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931.
Izumi H Yamagami S Futamura S Nafie LA Dukor RK 《Journal of the American Chemical Society》2004,126(1):194-198
The odd-even effect of chiral alkyl alcohols, (S)-CH(3)CHOHC(n)()H(2)(n)()(+1) (n = 2-8), in solution state has been observed spectroscopically for the first time. The vibrational circular dichroism (VCD) bands at 1148 cm(-)(1) exhibit a clear odd-even effect. The observed VCD bands of (R)-(-)-2-hexanol correspond well to those predicted (population weighted). Density functional theory calculations indicate that the most prevalent conformations in solution are the all-trans forms. The odd-even effect of the VCD bands is ascribed to the alternating terminal methyl motions in the alkyl chains relative to fixed motions near the chiral center in the trans conformations. The conformational sensitivity of VCD for the chiral alcohols in the solution state may be useful for the design of liquid crystals and ligands in the future. 相似文献
932.
A Zinc Phthalocyanine Based Periodic Mesoporous Organosilica Exhibiting Charge Transfer to Fullerenes 下载免费PDF全文
Dr. Florian Auras Dr. Yan Li Dr. Florian Löbermann Dr. Markus Döblinger Dr. Jörg Schuster Prof. Laurence M. Peter Prof. Dr. Dirk Trauner Prof. Dr. Thomas Bein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):14971-14975
Periodic mesoporous organosilica (PMO) materials offer a strategy to position molecular semiconductors within a highly defined, porous network. We developed thin films of a new semiconducting zinc phthalocyanine‐bridged PMO exhibiting a face‐centered orthorhombic pore structure with an average pore diameter of 11 nm. The exceptional degree of order achieved with this PMO enabled us to create thin films consisting of a single porous domain throughout their entire thickness, thus providing maximal accessibility for subsequent incorporation of a complementary phase. The phthalocyanine building blocks inside the pore walls were found to be well‐aggregated, enabling electronic conductivity and extending the light‐harvesting capabilities to the near IR region. Ordered 3D heterojunctions capable of promoting photo‐induced charge transfer were constructed by impregnation of the PMO with a fullerene derivative. When integrated into a photovoltaic device, the infiltrated PMO is capable of producing a high open‐circuit voltage and a considerable photocurrent, which represents a significant step towards potential applications of PMOs in optoelectronics. 相似文献
933.
Experimental data are presented for the solubility in water of benzoic and toluic acids from 5° to 65°C. From the solubility the molality of the monomeric form of the acid is calculated using literature data for both ionization and dimerization of the acid. These data for the monomer combined with data from the literature for vaporization of the solid and ionization in both the gas phase and the aqueous phase yield entropy and enthalpy changes for the solvation of molecular and anionic forms of the acid. A similar procedure is also applied to literature data for the solubility of benzene in water. It is shown that the hydration entropies of the monomeric forms are a linear function of their partial molar volumes. It is concluded that hydration of the undissociated o-toluic acid may be crucial to the increased acidity of that acid compared to benzoic acid. 相似文献
934.
Laurence J. Hardwick Michael Holzapfel Alexander Wokaun Petr Novk 《Journal of Raman spectroscopy : JRS》2007,38(1):110-112
Raman spectroscopy was performed on various mixtures of the ionic liquid salt, 1‐ethyl‐3‐methylimidazolium‐bis(trifluoromethylsulfonyl)imide (EMI‐TFSI). When EMI‐TFSI is used in combination with a lithium salt, it could be a potential electrolyte for lithium‐ion or lithium metal batteries. The Raman spectra of EMI‐TFSI, EMI‐TFSI 0.5 M Li‐TFSI, EMI‐TFSI 0.5 M Li‐TFSI 2 M vinylene carbonate (VC) and EMI‐TFSI 0.5 Li‐TFSI 2 M ethylene carbonate (EC) were collected and compared. A comparison of the peak positions of the δs CF3 mode at 742 cm−1 demonstrates that when carbonate additives are present, the lithium ion is no longer interacting with the TFSI anion. Instead, it is coordinated with the carbon–oxygen double bond of the carbonates. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
935.
