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   614994篇
  免费   6835篇
  国内免费   1651篇
化学   294718篇
晶体学   8483篇
力学   32351篇
综合类   14篇
数学   104023篇
物理学   183891篇
  2021年   4321篇
  2020年   4784篇
  2019年   5264篇
  2018年   20781篇
  2017年   21010篇
  2016年   17781篇
  2015年   7868篇
  2014年   10406篇
  2013年   23849篇
  2012年   24512篇
  2011年   38334篇
  2010年   25067篇
  2009年   25021篇
  2008年   32237篇
  2007年   36009篇
  2006年   18757篇
  2005年   22259篇
  2004年   18527篇
  2003年   17054篇
  2002年   14760篇
  2001年   14437篇
  2000年   11161篇
  1999年   8432篇
  1998年   7127篇
  1997年   6898篇
  1996年   6708篇
  1995年   5802篇
  1994年   5738篇
  1993年   5515篇
  1992年   6110篇
  1991年   6335篇
  1990年   5910篇
  1989年   5868篇
  1988年   5582篇
  1987年   5638篇
  1986年   5291篇
  1985年   6816篇
  1984年   6964篇
  1983年   5797篇
  1982年   6048篇
  1981年   5692篇
  1980年   5557篇
  1979年   5961篇
  1978年   6088篇
  1977年   5847篇
  1976年   5943篇
  1975年   5585篇
  1974年   5600篇
  1973年   5624篇
  1972年   3854篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Svetlakova  A. V.  Mendez  M. Sanchez  Tuchin  E. S.  Khodan  A. N.  Traore  M.  Azouani  R.  Kanaev  A.  Tuchin  V. V. 《Optics and Spectroscopy》2021,129(8):846-850
Optics and Spectroscopy - We study the photocatalytic activity of nanocomposites based on θ-phase alumina (Al2O3) with different TiO2 concentrations for heterogeneous photocatalysis and...  相似文献   
62.
Russian Chemical Bulletin - The N-methylation of primary carboxamides is based on two consecutive reactions. The silylation of the corresponding carboxamides with chloro(chloromethyl)dimethylsilane...  相似文献   
63.
Journal of Structural Chemistry - Structural parameters and relative Gibbs free energies are calculated by density functional theory methods for four tetrafluoro derivatives of zinc(II)...  相似文献   
64.
Crystallography Reports - Electron backscattered diffraction (EBSD) has been used to analyze structures of natural minerals and artificial compounds for almost three decades. In recent years, it is...  相似文献   
65.
66.
Ukrainian Mathematical Journal - We establish new criteria of compatibility for a linear system of equations (equivalent to the Kronecker–Capelli theorem) or inequalities (equivalent to the...  相似文献   
67.
Foundations of Computational Mathematics - We present a finite element variational integrator for compressible flows. The numerical scheme is derived by discretizing, in a structure-preserving way,...  相似文献   
68.
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   
69.
A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample.  相似文献   
70.
Crystallography Reports - The orientation of grains and the special boundaries formed by them in multicrystalline silicon has been studied by electron backscattered diffraction. It is found that...  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