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   697093篇
  免费   9014篇
  国内免费   3187篇
电工技术   12950篇
技术理论   5篇
综合类   1792篇
化学工业   105570篇
金属工艺   34130篇
机械仪表   23649篇
建筑科学   15964篇
矿业工程   5916篇
能源动力   14891篇
轻工业   50746篇
水利工程   8911篇
石油天然气   19141篇
武器工业   309篇
无线电   72559篇
一般工业技术   148010篇
冶金工业   114477篇
原子能技术   18754篇
自动化技术   61520篇
  2021年   6165篇
  2019年   5668篇
  2018年   14366篇
  2017年   14603篇
  2016年   13570篇
  2015年   7297篇
  2014年   11711篇
  2013年   28682篇
  2012年   19687篇
  2011年   28438篇
  2010年   23489篇
  2009年   24611篇
  2008年   25911篇
  2007年   26835篇
  2006年   19184篇
  2005年   18722篇
  2004年   17316篇
  2003年   16730篇
  2002年   15910篇
  2001年   15354篇
  2000年   14646篇
  1999年   14514篇
  1998年   31688篇
  1997年   23275篇
  1996年   17946篇
  1995年   13933篇
  1994年   12637篇
  1993年   12647篇
  1992年   9778篇
  1991年   9507篇
  1990年   9437篇
  1989年   9343篇
  1988年   8786篇
  1987年   7987篇
  1986年   7888篇
  1985年   8724篇
  1984年   8271篇
  1983年   7806篇
  1982年   7101篇
  1981年   7402篇
  1980年   7134篇
  1979年   7219篇
  1978年   7326篇
  1977年   7799篇
  1976年   9758篇
  1975年   6506篇
  1974年   6402篇
  1973年   6446篇
  1972年   5574篇
  1971年   5051篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Multimedia Tools and Applications - Discovering the relevant web services for specific applications in the dynamically changing business world becomes very critical. Researchers have used many...  相似文献   
62.
Mobile Networks and Applications - 5G/6G communication are first generation high speed wireless communication network which integrates the aerial data, terrestrial data and maritime data via...  相似文献   
63.
64.
Theoretical Foundations of Chemical Engineering - The effect of the electrolyte composition, mass-transfer conditions, pore diameter, interpore distance, and electric parameters on the formation of...  相似文献   
65.
The influence of the microstructure on the corrosion rate of three monolithic SiC samples in FLiNaK salt at 900 °C for 250 h was studied. The SiC samples, labeled as SiC-1, SiC-2, and SiC-3, had corrosion rates of 0.137, 0.020, and 0.043 mg/cm2h, respectively. Compared with grain size and the presence of special grain boundaries (i.e., Σ3), the content of high-angle grain boundaries (HAGBs) appeared to have the strongest influence on the corrosion rate of SiC in FLiNaK salt, since the corrosion rate increased six times as the concentration of high-angle grain boundaries increased from 19 to 32% for SiC-2 and SiC-1, respectively. These results stress the importance of controlling the content of HAGBs during the production process of SiC.  相似文献   
66.
One of the drawbacks of fusible clays is the narrow sintering interval due to a sharp increase in the amount of iron-silicate melt at a temperature of 1000–1100 °C, which hardens in the form of a glass phase upon cooling. This leads to a relatively low mechanical strength of the calcined samples and causes the danger of melting the granular material surface from such clays during the firing process. To increase the strength of samples of fusible clays, the influence of diabase and granitoid rocks was considered. It was found that the strengthening effect of diabase and granitoid rock additives in an amount of 20–50% in a mixture with fusible clay is due to an increase of total content of the crystalline phase (mullite, cristobalite and residual quartz) from 18–20% in clays without additives to 22–28 % - in mixtures with diabase and to 28–34% - with granitoid additives) at a temperature of 1050–1100 °C. This increase is due to the activation of synthesis processes of secondary mullite and crystallization from alkali-rich feldspar melt of amorphous silica, released from the structure of clay minerals. The established influence of the igneous rocks used made it possible to develop compositions and propose process flow sheet for producing aluminosilicate proppants based on fusible clays. The use of granitoid and diabase rocks in an amount of 20–70% with fusible clays produces lightweight aluminosilicate proppants with bulk density of 1.40–1.46 g/cm3 at temperature range of 1050–1100 °C, which can endure destructive pressures up to 34.5–52 MPa.  相似文献   
67.
Theoretical Foundations of Chemical Engineering - The corona onset voltage is an important operating parameter in the electrostatic precipitation of nanoparticulate, however, its experimental...  相似文献   
68.
Multimedia Tools and Applications - Gastrointestinal stromal tumor is one of the critical tumors that doctors do not suggest to get frequent endoscopy, so there is a need for a diagnosis system...  相似文献   
69.
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   
70.
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   
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