全文获取类型
收费全文 | 135篇 |
免费 | 2篇 |
专业分类
化学 | 54篇 |
力学 | 10篇 |
数学 | 16篇 |
物理学 | 57篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 18篇 |
2012年 | 5篇 |
2011年 | 6篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 3篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 7篇 |
2002年 | 13篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有137条查询结果,搜索用时 15 毫秒
51.
SK. Musharaf Ali 《Molecular physics》2013,111(4):387-393
We propose a simple hybrid model for the shear viscosity of isotopic fluid mixtures by coupling the contribution of the Stokes–Einstein relation with the existing linear model of Roults's law for the shear viscosity. The calculated values of shear viscosity using this simple hybrid model are found to be in excellent agreement with the molecular dynamics (MD) simulation results. The calculated value of the shear viscosity obtained from the theoretical model as well as the MD simulation increases with increasing mass ratio. 相似文献
52.
An analysis is made of steady two-dimensional oblique stagnation-point flow and radiative heat transfer of an incompressible viscous fluid towards a shrinking sheet which is shrunk in its own plane with a velocity proportional to the distance from a fixed point. Here the axis of the stagnation flow and that of the shrinking sheet are not aligned. A similarity transformation reduces the Navier-Stokes equations to a set of non-linear ordinary differential equations and are solved numerically using a shooting technique. The analysis of the results obtained shows that multiple solutions exist for a certain range of the ratio of the shrinking velocity to the free stream velocity. The effect of non-alignment for the wall shear stress and the horizontal velocity components are discussed. Streamline patterns are also shown for shrinking at the sheet with aligned and non-aligned cases. It is found that the temperature at a point in the fluid decreases with increase in effective Prandtl number (Pr eff ). The results pertaining to the present study indicate that as Pr eff increases, the rate of heat transfer also increases. The reported results are in good agreement with the available published work in the literature. 相似文献
53.
The effect of Nd3+ concentration on the CW and Q-switched laser performances at 1064 nm from Nd: YVO4 has been studied under diode laser pumping in identical laser configuration. The Nd3+ concentrations used were 1, 2 and 3 at.% in YVO4 crystals. Under the CW operations we have compared the thermal lensing effect, slope efficiencies and also the beam quality
at the fourth-order degeneracy configuration. Q-switching was done with the help of an acousto-optic modulator and we have
compared the pulses obtained from Nd: YVO4 laser with different doping concentration. It was found that the 1 at.%-doped crystal is the best, offering highest optical-to-optical
conversion efficiency (55%), lowest fractional heat load (24%), highest pulse energy (80 μJ) and shortest pulse width (20 ns). It was also found that there was not much difference in performances for 2 and 3 at.%-doped
crystals both in CW and Q-switched configurations. 相似文献
54.
Biological stabilization of urea is a two staged process; (i) urea hydrolysis and (ii) ammonia stripping/nitrification-denitrification. Ammonia thus produced is either stripped off by usual methods or after converting into nitrate using chemoautotrophic bacteria. On denitrification, nitrate is finally converted into nitrogen gas by means of heterotrophic bacteria. Details of stabilization of urea from urea bearing wastewater using urea biohydrolyser are presented in this paper. 相似文献
55.
On 3-D graphical representation of DNA primary sequences and their numerical characterization 总被引:8,自引:0,他引:8
Randić M Vracko M Nandy A Basak SC 《Journal of chemical information and computer sciences》2000,40(5):1235-1244
In this article we (1) outline the construction of a 3-D "graphical" representation of DNA primary sequences, illustrated on a portion of the human beta globin gene; (2) describe a particular scheme that transforms the above 3-D spatial representation of DNA into a numerical matrix representation; (3) illustrate construction of matrix invariants for DNA sequences; and (4) suggest a data reduction based on statistical analysis of matrix invariants generated for DNA. Each of the four contributions represents a novel development that we hope will facilitate comparative studies of DNA and open new directions for representation and characterization of DNA primary sequences. 相似文献
56.
