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   610090篇
  免费   7551篇
  国内免费   3025篇
电工技术   11663篇
综合类   923篇
化学工业   83130篇
金属工艺   28689篇
机械仪表   21036篇
建筑科学   14035篇
矿业工程   2747篇
能源动力   14755篇
轻工业   47151篇
水利工程   5892篇
石油天然气   8627篇
武器工业   60篇
无线电   74809篇
一般工业技术   122923篇
冶金工业   117029篇
原子能技术   12352篇
自动化技术   54845篇
  2021年   3920篇
  2019年   3749篇
  2018年   13344篇
  2017年   13800篇
  2016年   10614篇
  2015年   5174篇
  2014年   8019篇
  2013年   24515篇
  2012年   15342篇
  2011年   25496篇
  2010年   21458篇
  2009年   22556篇
  2008年   23108篇
  2007年   24990篇
  2006年   16015篇
  2005年   17763篇
  2004年   15940篇
  2003年   15383篇
  2002年   14217篇
  2001年   14034篇
  2000年   13124篇
  1999年   14241篇
  1998年   36663篇
  1997年   25586篇
  1996年   19117篇
  1995年   14584篇
  1994年   12839篇
  1993年   12724篇
  1992年   8882篇
  1991年   8646篇
  1990年   8150篇
  1989年   7864篇
  1988年   7458篇
  1987年   6415篇
  1986年   6433篇
  1985年   7263篇
  1984年   6593篇
  1983年   6031篇
  1982年   5682篇
  1981年   5714篇
  1980年   5462篇
  1979年   5092篇
  1978年   5066篇
  1977年   6023篇
  1976年   8572篇
  1975年   4273篇
  1974年   4137篇
  1973年   4144篇
  1972年   3456篇
  1971年   3024篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Wireless Personal Communications - The orthogonal frequency division multiplexing (OFDM) is the most encouraging multi-carrier modulation system chosen for the high data rates but the objective is...  相似文献   
52.
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   
53.
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   
54.
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   
55.
56.
57.
58.

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   
59.
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   
60.
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