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91.
García G Timón V Hernández-Laguna A Navarro A Fernández-Gómez M 《Physical chemistry chemical physics : PCCP》2011,13(21):10091-10099
Density Functional Theory has been used to study the structural, electronic and charge-transport properties of two regio-regular head-to-tail polythiophene derivatives, i.e. poly(3-hexyl-thiophene), P3HT, and poly(3-oxyhexyl-thiophene), P3OHT. The effect of substituents on the electronic structure was analyzed by means of bandwidth, bandgap, effective mass, total and partial densities of states and crystal orbital overlap populations. Electronic couplings were estimated from band diagrams as the splitting of the valence band. The neutral and cationic states of isolated oligomers were optimized using the supercell approximation. The hole-transfer rates and mobilities were evaluated according to Marcus's theory. Results provide a compelling illustration of the effect of side chains on the crystal packing, electronic structure and charge-transport properties. Thus, the hole mobility calculated for the alkyl derivative was 0.15 cm(2) V(-1) s(-1) (experimental mobility is 0.10 cm(2) V(-1) s(-1)), while the alkoxy derivative has a theoretical mobility of 0.49 cm(2) V(-1) s(-1). The obtained results hopefully could motivate experimentalists to try out P3OHT for an improved charge carrier mobility. 相似文献
92.
Bravo I Díaz-de-Mera Y Aranda A Moreno E Nutt DR Marston G 《Physical chemistry chemical physics : PCCP》2011,13(38):17185-17193
Density Functional Theory (DFT) has been used with an empirically-derived correction for the wavenumbers of vibrational band positions to predict the infrared spectra of several fluorinated esters (FESs). Radiative efficiencies (REs) were then determined using the method of Pinnock et al. and these were used with atmospheric lifetimes from the literature to determine the direct global warming potentials of FESs. FESs, in particular fluoroalkylacetates, alkylfluoroacetates and fluoroalkylformates, are potential greenhouse gases and their likely long atmospheric lifetimes and relatively large REs, compared to their parent HFEs, make them active contributors to global warming. Here, we use the concept of indirect global warming potential (indirect GWP) to assess the contribution to the warming of several commonly used HFEs emitted from the Earth's surface, explicitly taking into account that these HFEs will be converted into the corresponding FESs in the troposphere. The indirect GWP can be calculated using the radiative efficiencies and lifetimes of the HFE and its degradation FES products. We found that the GWPs of those studied HFEs which have the smallest direct GWP can be increased by 100-1600% when taking account of the cumulative effect due to the secondary FESs formed during HFE atmospheric oxidation. This effect may be particularly important for non-segregated HFEs and some segregated HFEs, which may contribute significantly more to global warming than can be concluded from examination of their direct GWPs. 相似文献
93.
Ringkøbing Fjord is a large and shallow brackish lagoon on the west coast of Denmark that has gone through two environmental regime shifts in recent decades. Different intervention strategies, including nutrient abatement and the construction of facilities to increase the water exchange between the lagoon and the outside sea, have been proposed to achieve good water quality in terms of trophic state and conditions for waterfowl. The selection of an intervention strategy is a complex decision-making problem in which several conflicting objectives, like costs of application and environmental or social impacts, must be taken into account simultaneously. We propose a PC-based decision support system, called the Generic Multi-Attribute Analysis system, to deal with such interdisciplinary analyses. It evaluates the intervention strategies by means of an additive multiattribute utility model accounting for imprecision of the various components of the analysis, such as intervention strategy performances and decision-makers’ preferences. Also, it implements what is known as decision making with partial information, through the application of Monte Carlo simulation techniques. This enables a straightforward analysis of the difference between an anthropocentrist and an ecocentrist view of the problem, from which a final recommendation can be reached. 相似文献
94.
Reactivity with Amines of Bis(cyanamide) and Bis(cyanoguanidine) Complexes of the Iron Triad 下载免费PDF全文
Treatment of bis(cyanamide) [M(N≡CNEt2)2L4](BPh4)2 and bis(cyanoguanidine) [M{N≡CN(H)C(NH2)=NH}2L4](BPh4)2 complexes [M = Fe, Ru, Os; L = P(OEt)3] with an excess of amine RNH2 (R = nPr, iPr) affords mixed‐ligand complexes with cyanamide and amine [M(NH2R)(N≡CNEt2)L4](BPh4)2 ( 1a – 5a ) and [M(NH2R){N≡CN(H)C(NH2)=NH}L4](BPh4)2 ( 1b , 2b ). The complexes were characterized by spectroscopy and X‐ray crystal structure determination of [M(NH2iPr)(N≡CNEt2){P(OEt)3}4](BPh4)2 [M = Ru ( 3a ), Os ( 5a )]. 相似文献
95.
