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   585859篇
  免费   7073篇
  国内免费   1882篇
化学   306803篇
晶体学   8841篇
力学   26262篇
综合类   14篇
数学   71599篇
物理学   181295篇
  2021年   4490篇
  2020年   4960篇
  2019年   5405篇
  2018年   6813篇
  2017年   6930篇
  2016年   10524篇
  2015年   6806篇
  2014年   10546篇
  2013年   27345篇
  2012年   20808篇
  2011年   25365篇
  2010年   17520篇
  2009年   17330篇
  2008年   22919篇
  2007年   23181篇
  2006年   21758篇
  2005年   19258篇
  2004年   17784篇
  2003年   15738篇
  2002年   15582篇
  2001年   17692篇
  2000年   13454篇
  1999年   10718篇
  1998年   8849篇
  1997年   8606篇
  1996年   8382篇
  1995年   7464篇
  1994年   7203篇
  1993年   6998篇
  1992年   7724篇
  1991年   7820篇
  1990年   7421篇
  1989年   7222篇
  1988年   7239篇
  1987年   7068篇
  1986年   6779篇
  1985年   9190篇
  1984年   9321篇
  1983年   7658篇
  1982年   8064篇
  1981年   7852篇
  1980年   7607篇
  1979年   7949篇
  1978年   8038篇
  1977年   7953篇
  1976年   7929篇
  1975年   7653篇
  1974年   7400篇
  1973年   7619篇
  1972年   4934篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Theoretical and Mathematical Physics - This paper is devoted to tetrahedron maps, which are set-theoretical solutions of the Zamolodchikov tetrahedron equation. We construct a family of tetrahedron...  相似文献   
52.
The health monitoring has been studied to ensure integrity of design of engine structure by detection, quantification, and prediction of damages. Early detection of faults may allow the downtime of maintenance to be rescheduled, thus preventing sudden shutdown of machines. In cylinder pressure developed, vibrations and noise emissions data provide a rich source of information about condition of engines. Monitoring of vibrations and noise emissions are novel non-intrusive methodologies for which positioning of various transducers are important issue. The presented work shows applicability of these diagnosis methodologies adopted in case of diesel engines. The effects of changing various fuel injection parameters was analyzed. Scope of using non-intrusive technique has been analyzed by changing locations of microphone. Novelty of this worklies in exploring signal processing methods for various locations around the engine test set up. Various frequency ranges of contributing noise and vibration sources were identified. Time-Frequency analysis showed the onset of various cyclic. Based on the identification of various frequency bands, it is possible to device suitable filters in order to extract more information.  相似文献   
53.
Crystallography Reports - Two LiInSe2 single crystals, grown under different conditions, have been studied. Characteristics of these crystals for neutron detection have been compared using...  相似文献   
54.
55.
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   
56.
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   
57.
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   
58.
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   
59.
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   
60.
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