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71.
Sherif El-Basil Gani Jashari Jan V. Knop Nenad Trinajstić 《Monatshefte für Chemie / Chemical Monthly》1984,115(11):1299-1312
The reduced graph model, when used in conjunction with the search trees method, provides a novel combinatorial procedure for the enumeration and generation ofKekulé structures. The procedure is suited for large benzenoid hydrocarbons consisting of cata- and thin peri-condensed parts.
Zur Anwendung des Reduced Graph Model im Zusammenhang mit Search Trees zur Ermittlung der Anzahl möglicherKekulé-Strukturen
Zusammenfassung Das Modell erlaubt mit der im Titel genannten Kombination eine neuartige Methode zur Ermittlung und Generierung vonKekulé-Strukturen. Das Verfahren ist für große benzoide Kohlenwasserstoffe geeignet, die aus cata- und (dünnen) peri-kondensierten Teilstrukturen bestehen.相似文献
72.
具有超大通道结构的介孔氧化硅柱层状钛酸的合成和催化应用初探 总被引:6,自引:0,他引:6
A mesoporous (d=2.3mm) silica-pillared layered tetratitanate with a super gallery (d001=1.84mm)was prepared by first preswelling layered tetratitanate with n-dodecyl amine, then reacting with 20wt% NH2(CH2)3Si(OC2H5)3 aqueous solution, and finally calcinating the resultant solid product in air at 550℃. All the reaction was carried out hydrothermally in an autoclave at 130℃. The obtained material has a relatively high BET surface area of 204m2·g-1 and a thermal stability beyond 600℃. The catalytic application of the material was also investigated by using the dehydration of isopropanol and the reform of n-hexane as two probing reactions. 相似文献
73.
Pentaazadienido Complexes of Zinc, Cadmium, and Mercury. The Crystal Structure of [Cd(EtOC6H4-N5-C6H4OEt)2(py)2] and [Hg(tol-N5-tol)2(py)] The pentaazadienido complexes [M(EtOC6H4N5C6H4OEt)2] (M = Zn ( 1 ), Cd ( 2 )) are formed by the reaction of [M(NH3)4]2+ with [EtOC6H4N5C6H4OEt]? in aqueous ammonia. 2 crystallizes from pyridine as [Cd(EtOC6H4N5C6H4OEt)2py2] ( 3 ) with the triclinic space group P1 and a = 937.2(2); b = 1422.7(2); c = 2085.5(2) pm; α = 75.28(1)°; β = 94.74(1)°; γ = 99.75(1)°; Z = 2. The central Cd2+ ion of 3 exhibits an octahedral coordination by two pyridine ligands in cis arrangement and two (N1, N3)-2+ chelating pentaazadienide ions. The reaction of [HgI4]2 with the 1,5-di(tolyl)pentaazadienide anion in aqueous ammonia affords [Hg(p-tol-N5-tol)2] ( 4 ), which crystallizes from pyridine in form of [Hg(tol-N5-tol)2py] ( 5 ) with the space group P1 and a = 1176.2(4); b = 1203.1(3); c = 1295.6(5) pm; α = 100.77(3)°; β = 110.08(3)°; γ = 94.29(2)°; Z = 2. In 5 the Hg2+ cation is threefold coordinated by two monodentate (N3)-η1 pentaazadienid anions and one pyridine ligand. Within the N5 chains of the pentaazadienid anions of 3 and 5 localized N? N double bonds are found in the positions N1? N2 and N4? N5 with distances between 125 and 129 pm. 相似文献
74.
Dynamical Behaviour of Linear Molecular Anions in the Hydrogensulfides of Sodium, Potassium and Rubidium: Differential Scanning Calorimetry, X-ray and Neutron Diffraction Hydrogensulfides of the alkali metals M ? Na, K, Rb were prepared in autoclaves by the reaction of the corresponding metals with H2S and D2S, respectively, in the temperature range from 50°C to 150°C. Differential scanning calorimetry, X-ray and neutron diffraction methods reveal that both, the HS?-and DS?-compounds occur in three crystalline modifications with HT ? high-, MT ? medium- and LT ? low-temperature form: The temperatures and enthalpies for the changes of modifications of the H- and D-compounds are given and the atomic arrangements revealed mainly by neutron diffraction data are discussed, in relation to, for example, size of cations. 相似文献
75.
Christopher T Burns 《Journal of organometallic chemistry》2003,683(1):240-248
The reaction of (hexyl)HC(mim)2 (1, mim=N-methyl-imidazol-2-yl) with (cod)PdMeCl in C6H6 yields {(hexyl)HC(mim)2}Pd(Me)Cl (3). The photochemical reaction of 3 with CH2Cl2 at 23 °C in ambient room light yields {(hexyl)HC(mim)2}Pd(CHCl2)Cl (4). It is proposed that this reaction proceeds by homolytic scission of the PdMe bond of 3. 相似文献
76.
