全文获取类型
收费全文 | 5056篇 |
免费 | 510篇 |
国内免费 | 445篇 |
专业分类
化学 | 845篇 |
晶体学 | 32篇 |
力学 | 543篇 |
综合类 | 81篇 |
数学 | 2890篇 |
物理学 | 1620篇 |
出版年
2023年 | 56篇 |
2022年 | 62篇 |
2021年 | 89篇 |
2020年 | 121篇 |
2019年 | 151篇 |
2018年 | 119篇 |
2017年 | 158篇 |
2016年 | 162篇 |
2015年 | 109篇 |
2014年 | 187篇 |
2013年 | 417篇 |
2012年 | 191篇 |
2011年 | 219篇 |
2010年 | 193篇 |
2009年 | 274篇 |
2008年 | 229篇 |
2007年 | 273篇 |
2006年 | 294篇 |
2005年 | 235篇 |
2004年 | 229篇 |
2003年 | 230篇 |
2002年 | 221篇 |
2001年 | 179篇 |
2000年 | 198篇 |
1999年 | 165篇 |
1998年 | 154篇 |
1997年 | 135篇 |
1996年 | 104篇 |
1995年 | 82篇 |
1994年 | 79篇 |
1993年 | 73篇 |
1992年 | 61篇 |
1991年 | 58篇 |
1990年 | 50篇 |
1989年 | 37篇 |
1988年 | 58篇 |
1987年 | 53篇 |
1986年 | 37篇 |
1985年 | 46篇 |
1984年 | 38篇 |
1983年 | 14篇 |
1982年 | 32篇 |
1981年 | 23篇 |
1980年 | 19篇 |
1979年 | 25篇 |
1978年 | 27篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1974年 | 4篇 |
1973年 | 7篇 |
排序方式: 共有6011条查询结果,搜索用时 390 毫秒
61.
This paper deals with two mixed nonlinear boundary value problems depending on a parameter λ. For each of them we prove the existence of at least three generalized solutions when λ lies in an exactly determined open interval. Usefulness of this information on the interval is then emphasized by means of some consequences. Our main tool is a very recent three critical points theorem stated in [Topol. Methods Nonlinear Anal. 22 (2003) 93-104]. 相似文献
62.
A. A. Kuznetsova V. I. Mikhailenko A. Yu. Popovskii 《Journal of Applied Spectroscopy》2004,71(5):648-653
Two types of absorption centers, one being related to monomers and the other to dimers, have been revealed by the method of statistical analysis of the normalized absorption spectra of a superthin interlayer of nitrobenzene of variable thickness formed on activated surfaces of quartz and barium fluoride and measured for different thicknesses of the interlayer. On a decrease in the interlayer thickness the concentration of dimers increases. 相似文献
63.
M. A. Noor 《Journal of Optimization Theory and Applications》2004,121(2):385-395
In this paper, we suggest and analyze some iterative methods for solving nonconvex variational inequalities using the auxiliary principle technique, the convergence of which requires either only pseudomonotonicity or partially relaxed strong monotonicity. Our proofs of convergence are very simple. As special cases, we obtain earlier results for solving general variational inequalities involving convex sets. 相似文献
64.
In a recent work (Int. J. Solids Struct. 37 (2000) 1561) by one of the authors, an extended system for calculating critical points of equilibrium paths in imperfect structures was presented. However, the extremum nature of these points was not analyzed explicitly in that paper. In this note, we will fill in the gap and establish a sufficient condition for determining the buckling strength of imperfect structures. 相似文献
65.
Marco Caliari Marco Vianello Luca Bergamaschi 《Journal of Computational and Applied Mathematics》2007,210(1-2):56-63
We implement a second-order exponential integrator for semidiscretized advection–diffusion–reaction equations, obtained by coupling exponential-like Euler and Midpoint integrators, and computing the relevant matrix exponentials by polynomial interpolation at Leja points. Numerical tests on 2D models discretized in space by finite differences or finite elements, show that the Leja–Euler–Midpoint (LEM) exponential integrator can be up to 5 times faster than a classical second-order implicit solver. 相似文献
66.
二维渗流中的最短开穿透 总被引:1,自引:0,他引:1
在二维边渗流模型中,设/rn/=min(/r/:r是正方形「0,n」^2的开穿透),这里/r/表示r的长度,本文证明了在上临界状态有limE/rn//n=λ,在临界状态时,我们对E/n/给出了上界,并对一个rnrn给出了E/rn/的下界。 相似文献
67.
定义了拓扑指数Si(i=1,2,3,4),并选取包含双、三键、环及苯环的碳氢化合物为研究对象,计算了这些化合物的拓扑指数Si,同时用Si相关了它们的沸点.结果较文献值有所改善.并从Si中筛选出了S 相似文献
68.
SocaltheBerlinskitheoremforplanarquadraticSystem(QS)is:TheoremA[1]SupposethataQShas4finitecriticalpoints(CPs),Ifthequadrila... 相似文献
69.
A. A. Tolstonogov 《Set-Valued Analysis》1998,6(2):129-147
Existence theorems of continuous selectors whose values are fixed points of multivalued contractions are proved. As an application, the existence of continuous selectors to generalized solution sets of partial differential inclusions, depending on a parameter, is obtained. 相似文献
70.
Consider a queueing system where customers arrive at a circle according to a homogeneous Poisson process. After choosing their positions on the circle, according to a uniform distribution, they wait for a single server who travels on the circle. The server's movement is modelled by a Brownian motion with drift. Whenever the server encounters a customer, he stops and serves this customer. The service times are independent, but arbitrarily distributed. The model generalizes the continuous cyclic polling system (the diffusion coefficient of the Brownian motion is zero in this case) and can be interpreted as a continuous version of a Markov polling system. Using Tweedie's lemma for positive recurrence of Markov chains with general state space, we show that the system is stable if and only if the traffic intensity is less than one. Moreover, we derive a stochastic decomposition result which leads to equilibrium equations for the stationary configuration of customers on the circle. Steady-state performance characteristics are determined, in particular the expected number of customers in the system as seen by a travelling server and at an arbitrary point in time. 相似文献