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   356123篇
  免费   2393篇
  国内免费   984篇
化学   151303篇
晶体学   4845篇
力学   20880篇
综合类   5篇
数学   71870篇
物理学   110597篇
  2021年   1677篇
  2020年   1851篇
  2019年   2047篇
  2018年   18825篇
  2017年   19313篇
  2016年   12222篇
  2015年   3825篇
  2014年   4058篇
  2013年   9642篇
  2012年   14137篇
  2011年   28052篇
  2010年   17046篇
  2009年   17339篇
  2008年   22868篇
  2007年   27864篇
  2006年   8299篇
  2005年   14562篇
  2004年   10965篇
  2003年   10581篇
  2002年   7787篇
  2001年   6811篇
  2000年   5509篇
  1999年   3983篇
  1998年   3279篇
  1997年   3216篇
  1996年   3136篇
  1995年   2822篇
  1994年   2642篇
  1993年   2506篇
  1992年   2822篇
  1991年   2805篇
  1990年   2733篇
  1989年   2539篇
  1988年   2597篇
  1987年   2584篇
  1986年   2414篇
  1985年   3068篇
  1984年   3346篇
  1983年   2732篇
  1982年   2906篇
  1981年   2860篇
  1980年   2722篇
  1979年   2830篇
  1978年   2939篇
  1977年   2861篇
  1976年   2944篇
  1975年   2717篇
  1974年   2687篇
  1973年   2857篇
  1972年   1792篇
排序方式: 共有10000条查询结果,搜索用时 31 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.
A model of the explosive fragmentation of a thin ring is developed which takes into account the statistical dispersion of the relative fracture deformation along the length of the ring. A formula is proposed for calculating the velocity of the boundary of the region near a plastic rupture in which the plastic flow of the ring material ceases. Methods for the numerical and analytical calculation of the average number of fragments of the ring are developed. The calculation results are compared with available experimental data.  相似文献   
64.
In this paper, we have significantly modified an existing model for calculating the zeta potential and streaming potential coefficient of porous media and tested it with a large, recently published, high-quality experimental dataset. The newly modified model does not require the imposition of a zeta potential offset but derives its high salinity zeta potential behaviour from Stern plane saturation considerations. The newly modified model has been implemented as a function of temperature, salinity, pH, and rock microstructure both for facies-specific aggregations of the new data and for individual samples. Since the experimental data include measurements on samples of both detrital and authigenic overgrowth sandstones, it was possible to model and test the effect of widely varying microstructural properties while keeping lithology constant. The results show that the theoretical model represents the experimental data very well when applied to model data for a particular lithofacies over the whole salinity, from 10?5 to 6.3 mol/dm3, and extremely well when modelling individual samples and taking individual sample microstructure into account. The new model reproduces and explains the extreme sensitivity of zeta and streaming potential coefficient to pore fluid pH. The low salinity control of streaming potential coefficient by rock microstructure is described well by the modified model. The model also behaves at high salinities, showing that the constant zeta potential observed at high salinities arises from the development of a maximum charge density in the diffuse layer as it is compressed to the thickness of one hydrated metal ion.  相似文献   
65.
66.
67.
In this work, the effect of various properties of materials on vacuum breakdown initiated by laser radiation is considered. Estimating calculations are performed which show that the material of the target electrode distinctly affects the minimum energy of laser radiation needed for igniting a vacuum spark. The experimental studies carried out confirm the estimating calculations, and a number of materials are revealed which can be arranged in order of increase in the energy needed for the formation of breakdown in vacuum by the impact of a laser pulse.  相似文献   
68.
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages.  相似文献   
69.
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   
70.
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