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31.
Ortiz ME 《Physical review D: Particles and fields》1992,45(8):R2586-R2589
32.
33.
Rosa Ortiz Joaquín Borrás Lourdes Perelló Horacio Jimenez 《Monatshefte für Chemie / Chemical Monthly》1986,117(4):443-451
The formation constants of the binary complexes Cu(CM)2+ and Cu(CM)
2
2+
as well as those of the ternary complexes Cu(CM)L
+ and Cu(CM)2
L
+ (CM=Cimetidine=N-Cyano-N-methyl-N[(5-methyl-1H-imidazol-4-yl)methyltioethyl]-guanidine; HL=Phenobarbital=5-ethyl-5-phenyl-barbituric acid) have been determined in 0.1 and 1.0 mol dm–3 NaClO4 methanol solutions at 25±0.2°C. The values of logX, log stat.., and logK confirm the stability of the ternary complexes.
Ternäre Komplexe von Cimetidin und Phenobarbital mit Cu(II) in methanolischer Lösung
Zusammenfassung Die Stabilitätskonstanten der binären Komplexe Cu(CM)2+ und Cu(CM) 2 2+ sowie die der ternären Komplexe Cu(CM)L + und Cu(CM)2 L + (CM=Cimetidin=N-Cyan-N-methyl-N-[(5-methyl-1H-imidazol-4-yl)methylthioethyl]-guanidin; HL=Phenobarbitalum=5-Ethyl-5-phenyl-barbitursäure) wurden in 0.1 und 1.0M Lösungen von NaClO4 in Methanol bei 25±0.2°C bestimmt. Die Werte von logX, log stat. und logK bestätigen die Stabilität der ternären Komplexe.相似文献
34.
Mogolloń L. Rodríguez R. Larrota W. Ortiz C. Torres R. 《Applied biochemistry and biotechnology》1998,(1):765-777
Asphaltenes from a crude oil rich in heavy metals (Castilla crude oil) were fractionated and partially characterized. Biocatalytic
modifications of these fractionated asphaltenes by three different hemoproteins: chloro-peroxidase (CPO), cytochrome C peroxidase
(Cit-C), and lignin peroxi-dase (LPO) were evaluated in both aqueous buffer and organic solvents. The reactions were carried
out in aqueous buffers, ternary systems of toluene: isopropanol: water, and aqueous-miscible organic solvent solutions with
petroporphyrins as substrate. The petroporphyrins were more soluble in the ternary systems and aqueous miscible-organic solvent
systems than in the aqueous buffer systems. However, only the CPO-mediated reactions were effective in eliminating the Soret
peak in both aqueous and organic solvent systems. The effects of CPO-mediated reactions on the release of the metals complexed
with the porphyrins and asphaltenes were also determined. Chloroperoxidase was able to alter components in the heavy fractions
of petroleum and remove 53 and 27% of total heavy metals (Ni and V, respectively) from petroporphyrin-rich fractions and asphaltenes 相似文献
35.
A rapid and simple fractionation procedure using solid-phase extraction (SPE) cartridges was developed for an accurate determination of aliphatic and polycyclic aromatic hydrocarbons in petroleum residues and further application in chemical fingerprinting of oil spills by gas chromatography-mass spectrometry (GC-MS). Among the adsorbents evaluated, SiO2/C3-CN exhibited the best selectivity, providing, by elution with n-hexane (4 ml) and n-hexane-CH2Cl2 (1:1) (5 ml), two well-resolved aliphatic and aromatic hydrocarbon fractions, with recoveries of 97 +/- 7.2 and 99.7 +/- 13.9%, respectively. The SPE fractionation procedure was compared with the conventional silica-alumina adsorption chromatography showing similar results but practical advantages in terms of reproducibility, analysis time, solvent reduction and cost. Moreover, is particularly suitable for routine analysis with a high sample throughput. The developed methodology was tested in the characterization of fuel-oil samples collected along the Spanish north-west coast, after the Prestige oil spill accident. 相似文献
36.
