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51.
Spectrofluorometric determination of certain quinolone antibacterials using metal chelation 总被引:1,自引:0,他引:1
Simple, rapid, reliable, and sensitive spectrofluorometric methods were developed for the determination of eight quinolone antibacterials namely ciprofloxacin, norfloxacin, lomefloxacin, difloxacin, amifloxacin, pefloxacin, ofloxacin, and nalidixic acid. The methods depend on the chelation of each of the studied drugs with zirconium, molybdenum, vanadium or tungsten to produce fluorescent chelates. Different factors affecting the relative fluorescence intensity of the resulting chelates were studied and optimised. At the optimum reaction conditions, the drug-metal chelates showed excitation maxima ranging from 274 to 295 nm and emission maxima ranging from 409 to 495 nm. The chelates were found to be stable at room temperature for 2 days and show good stability upon increasing temperature to 50 °C for about 1 h. Rectilinear calibration graphs were obtained in the range of 10-60 ng ml−1 for each of the investigated drugs and the limits of detection and quantitation ranged from 1.214 to 2.046 and from 4.047 to 6.819 ng ml−1, respectively. The molar ratios of the formed chelates were determined by Job's method and their association constants were also calculated. The developed methods were applied successfully for the determination of the studied drugs in their pharmaceutical dosage forms with a good precision and accuracy compared to official and reported methods as revealed by t- and F-tests. They were also applied for the determination of studied drugs in spiked urine and plasma samples. 相似文献
52.
53.
Colloidal palladium nanocatalysts prepared by in situ reductions of palladium chloride were immobilized and protected by either of two water-soluble polymers. The particle sizes and size distributions of the palladium colloids were determined by transmission electron microscopy. Their selectivities as catalysts were determined by comparing the extents of hydrogenation of carefully chosen pairs of small-molecule olefins. There was found to be high hydrogenation selectivity with regard to cyclic vs. noncyclic olefins. Selectivity was relatively low, however, among olefins that differed only in size (such as hexene vs. octene), or olefins differing only with regard to the positions of the double bonds (such as 1-octene vs. 3-octene). Selectivity could be improved by careful choice of the immobilizing polymer, and by its use at relatively high concentrations. 相似文献
54.
Prof. Dr. Werner Uhl 《Angewandte Chemie (International ed. in English)》1993,32(10):1386-1397
In the attempt to synthesize compounds with aluminum in a low oxidation state and an Al Al bond, by the reduction of alkylaluminum halides with alkali metals, analogous to a Wurtz coupling, in general the deposition of elemental aluminum and the formation of the corresponding trialkylaluminum compounds is observed. Thus, tetrasubstituted dialuminum compounds R2Al AlR2, apart from a few poorly characterized examples, were for a long time considered part of an unverified class of substances. Only with the sterically very highly shielded tetrakis[bis(trimethylsilyl)methyl]dialuminum did we achieve the synthesis of the first completely characterized organoelement compound with unlimited stability, which shows aluminum in the oxidation state + II and has an Al Al bond. In the meantime, corresponding compounds for the elements gallium and indium have been obtained. With the simple access to tetrasubstituted dimetal compounds, a fascinating new research area has opened for preparative chemistry, in which the particular interest will naturally lie in the reactive properties of the metal-metal bond. 相似文献
55.
56.
Synthesis and Structure of Li3RhH6 — a Ternary Hydride with Isolated [RhH6]3? Octahedra The ternary rhodium hydride Li3RhH6 was synthesized by the reaction of lithium hydride with rhodium under a hydrogen pressure of 80 bar. X-ray investigations on powdered samples and an elastic neutron diffraction experiment on the deuterated compound led to the complete structure determination (space group: Pnma, Z = 4). The atomic arrangement is isotypic to the Na3RhH6 structure type. The crystal structure contains isolated [RhH6]3? octahedra, which are separated by the lithium ions. 相似文献
57.
Methods for metal preconcentration are often described in the literature. However, purposes are often different, depending
on whether the methods are applied in environmental, clinical or technological fields. The respective method needs to be efficient,
give high sensitivity, and ideally also is selective which is useful when used in combination with atomic spectroscopy. This
review presents the actual tendencies in metal preconcentration using techniques such as Flame Atomic Absorption Spectrometry
(FAAS), Electrothermal Atomic Absorption Spectrometry (ETAAS), Hydride Generation Atomic Absorption Spectrometry (HGAAS),
Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS).
Procedures based on related to electrochemical, coprecipitation/precipitation, liquid–liquid and solid–liquid extraction and
atom trapping mechanisms are presented.
Correspondence: Department of Analytical Chemistry, Universidade Estadual de Campinas – UNICAMP, P.O. Box 6154, 13083-970
Campinas, Brazil. e-mail: zezzi@iqm.unicamp.br
Received December 20, 2001; accepted October 11, 2002 相似文献
58.
Lichens are bioaccumulators of divalent metal ions and the interaction between the lichens and five heavy metals was studied. In order to have a better understanding of the metal-uptake process by the lichens, data from atomic absorption spectroscopy were used to calculate the apparent coordination constants of the lichen–metal ion interactions by means of the Langmuir elaboration and microcalorimetric measurements to obtain enthalpimetric information. The results showed a correlation between the Langmuir constants and enthalpimetric measurements. 相似文献
59.
The kinetics of oxidation of ascorbic acid in the presence of cobalt octa-4,5-carboxyphthalocyanine sodium salt (Teraphthal) was studied. A kinetic equation was obtained and a scheme of the process was proposed. According to the scheme, the first stage is the formation of a complex of the catalyst with dioxygen, and the limiting stage is the reaction of dioxygen with the ascorbate monoanion. The influence of the pH of the medium and the presence of a transport protein (albumin) on the state and catalytic activity of Teraphthal was studied. The involvement of hydrogen peroxide and oxygen-centered radicals in the catalytic oxidation of ascorbic acid was proved. 相似文献
60.
Rolf Niedermayer 《Angewandte Chemie (International ed. in English)》1975,14(4):212-218
Synthesis of organometallic materials can be accomplished in many cases by cocondensation of metal atoms and organic molecules at low temperatures. The reaction kinetics is determined by the competition between metal cluster growth and formation of the organometallic compound. Interesting compounds may contain one or more metal atoms; the latter type could be obtained by reaction between a cluster containing the desired number of metal atoms and an organic molecule. A precise knowledge of the events occurring on condensation of metal atoms and cluster formation can therefore be of value in the control of chemical synthesis. These phenomena have been investigated in connection with the study of the growth of thin metallic films, both experimentally and theoretically. Direct observation of the formation of very small clusters is difficult. The good agreement between experimental results and recent calculations for the development of large clusters, however, allows reliable theoretical conclusions for the first stages of adsorption and cluster formation. The present contribution describes experimental work on film growth and relevant theoretical concepts, and an attempt is made to develop applications to organometallic synthesis. 相似文献