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81.
应用以氢氧化物共沉淀为前驱体的高温固相烧结法合成LiNi1/3Mn1/3Co1/3O2正极材料,研究了沉淀温度及烧结过程锂盐投入量对该材料的结构和电化学性能的影响.结果表明,以室温(-20℃)下合成的氢氧化物为前驱体制备的LiNi1/3Mn1/3Co1/3O2具有较好的电化学性能.高温固相烧结会导致部分LiOH损失,因而在合成过程中需加入过量的氢氧化锂,实验表明Li1.08Ni1/3Mn1/3Co1/3O2材料的电化学性能最优. 相似文献
82.
O. G. Stradella S. A. Maluendes E. A. Castro A. H. Jubert 《Theoretical chemistry accounts》1987,72(1):57-62
By means of Bader's approach on topological properties of the electronic density, the major stability of the O-bonded adduct over the C-bonded one between MgF2 and CO is reinforced. 相似文献
83.
Zhong-Le Huang Wolfgang Bensch Hubert Ebert 《Journal of solid state chemistry》2004,177(10):3245-3253
The effect of substitution of the anion Te by Se in non-stoichiometric Cr5Te8 has been investigated with respect to its crystal structure, magnetic properties, and electronic structure. The compounds Cr(1+x)Q2 (Q=Te, Se; Te:Se=7:1; (1+x)=1.234(6), 1.264(6), 1.300(7)) were synthesized at elevated temperatures followed by quenching the samples to room temperature. The crystal structures have been refined with X-ray powder diffraction data with the Rietveld method in the trigonal space group with lattice parameters a=3.8651(1)-3.8831(1) Å and c=5.9917(2)-6.0528(2) Å. The structure is related to the NiAs structure with full and deficient metal layers stacking alternatively along the c-axis. The irreversibility in the field-cooled/zero-field-cooled magnetization suggests that the substitution effects of one Te by one Se is strong enough to cause cluster-glass behavior, from ferromagnetic Cr5Te8 to cluster-glass Cr(1+x)Q2. Non-saturation magnetizations at 5.5 T and the magnetic relaxation results further support the existence of cluster-glass behavior. Accompanying SPR-KKR (spin-polarized relativistic Korringa-Kohn-Rostoker) band structure calculations strongly support the observation that the Cr(1) sites are preferentially occupied by Cr atoms and predict that these compounds are metallic. Results for the spin-resolved DOS and magnetic moments on each crystallographic sites are presented. 相似文献
84.
Five different structures of CH5
+ and one structure of CH5
– are calculated using a gaussian basis both in the SCF approximation and with the inclusion of electron correlation in the independent electron pair approximation (IEPA). While on SCF level the C
sstructure of CH5
+ has to lowest energy, the energy difference between the C
sand C
2vstructures becomes negligible if correlation is included. In contrast to this the approach of a proton to CH4 at large and intermediate distances is most favorable towards a corner of the CH4 tetrahedron which means a structure. The decomposition of CH5
+ into CH3
+ and H2 requires 20kcal/mol on SCF level and 40 kcal/mol if correlation is included. 相似文献
85.
86.
Smirnov O. Yu. Churakov A. M. Tyurin A. Yu. Strelenko Yu. A. Ioffe S. L. Tartakovsky V. A. 《Russian Chemical Bulletin》2002,51(10):1849-1856
Nucleophilic substitution in nitro- and bromobenzo-1,2,3,4-tetrazine 1,3-dioxides (BTDOs) was studied. In most cases, the bromo and nitro groups are replaced by methylamino, dimethylamino, azido, and methoxy groups without opening of the tetrazine ring. It was illustrated with the reactions of dibromo-BTDOs with sodium methoxide that the reactivity of positions 5 to 8 in their benzene ring as regards nucleophilic substitution changes in the following order: 6 > 8 > 7 > 5. The structures of the BTDOs obtained were confirmed by 1H, 13C, and 14N NMR data. 相似文献
87.
The complexes between R3Tr (Tr = B, Al, and Ga; R = H, F, Cl, and Br) and H2X (X = O, S, and Se) were theoretically studied. The interaction energies of R3Al⋯H2X and R3Ga⋯H2X are consistent with the electronegativity of the halogen atom R (R ≠ H), but an opposite dependence is found for R3B⋯H2X. The triel bond of R3Tr⋯H2X is weaker for the heavier chalcogen donor. The dependence of triel bonding strength on the triel atom is complicated, depending on the nature of R and X. The methyl substitution of H2X causes a substantial increase in the interaction energy from −5.74 kcal/mol to −22.88 kcal/mol, and its effect is relevant to the nature of Tr, X, and R groups. For the S and Se donors, the increased percentage of interaction energy is almost the same due to the methyl substitution, which is larger than that of the O analogue. In most triel-bonded complexes, electrostatic dominates and polarization has comparable contribution. However, polarization plays a dominant role in R3B⋯ and R3B⋯ (R = Cl and Br; R′ = H and Me). 相似文献
88.
由于乙醇最有可能成为直接甲醇燃料电池(DMFC)的替代燃料,因此近年来。对乙醇的电化学氧化及直接乙醇燃料电池的研究已引起人们的很大兴趣。甲醇毒性较大并且易透过Nafion膜进入阴极造成阴极的混合电位而影响DMFC的阴极性能.这是制约DMFC走向实用化的主要问题之一。因此人们在致力于研究直接甲醇燃料电池的同时.也寻求其它的小分子醇作为甲醇的替代燃料。乙醇是除甲醇以外最简单的醇.它来源广泛.无毒,是可再生和环保型能源.并且也有较高的能量密度和反应活性。但是乙醇在电极上的完全氧化因涉及到C-C键的断裂要比甲醇困难.阳极反应动力学过程也比较缓慢。到目前为止铂基催化剂仍然是乙醇氧化最好的催化剂.虽然也有使用非铂催化剂研究乙醇的电氧化,但催化活性远不如铂基催化剂高。 相似文献
89.
T. N. Solomoichenko Yu. S. Sadovskii T. M. Prokop’eva E. A. Karpichev I. V. Kapitanov Zh. P. Piskunova V. A. Savelova A. F. Popov 《Theoretical and Experimental Chemistry》2006,42(6):364-370
We have studied the nucleophilicity of the hydroperoxide anion relative to 4-nitrophenyl diethyl phosphonate (NPDEPS) in the
presence of cetyltrimethylammonium bromide (water, 25 °C) while varying the acidity of the medium and the hydroperoxide anion
concentration over a broad range. The increase in the reaction rate when the reaction is transferred to a micellar pseudophase
is as high as ∼10-fold, which is explained by concentration effects. In CTAB micelles, as in water, the hydroperoxide ion
is one of the most effective α-nucleophiles, and the size of the α-effect, characterized by the ratio of the second-order rate constants for reactions of HOO− and OH− anions with NPDEPS, remains practically constant and reaches a value of ∼50-fold.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 6, pp. 357–363, November–December, 2006. 相似文献
90.
Yu. V. Tomilov I. V. Kostyuchenko E. V. Shulishov O. M. Nefedov 《Russian Chemical Bulletin》1998,47(4):666-668
The reaction of diazocyclopropane generatedin situ with vinyl bromide occurs as regioselective 1,3-dipolar cycloaddition to give 5-bromospiro(1-pyrazoline-3,1′-cyclopropane)
in ∼60% yield. Reactions of the latter with nucleophilic reagents, which can occur both with retention and opening of the
cyclopropane ring, were studied.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 688–690, April 1998. 相似文献