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   131908篇
  免费   1717篇
  国内免费   927篇
化学   48954篇
晶体学   2038篇
力学   8868篇
综合类   50篇
数学   28040篇
物理学   46602篇
  2023年   212篇
  2022年   400篇
  2021年   412篇
  2020年   415篇
  2019年   420篇
  2018年   10115篇
  2017年   11043篇
  2016年   5075篇
  2015年   1563篇
  2014年   943篇
  2013年   1482篇
  2012年   6325篇
  2011年   15461篇
  2010年   9183篇
  2009年   9261篇
  2008年   13079篇
  2007年   16830篇
  2006年   1625篇
  2005年   8687篇
  2004年   4829篇
  2003年   4541篇
  2002年   2315篇
  2001年   1279篇
  2000年   1087篇
  1999年   700篇
  1998年   524篇
  1997年   510篇
  1996年   603篇
  1995年   435篇
  1994年   419篇
  1993年   335篇
  1992年   305篇
  1991年   288篇
  1990年   282篇
  1989年   248篇
  1988年   223篇
  1987年   201篇
  1986年   186篇
  1985年   201篇
  1984年   193篇
  1983年   156篇
  1982年   136篇
  1981年   139篇
  1980年   129篇
  1979年   142篇
  1978年   163篇
  1976年   111篇
  1975年   91篇
  1973年   124篇
  1968年   113篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications.  相似文献   
2.
Li  Y.  Shi  W. H.  Dong  L. M.  Xu  S. X.  Huang  H. J.  Yin  J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,...  相似文献   
3.
Du  Zhong  Xu  Tao  Ren  Shuai 《Nonlinear dynamics》2021,104(1):683-689
Nonlinear Dynamics - In this paper, we investigate the interactions of the vector breathers for the coupled Hirota system with $$4\times 4$$ Lax pair. Firstly, we give the first-order breather...  相似文献   
4.
5.
6.
7.
8.
9.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation.  相似文献   
10.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  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