首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   148915篇
  免费   29212篇
  国内免费   14357篇
化学   115046篇
晶体学   1637篇
力学   8630篇
综合类   884篇
数学   16422篇
物理学   49865篇
  2024年   114篇
  2023年   2365篇
  2022年   2598篇
  2021年   3987篇
  2020年   5870篇
  2019年   6781篇
  2018年   4846篇
  2017年   4391篇
  2016年   8665篇
  2015年   8610篇
  2014年   9790篇
  2013年   12402篇
  2012年   13380篇
  2011年   13427篇
  2010年   10278篇
  2009年   10046篇
  2008年   10066篇
  2007年   8786篇
  2006年   7995篇
  2005年   7096篇
  2004年   5537篇
  2003年   4490篇
  2002年   4419篇
  2001年   3106篇
  2000年   2534篇
  1999年   2444篇
  1998年   2199篇
  1997年   2034篇
  1996年   2143篇
  1995年   1818篇
  1994年   1733篇
  1993年   1374篇
  1992年   1209篇
  1991年   1179篇
  1990年   923篇
  1989年   686篇
  1988年   576篇
  1987年   465篇
  1986年   429篇
  1985年   362篇
  1984年   277篇
  1983年   188篇
  1982年   172篇
  1981年   125篇
  1980年   91篇
  1979年   50篇
  1978年   35篇
  1976年   43篇
  1975年   41篇
  1974年   47篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Two-dimensional van der Waals magnetic materials are intriguing for applications in the future spintronics devices, so it is crucial to explore strategy to control the magnetic properties. Here, we carried out first-principles calculations and Monte Carlo simulations to investigate the effect of biaxial strain and hydrostatic pressure on the magnetic properties of the bilayer CrI3. We found that the magnetic anisotropy, intralayer and interlayer exchange interactions, and Curie temperature can be tuned by biaxial strain and hydrostatic pressure. Large compressive biaxial strain may induce a ferromagneticto-antiferromagnetic transition of both CrI3 layers. The hydrostatic pressure could enhance the intralayer exchange interaction significantly and hence largely boost the Curie temperature. The effect of the biaxial strain and hydrostatic pressure revealed in the bilayer CrI3 may be generalized to other two-dimensional magnetic materials.  相似文献   
102.
Liu  Cungen  Gao  Chuang  Liu  Xiaoping  Wang  Huanqing  Zhou  Yucheng 《Nonlinear dynamics》2021,104(4):3655-3670
Nonlinear Dynamics - This paper is devoted to the adaptive finite-time prescribed performance control (FTPPC) for stochastic nonlinear systems with unknown virtual control coefficients (UVCCs),...  相似文献   
103.
Zhang  F.  Yi  S. H.  Niu  H. B.  Lu  X. G.  Wang  X. X. 《Fluid Dynamics》2021,56(3):383-392
Fluid Dynamics - To predict the boundary layer transition on swept wings, experimental and numerical researches were conducted to obtained the accurate boundary layer transition front and to...  相似文献   
104.
Molecular Diversity - According to the fact that 5-nitro-3-trinitromethyl-1H-1,2,4 triazole (NTNMT) is a successful, good explosive, energetic groups such as –CH3, –NH2, –NHNO2,...  相似文献   
105.
Wang  Zhenya  Chen  Hui  Yao  Ligang  Chen  Xu  Qi  Xiaoli  Zhang  Jun 《Nonlinear dynamics》2021,106(3):2107-2130
Nonlinear Dynamics - Fault diagnosis of critical rotating machinery components is necessary to ensure safe operation. However, the commonly used rotating machinery fault diagnosis methods are...  相似文献   
106.
Ding  Hao  Wang  Jin-Ting  Lu  Li-Qiao  Pan  Jian-Wen 《Nonlinear dynamics》2021,104(4):3365-3384
Nonlinear Dynamics - Conventional tuned liquid column dampers (TLCDs) are deficient in multidirectionality. In contrast, toroidal TLCDs are designed to extend the application to multidirectional...  相似文献   
107.
International Journal of Theoretical Physics - In this paper, we will consider the exact calculation of differential entropy of induced random state ensemble by partial tracing a subsystem over...  相似文献   
108.
We propose a lumped element Josephson parametric amplifier with vacuum-gap-based capacitor.The capacitor is made of quasi-floating aluminum pad and on-chip ground.We take a fabrication process compatible with air-bridge technology,which makes our design adaptable for future on-chip integrated quantum computing system.Further engineering the input impedance,we obtain a gain above 20 dB over 162-MHz bandwidth,along with a quasi quantum-limit noise performance.This work should facilitate the development of quantum information processing and integrated superconducting circuit design.  相似文献   
109.
In this paper, the authors discuss a generalization of Lappan’s theorem to higher dimensional complex projective space and get the following result: Let f be a holomorphic mapping of ? into Pn(C), and let H1, · · · , Hq be hyperplanes in general position in Pn(C).Assume that sup {(1 ? |z|2)f?(z) : z ∈ q[ j=1 f?1(Hj )o < ∞,if q ≥ 2n2 + 3, then f is normal.  相似文献   
110.
A reasonable prediction of photofission observables plays a paramount role in understanding the photofission process and guiding various photofission-induced applications, such as short-lived isotope production, nuclear waste disposal, and nuclear safeguards. However, the available experimental data for photofission observables are limited, and the existing models and programs have mainly been developed for neutron-induced fission processes. In this study, a general framework is proposed for characterizing the photofission observables of actinides, including the mass yield distributions (MYD) and isobaric charge distributions (ICD) of fission fragments and the multiplicity and energy distributions of prompt neutrons (np) and prompt γ rays (γp). The framework encompasses various systematic neutron models and empirical models considering the Bohr hypothesis and does not rely on the experimental data as input. These models are then validated individually against experimental data at an average excitation energy below 30 MeV, which shows the reliability and robustness of the general framework. Finally, we employ this framework to predict the characteristics of photofission fragments and the emissions of prompt particles for typical actinides including 232Th, 235, 238U and 240Pu. It is found that the 238U(γ, f) reaction is more suitable for producing neutron-rich nuclei compared to the 232Th(γ, f) reaction. In addition, the average multiplicity number of both np and γp increases with the average excitation energy.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号