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991.
Boris Remenec Silvia Dulanská Veronika Pau?ová L’ubomír Mátel 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(2):403-407
This paper describes a simple and rapid method of 99Tc pre-concentration, separation and purification by using AnaLig? Tc02 gel in two stages or AnaLig? Tc02 gel in a first stage and TEVA? resin in a second stage, which are commercially available from IBC advanced technologies, Inc. and Eichrom technologies,
Inc., respectively. The method is suitable for analyzing large volume concentrate samples in a relatively short time. The
use and effectiveness of AnaLig? Tc02 and Eichrom’s TEVA? resin were successfully tested by analysis of evaporator concentrate samples which belong to the class of most difficult
matrices to analyze. 相似文献
992.
A novel concept of an alternating current (AC) dielectrophoretic filter with a three-dimensional electrode array is presented. A filter is constructed by winding into layers around the core tube two sheets of woven metal wire-mesh with several sheets of woven insulating wire-mesh sandwiched in between. Contrary to conventional dielectrophoretic devices, the proposed design of electrodes generates a high-gradient field over a large working volume by applying several hundred volts at a standard frequency of 60?Hz. The operating principle of filtration is based on our recently developed method of AC dielectrophoretic gating for microfluidics. The filtration efficiency is expressed in terms of two non-dimensional parameters, which describe the combined influence of the particle polarizability and size, the oil viscosity and flow rate, and the field gradient on the particle captivity. The proof-of-concept is tested by measuring the single-pass performance of two filters on positively polarized particles dispersed in engine oil: spherical glass beads, fused aluminum oxide powder, and silicon metal powder, all smaller than the mesh opening. The results obtained are used to consider the potential of using AC dielectrophoretic filtration and provide critical design guidelines for the development of a filter based on the retention capability of challenge particles. 相似文献
993.
Noeen Malik Boris D. Zlatopolskiy Christoph Solbach Wolfgang Voelter Sven N. Reske Hans-Jürgen Machulla 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(2):563-569
In this work, we tested the applicability of several methyl substituted benzyl groups as an alternative to the methyl group
for the protection of the hydroxyl groups in the nucleophilic aromatic radiofluorination. As a model synthesis, the no-carrier-added
(n.c.a.) preparation of 2-[18F]fluoro-3-hydroxy-6-methylpyridine from O-protected 3-hydroxy-6-methyl-2-nitropyridine was chosen. Conditions for acidolytic
and hydrogenolytic cleavage of heteroaryl esters were studied. Among various protecting groups tested, 4-methylbenzyl and
2,4-dimethylbenzyl groups proved to be the best by resulting in about 70% yields of [18F]-labelled product after hydrolysis with 32% HCl at 120 °C for 10 min. Furthermore, 4-methylbenzyl ester cleaved readily
under catalytic transfer hydrogenation condition using ammonium formate and 10% Pd/C in boiling methanol to give 2-[18F]fluoro-3-hydroxy-6-methylpyridine in radiochemical yield of 75% within a reaction time of 10 min. Conditions for the cleavage
of both 4-methylbenzyl and 2,4-dimethylbenzyl esters are well suited for the implementation into an automated synthesis module. 相似文献
994.
This review describes the evolution of important concepts related to potential drops at interfaces in electrochemical systems. The role of the thermodynamic theory of electrocapillarity of perfectly polarizable electrodes in the development of interfacial electrochemistry is emphasized. A critical analysis of the phenomenological models of the electrical double layer on ideally polarizable electrodes is given. Certain trends in studying solid electrodes with well-defined surfaces brought into contact with electrolyte solutions are summarized. Attention is drawn to several unsolved problems crucial for the future development of electrochemical surface science. Finally, some recent experimental data are analyzed for selected models. 相似文献
995.
996.
Lebedeva IV Knizhnik AA Popov AM Lozovik YE Potapkin BV 《Physical chemistry chemical physics : PCCP》2011,13(13):5687-5695
The van der Waals corrected first-principles approach (DFT-D) is for the first time applied for investigation of interlayer interaction and relative motion of graphene layers. A methodological study of the influence of parameters of calculations with the dispersion corrected and original PBE functionals on characteristics of the potential relief of the interlayer interaction energy is performed. Based on the DFT-D calculations, a new classical potential for interaction between graphene layers is developed. Molecular dynamics simulations of relative translational vibrations of graphene layers demonstrate that the choice of the classical potential considerably affects dynamic characteristics of graphene-based systems. The calculated low values of the Q-factor for these vibrations Q≈ 10-100 show that graphene should be perfect for the use in fast-responding nanorelays and nanoelectromechanical memory cells. 相似文献
997.
Steric control on the redox chemistry of (η5-C9H7)2Yb(II)(THF)2 by 6-aryl substituted iminopyridines
Trifonov AA Shestakov BG Gudilenkov ID Fukin GK Giambastiani G Bianchini C Rossin A Luconi L Filippi J Sorace L 《Dalton transactions (Cambridge, England : 2003)》2011,40(40):10568-10575
A steric control on the reductive capacity of ytterbocenes towards iminopyridine ligands is described. The reaction of (η(5)-C(9)H(7))(2)Yb(THF)(2) with a series of 6-organyl-2-(aldimino)pyridyl ligands (IPy) takes place with the replacement of two THF molecules by one IPy unit. In contrast to the rich reductive ytterbocene chemistry described in the presence of the unsubstituted (aldimino)pyridyl ligand, all 6-aryl substituted IPys scrutinized hereafter are involved into the metal coordination as neutral bidentate {N,N} or tridentate {N,N,S; N,N,O} ligands, with no changes of the metal oxidation state in the final complexes. A series of Yb(II) metallocene complexes of general formula (η(5)-C(9)H(7))(2)Yb(II)(η(2) or η(3))[2,6-(i)Pr(2)(C(6)H(3))N=CH(C(5)H(3)N)-6-R)] have been isolated and completely characterized. The stereo-electronic role of the aryl substituents in the IPy ligands on the ytterbocene redox chemistry has also been addressed. 相似文献
998.
Dry EF Clegg JK Breiner B Whitaker DE Stefak R Nitschke JR 《Chemical communications (Cambridge, England)》2011,47(21):6021-6023
A new dicopper(I) complex is reported that can be incorporated into extended architectures through multitopic carboxylate linkers; reversible carboxylate templation under pH control led to the formation of [2+2] and [3+3] metallomacrocycles. 相似文献
999.
Błażewska KM Haiges R Kashemirov BA Ebetino FH McKenna CE 《Chemical communications (Cambridge, England)》2011,47(22):6395-6397
Under certain conditions, the phosphonocarboxylate analogue (3) of the bisphosphonate drug minodronate (4) in contact with borosilicate glassware reversibly forms an isolable dimer complex of boron, as revealed by the X-ray crystallographic structure of the (R,R/S,S) complex and supported by NMR and HRMS data. 相似文献
1000.
Schmidt EY Zorina NV Dvorko MY Protsuk NI Belyaeva KV Clavier G Méallet-Renault R Vu TT Mikhaleva AI Trofimov BA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(11):3069-3073
BODIPYrrole: A general strategy for the design of novel BODIPY fluorophores based on pyrroles with polycondensed aromatic and metallocene substituents has been developed. The strategy involves the acylation of the condensed substituent and treatment of the acylated derivative (as oxime) with acetylene in MOH/DMSO (M = alkali metal) to give pyrroles that were then used for assembly of the BODIPY fluorophores (see scheme). 相似文献