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71.
Milios CJ Inglis R Vinslava A Prescimone A Wernsdorfer W Parsons S Perlepes SP Christou G Brechin EK 《Chemical communications (Cambridge, England)》2007,(26):2738-2740
The spin ground state of a [Mn(III)(6)Mn(II)(2)] cluster has been deliberately switched from S = 1 to S = 7 upon designed ligand substitution. 相似文献
72.
George C. Kaspentakis Constantinos A. Tsoleridis Julia Stephanidou‐Stephanatou 《Journal of heterocyclic chemistry》2007,44(2):425-430
The reaction of 3‐formylchromone‐N‐benzoylhydrazone with ketenes, prepared in situ from the corresponding acid chlorides 2a‐d and the mixed anhydride 2e was studied. In all cases 2‐(4′‐oxo‐4′H‐3′‐chromyl)‐5‐phenyl‐2,3‐dihydro‐1,3,4‐oxadiazoles ( 3 ) were isolated in yields varying from 40 to 80%. A full structure assignment of all products has been made on the basis of 1D and 2‐D (COSY H‐H, COSY C‐H, COLOC C‐H) NMR spectra. A plausible reaction mechanism is also proposed based on theoretical approaches and experimental results. 相似文献
73.
74.
Konstantinos Lambropoulos Konstantinos Kaklamanis Georgios Georgiadis Constantinos Simserides 《Annalen der Physik》2014,526(5-6):249-258
A non conventional source or receiver of THz and above THz electromagnetic radiation is proposed. Specifically, electron or hole oscillations in DNA dimers (two interacting DNA base‐pairs or monomers) are predicted, with frequency in the range 0.25–100 THz (period 10–4000 fs) i.e. potentially absorbing or emitting electromagnetic radiation mainly in the mid‐ and far‐infrared with wavelengths ≈ 3–1200 μm. The efficiency of charge transfer between the two monomers which make up the dimer is described with the maximum transfer percentage p and the pure maximum transfer rate . For dimers made of identical monomers , but for dimers made of different monomers . The investigation is extended to DNA trimers (three interacting DNA base‐pairs or monomers). For trimers made of identical monomers the carrier oscillates periodically with 0.5–33 THz ( 30–2000 fs); for 0 times crosswise purines , for 1 or 2 times crosswise purines . For trimers made of different monomers the carrier movement may be non periodic. Generally, increasing the number of monomers above three, the system becomes more complex and periodicity is lost; even for the simplest tetramer the carrier movement is not periodic. 相似文献
75.
76.
Binns M de Visser SP Theodoropoulos C 《Journal of chemical information and modeling》2012,52(2):577-588
The study of pharmacophores, i.e., of common features between different ligands, is important for the quantitative identification of "compatible" enzymes and binding species. A pharmacophore-based technique is developed that combines multiple conformations with a distance geometry method to create flexible pharmacophore representations. It uses a set of low-energy conformations combined with a new process we call bound stretching to create sets of distance bounds, which contain all or most of the low-energy conformations. The bounds can be obtained using the exact distances between pairs of atoms from the different low-energy conformations. To avoid missing conformations, we can take advantage of the triangle distance inequality between sets of three points to logically expand a set of upper and lower distance bounds (bound stretching). The flexible pharmacophore can be found using a 3-D maximal common subgraph method, which uses the overlap of distance bounds to determine the overlapping structure. A scoring routine is implemented to select the substructures with the largest overlap because there will typically be many overlaps with the maximum number of overlapping bounds. A case study is presented in which 3-D flexible pharmacophores are generated and used to eliminate potential binding species identified by a 2-D pharmacophore method. A second case study creates flexible pharmacophores from a set of thrombin ligands. These are used to compare the new method with existing pharmacophore identification software. 相似文献
77.
Dr. Lipeng Zhai Dr. Siwen Cui Boli Tong Prof. Weihua Chen Dr. Zijie Wu Prof. Constantinos Soutis Prof. Donglin Jiang Prof. Guangshan Zhu Prof. Liwei Mi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(26):5784-5788
Covalent organic frameworks (COFs) enable precise integration of various organic building blocks into porous skeletons through topology predesign. Here, we report the first example of COFs by integrating electron withdrawing bromine group onto the skeletons for triboelectric nanogenerators (TENG). The resulting framework exhibits high surface area and good crystallinity. Thus, the bromine functionalized COF has more regular aligned π columns and arrays over the skeleton than bare COFs, which in turn significantly enhances charge transport ability. As a result, bromine functionalized COFs showed higher electrical output performance at 5 Hz with a peak value of short circuit current density of 43.6 μA and output voltage of 416 V, which is 2 and 1.3 times higher than those of bare COFs (21.6 μA and 318 V), respectively. These results demonstrated that this strategy for engineering electron withdrawing groups on the skeleton could open a new aspect of COFs for developing TENG devices. 相似文献
78.
Dr. Júlia Mayans Dr. Constantinos C. Stoumpos Dr. Mercé Font-Bardia Prof. Albert Escuer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(49):11158-11169
An anionic hexanuclear NiII metallamacrocycle with endo and exo linking sites has been employed as a building block to generate a series of capsules and bowls of nanometric size. The supramolecular arrangement of the {Ni6} rings was tailored by the size of the alkali cations, showing the transition from {Ni6-M2-Ni6} capsules (M=LiI and NaI) to {Ni6-M} bowls (M=KI and CsI). The alkyl co-cations are determinant to stabilize the assemblies by means of CH⋅⋅⋅π interactions on the exo side of the metallamacrocycles. The effect on the topology of the supramolecular assemblies of the cation size, cation charge, Et3NH+ or Me4N+ counter cations has been analyzed. Magnetic measurements reveal the presence of ferromagnetic and antiferromagnetic interactions inside the rings that allow a S=0 ground state. 相似文献
79.
Christos Raptis Ioannis N. Lykakis Dr. Constantinos Tsangarakis Dr. Manolis Stratakis Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(44):11918-11927
Based on stereoisotopic studies and β‐secondary isotope effects, we propose that the acid‐catalyzed cyclization of geranyl acetate proceeds through a concerted mechanism. Under heterogeneous conditions (zeolite Y confinement), a preorganized chairlike transition state predominates, whereas under homogeneous conditions the boat‐ and chairlike transition states are almost isoenergetic. For the case of farnesyl acetate, we propose that under homogeneous conditions a concerted dicyclization occurs with a preorganized boat–chair transition state competing with the chair–chair transition state. Under zeolite confinement conditions, the chair–chairlike dicyclization transition state is highly favorable. The preference of chairlike transition states within the cavities of zeolite Y is attributed to a transition state shape selectivity effect. 相似文献
80.
Gass IA Milios CJ Whittaker AG Fabiani FP Parsons S Murrie M Perlepes SP Brechin EK 《Inorganic chemistry》2006,45(14):5281-5283
The microwave-assisted reaction of Fe(O2CMe)2 with salicylaldoxime (saoH2) in pyridine produces an octametallic cluster in crystalline form in 2 min. The core describes a cube encapsulated in a tetrahedron, while sao2- exhibits a novel coordination mode. 相似文献