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91.
Santos E Schühle DT Jones H Schmickler W 《Langmuir : the ACS journal of surfaces and colloids》2005,21(14):6406-6421
The nonlinear optical properties of self-assembled monolayers obtained from bonding two different alpha-functionalized terthiophenes (alpha-T3) to (111) silver electrode surfaces have been investigated using second harmonic generation (SHG). The two (alpha-T3) compounds used were functionalized with alkane chains of different lengths (C8 and C4), and each was terminated with a thiol anchoring group. A nitrile group was attached to the terminal thiophene ring of the (alpha-T3) compound with the C4 chain. The orientation of the polarization of the incident beam was changed systematically and gradually between "p" and "s" orientation and the SH signal (isotropic and anisotropic contributions) analyzed in both directions ("P" and "S"). The symmetry of the system was reduced by the presence of the adlayers from C3v to C3. The dependence on the applied potential and the incident wavelength has also been studied. The relative magnitudes and phases of the various second-order tensor elements have been estimated and compared with the values for a bare surface. A resonance process in the (alpha-T3) pi moiety has been investigated, and from this, the effective "band-gap" energies of the organic semiconductor SAMs (i.e., the energy difference between the pi-pi bands) have been estimated. 相似文献
92.
The synthesis and properties of di-2-pyridyl ketone 2-furoylhydrazone as an analytical reagent are described. A rapid procedure for the fluorimetric determination of aluminium at the 10-100 ng ml level, at pH 6.1-6.5 (lambda(exc) 395 nm, lambda(em) 465 nm) has been established. Interferences have been evaluated, and the procedure has been applied satisfactorily to determination of aluminium in sea-water. 相似文献
93.
Zuev V. V. de Vekki D. A. Kuchaev A. E. Vorob’ev M. V. Skvortsov N. K. 《Russian Journal of General Chemistry》2004,74(11):1679-1685
Hydrosilylation of p-substituted acetophenones XC6H4COCH3 (X = H, Me, MeO, HO, F, Cl, NO2) with 1,1,3,3-tetramethyldisiloxane in the presence of rhodium and platinum complexes was studied. The Pt(II) complexes are less active but more selective catalysts of hydrosilylation of acetophenones. Six new 1-(1-arylethoxy)-1,1,3,3-tetramethyldisiloxanes were prepared.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1804–1811.Original Russian Text Copyright © 2004 by Zuev, de Vekki, Kuchaev, Vorobev, Skvortsov.This revised version was published online in April 2005 with a corrected cover date. 相似文献
94.
Y. BallesterosM.J. Gonzalez de la Huebra M.C. QuintanaP. Hernandez L. Hernandez 《Microchemical Journal》2003,74(2):193-202
The electrochemical behaviour of kinetin (6-furfurylaminopurine) on a carbon paste modified with OV-17 silicone electrode, is studied. The determination of kinetin is possible working in square wave voltammetric techniques, reaching limits of determination of 38.7 ng ml−1. The proposed method was successfully applied to determine the cytokinin in extracts of apples (previously spiked with kinetin) and the obtained results were in accordance with the results obtained with HPLC-UV. 相似文献
95.
Multicomponent adsorption data of a fermentation broth containing adipoyl-7-amino-3-deacetoxycephalosporanic acid (adipoyl-7-ADCA), a cephalosporin precursor for 7-ADCA, and two key impurities, alpha-hydroxyadipoyl-7-ADCA and alpha-aminoadipoyl-7-ADCA were obtained from batch equilibrium and frontal chromatography tests. Amberlite XAD-1600 was chosen as the resin. A rate model was applied to simulate the chromatograms. An alkaline buffer, which by itself has no affinity for the resin, was used as the eluent. The widely used reversed-phase modulator model is inaccurate in explaining the stepwise elution data. A new model, the induced competition model, has been developed to account for apparent retention of the buffer in the presence of adsorbed species. Close agreement between the simulations and the data was achieved with the new model. 相似文献
96.
C. de Duve 《Fresenius' Journal of Analytical Chemistry》1970,252(4-5):346-348
Summary Some recent developments in the field of tissue fractionation are briefly reviewed. Separation techniques have been improved considerably, thanks mainly to the construction of various automatic rotors for density gradient centrifugation. Progress has also been made in the analysis of the fractions, through automation of biochemical techniques, and especially through the use of quantitative morphological methods.
Trennverfahren subcellularer Teilchen
Zusammenfassung Ein Überblick über neuere Entwicklungen auf dem Gebiet der Gewebefraktionierung wird angegeben. Die Trennverfahren konnten wesentlich verbessert werden, hauptsächlich durch die Konstruktion verschiedener automatischer Rotoren zum Zentrifugieren mit Dichtegradient. Auch die Analyse der Fraktionen wurde durch Automation biochemischer Verfahren und besonders durch den Einsatz quantitativer morphologischer Methoden weitgehend verbessert.相似文献
97.
B. E. Krisyuk A. A. Popov G. E. Zaikov F. de Candia V. Vittoria R. Russo 《Colloid and polymer science》1987,265(3):220-225
The static modulus of elasticity (E) and the correlation time of rotation (
c
) of 2,-2,6,6-tetramethylpiperidine-1-oxyl are studied as a function of the temperature (210<T <350°K) for oriented films of isotactic polypropylene and polyethylene of high and low density.E and
c
change both upon heating and polymer orientation; this result indicates that sample properties are influenced by the microstructure of the amorphous phase where probes are localized. 相似文献
98.
Christian C. Van de Sande Syed Zahoor Ahmad Friedrich Borchers Karsten Levsen 《Journal of mass spectrometry : JMS》1978,13(11):666-670
Gaseous protonated aziridine ions are produced at the threshold from β-phenoxyethylamine molecular ions. The evidence for this is collisional activation spectra, using various precursors (including labelled analogues) under electron impact and field ionization conditions. Partial conversion to the acyclic \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH = }\mathop {\rm N}\limits^ + {\rm H}_{\rm 2} $\end{document} isomer occurs at higher electron energies and is rationalized by means of a potential energy surface constructed from energetic data. 相似文献
99.
Augustin de Castries 《Tetrahedron》2007,63(41):10330-10336
Azamacrocycles bearing four arylsulfonyl or arylsulfinyl pendant arms have been synthesised with good yields through nucleophilic addition of 1,4,8,11-tetraazacyclotetradecane (cyclam) to phenylvinylsulfone, phenylvinylsulfoxide or (R)-tolylvinylsulfoxide in isopropanol/water media. The crystal structure of the tetraethylsulfonylphenyl substituted macrocycle has been determined by X-ray crystallography. Preliminary studies of the coordination properties of these functionalised macrocyles towards Cu(II) and Eu(III) indicate that pendant sulfoxide groups act as oxygen donor coordinating groups. 相似文献
100.
Summary After a brief introduction of the subject, the paper focusses on the first step in any optimization procedure: the delineation
of the parameter space, wherein the global optimum is to be found. For organic modifier optimization in reversed-phase liquid
chromatography it is shown that the necessary information can be derived from a single water-methanol gradient. It first yields
an estimate of the total number of solutes in the sample, which is vital to define the peak capacity needed to achieve separation
at a certain confidence level. Next, the gradient allows the prediction of suitable isocratic methanol binary solvents, and
transfer rules formulate the iso-eluotropic composition of the common binary solvents (tetrahydrofuran and acetonitrile).
Because all predictions are based on a statistical analysis of a limited data base, attention is given to the practical situation
where an actual sample deviates from the average solute behaviour. Such deviations are revealed in the first isocratic run
and can be used to arrive at a better estimate of solute retention. 相似文献