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991.
The Crystal Structure of Lithiummetaperiodate, LiIO4 For the first time single crystals of LiIO4 were obtained. According to the results of an X-ray structure determination (monoclinic, P21/n; a = 525.5(3), b = 851.1(4), c = 796.9(5) pm, β = 104.21(3)°; Z = 4; 2 148 diffractometer data, R = 0.024) the coordination by oxygen is tetrahedral for iodine and strongly distorted trigonal bipyramidal for lithium. Two lithium-oxygen-polyhedra are connected via a common edge. LiIO4 crystallises isostructural to LiAlH4. The structure is discussed and compared to those of other metaperiodates and tetrahydridoaluminates. 相似文献
992.
Thomas Hartmann Helmut Ehrenberg Gerhard Miehe Thorsten Buhrmester Gernot Wltschek Jean Galy Hartmut Fuess 《Journal of solid state chemistry》2001,160(2):317
Trirheniumdecaoxide, Re3O10, was obtained by the reaction of ReO2 and ReO3 in an arc-melting furnace. X-ray powder diffraction revealed a tetragonal structure with space group I
m2 and lattice constants a=5.171(1) and c=13.371(6) Å. The crystal structure is built up by layers of corner-sharing [ReO5] square pyramids perpendicular to [001] with the apical oxygen pointing up and down alternatingly. These layers are interconnected by disordered [ReO6] octahedra. Early reports on Re2O5 are reviewed in the light of our results. 相似文献
993.
A new three-component, palladium-catalyzed domino reaction which gives access to meta-substituted arenes using aryl iodides and primary alkyl halides is reported. Various functional groups are tolerated on both the aryl iodide and alkyl halide. In addition, isotopic labeling studies provide insight into the mechanism of this Catellani-type reaction. [reaction: see text] 相似文献
994.
Cm(III) interaction with calcite was investigated by time-resolved laser fluorescence spectroscopy (TRLFS) in the trace concentration range. Two different Cm(III)/calcite sorption species were found. The first Cm(III) sorption species consists of a curium ion bonded onto the calcite surface. The second Cm(III) sorption species has lost its complete hydration sphere and is incorporated into the calcite bulk structure. The Cm(III)/calcite complexes are characterized by their emission spectra (peak maxima at 607.5 and 618.0 nm) and their fluorescence emission lifetimes (314+/-6 and 1302+/-75 micros). 相似文献
995.
Substitution reactions on 2′,3′,5′,6′-tetrachloro-4-dimethylamino-[1,4]bipyridinyl-1-ylium chloride with nitrogen nucleophiles such as n-propylamine, isopropylamine, glycine, morpholine, and piperidine were examined. Highly functionalized Cl2,Cl3,N4,Cl5,Cl6- and N2,Cl3,N4,Cl5,Cl6-substituted pyridines were obtained, in part possessing unsubstituted 4-amino groups due to dealkylation. Detailed NMR studies were performed in order to elucidate the regiochemistry of these dealkylations. 相似文献
996.
Gansäuer A Lauterbach T Narayan S 《Angewandte Chemie (International ed. in English)》2003,42(45):5556-5573
Over the last few decades the use of radicals in synthesis has witnessed an explosive growth through introduction of efficient chain and electron-transfer reactions. Strained heterocycles, in particular, have emerged as a highly versatile and readily available class of radical precursors. The generation of carbinyl radicals of heterocycles has resulted in many elegant applications of heteroatom-centered radicals, such as beta fragmentations, cyclizations, and intramolecular hydrogen atom abstractions. Direct electron transfer to strained heterocycles has been realized through the use of arene radical anions. The method combines the virtues of radical and organometallic chemistry to yield useful functionalized organolithium compounds. Epoxides have been opened with high regioselectivity by titanocene(III) reagents in either stoichiometric or catalytic quantities to yield beta-titanoxy radicals. This development has resulted in many new applications in natural product synthesis. 相似文献
997.
Peng S Edler M Ahlmann N Hoffmann T Franzke J 《Rapid communications in mass spectrometry : RCM》2005,19(19):2789-2793
An interface to allow on-line qualitative and quantitative full-plate detection and analysis of compounds separated by thin-layer chromatography (TLC) is presented. A continuous wave diode laser is employed as a desorption source. Atmospheric pressure chemical ionization mass spectrometry ionizes and subsequently identifies the desorbed sample molecules. Besides direct laser desorption on untreated TLC plates, graphite particles were used as a matrix to couple in the laser power and improve the efficiency of desorption. 相似文献
998.
The 2-(omega-alkenyl)-substituted 2-methyl-3(2H)-furanones 2a and 2b were prepared from biacetyl (3) in four reaction steps and in overall yields of 20% and 21%, respectively. They underwent a clean intramolecular [2 + 2] photocycloaddition upon irradiation at lambda = 350 nm. Whereas compound 2a reacted in the expected manner and yielded 7-oxabicyclo[3.2.1.0(3,6)]octane 7 (87% yield), the regioselectivity in the photocycloaddition of compound 2b was completely reversed. The reaction led to compound 8 (92% yield) with the unusual 9-oxabicyclo[4.2.1.0(3,8)]nonane skeleton, the structure of which was established by single-crystal X-ray crystallography. 相似文献
999.
Kaiser T Wittke S Just I Krebs R Bartel S Fliser D Mischak H Weissinger EM 《Electrophoresis》2004,25(13):2044-2055
We describe the application of capillary electrophoresis (CE) coupled on-line to an electrospray ionization-time of flight-mass spectrometer (ESI-TOF-MS) to the analysis of human urine and serum for the identification of biomarkers for clinical diagnostics. CE-MS led to display > 1000 polypeptides present in complex biological samples within 45-60 min in a single analysis run. To extract the information of the CE-MS spectra in a timely fashion, a software was designed to automatically deconvolute and normalize the spectra. Both urine and serum contain several hundred polypeptides in samples from healthy individuals. Hence, it is possible to establish typical "normal urine" or "normal serum" polypeptide patterns. Samples from patients with different diseases display polypeptide patterns that differ significantly from those obtained from healthy individuals. Examining series of patients with the same disease allowed the establishment of polypeptide patterns typical for specific diseases. This permits the search for marker peptides specific for diseases. The data indicate that a single polypeptide present in all patients with the same disease, but absent in all healthy control individuals does not exist. The combination of several polypeptides found in either urine or serum or both are forming a specific pattern, which is indicative not only for the particular disease, but also for the stage of disease. CE-MS detects many polypeptides in single samples and the application of the software to the search of identical polypeptides excreted in urine allows the unbiased diagnosis based on a pattern and does not rely on single disease markers. 相似文献
1000.