全文获取类型
收费全文 | 458篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
化学 | 22篇 |
晶体学 | 1篇 |
力学 | 26篇 |
综合类 | 4篇 |
数学 | 332篇 |
物理学 | 95篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 15篇 |
2019年 | 9篇 |
2018年 | 5篇 |
2017年 | 11篇 |
2016年 | 9篇 |
2015年 | 6篇 |
2014年 | 18篇 |
2013年 | 25篇 |
2012年 | 25篇 |
2011年 | 28篇 |
2010年 | 24篇 |
2009年 | 21篇 |
2008年 | 27篇 |
2007年 | 27篇 |
2006年 | 15篇 |
2005年 | 15篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 6篇 |
1975年 | 2篇 |
排序方式: 共有480条查询结果,搜索用时 15 毫秒
1.
2.
Dr. Eduard O. Bobylev Julian Ruijter Dr. David A. Poole III Dr. Simon Mathew Prof. Dr. Bas de Bruin Prof. Dr. Joost N. H. Reek 《Angewandte Chemie (International ed. in English)》2023,62(16):e202218162
Metabolic pathways are highly regulated by effector molecules that influences the rate of enzymatic reactions. Inspired by the catalytic regulation found in living cells, we report a Pt2L4 cage of which the activity can be controlled by effectors that bind inside the cage. The cage shows catalytic activity in the lactonization of alkynoic acids, with the reaction rates dependent on the effector guest bound in the cage. Some effector guests enhance the rate of the lactonization by up to 19-fold, whereas one decreases it by 5-fold. When mixtures of specific substrates are used, both starting materials and products act as guests for the Pt2L4 cage, enhancing its catalytic activity for one substrate while reducing its activity for the other. The reported regulatory behavior obtained by the addition of effector molecules paves the way to the development of more complex, metabolic-like catalyst systems. 相似文献
3.
刘臻 《数学年刊A辑(中文版)》2017,38(2):201-214
研究了完全耦合正倒向随机控制系统的最优控制问题.得到了粘性解框架下的,控制变量同时出现在正倒向随机系统的漂移项和扩散项中的最优控制问题的验证定理.还讨论了验证定理在构造随机最优反馈控制中的应用. 相似文献
4.
《Communications in Nonlinear Science & Numerical Simulation》2014,19(5):1465-1473
This paper presents a study of multi-objective optimal design of full state feedback controls. The goal of the design is to minimize several conflicting performance objective functions at the same time. The simple cell mapping method with a hybrid algorithm is used to find the multi-objective optimal design solutions. The multi-objective optimal design comes in a set of gains representing various compromises of the control system. Examples of regulation and tracking controls are presented to validate the control design. 相似文献
5.
Nonlinear filter generators are commonly used as keystream generators in stream ciphers. A nonlinear filter generator utilizes a nonlinear filtering function to combine the outputs of a linear feedback shift register (LFSR) to improve the linear complexity of keystream sequences. However, the LFSR-based stream ciphers are still potentially vulnerable to algebraic attacks that recover the key from some keystream bits. Although the known algebraic attacks only require polynomial time complexity of computations, all have their own constraints. This paper uses the linearization of nonlinear filter generators to cryptanalyze LFSR-based stream ciphers. Such a method works for any nonlinear filter generators. Viewing a nonlinear filter generator as a Boolean network that evolves as an automaton through Boolean functions, we first give its linearization representation. Compared to the linearization representation in Limniotis et al. (2008), this representation requires lower spatial complexity of computations in most cases. Based on the representation, the key recoverability is analyzed via the observability of Boolean networks. An algorithm for key recovery is given as well. Compared to the exhaustive search to recover the key, using this linearization representation requires lower time complexity of computations, though it leads to exponential time complexity. 相似文献
6.
This article reviews the solutions that have been studied for the implementation of nonreciprocal devices in integrated optics. These components, either isolators or circulators, use the nonreciprocal interaction between light and a magnetic medium. The only two isolators that have been experimented on to date are described in detail with their advantages and drawbacks, and some solutions are proposed to overcome the difficulties encountered. 相似文献
7.
Synchronization in large ensembles of coupled interacting units is a fundamental phenomenon, which is helpful for the understanding of working mechanisms in neuronal networks, social network, etc. In this paper, we will investigate the synchronization phenomenon in a network model. A feedback control scheme is proposed for the synchronization of the given complex networks. The obtained result indicates that synchronization can be achieved for growing chaotic network model. Method enhance the synchronizability of the given model are given at the same time. Finally, numerical simulations are given to show the effectiveness of obtained results. 相似文献
8.
In an evidential reasoning context, a group consensus (GC) based approach can model multiple attributive group decision analysis problems with GC requirements. The predefined GC is reached through several rounds of group analysis and discussion (GAD) in the approach. However, the GAD with no guidance may not be the most appropriate way to reach the predefined GC because several rounds of GAD will spend a lot of time of all experts and yet cannot help them to effectively emphasize on the assessments which primarily damage the GC. In this paper, an attribute weight based feedback model is constructed to effectively identify the assessments primarily damaging the GC and accelerate the GC convergence. Considering important attributes with the weights more than or at least equal to the mean of the weights of all attributes, the feedback model constructs identification rules to identify the assessments damaging the GC for the experts to renew. In addition, a suggestion rule is introduced to generate appropriate recommendations for the experts to renew their identified assessments. The identification rules are constructed at three levels including the attribute, alternative and global levels. The feedback model is used to solve an engineering project management software selection problem to demonstrate its detailed implementation process, its validity and applicability, and its advantages compared with the GC based approach. 相似文献
9.
Towards a unified recurrent neural network theory: The uniformly pseudo-projection-anti-monotone net
In the past decades, various neural network models have been developed for modeling the behavior of human brain or performing
problem-solving through simulating the behavior of human brain. The recurrent neural networks are the type of neural networks
to model or simulate associative memory behavior of human being. A recurrent neural network (RNN) can be generally formalized
as a dynamic system associated with two fundamental operators: one is the nonlinear activation operator deduced from the input-output
properties of the involved neurons, and the other is the synaptic connections (a matrix) among the neurons. Through carefully
examining properties of various activation functions used, we introduce a novel type of monotone operators, the uniformly
pseudo-projectionanti-monotone (UPPAM) operators, to unify the various RNN models appeared in the literature. We develop a
unified encoding and stability theory for the UPPAM network model when the time is discrete. The established model and theory
not only unify but also jointly generalize the most known results of RNNs. The approach has lunched a visible step towards
establishment of a unified mathematical theory of recurrent neural networks. 相似文献
10.
A low-cost optical feedback system using dynamic mirrors has been developed at the NSLS for stabilizing the position and direction of an infrared synchrotron beam against thermal drift and mechanical noise. The system design has some unique features that potentially simplify installation into an existing infrared beamline. We describe the system and its features along with some performance results. 相似文献