全文获取类型
收费全文 | 3055篇 |
免费 | 898篇 |
国内免费 | 224篇 |
专业分类
化学 | 185篇 |
晶体学 | 3篇 |
力学 | 275篇 |
综合类 | 96篇 |
数学 | 2251篇 |
物理学 | 1367篇 |
出版年
2024年 | 4篇 |
2023年 | 32篇 |
2022年 | 65篇 |
2021年 | 71篇 |
2020年 | 120篇 |
2019年 | 106篇 |
2018年 | 95篇 |
2017年 | 156篇 |
2016年 | 170篇 |
2015年 | 106篇 |
2014年 | 249篇 |
2013年 | 299篇 |
2012年 | 228篇 |
2011年 | 275篇 |
2010年 | 248篇 |
2009年 | 257篇 |
2008年 | 256篇 |
2007年 | 217篇 |
2006年 | 185篇 |
2005年 | 146篇 |
2004年 | 121篇 |
2003年 | 152篇 |
2002年 | 117篇 |
2001年 | 87篇 |
2000年 | 66篇 |
1999年 | 76篇 |
1998年 | 60篇 |
1997年 | 37篇 |
1996年 | 30篇 |
1995年 | 30篇 |
1994年 | 30篇 |
1993年 | 10篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1959年 | 3篇 |
1957年 | 1篇 |
排序方式: 共有4177条查询结果,搜索用时 15 毫秒
11.
David C. Magri 《Supramolecular chemistry》2017,29(10):741-748
AbstractFrom the cross-fertilisation of fluorescent pH indicators and fluorescent redox switches, our group has established a new class of molecular sensor that operates as two-input molecular logic gates. These molecular sensors, known as ‘Pourbaix sensors’, are named in honour of Marcel Pourbaix, who developed the pH–potential diagrams for the various states of metal ion species in aqueous solution. This review highlights the evolution of ‘Pourbaix sensors’ based on anthracene and naphthalimide fluorophores. Potential applications of this class of molecule in fields such as corrosion science, cell biology and biomedical diagnostics are highlighted. 相似文献
12.
13.
In this article, we consider a portfolio optimization problem of the Merton’s type with complete memory over a finite time horizon. The problem is formulated as a stochastic control problem on a finite time horizon and the state evolves according to a process governed by a stochastic process with memory. The goal is to choose investment and consumption controls such that the total expected discounted utility is maximized. Under certain conditions, we derive the explicit solutions for the associated Hamilton–Jacobi–Bellman (HJB) equations in a finite-dimensional space for exponential, logarithmic, and power utility functions. For those utility functions, verification results are established to ensure that the solutions are equal to the value functions, and the optimal controls are also derived. 相似文献
14.
15.
刘会茹 《数学的实践与认识》2017,(12):263-268
讨论了企业投资系统的Lyapunov稳定性,得到了企业投资系统渐进稳定的充分条件和稳定的必要条件,并给出了企业投资系统的临界积累率的表达式,这个问题的研究对于促进我国经济高速、稳定持续增长具有重要的理论意义和现实指导价值. 相似文献
16.
We described the design and synthesis of a colorimetric and ratiometric fluorescent probe based on a conjugated π-electron system that displayed differential fluorescence responses towards cyanide and sulfide and demonstrated its utility in intracellular ion imaging and logic gate. 相似文献
17.
《Electrophoresis》2017,38(3-4):507-512
LIF detection often requires labeling of analytes with fluorophores; and fast fluorescent derivatization is valuable for high‐throughput analysis with flow‐gated CE. Here, we report a fast fluorescein‐labeling scheme for amino acid neurotransmitters, which were then rapidly separated and detected in flow‐gated CE. This scheme was based on the reaction between primary amines and o‐phthalaldehyde in the presence of a fluorescent thiol, 2‐((5‐fluoresceinyl)aminocarbonyl)ethyl mercaptan (FACE‐SH). The short reaction time (<30 s) was suited for on‐line mixing and derivatization that was directly coupled with flow‐gated CE for rapid electrophoretic separation and sensitive LIF detection. To maintain the effective concentration of reactive FACE‐SH, Tris(2‐carboxyethyl)phosphine was added to the derivatization reagents to prevent thiol loss due to oxidation. This labeling scheme was applied to the detection of neurotransmitters by coupling in vitro microdialysis with online derivatization and flow‐gated CE. It is also anticipated that this fluorophore tagging scheme would be valuable for on‐chip labeling of proteins retained on support in SPE. 相似文献
18.
复杂网络广泛存在于日常生活,首先,给出几类标准的网络模型;然后,利用稳定性控制方法设计并实现了具有时滞与非时滞耦合的复杂网络模型快速控制;最后,通过构造优化Lyapunov函数,讨论其模型的射影同步问题,得到了系统全局稳定的条件和有效的控制器,以实例数值验证其方法的可行性。 相似文献
19.
This paper is concerned with a nonlinear Timoshenko system with a time delay term in the internal feedback together with initial data and Dirichet boundary conditions. Under some suitable assumptions on the weights of feedback, we obtain the existence of a global attractor with finite fractal dimension for the case of equal speed wave propagation. Furthermore, the existence of exponential attractors is also derived. 相似文献
20.
In this paper, we consider a vibrating system of Timoshenko-type in a bounded one-dimensional domain under Dirichlet–Dirichlet or Dirichlet–Neumann boundary conditions with one or two discrete time delays and one or two internal frictional dampings. First, we show that the system is well posed in the sens of semigroup theory. Second, we prove the exponential stability regardless to the speeds of wave propagation of the system if the weights of the time delays are smaller than the ones of the corresponding dampings, respectively. However, when the weight of one time delay is not smaller than the one of the corresponding damping, we prove the exponential stability in case of equal-speed wave propagation, and the polynomial stability in the opposite case. 相似文献