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   175篇
  免费   1篇
化学工业   57篇
金属工艺   11篇
机械仪表   3篇
建筑科学   5篇
矿业工程   3篇
轻工业   2篇
水利工程   14篇
石油天然气   16篇
无线电   10篇
一般工业技术   14篇
冶金工业   18篇
原子能技术   18篇
自动化技术   5篇
  2022年   17篇
  2021年   12篇
  2019年   3篇
  2018年   3篇
  2017年   7篇
  2016年   8篇
  2014年   6篇
  2013年   5篇
  2012年   3篇
  2011年   2篇
  2010年   2篇
  2009年   3篇
  2007年   2篇
  2006年   2篇
  2005年   4篇
  2003年   6篇
  2002年   3篇
  1998年   2篇
  1997年   7篇
  1996年   2篇
  1995年   3篇
  1992年   2篇
  1991年   1篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1982年   4篇
  1981年   2篇
  1980年   2篇
  1979年   2篇
  1978年   5篇
  1977年   3篇
  1976年   8篇
  1975年   5篇
  1974年   3篇
  1973年   2篇
  1971年   1篇
  1970年   1篇
  1969年   4篇
  1967年   4篇
  1966年   4篇
  1965年   3篇
  1964年   1篇
  1959年   1篇
  1958年   1篇
排序方式: 共有176条查询结果,搜索用时 500 毫秒
1.
Chronic stress is a combination of nonspecific adaptive reactions of the body to the influence of various adverse stress factors which disrupt its homeostasis, and it is also a corresponding state of the organism’s nervous system (or the body in general). We hypothesized that chronic stress may be one of the causes occurence of several molecular and cellular types of stress. We analyzed literary sources and considered most of these types of stress in our review article. We examined genes and mutations of nuclear and mitochondrial genomes and also molecular variants which lead to various types of stress. The end result of chronic stress can be metabolic disturbance in humans and animals, leading to accumulation of reactive oxygen species (ROS), oxidative stress, energy deficiency in cells (due to a decrease in ATP synthesis) and mitochondrial dysfunction. These changes can last for the lifetime and lead to severe pathologies, including neurodegenerative diseases and atherosclerosis. The analysis of literature allowed us to conclude that under the influence of chronic stress, metabolism in the human body can be disrupted, mutations of the mitochondrial and nuclear genome and dysfunction of cells and their compartments can occur. As a result of these processes, oxidative, genotoxic, and cellular stress can occur. Therefore, chronic stress can be one of the causes forthe occurrence and development of neurodegenerative diseases and atherosclerosis. In particular, chronic stress can play a large role in the occurrence and development of oxidative, genotoxic, and cellular types of stress.  相似文献   
2.
A method for fabricating single crystal blades that combines the techniques of seed crystals and selection is suggested. The method realizes the advantages of both techniques, i.e., the high structural perfection and the possibility of fabricating single crystals with specified spatial orientation. Metallographic and x-ray diffraction analyses are used to study the processes of nucleation of the single crystal structure of blade castings fabricated from high-temperature nickel alloys by the method of selection and seed crystals. A commercial process for fabricating cast single crystal turbine blades by the new method is suggested.  相似文献   
3.
This article considers a discrete sequential multilevel automated system for recording electron-diffraction patterns. A comparative analysis is presented, along with experimental results that make it possible to evaluate the effectiveness of the technical decisions on which the device is based. The general design of the system is presented. Translated from Izmeritel'naya Tekhnika No. 5, pp. 16–18, May, 1996.  相似文献   
4.
