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   609035篇
  免费   8645篇
  国内免费   1746篇
化学   335460篇
晶体学   7704篇
力学   25835篇
综合类   17篇
数学   71834篇
物理学   178576篇
  2021年   4796篇
  2020年   5439篇
  2019年   5809篇
  2018年   7453篇
  2017年   7136篇
  2016年   11509篇
  2015年   7823篇
  2014年   11182篇
  2013年   27968篇
  2012年   21719篇
  2011年   26294篇
  2010年   18010篇
  2009年   17531篇
  2008年   23822篇
  2007年   23838篇
  2006年   22070篇
  2005年   19970篇
  2004年   18403篇
  2003年   16171篇
  2002年   15705篇
  2001年   17442篇
  2000年   13329篇
  1999年   10510篇
  1998年   8675篇
  1997年   8385篇
  1996年   8381篇
  1995年   7398篇
  1994年   7337篇
  1993年   7111篇
  1992年   8046篇
  1991年   7955篇
  1990年   7707篇
  1989年   7512篇
  1988年   7465篇
  1987年   7188篇
  1986年   6765篇
  1985年   8996篇
  1984年   9194篇
  1983年   7356篇
  1982年   7718篇
  1981年   7628篇
  1980年   7085篇
  1979年   7626篇
  1978年   7995篇
  1977年   7759篇
  1976年   7684篇
  1975年   7186篇
  1974年   7118篇
  1973年   7180篇
  1972年   4963篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
41.
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   
42.
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   
43.
Pentafluorosulfanyl (SF5)-containing compounds and corresponding analogs are a highly valuable class of fluorine-containing building blocks owing to their unique properties. The reason for that is the set of peculiar and tremendously beneficial characteristics they can impart on molecules once introduced onto them. Despite this, their application in distinct scientific fields remains modest, given the extremely harsh reaction conditions needed to access such compounds. The recent synthetic approaches via S−F, and C−SF5 bond formation as well as the use of SF5-containing building blocks embody a “stairway-to-heaven” loophole in the synthesis of otherwise-inaccessible chemical scaffolds only a few years ago. Herein, we report and evaluate the properties of the SF5 group and analogs, by summarizing synthetic methodologies available to access them as well as following applications in material science and medicinal chemistry since 2015.  相似文献   
44.
Doklady Mathematics - The integrability of certain classes of homogeneous dynamical systems on the tangent bundles of four-dimensional manifolds is shown. The force fields involved in the systems...  相似文献   
45.
Ferrarini  A.  Finotello  A.  Salsano  G.  Auricchio  F.  Palombo  D.  Spinella  G.  Pane  B.  Conti  M. 《Acta Mechanica Sinica》2021,37(7):1192-1192
Acta Mechanica Sinica - A Correction to this paper has been published: https://doi.org/10.1007/s10409-021-01066-2  相似文献   
46.
Physics of Atomic Nuclei - Emission of short electron bunches with high charge in RF guns is considered. The emission mechanism in the case of picosecond laser pulses and the presence of a strong...  相似文献   
47.
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   
48.
Designs, Codes and Cryptography - Given an integer $$k\ge 3$$ and a group G of odd order,  if there exists a 2-(v, k, 1)-design and if v is sufficiently large then there...  相似文献   
49.
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   
50.
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   
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