The optimization for function in computational design requires the treatment of, often competing, multiple objectives. Current algorithms reduce the problem to a single objective optimization problem, with the consequent loss of relevant solutions. We present a procedure, based on a variant of a Pareto algorithm, to optimize various competing objectives in protein design that allows reducing in several orders of magnitude the search of the solution space. Our methodology maintains the diversity of solutions and provides an iterative way to incorporate automatic design methods in the design of functional proteins. We have applied our systematic procedure to design enzymes optimized for both catalysis and stability. However, this methodology can be applied to any computational chemistry application requiring multi-objective combinatorial optimization techniques. 相似文献
96.
Benign‐by‐Design Solventless Mechanochemical Synthesis of Three‐, Two‐, and One‐Dimensional Hybrid Perovskites 下载免费PDF全文
Alexander D. Jodlowski Dr. Alfonso Yépez Prof. Rafael Luque Prof. Luis Camacho Prof. Gustavo de Miguel 《Angewandte Chemie (International ed. in English)》2016,55(48):14972-14977
Organic–inorganic hybrid perovskites have attracted significant attention owing to their extraordinary optoelectronic properties with applications in the fields of solar energy, lighting, photodetectors, and lasers. The rational design of these hybrid materials is a key factor in the optimization of their performance in perovskite‐based devices. Herein, a mechanochemical approach is proposed as a highly efficient, simple, and reproducible method for the preparation of four types of hybrid perovskites, which were obtained in large amounts as polycrystalline powders with high purity and excellent optoelectronics properties. Two archetypal three‐dimensional (3D) perovskites (MAPbI3 and FAPbI3) were synthesized, together with a bidimensional (2D) perovskite (Gua2PbI4) and a “double‐chain” one‐dimensional (1D) perovskite (GuaPbI3), whose structure was elucidated by X‐ray diffraction. 相似文献
97.
L. Desdin O. Dominguez J. Moreno L. Alfonso M. Rodriguez 《Journal of Radioanalytical and Nuclear Chemistry》1995,199(4):305-308
Determination of boric acid in high nickel content solutions during nickel cathode production was made by measuring the transmission loss of thermal neutrons. According to industrial requirements, adequate accuracy and reproducibility were obtained. 相似文献
98.
Barone V Bloino J Monti S Pedone A Prampolini G 《Physical chemistry chemical physics : PCCP》2011,13(6):2160-2166
Classical all-atom molecular dynamics (MD) simulations and quantum mechanical (QM) time-dependent density functional theory (TD-DFT) calculations are employed to study the conformational and photophysical properties of the first emitter excited state of tetramethyl-rhodamine iso-thiocyanate fluorophore in aqueous solution. For this purpose, a specific and accurate force field has been parameterised from QM data to model the fluorophore's first bright excited state. During the MD simulations, the consequences of the π→π* electronic transition on the structure and microsolvation sphere of the dye has been analysed in some detail and compared to the ground state behaviour. Thereafter, fluorescence has been calculated at the TD-DFT level on configurations sampled from the simulated MD trajectories, allowing us to include time dependent solvent effects in the computed emission spectrum. The latter, when compared with the absorption spectrum, reproduces well the experimental Stokes shift, further validating the proposed multilevel computational procedure. 相似文献
99.
We introduce a new method to study compact spaceliken-submanifolds in de Sitter spacesS
q
n+q
by means of certain integral formulas which have a very clear geometric meaning. As a first application of them we obtain
a Bernstein type result for complete maximal submanifolds inS
q
n+q
. As for surfaces, we also get a uniqueness result for compact spacelike surfaces inS
q
2+q
with parallel mean curvature vector field.
Partially supported by a DGICYT Grant No. PB91-0705-C02-02
Partially supported by a DGICYT Grant No. PB91-0731 相似文献
100.