全文获取类型
收费全文 | 835篇 |
免费 | 51篇 |
国内免费 | 32篇 |
专业分类
化学 | 166篇 |
晶体学 | 1篇 |
力学 | 43篇 |
综合类 | 3篇 |
数学 | 75篇 |
物理学 | 180篇 |
综合类 | 450篇 |
出版年
2024年 | 4篇 |
2023年 | 13篇 |
2022年 | 13篇 |
2021年 | 16篇 |
2020年 | 21篇 |
2019年 | 25篇 |
2018年 | 15篇 |
2017年 | 33篇 |
2016年 | 24篇 |
2015年 | 35篇 |
2014年 | 39篇 |
2013年 | 46篇 |
2012年 | 35篇 |
2011年 | 45篇 |
2010年 | 35篇 |
2009年 | 58篇 |
2008年 | 52篇 |
2007年 | 62篇 |
2006年 | 74篇 |
2005年 | 43篇 |
2004年 | 52篇 |
2003年 | 36篇 |
2002年 | 25篇 |
2001年 | 25篇 |
2000年 | 23篇 |
1999年 | 15篇 |
1998年 | 17篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 6篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1984年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有918条查询结果,搜索用时 0 毫秒
801.
In this paper, we consider a new class of piecewise linear (PWL) systems with two virtual stable node-foci (the meaning of “virtual” is from Bernardo et al. (2008)) which exhibits periodic orbits and chaos. This fact that PWL systems have no unstable equilibria but has chaos will unavoidably make the exploration of this chaos more complicated. Particular values for bifurcation diagram are provided. Based on mathematical analysis and Poincaré map, periodic orbits of this kind of system without unstable equilibrium points are derived, the corresponding existence theorems are given, and the obtained results are applied to specific examples. 相似文献
802.
《Stochastic Processes and their Applications》2020,130(1):47-78
Forward–backward stochastic differential equations (FBSDEs) have attracted significant attention since they were introduced, due to their wide range of applications, from solving non-linear PDEs to pricing American-type options. Here, we consider two new classes of multidimensional FBSDEs with distributional coefficients (elements of a Sobolev space with negative order). We introduce a suitable notion of solution and show its existence and in certain cases its uniqueness. Moreover we establish a link with PDE theory via a non-linear Feynman–Kac formula. The associated semi-linear parabolic PDE is the same for both FBSDEs, also involves distributional coefficients and has not previously been investigated. 相似文献
803.
T. Cheng 《Annals of Physics》2010,325(2):265-286
We study the spectral and dynamical properties of a simplified model system of interacting fermions and bosons. The spatial discretization and an effective truncation of the Hilbert space permit us to compute the distribution of the bare fermions and bosons in the energy eigenstates of the coupled system. These states represent the physical particles and are used to examine the validity of the analytical predictions by perturbation theory and by the Greenberg-Schweber approximation that assumes all fermions are at rest. As an example of our numerical framework, we examine how a bare electron can trigger the creation of a cloud of virtual bosons around. We relate this cloud to the properties of the associated energy eigenstates. 相似文献
804.
805.
Daiyu KOBAYASHI Reiko WATANABE Mitsuru YAMAMOTO Masahiro KIZAKI 《Physical Therapy Research》2020,23(2):172
Objective: This study aimed to define the efficacy and features of physical therapy (PT) using the Nintendo Wii Fit U (Nintendo Inc., Kyoto, Japan) in patients with hematological malignancies confined to a bioclean room. Method: A total of 33 patients with hematological malignancies confined to a bioclean room were enrolled in this study. This study was designed as a randomized crossover test between two weeklong interventions: PT program (Therapist PT) and Wii Fit U program (Wii PT). We compared the efficacy of Wii PT and Therapist PT with regard to physical and psychological function test scores. Results: Of the 33 patients, 22 were analyzed. The validity of the crossover design was demonstrated, as there were no significant differences in period and carryover effects between the two groups. Therapist PT resulted in significantly better improvements in fatigue scores and total mood disturbance (TMD) scores in the Profile of Mood States short-form Japanese version compared to Wii PT (fatigue score, -5.2±8.3 vs 2.7±8.2; TMD score, -22.5±32.8 vs -2.6±20.5; p<0.05). Physical function improved post-Wii PT and post-Therapist PT interventions (p<0.05), and there was no difference in treatment effect. Conclusion: Improvements in physical function were clearly observed following the use of Wii PT in patients confined to a bioclean room. However, compared to Therapist PT, Wii PT was less effective in improving the psychological function of patients. 相似文献
806.
针对开口房间内的变压器,在开口处布放若干扬声器和误差传声器构成虚拟声屏障,实验研究了虚拟声屏障对通过开口向外辐射的低频线谱噪声的控制效果。将15个次级源近似均匀分布在面积为2 m′ 2.7 m的开口面上,左右间距约58.5 cm、上下间距45-65 cm,15个误差传声器分别位于对应的次级源正前方1 m,系统采用自适应谐波降噪算法。结果表明:虚拟声屏障系统在误差点100 Hz、200 Hz和300 Hz的平均降噪量分别达到12.7 dB、19.9 dB和22.2 dB,虚拟声屏障对100 Hz、200 Hz、300 Hz线谱噪声的控制效果与单层封闭窗户相当,且内部合成参考信号,无需外接参考传声器。采用虚拟声屏障对开口房间内的变压器降噪的好处是实现室内外的自然通风,便于变压器的散热。 相似文献
807.
本文综述了电声学科由于具有跨越科学与艺术两大领域和跨越多种学科的性质所带来的研究和应用特点,提出了几项近些年值得重视的应用领域和可能发展趋势,希望引起同仁讨论。鉴于我国在其中有些方面有突出成绩,本文将特别加以介绍,也希望得到大家的关心。本文还有一个附带的期望:促进非电声学科的声学工作者了解和关心电声学科的核心。 相似文献
808.
809.
810.
一种基于虚拟技术的新型测量材料导热系数的方法 总被引:1,自引:0,他引:1
针对稳态平板法测量材料导热系数存在的缺点,介绍了一种新的测量方法——瞬时平面热带法,并用虚拟仪器采集数据、数据处理及数据显示。 相似文献