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   4960篇
  免费   195篇
  国内免费   13篇
化学   3489篇
晶体学   42篇
力学   100篇
数学   514篇
物理学   1023篇
  2023年   47篇
  2022年   87篇
  2021年   161篇
  2020年   124篇
  2019年   140篇
  2018年   108篇
  2017年   109篇
  2016年   208篇
  2015年   161篇
  2014年   155篇
  2013年   325篇
  2012年   342篇
  2011年   391篇
  2010年   233篇
  2009年   246篇
  2008年   342篇
  2007年   305篇
  2006年   270篇
  2005年   228篇
  2004年   213篇
  2003年   164篇
  2002年   130篇
  2001年   72篇
  2000年   73篇
  1999年   57篇
  1998年   29篇
  1997年   34篇
  1996年   51篇
  1995年   40篇
  1994年   38篇
  1993年   31篇
  1992年   42篇
  1991年   15篇
  1990年   17篇
  1989年   15篇
  1988年   11篇
  1987年   15篇
  1986年   11篇
  1985年   14篇
  1984年   12篇
  1983年   7篇
  1982年   10篇
  1981年   11篇
  1980年   11篇
  1978年   7篇
  1977年   8篇
  1976年   7篇
  1975年   6篇
  1974年   7篇
  1968年   5篇
排序方式: 共有5168条查询结果,搜索用时 15 毫秒
1.
2.
3.
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an...  相似文献   
4.
A masked lithium homoenolate, generated by tellurium/lithium exchange, was reacted with epoxides. The lithium compound was also converted into other organometallics such as Grignard, and cuprates and the reactivity of those organometallics with epoxides was evaluated. The same building block was employed in the synthesis of (+/−)-frontalin.  相似文献   
5.
6.
Summary Studies performed by the Brazilian Nuclear Corporation (NUCLEBRAS), in collaboration with the Geological Survey Company of Brazil (CPRM), identified high levels of natural uranium in the districts of Pedra and Venturosa, in the rural region of the state of Pernambuco (PE) - Brazil, where the maximum value found in rocks was 22,000 mg.  相似文献   
7.
8.
 A simple and direct spectrofluorimetric method has been developed for the determination of aluminum using alizarin red PS (1,2,4-trihydroxy 9,10-anthraquinone-3-sulfonic acid). The method is based on the strong fluorescence (480/564 nm) of Al3+ and alizarin red. Experimental parameters such as pH, concentration of the ligand, ionic strength of the solution, reaction time and temperature were optimized in order to maximize the analytical signal. Interferences of several ions (anions and cations) were studied and evaluated. The linear range of the method extends from 3 to 100 μg L−1. Limit of detection (3sb) was 0.9 μg L−1. The method was tested with a silicate certified reference material. Interferences were eliminated by a liquid extraction with cupferron. Author for correspondence. E-mail: aucelior@rdc.puc-rio.br Received September 10, 2002; accepted January 15, 2003 Published online May 5, 2003  相似文献   
9.
In this paper we highlighted the synthesis, characterization, and practical exploitation of different types of polyphosphazenes substituted with fluorinated groups. There are several ways in which fluorine atoms can be inserted into polyphosphazenes, all of which leading to different polymers showing a wide range of characteristics. In general it is true that the insertion of fluorine atoms into phosphazene macromolecules leads to an enhancement of the thermal stability, flame resistance, low-temperature elastomericity, and chemical inertness of the phosphazenes obtained. The contribution of Italian research groups to the preparation and exploitation of organic commercial macromolecules grafted onto fluorinated polyphosphazenes is also reviewed.  相似文献   
10.
By combining frontal polymerization and radical‐induced cationic polymerization, it was possible to cure thick samples of an epoxy monomer bleached by UV light. The effect of the relative amounts of cationic photoinitiator and radical initiator was thoroughly investigated and was related to the front's velocity and its maximum temperature. The materials obtained were characterized by quantitative conversion also in the deeper layers, not reached by UV light. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2066–2072, 2004  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