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排序方式: 共有162条查询结果,搜索用时 265 毫秒
1.
In the present paper the problems of existence and uniqueness of almost periodic solutions for impulsive cellular neural networks with delay are considered. 相似文献
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L. K. Kostov W. Andrejtscheff L. G. Kostova A. Dewald G. Böhm K. O. Zell P. von Brentano 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(2):79-86
Applying delayed- r.f. coincidences and generalized centroid-shift analysis, nanosecond isomers in some odd-A iodine isotopes are studied in-beam. The reactions106Cd(12C,p2n) and116,118Sn(6Li,3n) have been used. The following half-lives were determined:T
1/2(565 keV)=0.50±0.10 ns andT
1/2(837 keV) =0.90±0.20 ns in115I,T
1/2(687 keV)=5.50±0.50 ns andT
1/2(2418 keV)=4.0±0.50 ns in119I as well asT
1/2(812 keV)=0.35±0.20 ns andT
1/2(445 keV)<0.10 ns=">0.10>121I. A systematics of the absolute probabilities for the transitions deexciting theg
9/2 9/2+ and
11/2 11/2
1
–
band heads in115–125I is presented and discussed.Partly supported by the Bulgarian National Research Foundation under contracts PH14, and PH31 and Kernforschungszentrum Karlsruhe, Stabsabteilung Internationale Beziehungen 相似文献
4.
New substrates and reaction conditions which may be expected to yield phenyl cation intermediates have been investigated. The approaches used were: (a) solvolysis of PhX in fluorinated alcohols, where X = ? N (O) = NOTs (tosyloxyazoxy), ? N (O) = NONf (Nf = C4F9SO) and ? OSO2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm + } $\end{document} (CH3)3ōTf (Tf=CF3SO); (b) solvolysis of ArBr, PhOTf and PhOSO2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm + } $\end{document}(CH3)3ōTf (phenyl ‘betylate triflate’) in super-acid solvents (FSO3H · SbF5, SbF5, AgSbF6). Analysis of the product mixtures provided no evidence for the intermediacy of phenyl cations as a major pathway in any of the reactions. This result is remarkable, since the ‘betylate’, for example, is a better leaving group by a factor of at least 105 than the ‘super’ leaving group triflate in the solvolysis of alkyl sulfonates. These results are a further indication of the extremely low stability of phenyl cations, as well as of the very special properties of the nitrogen leaving group in arenediazonium ions. 相似文献
5.
L. G. Kostova W. Andrejtscheff L. K. Kostov L. Funke E. Will A. I. Vdovin 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(2):145-148
Using the (,n) reaction, the half-life of the first 11/2– level in97Mo has been determined as T1/2(1437.0 keV)=2.5±0.3 ns by means of the pulsed beam method. The experimentally obtainedB(M2) value between theh
11/2 andg
7/2 configurations in97Mo has been satisfactorily described within the quasiparticle-phonon model usingg
s
eff
=0.6g
s
free
. Similar calculations and comparisons with experminental data have been performed also for95,99Mo as well as for99Ru and101Pd.This work is partly supported by the Bulgarian National Research Foundation 相似文献
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The nonlinear, nonnegative single‐mixture blind source separation problem consists of decomposing observed nonlinearly mixed multicomponent signal into nonnegative dependent component (source) signals. The problem is difficult and is a special case of the underdetermined blind source separation problem. However, it is practically relevant for the contemporary metabolic profiling of biological samples when only one sample is available for acquiring mass spectra; afterwards, the pure components are extracted. Herein, we present a method for the blind separation of nonnegative dependent sources from a single, nonlinear mixture. First, an explicit feature map is used to map a single mixture into a pseudo multi‐mixture. Second, an empirical kernel map is used for implicit mapping of a pseudo multi‐mixture into a high‐dimensional reproducible kernel Hilbert space. Under sparse probabilistic conditions that were previously imposed on sources, the single‐mixture nonlinear problem is converted into an equivalent linear, multiple‐mixture problem that consists of the original sources and their higher‐order monomials. These monomials are suppressed by robust principal component analysis and hard, soft, and trimmed thresholding. Sparseness‐constrained nonnegative matrix factorizations in reproducible kernel Hilbert space yield sets of separated components. Afterwards, separated components are annotated with the pure components from the library using the maximal correlation criterion. The proposed method is depicted with a numerical example that is related to the extraction of eight dependent components from one nonlinear mixture. The method is further demonstrated on three nonlinear chemical reactions of peptide synthesis in which 25, 19, and 28 dependent analytes are extracted from one nonlinear mixture mass spectra. The goal application of the proposed method is, in combination with other separation techniques, mass spectrometry‐based non‐targeted metabolic profiling, such as biomarker identification studies. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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9.
Daniela Nedeltcheva Vanya Kurteva Ivanka Topalova 《Rapid communications in mass spectrometry : RCM》2010,24(6):714-720
The tautomeric constants of a series of azo dyes were estimated in the gas phase by using electron ionization mass spectrometry. It was shown that the relative amount of the keto tautomer increases from 4‐phenylazo‐1‐phenol to 4‐phenylazo‐anthracen‐1‐ol, thus confirming the quantum‐chemical predictions. The existence of the enol tautomer of 4‐phenylazo‐anthracen‐1‐ol is shown for the first time by mass spectrometry in the gas phase. This finding is supported by flash photolysis measurements in solution. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
10.
T. Iossifova B. Mikhova I. Kostova 《Monatshefte für Chemie / Chemical Monthly》1995,126(11):1257-1264
Summary The isolation and structure elucidation of the secoiridoid hydroxyornoside is described. The behaviour of secoiridoid dilactones on acid methanolysis is discussed.
Ein Secoiridoiddilacton aus der Rinde vonFraxinus ornus
Zusammenfassung Die Isolierung und Strukturaufklärung des Secoiridoids Hydroxyornosid wird beschrieben. Das Verhalten von Secoiridoiddilactonen bezüglich saurer Methanolyse wird diskutiert.相似文献