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   430703篇
  免费   5762篇
  国内免费   1914篇
电工技术   7584篇
综合类   629篇
化学工业   63658篇
金属工艺   17777篇
机械仪表   12696篇
建筑科学   10473篇
矿业工程   2290篇
能源动力   11102篇
轻工业   36612篇
水利工程   4498篇
石油天然气   8339篇
武器工业   45篇
无线电   50342篇
一般工业技术   84866篇
冶金工业   80584篇
原子能技术   10786篇
自动化技术   36098篇
  2021年   3369篇
  2019年   3242篇
  2018年   5460篇
  2017年   5540篇
  2016年   5890篇
  2015年   3920篇
  2014年   6775篇
  2013年   19033篇
  2012年   11101篇
  2011年   15330篇
  2010年   12016篇
  2009年   13975篇
  2008年   14207篇
  2007年   14223篇
  2006年   12167篇
  2005年   11349篇
  2004年   11150篇
  2003年   10609篇
  2002年   10310篇
  2001年   10355篇
  2000年   9805篇
  1999年   10229篇
  1998年   25230篇
  1997年   17927篇
  1996年   13818篇
  1995年   10575篇
  1994年   9174篇
  1993年   9168篇
  1992年   6583篇
  1991年   6324篇
  1990年   6109篇
  1989年   6091篇
  1988年   5740篇
  1987年   5143篇
  1986年   5119篇
  1985年   5783篇
  1984年   5303篇
  1983年   4915篇
  1982年   4588篇
  1981年   4707篇
  1980年   4572篇
  1979年   4356篇
  1978年   4339篇
  1977年   4946篇
  1976年   6524篇
  1975年   3729篇
  1974年   3683篇
  1973年   3759篇
  1972年   3169篇
  1971年   2849篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
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   
2.
3.
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   
4.
Fan  Deng-Ping  Huang  Ziling  Zheng  Peng  Liu  Hong  Qin  Xuebin  Van Gool  Luc 《国际自动化与计算杂志》2022,19(4):257-287
Machine Intelligence Research - This paper aims to conduct a comprehensive study on facial-sketch synthesis (FSS). However, due to the high cost of obtaining hand-drawn sketch datasets, there is a...  相似文献   
5.
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell.  相似文献   
6.
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   
7.

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   
8.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
9.
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   
10.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  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