全文获取类型
收费全文 | 166篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学 | 68篇 |
力学 | 14篇 |
数学 | 39篇 |
物理学 | 46篇 |
出版年
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 5篇 |
2012年 | 12篇 |
2011年 | 8篇 |
2010年 | 2篇 |
2009年 | 7篇 |
2008年 | 11篇 |
2007年 | 10篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1971年 | 7篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1958年 | 1篇 |
1954年 | 1篇 |
1930年 | 1篇 |
1911年 | 1篇 |
排序方式: 共有167条查询结果,搜索用时 15 毫秒
1.
A test statistic is developed that checks the validity of the extreme value conditions without specifiying the shape parameter of the limiting extreme value distribution. 相似文献
2.
3.
G. Wytze Meindersma Lara M. Galán Sánchez Antje R. Hansmeier André B. de Haan 《Monatshefte für Chemie / Chemical Monthly》2007,138(11):1125-1136
Summary. Ionic liquids offer tremendous opportunities to intensify reactions and separations in process technologies by tuning their
physical and chemical properties. Several ionic liquids are suitable for the separation of aromatic and aliphatic hydrocarbons.
CO2 absorption behavior was influenced by the functionalized chains appended to the room temperature ionic liquid (RTIL) cation.
Ionic liquids seem able to combine the chemical features of amine solutions with the characteristic advantages of the physical
solvents used for CO2 absorption. 相似文献
4.
Alex B. Scholten Jan W. de Haan Hans-Gerd Janssen Leo J. M. van de Ven Carel A. Cramers 《Journal of separation science》1997,20(1):17-23
Retention gape deactivated with Silicone OV-1701-OH show good chromatographic performance and remarkable stability against water induced stationary phase degradrdation. In an attempt to better understand the findamentals off the deactivation process using silanol terminated polysiloxanes, a fumed silica was deactivated with Silicon OV-1701-OH. In contrast to fused silic capillaries, fumed silica (Aerosil A-200) can be studied by 29Si cross-polarization magic-angle-spinning (CPMAS) NMR, thus serving as a model substrate for fused silica. Retention data from inverse gas chromatography at infinite dilurion and 29Si CP MAS NMR data of five Aerosil phases, differing in residual silanol surface concentration, are correlated with the aim of validating this approach for stationary phase characterization. A comparatively detailed model of the deactivating polymer layer that explains the observed absorption activities is deduced. Surface silanols are shown to play a key role in the polymer layer, the structure of which is of primary importance for the absorption behavior after deactivation. Contrary to common belief, the absolute silanol surface concentration after deativation is only of secondary importance for the overall absorption activity. High silanol surface concentrations enhance degradation of the polysiloxane chains into small cyclic fragments as well as subsequent absorption and immobolization to the silica substrate surface. The mobility of linear polysiloxane chains in the kHz regime (as determined bby NMR cross-polarization dynamics) appears to determine the extent which the residual silanols are accessible for analytes. It is therefore anticipated that there is an optimum silanol surface concentration of fused silica surfaces to be deactivated with silanol terminated polysiloxanes; it should be lazrge enough to adsord polymer fragments, but not large to avoid excessive residual silanol activity. 相似文献
5.
In an Internet auction, the expected payoff acts as a benchmark of the reasonableness of the price that is paid for the purchased
item. Since the number of potential bidders is not observable, the expected payoff is difficult to estimate accurately. We
approach this problem by considering the bids as a record and 2-record sequence of the potential bidder’s valuation and using
the Extreme Value Theory models to model the tail distribution of the bidder’s valuation and study the expected payoff. Along
the discussions for three different cases regarding the extreme value index γ, we show that the observed payoff does not act as an accurate estimation of the expected payoff in all the cases except a
subclass of the case γ = 0. Within this subclass and under a second order condition, the observed payoff consistently converges to the expected
payoff and the corresponding asymptotic normality holds.
相似文献
6.
We use classical simulations to analyze the dynamics of nonsequential double-electron short-pulse photoionization. We utilize a microcanonical ensemble of 10(5) two-electron "trajectories," a number large enough to provide large subensembles and even sub-subensembles associated with double ionization. We focus on key events in the final doubly ionized subensemble and back-analyze the subensemble's history, revealing a classical slow-down scenario for nonsequential double ionization. We analyze the dynamics of these slow-down collisions and find that a good phase match between the motions of the electrons can lead to very effective energy transfer, followed by escape over a suppressed barrier. 相似文献
7.
t-channel unitarity equations are derived for n-particle overlap functions. Together with s-channel unitarity they lead to scaling laws for the inelastic s-channel partial-wave amplitudes in the limits . Assuming the validity of the scaling law in the whole range, allowed by s-channel unitarity — i.e. for we obtain constant production cross sections σ(n)(s) at high energies s → ∞ up to s factors. 相似文献
8.
J. Schreurs C. A. H. Van Noorden-Mudde L. J. M. van de Ven J. W. de Haan 《Magnetic resonance in chemistry : MRC》1980,13(5):354-358
Direct and long-range 13C? 1H coupling constants are presented for the enone moieties of cyclopent-2-enone, cyclohex-2-enone and their protonated derivatives. A correlation is given between the experimental values and the results of quantum chemical calculations (CNDO/2, INDO). The existing calculations are modified in order to improve the relationship between the calculated and experimental results. 相似文献
9.
The proton NMR spectra of four cis/trans pairs of 1,2-disubstituted olefins have been analysed. The observed trends of the olefinic, vicinal and allylic proton-proton coupling constants are discussed in terms of rehybridization at the sp2 carbon atoms. It is found that in these substances the trans-allylic couplings are generally more negative than the cis-allylic couplings contrary to Barfield's1 theoretical prediction but in agreement with some earlier experimental data. Steric hindrance between cisoid substituents is cited as the probable origin of this end related trends. 相似文献
10.
Kastelein RA Janssen M Verboom WC de Haan D 《The Journal of the Acoustical Society of America》2005,118(2):1172-1179
Receiving beam patterns of a harbor porpoise were measured in the horizontal plane, using narrow-band frequency modulated signals with center frequencies of 16, 64, and 100 kHz. Total signal duration was 1000 ms, including a 200 ms rise time and 300 ms fall time. The harbor porpoise was trained to participate in a psychophysical test and stationed itself horizontally in a specific direction in the center of a 16-m-diameter circle consisting of 16 equally-spaced underwater transducers. The animal's head and the transducers were in the same horizontal plane, 1.5 m below the water surface. The go/no-go response paradigm was used; the animal left the listening station when it heard a sound signal. The method of constants was applied. For each transducer the 50% detection threshold amplitude was determined in 16 trials per amplitude, for each of the three frequencies. The beam patterns were not symmetrical with respect to the midline of the animal's body, but had a deflection of 3-7 degrees to the right. The receiving beam pattern narrowed with increasing frequency. Assuming that the pattern is rotation-symmetrical according to an average of the horizontal beam pattern halves, the receiving directivity indices are 4.3 at 16 kHz, 6.0 at 64 kHz, and 11.7 dB at 100 kHz. The receiving directivity indices of the porpoise were lower than those measured for bottlenose dolphins. This means that harbor porpoises have wider receiving beam patterns than bottlenose dolphins for the same frequencies. Directivity of hearing improves the signal-to-noise ratio and thus is a tool for a better detection of certain signals in a given ambient noise condition. 相似文献