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71.
72.
Artem L. Gushchin Bee‐Lean Ooi Pernille Harris Pavel A. Abramov Maxim N. Sokolov 《无机化学与普通化学杂志》2019,645(4):398-401
The aqueous solution chemistry of niobium is underexplored, and well characterized aqua complexes are scarce. In this contribution, a new niobium aqua complex was obtained by treatment of Zn‐reduced ethanolic solution of NbCl5 with HCl in the presence of a selenide source (ZnSe). This is the first example of selenium containing aqua complex of niobium. The yellow‐green aqua complex was isolated by cation‐exchange chromatography and transformed into corresponding isothiocyanate complex by ligand exchange, which was crystallized as (PyH)4.5[H1.5Nb4SeO5(NCS)10] · 0.5H2O. X‐ray structural analysis revealed a metal‐metal bonded tetranuclear {Nb4(μ4‐Se)(μ2‐O)5}4+ core with a capping μ4‐Se ligand. 相似文献
73.
Divya Iyer Vaqar M. S. Syed Samanvaya Srivastava 《Journal of polymer science. Part A, Polymer chemistry》2021,59(22):2895-2904
The addition of monovalent salts to polyelectrolyte complexes (PECs) comprising oppositely charged polyelectrolytes results in diminishing propensity for complexation, leading to complexes with higher water contents and lower moduli. However, the corresponding influence of multivalent ions on polyelectrolyte complexation has not yet been explored beyond enhanced screening effects. Here, we elucidate the significant impact of the valency of the salt cation on the composition, ion partitioning, and viscoelasticity of charge-matched PECs comprising sodium salt of poly(acrylic acid) and poly(allylamine hydrochloride). Notably, preferential partitioning of divalent cations (Ca2+ and Sr2+) into the complexes is observed, in stark contrast to the depletion of monovalent ions (Na+) from the complexes. Concomitantly, electrostatic bridging of polyanion chains by divalent ions is found to hinder their relaxation, manifesting as a non-monotonic evolution of the shear moduli of the complexes with increasing divalent salt concentrations. Relatedly, a failure of time-salt and time-ionic strength superposition approaches in presence of divalent ions is demonstrated, highlighting the nontrivial influence of these ions on chain relaxation behavior. 相似文献
74.
Beneficiation of low-grade iron ore was carried out by selective flocculation process using different flocculants, namely starch amylopectin (AP) and grafted copolymer of amylopectin (GAP). The iron ore used in the investigation contained 56.98% Fe, 5.45% Al2O3, and 4.22% SiO2. Flocculant dosage, number of floc washing, and pH were considered as variable parameters to analyze their effect on the performance of grade and recovery of concentrate. A flocculant dosage of 0.4?mg/g was found to be the optimum condition for the sample and variable parameters under investigation. The investigation indicated that a grade of 64.77% Fe can be obtained with 96% recovery using AP; however, GAP showed the better result for Fe grade (67%) with a recovery of 97%. 相似文献
75.
Fred B. Stocker Melissa A. Troester Doyle Britton 《Journal of chemical crystallography》2000,30(6):389-397
Four complexes of CuCN with imidazoles have been prepared by adding the ligand to a solution of CuCN in aqueous sodium thiosulfate. The imidazole ligands used were 2-methylimidazole (mim), 1,2-dimethylimidazole (dmim), 5-chloro-1-methylimidazole (clmim), and 2-phenylimidazole (phim). Complex 1, (CuCN)(mim) is monoclinic, C2/c, a = 9.565(3), b = 7.764(5), c = 8.983(8) Å, = 96.76(3)°, Z, = 4, Complex 2, (CuCN)(dmim) is monoclinic, P21/c, a = 8.120(2), b = 11.796(4), c = 16.375(9) Å, , = 100.87(4)°, Z = 8. Complex 3, (CuCN) (clmim) is monoclinic, C2/c, a = 24.907(4), b = 6.894(5), c = 18.259(4) Å, = 102.79(2)°, Z = 16. Complex 4, (CuCN)(phim) is orthorhombic, Pca21, a = 9.204(4), b = 8.125(2), c = 26.304(6) Å, Z, = 8. Complexes 1, 2, and 4 have one-dimensional chains –Cu–CN–Cu– with an imidazole bonded to each Cu. Complex 3 has a two-dimensional sheet of CuCN, again with an imidazole bonded to each Cu. In 1 the imidazole group is disordered by a two-fold rotation approximately around the N···N direction in the imidazole group. In 3 one of the imidazole groups has a disorder involving exchange of the Cl and CH3. 相似文献
76.
BAI Yan PAN Xiao-Jing DANG Dong-Bin② SHANG Wei-Li WANG Jing-Ping 《结构化学》2008,27(6):673-676
A new one-dimensional polymeric complex [Cd(SCN)2(H2O)]L (L = N,N′-bis(furan- 2-ylmethylene)hydrazine) has been synthesized and characterized by IR, UV spectra, TG-DTA technique and single-crystal X-ray diffraction analysis. It crystallizes in triclinic, pace group P1^- with a = 5.9268(8), b = 10.8678(15), c = 13.3671(19) A, α = 109.295(2), β = 95.092(2), γ = 97.8580(10)°, V = 796.70(19)A^3, Z = 2, C12H10CdN4O3S2, Mr = 434.76, μ = 1.648 mm^-1, Dc = 1.812 g/cm^3, F(000) = 428, R = 0.0308 and wR = 0.0769. The crystal structure reveals that the structure of [Cd(SCN)2(H2O)]n features di-μ-1,3-thiocyante bridges and 1D chains. The octahedrally coordinated Cd atom is surrounded by one oxygen atom from water molecule, three S atoms and two N atoms from five di-μ-1,3 thiocyanato bridges. The Cd atoms are connected by two di-μ-1,3 thiocyanato bridges with the Cd(1)…Cd(1A) separation of 4.239(1) A and Cd(1)...Cd(1B) of 5.852(1)/~. In addition, the one-dimensional straight chain structure is further connected by multiform intermolecular N-H…O hydrogen bonds and π-π interactions to form a three-dimensional supramolecular structure. 相似文献
77.
