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161.
En route to conformationally restricted analogues of nicotine and anabasine, a novel synthetic route to bridged anabasines is described that hinges on a domino intramolecular [4 + 2]-cycloaddition/ring opening-elimination sequence of 3-amino-substituted furo[3,4-c]pyridines. Extension of this route to bridged nicotines, however, proved abortive, even when the dienophile tether is activated by a p-tolylsulfonyl group or when the diene moiety is activated by an electron-releasing methoxy substituent. A detailed density functional theoretical study (B3LYP/6-31+G) was undertaken to provide insight into the factors that facilitate an intramolecular Diels-Alder reaction in the former case. 相似文献
162.
Monisha Singha Manasi Maji Manish Gupta Srijoni Majhi Amit Basak 《Tetrahedron letters》2019,60(14):945-947
Garratt-Braverman (GB) cyclization, two CC bond forming reaction in a single step, has been utilized to construct several isoindoline and phthalan derivatives. The precursors were the bispropargyl protected amines and ethers with one of the propargyl arm substituted with an alkene moiety. The GB cyclizations were generally carried out in presence of DBU in refluxing toluene. In case of the bispropargyl amine systems with the alkene arm substituted with electron withdrawing ester group, the cyclization occurred at room temperature. The yields of cyclization ranged from 64 to 86% which are acceptable considering the formation of two CC bonds. The protected isoindolines could be successfully deprotected by treatment with thiophenol in presence of triethyl amine and the corresponding free amines were isolated as the TFA salts. 相似文献
163.
A series of mono-N-functionalized 1,4,8-trimethyl-1,4,8,11-tetraazacyclotetradecanes 3 – 14 were synthesized by alkylating the secondary N-atom of the macrocycle 1 . The spectral properties of the Cu2+ complexes, studied under different pH conditions, are discussed in relation to the possibility of coordination of the donor group of the side chain to the axial position of the metal ion and to the effect of the length of the side chain. 相似文献
164.
We construct almost periodic conoidal wave solutions toSO(2,1)-model field theory with the help of a periodic inverse problem suggested by Dote. The solutions can be explicitly constructed in terms of Riemann functions. 相似文献
165.
ABSTRACTStopping cross sections (SCS) for protons, alphas and Li ions are calculated with a modified form of our earlier work by incorporating a different electron density distribution of target materials; this involves four parameters – two projectile dependent and the rest two remain fixed. The prosed model has been tested for three stripped ion (H+, He2 + and Li3 +) projectiles and found that it describes quite satisfactorily the experimental SCS data from low energies with projectile velocities nearing v = Z1v0 (with Z1 as the atomic number and v0 the Bohr velocity) up to 100.0 MeV over a wide range of stopping media with atomic numbers Z2 =3–100. 相似文献
166.
A carbon-terminated interrupted Nazarov reaction is described. The trimethylsilyl enol ethers derived from propargyl vinyl ketones undergo selective proton transfer at the distal acetylenic carbon atom to provide allenyl vinyl ketones as transient intermediates. In the presence of indoles, a cascade of reactions is initiated that converts the initially formed pentadienyl cations to cyclopentenones bearing a quaternary alpha carbon atom. 相似文献
167.
Subhra Basak Soma Sen Samiran Mitra C. Marschner W. S. Sheldrick 《Structural chemistry》2008,19(1):115-121
Abstract Two new square planar Cu(II) and Ni(II) complexes, [CuL1(NCO)] (1) and [NiL2(N3)] (2) have been synthesized with two different tridentate N2O donor Schiff base ligands L
1
H (1:1 condensation product of benzoylacetone and 2-diethylaminoethylamine) and L
2
H (1:1 condensation product of benzoylacetone and 2-dimethylaminoethylamine), respectively. Both the complexes 1 and 2 have been characterized by elemental analysis, IR, UV-Vis spectroscopy, room temperature magnetic susceptibility measurement,
electrochemical, thermal, and single crystal X-ray diffraction studies. Structural studies reveal that in both the complexes
metal centers have square planar environment with N2O donor set of Schiff base ligands and terminal pseudohalide anions (isocyanate for 1 and azide for 2) at four coordination sites of square plane.
Graphical abstract
Square planar complexes of Cu(II) and Ni(II) with N
2
O donor set of two Schiff base ligands: synthesis and structural aspects
Subhra Basak, Soma Sen, Samiran Mitra, C. Marschner, W. S. Sheldrick
Two new square planar Cu(II) and Ni(II) complexes, [CuL1(NCO)] (1) and [NiL2(N3)] (2) have been synthesized with two different tridentate N2O donor Schiff base ligands L
1
H and L
2
H respectively. Both the complexes 1 and 2 have been characterized by elemental analysis, IR, UV-Vis
spectroscopy, room temperature magnetic susceptibility measurement, electrochemical, thermal and single crystal X-ray diffraction
studies.
相似文献
168.
Tathagata Basak 《Geometriae Dedicata》2010,147(1):357-387
We define and study a class of finite topological spaces, which model the cell structure of a space obtained by gluing finitely many Euclidean convex polyhedral cells along congruent faces. We call these finite topological spaces, combinatorial cell complexes (or c.c.c). We define orientability, homology and cohomology of c.c.c’s and develop enough algebraic topology in this setting to prove the Poincaré duality theorem for a c.c.c satisfying suitable regularity conditions. The definitions and proofs are completely finitary and combinatorial in nature. 相似文献
169.
Nonlinear Dynamics - We present a detailed study of Rayleigh–Bénard magnetoconvection with periodic gravity modulation and uniform vertical magnetic field. Linear stability analysis is... 相似文献
170.
The two macrocycles 1-(2-aminoethyl)- and 1-[2-(dimethylamino)ethyl]-4, 8, 11-trimethyl-1, 4, 8, 11-tetraazacyclotetradecane, 1 and 2 , respectively, and their metal complexes with Co2+, Ni2+ and Cu2+ were prepared. The different spectral properties of the complexes with these two ligands can be rationalized by assuming that, in the case of 1 , the amino group of the pendant arm is axially coordinated to the metal ion giving a pentacoordinate structure, whereas the dimethylamino group of 2 cannot bind because of sterical hindrance. This is also corroborated by the observation that the complexes of 2 react with unidentate ligands such as N and SCN? to give ternary species MLX+, whereas those of 1 do not. This indicates that the complexes of 1 have no free coordination site, their coordination sphere being completely saturated by the five N-atoms of the macrocycle, whereas the complexes of 2 having a vacant site still can add an unidentate ligand. 相似文献