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   9750篇
  免费   1836篇
  国内免费   1092篇
化学   6938篇
晶体学   89篇
力学   588篇
综合类   57篇
数学   1106篇
物理学   3900篇
  2024年   10篇
  2023年   231篇
  2022年   230篇
  2021年   353篇
  2020年   419篇
  2019年   400篇
  2018年   386篇
  2017年   310篇
  2016年   538篇
  2015年   464篇
  2014年   579篇
  2013年   775篇
  2012年   951篇
  2011年   955篇
  2010年   648篇
  2009年   640篇
  2008年   648篇
  2007年   561篇
  2006年   521篇
  2005年   421篇
  2004年   312篇
  2003年   237篇
  2002年   189篇
  2001年   165篇
  2000年   180篇
  1999年   212篇
  1998年   165篇
  1997年   159篇
  1996年   185篇
  1995年   148篇
  1994年   122篇
  1993年   91篇
  1992年   101篇
  1991年   59篇
  1990年   74篇
  1989年   55篇
  1988年   26篇
  1987年   28篇
  1986年   39篇
  1985年   39篇
  1984年   13篇
  1983年   16篇
  1982年   6篇
  1981年   4篇
  1980年   6篇
  1979年   2篇
  1977年   1篇
  1976年   2篇
  1957年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Qiang  Chenxu  Hao  Yuxin  Zhang  Wei  Li  Jinqiang  Yang  Shaowu  Cao  Yuteng 《应用数学和力学(英文版)》2021,42(11):1555-1570
Applied Mathematics and Mechanics - The concept of local resonance phononic crystals proposed in recent years provides a new chance for theoretical and technical breakthroughs in the structural...  相似文献   
3.
International Journal of Theoretical Physics - Quantum logic gates are the foundation of circuit-based quantum computation and quantum simulation. Multi-qubit quantum controlled gates are of vital...  相似文献   
4.

In this paper, we present and analyze an energy-conserving and linearly implicit scheme for solving the nonlinear wave equations. Optimal error estimates in time and superconvergent error estimates in space are established without certain time-step restrictions. The key is to estimate directly the solution bounds in the H2-norm for both the nonlinear wave equation and the corresponding fully discrete scheme, while the previous investigations rely on the temporal-spatial error splitting approach. Numerical examples are presented to confirm energy-conserving properties, unconditional convergence and optimal error estimates, respectively, of the proposed fully discrete schemes.

  相似文献   
5.
Since most of the control strategies for air-breathing hypersonic vehicles (AHVs) concentrate on the control-oriented models built at/around a specific working point, it is somewhat hard to extend them to the broader flight envelop. Aiming at the above deficiency, this paper formulates the dynamics of AHVs as several sub-models, which switch to each other in accordance with the flight condition and make up of the control-oriented switched model (COSM). With the aid of the COSM, two adaptive tracking controllers are proposed for the purposes of velocity tracking and altitude tracking, sequentially. By utilizing neural networks and designing robust control laws, the possible changes on the force and moment coefficients in the COSM are successfully handled. The time-varying inertia parameters of AHVs are also considered at design level. It is worth emphasizing that while this strategy is developed based on a switched model, the resulting control algorithm is continuous with no connection to the switching signal. Analysis indicates that both velocity and altitude tracking errors remain small within the whole flight envelop, which is further confirmed by a simulation study.  相似文献   
6.
In this study, we investigate the modulation of energy band in 3D self-assembled nanomembranes containing GaAs/Al0.26Ga0.74As quantum wells (QWs). Photoluminescence (PL) characterizations demonstrate that the self-assembled structures have different optical transition properties and the modulation of the energy band is thus realized. Detailed spectral analyses disclose that the small strain change in structures with different curvatures cannot cause remarkable change in energy bands in Al0.26Ga0.74As layer. On the other hand, the optical transitions of GaAs QW layer is influenced by the strain evolution in term of light emission intensity. We also find the first order Stark effect in rolled-up nanomembrane with diameter of 150 μm, which is closely connected with the coupling effect between the deformation potential and the piezoelectric potential. Our work may pave a way for the fabrication of high performance rolled-QW infrared photo-detectors.  相似文献   
7.
8.
A novel 6-endo-dig cyclization followed by oxidation/elimination of o-alkynylarylaldimines with 4-hydroxybenzylamine was developed for preparation of isoquinolines. The intermediates of this tandem reaction were monitored by mass spectroscopy (MS) to confirm the reaction pathway. This methodology was further applied to the design and synthesis of a novel ratiometric chemosensor for determination of fluoride.  相似文献   
9.
Herein we summarized some clean preparation examples to emphasize the concept of dual roles design (or named as “two birds one stone strategy”) in green and sustainable chemistry. In those examples, the reactants and/or solvent play dual roles rendering a cleaner organic preparation process. Consequently, both the chemical waste and manufacturing cost could be reduced.  相似文献   
10.
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