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   656423篇
  免费   9120篇
  国内免费   2548篇
电工技术   11418篇
综合类   940篇
化学工业   99559篇
金属工艺   24676篇
机械仪表   19712篇
建筑科学   16170篇
矿业工程   3170篇
能源动力   16670篇
轻工业   62029篇
水利工程   6537篇
石油天然气   10553篇
武器工业   79篇
无线电   76578篇
一般工业技术   125462篇
冶金工业   123791篇
原子能技术   14003篇
自动化技术   56744篇
  2021年   5159篇
  2019年   4921篇
  2018年   8205篇
  2017年   8246篇
  2016年   8922篇
  2015年   5890篇
  2014年   10015篇
  2013年   29500篇
  2012年   16695篇
  2011年   23326篇
  2010年   18237篇
  2009年   20646篇
  2008年   21535篇
  2007年   21656篇
  2006年   19345篇
  2005年   17522篇
  2004年   16964篇
  2003年   16553篇
  2002年   16015篇
  2001年   16087篇
  2000年   15155篇
  1999年   15802篇
  1998年   38085篇
  1997年   26964篇
  1996年   20686篇
  1995年   15883篇
  1994年   14052篇
  1993年   13893篇
  1992年   10266篇
  1991年   9658篇
  1990年   9665篇
  1989年   9369篇
  1988年   8921篇
  1987年   7757篇
  1986年   7708篇
  1985年   8950篇
  1984年   8245篇
  1983年   7570篇
  1982年   7076篇
  1981年   7237篇
  1980年   6948篇
  1979年   6582篇
  1978年   6495篇
  1977年   7309篇
  1976年   9456篇
  1975年   5591篇
  1974年   5329篇
  1973年   5521篇
  1972年   4540篇
  1971年   4108篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Journal of Materials Science -  相似文献   
2.
3.
Wireless Personal Communications - Chronic kidney disease (CKD) is a gradual loss of kidney function over the period of time and it is irrevocable once functionality reaches the critical state....  相似文献   
4.
Xiao  Zhu  Chen  Yanxun  Jiang  Hongbo  Hu  Zhenzhen  Lui  John C. S.  Min  Geyong  Dustdar  Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of...  相似文献   
5.
6.
Food Science and Biotechnology - A rich source of nutrients, figs have a number of clinically validated benefits. This study aimed to evaluate the in vitro simulated gastrointestinal digestion, and...  相似文献   
7.
Multimedia Tools and Applications - In this work, a new fuzzy logic-based algorithm is proposed for the enhancement of low light color images. A generalization of a fuzzy set known as an...  相似文献   
8.

We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.

  相似文献   
9.
This study presents the development and characterization of PVDF-conjugated polymer nanofiber-based systems. Five different conducting polymers (CPs) were synthesized successfully and used to create the nanofiber systems. The CPs used are polyaniline (PANI), polypyrrole (PPY), polyindole (PIN), polyanthranilic acid (PANA), and polycarbazole (PCZ). Nanofiber systems were produced utilizing the Forcespinning® technique. The nanofiber systems were developed by mechanical stretching. No electrical field or post-process poling was used in the nanofiber systems. The morphology, structure, electrochemical and piezoelectric performance was characterized. All of the nanofiber PVDF/CP systems displayed higher piezoelectric performance than the fine fiber PVDF systems. The PVDF/PPY nanofiber system displays the highest piezoelectric performance of 15.56 V. The piezoelectric performance of the PVDF/CP nanofiber systems favors potential for an attractive source of energy where highly flexible membranes could be used in power actuators, sensors and portable, and wireless devices to mention some.  相似文献   
10.
To investigate the evolution of the structural and enhanced magnetic properties of GdMnO3 systems induced by the substitution of Mn with Cr, polycrystalline GdMn1-xCrxO3 samples were synthesized via solid-state reactions. XRD characterization shows that all GdMn1-xCrxO3 compounds with single-phase structures crystallize well and that Cr3+ ions entering the lattice sites of GdMnO3 induce structural distortion. SEM results indicate that the grain size of the synthesized samples (a few microns) decreases as the Cr substitution concentration increases. Positron annihilation lifetime spectroscopy reveals that vacancy-type defects occur in GdMn1-xCrxO3 ceramics and that the vacancy size and concentration clearly change with the Cr content. The temperature and field dependence of the magnetization curves show that Cr substitution significantly influences the magnetic ordering of the gadolinium sublattice, improving the weak ferromagnetic transition temperature and magnetization of GdMn1-xCrxO3. The enhanced magnetization of GdMn1-xCrxO3 is closely related to the vacancy defect concentration.  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