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   2035篇
  免费   425篇
  国内免费   312篇
化学   1580篇
晶体学   36篇
力学   124篇
综合类   23篇
数学   232篇
物理学   777篇
  2024年   6篇
  2023年   46篇
  2022年   76篇
  2021年   90篇
  2020年   118篇
  2019年   102篇
  2018年   110篇
  2017年   103篇
  2016年   128篇
  2015年   136篇
  2014年   162篇
  2013年   201篇
  2012年   227篇
  2011年   207篇
  2010年   141篇
  2009年   114篇
  2008年   110篇
  2007年   90篇
  2006年   64篇
  2005年   66篇
  2004年   58篇
  2003年   42篇
  2002年   50篇
  2001年   45篇
  2000年   47篇
  1999年   45篇
  1998年   22篇
  1997年   24篇
  1996年   23篇
  1995年   15篇
  1994年   9篇
  1993年   13篇
  1992年   16篇
  1991年   13篇
  1990年   3篇
  1989年   8篇
  1988年   7篇
  1987年   4篇
  1986年   2篇
  1985年   3篇
  1984年   4篇
  1983年   3篇
  1982年   7篇
  1981年   3篇
  1980年   1篇
  1979年   2篇
  1977年   3篇
  1975年   1篇
  1957年   1篇
  1936年   1篇
排序方式: 共有2772条查询结果,搜索用时 31 毫秒
151.
比较了高性能微通道板和标准型微通道板在经过相同或类似制管工艺处理前、后电阻的变化,测定了高性能微通道板分别在真空烘烤和2个不同阶段电子清刷后电阻随电压及温度的变化关系。实验结果表明:高性能微通道板的热稳定性优于标准型微通道板,其电阻温度系数为-0.007/℃;经过第二阶段清刷后,电阻随电压的变化缓慢,电压系数为-1.11×10-4V-1;用这种材料和工艺制作的低电阻、大动态范围、高稳定性微通道板可满足特种探测器的需求。  相似文献   
152.
A novel long-lasting afterglow phosphor ZrO2:Ti is prepared by the conventional solid-stated method and their luminescent properties are investigated. A bluish white strong and broad emissive band, which is attributed to originate from the recombination of electrons trapped by F+ centers and the holes created in Valence band, is observed under 254 nm UV irradiation. The identical color long afterglow, which lasts about 1 h, is found in the ZrO2:Ti phosphor after removing the 254 nm UV light. The mechanism of the long lasting phosphorescence (LLP) has been discussed based on the thermoluminescence (TL) results. The replacement of Zr by Ti produces more anion vacancies, resulting in the enhanced photoluminescence (PL) and LLP of ZrO2:Ti sample. These results indicate that ZrO2:Ti phosphor has potential promising applications.  相似文献   
153.
We design a new three-dimensional double-wing fractional-order chaotic system with three quadratic terms, confirmed by numerical simulation and circuit implementation. We then study the synchronization between the new double-wing fractional-order chaotic system and different Lorenz systems with different structures. In the process of the synchronization, the definition of ‘the simplest response system’ and the practical method of designing the circuit have been originally proposed. The circuit of ‘the simplest response system’ (even the simplest incommensurate-order response system), holding different structures with the drive system, of any one integral or fractional drive system now can be designed effectively and sufficiently. Our results are supported by numerical simulation and circuit implementation.  相似文献   
154.
Losartan 1 (Dup-753) is a nonpeptide angiotensin II receptor (type AT1) antagonist discovered by Duncia, J.V. et al. 1 in 1990 and its potassium salt (cozaar) has been marketed as an antihypertensive since 1995 2. 1 2 Starting from Dup-753, a great number of structural related compounds have been prepared by several laboratories and several antihypertensive drugs have been developed3. In order to find new and more active compounds, a novel type of Losartan analogues 2 was designed and syn…  相似文献   
155.
The expansion coefficient CD|L| of Coulomb potential 1/r12 of atomic system in hyper‐spherical harmonics is derived and the explicit expression is given.  相似文献   
156.
本文将报告对硅纳米线、多孔硅、Si C纳米棒和碳纳米管等一维纳米体系的本征拉曼光谱及其特征的研究结果 ,并讨论拉曼光谱在上述材料的几何和物理特性研究中的应用。  相似文献   
157.
The light-oxygen effect consists in a direct excitation of molecular oxygen dissolved in aqueous media of biosystems by the light; it provides the possibility to use lasers for therapeutic purposes. The wavelength of the used light should strictly correspond to the oxygen absorption bands. However, laser therapy also makes use of lasers emitting at 0.89 μm (outside the known oxygen bands), which suggests the action of a new photoreceptor. Here we argue that this mechanism of photoreception is a modification of the light-oxygen effect involving the absorption of photon simultaneously by the oxygen molecule and O-H stretch of the H20 molecule of liquid water.  相似文献   
158.
Synthetic metalloporphyrin are efficient models of the cytochrome P-450 family ofmono-oxygen enzymes and have been largely used as catalysts in oxidation of alkanesand epoxidation of alkenesl. Polymer-bonded metalloporphyrin reveal many advantageson the catalytic reaction, where the catalysts can be easily separated from the products,recovered, and reused2. Quaternary ammonium salts as phase transfer catalysts werewide used in aqueous-organic two-phase conditions. Unfortunately, most porphyrin…  相似文献   
159.
160.
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