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   17535篇
  免费   3125篇
  国内免费   2712篇
化学   12856篇
晶体学   336篇
力学   1064篇
综合类   219篇
数学   2074篇
物理学   6823篇
  2024年   20篇
  2023年   327篇
  2022年   444篇
  2021年   583篇
  2020年   678篇
  2019年   729篇
  2018年   584篇
  2017年   667篇
  2016年   766篇
  2015年   835篇
  2014年   1046篇
  2013年   1433篇
  2012年   1643篇
  2011年   1769篇
  2010年   1292篇
  2009年   1251篇
  2008年   1294篇
  2007年   1197篇
  2006年   1002篇
  2005年   843篇
  2004年   733篇
  2003年   530篇
  2002年   517篇
  2001年   464篇
  2000年   442篇
  1999年   318篇
  1998年   246篇
  1997年   197篇
  1996年   204篇
  1995年   182篇
  1994年   180篇
  1993年   144篇
  1992年   138篇
  1991年   108篇
  1990年   97篇
  1989年   94篇
  1988年   53篇
  1987年   56篇
  1986年   54篇
  1985年   44篇
  1984年   38篇
  1983年   23篇
  1982年   11篇
  1981年   15篇
  1980年   9篇
  1979年   14篇
  1978年   6篇
  1977年   6篇
  1976年   11篇
  1975年   8篇
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
1.
Fan  K.  Lu  R. S.  Liang  K. K.  Hou  Z. C. 《High Energy Chemistry》2022,56(4):264-269
High Energy Chemistry - Modification of Polyvinylidene fluoride (PVDF) by radiation grafting is a research hotspot in recent years. In this study, the monomer 2-Hydroxyethyl methacrylate (HEMA) was...  相似文献   
2.
International Journal of Theoretical Physics - In this work, we give an analytical derivation of the reduced density matrix between two qubits in a cavity field, which is described by the quantum...  相似文献   
3.
4.
Acridone as a new kind of visible light photocatalyst has been developed to catalyze metal free atom transfer radical polymerization (ATRP). The photocatalyst possess low excited state potential as can undergo an oxidative quenching pathway to initiate ATRP of vinyl monomers. Kinetic study and light on/off reaction demonstrate the “living”/controlled nature of the polymerization by light. Block copolymers can be achieved by using PMMA as macroinitiator to reinitiate polymerization of other vinyl monomers, which shows highly preserved Br chain-end functionality in the synthesized polymers. Moreover, the polymerization can be conducted under air atmosphere as most photocatalysts need anaerobic condition, which may give inspiration of further application of this kind of photocatalyst.  相似文献   
5.
In this paper, let (Mn,g,dμ) be n-dimensional noncompact metric measure space which satisfies Poincaré inequality with some Ricci curvature condition. We obtain a Liouville theorem for positive weak solutions to weighted p-Lichnerowicz equation
p,fv+cvσ=0,
where c0,m>n1,1<p<m?1+(m?1)(m+3)2,σp?1 are real constants.  相似文献   
6.
计算了在两个假想的星际航行方案中,与"双子佯谬"相关的时间差别.这种差别体现了惯性与非惯性参考系经历的时间有绝对差异,而不再是"相对"效应.  相似文献   
7.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling.  相似文献   
8.
An organocatalytic asymmetric chlorinative dearomatization of naphthols was realized for the first time, providing chiral naphthalenones with a Cl-containing all-substituted stereocenter in excellent yields and enantioselectivity (up to 97% yield and 96% ee). The reaction features mild reaction conditions, good tolerance of diverse functional groups and simple reaction operation.  相似文献   
9.
A class of acceptor–donor–acceptor chromophoric small-molecule non-fullerene acceptors, 1–4, with difluoroboron(iii) β-diketonate (BF2bdk) as the electron-accepting moiety has been developed. Through the variation of the central donor unit and the modification on the peripheral substituents of the terminal BF2bdk acceptor unit, their photophysical and electrochemical properties have been systematically studied. Taking advantage of their low-lying lowest unoccupied molecular orbital energy levels (from −3.65 to −3.72 eV) and relatively high electron mobility (7.49 × 10−4 cm2 V−1 s−1), these BF2bdk-based compounds have been employed as non-fullerene acceptors in organic solar cells with maximum power conversion efficiencies of up to 4.31%. Moreover, bistable resistive memory characteristics with charge-trapping mechanisms have been demonstrated in these BF2bdk-based compounds. This work not only demonstrates for the first time the use of a boron(iii) β-diketonate unit in constructing non-fullerene acceptors, but also provides more insights into designing organic materials with multi-functional properties.

Boron(iii) β-diketonates have been demonstrated to serve as multi-functional materials in NFA-based OPVs and organic resistive memories.  相似文献   
10.
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes.  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