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   247662篇
  免费   3796篇
  国内免费   608篇
化学   130785篇
晶体学   3509篇
力学   10733篇
综合类   6篇
数学   29677篇
物理学   77356篇
  2021年   2121篇
  2020年   2410篇
  2019年   2591篇
  2018年   3640篇
  2017年   3344篇
  2016年   5187篇
  2015年   3603篇
  2014年   4915篇
  2013年   11749篇
  2012年   10355篇
  2011年   11871篇
  2010年   7921篇
  2009年   7442篇
  2008年   10621篇
  2007年   10807篇
  2006年   10097篇
  2005年   9209篇
  2004年   8391篇
  2003年   7248篇
  2002年   6877篇
  2001年   7192篇
  2000年   5576篇
  1999年   4250篇
  1998年   3390篇
  1997年   3365篇
  1996年   3214篇
  1995年   2879篇
  1994年   2769篇
  1993年   2653篇
  1992年   3028篇
  1991年   2959篇
  1990年   2867篇
  1989年   2660篇
  1988年   2663篇
  1987年   2668篇
  1986年   2459篇
  1985年   3292篇
  1984年   3532篇
  1983年   2841篇
  1982年   3082篇
  1981年   3056篇
  1980年   2879篇
  1979年   2969篇
  1978年   3047篇
  1977年   3000篇
  1976年   3127篇
  1975年   2887篇
  1974年   2857篇
  1973年   2960篇
  1972年   1836篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
61.
62.
In this study, the functional interaction of HPLW peptide with VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) was determined by using fast 15N‐edited NMR spectroscopic experiments. To this aim, 15N uniformly labelled HPLW has been added to Porcine Aortic Endothelial Cells. The acquisition of isotope‐edited NMR spectroscopic experiments, including 15N relaxation measurements, allowed a precise characterization of the in‐cell HPLW epitope recognized by VEGFR2.  相似文献   
63.
64.
65.
66.
S. D. Campos 《中国物理C(英文版)》2020,44(10):103103-103103-10
This work presents the subtraction procedure and the Regge cut in the logarithmic Regge pole approach. The subtraction mechanism leads to the same asymptotic behavior as previously obtained in the non-subtraction case. The Regge cut, in contrast, introduces a clear role to the non-leading contributions for the asymptotic behavior of the total cross-section. From these results, some simple parameterization is introduced to fit the experimental data for the proton-proton and antiproton-proton total cross-section above some minimum value up to the cosmic-ray. The fit parameters obtained are used to present predictions for the \begin{document}$ \rho(s)$\end{document} -parameter as well as to the elastic slope \begin{document}$ B(s)$\end{document} at high energies.  相似文献   
67.
This study compares the physicochemical properties of six electrolytes comprising of three salts: LiFTFSI, NaFTFSI and KFTFSI in two solvent mixtures, the binary (3EC/7EMC) and the ternary (EC/PC/3DMC). The transport properties (conductivity, viscosity) as a function of temperature and concentration were modeled using the extended Jones-Dole-Kaminsky equation, the Arrhenius model, and the Eyring theory of transition state for activated complexes. Results are discussed in terms of ionicity, solvation shell, and cross-interactions between electrolyte components. The application of the six formulated electrolytes in symmetrical activated carbon (AC)//AC supercapacitors (SCs) was characterized by cyclic voltammetry (CV), galvanostatic cycling with potential limitation (GCPL), electrochemical impedance spectroscopy (EIS) and accelerated aging. Results revealed that the geometrical flexibility of the FTFSI anion allows it to access and diffuse easily in AC whereas its counter ions (Li+, Na+ or K+) can remain trapped in porosity. However, this drawback was partially resolved by mixing LiFTFSI and KFTFSI salts in the electrolyte.  相似文献   
68.
NOx mitigation is a central focus of combustion technologies with increasingly stringent emission regulations. NOx can also enhance the autoignition of hydrocarbon fuels and can promote soot oxidation. The reaction between allyl radical (C3H5) and NOx plays an important role in the oxidation kinetics of propene. In this work, we measured the absolute rate coefficients for the redox reaction between C3H5 and NOx over the temperature range of 1000–1252 K and pressure range of 1.5–5.0 bar using a shock tube and UV laser absorption technique. We produced C3H5 by shock heating of C3H5I behind reflected shock waves. Using a Ti:Sapphire laser system with frequency quadrupling, we monitored the kinetics of C3H5 at 220 nm. Unlike low-temperature chemistry, the two target reactions, C3H5 + NO → products (R1) and C3H5 + NO2 → products (R2), exhibited a strong positive temperature dependence for this radical-radical type reaction. However, these reactions did not show any pressure dependence over the pressure range of 1.5–5.0 bar, indicating that the measured rate coefficients are close to the high-pressure limit. The measured values of the rate coefficients resulted in the following Arrhenius expressions (in unit of cm3/molecule/s):k1(C3H5+NO)=1.49×10?10exp(?6083.6KT)(1017?1252K)k2(C3H5+NO2)=1.71×10?10exp(?3675.7KT)(1062?1250K)To our knowledge, these are the first high-temperature measurements of allyl + NOx reactions. The reported data will be highly useful in understanding the interaction of NOx with resonantly stabilized radicals as well as the mutual sensitization effect of NOx on hydrocarbon fuels.  相似文献   
69.
Algebras and Representation Theory - We introduce and study the category of twisted modules over a triangular differential graded bocs. We show that in this category idempotents split, that it...  相似文献   
70.
Luyen  D. T. 《Mathematical Notes》2022,112(1-2):239-250
Mathematical Notes - We study the multiplicity of weak solutions to the boundary-value problem $$\begin{alignedat}{2} - M\biggl(\iint_{\mathbb R^{2N}}|u(x)-u(y)|^2 K(x-y)\,d x\,d y\biggr)\mathscr...  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