全文获取类型
收费全文 | 603篇 |
免费 | 28篇 |
国内免费 | 1篇 |
专业分类
化学 | 30篇 |
力学 | 4篇 |
数学 | 569篇 |
物理学 | 29篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 39篇 |
2018年 | 39篇 |
2017年 | 15篇 |
2016年 | 7篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 48篇 |
2012年 | 14篇 |
2011年 | 46篇 |
2010年 | 41篇 |
2009年 | 65篇 |
2008年 | 47篇 |
2007年 | 53篇 |
2006年 | 25篇 |
2005年 | 23篇 |
2004年 | 24篇 |
2003年 | 16篇 |
2002年 | 15篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 16篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
排序方式: 共有632条查询结果,搜索用时 187 毫秒
1.
The growth-fragmentation equation describes a system of growing and dividing particles, and arises in models of cell division, protein polymerisation and even telecommunications protocols. Several important questions about the equation concern the asymptotic behaviour of solutions at large times: at what rate do they converge to zero or infinity, and what does the asymptotic profile of the solutions look like? Does the rescaled solution converge to its asymptotic profile at an exponential speed? These questions have traditionally been studied using analytic techniques such as entropy methods or splitting of operators. In this work, we present a probabilistic approach: we use a Feynman–Kac formula to relate the solution of the growth-fragmentation equation to the semigroup of a Markov process, and characterise the rate of decay or growth in terms of this process. We then identify the Malthus exponent and the asymptotic profile in terms of a related Markov process, and give a spectral interpretation in terms of the growth-fragmentation operator and its dual. 相似文献
2.
3.
《印度化学会志》2023,100(6):100999
Cyclodextrins are natural oligosaccharides used to increase the solubility of drugs. It has numerous applications in drug discovery, food storage and other fields. Loftsson et al. explained about applications of Cyclodextrins(CDs) in administrating the drugs through various ways. Jansook et al. has given insights into the structure, physicochemical properties and pharmaceutical applications of CDs. In the present work, cyclodextrin and its derivatives such as α, β, γ CDs are studied for which various degree and neighborhood degree-based topological indices are computed through M-polynomial and NM-polynomial respectively and the comparison of the indices for all three types of cyclodextrins are presented which are of great importance in QSPR/QSAR studies. 相似文献
4.
《Mathematische Nachrichten》2017,290(17-18):2961-2976
A theory of ∞‐Besov capacities is developed and several applications are provided. In particular, we solve an open problem in the theory of limits of the ∞‐Besov semi‐norms, we obtain new restriction‐extension inequalities, and we characterize the pointwise multipliers acting on the ∞‐Besov spaces. 相似文献
5.
Shoukry El-Ganaini 《Journal of the Egyptian Mathematical Society》2017,25(1):19-27
In this paper, the first integral method combined with Liu's theorem is applied to integrate a new coupled nonlinear Schrodinger type equation. Using this combination, more new exact traveling wave solutions are obtained for the considered equation using ideas from the theory of commutative algebra. In addition, more solutions are also obtained via the application of semi-inverse variational principle due to Ji-Huan He. The used approaches with the help of symbolic computations via Mathematica 9, may provide a straightforward effective and powerful mathematical tools for solving nonlinear partial differential equations in mathematical physics. 相似文献
6.
Rupture of intracranial saccular aneurysms is the leading cause of spontaneous subarachnoid hemorrhage, which results in significant
morbidity and mortality. Although many have suggested that saccular aneurysms enlarge and rupture due to mechanical instabilities,
our recent nonlinear analyses suggest that at least certain classes of aneurysms do not exhibit a quasi-static limit point
instability or dynamic instabilities in response to periodic loading. Based on an increased understanding of the ubiquitous
role of growth and remodeling within the vasculature and recent histopathological data on saccular aneurysms, it is hypothesized
that a stress-mediated regulation of collagen turnover causes their enlargement. There is a need, however, for a theoretical
framework to explore this and competing hypotheses. In this paper, we present a 2-D constrained mixture model for growth and
remodeling of an ellipsoidally shaped saccular aneurysm and numerically simulate enlargement and changes in material symmetry
in the aneurysmal wall. Results suggest that ellipsoidal aneurysms tend toward spherical shapes, and a competition between
radial expansion and wall thickening plays a critical role in determining the stability of an enlarging lesion. 相似文献
7.
8.
The purpose of this paper is twofold. First of all we characterize Bernstein algebras having a nilpotent kernel using idempotents of their multiplication algebras. Secondly, we describe some properties of Bernstein algebras which are preserved by isomorphisms of their multiplication algebras. 相似文献
9.
Using chemical separations and radiometric measurements medium-half-life irradiation products of molybdenum with 12.5 MeV deuterons were determined (90Nb, 92Nb, 95mNb, 95Nb, 96Nb, 99Mo, 95mTc, 96Tc, 99mTc) as well as thick target yields for some of them: 92Nb (0.22 μCi/μAh), 95Nb(0.05 μCi/μAh), 99Mo (64 μCi/μAh), 95mTc(0.76 μCi/μAh), 96Tc((62.5 μCi/μAh). Moreover isolation possibiities of radioactive preparations from removed worn-cut molybdenum parts of the U-120 cycletron are discussed. 相似文献
10.
J. Christopher 《哲学杂志》2013,93(26):2992-3016
The flow and work-hardening behaviour of tempered martensitic P92 steel have been investigated using phenomenological constitutive model in the temperature range 300–873 K for the strain rates ranging from 3.16 × 10?5 to 1.26 × 10?3 s?1. The analysis indicated that the hybrid model reduced to Estrin–Mecking (E–M) one-internal-variable model at intermediate and high temperatures. Further, the analysis also indicated that dislocation dense martensite lath/cell boundaries and precipitates together act as effective barriers to dislocation glide in P92 steel. The flow behaviour of the steel was adequately described by the E–M approach for the range of temperatures and strain rates examined. Three distinct temperature regimes have been obtained for the variations in work-hardening parameters with respect to temperature and strain rate. Signatures of dynamic strain ageing in terms of the anomalous variations in work-hardening parameters at intermediate temperatures and the dominance of dynamic recovery at high temperatures have been observed. The evaluation of activation energy suggested that deformation is controlled by the dominance of cross-slip of dislocations at room and intermediate temperatures, and climb of dislocations at high temperatures. 相似文献