E. E. Vdovin Yu. N. Khanin P. L. Shabelnikova L. Eaves M. Henini 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(8):1124-1126
Study of split-gate structures, in which self-assembled InAs quantum dots (QDs) are located near the region of 2D electron gas, has revealed Coulomb oscillations in the dependence of the tunnel current through a limited number of InAs QDs in a channel on the gate voltage, which correspond to the excited states of QDs with opposite spins. The Coulomb oscillations of the current were observed up to a temperature of ~20 K. The Coulomb energy ΔE C was found to be 12.5 meV, a value corresponding to the theoretical estimates for p states of QDs in our experimental structures. 相似文献
936.
Lot-sizing with production and delivery time windows 总被引:3,自引:0,他引:3
Laurence A. Wolsey 《Mathematical Programming》2006,107(3):471-489
We study two different lot-sizing problems with time windows that have been proposed recently. For the case of production
time windows, in which each client specific order must be produced within a given time interval, we derive tight extended
formulations for both the constant capacity and uncapacitated problems with Wagner-Whitin (non-speculative) costs. For the
variant with nonspecific orders, known to be equivalent to the problem in which the time windows can be ordered by time, we
also show equivalence to the basic lot-sizing problem with upper bounds on the stocks. Here we derive polynomial time dynamic
programming algorithms and tight extended formulations for the uncapacitated and constant capacity problems with general costs.
For the problem with delivery time windows, we use a similar approach to derive tight extended formulations for both the constant
capacity and uncapacitated problems with Wagner-Whitin (non-speculative) costs.
We are most grateful for the hospitality of IASI, Rome, where part of this work was carried out. The collaboration with IASI
takes place in the framework of ADONET, a European network in Algorithmic Discrete Optimization, contract n MRTN-CT-2003-504438.
This text presents research results of the Belgian Program on Interuniversity Poles of Attraction initiated by the Belgian
State, Prime Minister's Office, Science Policy Programming. The scientific responsibility is assumed by the authors. 相似文献
937.
The magnetic susceptibility and low-temperature magnetization curve of the [3 x 3] grid [Mn(III)4Mn(II)5(2poap-2H)6](ClO4)10.10 H2O (1) are analyzed within a spin Hamiltonian approach. The Hilbert space is huge (4,860,000 states), but the consequent use of all symmetries and a two-step fitting procedure nevertheless allows the best-fit determination of the magnetic exchange parameters in this system from complete quantum mechanical calculations. The cluster exhibits a total spin S = 1/2 ground state; the implications are discussed. 相似文献
938.
Laurence M. Peter 《Journal of Solid State Electrochemistry》2013,17(2):315-326
Light-driven water-splitting (photoelectrolysis) at semiconductor electrodes continues to excite interest as a potential route to produce hydrogen as a sustainable fuel, but surprisingly little is known about the kinetics and mechanisms of the reactions involved. Here, some basic principles of semiconductor photoelectrochemistry are reviewed with particular emphasis on the effects of slow interfacial electron transfer at n-type semiconductors in the case of light-driven oxygen evolution. A simple kinetic model is outlined that considers the competition between interfacial transfer of photogenerated holes and surface recombination. The model shows that, if interfacial charge transfer is very slow, the build-up of holes at the surface will lead to substantial changes in the potential drop across the Helmholtz layer, leading to non-ideal behavior (Fermi level pinning). The kinetic model is also used to predict the response of photoanodes to chopped illumination and to periodic perturbations of illumination and potential. Recent experimental results obtained for α-Fe2O3 (hematite) photoanodes are reviewed and interpreted within the framework of the model. 相似文献
939.
Abdallah Chahadih Hicham El Hamzaoui Rémy Bernard Laurence Bois Franc Beclin Odile Cristini Bruno Capoen Mohamed Bouazaoui 《Journal of nanoparticle research》2011,13(12):6507-6515
Direct space-selective growth of PbS nanoparticles, embedded inside a transparent porous sol–gel derived silica matrix, has
been achieved using continuous laser irradiation. Before the irradiation, the porous silica host has been soaked in a PbS
precursor solution. The effect of the concentration of PbS precursors and of the incident laser power on the mean particle
size was studied. Absorption spectroscopy, X-ray diffraction analysis, and TEM measurements were used to identify the PbS
crystallites inside the xerogel and to estimate the average particle size. It has been shown that PbS crystallite sizes range
between 3 and 13 nm depending on the PbS precursors concentration. 相似文献