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   385篇
  免费   9篇
  国内免费   4篇
化学   181篇
晶体学   3篇
力学   13篇
数学   23篇
物理学   178篇
  2023年   3篇
  2022年   8篇
  2021年   7篇
  2020年   8篇
  2019年   10篇
  2018年   6篇
  2017年   9篇
  2016年   12篇
  2015年   10篇
  2014年   15篇
  2013年   33篇
  2012年   16篇
  2011年   22篇
  2010年   14篇
  2009年   13篇
  2008年   17篇
  2007年   10篇
  2006年   7篇
  2005年   14篇
  2004年   13篇
  2002年   8篇
  2001年   2篇
  1998年   6篇
  1996年   6篇
  1995年   7篇
  1994年   9篇
  1993年   8篇
  1992年   15篇
  1991年   5篇
  1990年   8篇
  1989年   4篇
  1988年   3篇
  1987年   3篇
  1986年   6篇
  1985年   4篇
  1984年   3篇
  1983年   3篇
  1982年   4篇
  1981年   3篇
  1980年   5篇
  1979年   2篇
  1978年   2篇
  1977年   5篇
  1976年   3篇
  1975年   4篇
  1973年   4篇
  1972年   4篇
  1963年   2篇
  1962年   2篇
  1955年   2篇
排序方式: 共有398条查询结果,搜索用时 15 毫秒
1.
Development of a 100 MeV CW proton LINAC has been planned at CAT. This LINAC will be needing CW rf power in the frequency ranges of 350 MHz and 700 MHz for its RFQ and DTL/CCDTL/SFDTL structures respectively. The power to the accelerating structures will be produced by either 1 MW CW or 250 kW CW klystrons/inductive output tubes (HOM IOTs). The power needed by respective feed points in the structure is max. 250 kW which will be powered by splitting the power from 1 MW klystron/klystrode into four channels by using a wave-guide system. In case of using 250 kW tubes the power to the structures will be provided directly from each tube. Two types of wave-guide transmission system have been considered, viz, WR 2300 for 350 MHz rf needs and WR 1500 for 700 MHz rf needs. The typical wave-guide system has been designed using the 1 MW CW klystron followed by wave-guide filter, dual directional coupler, high-power circulator, three 3 dB magic TEE power dividers to split the main channel into four equal channels of 250 kW each. Each individual channel has dual directional couplers, flexible wave-guide sections and high power ceramic vacuum window. The circulator and each power divider is terminated into the isolated ports by high power CW loads. Out of the four channels three channels have phase shifters. Present paper describes the technological aspects and design specifications-considerations for these stringent requirements.  相似文献   
2.
In the present paper we derive three interesting expressions for the composition of two most general fractional integral oprators whose kernels involve the product of a general class of polynomials and a multivariableH-function. By suitably specializing the coefficients and the parameters in these functions we can get a large number of (new and known) interesting expressions for the composition of fractional integral operators involving classical orthogonal polynomials and simpler special functions (involving one or more variables) which occur rather frequently in problems of mathematical physics. We have mentioned here two special cases of the first composition formula. The first involves product of a general class of polynomials and the Fox’sH-functions and is of interest in itself. The findings of Buschman [1] and Erdélyi [4] follow as simple special cases of this composition formula. The second special case involves product of the Jacobi polynomials, the Hermite polynomials and the product of two multivariableH-functions. The present study unifies and extends a large number of results lying scattered in the lierature. Its findings are general and deep.  相似文献   
3.
4.
Two iodometric procedures have been described for the microdetermination of certain organic acids which can be adopted for evaluating 0.03–0.1 meq of these acids. These methods consist of treating the acid sample with an excess of neutral potassium iodide and iodate. In the indirect method the iodate used up is measured whereas the direct procedure is based on the titration of the liberated iodine. The latter procedure has been applied to determine acids in a water-alcohol medium also. The effect of various factors influencing the stoichiometry of the reactions involved has also been studied.  相似文献   
5.
Summary A simple and rapid field Chromatographic method for the determination of thorium in ppm quantities in rocks, soils and low grade ores using paper strip chromatography is described. An aliquot of an hydrochloric acid solution of the sample is taken on a special paper (Chromatographic paper of C.R.L./l grade) and the paper is then placed into a beaker containing the solvent mixture consisting of methyl alcohol, acetone, 2-thenoyl trifluoroacetone and hydrochloric acid in the ratio 12 ml6 ml0.04 g2 ml (13) respectively.A saturated alcoholic solution of alizarin atph 2.8-2.4 is used as developing reagent.This method is applicable to samples containing from 0.2 ppm to 1000 ppm of thorium.
Zusammenfassung Eine einfache und schnell durchführbare Feldmethode zur papierchromatographischen Bestimmung von ppm-Mengen Thorium in Gesteinen, Böden und Erzen niederen Gehaltes wird beschrieben. Hierbei wird ein Anteil der salzsauren Probelösung auf ein Spezialpapier (C.R.L./ 1 grade) aufgebracht und dieses in einem Becherglas mit einem Gemisch aus Methanol, Aceton, 2-Thenoxyltrifluoraceton und Salzsäure (12 ml 6 ml0,04 g2 ml [13]) chromatographiert. Zur Entwicklung dient eine gesättigte alkoholische Alizarinlösung (ph 2,8-2,4). 0,2–1000 ppm Thorium können nach diesen Verfahren bestimmt werden.
  相似文献   
6.
7.
8.
9.
10.
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