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   355篇
  免费   11篇
  国内免费   1篇
化学工业   121篇
金属工艺   10篇
机械仪表   9篇
建筑科学   10篇
能源动力   3篇
轻工业   11篇
水利工程   2篇
石油天然气   27篇
无线电   31篇
一般工业技术   60篇
冶金工业   54篇
原子能技术   6篇
自动化技术   23篇
  2022年   21篇
  2021年   28篇
  2020年   5篇
  2019年   7篇
  2018年   16篇
  2017年   8篇
  2016年   17篇
  2015年   9篇
  2014年   9篇
  2013年   23篇
  2012年   13篇
  2011年   15篇
  2010年   11篇
  2009年   16篇
  2008年   7篇
  2007年   20篇
  2006年   14篇
  2005年   7篇
  2004年   7篇
  2003年   7篇
  2002年   4篇
  2001年   4篇
  2000年   2篇
  1999年   3篇
  1998年   12篇
  1997年   9篇
  1996年   3篇
  1994年   2篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1987年   3篇
  1986年   4篇
  1984年   4篇
  1980年   7篇
  1979年   3篇
  1978年   3篇
  1977年   2篇
  1976年   8篇
  1975年   1篇
  1974年   8篇
  1973年   2篇
  1972年   3篇
  1971年   1篇
  1970年   1篇
  1969年   1篇
  1968年   1篇
  1967年   1篇
  1966年   1篇
  1964年   1篇
排序方式: 共有367条查询结果,搜索用时 15 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 microscopic calculation of the conductivity in the integer quantum Hall effect (IQHE) mode is carried out. The precision of quantization is analyzed for finite-size samples. The precision of quantization shows a power-law dependence on the sample size. A new scaling parameter describing this dependence is introduced. It is also demonstrated that the precision of quantization linearly depends on the ratio between the amplitude of the disorder potential and the cyclotron energy. The data obtained are compared with the results of magnetotransport measurements in mesoscopic samples.  相似文献   
3.
The dynamics and present state of the radioactive contamination with 137Cs of littoral soil of Lake Kozhanovskoe and Lake Svyatoe on the Besed’ River are presented. The parameters of the vertical migration of 137Cs in soil-the rate of directional transfer with soil moisture, the diffusion coefficient, and the average velocity of vertical migration-are estimated by comparing the experimental and model distributions of 137Cs content over soil depth. It is shown that at the present time the two 5-cm layer of soil can contain 20–90% 137Cs depending on the type of soil and landscape. The average values of the diffusion coefficient, the rate of directional transfer, and the vertical migration velocity for 12-, 13-, and 20-year periods after the Chernobyl accident are 0.1–2.8 cm2/yr, 0.1–0.3 cm/yr, and 0.1–0.8 cm/yr, respectively. __________ Translated from Atomnaya énergiya, Vol. 102, No. 5, pp. 306–311, May, 2007.  相似文献   
4.
Although filial therapy has traditionally been viewed as suitable for children of diverse cultures, there is limited research to support this perspective. This qualitative case study examined the perceived effectiveness of filial therapy for a Jamaican mother and the perceived effect on the mother-child relationship. Findings indicate that some aspects of filial therapy are congruent with the parenting practices and values of this Jamaican mother. The mother reported an increase in empathy, a heightened awareness of her child's needs, and a stronger relationship with her child. She expressed some difficulty with limit setting and tracking skills taught as part of the model. Future research directions include further examination of the compatibility of filial therapy with other Jamaican parents and the effectiveness of group filial therapy with Jamaican parents or other parents of Caribbean descent. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
5.
Refractories and Industrial Ceramics - The article presents an overview of the methods of processing slag from Waelz process, and various approaches employed by scientists globally, aimed at...  相似文献   
6.
