全文获取类型
收费全文 | 8159篇 |
免费 | 535篇 |
国内免费 | 748篇 |
专业分类
化学 | 150篇 |
力学 | 361篇 |
综合类 | 116篇 |
数学 | 7788篇 |
物理学 | 1027篇 |
出版年
2024年 | 12篇 |
2023年 | 92篇 |
2022年 | 107篇 |
2021年 | 108篇 |
2020年 | 185篇 |
2019年 | 206篇 |
2018年 | 183篇 |
2017年 | 220篇 |
2016年 | 205篇 |
2015年 | 184篇 |
2014年 | 373篇 |
2013年 | 642篇 |
2012年 | 302篇 |
2011年 | 428篇 |
2010年 | 389篇 |
2009年 | 483篇 |
2008年 | 590篇 |
2007年 | 587篇 |
2006年 | 497篇 |
2005年 | 493篇 |
2004年 | 372篇 |
2003年 | 391篇 |
2002年 | 308篇 |
2001年 | 278篇 |
2000年 | 244篇 |
1999年 | 234篇 |
1998年 | 225篇 |
1997年 | 213篇 |
1996年 | 143篇 |
1995年 | 91篇 |
1994年 | 73篇 |
1993年 | 61篇 |
1992年 | 55篇 |
1991年 | 56篇 |
1990年 | 32篇 |
1989年 | 30篇 |
1988年 | 33篇 |
1987年 | 20篇 |
1986年 | 26篇 |
1985年 | 41篇 |
1984年 | 30篇 |
1983年 | 21篇 |
1982年 | 26篇 |
1981年 | 31篇 |
1980年 | 19篇 |
1979年 | 26篇 |
1978年 | 24篇 |
1977年 | 17篇 |
1976年 | 16篇 |
1973年 | 6篇 |
排序方式: 共有9442条查询结果,搜索用时 15 毫秒
21.
We describe the extension of the multiplication on a not-necessarily-discrete topological monoid to its flow compactification. We offer two applications. The first is a nondiscrete version of Hindman's Theorem, and the second is a characterization of the projective minimal and elementary flows in terms of idempotents of the flow compactification of the monoid. 相似文献
22.
§ 1 IntroductionRecently,certain three-point boundary value problems for nonlinear ordinarydifferential equations have been studied by many authors[1— 6] .However,few papers havebeen published on the same problems for nonlinear functional differential equations.In thispaper,we are concerned with the following second order differential equation with anadvanced argumentu″(t) +λa(t) f(u(h(t) ) ) =0 ,t∈ (0 ,1 ) (1 .1 )with the three-point boundary conditionsu(0 ) =0 ,αu(η) =u(1 ) ,(1 .2 )… 相似文献
23.
具有功能反应的两斑块扩散时滞竞争系统正周期解的存在性 总被引:6,自引:0,他引:6
§ 1 IntroductionFormanyspeciesthespatialfactorsareimportantinpopulationdynamics .Thetheoreticalstudyofspatialdistributionhasbeenextensivelystudiedinmanypapers .Mostofthepreviouspapersfocusedonthecoexistenceofpopulationsmodelledbyststemsofordinarydiffere… 相似文献
24.
XinPingWANG 《数学学报(英文版)》2003,19(4):765-782
In this paper,we are concerned with the boundedness of all the solutions of the equation x″ ax^ -bx- Ф(x)=p(t),where p(t) is a smooth 2π-periodic function,a and b are positive constants,and the perturbation Ф(x) is bounded. 相似文献
25.
26.
27.
FAN Hong-Yi JIANG Zhong-Hua 《理论物理通讯》2005,44(12)
We show how to directly use the generalized Feynman-Hellmann theorem, which is suitable for mixed state ensemble average, to derive the internal energy of Hamiltonian systems. A concrete example, which is a two coupled harminic oscillators, is used for elucidating our approach. 相似文献
28.
切变模量和转动惯量实验的改进 总被引:1,自引:1,他引:1
设计了一种基于垂直轴定理的新型吊钩,对切变模量和转动惯量实验进行了改进,使之成为既可测定金属丝切变模量和环、柱等刚体的转动惯量,又可验证反映转动惯量重要性质的平行轴定理及垂直轴定理的多功能实验仪. 相似文献
29.
C. I. J. M. Stuart 《Foundations of Physics Letters》1991,4(5):479-492
Aprediction puzzle leads to a form ofnecessary realism which forces the rejection of a central tenet of the Copenhagen interpretation. This leads to reconsidering conceptual difficulties related to Bell's locality premise. It is shown that aparadox of elementary probability theory puts new light on Bell's assumption that causality and statistical independence are mutually incompatible.
Nemo dat quod non habet : No one can offer more than he has ability to give; in that spirit, this paper is dedicated to the memory of J.S. Bell. 相似文献
30.
Ichiro Tsuda Hiroshi Watanabe Hiromichi Tsukada Yutaka Yamaguti 《Entropy (Basel, Switzerland)》2022,24(2)
The focus of this article is the self-organization of neural systems under constraints. In 2016, we proposed a theory for self-organization with constraints to clarify the neural mechanism of functional differentiation. As a typical application of the theory, we developed evolutionary reservoir computers that exhibit functional differentiation of neurons. Regarding the self-organized structure of neural systems, Warren McCulloch described the neural networks of the brain as being “heterarchical”, rather than hierarchical, in structure. Unlike the fixed boundary conditions in conventional self-organization theory, where stationary phenomena are the target for study, the neural networks of the brain change their functional structure via synaptic learning and neural differentiation to exhibit specific functions, thereby adapting to nonstationary environmental changes. Thus, the neural network structure is altered dynamically among possible network structures. We refer to such changes as a dynamic heterarchy. Through the dynamic changes of the network structure under constraints, such as physical, chemical, and informational factors, which act on the whole system, neural systems realize functional differentiation or functional parcellation. Based on the computation results of our model for functional differentiation, we propose hypotheses on the neuronal mechanism of functional differentiation. Finally, using the Kolmogorov–Arnold–Sprecher superposition theorem, which can be realized by a layered deep neural network, we propose a possible scenario of functional (including cell) differentiation. 相似文献