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21.
Solid solutions of GeO2 in Fe2O3 were prepared by mechanically mixing the solids and firing at 1000°C in air, and from a gel obtained by the addition of an alcohol solution of germanium ethoxide to iron dissolved in HNO3. The dried gel was then heated at 1000°C. The solubility limit is 5 mole% GeO2, Fe1.95Ge0.05O3. Similar procedures were used to prepare solid solutions with Si and the solubility limit is greater than 4 mole% SiO2. Firing of mixtures or gels of Fe2O3 containing Mg produces a spinel phase even at the lowest detectable concentrations. The resistivity of pressed pellets of Fe2?xGexO3 varies from about 106 ohm-cm for x = 0 to about 10?1 ohm-cm for x = 0.05. The photoassisted electrolysis of water at Ge-doped Fe2O3 electrodes is demonstrated. The photoelectrochemical cell showed a 0.29-V open-circuit voltage, 1.2-mA/cm2 short-circuit current, 0.31 fill factor, and 0.06% power efficiency. 相似文献
22.
23.
M. Chatry M. Henry M. In C. Sanchez J. Livage 《Journal of Sol-Gel Science and Technology》1994,1(3):233-240
The hydrolysis and condensation of zirconium n-propoxide in n-propanol have been chemically controlled via the complexation of the zirconium precursor with acetylacetone. The size of the zirconium oxide-based particles is mainly controlled by the complexation ratio x=[acac]/[Zr]. the mean size increases from nanometric to submicronic range when x decreases from 1 to 0.1. Amorphous colloidal particles are obtained at room temperature. They result from a competitive growth/termination mechanism of zirconium-oxo species in the presence of acac surface capping agents. However non-aggregated nanocrystalline particles of tetragonal zirconia, about 2 nm in diameter are formed upon aging at 60°C when hydrolysis is performed in the presence of paratoluene sulfonic acid (PTSA). 相似文献
24.
A multiresidue, automated and rapid method for the determination of pesticide residues in olive oil is presented. The method employs the through oven transfer adsorption-desorption interface for the on-line coupling of reversed-phase liquid chromatography and gas chromatography. In this fully automated system, olive oil is directly injected with no sample pre-treatment step other than filtration. Methanol-water is used as eluent in the liquid chromatography pre-separation step. The selected liquid chromatography fraction containing the pesticides is automatically transferred to the gas chromatography. The liquid chromatography column flow during elution is different from the flow during the transfer. Using a flame ionisation detector, pesticide detection limits varied from 0.1 to 0.3 mg/l. 相似文献
25.
Starting with 1,1-dimethoxy-2-propanone ( 1 ), 6-formyl-1,2-dihydro-2-oxo-3-pyridinecarboxylic acid ( 5a ) has been prepared in large quantities by a highly efficient, 4-step synthesis. This compound, along with its one carbon homologue, 6-acetyl-1,2-dihydro-2-oxo-3-pyridinecarboxylic acid ( 5b ) has been reacted with several carbonyl derivative forming reagents to provide a series of side chains for β-lactams. Among these carbonyl derivatives are styrylamides which were prepared from Wittig and Horner-Emmons reagents. The preparation of the phosphonium salts and phosphonate esters is also described. 相似文献
26.
Preparative reversed-phase high-performance liquid chromatography has found wide use in the production of peptides for pharmaceutical formulations. Purity of the substance and overall economy of the chromatographic system are the most important criterias. In this sense optimized, silica particles and production process with capability to separately control parameters important to chromatography, are essential to high-performance chromatography. Kromasil C18 packing material was tested and evaluated in respect of its selectivity, flow and pressure properties, resolution, load capacity, recovery, adsorption effects, mechanical strength and chemical degradation. 相似文献
27.
J. Hernandez Mendez A. Sanchez Perez F. Lucena Conde 《Journal of Electroanalytical Chemistry》1975,66(1):53-65
The anodic oxidation of a dropping copper amalgam electrode in presence of dilute solutions of glycine in 0.50 M NaClO4 has been studied. An anodic wave at ?0.28V (SCE) is observed, yielded by diffusion of glycinate anion in the solution towards the electrode surface. The wave-heights increase with the glycinate concentration (function of glycine concentration and pH value) until the anodic oxidation is controlled by the metal diffusion into mercury. The effect of pH is interpreted by attributing it to the depolarizer effects at glycinate anion even though the zwitterion is present in much larger concentrations. The applicability of anodic oxidation of a dropping copper amalgam electrode in the determination of glycine in the range of concentrations 10?4–10?2M with a rigorous control of pH (8.0<pH<10.5) is shown. The standard deviation of the proposed method is 4.1% and the minimum concentration determinable is in the 1×10?4M range. 相似文献
28.
1-Ethyl-6-fluoro-1,4-dihydro-7-methyl-4-oxo-1,8-naphthyridine-3-carboxylic acid ( 8 ) has been prepared in large quantities by a highly efficient process. It has in turn been degraded to give 7-chloro-1-ethyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid ( 11 ). This intermediate has been reacted with piperazine to give the known antibacterial agent, enoxacin ( 12 ). 相似文献
29.
使用硫杂冠醚、穴醚[2.2.2]作气相色谱固定相制备毛细管柱,考察两种固定相的使用比例、极性、热稳定性,并对甲苯-苯、乙苯-甲苯、甲基苯酚(o/p)、二氯苯(o/p,m)、硝基氯化苯(m,o)、苯-环己烷、庚醇-辛醇、苯胺-N,N二甲基苯胺等混合样品进行色谱分离.实验结果表明:两种固定相在OV-1701中的比例均为15%时有较好的分离效果,都属于中等极性的固定相.硫杂冠醚、穴醚[2.2.2]的平均极性分别为815、832,其中硫杂冠醚固定相的热稳定性较好,有较高的使用温度(185℃),而穴醚[2.2.2]的最高使用温度为120℃,因此穴醚[2.2.2]的使用温度受到一定的限制.从它们较好的分离性能看,固定相硫杂冠醚、穴醚[2.2.2]均具有较好的应用前景. 相似文献
30.