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981.
Covalently linked azamacrocycles have been known for several decades, but only a modest number of these ligands and their complexes had been described prior to 2000. Since that time, a number of new synthetic methods for their preparation have been discovered, yielding a growing collection of these interesting ligands. Additionally, the number of uses to which these ligands and their metal complexes have been applied has expanded. In this review, the important synthetic methods yielding linked azamacrocycles will be outlined, and their applications will be discussed. 相似文献
982.
Mesoporous silica particles of relatively uniform sub-1-micron size (0.6-0.9 μm) were successfully prepared by a modified synthesis strategy and applied in chiral separation in an ultra-high pressure liquid chromatography system. These particles were prepared via a ternary surfactant system (Pluronic P123, F127 and hexadecyltrimethyl-ammonium bromide) and subsequently derivatized with perphenylcarbamoylated-β-cyclodextrin moieties. The mesoporous silica particles, despite their submicron size, enabled low back-pressure operation on an ultra-high pressure liquid chromatography system at a maximum flow rate of 2 ml/min. In addition, the particles possessed high surface area (480 m(2)/g) and thus afforded high cyclodextrin derivative loading (32 μmol/g), demonstrating rapid enantioseparation and good resolution of 6 basic and neutral racemates. 相似文献
983.
Marcin Smiglak Dr. C. Corey Hines Timothy B. Wilson Shailendra Singh Dr. Adam S. Vincek Dr. Kostyantyn Kirichenko Dr. Alan R. Katritzky Prof. Robin D. Rogers Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(5):1572-1584
Compartmentalized molecular level design of new energetic materials based on energetic azolate anions allows for the examination of the effects of both cation and anion on the physiochemical properties of ionic liquids. Thirty one novel salts were synthesized by pairing diverse cations (tetraphenylphosphonium, ethyltriphenylphosphonium, N‐phenyl pyridinium, 1‐butyl‐3‐methylimidazolium, tetramethyl‐, tetraethyl‐, and tetrabutylammonium) with azolate anions (5‐nitrobenzimidazolate, 5‐nitrobenzotriazolate, 3,5‐dinitro‐1,2,4‐triazolate, 2,4‐dinitroimidazolate, 4‐nitro‐1,2,3‐triazolate, 4,5‐dinitroimidazolate, 4,5‐dicyanoimidazolate, 4‐nitroimidazolate, and tetrazolate). These salts have been characterized by DSC, TGA, and single crystal X‐ray crystallography. The azolates in general are surprisingly stable in the systems explored. Ionic liquids were obtained with all combinations of the 1‐butyl‐3‐methylimidazolium cation and the heterocyclic azolate anions studied, and with several combinations of tetraethyl‐ or tetrabutylammonium cations and the azolate anions. Favorable structure–property relationships were most often achieved when changing from 4‐ and 4,5‐disubstituted anions to 3,5‐ and 2,4‐disubstituted anions. The most promising anion for use in energetic ionic liquids of those studied here, was 3,5‐dinitro‐1,2,4‐triazolate, based on its contributions to the entire set of target properties. 相似文献
984.
Andrews PC Brown DH Fraser BH Gorham NT Junk PC Massi M St Pierre TG Skelton BW Woodward RC 《Dalton transactions (Cambridge, England : 2003)》2010,39(46):11227-11234
Three pentanuclear lanthanoid hydroxo clusters of composition [Ln(OH)(5)(abzm)(10)], where Ln = Eu, Tb, Ho and abzm = di(4-allyloxy)benzoylmethanide, have been prepared. The structures have been characterised by means of IR, Raman, elemental analyses and X-ray diffraction, showing a pyramidal square-based cluster core. The clusters (Tb and Ho) exhibit Curie-Weiss Law behaviour, displaying antiferromagnetic ordering at low temperatures. The emission properties of the Eu cluster demonstrate the abzm(-) ligand is an efficient antenna (λ(ex) = 420 nm) only for the sensitisation of Eu luminescence in the visible range, via energy transfer to the (5)D(0) state of the trivalent metal. The clusters have been reacted in the presence of methyl methacrylate and azobisisobutyronitrile to prepare reinforced polymers via radical polymerisation. The obtained materials exhibit swelling upon immersion into organic solvents up to ≈ 110% of their original size, in agreement with the presence of cluster-crosslinked polymeric chains. Also, no loss of transparency was observed in the preparation of the materials. The characteristic red emission of the Eu cluster in also retained in the polymeric material. 相似文献
985.