选用四种不同的密度泛函理论方法(B3LYP,B3P86,BLYP,BP86),在全电子的双ξ加极化加弥散函数基组(DZP )下,对SinH/SinH^-(n=3~8)体系进行研究,获得它们的基态结构和电子亲合能。预测Si3H/Si3H^-,Si4H/Si4H^-,Si5H/Si5H^-,Si6H/Si6H^-,Si7H/Si7H^-和Si8H/Si8H^-的基态结构分别为C2v(^2B2)/C2v(1^A1)氢桥结构,Cs(^2A’)/C(^1A’),C2v(^2B2)/C2v(^1A1),C2v(^2B2或^2B1)/C4v(^1A1),C5v(^2A1)/C5v(^1A1)和C5(^2A‘‘)/C3v(^1A1)。在电子亲合能方面,B3LYP方法预测的电子亲合能是最可靠的,预测Si3H,Si4H,Si5H,Si6H,Si7H和Si8H的电子亲合能分别为2.56,2.59,2.84,2.86,3.19和3.14eV。 相似文献
77.
Khuloud Takrouri Israel Goldberg Morris Srebnik 《Journal of organometallic chemistry》2005,690(18):4150-4158
The first examples of diborane (4) compounds derived from amine cyanoboranes are described. A series of monobromo derivatives of amine cyanoboranes (A:BHBrCN), and dibromo derivatives (A:BBr2CN), 1-7, were prepared. Lithiation of the monobromo derivative of trimethylamine cyanoborane, using n-BuLi, did not produce the C-lithiated intermediate Li+ [CH2NMe2BHBrCN]−, but instead the B-lithiated intermediate Li+ [Me3NBHCN]−, was obtained. This intermediate, when allowed to react for 16 h, coupled with the un-lithiated trimethylamine monobromocyanoborane (Me3NBHBrCN) and resulted in diborane (4) derivative formation as the 2LiBr complex. The same result was obtained when one equiv of the trimethylamine monobromocyanoborane was added to the reaction mixture 1 h after lithiation. Following the same procedure, novel diborane (4) derivatives of amine cyanoboranes were successfully obtained, 8-11, as their 2LiBr complexes from the monobromo derivatives of the corresponding amine cyanoboranes. Molecular structures of the trimethylamine dibromocyanoborane, 6, and the triethylamine dibromocyanoborane, 7, were determined using X-ray crystallography. 相似文献
78.
分别用MNDO和AM1两种半经验方法,对C59F2nHN (n = 1, 2) 的异构体进行几何构型全优化,结合频率分析及HF/6-31G单点能计算,确定了各异构体的基态结构及其相对稳定性。计算结果表明,C59HN的F加成物的立体选择性规律与C60的不同,最稳定异构体不是1-2加成物。C59F2HN的最稳定异构体是1-4加成的6, 18-或12, 15-异构体; C59F4HN的最稳定异构体是1-4,1-4加成的6, 18; 12, 15-异构体,其能量远小于其它各异构体的能量。N原子取代碳笼骨架C原子后,改变了碳笼F加成物的立体选择性规律。 相似文献
79.
The structures, energies, and natural atomic charges of 2-dimethylaminophenol oxide, 2-Me2N-(O)C6H4OH, and 2-dimethylphosphinylphenol, 2-Me2P(O)C6H4OH, in three different conformations were computed at the ab initio MP2/6-31G* level. Computed natural charges indicate distributions of electron density in amine oxides and phosphine oxides that are quite different from what is normally assumed on the basis of the formal charges in the usual representations of these compounds. The charges on nitrogen and phosphorus in these compounds are typically computed to be approximately zero on nitrogen and +2 on phosphorus, and the oxygen is considerably more negative in the phosphine oxide than in the amino oxide. Electronegativity differences thus play a larger role and formal charges a smaller one in determining atomic charges in these compounds than is generally believed. Despite the more negative oxygen in phosphine oxides, amine oxides are computed to be considerably more basic when participating in hydrogen bonding. Calculations treating the computed natural charges on these six conformations as point charges for classical approximations of the coulombic energies support the idea that the quantum mechanically computed relative energies are largely determined by coulombic interactions. 相似文献
80.
《Annals of Pure and Applied Logic》2022,173(10):103108
Probabilistic team semantics is a framework for logical analysis of probabilistic dependencies. Our focus is on the axiomatizability, complexity, and expressivity of probabilistic inclusion logic and its extensions. We identify a natural fragment of existential second-order logic with additive real arithmetic that captures exactly the expressivity of probabilistic inclusion logic. We furthermore relate these formalisms to linear programming, and doing so obtain PTIME data complexity for the logics. Moreover, on finite structures, we show that the full existential second-order logic with additive real arithmetic can only express NP properties. Lastly, we present a sound and complete axiomatization for probabilistic inclusion logic at the atomic level. 相似文献