全文获取类型
收费全文 | 1398篇 |
免费 | 106篇 |
国内免费 | 140篇 |
专业分类
化学 | 298篇 |
晶体学 | 5篇 |
力学 | 106篇 |
综合类 | 20篇 |
数学 | 860篇 |
物理学 | 355篇 |
出版年
2024年 | 4篇 |
2023年 | 31篇 |
2022年 | 23篇 |
2021年 | 29篇 |
2020年 | 45篇 |
2019年 | 39篇 |
2018年 | 36篇 |
2017年 | 35篇 |
2016年 | 45篇 |
2015年 | 25篇 |
2014年 | 44篇 |
2013年 | 120篇 |
2012年 | 55篇 |
2011年 | 71篇 |
2010年 | 54篇 |
2009年 | 85篇 |
2008年 | 121篇 |
2007年 | 90篇 |
2006年 | 77篇 |
2005年 | 76篇 |
2004年 | 44篇 |
2003年 | 73篇 |
2002年 | 53篇 |
2001年 | 55篇 |
2000年 | 51篇 |
1999年 | 56篇 |
1998年 | 39篇 |
1997年 | 47篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 17篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有1644条查询结果,搜索用时 15 毫秒
121.
Plane quartics containing the ten vertices of a complete pentalateral and limits of them are called Lüroth quartics.The locus of singular Lüroth quartics has two irreducible components,both of codimension two in P14.We compute the degree of them and discuss the consequences of this computation on the explicit form of the Lüroth invariant.One important tool is the Cremona hexahedral equations of the cubic surface.We also compute the class in M 3 of the closure of the locus of nonsingular Lüroth quartics. 相似文献
122.
The modal dispersion characteristics of EM waves in a new unconventional plasma loaded doubly clad waveguide having a shape of the lemniscates of Bernoulli-type core cross-section have been studied analytically. The proposed waveguide has three parts namely the core with slighter high index, the inner cladding with plasma and the outer cladding with air. Now using the necessary orthogonal coordinates for the proposed structure and imposing the boundary conditions under the weak guidance condition, the modal characteristics equation has been obtained considering variations in plasma width and plasma frequency, the dispersion curves and cutoff frequencies have been obtained and presented in this paper. It is noted that as the width of plasma layer increases, the cutoff frequency also increases considerably in all considered cases. This shows that using plasma width as a new parameter we can control any particular mode on our wish. 相似文献
123.
Houyu Zhao 《Mathematical Methods in the Applied Sciences》2014,37(17):2689-2696
In this paper, we study the existence of analytic invariant curves of a iterative equation which from mosquito model. By constructing an invertible analytic solution g(x) of an auxiliary equation of the form invertible analytic solutions of the form g(αg ? 1(x)) for the original iterative functional equation are obtained. Besides the hyperbolic case 0 < | α | < 1, we focus on those α on the unit circle S1, that is, | α | = 1. We discuss not only those α at resonance, that is at a root of the unity, but also those α near resonance under the Brjuno condition. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
124.
A note on finding clothoids 总被引:2,自引:0,他引:2
The clothoid is a spiral that is used as transition curve in highway and railway route design. Although its defining formulas are transcendental functions, recent work has shown that it can be used fairly easily on small computers. A single nonlinear equation must be solved in each of four common arrangements of the clothoid. The purpose of this work is to give starting intervals for which Newton's root finding method applied to those equations is guaranteed to converge. 相似文献
125.
Based on liquid variational perturbation theory with quantum mechanics correction, the effective exp-6 potential is adopted to compute the shock Hugoniot of liquid H2 + D2 mixtures at different molar rations. An examination of the confidence of the above computation is performed by comparing experiments and calculations, in which similar calculation procedure used for H2 + D2 is adopted for H2 and D2 each, since no experimental data are available to conduct this kind of comparison. Good agreement in both comparisons is found. This fact may look as if an indirect positive verification of calculation procedure was used here at least in the pressure and temperature domain covered by the experimental data of H2 and D2 used for comparison, numerically nearly up to 20 GPa and 104 K. Project supported by the Science and Technology Foundation of China Academy of Engineering Physics (Grant No. 97Z011). 相似文献
126.
Matthew H. Baker 《Proceedings of the American Mathematical Society》1999,127(10):2851-2856
This paper gives a new proof of Kamienny's Criterion using the method of Coleman and Chabauty.
127.
Ivan Kausz 《Compositio Mathematica》1999,115(1):37-69
We define a natural discriminant for a hyperelliptic curve X of genus g over a field K as a canonical element of the (8g+4)th tensor power of the maximal exterior product of the vectorspace of global differential forms on X. If v is a discrete valuation on K and X has semistable reduction at v, we compute the order of vanishing of the discriminant at v in terms of the geometry of the reduction of X over v. As an application, we find an upper bound for the Arakelov self-intersection of the relative dualizing sheaf on a semistable hyperelliptic arithmetic surface. 相似文献
128.
David Kohel 《Journal of Number Theory》2011,131(5):894-919
The study of alternative models for elliptic curves has found recent interest from cryptographic applications, after it was recognized that such models provide more efficiently computable algorithms for the group law than the standard Weierstrass model. Examples of such models arise via symmetries induced by a rational torsion structure. We analyze the module structure of the space of sections of the addition morphisms, determine explicit dimension formulas for the spaces of sections and their eigenspaces under the action of torsion groups, and apply this to specific models of elliptic curves with parametrized torsion subgroups. 相似文献
129.
D. Boneh 《Journal of Number Theory》2011,131(5):832-841
We apply the Cocks-Pinch method to obtain pairing-friendly composite order groups with prescribed embedding degree associated to ordinary elliptic curves, and we show that new security issues arise in the composite order setting. 相似文献
130.
Complex formation between a nanoparticle and a weak polyelectrolyte chain: Monte Carlo simulations 总被引:1,自引:0,他引:1
Serge?Ulrich Abohachem?Laguecir Serge?StollEmail author 《Journal of nanoparticle research》2004,6(6):595-603
Understanding the complexation processes between nanoparticles and polyelectrolytes is an essential aspect in many branches of nanotechnology, nanoscience, chemistry, and biology to describe processes such as nanoparticle stabilization/destabilization and dispersion, water treatment, microencapsulation, complexation with biomolecules for example, and evolution of the interface of many natural and synthetic systems. In view of the complexity of such processes, applications are often based on empirical or semiempirical observations rather than on predictions based on theoretical or analytical models. In this study, the complex formation between an isolated weak polyelectrolyte and an oppositely charged nanoparticle is investigated using Monte Carlo simulations with screened Coulomb potentials in the grand canonical ensemble. The roles of the nanoparticle surface charge density , solution pH and ionic concentration Ci are systematically investigated. The phase diagrams of complex conformations are also presented. It is shown that the polyelectrolyte conformation at the surface of the nanoparticle is controlled by the attractive interactions with the nanoparticle but also by the repulsive interactions between the monomers. To bridge the gap with experiments titration curves are calculated. We clearly demonstrate that an oppositely charged nanoparticle can significantly modify the acid/base properties of a weak polyelectrolyte. 相似文献