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   292905篇
  免费   5793篇
  国内免费   895篇
电工技术   5135篇
综合类   248篇
化学工业   44741篇
金属工艺   10331篇
机械仪表   8396篇
建筑科学   7599篇
矿业工程   978篇
能源动力   8053篇
轻工业   27354篇
水利工程   2588篇
石油天然气   3388篇
武器工业   21篇
无线电   36128篇
一般工业技术   56918篇
冶金工业   56350篇
原子能技术   5250篇
自动化技术   26115篇
  2022年   1922篇
  2021年   3242篇
  2020年   2431篇
  2019年   2880篇
  2018年   4906篇
  2017年   4880篇
  2016年   5108篇
  2015年   3516篇
  2014年   5511篇
  2013年   14726篇
  2012年   8621篇
  2011年   10883篇
  2010年   8769篇
  2009年   9649篇
  2008年   10048篇
  2007年   9824篇
  2006年   8443篇
  2005年   7419篇
  2004年   7149篇
  2003年   7347篇
  2002年   6749篇
  2001年   7032篇
  2000年   6467篇
  1999年   6903篇
  1998年   18783篇
  1997年   13026篇
  1996年   9827篇
  1995年   7269篇
  1994年   6421篇
  1993年   6443篇
  1992年   4385篇
  1991年   4268篇
  1990年   4063篇
  1989年   3858篇
  1988年   3756篇
  1987年   3203篇
  1986年   3108篇
  1985年   3400篇
  1984年   3123篇
  1983年   2961篇
  1982年   2798篇
  1981年   2720篇
  1980年   2636篇
  1979年   2414篇
  1978年   2225篇
  1977年   2890篇
  1976年   4154篇
  1975年   1856篇
  1974年   1806篇
  1973年   1770篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
Multimedia Tools and Applications - Mammograms are the images used by radiologists to diagnose breast cancer. Breast cancer is one of the most common cancers in women. The early detection of breast...  相似文献   
5.
The effect of microwave roasting parameters (300, 450 and 600 W; 5, 10 and 15 min) on acrylamide content in sorghum grain was determined using High Pressure Liquid Chromatography (HPLC)-photo diode array (PDA) detector coupled with C-18 column. Samples roasted at 300 and 450 W did not possess acrylamide, whereas 600 W (15 min) favoured formation of 2740.19 µg/kg of acrylamide, levels far exceeding the defined European Union (EU) limits. The chronic daily intake (CDI) for acrylamide through consumption of such grain flour was 3.25–9.5-fold higher to Joint FAO/WHO Expert Committee on Food Additives (JECFA) defined high exposure limits. The margin of exposure (MOE) values ranged from 4.3 to 12.76 and from 11.07 to 32.27 for neoplastic and neurological effects, respectively, demonstrating high exposure and serious health concerns associated with dietary intake of this toxicant. This study assesses the risk for the Indian population and highlights the importance of optimising process parameters for food product to minimise such exposure risks.  相似文献   
6.
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   
7.
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.
Water Resources Management - The water evaluation and planning (WEAP) approach and the invasive weed optimization algorithm (IWOA) are herein employed to determine the optimal operating policies in...  相似文献   
10.
Photoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors’ focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in “direct path” light delivery through tissue, and optical waveguides that “clear the path” between external light source and in vivo target. The authors’ intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials.  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