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   32267篇
  免费   6101篇
  国内免费   3664篇
化学   23266篇
晶体学   373篇
力学   1963篇
综合类   198篇
数学   3258篇
物理学   12974篇
  2024年   53篇
  2023年   723篇
  2022年   834篇
  2021年   1184篇
  2020年   1503篇
  2019年   1484篇
  2018年   1233篇
  2017年   1133篇
  2016年   1692篇
  2015年   1617篇
  2014年   2051篇
  2013年   2536篇
  2012年   3082篇
  2011年   3118篇
  2010年   2068篇
  2009年   1996篇
  2008年   2195篇
  2007年   1920篇
  2006年   1772篇
  2005年   1410篇
  2004年   1044篇
  2003年   807篇
  2002年   772篇
  2001年   616篇
  2000年   504篇
  1999年   615篇
  1998年   535篇
  1997年   514篇
  1996年   500篇
  1995年   445篇
  1994年   360篇
  1993年   292篇
  1992年   291篇
  1991年   238篇
  1990年   220篇
  1989年   159篇
  1988年   93篇
  1987年   80篇
  1986年   105篇
  1985年   81篇
  1984年   38篇
  1983年   49篇
  1982年   27篇
  1981年   22篇
  1980年   7篇
  1979年   5篇
  1975年   1篇
  1973年   1篇
  1957年   5篇
  1923年   1篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
31.
32.
Theoretical and Mathematical Physics - By introducing shift relations satisfied by a matrix $$\boldsymbol{r}$$ , we propose a generalized Cauchy matrix scheme and construct a discrete second-order...  相似文献   
33.
大学化学实验课程是培养材料、化学、化工等专业人才应用基本操作和理论解决实际问题的综合性实践训练环节。文章探讨了当前大学化学实验发展由于受到仪器设备大型化、专业化、成本大、更新快等因素限制出现瓶颈,设计了线上线下混合实验教学模式,进行相应的软硬件建设,并开展线上线下混合式实验教学模式的改革与探索。该教学模式具有良好的教学效果,并且可复制可推广,为创新人才的培养和实验教学的创新提供了有益的借鉴。  相似文献   
34.
Asymmetric mode transformation in waveguide is of great significance for on-chip integrated devices with one-way effect, while it is challenging to achieve asymmetric nonlinear-mode-conversion (NMC) due to the limitations imposed by phase-matching. In this work, we theoretically proposed a new scheme for realizing asymmetric NMC by combining frequency-doubling process and periodic PT symmetric modulation in an optical waveguide. By engineering the one-way momentum from PT symmetric modulation, we have demonstrated the unidirectional conversion from pump to second harmonic with desired guided modes. Our findings offer new opportunities for manipulating nonlinear optical fields with PT symmetry, which could further boost more exploration on on-chip nonlinear devices assisted by non-Hermitian optics.  相似文献   
35.
Along with the rapid development of industry, VOCs gradually move into the spotlight, and now become a kind of harmful environmental pollutants that cannot be overlooked. This paper introduces the hazards of VOCs and the common catalytic combustion catalysts, noble metal catalysts and non-noble metal catalysts, for the elimination of VOCs. Perovskite catalysts, as one of the non-noble catalysts, play an important role in the field of catalytic combustion in recent years. According to the classification of elements doping in perovskites, the research achievements in the past five years were analyzed and reviewed. In addition, this paper also analyzes and elaborates the reaction kinetics and QSAR/QSPR models for the introduction of structural properties and reaction mechanisms.  相似文献   
36.
The ability to optically reconfigure an existing actuator of a liquid crystal polymer network (LCN) so that it can display a new actuation behavior or function is highly desired in developing materials for soft robotics applications. Demonstrated here is a powerful approach relying on selective polymer chain decrosslinking in a LCN actuator with uniaxial LC alignment. Using an anthracene‐containing LCN, spatially controlled optical decrosslinking can be realized through photocleavage of anthracene dimers under 254 nm UV light, which alters the distribution of actuation (crosslinked) and non‐actuation (decrosslinked) domains and thus determines the actuation behavior upon order‐disorder phase transitions. Based on this mechanism, a single actuator having a flat shape can be reconfigured in an on‐demand manner to exhibit reversible shape transformation such as self‐folding into origami three‐dimensional structures. Moreover, using a dye‐doped LCN actuator, a light‐fueled microwalker can be optically reconfigured to adopt different locomotion behaviors, changing from moving in the laser scanning direction to moving in the opposite direction.  相似文献   
37.
Two‐dimensional (2D) PtSe2 shows the most prominent layer‐dependent electrical properties among various 2D materials and high catalytic activity for hydrogen evolution reaction (HER), and therefore, it is an ideal material for exploring the structure–activity correlations in 2D systems. Here, starting with the synthesis of single‐crystalline 2D PtSe2 with a controlled number of layers and probing the HER catalytic activity of individual flakes in micro electrochemical cells, we investigated the layer‐dependent HER catalytic activity of 2D PtSe2 from both theoretical and experimental perspectives. We clearly demonstrated how the number of layers affects the number of active sites, the electronic structures, and electrical properties of 2D PtSe2 flakes and thus alters their catalytic performance for HER. Our results also highlight the importance of efficient electron transfer in achieving optimum activity for ultrathin electrocatalysts. Our studies greatly enrich our understanding of the structure–activity correlations for 2D catalysts and provide new insight for the design and synthesis of ultrathin catalysts with high activity.  相似文献   
38.
39.
40.
Liu  Yang  Zhao  Yulai  Li  Jintao  Lu  Huanhuan  Ma  Hui 《Nonlinear dynamics》2020,99(2):1763-1777
Nonlinear Dynamics - Fault features extraction method for slight misalignment of rotor systems is researched in this paper. When a rotor system with faults is excited by harmonic inputs, system...  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