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排序方式: 共有264条查询结果,搜索用时 859 毫秒
31.
32.
In the present work, poly(glycidyl methacrylate-co-divinylbenzene) monoliths were synthesized and further derivatized to obtain strong anion exchange supports. Capillary monoliths (65 x 0.2 mm id) were prepared in situ by copolymerization of glycidyl methacrylate and divinylbenzene, employing 1-decanol and tetrahydrofuran as porogens. The free epoxy groups were derivatized in a two step synthesis to obtain quaternary ammonium functionalities. On testing the pressure stability of the synthesized monolith, a highly linear dependence between flow rate and pressure drop was obtained, indicating the high stability of the material even at high flow rates. The morphology of the copolymer was investigated by scanning electron microscopy. Mercury intrusion porosimetry showed a narrow pore size distribution, having a maximum at 439 nm. On recording a van Deemter plot the number of theoretical plates per meter was found to be 59324. The produced strong anion exchange monoliths turned out to be highly suitable for the separation of nucleotides and oligonucleotides. 相似文献
33.
34.
Kim S Cheng N Jeong JR Jang SG Yang SM Huck WT 《Chemical communications (Cambridge, England)》2008,(31):3666-3668
We report localized surface plasmon resonance (LSPR) of hexagonal Au nanodot arrays to detect changes in the thickness and conformation of poly[2-(methacryloyloxy)ethyltrimethyl ammonium chloride] (PMETAC) brushes. 相似文献
35.
In this paper the synthesis, optimisation and application of a silane based monolithic copolymer for the rapid separation of proteins and oligonucleotides is described. The monolith was prepared by thermal initiated in situ copolymerisation of trimethylsilyl-4-methylstyrene (TMSiMS) and bis(4-vinylbenzyl)dimethylsilane (BVBDMSi) in a silanised 200 microm I.D. fused silica column. Different ratios of monomer and crosslinker, as well as different ratios of micro- (toluene) and macro-porogen (2-propanol) were used for optimising the physical properties of the stationary phase regarding separation efficiency. The prepared monolithic stationary phases were characterised by measurement of permeability with different solvents, determination of pore size distribution by mercury intrusion porosimetry (MIP). Morphology was studied by scanning electron microscopy (SEM). Applying optimised conditions, a mixture comprised of five standard proteins ribunuclease A, cytochrome c, alpha-lactalbumine, myoglobine and ovalbumine was separated within 1 min by ion-pair reversed-phase liquid chromatography (IP-RPLC) obtaining half-height peak widths between 1.8 and 2.4 s. Baseline separation of oligonucleotides d(pT)(12-18) was achieved within 1.8 min obtaining half-height peak widths between 3.6 and 5.4 s. The results demonstrate the high potential of this stationary phase for fast separation of high-molecular weight biomolecules such as oligonucleotides and proteins. 相似文献
36.
Choi EY Azzaroni O Cheng N Zhou F Kelby T Huck WT 《Langmuir : the ACS journal of surfaces and colloids》2007,23(20):10389-10394
Cyclic voltammetry (CV) was employed to characterize the electrochemical behavior of polyelectrolyte brushes with immobilized electroactive counterions in response to external changes in concentration and composition of the supporting electrolyte and as a function of brush thickness. Poly(methacryloyloxy)ethyl-trimethyl-ammonium chloride (PMETAC) brushes were synthesized on Au substrates via atom transfer radical polymerization followed by ion-exchange with ferricyanide ions ([Fe(CN)6]3-) as redox probes. CV measurements of the modified PMETAC brushes showed the typical electrochemical response corresponding to a surface-confined electroactive species and the redox counterions, as [Fe(CN)6]3- species form stable ion pairs with the quaternary ammonium groups of the brush. The electron-transfer features of PMETAC brushes with different thicknesses, as characterized by CV and UV-vis spectroscopy, revealed that the charge density probed by CV was lower than the charge density measured by UV-vis spectroscopy. The electrode current decreased significantly with increasing concentration of supporting electrolyte due to the effect of the Donnan potential. Hydrophobic counterions, ClO4-, which induced brush collapse, lead to significantly reduced electrode currents. 相似文献
37.
