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   2856篇
  免费   172篇
  国内免费   141篇
化学   983篇
晶体学   9篇
力学   104篇
综合类   14篇
数学   714篇
物理学   1345篇
  2024年   2篇
  2023年   45篇
  2022年   24篇
  2021年   43篇
  2020年   66篇
  2019年   51篇
  2018年   41篇
  2017年   57篇
  2016年   52篇
  2015年   66篇
  2014年   99篇
  2013年   155篇
  2012年   91篇
  2011年   117篇
  2010年   90篇
  2009年   175篇
  2008年   186篇
  2007年   271篇
  2006年   232篇
  2005年   137篇
  2004年   175篇
  2003年   148篇
  2002年   130篇
  2001年   118篇
  2000年   87篇
  1999年   81篇
  1998年   71篇
  1997年   95篇
  1996年   66篇
  1995年   38篇
  1994年   23篇
  1993年   15篇
  1992年   19篇
  1991年   10篇
  1990年   7篇
  1989年   8篇
  1988年   15篇
  1987年   9篇
  1986年   9篇
  1985年   8篇
  1984年   4篇
  1983年   4篇
  1982年   4篇
  1981年   6篇
  1980年   3篇
  1979年   6篇
  1978年   2篇
  1977年   2篇
  1975年   2篇
  1959年   1篇
排序方式: 共有3169条查询结果,搜索用时 31 毫秒
1.
We provide a theoretical study of Algebraic Geometry codes constructed from abelian surfaces defined over finite fields. We give a general bound on their minimum distance and we investigate how this estimation can be sharpened under the assumption that the abelian surface does not contain low genus curves. This approach naturally leads us to consider Weil restrictions of elliptic curves and abelian surfaces which do not admit a principal polarization.  相似文献   
2.
In an attempt to create a polymer brush-based platform for the systematic study for anti-biofouling surfaces, the benefits of surface initiated, visible light-mediated radical polymerization are utilized to fabricate well-defined, chemically ambiguously patterned surfaces. A variety of analytical tools are used to illustrate the precise tuning of surface chemistry and thoroughly characterize spatially well-defined, hydrophilic/hydrophobic surfaces composed of poly(ethylene glycol methacrylate) and poly(trifluoroethyl methacrylate) with chemical definition on the micron scale. Advantages of both visible light-mediated photopolymerization and traditional copper-catalyzed atom transfer radical polymerization are combined to achieve both high spatial control and expanded monomer tolerance. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 253–262  相似文献   
3.
The immobilization of reversible addition–fragmentation chain transfer (RAFT) agents on silica for surface‐initiated RAFT polymerizations (SI‐RAFT) via the Z‐group approach was studied systematically in dependence of the functionality of the RAFT‐agent anchor group. Monoalkoxy‐, dialkoxy‐, and trialkoxy silyl ether groups were incorporated into trithiocarbonate‐type RAFT agents and bound to planar silica surfaces as well as to silica nanoparticles. The immobilization efficiency and the structure of the bound RAFT‐agent film varied strongly in dependence of the used solvent (toluene vs. 1,2‐dimethoxyethane) and the anchor group functionality, as evidenced by atomic force microscopy, transmission electron microscopy, dynamic light scattering, and UV/Vis spectroscopy. Surface‐initiated RAFT polymerizations using functionalized silica nanoparticles revealed that grafted oligomers, which often occur in SI‐RAFT, are not formed within the crosslinked structures that originate from the immobilization, and that RAFT‐agent films that show less aggregation during the immobilization are more efficient during SI‐RAFT in terms of polymer grafting density. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 103–113  相似文献   
4.
5.
Zwitterionic polymers are important in a wide range of industrial, biological and medical fields. Their chemical structures include an equal amount of anion and cation groups, and such structures give rise to many unique functionalities, such as temperature response, anti‐polyelectrolyte effect, and strong hydration properties. In this review, we focus on the structures and applications of functional zwitterionic polymers on surfaces. We review three areas of applications according to the architecture of the polymeric systems: surface coating, complex solutions, and hydrogel. We review the simulation and theory work and highlight some outlooks for further development.  相似文献   
6.
