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   566863篇
  免费   7357篇
  国内免费   992篇
电工技术   10523篇
综合类   484篇
化学工业   88892篇
金属工艺   23446篇
机械仪表   18559篇
建筑科学   12691篇
矿业工程   4315篇
能源动力   14740篇
轻工业   45990篇
水利工程   6963篇
石油天然气   14918篇
武器工业   42篇
无线电   60408篇
一般工业技术   116829篇
冶金工业   95625篇
原子能技术   14736篇
自动化技术   46051篇
  2021年   5631篇
  2020年   4177篇
  2019年   5411篇
  2018年   9462篇
  2017年   9649篇
  2016年   10097篇
  2015年   6176篇
  2014年   10476篇
  2013年   26687篇
  2012年   16019篇
  2011年   21354篇
  2010年   17226篇
  2009年   19098篇
  2008年   19240篇
  2007年   18966篇
  2006年   16367篇
  2005年   14794篇
  2004年   14053篇
  2003年   13716篇
  2002年   13291篇
  2001年   12883篇
  2000年   12352篇
  1999年   12022篇
  1998年   27664篇
  1997年   20045篇
  1996年   15629篇
  1995年   12008篇
  1994年   10755篇
  1993年   10509篇
  1992年   8236篇
  1991年   8020篇
  1990年   7943篇
  1989年   7675篇
  1988年   7389篇
  1987年   6658篇
  1986年   6458篇
  1985年   7330篇
  1984年   6643篇
  1983年   6360篇
  1982年   5716篇
  1981年   5847篇
  1980年   5587篇
  1979年   5690篇
  1978年   5635篇
  1977年   6149篇
  1976年   7656篇
  1975年   5071篇
  1974年   4868篇
  1973年   4943篇
  1972年   4257篇
排序方式: 共有10000条查询结果,搜索用时 218 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