A. O. Gattone D. Abriola F. T. Avignone R. L. Brodzinski J. I. Collar R. J. Creswick D. E. Di Gregorio H. A. Farach C. K. Gurard F. Hasenbalg H. Huck H. S. Miley A. Morales J. Morales S. Nussinov A. Ortiz de Solrzano J. H. Reeves J. A. Villar K. Zioutas The SOLAX Collaboration 《Nuclear Physics B - Proceedings Supplements》1999,70(1-3)
A new technique has been used to search for solar axions using a single crystal germanium detector. It exploits the coherent conversion of axions into photons when their angle of incidence satisfies a Bragg condition with a crystalline plane. The analysis of approximately 1.94 kg.yr of data from the 1 kg DEMOS detector in Sierra Grande, Argentina, yields a new laboratory bound on axion-photon coupling of gαγγ < 2.7 × 10−9GeV−1, independent of axion mass up to 1 keV. 相似文献
38.
D. Habs O. Kester T. Sieber H. Bongers S. Emhofer P. Reiter P.G. Thirolf G. Bollen J. Aystö O. Forstner H. Ravn T. Nilsson M. Oinonen H. Simon J. Cederkall F. Ames P. Schmidt G. Huber L. Liljeby O. Skeppstedt K.G. Rensfelt F. Wenander B. Jonson G. Nyman R. von Hahn H. Podlech R. Repnow C. Gund D. Schwalm A. Schempp K.-U. Kühnel C. Welsch U. Ratzinger G. Walter A. Huck K. Kruglov M. Huyse P. Van den Bergh P. Van Duppen L. Weissman A.C. Shotter A.N. Ostrowski T. Davinson P.J. Woods J. Cub A. Richter G. Schrieder 《Hyperfine Interactions》2000,129(1-4):43-66
The Radioactive Beam Experiment REX-ISOLDE [1–3] is a pilot experiment at ISOLDE (CERN) testing the new concept of post acceleration
of radioactive ion beams by using charge breeding of the ions in a high charge state ion source and the efficient acceleration
of the highly charged ions in a short LINAC using modern ion accelerator structures. In order to prepare the ions for the
experiments singly charged radioactive ions from the on-line mass separator ISOLDE will be cooled and bunched in a Penning
trap, charge bred in an electron beam ion source (EBIS) and finally accelerated in the LINAC. The LINAC consists of a radiofrequency
quadrupole (RFQ) accelerator, which accelerates the ions up to 0.3 MeV/u, an interdigital H-type (IH) structure with a final
energy between 1.1 and 1.2 MeV/u and three seven gap resonators, which allow the variation of the final energy. With an energy
of the radioactive beams between 0.8 MeV/u and 2.2 MeV/u a wide range of experiments in the field of nuclear spectroscopy,
astrophysics and solid state physics will be addressed by REX-ISOLDE.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
39.
M. Oinonen Y. Jading U. Köster J. Lettry H. Ravn J. Äystö P. Dendooven J. Huikari A. Jokinen P.O. Lipas A. Nieminen K. Peräjärvi T. Siiskonen P. Baumann A. Huck A. Knipper M. Ramdhane G. Walter F. Didierjean V.N. Fedoseyev V.I. Mishin M. Koizumi W. Liu E. Roeckl V. Sebastian 《Hyperfine Interactions》2000,127(1-4):431-436
Resonance ionization laser ion source (RILIS) technique has been used in the β-decay studies of 59Mn and 58Zn. The importance of the RILIS for production of these elements is discussed. The properties of the low-lying levels of the
studied nuclei are discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
40.
Krzysztof B. Be Justyna Grabska Christian W. Huck Sylwester Mazurek Mirosaw A. Czarnecki 《Molecules (Basel, Switzerland)》2021,26(22)
Mid-infrared (MIR) and near-infrared (NIR) spectra of crystalline menadione (vitamin K3) were measured and analyzed with aid of quantum chemical calculations. The calculations were carried out using the harmonic approach for the periodic model of crystal lattice and the anharmonic DVPT2 calculations applied for the single molecule model. The theoretical spectra accurately reconstructed the experimental ones permitting for reliable assignment of the MIR and NIR bands. For the first time, a detailed analysis of the NIR spectrum of a molecular system based on a naphthoquinone moiety was performed to elucidate the relationship between the chemical structure of menadione and the origin of the overtones and combination bands. In addition, the importance of these bands during interpretation of the MIR spectrum was demonstrated. The overtones and combination bands contribute to 46.4% of the total intensity of menadione in the range of 3600–2600 cm−1. Evidently, these bands play a key role in shaping of the C-H stretching region of MIR spectrum. We have shown also that the spectral regions without fundamentals may provide valuable structural information. For example, the theoretical calculations reliably reconstructed numerous overtones and combination bands in the 4000–3600 and 2800–1800 cm−1 ranges. These results, provide a comprehensive origin of the fundamentals, overtones and combination bands in the NIR and MIR spectra of menadione, and the relationship of these spectral features with the molecular structure. 相似文献