron Lewis acid is used to control the free-radical reaction through the exocyclic pathway. 相似文献
238.
A new series of vanadates with the general formula M Ba2V3O11, where M may be Bi, In, or a rare earth, has been synthesized and structurally characterized by single crystal X-ray diffraction and powder X-ray diffraction. The general formula may be rewritten as M Ba2(VO4)(V2O7) to emphasize that there is one orthovanadate group and one pyrovanadate group in each formula unit. Up to one-third of the vanadium may be replaced by phosphorous, leading to the general formula M Ba2V2PO11. However, phosphorous shows no preference between the ortho and pyro groups. Both M Ba2V3O11 and M Ba2V2PO11 crystallize in the monoclinic system with the space group P21/c and Z = 4. The cell parameters from single crystal X-ray data of BiBa2V3O11 are a = 12.332(4) Å, b = 7.750(4) Å, c = 11.279(4) Å, β = 103.22(3)°, V = 1049(1) Å3; and for BiBa2PO11 are a = 12.266(2) Å, b = 7.615(2) Å, c = 11.312(2) Å, β = 103.32(2)°, V = 1028.2(2) Å3. The Bi atom coordinates to six oxygen atoms forming a distorted octahedron, and the edge sharing of BiO6 octahedra results in a BiO4 chain along the b axis. There are two types of Ba atoms with coordination numbers of 10 and 11. There are three types of tetrahedral (T) atoms in these structures. The nonequivalent T atoms of the pyro group give T-O-T angles of 167 and 171° in BiBa2V3O11 and BiBa2V2PO11, respectively. Isostructural M Ba2V3O11 compounds were prepared in which M is In, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Lu. 相似文献
239.
Summary A method of obtaining the asymptotic solution of a singularly perturbed system containing singular manifolds is presented. Some sufficient conditions for the convergence of the solutions to the stable singular manifolds are provided. An example from magneto-hydrodynamics, showing interesting properties of the solution, is given. 相似文献
240.