王洁  叶雨晴  李源  马小杰  王博 《化学学报》2022,80(9):1338-1350
COVID-19在全球的大流行对人类的健康生活和社会的正常运行都造成了严重的危害. 阻断致病微生物通过受污染表面与人类间接接触传播, 或者避免与其直接接触是保护我们免受伤害的主要方法. 目前的解决措施包括设计开发抗菌抗病毒表面涂层和研发由自清洁薄膜或织物制成的个人防护设备. 综述了近年来几种研究广泛的金属、金属氧化物、金属有机框架材料等用于抗菌抗病毒涂层或薄膜的工作, 对其作用机制和微生物灭活效果进行了总结讨论, 并且评估了其本身的毒性以及实际应用的局限性, 最后就抗菌抗病毒涂层和薄膜开发的挑战和新兴研究方向提出了未来展望.  相似文献   
7.
《Physics letters. A》2020,384(20):126412
Capillary condensation, which takes place in confined geometries, is the first-order vapor-to-liquid phase transition and is explained by the Kelvin equation, but the equation's applicability for arbitrarily curved surface has been long debated and is severe problem. Recently, we have proposed generic dynamic equations for moving surfaces. Application of the equations to the vapor/fluid interfaces in chemical equilibrium conditions nearly trivially solves the generalization problem for the Kelvin equation. The equations are universally true for any surfaces: atomic, molecular, micro or macro scale, real or virtual, Riemannian or pseudo-Riemannian, active or passive.  相似文献   
8.
9.
为了设计低投射比的超短焦投影物镜,本文采用自由曲面和折反式的光路结构设计了一种具有低投射比的超短焦投影物镜系统。该物镜由一个旋转对称的折射透镜组和一个自由曲面反射镜组成。采用11.938 mm的数字微镜器件(DMD)作为空间光调制器产生图像源。采用法线加权迭代优化的方法计算自由曲面。最后,分析了系统的性能。仿真结果表明:超短焦投影物镜可在580 mm的投影距离处实现3048 mm尺寸的大屏幕投影,系统的投射比低至0.19,系统的最大畸变小于0.72%。能够满足低投射比超短焦投影物镜的设计要求。该投影系统具有低投射比、低畸变、投影效果好等优点,可为超短焦投影系统的进一步发展提供有益参考。  相似文献   
10.
A series of new mono- and bis-terpyridine complexes [Mn(tpyOH)Cl2] ( 1 ), [Ni(tpyOH)2](PF6)2 ( 2 ) and [Zn(tpyO)(η1-OCOCH3)(H2O)]⋅3H2O ( 4 ) containing 4′-hydroxy-2,2′:6′,2″-terpyridine (tpyOH) were synthesized and structurally characterized using elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction. The reaction of MnCl2 with tpyOH in a mixture of methanol and CH2Cl2 resulted in the formation of 1 . The X-ray crystal structure of 1 reveals that Mn(II) is penta-coordinated by three nitrogen atoms from tpyOH and two Cl in a slightly distorted trigonal bipyramidal geometry. Complex 2 was also prepared by the reaction of nickel(II) chloride with tpyOH in a methanolic medium in the presence of NH4PF6. Notably, the complex [Ni(tpyOH)(tpyO)]PF6 ( 3 ), obtained during the crystallization of 2 from dichloromethane, was characterized using X-ray crystallography which shows that six nitrogen atoms from terpyridine ligands occupy the coordination sites around the Ni(II) centre in a distorted octahedral geometry with four longer bonds and two shorter Ni N bonds. The reaction of zinc(II) acetate with tpyOH in a mixture of methanol and CH2Cl2 led to the formation of 4 . The crystal structure of 4 reveals the formation of penta-coordinated Zn(II) complex containing three nitrogen atoms from tpyO, a monodentate acetate ligand and one coordinated water molecule. Hirshfeld surface analyses and two-dimensional fingerprint plots show that the main interactions are O…H/H…O contacts in 1 , 3 and 4 . The thermal decomposition reactions of 1 , 2 and 4 were studied using thermogravimetric analysis in detail due to their different structures. The solution luminescence features of 1 , 2 and 4 include high-energy intense π → π* intraligand and low-energy metal-to-ligand charge transfer transitions at room temperature. The calcination of the coordination complexes led to the formation of corresponding nano metal oxides. The products were structurally characterized using infrared spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The average particle size using Scherrer's equation was calculated to be below 50 nm.  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