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   189396篇
  免费   19552篇
  国内免费   14415篇
化学   104484篇
晶体学   1999篇
力学   13090篇
综合类   784篇
数学   45372篇
物理学   57634篇
  2024年   276篇
  2023年   2253篇
  2022年   3504篇
  2021年   4031篇
  2020年   4639篇
  2019年   4410篇
  2018年   13441篇
  2017年   13023篇
  2016年   11080篇
  2015年   6161篇
  2014年   6935篇
  2013年   8967篇
  2012年   14023篇
  2011年   20650篇
  2010年   12906篇
  2009年   12896篇
  2008年   13947篇
  2007年   15209篇
  2006年   6706篇
  2005年   6744篇
  2004年   5748篇
  2003年   5381篇
  2002年   4190篇
  2001年   2903篇
  2000年   2628篇
  1999年   2547篇
  1998年   2211篇
  1997年   1948篇
  1996年   2046篇
  1995年   1744篇
  1994年   1506篇
  1993年   1251篇
  1992年   1126篇
  1991年   988篇
  1990年   826篇
  1989年   659篇
  1988年   516篇
  1987年   466篇
  1986年   446篇
  1985年   345篇
  1984年   255篇
  1983年   219篇
  1982年   180篇
  1981年   131篇
  1980年   112篇
  1979年   68篇
  1978年   57篇
  1973年   43篇
  1914年   45篇
  1909年   41篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
For the orthosymplectic Lie superalgebra ◂⋅▸OSP(2,2), we choose a set of basis matrices. A linear combination of those basis matrices presents a spatial spectral matrix. The compatible condition of the spatial part and the corresponding temporal parts of the spectral problem leads to a generalized super AKNS (GSAKNS) hierarchy. By making use of the supertrace identity, the obtained GSAKNS hierarchy can be written as the super bi-Hamiltonian structures.  相似文献   
82.
Photoactivated chemotherapy (PACT) has appealing merits over traditional chemotherapy as well as photodynamic therapy (PDT) by virtue of its spatial and temporal control on drug activity and oxygen-independent mechanisms of action. However, the short photoactivation wavelengths, e.g., visible light–activated Ru(II)-based PACT agents, limit the clinical application severely. In this work, a facile construction of supramolecular nanoparticles from a poly(ethylene glycol) (PEG)-modified [Ru(dip)2(py-SO3)]+ (abbreviated as Ru-PEG, dip = 4,7-diphenyl-1,10-phenanthroline, py-SO3 = pyridine-2-sulfonate) and 1,3-phenylenebis(pyren-1-ylmethanone) (BP) is shown. While Ru-PEG may undergo photoinduced ligand dissociation and release anticancer species of [Ru(dip)2(H2O)2]2+, BP has extremely large two-photon absorption cross sections (δ2) in the NIR region and intense fluorescence over the wavelengths where Ru-PEG has strong absorption. Thus, two-photon excitation of BP followed by an efficient Förster resonance energy transfer (FRET) from BP to Ru-PEG may lead to a potent inactivation against cisplatin-resistant cancer cells and 3D multicellular tumor spheroids (MCTSs). The residue fluorescence of BP also allows the cellular uptake of the particles to be visualized. This work provides a universal and convenient strategy to realize theranostic PACT in the ideal phototherapeutic window of 650–900 nm.  相似文献   
83.
84.
A new approach has been developed to improve SO2 sorption by cyano‐containing ionic liquids (ILs) through tuning the basicity of ILs and cyano–sulfur interaction. Several kinds of cyano‐containing ILs with different basicity were designed, prepared, and used for SO2 capture. The interaction between these cyano‐containing ILs and SO2 was investigated by FTIR and NMR methods. Spectroscopic investigations and quantum chemical calculations showed that dramatic effects on SO2 capacity originate from the basicity of the ILs and enhanced cyano–sulfur interaction. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the ILs. This efficient and reversible process, achieved by tuning the basicity of ILs, is an excellent alternative to current technologies for SO2 capture.  相似文献   
85.
86.
A series of tetraimidazolium salts with different anions was prepared and applied in the isomerization of β-pinene oxide. After examining the activity of different catalysts, a remarkable enhancement of the selectivity of perillyl alcohol (47 %) was obtained over [PEimi][HNO3]4 under mild reaction conditions and using DMSO as the solvent. Furthermore, noncovalent interactions between solvent molecules and the catalyst were found by FT-IR spectroscopy and confirmed by computational chemistry. The homogeneous catalyst showed excellent stability and was reused up to six times without significant loss.  相似文献   
87.
Chen  Haiyang  Gao  Fangzheng 《Nonlinear dynamics》2022,108(2):1319-1338
Nonlinear Dynamics - Based on a mixed control strategy, this study addresses the finite-time stabilization with extended dissipativity for Markov jump systems (MJSs) with unreliable...  相似文献   
88.
Guo  Yan  Li  Zhuang  Wei  Yuxi  Zhang  Xinxu  Shi  Kexin 《Journal of Solid State Electrochemistry》2022,26(4):1051-1065
Journal of Solid State Electrochemistry - Polyvinylpyrrolidone (PVP) and graphene (G)-modified iron oxides (Fe2O3-PVP-G) are prepared by a simple hydrothermal reaction. Their morphology and...  相似文献   
89.
90.
The Ramanujan Journal - Inspired by Andrews and Merca’s recent work on the number of even parts over all partitions into distinct parts, we introduce a new kind of Beck type identities, which...  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