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   3154篇
  免费   484篇
  国内免费   432篇
化学   2324篇
晶体学   30篇
力学   225篇
综合类   45篇
数学   314篇
物理学   1132篇
  2024年   6篇
  2023年   54篇
  2022年   93篇
  2021年   97篇
  2020年   135篇
  2019年   103篇
  2018年   111篇
  2017年   112篇
  2016年   147篇
  2015年   129篇
  2014年   178篇
  2013年   219篇
  2012年   219篇
  2011年   299篇
  2010年   207篇
  2009年   198篇
  2008年   210篇
  2007年   197篇
  2006年   162篇
  2005年   125篇
  2004年   95篇
  2003年   76篇
  2002年   75篇
  2001年   69篇
  2000年   60篇
  1999年   73篇
  1998年   60篇
  1997年   50篇
  1996年   48篇
  1995年   51篇
  1994年   52篇
  1993年   48篇
  1992年   47篇
  1991年   37篇
  1990年   40篇
  1989年   32篇
  1988年   25篇
  1987年   31篇
  1986年   23篇
  1985年   13篇
  1984年   8篇
  1983年   11篇
  1982年   12篇
  1981年   5篇
  1980年   7篇
  1979年   5篇
  1977年   3篇
  1976年   2篇
  1975年   2篇
  1957年   4篇
排序方式: 共有4070条查询结果,搜索用时 15 毫秒
931.
Li  Jian  Yang  Yi Ni 《数学学报(英文版)》2021,37(12):1933-1946
Acta Mathematica Sinica, English Series - We study several stronger versions of sensitivity for minimal group actions, including n-sensitivity, thick n-sensitivity and blockily thick n-sensitivity,...  相似文献   
932.
Journal of Thermal Analysis and Calorimetry - In this investigation, a T-joint numerical welding simulation of thick steel plates is performed to estimate transient temperature distributions,...  相似文献   
933.
934.
In this paper, we consider the uniform estimates of strong solutions in the Mach number ? and t ∈ [0,) for the compressible nematic liquid crystal flows in a 3‐D bounded domain , provided the initial data are small enough and the density is close to the constant state. Here, we consider the case that the velocity field satisfies the Dirichlet boundary condition. Based on the uniform estimates, we obtain the global convergence of the compressible nematic liquid crystal system to the incompressible nematic liquid crystals system as the Mach number tends to zero.  相似文献   
935.
Liu  Shanshan  Liu  Xiujing  Wang  Qiang  Wang  Yingchao  Ji  Xingxiang  Yang  Guihua  Chen  Jiachuan  Ni  Yonghao 《Cellulose (London, England)》2022,29(3):1993-2003
Cellulose - Superhydrophobic and strong cellulosic paper was fabricated in a two-step process consisting of heavy refining and dip coating with PDMS (trimethylsiloxy-terminated poly...  相似文献   
936.
Fluorophores with emission in the second near-infrared window (NIR-II) have displayed salient advantages for biomedical applications. However, the common strategy of reducing the energy bandgap of fluorophores so as to achieve red-shifted wavelengths always leads to compromised fluorescent brightness. Herein, we propose a molecular design concept of “ring-fusion” to modify the acceptor of AIEgen that can extend the luminous wavelength from NIR-I to NIR-II. The fused-acceptor-containing fluorophore yielded, TTQP, has an enhanced absorption coefficient with a higher brightness in nanoparticle formation compared to its NIR-I emissive counterpart (TTQ-DP) with a non-fused acceptor. Theoretical calculation further confirms that the ring fusion can efficiently promote the rigidity and planarity of the electron-deficient core, leading to a lower reorganization energy and nonradiative decay. The TTQP NPs yielded thus allow sensitive NIR-II fluorescence imaging of vasculature and intestinal inflammation in mice models. Therefore, we anticipate that our work will provide a promising molecular-engineering strategy to enrich the library and broaden the application scope of NIR-II fluorophores.  相似文献   
937.
S-(Trifluoromethyl)benzothioate (TFBT) has been developed as an inexpensive, bench-stable, and user-friendly trifluoromethylthiolation reagent, which can be easily synthesized by using KF as the only fluorine source. By using TFBT, trifluoromethylthiolates with various counterions can be readily obtained. The synthetic application of TFBT was demonstrated by trifluoromethylthiolation-halogenation of arynes, bis(trifluoromethylthiolation)–halogenation of 1,2-benzdiynes, nucleophilic substitution of alkyl halides, deoxytrifluoromethylthiolation of alcohols, and cross-coupling with aryl and vinyl boronic acids.  相似文献   
938.
939.
This letter reports the application of the scanning heating laser source technique to detect microcracks that may be undetected by conventional methods.In the proposed approach,we monitor changes in the transmitted surface acoustic waves(SAWs) as a heating source is scanned over the crack.The experimental system for microcrack detection by a scanning heating laser source is obtained by exploiting the strong dependence of the transmission efficiency of acoustic pulses on the state of the contacts,whether open or closed,between the crack faces.Microcracks can be detected successfully by confirming the heating position at the point of maximal improvement of the transmission efficiency of the SAWs.  相似文献   
940.
Wang  Junru  Zhou  Yucheng  Shao  Yamin  He  Feng  Wu  Min  Ni  Henmei  Zheng  Yingping  Sun  Yueming 《Research on Chemical Intermediates》2019,45(4):1721-1735
Research on Chemical Intermediates - Hybrid materials of chitosan–silica (CS–SiO2) with nonprecious-metallic ions (Cu) immobilized on (Cu–M@CS–SiO2) were developed as green...  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