全文获取类型
收费全文 | 328篇 |
免费 | 83篇 |
国内免费 | 28篇 |
专业分类
化学 | 54篇 |
力学 | 71篇 |
综合类 | 10篇 |
数学 | 29篇 |
物理学 | 275篇 |
出版年
2022年 | 9篇 |
2021年 | 19篇 |
2020年 | 9篇 |
2019年 | 6篇 |
2018年 | 10篇 |
2017年 | 20篇 |
2016年 | 22篇 |
2015年 | 25篇 |
2014年 | 30篇 |
2013年 | 26篇 |
2012年 | 17篇 |
2011年 | 18篇 |
2010年 | 24篇 |
2009年 | 18篇 |
2008年 | 26篇 |
2007年 | 24篇 |
2006年 | 22篇 |
2005年 | 21篇 |
2004年 | 13篇 |
2003年 | 21篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有439条查询结果,搜索用时 15 毫秒
101.
The two major advantages of bispectral analysis are: resistance to noise and the ability to detect nonlinearities, like quadratic
phase coupling. The first aim was to study some of the theoretical aspects of bispectral estimation. A lot of attention was
paid to the influence of noise, the number of segments, the influence of one or several harmonic deterministic components
and aliasing. These aspects are typical of rotating machinery. An example of successful fault identification in DC electric
motors is presented. The identification proved to be capable to identify quadratically coupled mechanical system when the
power-spectra analysis failed. Further it proved to be quite resistant to noise. 相似文献
102.
103.
Human movement reveals the hall mark characteristics of complex systems: namely, many interacting subsystems, multiple interactions within and between levels of analysis, emergence of movement coordination modes, and the exhibition of varying levels of the complexity of system output that continually evolve with learning and development over the life span. Here we outline how this high or infinitely dimensional complex dynamical system can be modeled by an epigenetic landscape framework—in the sense of Waddington—that captures the key features of the adaptive qualitative and quantitative properties of coordination modes (“order parameters”), the degeneracy of movement organization and the time scales of change. The framework provides some new ways to consider old problems in motor learning and development—such as an explicit and quantitative approach to exploring the concept of motor programs and developmental pathways—and yields new results and insights into the organization of learning during practice and rest times. For instance along one dimension of the landscape most of the changes occur between practice sessions. © 2006 Wiley Periodicals, Inc. Complexity 12: 40–51, 2006 相似文献
104.
Sampreeth Thayyil Yukinori Nishigami Md. Jahirul Islam P. K. Hashim Ken'ya Furuta Kazuhiro Oiwa Jian Yu Min Yao Toshiyuki Nakagaki Nobuyuki Tamaoki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202200807
Adenosine triphosphate (ATP) is the energy source for various biochemical processes and biomolecular motors in living things. Development of ATP antagonists and their stimuli-controlled actions offer a novel approach to regulate biological processes. Herein, we developed azobenzene-based photoswitchable ATP antagonists for controlling the activity of motor proteins; cytoplasmic and axonemal dyneins. The new ATP antagonists showed reversible photoswitching of cytoplasmic dynein activity in an in vitro dynein-microtubule system due to the trans and cis photoisomerization of their azobenzene segment. Importantly, our ATP antagonists reversibly regulated the axonemal dynein motor activity for the force generation in a demembranated model of Chlamydomonas reinhardtii. We found that the trans and cis isomers of ATP antagonists significantly differ in their affinity to the ATP binding site. 相似文献
105.
Dr. Hao Wang Dr. Hari Krishna Bisoyi Xinfang Zhang Dr. Fathy Hassan Prof. Quan Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(18):e202103906
Inspired by human vision, a diverse range of light-driven molecular switches and motors have been developed for fundamental understanding and application in material science and biology. Recently, the design and synthesis of visible light-driven molecular switches and motors have been actively pursued. This emerging trend is partly motivated to avoid the harmful effects of ultraviolet light, which was necessary to drive the classical molecular switches and motors at least in one direction, impeding their employment in biomedical and photopharmacology applications. Moreover, visible light-driven molecular switches and motors are demonstrated to enable benign optical materials for advanced photonic devices. Therefore, during the past several years, visible light-driven molecular switches based on azobenzene derivatives, diarylethenes, 1,2-dicyanodithienylethenes, hemithioindigo derivatives, iminothioindoxyls, donor-acceptor Stenhouse adducts, and overcrowded alkene based molecular motors have been judiciously designed, synthesized, and used in the development of functional materials and systems for a wide range of applications. In this Review, we present the recent developments toward the design of visible light-driven molecular switches and motors, with their applications in the fabrication of functional materials and systems in material science, bioscience, pharmacology, etc. The visible light-driven molecular switches and motors realized so far undoubtedly widen the scope of these interesting compounds for technological and biological applications. We hope this Review article could provide additional impetus and inspire further research interests for future exploration of visible light-driven advanced materials, systems, and devices. 相似文献
106.
Stephen A. Wallace D. L. Weeks P. Foo 《Nonlinear dynamics, psychology, and life sciences》2000,4(4):311-338
A case study was conducted on an experienced upper extremity prosthetic user that required him to perform a reaching and grasping task with both his prosthetic and normal anatomical hand. We used a scanning task (Wallace, Stevenson, Spear, & Weeks, 1994; Button, Bennett, & Davids, 1998) that required the participant to perform a wide range of coordination patterns defined by the relative phasing between the aperture of the fingers (or artificial prehensor) and the arm. Visual templates of the required finger trajectories in the various required phase conditions served as environmental information for the subject to follow. Based on previous work, we hypothesized that the participant would exhibit at least one stable reaching and grasping pattern in both his anatomical and prosthetic arm. In support of this hypothesis, the results showed a negative sloping relationship between the required relative phase and the mean delta relative phase (required relative phase minus the actual relative phase). The smallest delta relative phase occurred at approximately 80° and 115° relative phase for the anatomical and prosthetic arm, respectively during the scanning task. These results confirm our previous work of the presence of only one attractor in reaching and grasping movements using either the anatomical or prosthetic arm. 相似文献
107.
Backstepping-based lag synchronization of a complex permanent magnet synchronous motor system 下载免费PDF全文
Through introducing the concept of complex current and resetting cross-coupling term, this paper proposes a novel complex permanent magnet synchronous motor system and analyzes its properties. Based on a complex permanent magnet synchronous motor system, we design controllers and achieve lag synchronizations both in real part and imaginary part with backstepping method. In our study, we take complex current, time delay, and structure of complex system into consideration. Numerical simulation results demonstrate the validity of controllers. 相似文献
108.
The main objective of this study is to utilize two dynamic models: a mathematical model and a simple model, to identify a pick-and-place mechanism (PPM) which is driven by a permanent magnet synchronous motor (PMSM). In this paper, Hamilton’s principle is employed to derive the mathematical model, which is a nonlinear differential equation, while Newton’s second law is utilized to derive the simple linear model. In system identification, we adopt the real-coded genetic algorithm (RGA) to find not only the parameters of the PPM, but also the PMSM simultaneously. From the identification simulations and experimental results, it is demonstrated that the identification results of the mathematical model present the better matching with the experimental results of the system. 相似文献
109.
110.