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   14990篇
  免费   566篇
  国内免费   52篇
化学   11981篇
晶体学   79篇
力学   254篇
数学   1929篇
物理学   1365篇
  2023年   111篇
  2022年   111篇
  2021年   527篇
  2020年   354篇
  2019年   405篇
  2018年   309篇
  2017年   236篇
  2016年   529篇
  2015年   532篇
  2014年   520篇
  2013年   999篇
  2012年   1052篇
  2011年   1199篇
  2010年   718篇
  2009年   714篇
  2008年   1018篇
  2007年   933篇
  2006年   822篇
  2005年   771篇
  2004年   638篇
  2003年   517篇
  2002年   419篇
  2001年   153篇
  2000年   123篇
  1999年   84篇
  1998年   89篇
  1997年   106篇
  1996年   117篇
  1995年   79篇
  1994年   81篇
  1993年   79篇
  1992年   63篇
  1991年   78篇
  1990年   59篇
  1989年   79篇
  1988年   66篇
  1987年   55篇
  1986年   53篇
  1985年   66篇
  1984年   81篇
  1983年   43篇
  1982年   71篇
  1981年   57篇
  1980年   55篇
  1979年   46篇
  1978年   54篇
  1977年   38篇
  1976年   34篇
  1975年   24篇
  1963年   20篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
1.
2.
Journal of Fourier Analysis and Applications - We develop a theory of Sobolev orthogonal polynomials on the Sierpiński gasket ( $$SG$$ ), which is a fractal set that can be viewed as a limit...  相似文献   
3.
4.
5.
Cedrela genus, a member of the Meliaceae family, presents both chemical characteristics associated with and those that distinguish it from the rest of its members. The presence of triterpenes and limonoids is the characteristic of the Meliaceae family, but the class and type of these chemical constituents are distinctive for each genus. Cedrela includes cycloartane, ursane, oleanane, tirucallane, butyrospermane, and apotirucallane triterpenes, and its limonoids belongs to six class and nine types, known as class Ia-type havanensines, class Ib-type delevoyin, class II-type gedunin, class IIIb-type andirobin, class IIIg-type mexicanolide, class IVa-type evoludone, class Va-type obacunol, class V-type limonin, and class VIII. Each of these structural arrangements includes specific traits, defined by their biosynthetic origin, which can be established by means of structural elucidation techniques, particularly 1H and 13C NMR, which assisted by 2D NMR techniques, allowing to deduce their structures unequivocally. The constant presence of these skeletal arrangements in Cedrela ensures that they are its chemophenetic markers and their recurrence is an important criterion for their identity. This review is a compilation of the occurrence of triterpenes and limonoids in Cedrela genus, detailing their biosynthetic association and collecting and organizing their NMR data, with the purpose of facilitating its location, analysis, and use in the phytochemical study of species from this genus.  相似文献   
6.
Methodology and Computing in Applied Probability - The family of the multivariate conditional hazard rate functions often reveals to be a convenient tool to describe the joint probability...  相似文献   
7.
Journal of Optimization Theory and Applications - We describe the dynamics of fluids with scattered polymer chains through a multi-field model accounting for weakly non-local inertia and...  相似文献   
8.
Journal of Dynamics and Differential Equations - In this paper we study the local and global well posedness of a fractional dissipative Klein–Gordon–Schrödinger type system in...  相似文献   
9.
CRANAD-2 is a fluorogenic curcumin derivative used for near-infrared detection and imaging in vivo of amyloid aggregates, which are involved in neurodegenerative diseases. We explore the performance of CRANAD-2 in two super-resolution imaging techniques, namely stimulated emission depletion (STED) and single-molecule localization microscopy (SMLM), with markedly different fluorophore requirements. By conveniently adapting the concentration of CRANAD-2, which transiently binds to amyloid fibrils, we show that it performs well in both techniques, achieving a resolution in the range of 45–55 nm. Correlation of SMLM with atomic force microscopy (AFM) validates the resolution of fine features in the reconstructed super-resolved image. The good performance and versatility of CRANAD-2 provides a powerful tool for near-infrared nanoscopic imaging of amyloids in vitro and in vivo.  相似文献   
10.
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