全文获取类型
收费全文 | 214篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 97篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 95篇 |
物理学 | 24篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 1篇 |
2016年 | 15篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 16篇 |
2012年 | 17篇 |
2011年 | 10篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 6篇 |
2005年 | 9篇 |
2004年 | 14篇 |
2003年 | 2篇 |
2002年 | 10篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有221条查询结果,搜索用时 156 毫秒
101.
A projection MR technique for imaging the velocity profiles of moving fluids has been applied to various steady flow models designed to simulate a variety of flow conditions. From such profiles can be readily deduced peak velocities, volume flow rates, information concerning the degree of flow development, features such as flow separation, and estimates shear stresses at the vessel wall. 相似文献
102.
Nikolaos N. Louros Fotis A. Baltoumas Stavros J. Hamodrakas Vassiliki A. Iconomidou 《Journal of computer-aided molecular design》2016,30(2):153-164
Pmel17 is a multidomain protein involved in biosynthesis of melanin. This process is facilitated by the formation of Pmel17 amyloid fibrils that serve as a scaffold, important for pigment deposition in melanosomes. A specific luminal domain of human Pmel17, containing 10 tandem imperfect repeats, designated as repeat domain (RPT), forms amyloid fibrils in a pH-controlled mechanism in vitro and has been proposed to be essential for the formation of the fibrillar matrix. Currently, no three-dimensional structure has been resolved for the RPT domain of Pmel17. Here, we examine the structure of the RPT domain by performing sequence threading. The resulting model was subjected to energy minimization and validated through extensive molecular dynamics simulations. Structural analysis indicated that the RPT model exhibits several distinct properties of β-solenoid structures, which have been proposed to be polymerizing components of amyloid fibrils. The derived model is stabilized by an extensive network of hydrogen bonds generated by stacking of highly conserved polar residues of the RPT domain. Furthermore, the key role of invariant glutamate residues is proposed, supporting a pH-dependent mechanism for RPT domain assembly. Conclusively, our work attempts to provide structural insights into the RPT domain structure and to elucidate its contribution to Pmel17 amyloid fibril formation. 相似文献
103.
104.
Papakostas Konstantinos T. Pavlou Stavros Papadopoulos Agis M. 《Journal of Thermal Analysis and Calorimetry》2020,141(1):435-445
Journal of Thermal Analysis and Calorimetry - Heating degree days (HDDs) and cooling degree days (CDDs) are widespread climatic indicators that depict the extremity and duration of ambient air... 相似文献
105.
The reaction of succinamic acid (H2sucm) with Ca(NO3)2·4H2O yielded compounds [Ca(Hsucm)(NO3)(H2O)]n (1) and [Ca(Hsucm)2]n (2). The succinamate(-1) ligand presents two new ligation modes and coordinates through the two carboxylato and the amide O-atoms, thus bridging three CaII ions which assemble into zig-zag 1D chains in 1 and 2D networks in 2. Intermolecular hydrogen bonding interactions in the crystal structures of 1 and 2 result in overall 3D framework structures. Both compounds have been characterized by IR and 1H NMR spectroscopy, and their thermal decomposition was monitored by TG/DTG and DSC measurements. The structural comparison of 1 and 2 with known lanthanide(III) succinamate(-1) complexes reveals differences in the coordination mode of the ligand and in the coordination number of the metal ions; the biological relevance of these differences is discussed. 相似文献
106.
A classical spin network consists of a ribbon graph (i.e., an abstract graph with a cyclic ordering of the vertices around
each edge) and an admissible coloring of its edges by natural numbers. The standard evaluation of a spin network is an integer
number. In a previous paper, we proved an existence theorem for the asymptotics of the standard evaluation of an arbitrary
classical spin network when the coloring of its edges are scaled by a large natural number. In the present paper, we extend
the results to the case of an evaluation of quantum spin networks of arbitrary valency at a fixed root of unity. As in the
classical case, our proofs use the theory of G-functions of André, together with some new results concerning holonomic and q-holonomic sequences of Wilf-Zeilberger. 相似文献
107.
Lalas S Gortzi O Athanasiadis V Tsaknis J Chinou I 《Molecules (Basel, Switzerland)》2012,17(3):2330-2334
The antimicrobial activity of the oil extracted with n-hexane from the seeds of Moringa peregrina was tested against Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Candida albicans, C. tropicalis and C. glabrata. The oil proved effective against all of the tested microorganisms. Standard antibiotics (netilmycin, 5-flucytocine, intraconazole and 7-amino-4-methylcoumarin-3-acetic acid) were used for comparison. The resistance to oxidation of the extracted seed oil was also determined. 相似文献
108.
Yu H Evans NL Stavros VG Ullrich S 《Physical chemistry chemical physics : PCCP》2012,14(18):6266-6272
Imidazole acts as a subunit in the DNA base adenine and the amino acid histidine-both important biomolecules which display low fluorescence quantum yields following UV excitation. The low fluorescence quantum yields are attributed to competing non-radiative excited state relaxation pathways that operate on ultrafast timescales. Imidazole is investigated here as a model compound due to its accessibility to high level ab initio calculations and time-resolved gas-phase spectroscopic techniques. Recent non-adiabatic dynamics simulations have identified three non-radiative relaxation mechanisms which are active following 6.0-6.2 eV excitation. Presented herein is a comprehensive investigation of each mechanism using a combination of femtosecond time-resolved ion yield and total kinetic energy release spectroscopies to monitor the formation of associated photoproducts. Relaxation along the (1)πσ state constitutes the predominant deactivation pathway. Timescales for NH-dissociation are extracted and distinguished from alternative H-atom sources based on their kinetic energy distributions. Larger photoproducts are observed to a lesser extent and attributed to ring fragmentation following NH-puckering and CN-stretching relaxation paths. 相似文献
109.
110.
We study portfolio credit risk management using factor models, with a focus on optimal portfolio selection based on the tradeoff
of expected return and credit risk. We begin with a discussion of factor models and their known analytic properties, paying
particular attention to the asymptotic limit of a large, finely grained portfolio. We recall prior results on the convergence
of risk measures in this “large portfolio approximation” which are important for credit risk optimization. We then show how
the results on the large portfolio approximation can be used to reduce significantly the computational effort required for
credit risk optimization. For example, when determining the fraction of capital to be assigned to particular ratings classes,
it is sufficient to solve the optimization problem for the large portfolio approximation, rather than for the actual portfolio.
This dramatically reduces the dimensionality of the problem, and the amount of computation required for its solution. Numerical
results illustrating the application of this principle are also presented.
JEL Classification G11 相似文献