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   4525篇
  免费   722篇
  国内免费   419篇
化学   3163篇
晶体学   42篇
力学   273篇
综合类   46篇
数学   449篇
物理学   1693篇
  2024年   14篇
  2023年   125篇
  2022年   173篇
  2021年   189篇
  2020年   215篇
  2019年   163篇
  2018年   145篇
  2017年   127篇
  2016年   208篇
  2015年   182篇
  2014年   256篇
  2013年   282篇
  2012年   395篇
  2011年   361篇
  2010年   266篇
  2009年   265篇
  2008年   285篇
  2007年   274篇
  2006年   270篇
  2005年   182篇
  2004年   126篇
  2003年   110篇
  2002年   99篇
  2001年   86篇
  2000年   87篇
  1999年   100篇
  1998年   91篇
  1997年   89篇
  1996年   65篇
  1995年   90篇
  1994年   74篇
  1993年   45篇
  1992年   61篇
  1991年   45篇
  1990年   40篇
  1989年   26篇
  1988年   16篇
  1987年   14篇
  1986年   8篇
  1985年   8篇
  1984年   4篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
排序方式: 共有5666条查询结果,搜索用时 15 毫秒
91.
2002年12月31日建成通车的上海磁悬浮列车是世界上第一条投入商业化磁浮示范运营线.从浦东的龙阳路到浦东机场,8分钟就滑过30km的距离,最高时速可达430km/h.  相似文献   
92.
This paper demonstrates and analyses double heteroclinic tangency in a three-well potential model, which can produce three new types of bifurcations of basin boundaries including from smooth to Wada basin boundaries, from fractal to Wada basin boundaries in which no changes of accessible periodic orbits happen, and from Wada to Wada basin boundaries. In a model of mechanical oscillator, it shows that a Wada basin boundary can be smooth.  相似文献   
93.
In this paper a controller of pulse coupling feedback (PCF) is designed to control chaotic systems. Control principles and the technique to select the feedback coefficients are introduced. This controller is theoretically studied with a three dimensional (3D) chaotic system. The artificial simulation results show that the chaotic system can be stabilized to different periodic orbits by using the PCF method, and the number of the periodic orbits are 2n× 3mp (n and m are integers). Therefore, this control method is effective and practical.  相似文献   
94.
We propose a scheme for generating a two-atom entangled state and an N-atom W state using adiabatic evolution of dark eigenstates in cavity QED. The time required to complete the process does not need precise control. Since the cavity modes are never excited during the operations by engineering adiabatic evolution and controlling the atom–cavity couplings, the decoherence of the cavity decay can be suppressed.  相似文献   
95.
96.
Mao  Jin-Jin  Tian  Shou-Fu  Zou  Li  Zhang  Tian-Tian  Yan  Xing-Jie 《Nonlinear dynamics》2019,95(4):3005-3017
Nonlinear Dynamics - We consider the simplified (3+1)-dimensional B-type Kadomtsev–Petviashvili equation. We use the binary Bell polynomial theory to construct a bilinear form of the...  相似文献   
97.
A series of porphyrin‐containing polyimide (PI) photocatalysts were synthesized by a one‐step solvothermal method. Characterization results revealed that porphyrin was uniformly coupled into the PI framework through covalent bonding and the visible‐light absorption was greatly improved. The photodegradation activity of porphyrin‐containing PIs for methyl orange (MO) under visible light was enhanced significantly, with the highest pseudo‐first‐order rate constant 35 times higher than that of neat porphyrin and 10 times higher than that of porphyrin‐free PI. The enhancement is mainly attributed to an increased light harvesting accompanied by a varied HOMO level, which was clarified by control experiments, characterizations and theoretical calculations. This work provides an insight into multiple effects of dye molecules in dye‐containing heterogeneous photocatalysts.  相似文献   
98.
Although cocrystallization has provided a promising platform to develop new organic optoelectronic materials, it is still a big challenge to purposely design and achieve specific optoelectronic properties. Herein, a series of mixed-stacking cocrystals (TMFA, TMCA, and TMTQ) were designed and synthesized, and the regulatory effects of the acceptors on the co-assembly behavior, charge-transfer nature, energy-level structures, and optoelectronic characteristics were systematically investigated. The results demonstrate that it is feasible to achieve effective charge-transport tuning and photoresponse switching by carefully regulating the intermolecular charge transfer and energy orbitals. The inherent mechanisms underlying the change in these optoelectronic behaviors were analyzed in depth and elucidated to provide clear guidelines for future development of new optoelectronic materials. In addition, due to the excellent photoresponsive characteristics of TMCA, TMCA-based phototransistors were investigated with varying light wavelength and optical power, and TMCA shows the best performance among all reported cocrystals under UV illumination.  相似文献   
99.
Wang  Yang  Zou  Xingfu 《Journal of Nonlinear Science》2020,30(4):1579-1605
Journal of Nonlinear Science - Predator–prey interactions are among the most complicated interactions between biological species, in which there may be both direct effect (through predation)...  相似文献   
100.
Asymmetric Michael addition between 3-ethyl carboxylate substituted pyrazolones and 5-alkenylthiazolones catalyzed by a series of chiral bifunctional hydrogen bonding organocatalysts was investigated. Good yields (up to 96%) and excellent enantioselectivities (up to 99% ee) were achieved by using a squaramide containing piperidine group derived from (1S, 2S)-cyclohexanediamine. This strategy provides facile access to a diverse library of thiazole-pyrazolone derivatives with potential bioactivity.  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