Associating polymers are hydrophilic long-chain molecules containing a small amount of hydrophobic groups. The aqueous solutions
show viscoelastic responses above some critical concentrations because a three-dimensional structure is formed by association
of hydrophobic groups. When the associating polymers are added to silica suspensions at low concentrations, the flocculation
is induced by bridging mechanisms, and the flow of suspensions become shear-thinning. For suspensions prepared with polymer
solutions in which the associating network is developed, the viscosity decreases, shows a minimum, and then increases with
increasing particle concentration. The viscosity decrease may arise from the breakdown of associating network due to adsorption
of polymer chains onto the silica surfaces. As the particle concentration is increased, the polymer concentration in solution
is decreased, and finally, all polymer chains are adsorbed on the surfaces. Beyond this point, the partial coverage of particle
surfaces takes place and strong interactions are generated between particles by polymer bridging. Since the stable suspensions
are converted to highly flocculated systems, the viscosity is increased and the flow becomes shear-thinning. The concentration
effect of silica particles on the viscosity behavior of suspensions can be explained by a combination of viscosity decrease
in solution due to polymer adsorption and viscosity increase due to flocculation. 相似文献
78.
Otsuki J Imai A Sato K Li DM Hosoda M Owa M Akasaka T Yoshikawa I Araki K Suenobu T Fukuzumi S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(9):2709-2718
A star-shaped Ru/Os tetranuclear complex, in which a central Os unit is linked to three peripheral Ru units by 4,4'-azobis(2,2'-bipyridine) (azobpy) bridging ligands, was prepared to examine the unique photodynamics regulated by its redox state. The Ru/Os tetranuclear complex exhibits Ru-based luminescence at 77 K, whereas the three-electron reduction (one for each azobpy) of the Ru/Os complex results in luminescence from the Os unit. The photoexcited state of the Ru/Os complex rapidly decays into low energy metal-to-ligand charge-transfer states, in which the excited electron is localized in the azobpy ligand in the form of azobpy(.-). Upon the one-electron reduction of the azobpy ligands, the above-mentioned low-energy states become unavailable to the photoexcited complex. As a result, an energy transfer from the Ru-based excited state to the Os-based excited state becomes possible. Ultrafast transient absorption measurements revealed that the energy transfer process consists of two steps; intramolecular electron transfer from the terminal bipyridine ligand (bpy(.-)) to form azobpy(2-) followed by a metal-to-metal electron transfer. Thus, the Ru/Os tetranuclear complex collects light energy into the central Os unit depending on the redox state of the bridging ligands, qualifying as a switchable antenna. 相似文献
79.
E. I. Mayboroda Yu. L. Slominsky A. V. Turov A. I. Tolmachev 《Chemistry of Heterocyclic Compounds》2008,44(1):78-85
Tetramethylene-2,2′-bis(1,3,3-trimethyl-(3H)-indolium),-3-ethylbenzothiazolium,-1-methyl-quinolinium, and-1-methyl-and-1-butylbenz[c,d]indolium
salts were synthesized starting from them trimethinecyanines containing an ethylene bridging group in the α, α′-positions
of the chromophore have been prepared. These compounds are converted to their analogs containing a vinylene group by the action
of benzoquinones. In the case of thiacarbocyanines the effect of the indicated bridging groups on the conformation and protonation
route of the carbocyanines has been studied. The chromaticity of the dyes has been investigated.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 94–102, January, 2008. 相似文献
80.
Kazem Barati William Clegg Mohammad Hossein Habibi Ross W. Harrington Arash Lalegani Morteza Montazerozohori 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(3):239-242
Transition metal complexes of Schiff base ligands have been shown to have particular application in catalysis and magnetism. The chemistry of copper complexes is of interest owing to their importance in biological and industrial processes. The reaction of copper(I) chloride with the bidentate Schiff base N,N′‐bis(trans‐2‐nitrocinnamaldehyde)ethylenediamine {Nca2en, systematic name: (1E,1′E,2E,2′E)‐N,N′‐(ethane‐1,2‐diyl)bis[3‐(2‐nitrophenyl)prop‐2‐en‐1‐imine]} in a 1:1 molar ratio in dichloromethane without exclusion of air or moisture resulted in the formation of the title complex μ‐chlorido‐μ‐hydroxido‐bis(chlorido{(1E,1′E,2E,2′E)‐N,N′‐(ethane‐1,2‐diyl)bis[3‐(2‐nitrophenyl)prop‐2‐en‐1‐imine]‐κ2N,N′}copper(II)) dichloromethane sesquisolvate, [Cu2Cl3(OH)(C20H18N4O4)2]·1.5CH2Cl2. The dinuclear complex has a folded four‐membered ring in an unsymmetrical Cu2OCl3 core in which the approximate trigonal bipyramidal coordination displays different angular distortions in the equatorial planes of the two CuII atoms; the chloride bridge is asymmetric, but the hydroxide bridge is symmetric. The chelate rings of the two Nca2en ligands have different conformations, leading to a more marked bowing of one of the ligands compared with the other. This is the first reported dinuclear complex, and the first five‐coordinate complex, of the Nca2en Schiff base ligand. Molecules of the dimer are associated in pairs by ring‐stacking interactions supported by C—H…Cl interactions with solvent molecules; a further ring‐stacking interaction exists between the two Schiff base ligands of each molecule. 相似文献