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   647849篇
  免费   8131篇
  国内免费   1405篇
电工技术   11256篇
综合类   2765篇
化学工业   100916篇
金属工艺   27863篇
机械仪表   21475篇
建筑科学   14829篇
矿业工程   4865篇
能源动力   15606篇
轻工业   49396篇
水利工程   8133篇
石油天然气   15313篇
武器工业   40篇
无线电   69195篇
一般工业技术   131678篇
冶金工业   98675篇
原子能技术   14914篇
自动化技术   70466篇
  2021年   5540篇
  2020年   4069篇
  2019年   5327篇
  2018年   22883篇
  2017年   22011篇
  2016年   19360篇
  2015年   6660篇
  2014年   10573篇
  2013年   26538篇
  2012年   18846篇
  2011年   30051篇
  2010年   24810篇
  2009年   24126篇
  2008年   25594篇
  2007年   26148篇
  2006年   16533篇
  2005年   15982篇
  2004年   15141篇
  2003年   14879篇
  2002年   13841篇
  2001年   13007篇
  2000年   12543篇
  1999年   12129篇
  1998年   27772篇
  1997年   20144篇
  1996年   15719篇
  1995年   12074篇
  1994年   10913篇
  1993年   10671篇
  1992年   8404篇
  1991年   8160篇
  1990年   8028篇
  1989年   7809篇
  1988年   7529篇
  1987年   6783篇
  1986年   6582篇
  1985年   7450篇
  1984年   6744篇
  1983年   6496篇
  1982年   5812篇
  1981年   5926篇
  1980年   5664篇
  1979年   5784篇
  1978年   5699篇
  1977年   6216篇
  1976年   7714篇
  1975年   5137篇
  1974年   4918篇
  1973年   5003篇
  1972年   4293篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
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   
62.
Kirovskaya  I. A.  Filatova  T. N.  Nor  P. E. 《Semiconductors》2021,55(2):228-233
Semiconductors - According to developed methods, in the fields of the mutual solubility of initial binary compounds (InP, InSb, and CdS), solid solutions of the InP–CdS and InSb–CdS...  相似文献   
63.
Chemical and Petroleum Engineering - The processes of separation of impurities of particles of different sizes are analyzed under conditions of irregularity of structural and kinematic parameters...  相似文献   
64.
Herein, we report the photosensing property of CdS thin films. CdS thin films were coated onto glass substrates via a spray pyrolysis method using different spray pressures. Prepared films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical and photoluminescence spectroscopy. XRD analysis demonstrated the growth of crystalline CdS films with crystallite sizes varying from 26 to 29 nm depending on the pressure. The SEM and EDAX analyses revealed nearly-stoichiometric CdS films with smooth surfaces and slight variation in grain morphology due to pressure changes. Optical measurements showed a direct bandgap varying from 2.37 eV to 2.42 eV due to pressure changes. A photodetector was also fabricated using the grown CdS films; the fabricated photodetector exhibited good performance depending on the spray pressure. A spray pressure of 1.5 GPa resulted in high photoresponsivity and external quantum efficiency.  相似文献   
65.
Golubev  N. V.  Ignat’eva  E. S.  Maurus  A. A.  Ziyatdinova  M. Z.  Lopatina  E. V.  Lorenzi  R.  Paleari  A.  Sigaev  V. N. 《Glass and Ceramics》2021,77(11-12):415-418
Glass and Ceramics - The influence of Al2O3 as an additive and the heat-treatment regime on the luminescence spectra of gallate glass-ceramics was investigated. It is shown that its luminescence...  相似文献   
66.
Russian Engineering Research - Models based on regression analysis for predicting the operational efficiency of high-pressure roller crushers are considered. A systematized and structured...  相似文献   
67.
Journal of Machinery Manufacture and Reliability - The problem of calculating the reliability and fatigue life of machine parts by the fatigue failure under random changes in the actual and limit...  相似文献   
68.
69.
In this study, amaranth flour was used as an ingredient to prepare gluten-free cookies. The production process and attributes of amaranth cookies were characterised, and the potential use of amaranth flour as a functional ingredient was analysed. Cookies exhibited a non-uniform reddish brown colour and a cookie factor ratio of 4.5 ± 0.6. Storage studies indicated that after 3 weeks at room temperature cookies presented slight variations in the texture. Simulated gastrointestinal digestion of this product was able to release peptides capable of exerting potential antithrombotic and antihypertensive activities, IC50 values of 0.22 ± 0.04 and 0.23 ± 0.03 mg mL−1 protein, respectively. This work demonstrates for the first time that food made with amaranth flour exerts potential antithrombotic and antihypertensive activity. In conclusion, these amaranth cookies could be an alternative way of incorporating potentially health beneficial products for people who choose a conscious diet, including coeliac or vegan consumers.  相似文献   
70.
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