A sequential kinetic discrimination of potential kinetic models for non-isothermal linear programmed temperature data on the depolymerization of trioxane in a homogeneous liquid phase has been discussed.The influence of the initial concentration on the kinetic curves has been used as an experimental confirmation of the first-order influence of the concentration on the model.Kinetic analysis at constant temperature and conversion permits separation of the effects of concentration and temperature on the kinetic analysis at different levels of the variables.It is provided via non-isothermal kinetic data on the depolymerization of trioxane that nonisothermal experiment's allow a systematic approach to the kinetic behaviour in a wide range of the variables temperature and concentration, leading to maximum knowledge of the reaction model through minimum experimental effort.
Zusammenfassung Eine sequentielle kinetische Unterscheidung potentieller kinetischer Modelle für die nicht-isotherme, linear temperaturprogrammierte Depolymerisation von Trioxan in homogener flüssiger Phase wird diskutiert. Der Einfluß der Ausgangskonzentration auf die kinetischen Kurven wurde als experimentelle Bestätigung dafür angesehen, daß die Konzentration auf das Modell nach erster Ordnung einwirkt. Die kinetische Analyse bei konstanter Temperatur und Konversion ermöglicht eine Trennung des Einflusses der Konzentration und Temperatur auf die kinetische Analyse bei unterschiedlichen Werten dieser Variablen. In der vorliegenden Arbeit wurde anhand von nichtisothermen kinetischen Daten für die Depolymerisation von Trioxan gezeigt, daß nicht-isotherme Experimente eine systematische Näherung an das kinetische Verhalten in einem weiten Bereich der Variablen Temperatur und Konzentration erlauben und zu einen Maximum an Erkenntnissen über das Reaktionsmodell bei einem Minimum an experimentellen Aufwand führen.
- - . . . , , , .相似文献
37.
de Ropp JS Sham S Asokan A Newmyer S Ortiz de Montellano PR La Mar GN 《Journal of the American Chemical Society》2002,124(37):11029-11037
The functional higher oxidation states of heme peroxidases have been proposed to be stabilized by the significant imidazolate character of the proximal His. This is induced by a "push-pull" combination effect produced by the proximal Asp that abstracts ("pulls") the axial His ring N(delta)H, along with the distal protonated His that contributes ("pushes") a strong hydrogen bond to the distal ligand. The molecular and electronic structure of the distal His mutant of cyanide-inhibited horseradish peroxidase, H42A-HRPCN, has been investigated by NMR. This complex is a valid model for the active site hydrogen-bonding network of HRP compound II. The (1)H and (15)N NMR spectral parameters characterize the relative roles of the distal His42 and proximal Asp247 in imparting imidazolate character to the axial His. 1D/2D spectra reveal a heme pocket molecular structure that is highly conserved in the mutant, except for residues in the immediate proximity of the mutation. This conserved structure, together with the observed dipolar shifts of numerous active site residue protons, allowed a quantitative determination of the orientation and anisotropies of the paramagnetic susceptibility tensor, both of which are only minimally perturbed relative to wild-type HRPCN. The quantitated dipolar shifts allowed the factoring of the hyperfine shifts to reveal that the significant changes in hyperfine shifts for the axial His and ligated (15)N-cyanide result primarily from changes in contact shifts that reflect an approximately one-third reduction in the axial His imidazolate character upon abolishing the distal hydrogen-bond to the ligated cyanide. Significant changes in side chain orientation were found for the distal Arg38, whose terminus reorients to partially fill the void left by the substituted His42 side chain. It is concluded that 1D/2D NMR can quantitate both molecular and electronic structural changes in cyanide-inhibited heme peroxidase and that, while both residues contribute, the proximal Asp247 is more important than the distal His42 in imparting imidazole character to the axial His 170. 相似文献
38.
Villagomez-Guzman Ana K. Rodriguez-Garcia Gabriela del Rio Rosa E. Oliveros Ortiz Antonio J. Cerda-Garcia-Rojas Carlos M. Joseph-Nathan Pedro Gomez-Hurtado Mario A. 《Chemistry of Natural Compounds》2021,57(2):319-322
Chemistry of Natural Compounds - A known kaurenoic acid (1), together with a new kaurane derivative named 3α-isobutyryloxykaurenoic acid (2), was isolated from the roots of Lasianthaea aurea,... 相似文献
39.
40.