The size of the inner water cavity of reversed micelles formedin a triple system ‘water-surfactant-organic solvent’can be widely varied by changing the degree of surfactant hydration.This gives grounds to use reversed micelles as matrix microreactorsfor the design of supramolecular complexes of proteins. Usingultracentrifugation analysis, it has been demonstrated thatthe oligomeric composition of various enzymes (ketoglutaratedehydrogenase, alkaline phosphatase, lactic dehydrogenase, glyceraldehyde-3-phosphatedehydrogenase) solubilized in reversed micelles of Aerosol OT[sodium bis(2-ethylehexyl)sulfosuccinate] in octane changesupon variation of the degree of hydration. An oligomeric complexforms under conditions when the radius of the micelle innercavity is big enough to incorporate this complex as a whole.At lower degrees of hydration the micelles ‘uncouple’such complexes to their components. The catalytic propertiesof various oligomeric complexes have been studied. Possibilitiesof using reversed micelles for the separation of subunits ofoligomeric enzymes under non-denaturating conditions have beendemonstrated. In particular, the isolated subunits of alkalinephosphatase, lactic dehydrogenase and glyceralde-hyde-3-phosphatedehydrogenase have been found to be active in Aerosol OT reversedmicelles. The dependences of the catalytic activity of oligomericenzymes represent saw-like curves. The maxima of the catalyticactivity observed at these curves relate to the functioningof various oligomeric forms of an enzyme. The radii of the micelleinner cavity under conditions when these maxima are observedcorrelate with the linear dimensions of the enzyme oligomericforms. Correlation of the position of a maximum with the shapeof an oligomeric complex is discussed.  相似文献   
7.
A method of controlling anchoring energy of surface interaction of liquid crystal photoaligning substances is considered to enhance the liquid crystal display performances. An important parameter of the dye's molecular structure that determines the ratio of polar and azimuthal anchoring energy is the ability to form dimers. The values of dimerization thermodynamic potentials have been found. The probability of the formation of dye molecules dimers is evaluated. The bonds conjugation transfer via intermolecular hydrogen bond is revealed, and anisotropy of polarizability of the hydrogen bond is evaluated. The effect of dimerization on polar and azimuthal anchoring energy of liquid crystal — azo dye system — is shown.  相似文献   
8.
This paper addresses the problem of integration of reputation management mechanisms into data look-up and routing processes to cope with some specific security problems in peer-to-peer (P2P) networks based on Distributed Hash Tables (DHT). The goal is to find a mode for “good” peers to cooperate in order to withstand malicious activity of single malevolent peers and their collusions as well.We start from consideration of individual instruments for reputation evaluation that every single peer should be provided with to autonomously define the level of its own trust towards others. We also propose a possible scenario of integration of some existing reputation management techniques and routing mechanisms in a P2P network based on the popular Kademlia algorithm. Then, we present an interaction algorithm that allows peers to obtain the global trust value for each single node through exchanging opinions in the form of local trust values independently calculated by every peer with other members of the community. Such collaboration between peers is indispensable to cope with malicious activity of inconsistent nature specific to DHT-based environment. To render the algorithm resilient to the presence of malicious participants we propose to apply solutions for Byzantine Agreement to exchange opinions among peers. We also provide mathematical evaluations concerning the complexity and computational costs of the proposed algorithm that evidence apparent improvements over the previous one.  相似文献   
9.
Communication and reputation are essential for the positioning of an organization, which is based on communications theory, management sociology, corporate management, and public relations. Corporate culture and visual identity are also important for any organization; they not only help develop an integrated image of the organization but also contribute to developing its successful positioning strategy. We began our research with the analysis stage, in which we elicited the practices of both the internal and external communications of the organization studied. We used such methods as communication and reputation audits with a questionnaire survey, focus groups, the semantic differential method, and the projective method. The analysis stage of the research produced results that helped us adjust the positioning strategy of the organization by taking into account its individual characteristics and the features of its target publics and its target markets.  相似文献   
10.
The Foundational Model of Anatomy (FMA) represents the result of manual and disciplined modeling of the structural organization of the human body. It is a tremendous resource in bioinformatics that facilitates sharing of information among applications that use anatomy knowledge. The FMA was developed in Protégé and the Protégé frames language is the canonical representation language for the FMA. We present a translation of the original Protégé frame representation of the FMA into OWL. Our effort is complementary to the earlier efforts to represent FMA in OWL and is focused on two main goals: (1) representing only the information that is explicitly present in the frames representation of the FMA or that can be directly inferred from the semantics of Protégé frames; (2) representing all the information that is present in the frames representation of the FMA, thus producing an OWL representation for the complete FMA. Our complete representation of the FMA in OWL consists of two components: an OWL DL component that contains the FMA constructs that are compatible with OWL DL; and an OWL Full component that imports the OWL DL component and adds the FMA constructs that OWL DL does not allow.  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