57.
Barluenga J Nandy SK Laxmi YR Suárez JR Merino I Flórez J García-Granda S Montejo-Bernardo J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(23):5725-5736
The sequential low-temperature addition reaction of an organolithium compound and methyl triflate to (menthyloxy)(3-furyl)carbene complexes of chromium and tungsten proceeded with excellent regioselectivity (1,4-addition) and diastereoselectivity (2,3-trans disposition of the nucleophile and electrophile groups) to afford new 2,3-disubstituted (2,3-dihydro-3-furyl)carbene complexes. In addition, a high degree of diastereofacial selectivity was achieved by employing alkenyllithium compounds. After detachment of both the metal fragment and the chiral auxiliary group, trisubstituted 2,3-dihydrofuran derivatives containing a quaternary stereogenic center at the C3 position were obtained. The characterization, including X-ray crystallography, of a novel type of stable four-membered chelate (eta(2)-alkene)tetracarbonylcarbene complex of chromium is also reported. 相似文献
58.
The Raman spectra of 3-methyl 2-butanethiol in the temperature range-120° C to + 60° C have been recorded together with its
liquid phase infrared spectrum at room temperature. The spectral analysis shows that the molecule of the compound exists in
the liquid state, in three different rotameric configurationsA, B andC of which the formA is the stablest. Besides, a tentative assignment of the observed vibrational frequencies arising from the rotameric forms
has been presented. 相似文献
59.
Peroxysome proliferator-activated receptors (PPARs) have grown greatly in importance due to their role in the metabolic profile. Among three subtypes (α, γ and δ), we here consider the least investigated δ subtype to explore the molecular fingerprints of selective PPARδ agonists. Validated QSAR models (regression based 2D-QSAR, HQSAR and KPLS) and molecular docking with dynamics analyses support the inference of classification-based Bayesian and recursive models. Chemometric studies indicate that the presence of ether linkages and heterocyclic rings has optimum influence in imparting selective bioactivity. Pharmacophore models and docking with molecular dynamics analyses postulate the occurrence of aromatic rings, HB acceptor and a hydrophobic region as crucial molecular fragments for development of PPARδ modulators. Multi-chemometric studies suggest the essential structural requirements of a molecule for imparting potent and selective PPARδ modulation. 相似文献
60.
[18F]-3′-deoxy-3′-fluorothymidine ([18F]FLT) is an established positron emission tomograph (PET)—radiopharmaceutical to study cell-proliferation rate in tumors.
Very low practical yield, uncertain and time-consuming high performance liquid chromatography (HPLC) purification, are the
main obstacles for the routine use of [18F]FLT in clinical PET. To obviate these difficulties, we have developed a fully automated radiosynthesis procedure for [18F]FLT using 5′-O-(4,4′-dimethoxytriphenylmethyl)-2,3′-anhydro-thymidine (DMTThy) and simplified single neutral alumina column purification.
The [18F]FLT yield was 8.48 ± 0.93% (n = 5) (without radioactive decay correction) in a synthesis time of 68 ± 3 min. The radiochemical purity was greater than
95% as confirmed by analytical HPLC using reference standard FLT and also free of non-radioactive impurity. Soluble aluminum
in the final product was much below the permissible limits. Di-methyl sulfoxide (DMSO), the reaction medium, could be detected
in the final product in trace amounts, well below the permissible levels. The synthesized [18F]FLT was sterile and bacterial endotoxin free by appropriate tests. PET imaging study in normal rabbits showed distinct localization
of [18F]FLT in organs having rapid cell division rate like bone marrow, guts and snout and the excretion was through the renal route.
There were no significant uptakes in bone and brain. The former finding confirms the in vivo stability of the [18F]FLT. This simplified radiosynthesis procedure can easily be adapted in any commercial or indigenous [18F]FDG synthesis module for routine [18F]FLT synthesis without the need of additional automation for HPLC purification. 相似文献