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   1564882篇
  免费   26435篇
  国内免费   7032篇
电工技术   34620篇
综合类   6457篇
化学工业   274647篇
金属工艺   64995篇
机械仪表   44220篇
建筑科学   47450篇
矿业工程   11557篇
能源动力   50434篇
轻工业   120233篇
水利工程   15744篇
石油天然气   37844篇
武器工业   150篇
无线电   198119篇
一般工业技术   292413篇
冶金工业   193543篇
原子能技术   34239篇
自动化技术   171684篇
  2021年   15765篇
  2020年   12036篇
  2019年   14784篇
  2018年   17250篇
  2017年   16567篇
  2016年   22126篇
  2015年   17616篇
  2014年   28863篇
  2013年   88226篇
  2012年   37184篇
  2011年   50785篇
  2010年   44008篇
  2009年   51922篇
  2008年   46999篇
  2007年   44381篇
  2006年   45933篇
  2005年   40919篇
  2004年   42811篇
  2003年   42552篇
  2002年   41381篇
  2001年   38523篇
  2000年   36737篇
  1999年   36388篇
  1998年   54849篇
  1997年   45170篇
  1996年   39063篇
  1995年   32882篇
  1994年   30513篇
  1993年   30469篇
  1992年   26683篇
  1991年   23775篇
  1990年   24075篇
  1989年   23161篇
  1988年   21655篇
  1987年   19922篇
  1986年   19236篇
  1985年   22547篇
  1984年   22509篇
  1983年   20460篇
  1982年   19444篇
  1981年   19612篇
  1980年   18204篇
  1979年   18621篇
  1978年   17909篇
  1977年   18078篇
  1976年   19713篇
  1975年   16072篇
  1974年   15544篇
  1973年   15660篇
  1972年   13122篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
High Temperature - Experimental findings suggest that a strongly ionized, arc He plasma of atmospheric pressure does not exist in the state of the local thermodynamic equilibrium (LTE) expected for...  相似文献   
182.
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to...  相似文献   
183.
Ji  Chengang  Yang  Chenying  Shen  Weidong  Lee  Kyu-Tae  Zhang  Yueguang  Liu  Xu  Guo  L. Jay 《Nano Research》2019,12(3):543-548

We present a new scheme for visibly-opaque but near-infrared-transmitting filters involving 7 layers based on one-dimensional ternary photonic crystals, with capabilities in reaching nearly 100% transmission efficiency in the near-infrared region. Different decorative reflection colors can be created by adding additional three layers while maintaining the near-infrared transmission performance. In addition, our proposed structural colors show great angular insensitivity up to ±60° for both transverse electric and transverse magnetic polarizations, which are highly desired in various fields. The facile strategy described here involves a simple deposition method for the fabrication, thereby having great potential in diverse applications such as image sensors, anti-counterfeit tag, and optical measurement systems.

  相似文献   
184.
Fedotov  A. A. 《Measurement Techniques》2019,61(12):1238-1243
Measurement Techniques - The article is devoted to the issues of conceptual development of a new generation of electrocardiogram imitators. A mathematical model is proposed for simulating ECG...  相似文献   
185.
186.
Electrochemical impedance spectroscopy (EIS), anodic polarization and scanning electron microscopy techniques were used to investigate the damage mechanism in the transpassive potential region of AISI ...  相似文献   
187.
The separation of iron oxide from banded hematite jasper(BHJ) assaying 47.8% Fe, 25.6% Si O2 and 2.30%Al2O3 using selective magnetic coating was studied. Characterization studies of the low grade ore indicate that besides hematite and goethite,jasper, a microcrystalline form of quartzite, is the major impurity associated with this ore. Beneficiation by conventional magnetic separation technique could yield a magnetic concentrate containing 60.8% Fe with 51% Fe recovery. In order to enhance the recovery of the iron oxide minerals, fine magnetite, colloidal magnetite and oleate colloidal magnetite were used as the coating material. When subjected to magnetic separation, the coated ore produces an iron concentrate containing 60.2% Fe with an enhanced recovery of56%. The AFM studies indicate that the coagulation of hematite particles with the oleate colloidal magnetite facilitates the higher recovery of iron particles from the low grade BHJ iron ore under appropriate conditions.  相似文献   
188.
189.
190.
Potentiometric sensors with plasticized poly(vinyl chloride) membranes based on β-lactam–tetraalkylammonium ion associates sensitive to penicillin antibiotics are proposed. The physicochemical characteristics (solubility product constants and dissociation constants) of active membrane components and the electrode, transport, and selective properties of the membranes of liquidand solid-contact sensors have been studied. The quantitative characteristics of membrane transport (penetrability, ion flux, and transport rate) have been evaluated. The main charge carriers in the membranes and at the membrane/solution interface have been determined from the membrane transport characteristics. The potentiometric sensors are shown to be applicable to the determination of penicillin antibiotics in biological fluids (blood serum and oral fluid) from patients with urinary tract infection.  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