全文获取类型
收费全文 | 442篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
化学 | 268篇 |
晶体学 | 4篇 |
力学 | 14篇 |
数学 | 27篇 |
物理学 | 140篇 |
出版年
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 11篇 |
2012年 | 12篇 |
2011年 | 22篇 |
2010年 | 15篇 |
2009年 | 7篇 |
2008年 | 18篇 |
2007年 | 19篇 |
2006年 | 12篇 |
2005年 | 23篇 |
2004年 | 22篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 19篇 |
2000年 | 18篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1986年 | 4篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 9篇 |
1973年 | 6篇 |
1972年 | 7篇 |
1971年 | 3篇 |
1968年 | 5篇 |
1888年 | 3篇 |
排序方式: 共有453条查询结果,搜索用时 15 毫秒
141.
Free-energy perturbation (FEP) simulations have been applied to a series of analogues of the natural trisaccharide epitope of Salmonella serotype B bound to a fragment of the monoclonal anti-Salmonella antibody Se155-4. This system was selected in order to assess the ability of free-energy perturbation (FEP) simulations to predict carbohydrate-protein interaction energies. The ultimate goal is to use FEP simulations to aid in the design of synthetic high affinity ligands for carbohydrate-binding proteins. The molecular dynamics (MD) simulations were performed in the explicit presence of water molecules, at room temperature. The AMBER force field, with the GLYCAM parameter set for oligosaccharides, was employed. In contrast to many modeling protocols, FEP simulations are capable of including the effects of entropy, arising from differential ligand flexibilities and solvation properties. The experimental binding affinities are all close in value, resulting in small relative free energies of binding. Many of the DeltaDeltaG values are on the order of 0-1 kcal mol(-1), making their accurate calculation particularly challenging. The simulations were shown to reasonably reproduce the known geometries of the ligands and the ligand-protein complexes. A model for the conformational behavior of the unbound antigen is proposed that is consistent with the reported NMR data. The best agreement with experiment was obtained when histidine 97H was treated as fully protonated, for which the relative binding energies were predicted to well within 1 kcal mol(-1). To our knowledge this is the first report of FEP simulations applied to an oligosaccharide-protein complex. 相似文献
142.
We show that a magnetic flux tube can grow in strength and size provided the temperature increases outward at the edge of the tube where the axial magnetic field declines to its external value. The radius of the tube increases at a rate determined by our theory. It is the coincidence of temperature and magnetic field gradients of opposite sign that generates the new field, and if this is lost the tube ceases to grow. The phenomenon is illustrated by adopting plausible distributions for the temperature and magnetic field strength, which yield an expression for the rate of growth of the magnetic field magnitude B. The mechanism provides a possible explanation of the fibrous nature of solar magnetic fields. 相似文献
143.
We introduce a new phase-restricted algorithm for producing a heterogeneous correlation filter that permits new in-class members to be added without changing the phase of the filter. This heterogeneous correlation filter uses amplitude modulation both to enhance in-class cross correlations and to suppress selected out-of-class correlations. This new algorithm should substantially improve the performance of existing class-associative correlators and improve their operation. 相似文献
144.
The electrical properties of vacuum evaporated layers of CdS on amorphous substrates have been investigated as a function of the various preparative parameters, i.e. evaporation rate, substrate temperature, thickness of the layers and purity of the source. The degree of preferential orientation of the crystallites which comprise the film has also been examined. It is shown that the resistivity of the films decreases with increasing thickness. This effect is associated with a corresponding increase in the density of free electrons, which it is suggested is associated with an increasing deviation from stoichiometry of the source as the evaporation proceeds. The variation of the Hall mobility with thickness can be explained in terms of surface scattering. A tentative model of the evaporation process is proposed which gives some insight into many of the experimental observations. 相似文献
145.
We have measured the thermoelectric power of LaB6, PrB6 and NdB6 in the temperature range 2–20K. PrB6 and NdB6 order antiferromagnetically at TN = 6.99K and 7.74K respectively, whereas LaB6 is non-magnetic. The thermoelectric power data have a negative maximum near 5.5K in all three hexaborides. This negative peak is thought to be mainly due to phonon drag in LaB6. In PrB6 and NdB6 there is an additional contribution due to magnon drag. It is expected that the high temperature thermoelectric power is mainly due to an electron diffusion term and a contribution due to spin disorder scattering. The thermoelectric power and the resistivity have been compared in the vicinity of TN. A qualitative similarity in the temperature derivatives of these two quantities has been found for PrB6 and NdB6 near TN. 相似文献
146.
在44~77K温度范围内.在正向电压激发下的Cds MIS二极管中,观测到了发射0、1或2个纵光学(O、1LO或2LO)声子的自由激子的辐射衰减.根据激子的动能分布,讨论了1LO和2LO声子协助的伴线的形状和温度依赖.这里激子的有效温度等于晶格温度. 相似文献
147.
A theorem of Skubenko asserts that if L is a lattice in R5, then there exist positive real numbers λ1,…, λ5 such that L has five linearly independent points on the boundary of the ellipsoid and none other than the origin in its interior. A different proof of this result is given for the case when L has homogeneous minimum different from zero. 相似文献
148.
149.
150.
D.M.S. Bagguley J.P. Partington J.A. Robertson R.C. Woods 《Journal of magnetism and magnetic materials》1980,20(1):56-66
Measurements of magnetization, ac susceptibility and microwave absorption at 9.5 and 35 GHz, have been carried out with single crystals of Tb and Gd70Tb30. The critical temperatures for Tb were in agreement with previous published results. The Curie Temperature for Gd70Tb30 was measured to be (275 ± 2) K. Anisotropy constants have been derived from the microwave measurements. The value of K2 at 0 K is estimated to 8.8 × 108 erg cm-3 (Tb) and 1.3 × 108 erg cm-3 (Gd70Tb30). At 77 K, the value of K6 is estimated to be 6 × 104 erg cm-3 (Gd70Tb30. 相似文献