全文获取类型
收费全文 | 14199篇 |
免费 | 1033篇 |
国内免费 | 1607篇 |
专业分类
化学 | 2847篇 |
晶体学 | 28篇 |
力学 | 730篇 |
综合类 | 178篇 |
数学 | 4062篇 |
物理学 | 1701篇 |
综合类 | 7293篇 |
出版年
2024年 | 31篇 |
2023年 | 128篇 |
2022年 | 189篇 |
2021年 | 232篇 |
2020年 | 262篇 |
2019年 | 301篇 |
2018年 | 295篇 |
2017年 | 325篇 |
2016年 | 367篇 |
2015年 | 360篇 |
2014年 | 611篇 |
2013年 | 765篇 |
2012年 | 719篇 |
2011年 | 767篇 |
2010年 | 684篇 |
2009年 | 861篇 |
2008年 | 982篇 |
2007年 | 1161篇 |
2006年 | 1080篇 |
2005年 | 921篇 |
2004年 | 821篇 |
2003年 | 766篇 |
2002年 | 696篇 |
2001年 | 586篇 |
2000年 | 554篇 |
1999年 | 412篇 |
1998年 | 378篇 |
1997年 | 282篇 |
1996年 | 228篇 |
1995年 | 204篇 |
1994年 | 175篇 |
1993年 | 123篇 |
1992年 | 121篇 |
1991年 | 93篇 |
1990年 | 72篇 |
1989年 | 56篇 |
1988年 | 52篇 |
1987年 | 44篇 |
1986年 | 24篇 |
1985年 | 20篇 |
1984年 | 21篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1976年 | 5篇 |
1973年 | 3篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
Brenda J. Latka 《Journal of Graph Theory》2003,42(3):165-192
A finite tournament T is tight if the class of finite tournaments omitting T is well‐quasi‐ordered. We show here that a certain tournament N5 on five vertices is tight. This is one of the main steps in an exact classification of the tight tournaments, as explained in [10]; the third and final step is carried out in [11]. The proof involves an encoding of the indecomposable tournaments omitting N5 by a finite alphabet, followed by an application of Kruskal's Tree Theorem. This problem arises in model theory and in computational complexity in a more general form, which remains open: the problem is to give an effective criterion for a finite set {T1,…,Tk} of finite tournaments to be tight in the sense that the class of all finite tournaments omitting each of T1,…,Tk is well‐quasi‐ordered. © 2003 Wiley Periodicals, Inc. J Graph Theory 42: 165–192, 2003 相似文献
112.
基于Karhunen-Loève变换和小波谱特征矢量量化的三维谱像数据压缩 总被引:1,自引:1,他引:0
提出了基于Karhunen Lo埁ve变换的小波谱特征矢量量化三维谱像数据压缩方法耍幔颍瑁酰睿澹?Lo埁ve变换 /小波变换 /小波谱特征矢量量化方法应用了Karhunen Lo埁ve变换的消除谱相关性优良性能 ,应用二维小波变换消除空间相关性 ,在小波变换域内应用二维集分割嵌入块编码和一维谱特征矢量量化对三维谱像数据压缩 ,获得较高的压缩性能。实验结果表明 :Karhunen Lo埁ve变换 /小波变换 /小波谱特征矢量量化编码比Karhunen Lo埁ve变换 /小波变换 /改进对块零树编码和Karhunen Lo埁ve变换 /小波变换 /快速矢量量化编码方法在同样压缩比条件下 ,峰值信噪比提高 2dB和 1dB以上 ,而速度提高了 1.5和 8倍 ,整体压缩性能有较大的提高 相似文献
113.
Heinz H. Bauschke Patrick L. Combettes 《Proceedings of the American Mathematical Society》2003,131(12):3757-3766
An iterative method is proposed to construct the Bregman projection of a point onto a countable intersection of closed convex sets in a reflexive Banach space.
114.
半参数回归模型中小波估计的随机加权逼近速度 总被引:10,自引:1,他引:9
把小波光滑方法和随机加权方法结合在一起,获得了半参数回归模型中参数分量的小波估计的随机加权逼近速度为σ(n^-1/2)。因此,从大样本意义上说,小波光滑方法和随机加权方法对半参数回归模型是可用的。 相似文献
115.
We study a GI/M/c type queueing system with vacations in which all servers take vacations together when the system becomes empty. These servers keep taking synchronous vacations until they find waiting customers in the system at a vacation completion instant.The vacation time is a phase-type (PH) distributed random variable. Using embedded Markov chain modeling and the matrix geometric solution methods, we obtain explicit expressions for the stationary probability distributions of the queue length at arrivals and the waiting time. To compare the vacation model with the classical GI/M/c queue without vacations, we prove conditional stochastic decomposition properties for the queue length and the waiting time when all servers are busy. Our model is a generalization of several previous studies. 相似文献
116.
Convergent Algorithm Based on Progressive Regularization for Solving Pseudomonotone Variational Inequalities 总被引:2,自引:2,他引:0
In this paper, we extend the Moreau-Yosida regularization of monotone variational inequalities to the case of weakly monotone and pseudomonotone operators. With these properties, the regularized operator satisfies the pseudo-Dunn property with respect to any solution of the variational inequality problem. As a consequence, the regularized version of the auxiliary problem algorithm converges. In this case, when the operator involved in the variational inequality problem is Lipschitz continuous (a property stronger than weak monotonicity) and pseudomonotone, we prove the convergence of the progressive regularization introduced in Refs. 1, 2. 相似文献
117.
118.
Condition monitoring and life prediction of the vehicle engine is an important and urgent problem during the vehicle development process. The vibration signals that are closely associated with the engine running condition and its development trend are complex and nonlinear. The chaos theory is used to treat the nonlinear dynamical system recently. A novel chaos method in conjunction with SVD (singular value decomposition)denoising skill are used to predict the vibration time series. Two types of time series and their prediction errors are provided to illustrate the practical utility of the method. 相似文献
119.
120.
本文研究了非线性应变波方程与Schr(?)dinger方程耦合系统Cauchy问题吸引 子的正则性.获得了该系统在空间Eo中存在整体吸引子Ao,并且Ao与E1中的强吸 引子A1相等. 相似文献