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   377819篇
  免费   6049篇
  国内免费   1401篇
化学   205084篇
晶体学   4138篇
力学   15500篇
综合类   19篇
数学   51820篇
物理学   108708篇
  2021年   2191篇
  2020年   2606篇
  2019年   2571篇
  2018年   3972篇
  2017年   3986篇
  2016年   5883篇
  2015年   4984篇
  2014年   6124篇
  2013年   17094篇
  2012年   16210篇
  2011年   18395篇
  2010年   11527篇
  2009年   10945篇
  2008年   15403篇
  2007年   15620篇
  2006年   14976篇
  2005年   17233篇
  2004年   15294篇
  2003年   12309篇
  2002年   10392篇
  2001年   10910篇
  2000年   8378篇
  1999年   6652篇
  1998年   5321篇
  1997年   5114篇
  1996年   5235篇
  1995年   4642篇
  1994年   4351篇
  1993年   4171篇
  1992年   4751篇
  1991年   4548篇
  1990年   4235篇
  1989年   4054篇
  1988年   4285篇
  1987年   3939篇
  1986年   3793篇
  1985年   5554篇
  1984年   5622篇
  1983年   4511篇
  1982年   4933篇
  1981年   4984篇
  1980年   4690篇
  1979年   4832篇
  1978年   4841篇
  1977年   4762篇
  1976年   4822篇
  1975年   4658篇
  1974年   4545篇
  1973年   4703篇
  1972年   2658篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
1.
Journal of Fluorescence - This report describes a combined immunofluorescence and fluorescence viability stain applied as one staining solution for rapid detection of live Legionella...  相似文献   
2.
Yang  T. L.  Kao  C. L.  Kuo  C. E.  Yeh  H. C.  Li  W. J.  Li  H. T.  Chen  C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the...  相似文献   
3.
Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from FeII and FeIII precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV-visible, Mössbauer), ESI-MS and DFT studies, an FeIV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the FeII precursor was expected by a two-electron oxidative addition, its formation from an FeIII precursor was unprecedented. Thanks to a combination of spectroscopic (UV-visible, EPR, Hyscore and Mössbauer), ESI-MS and DFT studies, we found that, when starting from the FeIII precursor, an FeIII tosyliodinane adduct was formed and decomposed into an FeV tosylimido species which generated the catalytically active FeIV tosylimide through a comproportionation process with the FeIII precursor.  相似文献   
4.
Journal of Analytical Chemistry - The present development involved a flow injection strategy using a mini-column of multiwalled carbon nanotubes and fluorescent detection (λex of 283 nm,...  相似文献   
5.
Sun  J.  Yuan  H. 《Experimental Mechanics》2021,61(3):565-580
Experimental Mechanics - Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients...  相似文献   
6.
Central European Journal of Operations Research - Sustainability practice within supply chains remains in an early development phase. Enterprises still need tools that support the integration of...  相似文献   
7.
8.
Nonlinear Dynamics - Given a data-set of Ribonucleic acid (RNA) sequences we can infer the phylogenetics of the samples and tackle the information for scientific purposes. Based on current data and...  相似文献   
9.
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   
10.

In this paper, we design a Branch and Bound algorithm based on interval arithmetic to address nonconvex robust optimization problems. This algorithm provides the exact global solution of such difficult problems arising in many real life applications. A code was developed in MatLab and was used to solve some robust nonconvex problems with few variables. This first numerical study shows the interest of this approach providing the global solution of such difficult robust nonconvex optimization problems.

  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