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   4007篇
  免费   544篇
  国内免费   417篇
化学   2902篇
晶体学   27篇
力学   175篇
综合类   45篇
数学   594篇
物理学   1225篇
  2024年   8篇
  2023年   76篇
  2022年   75篇
  2021年   118篇
  2020年   143篇
  2019年   158篇
  2018年   150篇
  2017年   126篇
  2016年   198篇
  2015年   180篇
  2014年   255篇
  2013年   290篇
  2012年   333篇
  2011年   317篇
  2010年   233篇
  2009年   219篇
  2008年   259篇
  2007年   215篇
  2006年   210篇
  2005年   176篇
  2004年   143篇
  2003年   124篇
  2002年   146篇
  2001年   127篇
  2000年   80篇
  1999年   72篇
  1998年   65篇
  1997年   41篇
  1996年   42篇
  1995年   46篇
  1994年   53篇
  1993年   35篇
  1992年   36篇
  1991年   42篇
  1990年   31篇
  1989年   16篇
  1988年   16篇
  1987年   10篇
  1986年   8篇
  1985年   15篇
  1984年   7篇
  1983年   5篇
  1982年   6篇
  1981年   8篇
  1980年   6篇
  1979年   6篇
  1978年   5篇
  1977年   5篇
  1971年   5篇
  1962年   3篇
排序方式: 共有4968条查询结果,搜索用时 15 毫秒
991.
Two hetero-bimetallic [Zn(II)2M(II)] (M = Ca and Sr) complexes [Zn2Ca(L)(OAc)2] ( 1 ) and [Zn2Sr(L)(OAc)2] ( 2 ) with a novel asymmetrical bis(salamo)-type tetraoxime ligand (H5L) were designed and synthesized, and characterized by elemental analyses, FT-IR spectra, UV–vis absorption spectra, Density Functional Theory (DFT) calculation, Hirshfeld surface analyses and X-ray single crystal diffractions. Compared with the symmetric bis(salamo)-type ligands, the ligand H5L and its [Zn(II)2M(II)] (M = Ca and Sr) asymmetrical bis(salamo)-type complexes synthesized for the first time in this paper have more novel structures and better properties. The results of ultraviolet titration show that the coordination ratio of ligand, alkaline earth metal and transition metal is 1:1:2. Complexes 1 and 2 have good luminescent properties and obvious antimicrobial activities.  相似文献   
992.
993.
A recent experimental breakthrough identified the last bound neutron-rich nuclei in fluorine and neon isotopes. Based on this finding, we perform a theoretical study of Z = 9, 10, 11, 12 isotopes in the relativistic mean field(RMF) model. The mean field parameters are assumed from the PK1 parameterization, and the pairing correlation is described by the particle number conservation BCS(FBCS) method recently formulated in the RMF model. We show that the FBCS approach plays an essential role in reproducing experimental results of fluorine and neon isotopes. Furthermore, we predict ~(39)Na and ~(40)Mg to be the last bound neutron-rich nuclei in sodium and magnesium isotopes.  相似文献   
994.
Now, there have been many different methods to calculate one-loop amplitudes. Two of them are the unitarity cut method and the generalized unitarity cut method. In this short paper, we present an explicit connection between these two methods, especially how the extractions of triangle and bubble coefficients are equivalent to each other.  相似文献   
995.
996.
The tumor microenvironment (TME) significantly influences cancer evolution and therapeutic efficacy. Targeting biofunctional molecules to the TME has long been appreciated as a means of raising local drug concentrations and reducing systemic toxicities. The booming nanotechnology field has realized the importance of cathepsin B to derive a variety of intelligent enzyme-responsive nanosized drug delivery systems (nanoDDS) to improve treatment responses and clinical outcomes. In this tutorial review, after introducing the molecular structure and physiological/pathological functions of cathepsin B, the outstanding achievements of cathepsin B-responsive nanoplatforms in the precise diagnosis, targeted therapy, and synergistic theranostics of malignant tumors are systematically described. Finally, the challenges of enzyme-substrate incompatibility, low diagnostic sensitivity, mass production and biocompatibility of multifunctional nanoDDS are considered in order to successfully promote them to clinical applications.  相似文献   
997.
Abstract

Two new compounds, versicolones A and B (1 and 2), and three known pyrone derivatives (3?5) were isolated from the insect-associated fungus Aspergillus versicolor. Their structures were elucidated through a combination of HRESIMS and NMR spectroscopic analysis. Versicolone A (1) was revealed as a coumarin derivative with the rare 5-alkyl side chain substitution. Compound 5 exhibited significant antioxidant activity with EC50 value of 8.0?μM in the ABTS (2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid) assay, which was more than 2-fold potency of the positive control trolox.  相似文献   
998.
We study the generation of quadruple-transparency windows and the implementation of a conversion between slow and fast light in a hybrid optomechanical system. By demonstrating the generation of these transparency windows one by one, we analyze the physical mechanism through which each transparency window forms in detail. Additionally, we discuss how the system parameters affect the formation of transparency windows and conclude that the location, width, and absorption of each transparency window can be arbitrarily manipulated by varying the appropriate parameters. Moreover, when the pump field is changed from red to blue detuning, conversions between slow and fast light occur in the output field. These interesting properties of the output field can be applied to achieve the coherent control and manipulation of light pulses using cavity optomechanical system.  相似文献   
999.
本文依照四川大学某理论力学教学班实际教学改革的经验,通过具体举例说明计算机技术在理论力学教学中尚未开发的巨大潜力,减小数学运算使学生重点关注理论力学基本原理,批量求解使学生提前接触实际应用案例,普适性求解使学生深化对处理多变量问题的认识。同时本文还探讨了理论力学教学改革的方向和目的,即把教学重点放在普适的教学方法上,借助计算机求解多刚体、多变量问题,以期有助于理论力学教材更好地适应时代发展。  相似文献   
1000.
关于多元非线性方程的Broyden方法   总被引:2,自引:0,他引:2  
安恒斌  白中治 《计算数学》2004,26(4):385-400
本文提出了求解多元非线性方程的Broyden方法,讨论了该方法的局部与半局部收敛性,并估计了其超线性收敛速度.数值实验表明,新方法是可行有效的,并且其计算效率高于方向Newton法和方向割线法.  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