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51.
A liquid-gas-phase tubing separator was designed and its operation studied in comparison with a PTFE tape-based separator. The relative efficiencies of the two separators were compared after injection into the carrier solution of a sample containing free chlorine using a chromatographic electron-capture detector for detection in the gaseous phase. The membrane separator contained porous PTFE tape whereas the tubular separator consisted of microporous PTFE membrane tubing. The two separators were compared with respect to sensitivity and reproducibility, simplicity of design and liability to interferences. Linear ranges and free chlorine detection limits were established for each of the two separators, that of the PTFE tape-based separator being 100 μg 1?1 and that of the tubing device 50 μg 1?1. 相似文献
52.
B. G. Zupančič 《Monatshefte für Chemie / Chemical Monthly》1962,93(6):1298-1302
Zusammenfassung Durch Einwirkung von konz. NaOH auf den wasserlöslichen Phenylmercuriamidokomplex ist es gelungen, Phenylmercuri-hydroxyd in genügend reiner Form zu erhalten. Bei der Reproduktion der an sich schon bekannter Verfahren zur Umwandlung des Phenylmercuriacetates in Phenylmercurihydroxyd wurde eine Verbesserung der Methode vonL. Bake erzielt.Kemijski institut Boris Kidri. 相似文献
53.
Trifluoroacetic acid-catalyzed liquid-phase fluorination with xenon difluoride of phenyl-substituted olefins, e.g. cis- and trans-1-phenylpropene and cis- and trans-stilbene, results in the formation of vicinal difluorides and fluoro-trifluoroacetates. The reaction is non-stereospecific. d,1-Erythro and d,1-threo fluoro-trifluoroacetates are formed in a highly regiospecific Markovnikov manner in 50% yield. The formation of β-fluorocarbonium ions is suggested. 相似文献
54.
We show that the forward-backward asymmetry in top quark pair production can be enhanced by fields that transform nontrivially under the flavor group and satisfy minimal flavor violation, while at the same time the constraints from associated effects on the dσ(tt)/dM(tt) distribution, dijet resonance searches, same-sign top-pair production, and other phenomenology are satisfied. We work out two examples in detail: one where a scalar color antisextet field that is also an antisextet of SU(3)(U) enhances the forward-backward asymmetry and one where the enhancement arises from a vector color octet field that is also an octet of SU(3)(U). 相似文献
55.
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57.
Andreja Zupančič Valant Lovro Žiberna Yannis Papaharilaou Andreas Anayiotos Georgios C. Georgiou 《Rheologica Acta》2011,50(4):389-402
During the complicated cardiac surgery on a non-beating heart with cardiopulmonary bypass, protection of the heart is accomplished
by injecting cold cardioplegic solutions. In most forms of circulatory shock, it is necessary to immediately restore the circulating
volume. Intravenous solutions of volume expanders, such as hydroxyethyl starch and dextrans, are used to increase the volume
of fluid in the circulating blood. In this work, blood samples of six donors were obtained and used to prepare mixtures with
different volume expanders in concentrations ranging from 10 to 50 vol./vol.%. The flow curves of all mixtures in the temperature
range from 4°C to 37°C were constructed and fitted to the Herschel–Bulkley model, in order to extract the shear thinning and
yield stress parameters. To assess the influence of the observed changes in the rheological properties of blood on the hemodynamics
in arterial vasculature, a realistic three-dimensional rigid-wall computational model was constructed from MRI images of the
right carotid bifurcation obtained in vivo from a healthy male volunteer. The time-varying flow field was numerically computed
using the Newtonian model as well as the Herschel–Bulkley model with the Papanastasiou regularization. The numerical simulations
indicate only moderate changes in the time-averaged flow field that become accentuated when the instantaneous flow field is
considered. We also found that although the influence of temperature, hematocrit, and volume expanders on hemodynamics is
significant, this can primarily be attributed to the changes in the nominal viscosity of the flow medium. 相似文献
58.
Jernej F. Kamenik Jing Shu Jure Zupan 《The European Physical Journal C - Particles and Fields》2012,72(8):1-19
Both CDF and DØ report a forward–backward asymmetry in $t\bar{t}$ production that is above the standard model prediction. We review new physics models that can give a large forward backward asymmetry in $t\bar{t}$ production at the Tevatron and the constraints these models face from searches for dijet resonances and contact interactions, from flavor physics and the $t\bar{t}$ cross section. Expected signals at the LHC are also reviewed. 相似文献
59.
A H2O2-HBr system and N-bromosuccinimide in an aqueous medium were used as a ‘green’ approach to electrophilic and radical bromination. Several activated and less activated aromatic molecules, phenylsubstituted ketones and styrene were efficiently brominated ‘on water’ using both systems at ambient temperature and without an added metal or acid catalyst, whereas various non-activated toluenes were functionalized at the benzyl position in the presence of visible light as a radical activator. A comparison of reactivity and selectivity of both brominating systems reveals the H2O2-HBr system to be more reactive than NBS for benzyl bromination and for the bromination of ketones, while for electrophilic aromatic substitution of methoxy-substituted tetralone it was higher for NBS. Also, higher yields of brominated aromatics were observed when using H2O2-HBr ‘on water’. Bromination of styrene reveals that not just the structure of the brominating reagent but the reaction conditions: amount of water, organic solvent, stirring rate and interface structure, play a key role in defining the outcome of bromination (dibromination vs bromohydroxylation). In addition, mild reaction conditions, a straightforward isolation procedure, inexpensive reagents and a lower environment impact make aqueous brominating methods a possible alternative to other reported brominating protocols. 相似文献
60.
The dual behavior phenomenon of alcohols in iodine-catalyzed esterification under solvent-free reaction conditions (SFRCs) is described; the governing factor is the stability of the carbonium ion generated from the alcohol; high concentration reaction conditions (HCRCs) or dilute solutions are much less suitable. In the case of benzylic alcohols, loss of optical activity was noted, whereas alkyl alcohols furnished a product with retention of stereochemistry. 相似文献