Thermoresponsive PEG-based (PEG stands polyethylene glycol) polymers are unique for use in medicine because of their low toxicity, good biocompatibility and biodegradability, but usually more hydrophobic and more toxic comonomers are used to adjust lower critical solution temperature (LCST). A convenient way to overcome this problem and to finely tune LCST is to use alkoxy oligo(ethylene glycol)- or alkoxy oligo(propylene glycol) (meth)acrylates as starting comonomers. Here we report on the conditions for the simple and affordable synthesis of methoxy oligo(propylene glycol) (meth)acrylate- and methoxy oligo(propylene glycol)-block-oligo(ethylene glycol) (meth)acrylate-based macromonomers with high yields (80%–98.7%) by the acid-catalyzed esterification of (meth)acrylic acid with alkoxy oligo(alkylene glycols) containing oligo(ethylene glycol) (OEG) and/or oligo(propylene glycol) (OPG) blocks. p-Toluene sulphonic acid (pTSA), alkyl(C12–C14)benzene sulfonic acid (ABSA) and H2SO4 were used as catalysts. It has been shown that pTSA and ABSA are practically the same in catalytic activity and are superior to sulfuric acid. The reaction orders with respect to catalyst was found to be close to 1 in all cases. It has been shown that the reaction is actually insensitive to the lengths of OEG and OPG blocks, as well as to the structure of the terminal alkyl group, while the esterification of acrylic acid (AA) proceeds much faster compared to methacrylic acid (MAA) one under the same conditions. The influence of temperature on the equilibrium conversions of alcohols was determined, which were found to be 89%–93% for the esterification of AA and 61%–86% for MAA in the temperature range of 60–120°C. A further increase in conversion was achieved by introducing an azeotropic agent (toluene), its optimal concentration was found to be 10%–15%.  相似文献   
5.
The structure and conductivity of hybrid nanocomposite poly(p-xylylene) films containing iron nanoparticles are studied. The films are obtained by the method of polymerization on a surface from the gas phase, and the concentration of the filler is 4 and 11 vol %. According to the analysis of microphotographs of nanostructures obtained by transmission electron microscopy, the particles are distributed evenly (with a size in the nanometer range and a rather narrow distribution). Studies of the frequency dependence of conductivity show that the transport of the charge carriers is realized by the hopping mechanism with a jump length of ~3.5 nm.  相似文献   
6.
This is the continuation of the paper devoted to the study of airspace sectorization problems for air traffic areas as one of airspace design problems [1]. Algorithmic and technical aspects of solution of the problem of the first stage of airspace sectorization of a district center of air traffic management based on genetic optimization procedures are considered. Results of simulation of operation of optimization procedures are analyzed.  相似文献   
7.
The results of investigations of the leading operation of a nonaqueous technology for reprocessing fuel elements from nuclear reactors — dissolution of fuel claddings in a zinc-based melt — are presented. Data obtained in experiments on simulators and samples of irradiated fuel elements in standard BOR-60 and SM-2 packages with different burnup and holding time are presented. In the experiments, the metallic melt was separated from the fuel by filtering through a mesh and regenerated by vacuum distillation for reuse. The uranium and plutonium extraction was 99.99%. The behavior of individual radionuclides is described. __________ Translated from Atomnaya Energiya, Vol. 99, No. 4, pp. 273–276, October, 2005.  相似文献   
8.
In atherosclerosis; blood low-density lipoproteins (LDL) are subjected to multiple enzymatic and non-enzymatic modifications that increase their atherogenicity and induce immunogenicity. Modified LDL are capable of inducing vascular inflammation through activation of innate immunity; thus, contributing to the progression of atherogenesis. The immunogenicity of modified LDL results in induction of self-antibodies specific to a certain type of modified LDL. The antibodies react with modified LDL forming circulating immune complexes. Circulating immune complexes exhibit prominent immunomodulatory properties that influence atherosclerotic inflammation. Compared to freely circulating modified LDL; modified LDL associated with the immune complexes have a more robust atherogenic and proinflammatory potential. Various lipid components of the immune complexes may serve not only as diagnostic but also as essential predictive markers of cardiovascular events in atherosclerosis. Accumulating evidence indicates that LDL-containing immune complexes can also serve as biomarker for macrovascular disease in type 1 diabetes.  相似文献   
9.
A method for registration of the coherent scattering reactor antineutrino on nuclei using a three-section low-background proportional counter was proposed. It is planned to use argon and xenon as the working substance. As has been shown on a test bench, pulse shape discrimination can effectively suppress the background from electromagnetic interference and microphonic effects in the energy range from 20 to 100 eV where the effect of coherent scattering of neutrinos on nuclei is expected with a factor of about 103. Problems of the neutron background generated by cosmic-ray muons are analyzed. The scheme of the experimental setup is presented.  相似文献   
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