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   1668篇
  免费   313篇
  国内免费   148篇
化学   1047篇
晶体学   10篇
力学   85篇
综合类   28篇
数学   242篇
物理学   717篇
  2024年   3篇
  2023年   32篇
  2022年   37篇
  2021年   43篇
  2020年   64篇
  2019年   68篇
  2018年   58篇
  2017年   38篇
  2016年   75篇
  2015年   70篇
  2014年   79篇
  2013年   112篇
  2012年   129篇
  2011年   146篇
  2010年   81篇
  2009年   92篇
  2008年   86篇
  2007年   93篇
  2006年   95篇
  2005年   79篇
  2004年   79篇
  2003年   51篇
  2002年   53篇
  2001年   29篇
  2000年   28篇
  1999年   46篇
  1998年   42篇
  1997年   27篇
  1996年   37篇
  1995年   31篇
  1994年   27篇
  1993年   27篇
  1992年   24篇
  1991年   24篇
  1990年   19篇
  1989年   25篇
  1988年   21篇
  1987年   12篇
  1986年   9篇
  1985年   8篇
  1984年   2篇
  1983年   3篇
  1982年   2篇
  1981年   2篇
  1980年   4篇
  1979年   4篇
  1978年   2篇
  1976年   4篇
  1973年   4篇
  1930年   1篇
排序方式: 共有2129条查询结果,搜索用时 375 毫秒
121.
A Cayley graph Γ=Cay(G,S)is said to be normal if G is normal in Aut Γ.In this paper,we investigate the normality problem of the connected 11-valent symmetric Cayley graphs Γ of finite nonabelian simple groups G,where the vertex stabilizer Av is soluble for A=Aut Γ and v ∈ VΓ.We prove that either Γ is normal or G=A5,A10,A54,A274,A549 or A1099.Further,11-valent symmetric nonnormal Cayley graphs of A5,A54 and A274 are constructed.This provides some more examples of nonnormal 11-valent symmetric Cayley graphs of finite nonabelian simple groups after the first graph of this kind(of valency 11)was constructed by Fang,Ma and Wang in 2011.  相似文献   
122.
Venetoclax has emerged as a breakthrough for treatment of leukemia with a wide interindividual variability in pharmacokinetics. Herein, a rapid, sensitive, and reliable UPLC-MS/MS method for quantification of venetoclax in plasma was developed and validated. The method was operated in the multiple-reaction monitoring (MRM) mode to detect venetoclax at m/z transition 868.5 > 321.0 and IS at 875.5 > 321.0, respectively. Protein precipitation prior to injection into the LC-MS/MS and the analyte was separated on an ACQUITY UPLC BEH C18 column by gradient elution with acetonitrile and 0.1% formic acid in water. Linear calibration curves were obtained in the range of 25–8000 ng/mL. The specificity, recovery, matrix effect, and stability also met the acceptance criteria of FDA guidance. The method was successfully applied to analyze plasma in acute myeloid leukemia (AML) patients. The peak plasma concentration (Cmax) of venetoclax in Chinese AML patient was 2966.0 ± 1595.0 ng/mL while the trough concentration (Cmin) was 1018.0 ± 729.4 ng/mL. Additionally, Cmax and Cmin showed a positive correlation with AST levels. Furthermore, Cmax was significantly higher in the older patients. The present method can be applied for TDM of venetoclax in treatment of hematological cancers.  相似文献   
123.
124.
High-yield purity chain-like one-dimensional nanostructures consisting of single crystal Fe nanoparticles have been produced by using solution dispersion approach. Room temperature magnetic measurement shows that the as-fabricated Fe nanochains are ferromagnetic with a high saturation magnetization (203 emu/g) whereas the nanoparticles are single magnetic domains, which indicate that the as-synthesized products have superparamagnetism behavior with the saturation magnetization of about 28 emu/g. Maybe this results from the directional alignment of the nanoparticles. The excellent characteristic may have led to the potential applications in spin filtering, high density magnetic recording, and nanosensors.  相似文献   
125.
126.
127.
Differentiation of biologically important thiols, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) is still a challenging task. Herein, we present a novel fluorescent chemodosimeter capable of selectively detecting Cys over other biothiols including Hcy and GSH and other amino acids by a facile thiol‐Michael addition/transcyclization rearrangement cascade click process. The unique transcyclization step is critical for the selectivity as a result of the kinetically favorable formation of a six‐membered ring with the Cys Michael adduct. Moreover, the probe adopts a distinctive dual quenching mechanism—photoinduced electron transfer (PET) and photoinduced intramolecular charge transfer (ICT) to deliver a drastic turn‐on fluorescence response only at the Cys‐selective transcylization step. The judicious selection of strong electron‐withdrawing naphthalimide fluorophore with maleimide group enhances the electrophilicity and thus reactivity for the cascade process leading to fast detection and ultrasensitivity with a detection limit of 2.0 nm (S/N=3). The probe has demonstrated its practical utility potential in Cys imaging in live cells.  相似文献   
128.
L&#;  LinHui  Ye  YanLin  Jiang  DongXing  Hua  Hui  Zheng  Tao  Li  ZhiHuan  Ge  YuCheng  Li  XiangQing  Lou  JianLing  Cao  ZhongXin  Song  YuShou  Xiao  Jun  Li  QiTe  Qiao  Rui  You  HaiBo  Chen  RuiJiu  Xu  HuShan  Wang  JianSong  Guo  ZhongYan  Zhang  XueYing  Li  Chen  Hu  ZhengGuo  Chen  RuoFu  Wang  Meng  Xu  ZhiGuo  Yue  Ke  Tang  Bin  Zang  YongDong  Zhang  XueHeng  Yao  XiangWu  Chen  JinDa  Bai  Zhen 《中国科学:物理学 力学 天文学(英文版)》2011,54(1):136-140

Knockout reaction experiment was carried out by using the 6He beams at 61.2 MeV/u impinging on a CH2 target. The α core fragments at forward angles were detected in coincidence with the recoiled protons at larger angles. From this exclusive measurement the valence nucleon knockout mechanism and the core knockout mechanism can be distinguished by the relation between the polar angles of the core fragments and the recoiled protons, respectively. It is demonstrated that the core knockout mechanism may result in some strong contamination to the real invariant mass spectrum.

  相似文献   
129.
The effect of laser fluence on the crystallization of amorphous silicon irradiated by a frequency-doubled Nd:YAG laser is studied both theoretically and experimentally. An effective numerical model is set up to predict the melting threshold and the optimized laser fluence for the crystallization of 200-nm-thick amorphous silicon. The variation of the temperature distribution with time and the melt depth is analyzed. Besides the model, the Raman spectra of thin films treated with different fluences are measured to confirm the phase transition and to determine the optimized fluence. The calculating results accord well with those obtained from the experimental data in this research.  相似文献   
130.
In this paper, we focus on the robust adaptive synchronization between two coupled chaotic neural networks with all the parameters unknown and time-varying delay. In order to increase the robustness of the two coupled neural networks, the key idea is that a sliding-mode-type controller is employed. Moreover, without the estimate values of the network unknown parameters taken as an updating object, a new updating object is introduced in the constructing of controller. Using the proposed controller, without any requirements for the boundedness, monotonicity and differentiability of activation functions, and symmetry of connections, the two coupled chaotic neural networks can achieve global robust synchronization no matter what their initial states are. Finally, the numerical simulation validates the effectiveness and feasibility of the proposed technique.  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