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61.
Takeshi Matsumoto Akitami Ichihara Mitsutoshi Yanagiya Tamio Yuzawa Akiyoshi Sannai Hideaki Oikawa Sadao Sakamura Conrad Hans Eugster 《Helvetica chimica acta》1985,68(8):2324-2331
By a simple process, 3-methoxyjuglone (= 8-hydroxy-2-methoxy-1,4-naphthoquinone; 9 ) has been synthesized from 1,2,4-trimethoxybenzene ( 5 ) and converted, after prenylation, to α-caryopterone ( 1 ; Scheme 1), a pyranojuglone pigment from Caryopteris clandonensis. On the other hand, juglone (= 5-hydroxy-1,4-naphthoquinone; 12 ) was regioselectively prenylated at C(2) via its 1-methoxy-cyclohexa-1,3-diene adduct 15 (Scheme 2). The 2-prenyljuglone ( 4 ) thus formed led to 1 after oxidation and other reactions. 相似文献
62.
Moment equations were developed on the basis of the Einstein equation for diffusion and the random walk model to analytically determine the rate constant for the interfacial solute permeation from a bulk solvent into molecular aggregates (kin) and the inverse rate constant from the molecular aggregates to the bulk solvent (kout). The moment equations were in good agreement with those derived in a different manner. To demonstrate their effectiveness in one concrete example, the moment equations were used to analytically determine the values of kin and kout of three electrically neutral solutes, i.e. resorcinol, phenol, and nitrobenzene, from the first absolute (μ1A) and second central (μ2C) moments of their elution peaks, as measured by electrokinetic chromatography (EKC), in which the sodium dodecyl sulfate (SDS) micelles were used as a pseudostationary phase. The values of kin and kout should be determined with no chemical modifications and no physical action with the molecular aggregates because they are dynamic systems formed through weak interactions between the components. The moment analysis of the elution peak profiles measured by EKC is effective to unambiguously determine kin, kout, and the partition equilibrium constant (kin/kout) under appropriate experimental conditions. 相似文献
63.
A new model of surface diffusion in reversed-phase liquid chromatography (RPLC) was derived by assuming a correlation between surface and molecular diffusion. Analysis of surface diffusion data under different conditions of sample compounds, mobile and stationary phases, and temperature in RPLC systems validates this assumption and shows that surface diffusion should be regarded as a molecular diffusion restricted by the adsorptive interactions between the adsorbate molecule and the stationary phase surface. A surface-restricted molecular diffusion model was proposed as a first approximation for the mechanism of surface diffusion. The model is formulated according to the absolute rate theory. The activation energy of surface diffusion (Es) was quantitatively interpreted assuming that Es consists of the contributions of two processes, a hole-making and a jumping one. The former contribution is nearly equal to the activation energy of molecular diffusion and is correlated with the evaporative energy of the mobile phase solvent. The latter contribution is a fraction of the isosteric heat of adsorption. An appropriate explanation based on this new model of surface diffusion is provided for two contradictory results related to the relationship between retention equilibrium and surface diffusion in RPLC and to the surface diffusion coefficient for weakly retained sample compounds. 相似文献
64.
I. Katakuse H. Ito T. Ichihara 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):101-104
The dissociation patterns of doubly charged noble metal clusters (M) n ++ to two singly charged clusters, (M) m Emphasis>1/+ and (M) m Emphasis>2/+ have been investigated using a double focusing mass spectrometer. They are compared with the dissociation patterns from singly charged clusters. The dissociation probabilities to (M) 3 + and (M) 9 + were large and the odd-even alternations were observed in both patterns. 相似文献
65.
