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   5233篇
  免费   43篇
  国内免费   9篇
化学   2494篇
晶体学   129篇
力学   167篇
综合类   3篇
数学   616篇
物理学   1876篇
  2019年   46篇
  2018年   67篇
  2017年   69篇
  2016年   75篇
  2015年   53篇
  2014年   86篇
  2013年   214篇
  2012年   163篇
  2011年   197篇
  2010年   115篇
  2009年   150篇
  2008年   181篇
  2007年   194篇
  2006年   156篇
  2005年   137篇
  2004年   145篇
  2003年   116篇
  2002年   132篇
  2001年   104篇
  2000年   99篇
  1999年   91篇
  1998年   55篇
  1997年   63篇
  1996年   67篇
  1995年   60篇
  1994年   69篇
  1993年   55篇
  1992年   74篇
  1991年   73篇
  1990年   78篇
  1989年   58篇
  1988年   43篇
  1987年   62篇
  1986年   63篇
  1985年   62篇
  1984年   83篇
  1983年   88篇
  1982年   82篇
  1981年   88篇
  1980年   99篇
  1979年   71篇
  1978年   91篇
  1977年   96篇
  1976年   70篇
  1975年   54篇
  1974年   49篇
  1973年   45篇
  1972年   37篇
  1970年   35篇
  1969年   35篇
排序方式: 共有5285条查询结果,搜索用时 10 毫秒
101.
The temperature shift of the neutrino mass in a constant magnetic field is calculated within the framework of the Weinberg-Salam model. The cases of weak field and low and high temperatures are considered. The contribution to the anomalous magnetic moment of the neutrino is determined. The imaginary component of the mass correction describing the reaction of decay and W-boson formation is analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 3–6, December, 1987.  相似文献   
102.
103.
Methods for the preparation of composite ion-exchange membranes from polymer (polyvinylidene fluoride (PVDF), ultrahigh molecular weight polyethylene (UHMWPE), and polypropylene (PP)) matrices were considered. Polystyrene (PS) was introduced in the matrices by thermal polymerization of the monomer followed by sulfonation of the implant. The fundamentals of membrane synthesis from industrial polytetrafluoroethylene (PTFE, Teflon F-4) films by thermal polymerization of styrene in a film stretched in a monomer solution followed by sulfonation of incorporated PS were described. The literature on radiation- chemical synthesis of composite ion-exchange membranes based on polymer matrices with embedded polystyrene and its subsequent sulfonation was analyzed. Some problems of the kinetics and mechanism of thermal implantation of PS into various polymer matrices under different conditions were discussed. The physicochemical characteristics, structure, and transport properties of the membranes synthesized by thermal implantation of PS were reported. The obtained membranes were tested in low-temperature fuel cells.  相似文献   
104.
105.
From the feeding of young plants of Strychnos nux-vomica with [14C]-1-and [14C]-2-acetate it could be deduced that the C-atoms 22 and 23 were derived from acetate. [14C]-2-mevalonate, [14C]-2-geraniol and [14C]-2-geranyl pyrophosphate were also incorporated into strychnine. The distribution of radioactivity in the «mevalonate-strychnine» was in agreement with the monoterpenoid hypothesis. Feeding experiments especially with [14C]-tryptophane showed that the main production centre of the alkaloid lay in the roots and that only a small part of it was carried to the leaves. Tritium labelled WIELAND GUMLICH aldehyde as well as N(a)-[14C]-1-acetyl WIELAND GUMLICH aldehyde were not converted into strychnine by S. nux-vomica.  相似文献   
106.
The electroreduction of camphorquinone in DMF, at mercury electrodes, was investigated by a variety of techniques. In DMF, in the absence of proton donor, camphorquinone exhibits two one-electron waves: the first, a one-electron reversible wave to be due to a reversible charge transfer without a coupled chemical reaction. After the first charge transfer, the semidione anion radical is reduced to the dianion. The irreversibility of the second wave derives from a fast irreversible protonation of the dianion. A wide variety of changes in behaviour is observed in the reduction of camphorquinone as increasing amounts of benzoic acid are added: a new two-electron irreversible wave appears at a potential less negative than the original wave. A proton donor to substrate ratio of 2 is required to completely suppress the two original waves. A mechanism for the electroreduction of camphorquinone is proposed and discussed on the basis that the prewave current is controlled by the diffusion of the undissociated acid species and that the undissociated acid, rather than the solvated proton, takes part in the protonation, prior to the charge transfer.  相似文献   
107.
Series of variously sustituted amides of 2-sulfonamido-4,5-dimethoxyphenylacetic acid have been prepared. The reaction of diethylamine, piperidine, morpholine and bis(2-chloroethyl)amine with carbo-methoxymethyl-3,4-dimethoxybenzenesulfonyl chloride produced the corresponding sulfonamido derivatives. Acid hydrolysis of the latter and action of thionyl chloride gave the chlorocarboxymethyl-benzenesulfonamides. The acid chlorides of the sulfonamides were transformed to the 2-carboxamido-bis(2-chloroethyl)methylbenzenesulfonamides with bis(2-chloroethyl)amine. These agents were tested in L-1210 and P-388 leukemias and were found not to possess antitumor activity in these two transplantable tumor lines.  相似文献   
108.
109.
110.
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