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   406275篇
  免费   6305篇
  国内免费   3971篇
化学   209258篇
晶体学   6617篇
力学   19131篇
综合类   210篇
数学   54453篇
物理学   126882篇
  2018年   11363篇
  2017年   12308篇
  2016年   8262篇
  2015年   4338篇
  2014年   4754篇
  2013年   13313篇
  2012年   13901篇
  2011年   24203篇
  2010年   15135篇
  2009年   14867篇
  2008年   21005篇
  2007年   24457篇
  2006年   10208篇
  2005年   16391篇
  2004年   11778篇
  2003年   10633篇
  2002年   8559篇
  2001年   8911篇
  2000年   6951篇
  1999年   5483篇
  1998年   4402篇
  1997年   4390篇
  1996年   4371篇
  1995年   4120篇
  1994年   3774篇
  1993年   3614篇
  1992年   4280篇
  1991年   4098篇
  1990年   3949篇
  1989年   3990篇
  1988年   3974篇
  1987年   3974篇
  1986年   3708篇
  1985年   5010篇
  1984年   5113篇
  1983年   4267篇
  1982年   4670篇
  1981年   4475篇
  1980年   4435篇
  1979年   4580篇
  1978年   4909篇
  1977年   4596篇
  1976年   4617篇
  1975年   4361篇
  1974年   4236篇
  1973年   4459篇
  1972年   2811篇
  1968年   2855篇
  1967年   3039篇
  1966年   2629篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Kobayashi  M.  Zhang  Y.  Ishikawa  H.  Sun  J.  Oddershede  J.  Juul Jensen  D.  Miura  H. 《Experimental Mechanics》2021,61(5):817-828
Experimental Mechanics - The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such...  相似文献   
12.
Mejjaoli  H.  Ben Saïd  S. 《Analysis Mathematica》2021,47(3):629-663
Analysis Mathematica - We introduce and study the k-Hankel Gabor transform. We investigate the localization operators for this transform. In particular, we study their trace class properties and we...  相似文献   
13.
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   
14.
Chen  C. Y.  Kao  C. L.  Huang  S. T.  Kuo  C. E.  Song  P. L.  Li  W. J.  Hsu  L. T.  Li  H. T. 《Chemistry of Natural Compounds》2022,58(1):107-109
Chemistry of Natural Compounds -  相似文献   
15.
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   
16.
Herein, we report a Mott-Schottky catalyst by entrapping cobalt nanoparticles inside the N-doped graphene shell (Co@NC). The Co@NC delivered excellent oxygen evolution activity with an overpotential of merely 248 mV at a current density of 10 mA cm–2 with promising long-term stability. The importance of Co encapsulated in NC has further been demonstrated by synthesizing Co nanoparticles without NC shell. The synergy between the hexagonal close-packed (hcp) and face-centered cubic (fcc) Co plays a major role to improve the OER activity, whereas the NC shell optimizes the electronic structure, improves the electron conductivity, and offers a large number of active sites in Co@NC. The density functional theory calculations have revealed that the hcp Co has a dominant role in the surface reaction of electrocatalytic oxygen evolution, whereas the fcc phase induces the built-in electric field at the interfaces with N-doped graphene to accelerate the H+ ion transport.  相似文献   
17.
Journal of Radioanalytical and Nuclear Chemistry - In this paper a study for the selection of an NPE (nonylphenol ethoxylates)—free cocktail is discussed in order to be used for our routine...  相似文献   
18.
Chen  R. J.  Chen  W.  Kong  F. L. 《Analysis Mathematica》2022,48(1):19-28

Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.

  相似文献   
19.
20.
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