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921.
Summary A direct titrimetric method for the estimation of iron(III) has been developed, which involves the adjustment of concentration of iron(III) andPh, dilution, addition of 1 ml of 2% indicator solution and titration with EDTA (30° to 35° C). It is based on the fact that the iron(III) forms a blue coloured complex which is destroyed at the 11 molar ratio making the end-point of the titration. Quantity of iron(III) as small as 23.2 mg can be titrated accurately when present in a volume of 100 ml. Study of interferences revealed that quite a number of elements like Be2+, Mg2+, Ca2+, Sr2+, Ba2+, UO2
2+ and Mn2+ does not interfere, whereas much interference is caused by Cu2+, Zn2+, Pb2+, Fe2+, Co2+, Ni2+, ZrO2+, V02+, Al3+, Cr3+, Ti4+, Ce4+ and Th4+. The method proposed for iron(III) is selective and should be of considerable use in many cases.Part III: See Z. analyt. Chem. 167, 332 (1959). 相似文献
922.
We calculated the geometrical structures and electronic properties of neutral and anionic Fe2Cn clusters (n = 3,4) using a density-functional method that employs linear combinations of atomic orbitals as basis sets, standard nonlocal norm-conserving pseudopotentials, and the generalized gradient approximation to exchange and correlation. We show that the ground-state structures of Fe2C3 and Fe2C4 are essentially the same in the neutral and anionic states, namely, planar rings that feature nonadjacent Fe atoms. For the anionic clusters, these findings contrast with previously published results. 相似文献
923.
R. C. Orlando E. A. N. Fernandes M. Szikszay 《Journal of Radioanalytical and Nuclear Chemistry》1994,179(2):259-266
This study comprises Tertiary sediments (clays, silts, and fine clayey sands) from the unsaturated zone of the Experimental Station in the University of São Paulo, taken from a nine meters depth profile; ten samples were separated in bulk and <53 m fractions. Chemical composition was determined by INAA to ascertain the distribution of trace elements throughout the sediment deposition, and to establish the background parameters, useful for mobilization studies of such elements after industrial waste disposal. 相似文献
924.
D. L. Bowers E. A. Rhodes C. E. Dickerman 《Journal of Radioanalytical and Nuclear Chemistry》1998,230(1-2):161-165
The formation of160Er,159Dy and149Gd employing natural dysprosium as target and its irradiation with α-particles was the objective of this work. This is included
in a study performed by our group on excitation functions of induced reactions for charged particles on rare earths. A target
with metallic foils of Dy was irradiated in the Isochronous Cyclotron at Karlsruhe (Germany) with incident energy up to 88.5
MeV. Due to the contributions of the precursors in the isobaric chains, we were not able to measure the absolute cross sections.
Then, the determination of the cumulative cross sections were carried out. Thick target yields for the production of160Er,159Dy and149Gd are also presented. At present we do not know other publications about the functions studied in this work. 相似文献
925.
Monitoring the atmospheric stability by using radon concentration measurements: A study in a Central Italy site 总被引:1,自引:0,他引:1
D. Desideri C. Roselli L. Feduzi M. Assunta Meli 《Journal of Radioanalytical and Nuclear Chemistry》2006,270(3):523-530
Summary Meteorological and radon concentration data referring to a measurement campaign carried out in Urbino, Central Italy, are
reported and discussed. This study presents a method allowing monitoring of the vertical atmospheric stability using continuous
measurements of radon gas near ground. In particular radon evidences the presence of temperature inversion such as the formation
of the nocturnal stable layer and gives information on the vertical turbulence and the motion of air masses. This technique
is very useful in describing the temporal evolution of the pollutants in the atmosphere. 相似文献
926.
A method is presented for the determination of 2-10M nitric acid based on the fact that the presence of high nitric acid concentration causes an enhancement of the intensity of some bands in the fluorescence spectra of rare earth ions in solution. The 616-nm band of Eu(3+) shows the most dramatic intensity enhancement with increasing nitric acid concentration. The present method, based on the measurement of the ratio of Eu(3+) fluorescent band intensities is shown to be independent of Eu(3+) concentration and relatively free of interference. This robust method allows the presence of an interferent to be determined from the experimental data. 相似文献
927.
R. E. Van Der Stoel H. C. Van Der Plas G. Geurtsen 《Journal of heterocyclic chemistry》1980,17(7):1617-1620
1H- and 13C-nmr spectroscopy is presented showing that photolysis of 4-(p-trifluoromethylphenyl)-1,4-(3,4)-dihydropyrimidine yields 6-(p-trifluoromethylphenyl)-2,4-diazabicyclo[3.1.0]hex-2-(3)ene. 相似文献
928.
An apparatus is described that enabled us to carry out a quantitative kinetic investigation of rather quick physicochemical transformations of divided solids by means of an emission of radioactive gas, as in the emanation method. Especially the details of the reaction cells are given in which surface area measurements by the BET method are also performed, and of the low volume scintillation chamber. Its high efficiency does not depend on the nature of the gas. The diverse components of the device ensure a good quality of pure atmosphere or vacuum, rapid and precise temperature setting and control, and reproducible sweeping of the radioactive gas escaping from the sample. 相似文献
929.
Fluorocarbons containing higher halogens have the potency of breaking certain hydrogen bonds in solutions. The relative strength of this potency varies in the series F < Cl < Br < I and the presence of hydrogen atoms in the fluorocarbon increases it. There is a striking parallelism between the hydrogen bond breaking and the anaesthetic potency of these molecules. It is suggested that the breaking of hydrogen bonds is an important step in the mechanism of anaesthesia. 相似文献
930.
L. A. Gugliemelli C. L. Swanson W. M. Doane 《Journal of polymer science. Part A, Polymer chemistry》1973,11(10):2451-2462
Acrylonitrile (AN) was graft copolymerized onto gelatinized and granular wheat starch in aqueous media in the presence of ceric ammonium nitrate initiator at 91-364 anhydroglucose units (AGU) per cerium (IV) and at 1.08-4.33 AN to AGU ratios. Molecular weights and dispersities of polyacrylonitrile side chains were determined by gel-permeation chromatography. Conversion-time plots of AN polymerizations in both gelatinized and granular starch systems show characteristics common to heterogeneous polymerizations that could be explained on the basis of buried polymer radicals. The rates of polymerizations were directly related to the square root of the corrected cerium(IV) concentration and to the 1.3 power of the AN concentration. Graft copolymerization of AN onto starch, at least during initial stages, is not suitably explained by a kinetic scheme involving termination by polymer radical with cerium(IV) ion. 相似文献