全文获取类型
收费全文 | 160篇 |
免费 | 1篇 |
专业分类
化学 | 54篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 12篇 |
物理学 | 90篇 |
出版年
2023年 | 1篇 |
2018年 | 1篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 1篇 |
2010年 | 6篇 |
2009年 | 3篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 10篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1938年 | 1篇 |
1899年 | 1篇 |
1874年 | 2篇 |
排序方式: 共有161条查询结果,搜索用时 7 毫秒
11.
Rolf MP Hofman MB Kuijer JP Pai VM Greiser A van Rossum AC Heethaar RM 《Magnetic resonance imaging》2009,27(3):385-392
Multiecho phase-contrast steady-state free precession (PC-SSFP) is a recently introduced sequence for flow quantification. In this multiecho approach, a phase reference and a velocity-encoded readout were acquired at different echo times after a single excitation. In this study, the sequence is validated in vitro for stationary flow. Subsequently, the sequence was evaluated on cardiac output measurements in vivo for through-plane flow in comparison to regular single gradient echo velocity quantification [phase-contrast spoiled gradient echo (PC-GE)]. In vitro results agreed with regular flow meters (RMS 0.1 cm/s). Cardiac output measurements with multiecho PC-SSFP on 10 healthy subjects gave on average the same results as the standard PC-GE. However, the limits of repeatability of PC-SSFP were significantly larger than those of PC-GE (2 l/min and 0.5 l/min, respectively, P=.001). The multiecho approach introduced some specific problems in vivo. The difference in echo times made the velocity maps sensitive for water-fat shifts and B(0)-drifts, which in turn made velocity offset correction problematic. Also, the addition of a single bipolar gradient cancelled the flow compensated nature of the SSFP sequence. In combination with the prolonged TR, this resulted in flow artifacts caused by high and pulsatile through-plane flow, affecting repeatability. Given the significantly lower repeatability of PC-SSFP, cardiac output in turn is less reliable, thus impairing the use of multiecho PC-SSFP. 相似文献
12.
13.
Barbara Marciniec M. Stawny Magdalena Hofman M. Naskrent 《Journal of Thermal Analysis and Calorimetry》2008,93(3):733-737
The study has been undertaken to check the effect of ionising radiation on the physical and chemical properties of florfenicol,
an antibiotic of a wide range of antibacterial activity. The solid-state samples were subjected to an electron beam generated
by accelerator corresponding to the doses of 25, 100 and 400 kGy, and the effect of the exposure was analysed by the methods
not requiring changes in the state (with no preliminary treatment), such as SEM, DSC, FTIR, XRD, EPR and HPLC.
Florfenicol irradiated with a dose of 25 kGy has not changed the form or colour, however, a small increase in intensity of
some absorption bands in the FTIR spectrum and of some peaks in the XRD pattern, a decrease in the melting point by 0.6°C,
the appearance of free radicals and a loss in the FF content within the error of the method (0.91%) have been observed. After
irradiation with greater doses (100 and 400 kGy) the changes have intensified, yellow discolouration appeared and the loss
of FF content has increased to 6.39%. As follows from the results, the compound studied in solid-state undergoes radiolysis
after e-beam irradiation in the doses ≥25 kGy, but lower doses (15–20 kGy) can be applied for its decontamination or sterilization
with no adverse effect on its physico-chemical properties. 相似文献
14.
Dr. Anton H. Hofman Dr. Mehedi Reza Prof. Janne Ruokolainen Prof. Gerrit ten Brinke Prof. Katja Loos 《Angewandte Chemie (International ed. in English)》2016,55(42):13081-13085
The formation of unusual multilayered parallel lamellae‐in‐lamellae in symmetric supramolecular double‐comb diblock copolymers is presented. While keeping the concentration of surfactant fixed, the number of internal layers was found to increase with molecular weight M up to 34 for the largest block copolymer. The number of internal structures n was established to scale as M0.67 and therefore enables easy design of such structures with great precision. 相似文献
15.
Laurent De Windt Detlef W. M. Hofman Lorenzo Pisani Enrico Clementi 《International journal of quantum chemistry》1995,53(2):131-147
The Coulomb–Hole–Hartree–Fock method introduced by E. Clementi in the early 1960s and reparametrized more recently by S. Chakraworty and E. Clementi to compute the correlated electronic energy in atomic systems, is here extended to compute molecules. The new parametrization is obtained empirically by fitting first and second atomic ionization potentials from He to Ca and a few diatomic molecules. The present formulation makes use of either one or more determinants in order to ensure proper dissociation products, following the early proposal of G.C. Lie and E. Clementi in the context of density functional computations for molecular systems. The new formulation is tested against the dissociation energies of a large number of molecules and it is found satisfactory. © 1995 John Wiley & Sons, Inc. 相似文献
16.
de Farias RF de Souza JM de Melo JV Airoldi C 《Journal of colloid and interface science》1999,212(1):123-129
The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press. 相似文献
17.
18.
19.
Supershell structure in alkali metal nanowires 总被引:1,自引:0,他引:1
Nanowires are formed by indenting and subsequently retracting two pieces of sodium metal. Their cross section gradually reduces upon retraction and the diameters can be obtained from the conductance. In previous work we have demonstrated that when one constructs a histogram of diameters from large numbers of indentation-retraction cycles such histograms show a periodic pattern of stable nanowire diameters due to shell structure in the conductance modes. Here, we report the observation of a modulation of this periodic pattern, in agreement with predictions of a supershell structure. 相似文献
20.
Kwok WK Olsson RJ Karapetrov G Paulius LM Moulton WG Hofman DJ Crabtree GW 《Physical review letters》2000,84(16):3706-3709
The critical points in untwinned YBa(2)Cu(3)O(7-delta) crystals with dilute columnar defects are investigated. We find a convergence of a first order vortex melting line with an irreversibility line associated with the onset of the Bose glass critical regime at the lower critical point. In addition, we find that columnar defects raise the upper critical point, implying that vortex line meandering is a basic feature controlling its position. 相似文献