全文获取类型
收费全文 | 2173篇 |
免费 | 249篇 |
国内免费 | 360篇 |
专业分类
化学 | 1139篇 |
晶体学 | 8篇 |
力学 | 28篇 |
综合类 | 20篇 |
数学 | 692篇 |
物理学 | 895篇 |
出版年
2023年 | 56篇 |
2022年 | 71篇 |
2021年 | 75篇 |
2020年 | 94篇 |
2019年 | 72篇 |
2018年 | 53篇 |
2017年 | 60篇 |
2016年 | 62篇 |
2015年 | 94篇 |
2014年 | 167篇 |
2013年 | 175篇 |
2012年 | 212篇 |
2011年 | 180篇 |
2010年 | 156篇 |
2009年 | 183篇 |
2008年 | 218篇 |
2007年 | 184篇 |
2006年 | 172篇 |
2005年 | 112篇 |
2004年 | 46篇 |
2003年 | 58篇 |
2002年 | 35篇 |
2001年 | 43篇 |
2000年 | 29篇 |
1999年 | 39篇 |
1998年 | 33篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 38篇 |
1987年 | 11篇 |
1986年 | 1篇 |
1985年 | 3篇 |
排序方式: 共有2782条查询结果,搜索用时 15 毫秒
131.
该文讨论了如下具有退化粘性的非齐次双曲守恒律方程的Cauchy问题$\left\{\begin{array}{l} u_t+f(u)_x=a^2t^\alpha u_{xx}+g(u),\ \ \ x\in{\bf R},\ \ \ t>0,\\u(x,0)=u_0(x) \in L^\infty({\bf R}).\end{array}\right.\eqno{({\rm I})}$其中$f(u), g(u)$是${\bf R}$上的光滑函数, $a>0, 0<\alpha<1$均为常数.在此条件下, 作者首先给出了Cauchy问题(I)的局部解的存在性, 再利用极值原理获得了解的$L^{\infty}$估计, 从而证明了Cauchy问题(I)整体光滑解的存在性. 相似文献
132.
Ting Cheng 《Journal of Differential Equations》2008,244(4):766-802
The blow-up rate estimate for the solution to a semilinear parabolic equation ut=Δu+V(x)|u|p−1u in Ω×(0,T) with 0-Dirichlet boundary condition is obtained. As an application, it is shown that the asymptotic behavior of blow-up time and blow-up set of the problem with nonnegative initial data u(x,0)=Mφ(x) as M goes to infinity, which have been found in [C. Cortazar, M. Elgueta, J.D. Rossi, The blow-up problem for a semilinear parabolic equation with a potential, preprint, arXiv: math.AP/0607055, July 2006], is improved under some reasonable and weaker conditions compared with [C. Cortazar, M. Elgueta, J.D. Rossi, The blow-up problem for a semilinear parabolic equation with a potential, preprint, arXiv: math.AP/0607055, July 2006]. 相似文献
133.
Jia-Rong Chen 《Tetrahedron》2009,65(45):9238-5287
An efficient and novel organocatalyst has been developed for the asymmetric desymmetrization of meso- and prochiral ketones by direct Michael addition to nitroolefins. This strategy can afford the desymmetrization products with excellent diastereo- (up to >99:1) and enantioselectivity (up to 96%) in great yields (up to 95%). 相似文献
134.
This is a continuation of the article(Comm.Partial Differential Equations 26(2001)965).In this article,the authors consider the one-dimensional compressible isentropic Navier-Stokes equations with gravitational force,fixed boundary condition,a general pressure and the density-dependent viscosity coefficient when the viscous gas connects to vacuum state with a jump in density.Precisely,the viscosity coefficient μ is proportional to ρ^θ and 0〈θ〈1/2,where ρ is the density,and the pressure P=P(ρ)is a general pressure.The global existence and the uniqueness of weak solution are proved. 相似文献
135.
136.
By variational methods, for a kind of Yamabe problem whose scalar curvature vanishes in the unit ball BN and on the boundary S^N-1 the mean curvature is prescribed, we construct multi-peak solutions whose maxima are located on the boundary as the parameter tends to 0^+ under certain assumptions. We also obtain the asymptotic behaviors of the solutions. 相似文献
137.
138.
The non-thermal phase transition in high energy collisions is studied in detail in the framework of random cascade model.
The relation between the characteristic parameter Ap, of phase transition and the rank q of moment is obtained using Monte Carlo simulation, and the existence of two phases in
self-similar cascading multiparticle systems is shown. The relation between the critical point qc of phase transition on the
fluctuation parameter a is obtained and compared with the experimental results from NA22. The same study is carried out also
by analytical calculation under central limit approximation. The range of validity of the central limit approximation is discussed. 相似文献
139.
Qintao Deng 《Archiv der Mathematik》2008,90(4):360-373
In this paper, we consider complete hypersurfaces in R
n+1 with constant mean curvature H and prove that M
n
is a hyperplane if the L
2 norm curvature of M
n
satisfies some growth condition and M
n
is stable. It is an improvement of a theorem proved by H. Alencar and M. do Carmo in 1994. In addition, we obtain that M
n
is a hyperplane (or a round sphere) under the condition that M
n
is strongly stable (or weakly stable) and has some finite L
p
norm curvature.
Received: 14 July 2007 相似文献
140.
This article is contributed to the Cauchy problem u/t = △u K(ㄧxㄧ)up in Rn x (0,T), u(x,0) =(ψ)(x) in Rn; with initial function(ψ)≠0. The stability of positive radial steady state, which are positive solutions of △u K(ㄧxㄧ)up =0, is obtained when p is critical for general K(ㄧxㄧ). 相似文献