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   314篇
  免费   23篇
  国内免费   1篇
化学工业   84篇
金属工艺   6篇
机械仪表   15篇
建筑科学   15篇
能源动力   8篇
轻工业   102篇
水利工程   2篇
石油天然气   3篇
无线电   5篇
一般工业技术   44篇
冶金工业   20篇
原子能技术   1篇
自动化技术   33篇
  2024年   3篇
  2023年   4篇
  2022年   13篇
  2021年   15篇
  2020年   5篇
  2019年   12篇
  2018年   18篇
  2017年   9篇
  2016年   12篇
  2015年   11篇
  2014年   10篇
  2013年   28篇
  2012年   18篇
  2011年   26篇
  2010年   13篇
  2009年   20篇
  2008年   15篇
  2007年   19篇
  2006年   8篇
  2005年   9篇
  2004年   9篇
  2003年   7篇
  2002年   6篇
  2001年   4篇
  2000年   1篇
  1999年   4篇
  1998年   4篇
  1997年   7篇
  1996年   6篇
  1995年   4篇
  1994年   1篇
  1993年   1篇
  1991年   1篇
  1990年   2篇
  1988年   2篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
  1974年   3篇
  1973年   1篇
排序方式: 共有338条查询结果,搜索用时 31 毫秒
1.
2.
3.
A man had a quarrel with his wife. Suddenly he collapsed and became cyanotic. The woman supposed him to be dead. Because she was afraid of familiar requital, she opened the gas-cock of the cooking-range to pretend a suicide; methane emitted. The autopsy revealed a fresh cardiac infarction. Postmortem chemical analysis established methane in the blood. The question was, whether the methane had any importance for the death. By experimental inhalation of a methane-air-mixture (3%) we could expose, that the methane concentration in postmortem blood didn't have any relevance for the death.  相似文献   
4.
Trimipramine (TRI), which shows a clinical antidepressant activity, is chemically related to imipramine but does not inhibit the reuptake of noradrenaline and 5-hydroxytryptamine, nor does it induce beta-adrenergic down-regulation. The mechanism of its antidepressant activity is still unknown. The aim of the present study was to find out whether TRI given repeatedly was able to induce adaptive changes in the dopaminergic and alpha1-adrenergic systems, demonstrated by us previously for various antidepressants. TRI was given to male Wistar rats and male Albino Swiss mice perorally twice daily for 14 days. In the acute experiment TRI (given i.p.) does not antagonize the reserpine hypothermia in mice and does not potentiate the 5-hydroxytryptophan head twitches in rats. TRI given repeatedly to rats increases the locomotor hyperactivity induced by d-amphetamine, quinpirole and (+)-7-hydroxy-dipropyloaminotetralin (dopamine D2 and D3 effects). The stereotypies induced by d-amphetamine or apomorphine are not potentiated by TRI. It increases the behaviour stimulation evoked by phenylephrine (given intraventricularly) in rats, evaluated in the open field test as well as the aggressiveness evoked by clonidine in mice, both these effects being mediated by an alpha1-adrenergic receptor. It may be concluded that, like other tricyclic antidepressants studied previously, TRI given repeatedly increases the responsiveness of brain dopamine D2 and D3 (locomotor activity but not stereotypy) as well as alpha1-adrenergic receptors to their agonists. A question arises whether the reuptake inhibition is of any importance to the adaptive changes induced by repeated antidepressants, suggested to be responsible for the antidepressant activity.  相似文献   
5.
6.
Depending on the calcium:phosphorus molar ratio of the initial precipitates determined by precipitation conditions (calcium:phosphorus molar ratio of reactants and pH of reaction environment), after sintering at 1250°C, monophase, biphase, or triphase ceramics consisting of hydroxyapatite, β-tricalcium phosphate, α-tricalcium phosphate, and calcium oxide were obtained. The phase composition and properties—i.e., density, shrinkage, hardness, bending strength, and roughness—of the fractured surfaces of the isostatically re-pressed sinters were determined.  相似文献   
7.
This work demonstrates the applicability of the free-radical addition of ω-functional mercaptans onto 1,2-polybutadienes as a modular synthetic pathway toward a toolbox of diverse functional block copolymers. Functional groups included, for instance electrolytes (carboxylic acid and amine), l-amino acid, and fluorocarbon. The number of functional groups attached to the polymer was lower than that of double bonds reacted (degree of functionalization=50–85%, typically 70–80%) due to cyclization of two neighboring units, but the narrow molecular-weight distribution of the parent (co)polymer was always maintained.  相似文献   
8.
Knowledge of the solution of transport equations allows one to determine parameters which are needed to evaluate the protective properties of organic coatings, particularly the penetration of water inside the coatings. The form of equations representing the processes of transport and their usefulness should be verified by experimental results. The mathematical aspect of the problem is studied in the framework of the theory of partial differential equations. Various methods of solving the equations, the problem of their univocal character, their regularity and properties are considered. The form of a particular solution depends on the imposed problem. The method of determination of the depth of water penetration inside the organic coatings is based upon the solutions of the transport equation. The use of Boltzmann transformation allows the concentration profiles dependent on additional parameters (e.g., temperature) to be represented. The solutions of the diffusion equation for various limiting conditions as well as the methods of determination of diffusion coefficient are presented. The method of evaluation of the depth of medium penetration inside the protective coating in the case of a non-stationary process is described. The use of Boltzmann transformation made it easier to analyse the solution of the diffusion equation. The dependence of the water diffusion coefficient in epoxide-phenol lacquer coatings on temperature was determined and the applicability of Arrhenius' law was found in the temperature range from 303 to 363 K. Knowledge of the diffusion coefficients enabled the time of water penetration inside organic coatings to be determined.  相似文献   
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