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   661419篇
  免费   7808篇
  国内免费   2533篇
电工技术   12196篇
综合类   870篇
化学工业   95901篇
金属工艺   29487篇
机械仪表   22724篇
建筑科学   14521篇
矿业工程   3807篇
能源动力   17060篇
轻工业   46607篇
水利工程   7265篇
石油天然气   12929篇
武器工业   56篇
无线电   77975篇
一般工业技术   136027篇
冶金工业   119107篇
原子能技术   14966篇
自动化技术   60262篇
  2021年   5347篇
  2020年   4069篇
  2019年   5215篇
  2018年   14281篇
  2017年   14574篇
  2016年   12648篇
  2015年   6438篇
  2014年   10238篇
  2013年   28830篇
  2012年   18021篇
  2011年   27643篇
  2010年   22919篇
  2009年   24461篇
  2008年   24975篇
  2007年   26129篇
  2006年   18081篇
  2005年   18684篇
  2004年   17078篇
  2003年   16643篇
  2002年   15314篇
  2001年   14819篇
  2000年   14011篇
  1999年   14637篇
  1998年   37022篇
  1997年   25813篇
  1996年   19825篇
  1995年   14944篇
  1994年   13095篇
  1993年   13214篇
  1992年   9460篇
  1991年   8957篇
  1990年   8799篇
  1989年   8499篇
  1988年   8000篇
  1987年   7065篇
  1986年   7011篇
  1985年   7789篇
  1984年   7139篇
  1983年   6529篇
  1982年   6059篇
  1981年   6159篇
  1980年   5899篇
  1979年   5592篇
  1978年   5594篇
  1977年   6334篇
  1976年   8299篇
  1975年   4753篇
  1974年   4566篇
  1973年   4672篇
  1972年   3921篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Journal of Communications Technology and Electronics - Abstract—The two-dimensional diffraction problem of a plane polarized TM-wave on two identical solid silver nanocylinders is considered....  相似文献   
72.
Wireless Personal Communications - The rapid development of Information and Communication Technology and the growing number of devices connected to the Internet make the Internet of Things (IoT) as...  相似文献   
73.
Metallurgical and Materials Transactions B - The process of obtaining titanium tetrachloride (TiCl4) from the quartz-leucoxene concentrate (QLC) from the Yaregskoe oil-titanium field was studied....  相似文献   
74.
The use of field robots can greatly decrease the amount of time, effort, and associated risk compared to if human workers were to carryout certain tasks such as disaster response. However, transportability and reliability remain two main issues for most current robot systems. To address the issue of transportability, we have developed a lightweight modularizable platform named AeroArm. To address the issue of reliability, we utilize a multimodal sensing approach, combining the use of multiple sensors and sensor types, and the use of different detection algorithms, as well as active continuous closed‐loop feedback to accurately estimate the state of the robot with respect to the environment. We used Challenge 2 of the 2017 Mohammed Bin Zayed International Robotics Competition as an example outdoor manipulation task, demonstrating the capabilities of our robot system and approach in achieving reliable performance in the fields, and ranked fifth place internationally in the competition.  相似文献   
75.
76.
77.

Stability constants and formation enthalpies of supramolecular complexes of crown ethers and their cyclic and acyclic analogues are determined on the basis of experimental data obtained by different physicochemical methods in the terms of a general approach developed and implemented in the ChemEqui software package. The established regularities of variation of stability of complexes are discussed as dependent on the ligand structure, nature of the cation, solvent, and anion. The applicability of the suggested method of determining complexation selectivity is shown for multicomponent equilibria in solutions.

  相似文献   
78.
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis.  相似文献   
79.
80.
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product.  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