A new diffusion anisotropy index, ellipsoidal area ratio (EAR), was described recently and proved to be less noise-sensitive than fractional anisotropy (FA) by theory and simulation. Here we show that EAR has higher signal-to-noise ratios than FA in average diffusion tensor imaging data from 40 normal subjects. EAR was also more sensitive than FA in detecting white matter abnormalities in a patient with widespread diffuse axonal injury. Monte Carlo simulation showed that EAR's mean values are more biased by noise than FA when anisotropy is small, both for single fiber tracts and when fiber tracts cross. However, the improved signal-to-noise ratio of EAR relative to FA suggests that EAR may be a superior measure of anisotropy both in quantifying both deep white matter with relatively uniform fiber tracts and pericortical white matter structure with relatively low anisotropy and fiber crossings. 相似文献
986.
Rados?aw Kamiński Timothy Graber Jason B. Benedict Robert Henning Yu‐Sheng Chen Stephan Scheins Marc Messerschmidt Philip Coppens 《Journal of synchrotron radiation》2010,17(4):479-485
The accuracy that can be achieved in single‐pulse pump‐probe Laue experiments is discussed. It is shown that with careful tuning of the experimental conditions a reproducibility of the intensity ratios of equivalent intensities obtained in different measurements of 3–4% can be achieved. The single‐pulse experiments maximize the time resolution that can be achieved and, unlike stroboscopic techniques in which the pump‐probe cycle is rapidly repeated, minimize the temperature increase due to the laser exposure of the sample. 相似文献
987.
Determination of ion structures in structurally related compounds using precursor ion fingerprinting
Michelle T. Sheldon Robert Mistrik Timothy R. Croley 《Journal of the American Society for Mass Spectrometry》2009,20(3):370-376
Structurally-related alkaloids were analyzed by electrospray ionization/multiple stage mass spectrometry (ESI/MS
n
) at varying collision energies to demonstrate a conceptual algorithm, precursor ion fingerprinting (PIF). PIF is a new approach
for interpreting and library-searching ESI mass spectra predicated on the precursor ions of structurally-related compounds
and their matching product ion spectra. Multiple-stage mass spectra were compiled and constructed into “spectral trees” that
illustrated the compounds’ product ion spectra in their respective mass spectral stages. The precursor ions of these alkaloids
were characterized and their spectral trees incorporated into an MS
n
library. These data will be used to construct a universal, searchable, and transferable library of MS
n
spectra. In addition, PIF will generate a proposed structural arrangement utilizing previously characterized ion structures,
which will assist in the identification of unknown compounds. 相似文献
988.
Timothy Biswick William Jones Aleksandra Pacuła Ewa Serwicka Jerzy Podobinski 《Solid State Sciences》2009,11(2):330-335
Zinc hydroxy acetate, Zn5(OH)8(CH3CO2)2·4H2O, has been prepared by the precipitation method. It has been demonstrated by FTIR analysis that, contrary to previous reports, the interaction of the acetate anion with the matrix cation is ionic. TG analysis, mass spectral analysis of the evolved gases, and in situ variable temperature PXRD and FTIR analysis have shown that decomposition of the material to ZnO involves the formation of Zn5(OH)8(CH3CO2), Zn3(OH)4(CH3CO2)2 and anhydrous zinc acetate (Zn(CH3CO2)2) as some of the acetate-containing intermediate solid products. The acetate anion is finally lost, at temperatures below 400 °C, as acetic anhydride, (CH3CO)2O. 相似文献
989.
Amanda K. Petrus Timothy J. Fairchild Prof. Robert P. Doyle Prof. 《Angewandte Chemie (International ed. in English)》2009,48(6):1022-1028
Oral routes of administration for therapeutic peptides and proteins face two major barriers: proteolytic degradation in the stomach and an inadequate absorption mechanism for polypeptides within the intestinal lumen. As a result, peptide‐based therapeutics are administered by injection, a painful process associated with lower patient compliance. The development of a means of overcoming these two major obstacles and enabling the successful delivery of peptide therapeutics by the oral route of administration has therefore been the target of extensive scientific endeavor. This Minireview focuses on oral peptide/protein delivery by the dietary uptake pathway for vitamin B12. Recent progress in this field includes the delivery of erythropoietin, granulocyte‐colony‐stimulating factor, luteinizing‐hormone‐releasing hormone, and insulin. 相似文献
990.
Aaron R. Van Dyke Timothy F. Jamison Prof. 《Angewandte Chemie (International ed. in English)》2009,48(24):4430-4432
Extension ladder : The successful application of epoxide‐opening strategies towards the synthesis of ladder‐type polyethers is contingent upon further elaboration of the product. By employing two different functionalized templates, a fragment of gymnocin A that bears four sites for subsequent fragment coupling has been prepared (see scheme; Bn=benzyl).