Formation and structure of titanium alkyl phosphates 总被引:1,自引:0,他引:1
Titanium alkyl phosphates (TiAP) synthesized by the reactions of Ti(SO(4))(2) with monohexyl, monooctyl, and monodecyl phosphates in aqueous media were characterized by various means. The XRD patterns of TiAP showed a strong diffraction peak and two weak ones below 2theta=15 degrees. The TiAP particle prepared using octyl phosphate gave rise to the lattice patterns having uniform alternating spacings of ca. 0.7 and ca. 2.0 nm. When treated at 900 degrees C, TiAP crystallized as TiP(2)O(7). The chemical formula could be shown as (ROPO(3))(2)Ti.0.44H(2)O. These facts suggest that the TiAP is composed of a multilayer alternating bimolecular layer of alkyl phosphates and hydrated titanium phosphate phase. Alkyl groups in the layers were removed by outgassing above 300 degrees C to give the materials having mesopores with a diameter of ca. 2 nm. 相似文献
66.
67.
Hexagonally ordered mesoporous Li2O-TiO2-P2O5 oxides with high lithium content have been synthesized using surfactant-templated self-assembly; this ternary oxide has been specifically designed to yield a variety of mesoporous frameworks including a nanocomposite, amorphous multicomponent oxide, and almost fully nanocrystalline anatase. 相似文献
68.
Tanoue O Ichihara H Goto K Matsumoto Y Ueoka R 《Chemical & pharmaceutical bulletin》2003,51(2):224-226
The enantioselective hydrolysis of the amino acid esters, p-nitrophenyl-N-dodecanoyl-D(L)-phenylalaninates (C(12)-D(L)-Phe-PNP) catalyzed by active tripeptide, N-(benzyloxycarbonyl)-L-phenylalanyl-L-histidyl-L-leucine (Z-PheHisLeu) in the presence of coaggregates (hybrid membranes) composed of native phospholipid, L-alpha-dimyristoylphosphatidylcholine (DMPC) and nonionic surfactant, polyoxyethylene (8) lauryl ether (C(12)(EO)(8)) was easily controlled by regulating the reaction temperature and changing the composition of coaggregates. Furthermore, excellent correlations were observed between the enantioselectivity in the hydrolysis of C(12)-D(L)-Phe-PNP catalyzed by Z-PheHisLeu in the presence of coaggregates and physical properties of hybrid membranes. It is assumed that catalytic activities of tripeptide catalyst in hybrid membranes should be regulated by changing the microenvironments of reaction fields. 相似文献
69.
A sodium borohydride reduction, with subsequent atomization in a small argon—hydrogen—entrained air flame has been developed for the determination of arsenic and antimony by non-dispersive atomic fluorescence spectrometry. The proposed method increases the signal level and decreases the noise level in the system. The detection limits for arsenic and antimony are 0.05 ng and 0.1 ng, respectively. The analytical working curves are linear over about four decades of concentration from the detection limits. The consumption rates of hydrogen and argon are comparatively low, while the speed of hydride evolution is improved; a peak measurement requires less than 40 s. The technique has been applied to the determination of arsenic in steel samples. 相似文献
70.
Akiyoshi Osaka Kanji Tsuru H. Iida Chikara Ohtsuki Satoshi Hayakawa Yoshinari Miura 《Journal of Sol-Gel Science and Technology》1997,8(1-3):655-661
Apatite derived by sol-gel routes through an amorphous state or derived biomimetically is likely to provide chemically and
biologically active surfaces. Thus apatite or apatite-composite particles were prepared by spray-pyrolysis of several solutions
as they were applicable to medical treatment. Calcium lactate and ammonium dihydrogen phosphate aqueous solutions stabilized
with ethylenediaminetetraacetic acid were sprayed ultrasonically and pyrolysed at 600°C to yield amorphous particles of apatite
while apatite-ferric oxide composite powders were prepared from the solutions of calcium lactate and ferric nitrate. Solutions
of calcium nitrate and titanium ethoxide in 0.5 N HNO3 were also spray-pyrolysed at 600°C to prepare calcium titanate and titanium oxide particles trapped on a Ti substrate. Apatite
could biomimetically be developed on the calcium titanate particles when they were soaked in an acellular simulated body fluid. 相似文献