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71.
Coherent Dynamics of Direct-Current-Driven Quantum-Dot-Array with Two Time-Dependent Embedded Impurities 下载免费PDF全文
The coherent dynamics of dc-driven quantum-dot array with two embedded time-dependent impurities is investigated, the exact crossings and avoided crossings in the quasienergies are associated with the evolution dynamics of the electron by the introduction of the envelope lines of the site's maximum returning probability. Through a perturbative scheme, the time-dependent Hamiltonian is replaced by an equivalent static one, whose structure reveals the new quantum tunnelling mechanism in the time-periodic driving system and sheds light on the alternative interpretation of dynamic localization and delocalization. 相似文献
72.
73.
We consider a collective insurance risk model with a compound Cox claim process, in which the evolution of a claim intensity
is described by a stochastic differential equation driven by a Brownian motion. The insurer operates in a financial market
consisting of a risk-free asset with a constant force of interest and a risky asset which price is driven by a Lévy noise.
We investigate two optimization problems. The first one is the classical mean-variance portfolio selection. In this case the
efficient frontier is derived. The second optimization problem, except the mean-variance terminal objective, includes also
a running cost penalizing deviations of the insurer’s wealth from a specified profit-solvency target which is a random process.
In order to find optimal strategies we apply techniques from the stochastic control theory. 相似文献
74.
75.
α-Bromoacrylates, α-bromoacrylonitrile and diethyl alkylidenemalonates all react with bromoform and base under phase transfer conditions to give dibromocycloprapanes. When γ-bromine is present in a crotonate or an alkylidenemalonate, the intermediate derived by Michael addition of tribromomethylanion is trapped by cyclisation at that position to produce a (tribromomethyl)cyclopropane. 相似文献
76.
Anthony C. Jones Neil D. Gerrard David J. Cole-Hamilton A.Kenneth Holliday J.B. Mullin 《Journal of organometallic chemistry》1984,265(1):9-15
Electrolysis of methylmagnesium chloride or dimethylmagnesium in tetrahydrofuran (thf) with an indium anode yields the spectroscopically characterised adduct Me3In · thf directly; the adducts Me3In · L (L = NEt3, PMe3, PEt3) are obtained by direct addition of excess L to Me3In · thf. 相似文献
77.
78.
Four new amine-templated materials, containing two-dimensional lithium beryllofluoride sheets of the stoichiometry [LiBeF(4)](-), have been synthesised under hydrothermal and ambient pressure conditions. [LiBeF(4)][C(6)H(4)(CH(3))CH(2)NH(3)] (1), [LiBeF(4)][C(6)H(4)CH(2)NH(3)Cl] (2), [LiBeF(4)](2)[NH(3)CH(2)CH(2)CH(2)NH(3)] (3), and [LiBeF(4)][C(6)H(5)CH(2)CH(2)CH(2)NH(3)] (4) all contain well-separated anionic sheets containing two different topologies with the 'inter-layer' regions comprising of organoamine templating species. Use of the different organoamine templating agents results in compounds possessing very different relative arrangements of the lithium beryllofluoride sheets. The materials crystallise in P-centred orthorhombic and monoclinic cells; for 1 (templating agent: 3-methylbenzylamine) Pca2(1); for 2 (4-chlorobenzylamine) Pbca; for 3 (1,3-diamminopropane) Pccn, and for 4 (3-phenyl-1-propylamine) P2(1)/c. Hydrogen bonding exists between ions situated on the protonated amine groups on the templating species and electronegative fluoride ions, on MF(4) tetrahedra (where M=Li and Be). 相似文献
79.
Aleisha A. McLachlan Kulbir Singh D. Gerrard Marangoni 《Colloid and polymer science》2010,288(6):653-663
The conformation and orientation of a series of zwitterionic surfactants (the alkyl-N,N-dimethylammoniopropanesulfonates, or Zwittergent® Detergents) has been studied via 13C chemical shift measurements and 2D NOESY spectroscopy. Chemical shift changes (Δδ values) support the tendency for the intercharge arm to adopt a ring-like orientation as the alkyl chain length increases. Protons of the headgroup regions for both the 8 carbon and the 10 carbon Zwittergent® appear to form a greater number of intermolecular interactions with headgroups of neighboring monomers in the micelle. Interactions between the end of the alkyl chain and the headgroup region of the 12 carbon Zwittergent® are also apparent from examination of the NOESY spectrum indicating that the tail folds back towards the surface of the micelle. These results indicate that a combination of the ring-like conformation of the intercharge arm along with crowding in the vicinity of the sulfonate group could explain why ZW3-12 appears to behave more as a cationic surfactant in previously studied mixed micellar systems. 相似文献
80.
使用均苯三甲酸与碳酸镍在水热条件下反应得到了一例新的二维双层Ni(II)配位聚合物Ni3(BTC)2(μ-H2O)26H2O。二维层包含syn-syn羧酸桥和水桥连接的三核Ni3单元,进一步用均苯三甲酸上的苯环连接成二维层状结构。磁性研究表明,相邻Ni2+离子间存在弱的铁磁耦合作用。水桥连镍离子的桥联键角为122.8(3)deg,所以通过该水桥镍离子间应该呈现反铁磁耦合。因此,实验结果证明了syn-syn羧酸桥传递铁磁耦合,而且铁磁耦合大于反铁磁作用,最终配合物呈弱的铁磁耦合。基于本工作和文献报道的含syn-syn 羧酸混合桥联镍配合物的磁性,我们总结出下面结论:Ni–O–C–O–Ni的共面性与否决定了配合物的磁性。共面性好的Ni–O–C–O–Ni导致中等强度的反铁磁耦合,而共面性差会消弱反铁磁作用,甚至出现由反铁磁变为铁磁耦合。标题配合物中羧酸桥所传递的铁磁性可能就归因于Ni–O–C–O–Ni的不共平面性。因此,与含羧酸桥的混合桥联双核铜(II)配合物类似,轨道补偿效应(the orbital complementary effect (OCE))对于解释水/羧酸混合桥联镍(II)配合物的磁性也同样适用。 相似文献